in building, a composition of white marble pulverised, and mixed with plaster of lime; and the whole being sifted and wrought up with water, is to be used like common plaster: this is called by Pliny marmoratum opus, and albarium opus.

A patent has been granted to Mr B. Higgins for inventing a new kind of stucco, or water-cement, more firm and durable than any heretofore. Its composition, as extracted... tracted from the specification signed by himself, is as follows: "Drift-sand, or quarry (A) sand, which consists chiefly of hard quartzose flat-faced grains with sharp angles; which is the freest, or may be most easily freed by washing, from clay, fels, and calcareous, gypseous, or other grains less hard and durable than quartz; which contains the smallest quantity of pyrites or heavy metallic matter inseparable by washing; and which suffers the smallest diminution of its bulk in washing in the following manner—is to be preferred before any other. And where a coarse and fine sand of this kind, and corresponding in the size of their grains with the coarse and fine sands hereafter described, cannot be easily procured, let such sand of the foregoing quality be chosen as may be sorted and cleansed in the following manner:

"Let the sand be sifted in streaming clear water, thro' a sieve which shall give passage to all such grains as do not exceed one-sixteenth of an inch in diameter; and let the stream of water and the sifting be regulated so that all the sand, which is much finer than the Lynn-sand commonly used in the London glasshouses, together with clay and every other matter specifically lighter than sand, may be washed away with the stream, whilst the purer and coarser sand, which passes through the sieve, subsides in a convenient receptacle, and whilst the coarse rubbish and rubble remain on the sieve to be rejected.

"Let the sand which thus subsides in the receptacle be washed in clean streaming water through a finer sieve, so as to be further cleansed and sorted into two parcels; a coarse, which will remain in the sieve which is to give passage to such grains of sand only as are less than one-thirtieth of an inch in diameter, and which is to be saved apart under the name of coarse sand; and a finer, which will pass through the sieve and subside in the water, and which is to be saved apart under the name of fine sand.—Let the coarse and the fine sand be dried separately, either in the sun or on a clean iron-plate, set on a convenient furnace, in the manner of a sand-heat (B).

"Let lime be chosen (C) which is stone-lime, which heats the most in flaking, and flakes the quickest when duly watered; which is the freest made and closest kept; which dissolves in distilled vinegar with the least effervescence, and leaves the smallest residue insoluble, and in this residue the smallest quantity of clay, gypsum, or martial matter.

"Let the lime chosen according to these important rules be put in a brass-wired sieve to the quantity of 14 pounds. Let the sieve be finer than either of the foregoing; the finer, the better it will be: let the lime be flaked (D) by plunging it in a butt filled with soft water, and raising it out quickly and suffering it to heat and fume, and by repeating this plunging and raising alternately, and agitating the lime, until it be made to pass through the sieve into the water; and let the part of the lime which does not easily pass through the sieve be rejected; and let fresh portions of the lime be thus used, until as many (E) ounces of lime have passed through the sieve as there are quarts of water in the butt. Let the water thus impregnated stand in the butt closely covered (F) until it becomes clear; and through wooden (G) cocks placed at different heights in the butt, let the clear liquor be drawn off as fast (H) and as low as the lime subsides, for use. This clear liquor I call the cementing liquor (I). The freer the water is from saline matter, the better will be the cementing liquor made with it.

---

(A) "This is commonly called pit-sand.

(B) "The sand ought to be stirred up continually until it is dried, and is then to be taken off; for otherwise the evaporation will be very slow, and the sand which lies next the iron plate, by being overheated, will be discoloured.

(C) "The preference given to stone-lime is founded on the present practice in the burning of lime, and on the closer texture of it, which prevents it from being so soon injured by exposure to the air as the more spongy chalk-lime is; not on the popular notion that stone-lime has something in it whereby it excels the best chalk in the cementing properties. The gypsum contained in lime-stone remains unaltered, or very little altered, in the lime, after the burning; but it is not to be expected that clay or martial matter should be found in their native state in well-burned lime; for they concretate or vitrify with a part of the calcareous earth, and constitute the hard grains or lumps which remain undissolved in weak acids, or are separable from the flaked lime by sifting it immediately through a sieve.

(D) "This method of impregnating the water with lime is not the only one which may be adopted. It is, however, preferred before others, because the water clears the sooner in consequence of its being warmed by the flaking lime; and the gypseous part of the lime does not diffuse itself in the water so freely in this way as it does when the lime is flaked to fine powder in the common method, and is then blended with the water; for the gypseous part of the lime flakes at first into grains rather than into fine powder, and will remain on the sieve after the pure lime has passed through, long enough to admit of the intended separation; but when the lime is otherwise flaked, the gypseous grains have time to flake to a finer powder, and passing through the sieve, dissolve in the water along with the lime. I have imagined that other advantages attended this method of preparing the lime-water, but I cannot yet speak of them with precision.

(E) "If the water contains no more acidulous gas than is usually found in river or rain water, a fourth part of this quantity of lime, or less, will be sufficient.

(F) "The calcareous crust which forms on the surface of the water ought not to be broke, for it assists in excluding the air, and preventing the absorption of acidulous gas whereby the lime-water is spoiled.

(G) "Brass-cocks are apt to colour a part of the liquor.

(H) "Lime-water cannot be kept many days unimpaired, in any vessels that are not perfectly air-tight. If the liquor be drawn off before it clears, it will contain whitening, which is injurious; and if it be not instantly used after it is drawn limpid from the butt into open vessels, it will grow turbid again, and deposit the lime changed to whitening by the gas absorbed from the air. The calcareous matter which subsides in the butt resembles whitening the more nearly as the lime has been more sparingly employed; in the contrary circumstances, it approaches to the nature of lime; and in the intermediate state, it is fit for the common composition of the plasterers for inside stucco.

(I) "At the time of writing this specification, I preferred this term before that of lime-water, on grounds which I had not sufficiently examined." Let 6 pounds of the aforeaid chosen lime be flaked, by gradually sprinkling on it, and especially on the unflaked pieces, the cementing liquor, in a clofe (x) clean place. Let the flaked part be immediately (L) fitted through the last-mentioned fine brass-wired sieve; let the lime which passes be used instantly, or kept in air-tight vessels, and let the part of the lime which does not pass through the sieve be rejected (m).—This finer richer part of the lime which passes through the sieve I call purified lime.

Let bone-ash be prepared in the usual manner, by grinding the whitest burnt bones, but let it be fitted, to be much finer than the bone-ash commonly sold for making cupels.

The most eligible materials for making my cement being thus prepared, take 56 pounds of the coarse sand and 42 pounds of the fine sand; mix them on a large plank of hard wood placed horizontally; then spread the sand so that it may stand to the height of six inches, with a flat surface on the plank; wet it with the cementing liquor; and let any superfluous quantity of the liquor, which the sand in the condition described cannot retain, flow away off the plank. To the wetted sand add 14 pounds of the purified lime in several successive portions, mixing and beating them up together in the mean time with the instruments generally used in making fine mortar; then add 14 pounds of the bone-ash in successive portions, mixing and beating all together. The quicker and the more perfectly these materials are mixed and beaten together, and the sooner the cement thus formed is used, the better (n) it will be. This I call the water-cement coarse-grained, which is to be applied in building, pointing, plastering, stuccoing, or other work, as mortar and stucco now are; with this difference chiefly, that as this cement is shorter than mortar or common stucco, and dries sooner, it ought to be worked expeditiously in all cases; and in stuccoing, it ought to be laid on by sliding the trowel upwards on it; that the materials used along with this cement in building, or the ground on which it is to be laid in stuccoing, ought to be well wetted with the cementing liquor in the instant of laying on the cement; and that the cementing liquor is to be used when it is necessary to moisten the cement, or when a liquid is required to facilitate the floating of the cement.

When such cement is required to be of a finer texture, take 98 pounds of the fine sand, wet it with the cementing liquor, and mix it with the purified lime and the bone-ash in the quantities and in the manner above described; with this difference only, that 15 pounds of lime, or (o) thereofabouts, are to be used instead of 14 pounds, if the greater part of the sand be as fine as Lynn sand. This I call water-cement fine-grained. It is to be used in giving the last coating, or the finish to any work intended to imitate the finer-grained stones or stucco. But it may be applied to all the uses of the water-cement coarse-grained, and in the same manner.

When for any of the foregoing purposes of pointing, building, &c., such a cement is required, much cheaper and coarser-grained, then much coarser clean sand than the foregoing coarse sand, or well-washed fine rubble, is to be provided. Of this coarse sand or rubble take 56 pounds, of the foregoing coarse sand 28 pounds, and of the fine sand 14 pounds; and after mixing these, and wetting them with the cementing liquor in the foregoing manner, add 14 pounds, or somewhat less, of the (p) purified lime, and then 14 pounds or somewhat less of the bone-ash, mixing them together in the manner already described. When my cement is required to be white, white sand, white lime, and the whitest bone-ash are to be chosen. Grey sand, and grey bone-ash formed of half-burnt bones, are to be chosen to make the cement grey; and any other colour of the cement is obtained, either by choosing coloured sand, or by the admixture of the necessary quantity of coloured talc in powder, or of coloured, vitreous, or metallic powders, or other durable colouring ingredients commonly used in paint.

To the end that such a water-cement as I have described may be made as useful as it is possible in all circumstances; and that no person may imagine that my claim and right under these letters-patent may be eluded by divers variations, which may be made in the foregoing process without producing any notable defect in the cement; and to the end that the principles of this art, as well as the art itself, of making my cement, may be gathered from this specification and perpetuated to the public; I shall add the following observations:

This my water-cement, whether the coarse or fine grained, is applicable in forming artificial stone, by making alternate layers of the cement and of flint, hard stone, or brick.

(x) "The vapour which arises in the flaking of lime contributes greatly to the flaking of these pieces which lie in its way; and an unnecessary waste of the liquor is prevented, by applying it to the lime heaped in a pit or in a vessel, which may restrain the issue of the vapour, and direct it through the mats. If more of the liquor be used than is necessary to flake the lime, it will create error in weighing the flaked powder, and will prevent a part of it from passing freely through the sieve. The liquid is therefore to be used sparingly, and the lime which has escaped its action is to be sprinkled apart with fresh liquor.

(L) "When the aggregation of the lumps of lime is thus broken, it is impaired much sooner than it is in the former state, because the air more freely pervades it.

(m) "Because it consists of heterogeneous matter or of ill-burnt lime; which last will flake and pass through the sieve, if the lime be not immediately fitted after the flaking, agreeable to the text.

(n) "These proportions are intended for a cement made with sharp sand, for incrustation in exposed situations, where it is necessary to guard against the effects of hot weather and rain. In general, half this quantity of bone-ashes will be found sufficient; and although the incrustation in this latter case will not harden deeply so soon, it will be ultimately stronger, provided the weather be favourable.

"The injuries which lime and mortar sustain by exposure to the air, before the cement is finally placed in a quiescent state, are great; and therefore our cement is the worse for being long beaten, but the better as it is quickly beaten until the mixture is effected, and no longer.

(o) "The quantity of bone-ashes is not to be increased with that of the lime; but it is to be lessened as the exposure and purposes of the work will admit.

(p) "Because less lime is necessary, as the sand is coarser." brick, in moulds of the figure of the intended stone, and by exposing the masses so formed to the open (q) air to harden.

"When such cement is required for water (r) fences, two-thirds of the prescribed quantity of bone-ashes are to be omitted; and in the place thereof an equal measure of powdered terras is to be used; and if the sand employed be not of the coarsest sort, more terras must be added, so that the terras shall be by weight one-sixth part of the weight of the sand.

"When such a cement is required of the finest grain (s) or in a fluid form, so that it may be applied with a brush, flint powder, or the powder of any quartzo or hard earthy substance, may be used in the place of sand; but in a quantity smaller, as the flint or other powder is finer; so that the flint-powder, or other such powder, shall not be more than five times the weight of the lime, nor less than four times its weight. The greater the quantity of lime within these limits, the more will the cement be liable to crack by quick drying, and vice versa.

"Where such sand as I prefer cannot be conveniently procured, or where the sand cannot be conveniently washed and sorted, that sand which most resembles the mixture of coarse and fine sand above prescribed, may be used as I have directed, provided due attention is paid to the quantity of the lime, which is to be greater (t) as the quantity is finer, and vice versa.

"Where sand cannot be easily procured, any durable stony body, or baked earth grossly powdered (u), and sorted nearly to the sizes above prescribed for sand, may be used in the place of sand, measure for measure, but not weight for weight, unless such gross powder be as heavy specifically as sand.

"Sand may be cleaned from every softer, lighter, and less durable matter, and from that part of the sand which is too fine, by various methods preferable (x), in certain circumstances, to that which I have described.

"Water may be found naturally free from fixable gas, selenite, or clay; such water may, without any notable inconvenience, be used in the place of the cementing liquor; and water approaching this state will not require so much lime as I have ordered to make the cementing liquor; and a cementing liquor sufficiently useful may be made by various methods of mixing lime and water in the described proportions, or nearly so.

"When stone-lime cannot be procured, chalk-lime, or shell-lime, which best resembles stone-lime, in the characters above written of lime, may be used in the manner described, except that fourteen pounds and a half of chalk-lime will be required in the place of fourteen pounds of stone-lime. The proportion of lime which I have prescribed above may be increased without inconvenience, when the cement or stucco is to be applied where it is not liable to dry quickly; and in the contrary circumstance, this proportion may be diminished; and the defect of lime in quantity or quality may be very advantageously supplied (y), by causing a considerable quantity of the cementing liquor to soak into the work, in successive portions, and at distant intervals of time, so that the calcareous matter of the cementing liquor, and the matter attracted from the open air, may fill and strengthen the work.

"The powder of almost every well-dried or burnt animal substance may be used instead of bone-ash; and several earthy powders, especially the micaceous and the metallic; and the eluated ashes of divers vegetables whose earth will not burn to lime; and the ashes of mineral fuel, which are of the calcareous kind, but will not burn to lime, will answer the defects of bone-ash in some degree.

"The quantity of bone-ash described may be lessened without injuring the cement, in those circumstances especially which admit the quantity of lime to be lessened, and in those wherein the cement is not liable to dry quickly. And the art of remedying the defects of lime may be advantageously practised to supply the deficiency of bone-ash, especially in building, and in making artificial stone with this cement.

---

(q) "But they must not be exposed to the rain until they are almost as strong as fresh Portland stone; and even then they ought to be sheltered from it as much as the circumstances will admit. These stones may be made very hard and beautiful, with a small expense of bone-ash, by soaking them, after they have dried thoroughly and hardened, in the lime liquor, and repeating this process twice or thrice, at distant intervals of time. The like effect was experienced in incrustations.

(r) "In my experiments, mortar made with terras-powder, in the usual method, does not appear to form so strong a cement for water-fences as that made, according to the specification, with coarse sand; and I see no more reason for avoiding the use of sand in terras-mortar, than there would be for rejecting stone from the embankment. The bone-ashes meant in this place are the dark grey or black sort. I am not yet fully satisfied about the operation of them in this instance.

(s) "The qualities and uses of such fine calcareous cement are recommended chiefly for the purpose of smoothing and finishing the stronger crustaceous works, or for washing walls to a lively and uniform colour. For this last intention, the mixture must be as thin as new cream, and laid on briskly with a brush, in dry weather; and a thick and durable coat is to be made by repeated washing; but is not to be attempted by using a thicker liquor; for the coat made with this last is apt to scale, whilst the former endures the weather much longer than any other thin calcareous covering that has been applied in this way. Fine yellow-ochre is the cheapest colouring-ingredient for such wash, when it is required to imitate Bath-stone, or the warm-white stones.

(t) "If sea-sand be well washed in fresh water, it is as good as any other round sand.

(u) "The cement made with these and the proper quantities of purified lime and lime-water, are inferior to the best, as the grains of these powders are more perishable and brittle than those of sand. They will not therefore be employed, unless for the sake of evanescence, or for want of sand; in this latter case, the finer powder ought to be washed away.

(x) "This and the next paragraph is inserted with a view to evasions, as well as to suggest the easier and cheaper methods which may be adopted in certain circumstances, by artists who understand the principles which I endeavour to teach.

(y) "This practice is noticed, as the remedy which may be used for the defects arising from evasive measures, and as the method of giving spongey incrustations containing bone-ashes the greatest degree of hardness."