in Natural History, a fountain or source of water rising out of the ground. Many have been the conjectures of philosophers concerning the origin of fountains, and great pains have been taken both by the members of the Royal Society and those of the Academy of Sciences at Paris, in order to ascertain the true cause. It was Aristotle's opinion, and held by most of the ancient philosophers after him, that the air contained in the caverns of the earth, being condensed by cold near its surface, was thus changed into water; and that it made its way where it could find a passage. But we have no experience of any such transmutation of air into water.

Those who imagine that fountains owe their origin to waters brought from the sea by subterraneous ducts, give a tolerable account how they lose their saltiness by percolation as they pass through the earth; but they find great difficulty in explaining by what power the water rises above the level of the sea to near the tops of mountains, where springs generally abound; it being contrary to the laws of hydrostatics, that a fluid should rise in a tube above the level of its source. They have however found two ways by which they endeavoured to extricate themselves from this difficulty. The one is that of Des Cartes, who imagines that after the water has become fresh by percolation, it is raised out of the caverns of the earth in vapour towards its surface; where meeting with rocks near the tops of mountains in the form of arches or vaults, its adheres to them, and, like water in an alembic, runs down their sides, till

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1 Laing's History of Scotland, vol. iii. p. 154. it meets with proper receptacles, from which it supplies the fountains. Now this is a mere hypothesis, without foundation or probability: for, in the first place, we know of no internal heat of the earth sufficient to cause such evaporation; or if that were allowed, yet it is quite incredible that there should be any caverns so smooth and void of protuberances as to answer the ends of an alembic, in collecting and condensing the vapours together in every place where fountains arise. Varenius, and others, suppose that the water may rise through the pores of the earth, as through capillary tubes, by attraction. But here they show that they are quite unacquainted with what relates to the motion of a fluid through such tubes: for when a capillary tube opens into a cavity at its upper end, or grows larger and larger, so as to cease to be capillary at that end, the water will not ascend through that tube into the cavity, or beyond where the tube is capillary; because that part of the periphery of the cavity, which is partly above the surface of the water, and partly below it, is not of the capillary kind. Nay, if the cavity is continually supplied with water, it will be attracted into the capillary tube, and run down it as through a funnel, if the lower end is immersed in the same fluid, as in this case it is supposed to be.

It has been a generally received opinion, and much exposed by Mariotte, a diligent observer of nature, that the rise of springs is owing to the rains and melted snow. According to him, the rain-water which falls upon the hills and mountains, penetrating the surface, meets with clay or rocks contiguous to each other; along which it runs, without being able to penetrate them, till, having descended to the bottom of the mountain, or to a considerable distance from the top, it breaks out of the ground, and forms springs.

In order to examine this opinion, Mr. Perrault, De la Hire, and Sideleau, endeavoured to make an estimate of the quantity of rain and snow that falls in the space of a year, with the view of ascertaining whether it would be sufficient to afford a quantity of water equal to that which is annually discharged into the sea by the rivers. The result of their inquiries was, that the quantity of rain and snow which fell in a year into a cylindrical vessel would, if secured from evaporating, fill it to the height of about nineteen inches. This quantity, Sideleau showed, was not sufficient to supply the rivers; for those of England, Ireland, and Spain, discharge a greater quantity of water annually, than the rain, according to that experiment, is able to supply. Another observation was made by them at the same time, viz., that the quantity of water raised in vapour, one year with another, amounted to about thirty-two inches, which is thirteen more than falls in rain; a plain indication that the water of fountains is not supplied by rain and melted snow.

Thus the true cause of the origin of fountains remained undiscovered, till Dr. Halley, in making his celestial observations upon the tops of the mountains at St. Helena, about eight hundred yards above the level of the sea, found, that the quantity of vapour which fell there, even when the sky was clear, was so great, that it very much impeded his observations, by covering his glasses with water every half-quarter of an hour; and he attempted to determine by experiment the quantity of vapour exhaled from the surface of the sea, as far as it rises from heat, in order to try whether that might be a sufficient supply for the water continually discharged by fountains. The process of his experiment was as follows. He took a vessel of water saluted to the same degree with that of sea water, in which he placed a thermometer; and by means of a pan of coals brought the water to the same degree of heat which is observed to be that of the air in our hottest summer; he then fixed the vessel of water with the thermometer in it to one end of a pair of scales, and exactly counterpoised it with weights on the other. At the end of two hours, he found, by the alteration made in the weight of the vessel, that about a sixtieth part of an inch of the depth of the water was gone off in vapour; and therefore, in twelve hours, one tenth of an inch would have gone off. Now, this accurate observer allows the Mediterranean sea to be forty degrees long, and four broad, the broader parts compensating for the narrower, so that its whole surface is one hundred and sixty square degrees; which, according to the experiment, must yield at least 5,280,000,000 tons of water. In this account no regard is had to the wind and the agitation of the surface of the sea, both which undoubtedly promote the evaporation. It now remained to compare this quantity of water with that which is daily conveyed into the same sea by the rivers. The only mode of proceeding was to compare them with some known river, and accordingly he takes his computation from the river Thames; and, to avoid all objections, makes allowances, probably greater than what were absolutely necessary.

The Mediterranean receives the following considerable rivers, viz., the Ebro, the Rhone, the Tiber, the Po, the Danube, the Niester, the Borysthenes, the Tanais, and the Nile. Each of these he supposes to bring down ten times as much water as the Thames, and he thus makes an allowance for smaller rivers which fall into the same sea. The Thames, then, he finds by measurement, to discharge about 20,300,000 tons of water a-day. If, therefore, the above nine rivers yield ten times as much water as the Thames, it will follow, that all of them together yield but 1827 millions of tons in a day, which is little more than one-third of what is proved to be raised in vapour out of the Mediterranean in the same time. Here, therefore, we have a source abundantly sufficient for the supply of fountains.

Now, having found that the vapour exhaled from the sea is a sufficient supply for the fountains, he proceeds, in the next place, to consider the manner in which they are raised, and how they are condensed into water again, and conveyed to the source of springs. He considers, that if an atom of water expanded into a shell or bubble, so as to be ten times as large in diameter, as when it was water, that atom would become specifically lighter than air; and therefore would rise so long as the warmth which first separated it from the surface of the water should continue to distend it to the same degree; and consequently, that vapours may be raised from the surface of the sea in that manner, till they arrive at a certain height in the atmosphere, at which they find air of equal specific gravity with themselves. Here they will float, till, being condensed by cold, they become specifically heavier than the air, and fall down in dew; or, being driven by the winds against the sides of mountains (many of which far surpass the usual height to which the vapours would of themselves ascend,) are compelled by the stream of the air to mount up with it to the tops of them; where, being condensed into water, they presently precipitate, and gleaming down by the crenellations of the stones, part of them enters into the caverns of the hills; which being once filled, all the overplus of water that comes thither, runs over by the lowest place, and breaking out by the sides of the hills, forms single springs. Many of these running down by the valleys between the ridges of the hills, and coming to unite, form little rivulets or brooks; many of these again meeting in one common valley, and gaining the plain ground, being grown less rapid, become a river; and many of these being united in one common channel, make such streams as the Rhine and the Danube; which latter, he observes, one would hardly think to be a collection of water condensed out of vapour, unless we consider how vast a tract of ground that river drains, and that it is the sum of all those springs which break out on the south side of the Carpathian mountains, and on the north side of the immense ridge of the Alps, which is one continued chain of mountains from Switzerland to the Black Sea.

Thus one part of the vapours which are blown on the land is returned by the rivers into the sea from whence it came. Another part falls into the sea before it reaches the land; and this is the reason why the rivers do not return so much water into the Mediterranean as is raised in vapour. A third part falls on the low lands, where it affords nourishment to plants; yet it does not rest there, but is again exhaled in vapour by the action of the sun, and is either carried by the winds to the sea to fall in rain or dew there, or else to the mountains to become the sources of springs.

It is not however to be supposed that all fountains can be referred to one and the same cause. Some proceed from rain and melted snow, which, subsiding through the surface of the earth, makes its way into certain cavities, and thence issues out in the form of springs; because the waters of several are found to increase and diminish in proportion to the rain which falls. Others, again, especially such as are salt, and spring near the sea-shore, owe their origin to seawater percolated through the earth; and some to both these causes; though without doubt most of them, and especially such as spring near the tops of high mountains, receive their waters from vapours, as before explained.

This reasoning of Dr. Halley's is confirmed by more recent observations and discoveries. It is now found, that though water is a tolerable conductor of the electric fluid, dry earth is an electric *per se*, consequently the dry land must always be in an electrified state, compared with the ocean. It is also well known, that such bodies as are in an electrified state, whether *plus* or *minus*, will attract vapour, or other light substances that come near them. Hence the vapours that are raised from the ocean must necessarily have a tendency to approach the land in great quantity, even without the assistance of the wind, though this last must undoubtedly contribute greatly towards the same purpose, as Dr. Halley justly observes. In like manner, the higher grounds are always in a more electrified state than the lower ones; and hence the vapours having once left the ocean and approached the shore, are attracted by the high mountains; of which Mr. Pennant gives an instance in Snowdon. Hence we may see the reason why springs are so common in the neighbourhood of mountains, they being so advantageously formed in every respect for collecting and condensing the vapours into water.

The heat of springs is generally the same with the mean temperature of the atmosphere. The mean temperature of the south of England is $48^\circ$; in Scotland, near Edinburgh, it is $45^\circ$; in the north of Ireland it is $48^\circ$, and on the south coast about $51^\circ$. At Upsala, in Sweden, it is $43^\circ$, and in Paris $53^\circ$. According to accurate experiments made by eminent philosophers, the heat of the springs in these different countries corresponds with the medium temperature. We have not heard that similar experiments have been made in other countries, or we should have been careful to collect them. We do not however doubt but they have been made in most countries of Europe; yet we suspect little attention has been paid to this subject within the tropical regions.

Though this coincidence of the heat of springs with the mean temperature of the climate where they flow, seems to be a general fact, yet it admits of many exceptions. In various parts of the world there are springs which not only exceed the mean temperature, but even the strongest meridian heat ever known in the torrid regions. The following table will give a distinct notion of the degrees of heat which different springs have been found to possess, according to the experiments of philosophers. It is necessary to remark that experiments made upon the same springs, by different persons, vary a little from one another, which may be owing to many accidents easily accounted for. Where this is the case, we shall mention both the lowest and highest degree of heat which has been ascribed to the same spring, according to Fahrenheit's thermometer.

| Places | Springs | Highest degree of heat | Lowest degree of heat | |-----------------|--------------------------|------------------------|-----------------------| | Bristol | St. Vincent's or the hot well | 84 | 76 | | Buxton | Gentleman's bath | 82 | | | Matlock | | 69 | | | Bath | King's bath | 119 | 113 | | Aix-la-Chapelle | | 146 | 136 | | Barege | | 122 | | | Pisa | | 104 | | | Caroline baths in Bohemia | Prudel or furious | 165 | | | Iceland | Geyser | 212 | |

In cold countries where congelation takes place, the heat of the earth is considerably above the freezing point, and continues so through the whole year. From experiments that have been made in mines and deep pits, it appears that this heat is uniform and stationary at a certain depth. But as the heat of these springs far exceeds the common heat of the internal parts of the earth, it must be occasioned by causes peculiar to certain places; but what these causes are, it is no easy matter to determine. We are indeed certain that hot springs receive their heat from some subterranean cause; but it is a matter of difficulty to investigate how this heat is produced and preserved. Theories have however been formed on this subject. The subterranean heat has been ascribed to the electrical fluid, and to a great body of fire in the centre of the earth; but we suspect that the nature of the electrical fluid and its effects are not sufficiently understood. As to the supposition that the heat of springs is owing to a central fire, it is too hypothetical to require any refutation. From what then does this heat originate, and whence is the fuel which has produced it for so many ages? To enable us to answer these questions with precision, more information is necessary than we have hitherto obtained respecting the structure of the internal parts of the earth. It is peculiarly requisite that we should be made acquainted with the fossils which are most common in those places where hot springs abound. We should then perhaps discover that hot springs always pass through bodies of a combustible nature. It is well known to chemists, that when water is mixed with vitriolic acid, a degree of heat is produced superior to that of boiling water. It is also an established fact, that when water meets with pyrites, that is, a mixture of sulphur and iron, a violent inflammation takes place. If therefore we could prove that these materials exist in the strata from which hot springs are derived, we should be enabled to give a satisfactory account of this curious phenomenon. As some apology for this supposition, we may add, that most of the hot springs mentioned above, have been found by analysis to be impregnated with sulphur, and some of them with iron. It must however be acknowledged, that the hot springs of Iceland, which are $212^\circ$, the heat of boiling water, according to an accurate analysis of their contents by the ingenious Dr. Black, were neither found to contain iron nor sulphur. It will be necessary that we should wait with patience, and continue to collect facts, till the sciences of chemistry and mineralogy shall be so far advanced as to enable us to form a permanent theory on this subject.

Springs are of different kinds. Some are perennial, or continue to flow during the whole year; others flow only during the rainy season; some ebb and flow. At Torbay there is one of this kind, which ebbs and flows five or six inches every hour. There is another near Coriso in Italy, which ebbed and flowed three times a day in the time of Pliny, and continues to do so still. A spring near Henley SPR sometimes flows for two years together, and then dries up for an equal period.

in Mechanics, denotes a thin piece of tempered steel, or other elastic substance, which, being wound up, serves to put machines in motion by its elasticity, or endeavours to unbend itself. Such is the spring of a watch, clock, or the like.

Ver, in cosmography, denotes one of the seasons of the year; commencing, in the northern parts of the world, on the day when the sun enters the first degree of Aries, which is about the 10th day of March, and ending when the sun leaves Gemini; or, more strictly and generally, the spring begins on the day when the distance of the sun's meridian altitude from the zenith, being on the increase, is at a medium between the greatest and least. The end of the spring coincides with the beginning of summer.