Plate ECCCXV

Plate ECCCXV. Mr Stephens's apparatus was as follows: Fig. 1. A is the bed of the kiln, which flies off about four feet by

two from the grate, more or less according to the size; C is the ash-hole, 2$\backslash frac\{1\}\{2\}$ or 3 feet deep. Fig. 2. B represents quadrangular bars of iron, with their opposite angles placed upwards and downwards, not above an inch asunder. Fig. 3. A, B, and C, are three keepers five feet deep, and of any width from four to eight feet square, of the best white pine or cypress plank, with square joints and strong oak frames, placed each over a receiver, with a cock to let off the lye, and a vent just beneath the surface of the grating. E represents three receivers, standing each under, and projecting out, from its keeper. They must be made of the best stuff, carefully put together, and laid in tough clay well rammed within the ground, their tops being level with the surface: they need not be so large as the keepers by six, eight, or twelve inches. Fig. 4. E represents a false bottom or lattice of boards, eight inches deep and five square, with a hole in the under edge of every partition for the lye to pass into the keeper. Fig. 5. A is the vessel over the furnace in which the lye and ashes are mixed; B is a hole or funnel a few inches from the back of the furnace, with an iron socket to let the pipe through the hinder part of the arch, to reach down within two inches of the floor of the furnace. C is a cast iron cauldron for boiling the lye to dryness when pearl-ash is made. D is a vessel whence the liquor is let into the cauldron as it evaporates. The mortar for building the furnace should be made of loam; the arch should be 18 inches thick, and the floor should be laid with tiles on a layer of sand an inch thick, with neat joints.

Mr Stephens's process, both with and without the kiln, was as follows. Cut timber, felled at any season, into lengths of about eight feet; lay from three to ten of them lengthwise in a heap upon dry ground, and fill the vacancies between with smaller wood: the sooner it is burnt after felling, the better. Set fire to it by laying embers on the bottom logs at each end; and for burning the brush and lappings, with other smaller woods, lay them lengthwise on the ground, top to top, lapping over a little, with the butt ends outwards, and as close as a faggot; laying the larger woods on top till the heap is full four feet high; the length of the brush set against each other making the breadth of the heap. As to the choice of the timber, old hollow trees, if not dead, are best: pine, cypress, and cedar, are to be totally rejected.

As soon as the pile is burnt down, rake such ashes as lie round the outside a little in towards the middle; add no fresh fuel, nor throw on any brands. Let the ashes lie without stirring till you can just bear your hand in them; then carry them to a houfe, or under a shed, on a plank floor raised a little from the earth and well jointed;

(A) According to Sir Peter Warren, the best woods for making Russia potash are, oak, ash, poplar, hiccory, elm, hazle, and beech. They must be cut in November, December, January, and February, split and stacked to dry. After 12 months in warm open weather, it must be burnt on a brick hearth by a slow fire in a kiln, or close place; the ashes must be sifted through two sieves, one finer than the other, and then put up in brick troughs or wooden backs, covered with rain or river water, and must remain well marshed and incorporated five months. Brick furnaces shaped like bakers ovens must be heated with a strong fire of oak or ash, burning night and day; the prepared ashes must be gradually thrown on the fire, when they will run into metal like lead: the fire must not go out till the furnace is nigh filled with potashes. The ashes must then be broken to be taken out, but the larger the pieces the better; they must be preserved from the air in tight casks, the large pieces by themselves, and the dust by itself.

Potash. jointed; there wet them till brought nearly to the consistence of mortar in the first mixture of lime and sand, and ram them in a heap, in which they must lie full 20 days, or some months if you please; observing to be more sparing of water in winter, and ramming them closer, and sometimes wetting the top that it may never grow quite dry.

And with it. Wood may also be burnt in a kiln, as fig. 1 and 2; and then it must be cut into such lengths as may be most convenient for carriage, and best suit the size of the kiln. Plate CCCCXV. The mouth of the ash-hole must be close stopped by daubing the joints of the lid with loam, or throwing a bank of sand or earth against it: keep the bed of the kiln filled with wood up to the surface, but not above it, and let it burn incessantly till the ashes rise within six or eight inches of the grate. Draw them out whilst red-hot, and in that state sprinkle them with lye, from four to six caracts weight; weigh a small vial which holds about four ounces very exactly; then fill it with water and weigh that also: divide the weight of water into equal parts till you come to $\backslash frac\{1\}\{2\}$ of the whole, which is called a caract, $\backslash frac\{1\}\{2\}$ two caracts, &c. until you have a weight equal to $\backslash frac\{1\}\{2\}$ of the whole water, which is called 32 caracts: all which small weights, together with one equal to the phial filled with water, are to be kept for weighing the lye in the said phial till they are made damp; then ram them as before in a heap, but separate from the ashes made as above. N. B. By kiln-burning a stronger lye may be more certainly procured than by the other way, where rain may chance to fall on the ashes before they can be removed.

The ashes thus prepared are to be put in vats or sleepers fig. 3, with a false latticed bottom as fig. 4; first putting coarse wheat or rye straw about a foot thick on the lattice or grating; on which put ashes to within four or five inches of the top, ramming them all the way up, especially at the sides, with a small light rammer, as tight as you can, without bursting the vat. Form on the top of the sleeper a hollow basin in the ashes four or five inches deep, leaving the ashes four or five inches thick on the sides, by raising a small bank round the sides, so that the liquor may not overflow the edges of the ashes at top: keep this basin constantly filled with soft water in the sleeper A, until the ashes will imbibe no more, which will be in 24 hours or more, according as it is rammed; then turn the cock, and let off what shall be soaked through into the receiver or lower chamber of the sleeper, and no more; for if the several runnings are not kept separate, the lye will not be brought to its due strength. Follow that sleeper with fresh water on the same ashes for several other runnings, which will each come off in a few days, till the liquor has neither smell nor taste; then heave out the ashes, and charge the sleeper as fresh.

Upon drawing off the first running from the sleeper A, fig. 3, fill the sleeper B with ashes as before, and put into its hollow at the top the lye so first run off, and the smaller or half lyes also, till full, and draw off as directed for the sleeper A: if this weighs 18 caracts or more, pump it into the cistern F as fit for use; if it be short of that, pass it off as half lye to the sleeper C, and through fresh ashes till strong enough. With kiln-ashes only, from water passing through the first sleeper, it will be strong enough for the cistern, if the ashes are well prepared. If your water be hard, let it stand two

or three days exposed to the air and sun in a shallow back, and it will be soft. When you use kiln-ashes with others, lay them at bottom. Potash.

The lye must be conveyed from the cistern F, as it is wanted to the vessel A fig. 5; where with every gallon of proof lye mix three ounces of fine, light, wood ashes; and to the lye that is $\backslash frac\{1\}\{2\}$ over-proof put six ounces of ashes; and if $\backslash frac\{2\}\{3\}$ over-proof put 12 ounces, increasing or lessening according to the strength of the lye.

For evaporating the lye and melting the salt, heat a furnace till you bring it very near a white heat, of which the side-doors being red-hot is a mark. This will take 48 hours or more, if the furnace be quite cold; when thorough hot, a little fuel keeps it so. Then, through the cock of the vessel A, pass the mixture by the funnel B into the furnace, not so as to reach much beyond the middle of the floor, before it changes from dark to bright red, letting the heat prevail towards front or back as you see necessary. When the mass begins to gather about the flames or in heaps, run in no more till the furnace is cleared by driving the fire backward. You must have two funnels, one soon choking: in an hour or less will issue out a red-hot stream of melted salt, which is potash, to be broke to pieces as soon as cold, and packed in tight close casks, being in no respect inferior to the best foreign ash-whatever.

The best potash is made from barilla, and comes from Spanish Spain. The plants from which it is procured are found potash the in great plenty about Carthigena, where they are indigenous, and may be collected in a swamp called Almogar east of that place; the Sayana barilla is the best. They are found, besides all along that coast, on the borders of the Mediterranean for 60 leagues in length and 8 in breadth. About 150,000 quintals of it are annually exported from Spain. It produces a revenue of 25,500 l. a year; each quintal paying a duty of 17 reals: yet Don Bernardo de Ulloa, A. D. 1740, says it was farmed at L. 1822, 4s. 3d. M. Macdonnell has brought the manufacture of potash to its present perfection in Spain; but its exportation is materially injured by the heavy tax on it. See Townshend's Travels, vol. iii. p. 131. See also BARILLA, KEEF, and FOCUS.

In the 70th volume of the Philosophical Transactions Dr Percival's account of procuring this salt from the putrid water which runs from dunghills. The making process is very easy, consisting only in simple evaporation of the fluid, and calcining the impure salt till most of the foulness is burnt out. From 24 wine-pipes full of this muck-water were obtained 9 cwt. 1 q. 12 lb of saleable potash, valued at 42 s. per cwt; the expence of manufacturing them being only valued at 4 l. 9 s.

The potash thus made is of a greyish white appearance; deliquesces a little in moist air; but if kept in a dry room, near the fire, acquires a powdery surface. It is hard and of a spongy texture when broken, with many small crystals in its substance. The colour of its internal parts is dusky and variegated. To the taste it is acrid, saline, and sulphureous. It emits no smell of volatile alkali, either in a solid form, dissolved, or when added to lime-water; neither does it communicate the sapphire-colour to a solution of blue vitriol. Silver is quickly tinged black by it; a proof that it contains much phlogiston. Ten grains of this potash required 11 drops of the weak spirit of vitriol to separate it. The

Potash. The like quantity of salt of tartar required 24 drops: a strong effervescence occurred in both mixtures; and a sulphureous vapour exhaled from the former. A tea spoonful of the syrup of violets diluted with an ounce of water was changed into a bright green colour by five grains of the salt of tartar; but ten grains of this potash were necessary to produce the same hue in a similar mixture. Half an ounce of the salt dissolved entirely in half a pint of hot water; but when the liquor was cold, a large purple sediment subsided to the bottom; and it was found that this sediment amounted to about two-thirds of the whole quantity of ashes used.

Dr Percival, the author of this paper, concludes with observing, that this potash is a true fixed vegetable alkali, produced by putrefaction; that the quantity of alkali contained in it may be estimated at one-third of its weight, whereas the white Muscovy ashes are said to yield only one-eighth part; that no quicklime appears to be contained in this potash, for a solution of it poured from its sediment remained clear though long exposed to the air: that it would be worth trying, whether the large purple sediment, which subsides when this potash is lixiviated, might not be applied to the manufacture of Prussian blue, or used in the manner recommended by Macquer for dyeing wool and silks; and that this manufacture will furnish the farmer for top-dressing for his garden and land, of great fertilizing powers. See Phil. Trans. Vol. LXX. p. 345.

There are the processes most essentially different from one another which have appeared concerning the manufacture of this useful salt. Some indeed have attempted to compose it on the supposition that alkali consisted of an earth combined in a peculiar manner with a certain acid. But the little success of all these attempts show that they have been built on a false principle. The only method of producing alkaline salts originally is from the ashes of vegetables; and the vegetable substances which yield the largest quantity of them are tartar and marine plants. From the former the purest and strongest vegetable alkali is obtained, and from the latter the mineral alkali. From other vegetables, as fern, broom, bean-stalks, &c. an alkaline salt is produced, but so impure, and in such small quantity, that no manufacture of it can be established in this country with any reasonable expectations of profit.

Dr Watson (the present bishop of Landaff) suggests, that the investigation of a method of extracting its alkaline part from rock salt would be a most serviceable discovery. We have inexhaustible mines of rock salt in this country, which (he observes) the proprietors can afford at ten shillings a ton. A ton of rock-salt contains about half a ton of mineral alkali, which is for most purposes far preferable to potash. To those who have leisure to attempt such a discovery, he gives the following hint: whether the alkaline part of rock-salt may not be obtained by calcining it in conjunction with charcoal in open fires? His reason for this conjecture is founded upon the following experiment: upon burning sea-wreck to a black coal and stopping the process at that point, he has obtained great plenty of common salt, but no mineral alkali from the black ashes; though we are certain, that when the black ashes are thoroughly calcined, or reduced to white ashes, mineral alkali may be obtained from them. This makes it probable, that the common salt contained in the black ashes o

sea-wreck is decomposed, and changed into a mineral alkali, during the burning of the black ashes. There are reasons to suppose, that the cinder of pit-coal would answer the purpose better than charcoal. Chem. Eff. vol. I. p. 136, &c.

The potashes of different countries vary much in Dr Home's quality; and the experiments of Dr Home, in his treatise on Bleaching, seem to set forth their different properties in the clearest point of view. The different kinds tried by him were;

1. Blue pearl-ashes. These appear to be a pure alkaline salt, mixed with a small quantity of vitriolated tartar and earth. Half a pound of this, filtered and evaporated, yielded 5½ ounces of pure salt.—Here, however, we must observe, that though the quantity was so far diminished by this operation, yet we are not to imagine that the whole of this diminution was owing to impurities; for all salts are destroyed in some measure by solution in water and exiccation.

2. White pearl-ashes are nearly of the same quality with the former; half a pound of them giving five ounces and seven drams of pure salt, with some vitriolated tartar and earth.

3. Russia or Muscovy ashes have very much the appearance of flaked lime, and are, like it, friable betwixt the fingers. They adhere to the tongue; and their alkaline taste soon goes away, leaving in the mouth a strong taste of lime. Some small bits of charcoal are observable in their composition, and they never turn moist in the air. Half a pound of the salt lixiviated with water and evaporated, gave only 10 drams 15 grains of very caustic salt. These consist therefore of a small quantity of alkaline salt united with a large quantity of lime.

4. Cashub-ashes are of the colour of iron stone, and extremely hard, with many shining particles of charcoal in them. They have a saline taste, with a considerable degree of pungency; feel gritty in the mouth when broke in pieces by the teeth; and will dissolve in water. To extract the pure salt, half a pound of the ashes were boiled in a pint of water; then that water poured off, and half a pint put on the ashes again; and so on, till the ashes tasted no more salt. This boiling took 24 hours, and the last water that came off had a strong taste of sulphur, and was blackish. A piece of silver put in the decoction was in a few minutes turned almost black; but though the decoction was evaporated considerably, it did not turn silver black more speedily than before. The whole, when totally evaporated, yielded only 10 drams of a brown salt having a strong caustic alkaline taste. Some Cashub-ashes powdered, and often washed in water so that the salts were all carried off, were infused in water. After standing some time, there was a weak lime-water, with something of a saline taste, but no pellicle. Some of this residuum was put into a reverberatory furnace for two hours; after which it afforded good lime-water. Cashub-ashes then appear to contain an earth half vitrified, some lime, alkaline salts, and a quantity of sulphur.

5. Marcesc ashes are of a paler colour than the former, with some small pieces of charcoal in their composition. They have a strong saline taste; and so great pungency, that they cannot be held long in the mouth. Half a pound dissolved in water, filtered and evaporated, yielded 11 drams one scruple and two grains of alkaline

Potash. alkaline residuum. The decoction blackened silver, but not so strongly as the former; and by evaporation it quickly lost that quality.

11
On manufacturing them in this country.

Our author next proceeds to consider the probability of manufacturing these ashes in this country. On which subject he has the following observations.—“The blue and white pearl-ashes we have discovered to be pure alkaline salts, without any considerable mixture of heterogeneous bodies. Their purity shows the lixivie to have been strained through some close substance, such as linen or flannel. The blue ashes show by their colour that they have sustained the most fire. But both of them are so much alike, that the one may be substituted for the other; and therefore we shall consider them in one view.

“Every one knows that alkaline salts, such as these, are got from all plants except the alkaline, and from all trees except the most resinous, which afford them in very small quantity. These plants or trees, when found, are pulled or felled in the spring, dried, and burnt to ashes. By the infusion of warm water the salts are dissolved, and, by straining, separated from the earth along with the water. This saline liquor, which is called a lixivie, is evaporated over a fire; and what remains is an alkaline salt of the same kind with the pearl-ashes.

“I was informed by a skillful bleacher in Ireland, that he practised a more expeditious way of extracting the salts. He bought the ashes of different vegetables from the commonalty for 9s. a bushel. From these a very strong lye was made, into which dry straw was dipped until it sucked up all the lye. This straw was afterwards dried and burnt, and gave him salts which he showed me, almost as good and pure as the pearl-ashes. This method I have several times tried; but could never burn the straw to white ashes, the salts diminishing the inflammability of the straw. It is a very expeditious method if it can be practised. But I can see no occasion for bringing the lye into a solid form, as the salts must again be dissolved in water before they can be used. The strength of the lye can easily be determined by the hydrostatical balance.

“Though I make no question, that the quantity of salt, in plants of the same species, will vary in different soils and climates; yet it would be of advantage to have the proportion ascertained in general. Some trials of this kind I have made.

“Two pounds of fern which had been pulled August 16. were dried, and burnt to white ashes. These weighed 7 dr. and tasted very salt. When lixiviated, strained, and evaporated, they gave me 49 gr. of salt, about the eighth part of the ashes. If the fern had been pulled in April, it would have afforded more salt. Why then should we not prepare salts from this vegetable? There is more of it growing on our hills than would serve all our bleachfields. The Irish make great use of it.

“From 11 oz. of tobacco-ashes I had 1 oz. of salt. Two ounces of peat-ashes afforded half a drachm of

salt. Nettles, I am informed, afford much salt. Furz and broom, natives of this country, are very fit for this purpose.

“But the kelp, as it grows in such plenty along our shore, and contains more salt than any other vegetable I know, would be the most proper, were it not for a mixture of some substance that renders it unfit for bleaching, at least of fine cloths, after they have obtained a tolerable degree of whiteness. It is observed by bleachers, that, in these circumstances, it leaves a great yellowness in the linen. As these ashes are much used in Ireland, and as it is not uncommon to bleach coarse cloths with them in Scotland, a disquisition into their nature, and some attempts to purify them, may not be improper. “There are no ashes sold so cheap as these; for the best gives but 2 l. the 2000 weight (B). They may, therefore, allow of more labour to be expended on them, and come cheaper at long-run than the foreign salts.

“I dried some sea-ware, and burnt it, though I found that last operation very difficult. When I had kept it fused in the fire for two hours, it weighed 3½ oz. I poured on the ashes an English pint and a half of cold water, that I might have as little of the sulphur as possible. This lye, after it had stood for some hours, was poured off clear, and had but a slight tendency to a green colour. I made a second infusion with milk-warm water, and poured it off from the sediment. This had a darker colour than the former; was kept separated from it, and evaporated by itself. There was a third infusion made; but having no salt taste, it was thrown away. The second infusion seemed to contain more sulphur than the first; and a piece of white linen kept in it half an hour, while it was boiling, was tinged yellow, and could not be washed white again. The earthy part remaining, weighed, when well dried, 1 oz. 2 dr. The saline decoction evaporated by degrees, and set at different times in a cellar to crystallize, afforded me 5 dr. 46 gr. The liquor, when entirely evaporated, left 4½ dr. of a yellow salt, which appeared to be a strong alkaline. The salts which crystallized seemed to be mostly sea-salt, with a considerable quantity of sulphur, and some alkaline salt. There appeared no signs of the bitter in these salts, as their solution did not turn turbid with the oil of tartar. Nor is any of the bitter to be expected in kelp ashes, although it probably is to be found in the recent vegetable; because the alkaline salts formed by the fire must have changed it into a neutral. The lye made warm with water, being evaporated, left 4 dr. of a black bitter salt, which, from its quantity of sulphur, appeared unfit for bleaching. These ashes, then, seem to be a composition of somewhat less than the fourth of sulphur, the same quantity of sea-salt, about a fourth of alkaline salt, and somewhat more than a fourth of earth. The alkaline salt contained in kelp ashes amounts to one penny a pound. This cheapness makes it worth our pains to bestow some labour on them.

“If the bad effects in bleaching with kelp-ashes arise

Potash. from the sea-salt, as some of the most knowing bleachers think, they can be freed from it in an easy manner. Let a lixive of kelp-ashes be made with cold water, for that does not extract so much of the sulphur; it must stand but for a short time, for these salts dissolve easily; decant it, and evaporate the lye. As the boiling continues, the sea-salt will crystallize. When that is all separated, the remaining lye will contain alkaline salt with some sulphur. This operation every master of a bleachfield may learn and oversee, without taking up much of his time. A similar process is carried on by common servants in the alum-works, who have by practice learned it from others.

"I had some hopes that the sulphur might be carried off by long roasting, such as these salts undergo before they are fused in order to be turned into glass; because I had observed, that the longer time they were kept in the fire, the freer were they from this sulphureous part.

"I ordered a quantity of kelp-ashes to be kept in the furnace of a glasshouse, where the heat was just below the vitrifying point, for 24 hours. During this time they had lost almost four-fifths of their weight. They were now much freer from their sulphur, and were of a light colour; but much of the alkaline salt had been driven off with the oils. If a lye is much impregnated with this sulphureous matter, it appears to be carried off in a great measure by long boiling.

"We come now to explain the method of manufacturing the white Muscovy ashes. We have shown, by undoubted experiments, that the greatest part of these ashes consists of lime; and yet we have several acts of parliament which forbid the use of that material under severe penalties. The parliament were in the right to discharge its use, upon the disadvantageous reports which were made to them. We shall immediately see how dangerous a material it is when used improperly, or without the mixture of alkaline salts, which render it safe, and more soluble in water. But I will venture to say, that experiment will not support the prejudice entertained with regard to it, if carried any further.

"Since bleaching, then, cannot be carried on without it (for those ashes which contain it are quite necessary in that operation), and since we import them from foreign countries, let these prejudices against it cease, and let us only consider how we may render our own lime as safe as the foreign. If we can do that, the wisdom of the legislature will be as ready to abrogate these acts as they were to make them.

"By my experiments on the white Muscovy ashes, I got about the eighth part of alkaline salts from them. This made me expect, that, by mixing in the same proportion quicklime and alkaline salts, I should be able to produce Muscovy ashes.

"To an ounce of quicklime and a drachm of white pearl ashes, I added about a gill of water, and boiled them together till the water was all evaporated. The taste of this substance was little different from lime. To recover the salts again from the lime, I dissolved it in water, strained off the liquor, and evaporated it. Instead of the drachm of salts, I had but 2 gr. of a substance which was more earthy than saline.

"To 3 dr. of quicklime, and as much potashes, I added a mutchkin of water, and kept it boiling for two

hours till it was evaporated. I dissolved it again in water, which being filtered and evaporated, gave me 1$\backslash frac\{1\}\{2\}$ dr. of a caustic salt, that liquefied in the air when it had been but four minutes from the fire. It appears, then, that the alkaline salts are destroyed by lime, and that a great part of them can never be again recovered. From the remaining lime, after the salts were extracted, I got strong lime-water, but without a pellicle. This shows, that a quantity of alkaline salts, equal to the lime, boiled with it for two hours, are not able to fix all the soluble part of the lime.

"From these experiments we may draw some corollaries with regard to the present subject. 1$\backslash frac\{1\}\{2\}$, That evaporating the water from the lime and salts by boiling, is a most unfrugal way of preparing these white ashes. 2$\backslash frac\{1\}\{2\}$, That these ashes ought to be kept close shut up in casks; for if exposed to the open air, though in a room, the alternate moisture and drought must fix their most useful parts. This I have found to be fact: for the salts that I made became less pungent by keeping; and I have observed, that the surface of the Muscovy ashes lost all pungency by being exposed to the air, while their internal parts still retained it. 3$\backslash frac\{1\}\{2\}$, That all boiling is prejudicial to these Muscovy ashes, as it fixes, and that quickly, their most subtile and probably their most serviceable parts.

"Let us now proceed to another method of making these white ashes. I imagined, that if the salts were dissolved in water, and the quicklime slacked with that, the mass would soon dry without the assistance of fire. In this way I added equal parts of both; but the composition was so strong, that it blistered my tongue if it but touched it. When the fourth part was alkaline salt, it blistered my tongue when kept to it a few seconds. I could taste the salts plainly in the composition, when they made but the thirty-second part of the whole.

"I thought, when composed with the eighteenth part of salt, it had, when fresh made, just the taste and look of the Muscovy ashes; nor could any person have distinguished them. This I once imagined was the proportion; but when I found that the saline pungency soon turned weaker by keeping, and that this composition would not afford the same quantity of salts that the Muscovy ashes did, I saw that a much greater quantity of salts was necessary. The proportion appears to be one of salt to four of lime, prepared in this last way. Three drachms of ashes prepared in this way, and kept for a fortnight, gave me but 15 grains of salt; which is but the half of what the Muscovy would have afforded. I find, if the quicklime is first quenched, it does not fix the salts so much; and therefore is better and cheaper. One drachm of potashes dissolved in a little water, and added to 3 drachms of quenched lime, gave me 44 grains of a very caustic salt. I prefer this method as the best.

"The manufacturers of this salt probably pour the lixive upon the lime, as they can know by its specific gravity what quantity of salts is in the water, and so save themselves the expence of procuring the salts in a dry form.

"The manufacture of the Marcoft and Cashub ashes remains yet to be explained. We have discovered that both of them contain sulphur, earth, alkaline salts, and

Potash. lime; and differ in nothing but in the Cashub's having more sulphur than the Marcoft ashes. We shall therefore consider them together.

"Whether these two species of ashes are of any use in bleaching, may be, and has already been, disputed. I find they contain no other principles, the sulphureous part excepted, than the former ashes combined together. Why then should we expect any other effects from the same ingredients in the Marcoft and Cashub ashes, than what we have from either of the pearl and Muscovy ashes mixed together? The sulphureous principle in the former must have very bad effects; as I find by experiment, that it leaves a yellowness on cloth that is very hard to be washed out. It is owing to this sulphureous principle that linen, after it has been washed with soap, and is pretty well advanced in whiteness, is apt to be discoloured by lye which is brought to boil: for, by boiling, the sulphureous part is extracted from these ashes, and the lye becomes of a deep brown colour. Daily practice, then, shows the disadvantage of this sulphureous principle. Besides, as sulphur unites itself quickly and firmly with alkaline salts, it must weaken or altogether destroy a great quantity of these in the Marcoft and Cashub ashes, and so render them of no effect in bleaching. These two reasons seem to me sufficient to exclude them from the bleaching field; especially as, by increasing the other materials, we can attain perhaps more speedily the same end.

"However, as custom has introduced them into general practice, we shall consider how they are to be manufactured. Dr Mitchell has, in a very ingenious and useful paper, contained in the Philosophical Transactions for the year 1748, delivered an account transmitted to him by Dr Linnaeus of the method of making potashes in Sweden. This account was contained in an academical dissertation of one Lundmark upon this subject at Aboe in Sweden. The substance of this account is, 'That birch or alder is burnt by a slow fire to ashes, and made into a paste with water. This paste is plastered over a row of green pine or fir logs. Above that is laid transversely another row of the same; and that likewise is plastered over. In this way they continue building and plastering till the pile be of a considerable height. This pile is set on fire; and whenever the ashes begin to run, it is overturned, and the melted ashes are beat with flexible sticks, so that the ashes incrust the logs of wood, and become as hard as stone.' This, in the Doctor's opinion, is the method of making the potashes that come from Sweden, Russia, and Dantzic; and that there is no other difference betwixt the ashes made in those different countries, but that the Russian, containing more salt, must be made into a paste with a strong lye.

"There would appear, by my experiments, a greater difference than this betwixt the Swedish ashes, if that is the true process, and those I have examined. I had discovered the greatest part of the Muscovy ashes to be lime. I suspected it might enter into the composition of the Marcoft and Cashub; and have accordingly discovered it there. Without the same grounds, none would ever have searched for it. Whence then comes this lime? It must either enter into its composition, or arise from the materials managed according as the process directs.

Potash. "I have tried the birch ashes made into a paste with water. I have tried common charcoal made into a paste with a third part of potashes, and kept them in a strong reverberatory heat for some hours, and yet no such caustic substance appeared. I have kept earth and salts of kelp-ashes fused together for 24 hours in the furnace of a glasshouse, where the heat was just below the degree of vitrification; and yet no remarkable causticity appeared afterwards in the concreted mass. But supposing that there did, will ever this account for the generation of lime? These chemists do not assert that it is a calcareous causticity. The earth of vegetables kept in fusion with their salts, is so far from turning into a quicklime, that the mass takes the opposite course, and becomes glass. Bodies that, by the laws of nature, are vitrifiable, can never, so far as we know, become calcareous. In one or other of these two substances all bodies terminate that are changeable by fire; and vegetables are of the former kind. Here it may be asked, Why then, since they endure such a fire, are they not vitrified? the objection would be just, did they contain nothing else but what was found in vegetables. But if we once allow that lime is one of the materials, the difficulty is easily solved: for lime, we know, in proportion as it is mixed, hinders the vitrification of all bodies. In effect, the earthy part in these ashes is almost vitrified: and I think that I have carried the vitrification yet farther in that part; but I never was able, with the utmost heat of a reverberatory furnace, continued for six hours, to produce any thing like a thorough vitrification in these ashes. The heat of the fire used in the process would seem to be very great; and must, if it were not very difficult, reduce them to glass. The invitrifiable nature of these salts, so far from being an objection, becomes a strong proof of my opinion.

"These salts have a remarkable pungency. This we have already seen is the natural effect of quicklime on salts.

"These salts are found to be the fittest for making soap, and to incorporate soonest and best with oils. Salts, we know, of themselves do not readily unite with oil; but when once mixed with quicklime, they have a greater tendency to union.

"Again, I find that these ashes are more easily fluxed than charcoal made into a paste with the third part salt; which is much more than the ashes contain. Now, it is observed that quicklime increases the fluxing power of alkaline salts; for the common caustic made of quicklime and alkaline salts is sooner fused than the latter alone.

"From these reasons, and the experiments that discover lime in these ashes, I am led to think, that it is not generated by the process, but mixed with the ashes when they are made into a paste. The following experiment is a convincing proof of what I have been endeavouring to make out.

"I boiled some pease-straw in a strong lye of pearl-ashes burnt into a black coal, and made it into a paste with water. Another quantity of straw was boiled in a lye made of one part of quicklime and four parts of pearl salts, the lye being poured off turbid from the lime. This straw was likewise burnt when dry, and made into a paste. These two substances were put in-

Potash. to separate crucibles, and fluxed in a reverberatory furnace. The latter appeared to resemble the Marcoot and Cashub ashes more than the former, which seemed to want their pungency.¹²

Though the only method of preparing the alkaline salt originally is by the combustion of vegetables, yet there are some neutral salts from which if it were possible to expel the acid, we should have it in our power to procure the finest pearl-ashes in vast quantity. These are vitriolated tartar, nitre, but especially sea-salt, on account of the inexhaustible quantities of it to be met with in the waters of the ocean. Unhappily, however, there are some objections to every one of those. The vitriolated tartar, or any other salt in which the vitriolic acid enters, cannot be decomposed without converting the acid into sulphur by charcoal-dust; in which case it is as difficult to get free of the sulphur as of the acid; and if we attempt it by frequent solutions in water, we destroy the phlogiston of the sulphur, and have only vitriolated tartar again instead of alkali. See CHEMISTRY, n^o 716, &c.

With respect to nitre, though its acid may be expelled by fire, yet it is too high-priced, and too much used in other manufactures, to be thought of for this purpose. A potash manufacture from sea-salt has indeed been lately erected in England. The principle on which this was established is, that the acid of sea-salt may be extracted by means of lime; and accordingly we find that the saline efflorescence, which frequently appears on walls, consists chiefly of the marine alkali deprived of its acid. But this, though delivered on the credit of a very eminent chemist, we can affirm from our own observation to be a mistake. Of the many cases in which we have examined this efflorescence, only one was found to be alkaline; the others uniformly appeared to be true Glauber's salt composed of the vitriolic acid and fossil alkali. Neither did this appear to be formed by any decomposition of salt originally in the plaster, but to be a real generation of both acid and alkali where none of them existed before. See EFFLORESCENCE.

Potatoes, it is generally thought, came originally from North America, where they were not reckoned good for food. They were first (we are told) introduced into Ireland in the year 1565, and from thence into England by a vessel wrecked on the western coast, called North Meals, in Lancashire, a place and soil even now famous for producing this vegetable in great perfection. It was 40 years after their introduction, however, before they were much cultivated about London; and then they were considered as rarities, without any conception of the utility that might arise from bringing them into common use. At this time they were distinguished from the Spanish by the name of Virginia potatoes, or battata, which is the Indian name of the Spanish ^* sort. At a meeting of the Royal Society, March 18th, 1662-3, a letter was read from Mr Buckland, a Somerset gentleman, recommending the planting of potatoes in all parts of the kingdom to prevent famine. This was referred to a committee; and, in consequence of their report, Mr Buckland had the thanks of the Society, such members as had lands were intreated to plant them, and Mr Evelyn was desired to mention the proposals at the close of his Sylva.

In Sweden, notwithstanding the indefatigable industry of Linnaeus, the culture of potatoes was only introduced in 1764, when a royal edict was published to encourage their general cultivation. They were known to them, however, at an earlier period; for in the Memoirs of the Royal Academy of Sciences in Sweden, 1747, M. Charles Skytte proposed to distil brandy from them, in order to save corn, which in that country is very dear. He found by experience, that an acre of land set with potatoes will yield a much greater quantity of brandy than when sown with barley.

The utility of potatoes to the common people is well known, and this utility has brought them into general use, and has extended them over every part of this kingdom. To promote this utility, and to make their cultivation more easy, a variety of experiments and inquiries have been made. Some of these we shall now lay before our readers, without repeating, however, what has been said on the same subject in the article AGRICULTURE, n^o 158-167. By many people the Irish purple potato is thought to be the sweetest and best; and of these the bright and middle-sized are directed to be set whole, in February, March, and April, in a fine deep tilth, in any soil. During the frost, the first setting should be covered with litter or fern. They should be set six inches deep, and a yard distant from each other every way, in a kind of hillocks like a mole-cast; and they must be moulded every month or fortnight, as high as possible. By July or August, under each hillock there will be nearly a bushel of potatoes. The white kidney potato runs all into stringy roots in loose ground, while the pink-coloured will do extremely well in the way we have now directed; and the smallest of them, though often given to hogs, unless they be otherwise improper or unhealthy, will be very good feed.

The following experiments concerning the culture of potatoes are related in the Georgical Essays.

“By all the experiments that have been made, the Howard or large Bedfordshire potato is found to produce the largest crop. On that account they are chiefly used in feeding of cattle. In two beds, four feet wide, and 200 feet long, I planted in a common field a sufficient number of sets of this kind of potato, and managed them by a horse-hoe. The produce was 64 bushels, each bushel up-heaped, weighing about 70 lb. My cattle eat them boiled with as much eagerness as the best sorts, and came on as well with them. I have built a boiling-house, &c. on Mr Young's plan, and during this whole winter have boiled potatoes for my cattle. For the fattening ones, I mix ground oats with them; and for the milk-cows, malt-dust; and dare venture to affirm, that they are much more profitable than either turnips or cabbages. Once, when my potatoes grew low, I desisted giving them to the milking-cows. Immediately, though fed with the best hay, they fell off amazingly in their milk. I therefore began again; and in a week's time they gave better than one-third more butter. I own this accidental discovery gave me much satisfaction, as it confirmed my opinion, that potatoes boiled are an excellent winter food for cattle. Their culture is not so difficult, at least not so precarious, as either turnips or cabbages. Their value is superior, and there is no risk of their giving a disagreeable taste either to butter or milk.

Potato. milk. Add to this the vast increase of the Howard potato, and its equality with the best sorts when used for cattle.

6 Of the increase of potatoes. "My gardener cut a large potato into nine pieces, which he planted with dung, in a drill, in the garden. By earthing up and laying the shoots, he produced 575 (A) sizeable potatoes, which weighed eight stone eight pound. Another of my servants produced, in the field, seven stone of good potatoes from the same number of sets. Though this experiment cannot always be executed in its full force in an extensive scale, it ought, notwithstanding, to be imitated as nearly as circumstances will allow. It shows, in the most distinguishing manner, the use of clean and careful husbandry.

"On the 14th of April, I cut a large white potato into 17 sets, which were planted in as many hillocks, at the distance of four feet. In the course of growing, the plants were earthed up, and on the 14th of October the crop was taken up: The produce, 10 pecks of sizeable potatoes. At the time that this experiment was made, I had several hillocks, in which I put three and four sets of the same kind of potato. But, upon the most careful examination, I could not observe that these hillocks produced a greater crop than the others planted with a single set. Hence it is obvious, that the potato spreads its roots most kindly when least crowded."

Whilst speaking of the increase of potatoes, we cannot help taking notice of a memoir by John Howard, Esq; of Cardington, in Bedfordshire, on a new kind of potato remarkable for its prolificacy. "In the year 1765 (says he) being at Clifton, near Bristol, I was informed a person had brought from America a new sort of potato, and with some trouble I procured half a dozen roots of it, as the greatest part of those brought over were already planted. That autumn I planted three of them, and in the following spring the other three, in my garden at Cardington in Bedfordshire; setting them in hillocks about six feet asunder. The strength of the stems, and largeness of the blossom and apples, gave the pleasing prospect of great increase; and accordingly, when I took them up in the autumn 1766, I found they had increased far beyond any of the common sort, which for some years I had encouraged our cottagers to cultivate. The produce from each cutting was in weight from 26 to 27 pounds and a half. I sent for two of the Bedford gardeners, who serve the market, to see them taken up, and they were surprised at the great increase. I gave some of them to the gardeners, and others to almost all our own cottagers. The increase continued to appear the same in the succeeding year, viz. 1767, as in the last: only, as many of the single potatoes had been then found to weigh four or five pounds each, I had now planted most of them in drills three feet asunder, in order to procure a greater number, and a less size. Their produce was now from 22 to 30 pounds from each cutting; and the potatoes were more

sizeable for common use. The vegetation was not so luxuriant as in those I before planted in hillocks; but the increase of these was, allowing the cuttings to weigh one ounce, full 400-fold. Having last year upwards of a waggon-load of these potatoes, I with pleasure ordered it to be made publicly known, that every person who chose to cultivate them were welcome to have a quantity for planting. In consequence of this, numbers applied in our own and the adjacent counties. In my plantations, as well as those of other persons, the increase has been still greater this year: for the season having proved very favourable, I have had from some hillocks 41 pounds and a half, allowing for dirt."

We now continue our extracts from the Geographical Essays.

7 "Take a bunch of the apples of any sort of potato. On raising Hang it up in a warm room during the winter, and in feeding February separate the seeds from the pulp, by washing potatoes the apples in water, and pressing them with the fingers. Then dry the seeds upon paper. In the month of April, sow these seeds, in drills, in a bed of earth well dug, and manured with rotten dung. When the plants are about an inch high, draw a little earth up to them with a hoe, in order to lengthen their main roots. When they are about three inches high, dig them up with a spade, and separate them carefully from each other, in order for planting out in the following manner. Prepare a piece of fresh ground by trenching it well. Dig up the seedling plants as before directed; and plant them out in the ground, thus prepared, in such a manner that there shall be 16 inches between each plant. As they advance in growth, let them receive one or two earthings up, in order to lengthen the main root, and encourage the shoots under ground. By this management, the potatoes will, in the course of one season, arrive at the size of hen's eggs, and the haulm will be as vigorous as if sets had been planted. But what proves the luxuriance in the most convincing manner, is, that flowers and apples are produced.

"In Lancashire, where the gardeners raise potatoes from seed, they are always two, and sometimes three, years in bringing them to full size. By the above method of transplanting, with wide distances, many of the potatoes nearly attain their full size in one season. It is observable, that these seedlings produce potatoes of all the different kinds; and sometimes new sorts are procured. We do not find any difference whether the apple comes from one kind or another. It is not so when we use the set, which invariably produces the same kind. Potatoes, when propagated from sets, after a number of years, are found to decrease in bearing; for which reason they should be brought back every 14 years to their original. From a want of attention to this circumstance, I have known potatoes so run out, that they hardly returned treble seed. The farmer complains that his land is tired of them; but the true cause

cause is the age of the sets. The increase of potatoes raised from seed is astonishing. They continue in vigour for about 14 years; after which the produce gradually declines.

"As the culture of potatoes, and particularly of the early sorts for the table, has of late become an object of very general attention, I hope the following account of a new method of obtaining these (without the help of hot-beds) will be acceptable to the public.

"On the 2d of January 1772, I made a hot-bed for the forward sort of potatoes, and on the 7th put in the sets, placing a glass and frame over them, and taking every precaution to defend them from the frost. Of these small potatoes, or sets, there remained about 40 in a basket, which was accidentally hung up in a warm kitchen, and there remained unnoticed till about the 25th of April. I then accidentally observed the basket, and perceiving something green on the edge of it, took it down, and, to my great surprise, found that the potatoes had sprouted half a yard in length, and that there were a great number of very small potatoes formed on the fibrous roots which had grown out. I took them into my garden, and planted them in a rich sandy soil, without any manure. The roots I put into the ground three inches deep, and laid down the stems that had sprouted, horizontally, and covered them with two inches of soil, but left the tops uncovered. Without farther attention they grew surprisingly.

"On the 26th of May, I took up the roots planted in the hot-bed on the 7th of January. They by no means answered my expectations, or paid for the trouble of their culture: but, at the same time, I was astonished to find the others, which were put into the ground so late, to have produced larger potatoes than the roots in the hot-bed. I took up all the roots, and picked off the large potatoes from them, which amounted to from 4 to 12 on each root, and then set the roots again in the same ground. This, indeed, I have successfully practised for many years, sometimes even twice, and have had a third good crop at Michaelmas. When this method is tried, the roots must be watered on the evenings of hot days.

"In January 1773, in order to make a second trial of this experiment with a large quantity, I placed a great many potatoes of the early sorts on a thick layer of gravelly soil, close to each other, over an oven, flatted over, but open to the south-west, and covered them two inches deep with the same earth. At the end of April I took them up, and found the stems about a foot long or more. For fear of injuring the fine and delicate fibres of the roots, I took great care in taking them up, and planting them in the soil. This I now manured, but in all other respects treated them in the manner above described, many of the fibrous roots having then potatoes formed upon them nearly as large as walnuts. For a week, the plants came on surprisingly, when, by one sharp night's uncommon frost, they were nearly destroyed. However, notwithstanding this, fresh stems grew up in a few days, and I actually gathered from them, on the 3d of June following, finer potatoes than were sold at that time, at Manchester, from 1 s. to 1 s. 6 d. per pound, being the produce of hot-beds. After taking off the larger potatoes, I again planted

the roots for a second crop, and in September obtained a very large produce. I weighed the increase of many separate roots, which amounted from four pound eight ounces to 14 pound 12 ounces, the potatoes being the largest of the forward kinds I ever saw.

"Make a compost of earth, sand, and coal-ashes. With this mixture fill a tub about 16 inches deep. Plant this artificial soil with some sets of the early round potato, and place the tub in a stable opposite to a window, taking care to water the earth now and then. In all seasons the sets will sprout, and give a tolerable increase of potatoes. Last November I planted some sets in the above manner; and in February following I took up a considerable number of young potatoes, clean skinned and well flavoured.

"On the 18th of May 1772, finding some beds I had sown very early with onions, to be a missing crop, I was induced to make the following experiment. The potato tops. I had set some potatoes in another part of my garden in the common way; and as it is impossible but some will remain in the ground all winter, so I found a number of sprouts about three inches high, which I nipped off close to the ground, and transplanted them into the onion-beds, without any further preparation, about a foot and a half asunder, in the same manner that cabbages and cauliflowers are planted. As the season became immediately very dry, I was obliged to give my plants a little water for four or five successive nights; after which they began to flourish, and had the appearance of a promising crop during all the summer. At the usual time, in October, I ordered them to be taken up; and for size, quantity, and quality, they exceeded all I ever had in the common way. Had the ground been fresh, properly manured and prepared, and the plants put down at a proper distance from each other, I am of opinion that the success would have been still greater.

"From an accurate experiment made last year, I dare venture to recommend baked potatoes as an excellent food for hogs. The pork produced by this food was equal to that from barley and beans: but at present I cannot exactly ascertain the comparative experiment with potatoes. with pota-
tatoes. I am of opinion, that roasted potatoes, considering the improvement of the hogs, is as cheap a food, if not cheaper, than can be given them. I roasted my potatoes upon a kiln, similar to what is used by oatmeal shellers for drying their oats. The difference in expence between boiling and roasting the potatoes is prodigious, both with regard to the labour and fuel. A kiln that will cost 3 l. will roast potatoes sufficient for the maintenance of more than 20 hogs; and one man will bestow all the necessary attendance upon them, and do other work besides. The action of the fire, by dissipating the crude juices that are contained in raw potatoes, reduces them into a state highly wholesome and nutritious. Boiling does this in part, but not so effectually. A potato roasted in the manner above described, partakes much of the nature of a chestnut, and perhaps is not greatly inferior to it."

Potatoes are found to be useful food for most other animals. See AGRICULTURE, n^o 45.

To these experiments we shall add some important observations of Dr Anderson of Cotesfield near Leith, who

who has paid a very particular attention to this as well as other branches of agriculture. Our readers will find the Doctor's remarks and experiments at large in the Bath Papers, volume fourth. He first considers the nature of the feeds most proper to be planted; and from his experiments he thinks it appears that the produce is not materially affected, by planting for feed, either whole potatoes or cuttings, or large or small potatoes as such; for it is only incidentally that these things can affect the crop. In the fifth volume of the Bath Papers, Mr Wimpey relates an experiment, by which it would appear that there is an advantage in planting cut potatoes. His conclusion is as follows. "The measure of all the ground planted, says he, was 325 poles; the whole produce 378 bushels. The measure of the ground planted with cut potatoes was 265 poles; the produce 312 bushels. The ground planted with whole or uncut sets was 60 poles, and the produce of the same 66 bushels. Now, if 48 bushels, the whole quantity of sets used, produced 378 bushels, then 34 bushels, the quantity cut, should produce 267 bushels; but they produced 312, which is 45 bushels more than the proportion. Again, if 48 bushels produced 378 bushels, then 14 bushels should have produced 110 bushels; but 14 bushels of uncut produced only 66 bushels, which is 44 bushels less than the proportion. A preference of 40 per cent. in favour of cut potatoes, in comparison with whole sets." Mr Wimpey corroborates the fact in the sixth volume of the same work, and informs us, moreover, that he used to supply many of his neighbours with potatoes for planting; some of whom desired to have them all small, as they had found them equally productive with the larger, and saved much trouble in cutting. "Others (continues he) preferred the largest, who carried their economy much further: they, it seems, used to pare them, eat the fleshy part, and plant the rinds only. Upon inquiry, I found it was not an usual practice among the cottagers; and I have been credibly informed they get as large crops and as good potatoes in that method of planting as in any other whatever. If this be a fact, it seems to appear that the fleshy part of the bulb is of no use in supplying nourishment to the young fruit after the fibrous roots have put forth and laid hold of the ground. Perhaps an experiment of this sort may be thought worth making." The weight of the crop, however, Dr Anderson asserts (and Mr Wimpey agrees with him, see Bath Papers, vol. v. p. 34.), is always in some measure influenced by the weight of the feeds planted; but the weight of produce is not augmented in the same proportion with the weight of the feed planted; the smallest feed yielding the greatest returns in proportion to the feed, but the smallest in proportion to the extent of ground. It is in no case profitable, however, the Doctor thinks to plant small potatoes (a), or small cuttings, unless where it is meant to increase

as fast as possible a favourite kind; in which case it may be sometimes eligible to plant pieces very small, as in that way the kind will be most quickly multiplied. We may also remark here, that such as wish for a large increase should never plant the worst of the crop; it is, we know, extremely common, and may indeed be an immediate saving; but it is unquestionably a loss upon the whole; and perhaps it is one cause of the evil disease, which is the sure indication of a poor dwindling crop, and of which we shall speak more at large immediately.

Our author further remarks, that there seems to be no reason to suspect that eyes taken from any particular part of the bulb are possessed of a degree of prolificacy greater than those taken from any other part of it, independent of the size of the fleshy part that adheres to the eye. It is however highly probable that a difference in the crop, either with respect to the number and size, or general weight of the whole, would result from planting large cuttings of equal weight, taken from the big end of large potatoes, or from the point, as many eyes would be in the last in comparison of the first. This is therefore one of the many preparatory experiments that require to be made. It is possible too that even the apples may be an object of value, and may indicate a thriving crop or otherwise; but of this there is no certainty, as no specific experiments have yet been made on this subject.

With respect to the effects of cutting the stems of potatoes while growing, the Doctor seems to be doubtful. The stems of potatoes, if cut while growing, and used green, are found to be a wholesome food for cattle and horses. But though some farmers maintain that the produce in potatoes is not lessened by having the stems cut off while they are in a state of vigorous vegetation; others as positively insist that the crop is essentially injured by that operation. It is proper that this point should be ascertained. Probably the crop is hurt if the stems are cut over before they have attained a certain point of maturity, though it is possible they may be afterwards cut without doing any essential injury to it.

We have already mentioned that an experiment was made a good while ago in Sweden, to extract ardent spirits from potatoes. Other experiments have been made in this country of a later date, but with little effect. This, however, appears to have proceeded either from ignorance or a want of proper attention to the fermentation and after distillation; as appears from Dr Anderson's experiment, which succeeded extremely well by attending to these processes. What he made he asserts to have been the finest and most agreeable vinous spirit he ever saw, resembling in taste very fine brandy, but more mild, and having a certain coolness on the stomach peculiar to itself.

Much may be done in bringing potatoes to perfection

tion by attending to their several varieties. For this purpose some particular potato must be fixed upon as a standard; and when this is done, the inquiry must be carried on by attending, first, to their appearances below ground, as, 1. the general form and size of the bulbs; 2. their colour; 3. the smoothness or roughness of the skin; 4. the consistence, that is, the mealiness or viscosity and taste of the bulb; 5. the colour, length, thickness, &c. of the umbilical cord; 6. their tendency to go deep, or to rise near the surface; to ramble wide, or to adhere close to the stem; 7. the time when the bulbs knot and set; marking, not by the calendar only, but also compared with the advance of the plant above ground; 8. the time when they attain perfect maturity with respect to size, and also that period of their growth at which they lose the herbaceous, and attain the farinaceous, taste; 9. their general prolificacy; 10. how long they may be kept, at what season they are in greatest perfection for eating, &c. We must next attend to the particulars observable above-ground; as, 1. the general height, colour, and form of the stem; 2. their tendency to push out many or few stems from a root; 3. whether they carry blossom or not; 4. the form, dimensions, and colour of the leaves; 5. the form, colour, and general habitude of the blossom where there is any; 6. the time at which the blossom appears; 7. the tendency they have to produce few or many apples; 8. the tendency they have to produce those excrecences on the stalks that resemble potatoes below ground, which may be called air potatoes; 9. the comparative hardness or tenderness of the leaves, in respect of frost or other variations of weather that affect them. And, lastly, we must attend to the particulars that concern the whole plant; as, 1. the soil which seems best to suit each kind; 2. the mode of culture that best agrees with them; 3. the accidents which are most liable to affect them; and in general every particular that could indicate any difference between one kind and another.

Our author next considers the circumstances of raising feeding potatoes. His mode of raising them was similar to that recommended in the Georgical Essay quoted above; but he differs with respect to the utility or success of that mode. It has been alleged, he says, that potatoes, which have been long propagated by means of bulbs, lose in time their generative quality, so as to become much less prolific than at first; and it is asserted that those bulbs which have been lately obtained from feeds are much more prolific, and consequently much more profitable for being employed as plants than others; but this opinion appears to have been adopted without sufficient examination: for there appears not the smallest indication of superior prolificacy in those raised from feeds, but rather the reverse. That potatoes do not degenerate in point of prolificacy in consequence of being long propagated in the usual way, seems to be confirmed by the general experience of all Europe. It is now about a hundred years since the potato was pretty generally cultivated in Ireland, and it has been very universally cultivated in Britain for

50 years past; and all that have been reared in it since their first introduction two hundred years ago, a very few of late only excepted, have been propagated from bulbs only; so that if they had declined in point of prolificacy, the degeneracy should in this time have been very apparent. Nothing of that kind however was ever remarked, nor any insinuation of that sort thrown out, till the discovery of rearing potatoes from seed was made, when it was for the first time heard of. There are many persons now living who have been in the constant practice of rearing potatoes for 30 or 40 years; and notwithstanding the general tendency that mankind have to dispraise the present, when compared to past times, yet none of them have given the smallest hint of degeneracy in this respect. And perhaps it will be found that this is merely a groundless notion, that has originated from the partial fondness of those who first propagated this plant from seed, in favour of their new discovery. It has been further said, that by raising potatoes from seed, many new and valuable kinds may be obtained; and it is also asserted in the Georgical Essay. Indeed an opinion of obtaining new varieties of plants by propagating them from seed universally prevails among naturalists. But Dr Anderson, in his first paper, doubts whether this be fact, and whether, when any of these occur, they have not been the effect of accidental position or other causes. We may certainly (says he) assert on the whole, that if the practice of rearing potatoes from seeds shall ever be productive of any advantages to society, they have not yet been discovered. Since he wrote that treatise which appears in the Bath Papers, vol. iv. (and of which we are now giving a short account), however, he has had occasion to alter his opinion, which he does with great candour in vol. v. The experiment which induced him to alter his opinion, and which appears to be decisive, was made with the seed of a potato procured from Ireland of a very peculiar kind. Its colour was a dirty dark purple, its shape a round irregular bulb, and its stem tall and upright. The seeds procured from this potato were sown by themselves, and the seedlings when of a proper size were transplanted. From the appearance of the stems he soon discovered that they were not all of one sort, and on taking them up the variety was almost infinite; and such as could not be accounted for on the principles of a mongrel adulteration. The diversities respected colour, shape, &c. some of which he enumerates. See Bath Papers, vol. v. p. 127; see also p. 35. where Mr Wimpey controverts the Doctor's former opinion.

Respecting the causes and prevention of the curled On the disease in potatoes there has been a great variety of opinions, which we have detailed at some length under the article AGRICULTURE, p. 267 to 270. Dr Anderson confesses that he can say but little positive as to the cause of this disorder, but he thinks a good deal may be said on the negative side of the question. It was little known till lately (c), and in the northern parts of this island it was absolutely unknown but a very few years ago; and even now in the more remote corners it is still less frequent than in the more southern and

Potato. and more commercial districts of the island. It has been supposed that nature, fated as it were by having long produced this plant in a climate not deemed congenial to it, had become so far exhausted as to occasion this disease. But in this case, the more northern parts, where the climate is most unfavourable, should have been soonest affected. It has been also thought that potatoes, whose bulbs are frost-bitten before they are housed, occasion this disease in the plants they produce. But the fact is, that they are least liable to the disease in those districts where they are most exposed to frost. A potato can never indeed be benefited by frost; but it is not at all probable that the being touched by it occasions the curl. The taking up potatoes before they arrive at maturity has been thought to occasion the disease; but in places where they must be taken up so, the disease is scarcely known. It has also been thought that potatoes obtained from feed are entirely free from it. But Dr Anderson gives a proof of the contrary; for one half of the plants of a large field planted from potatoes the third year from the feed were curled; while another field adjoining raised from potatoes that never were, that he knows, produced from feed in this country, had scarcely one curled plant in the whole. The disease has been supposed by others to arise from the soil or season. But that this is not the case, appears from the circumstance of a single field which Dr Anderson planted with potatoes of the very same sort, but obtained from different persons. The ridges were intermixed, and the one was very much curled, and the other perfectly free. The disease, therefore, appears to arise from infected seed: it is however possible that it may be communicated by juxtaposition; and if so, the disease might be in a great measure if not entirely avoided, by pulling out those that showed the least symptom of it, on their first appearing above ground.

In the Transactions of the London Society for encouragement of arts, &c. we find a good deal about the curl disease. Many of the writers agree in opinion with Dr Anderson in many particulars; and particularly, that though the disease may be prevented, we do not yet know enough of its nature to be able to cure it. See their vol. viii. p. 18, &c. ix. p. 52, &c. and x. p. 75. In this last volume we are told that the principal causes of the curl are three: 1. From their being forced by cultivation to overgrow their power for vegetation; 2. From their vegetative power being dried up in ebb soil by the scorching heat of the sun; and, 3. From their being exposed too long after they are cut in sets before they are planted.

18
On the soil and season most proper for potatoes. It is generally and very naturally believed that a dry soil or a dry season necessarily produces the driest potatoes. But there is good reason to doubt the truth of the opinion. The year 1775 was the driest and warmest season that has been known in Scotland within the memory of man, yet the potatoes of that year's crop were watery almost to a proverb: on the other hand, the potatoes of crop 1777, although it was a remarkably rainy season, were as dry and mealy at least

as is common, and much more so than in the year 1775. It deserves also to be remarked, that the crop of 1775 was almost double in quantity to that of 1777. Hence a dry season would seem to augment the produce, though it does not for certain in all cases improve the quality, of this crop: nor does a dry soil necessarily insure mealy potatoes; for our author says he has often seen potatoes of the same kind, and of the same year's produce, reared in two different places; the one of them in a naturally damp soil, which turned out to be much freer and more mealy than the others which were reared on a drier and sharper soil. He confesses, that he has also often seen it turn out in fact, that potatoes raised in those districts where the soil is hot and sandy, are usually more free and tender than those raised in countries where the soil is cold and damp. Our author tries to account for these contradictory phenomena by conjecturing the probable cause of the wateryness or dryness of a crop. He asks, Whether in this respect the crop is anywise affected by the degree of ripeness that the plants employed for feed may have attained in the preceding season? That this is the case he thinks highly probable. Potatoes which, on account of the richness or other peculiarity of the soil, continue in a state of vegetation highly luxuriant till they are nipped by frost, or checked in their growth by other inclemencies of the season, have much less chance of being dry and mealy than others of the same sort which have attained their full growth before the coldness or inclemency of the weather checked them. But our author's question does not relate to this, but to the effect these unripe potatoes, used as feed, would have on the succeeding crop; a circumstance which experience alone can determine. "But even if it should be found (continues our author) that the maturity of the feeds affected the quality of the potatoes, it would not follow invariably that the feeds produced on early dry soils would be better than those from later soils; because it might sometimes happen from local position, and other accidental circumstances, that the growth of the potatoes in the dry early soil might be checked by frosts many weeks before those on the other soil were affected, in consequence of which the plants in the cold soil might attain to more perfect maturity than those on the drier one. I mention this peculiarity merely to show how cautious the farmer ought to be in adopting general conclusions without carefully attending to all the collateral circumstances that may affect his experiment. I shall only farther add on this head, that I had occasion to know well a dry warm spot of ground on which the stems of the potatoes of crop 1776 were frost-bitten at least six weeks before those on another spot at some miles distance from it, where the soil was naturally more cold and damp, were in the smallest degree affected by it. It likewise so happened, that the potatoes raised on the first-mentioned spot in the year 1777 (their own frost-bitten (d) feed was employed) had such a peculiar acrid and bitterish taste as to be hardly at all eatable, while those in the colder place of that crop had nothing of that unusual

Potato. usual taste. Whether this diversity was occasioned by the circumstance here alluded to, I do not take it on me to say. In matters of such nice disquisition as the present, many facts obtained by very accurate observation are necessary before any conclusion can be relied on."

Potatoes, when planted in water, shoot out a great number of fine white roots like threads into the water; but on none of them is there to be found the least appearance of a bulb; while on the other hand the potatoes in that case always grow on the top. Potatoes are found to be extremely useful in bringing exhausted land into heart again. See AGRICULTURE, n. 35 and 186, p. 300, col. 1. The bishop of Killaloe in Ireland directs the use of them for this purpose in a letter in the Bath Papers, vol. 4. p. 232, and confirms its utility in this respect by experiments of his own. In the 10th vol. of the Transactions of the London Society for Encouragement of Arts, &c. p. 34, there is also a most decisive proof of this utility.

We have been induced, from the extensive utility of this root, to extend our observations on the subject to a greater length than we should otherwise have done. Such of our readers as wish for further information, will of course consult the books from which we have made up the present article, as well as other books on Agriculture; in which they will find the observations and experiments which we have mentioned at much greater length than we could possibly give them. In the sixth volume of the Bath Society Papers there is an excellent paper on the culture of potatoes and feeding hogs with them during seven years by John Billingfley Esq; of which our limits do not permit us to take particular notice. There are also a variety of other papers in the several volumes of that work, as well as in the Transactions of the London Society, which we have already several times mentioned; which will deserve the particular attention of such as wish well to the poor, or have a desire still farther to extend the utility of this most valuable root. We have already mentioned a cheap preparation by means of potatoes for the poor, see AGRICULTURE, n. 161; and we shall finish the present article with a receipt to make a potato herrico, which may be equally useful to those whose circumstances are not such as to make them regardless of economy. We take it from the Gentleman's Magazine, and give it in the words of a person who had tried the experiment.

Scrape the skin clean off four pounds of good raw potatoes, then wash them clean in fair water: take two pounds of beef, one of mutton, and one of pork; or as you like best, four pounds of any of these meats; cut them into pieces of three or four ounces each, season them very well with pepper and salt and a good onion chopped very small: have ready a strong wide-mouthed stone-jar, such as hares are usually juggled in; slice thin a layer of the potatoes into the jar, then a layer of the seasoned meat over them, and so alternately layers of potatoes and meat; let your uppermost layer be potatoes, so that your jar be about three quarters full, but put no water into your jar; then close or stop the mouth of it with a large well-fitted piece of cork, covering the same with a strong piece of canvas, and tying it down with pack-thread, so as only a little of the steam may escape in the stewing; for a little should constantly evaporate from the side of the cork to save the jar from bursting. Then place your jar upright in a kettle of

cold water on the fire, so as the mouth of the jar may be always two inches above the water in the kettle when boiling. The herrico in the jar will begin to boil some minutes sooner than the water in the kettle, and that for obvious reasons. In about an hour after the water in the kettle begins to boil, your herrico will be fully stewed. Then take out and open the jar, pour out the herrico into a deep dish, and serve it up.

This excellent, wholesome, and economical dish supplies an agreeable dinner twice a week to a family consisting of three grown people, and three children under fourteen years of age, where neither health nor good stomachs are wanting, thanks to God: and, in point of economy we must observe, that here is the whole article of butter saved, as also the whole article of bread, or nearly so; nor does there require so large or so continued a fire, nor so much time or trouble as is necessary for the dressing of many other dishes that by no means deserve the preference to this excellent herrico.

We have also (by way of change) made it with powdered beef, sometimes with powdered pork, sometimes with half fresh beef or mutton and half pickled pork, and found it good in all these ways, particularly with three pounds of fresh beef and one of pickled pork. We have left off sending pies and stews to the bakers. We sometimes (in a larger kettle) boil a small piece of powdered beef along-side of the jar, by continuing the boiling an hour and an half longer, and this serves us to eat cold the next day, with hot garden-stuff or a pudding.

Potato-Bread. See BREAD of Potatoes.

Spanish Potato. See CONVOLVULUS, n. 5.