Yes if a mixture of oxygen and hydrogen gases, in proper proportion, be fired, the inflammation will unite the bases of the two gases, without separating the whole of their caloric, and water will be the product*.

Is there any reason to suppose that water is thus formed in any of the great operations of nature?

Yes: : claps of thunder appear to be owing to a sudden combustion of hydrogen gas and vital air; for these aërial explosions are often succeeded by an immediate torrent of rain‡.

How is the atmosphere furnished with this hydrogen gas?

Hydrogen being a component part of vegetables, it is given out in great abundance during their putrefaction, and forming a light gas it passes through the surrounding atmosphere without mixing with it§.

What is the specific gravity of water?

* In Lavoisier's Elements of Chymistry, a copper plate print of an excellent apparatus for composin water may be seen, with a full and satisfactory descript on of the method of making use of it.

M. Biot has succeeded in forming water from hydrogen and oxygen, by compression only, independently of the electric spark. The compression, by bringin the particies of gas into intimate union, makes them throw out heat sufficient to set them on fire; and the product of the combustion is water.

It here occurs, that the affinity of hydrogen for oxygen may be exemplified by the large portion of oxygen which all combustible bodies containing much hydrogen require in combustion; affording water as the product. Thus, one pound of highly rectified spirits of wine on being burnt will produce more than its own weight of water. See Additional Notes, No. xvi. + This combustion is probably occasioned by lightning.

The aurora borealis is probably owing to the existence of a stratum of hydrogen gas in the higher regions of the atmosphere, which being lighter than atmospheric air would keep that situation till ignited by electricity. The vulgar have had strange conceits about this curious phænomenon of

Hydrogen gas is only one thirteenth of the weight of atmospheric air, and occupies a space fifteen hundred times greater than it possessed in its aqueous combination.

The ignis fatuus, or will-o-wisp, it is supposed, has its origin from this decomposition of decayed vegetables.

Thus heat evolved from some fermenting mass
Expands the kindling atoms into gas.

DARWIN.

Dr. Shaw, in his Travels in Palestine, has given a curious account of an ignis fatuus which they observed there. See Shaw's Travelɛ.

A wine pint measure of water weighs one pound*, a cubic foot of water weighs about 1000 ounces, or 62 lbs. avoirdupois. It is 816 times heavier than atmospheric airt.

What change does water undergo in order to be converted into ice?

When the cold atmosphere has deprived water of its caloric of fluidity, crystallization takes place, and it becomes icet. What do you mean by crystallization?

By crystallization is understood the concretion of certain substances into regular forms, occasioned by the loss of a portion of their caloric.

To what substances is the term usually applied?

The term is generally applied to bodies of the saline kind, and

* It is necessary for the student to bear in mind the specific gravity of water, because it is always made unity in the measure of the specific gravity of every other substance.

This estimate is agreeably to the last experiments made by Sir George Shuckburgh, when the barometer is at 30 inches, and the thermometer beEween 50 and 60°.

Water in freezing crystallizes in filaments which are uniformly joined at an angle of 60 degrees.

It has been said that water may be purified from the putridity which may be contained in it by freezing; and that in such water the portion which freezes is pure, while that which remains fluid is contaminated with noxious matter. Dr. Lamb on Constitutional Diseases.

It is owing to the expansion of water in freezing that rocks and trees are often split during intense frosts. According to the calculations of the Florentine academicians, a spherule of water, only one inch in diameter, expands with a force in freezing superior to the resistance of 13 tons weight. Phil. Mag. vol. vii. 69.

This property of water is taken advantage of in splitting slate. At Colly Western the slate is dug from the quarries in large blocks, which are placed in an opposite direction to what they had in the quarry, and the rain is allowed to fall upon them; it penetrates the fissures of the slate, and the first sharp frost freezes the water, which, expanding with its usual force, splits the slate into thin layers.

It was necessary for the preservation of the world, that water should in this instance be subjected to a law different from that of other subftances which change from fluid to solid. For an account of this important deviation from a general law of nature, see Note Chap. 4th, page 76.

It may be remarked, that though fresh water freezes when reduced to the temperature of 32°, sea water does not freeze till cooled down to 28.5°. Was not this designed by nature to keep the ocean open at all seasons, that there might be no impediment to that general intercourse among nations which tends so much to promote their civilization and refinement?

For this the ship, in floating balance held,

By earth attracted and by seas repell'd;

Directs her devious track through climes unknown,
That leads to every shore and every zone.

FALCONER,

to their separation, in regular and peculiar figures, from the water in which they were dissolved*.

You have said that water is composed of two solid substances; de you thence imagine that it is naturally solid?

Yes: for underneath the poles water is eternally solid; it is similar to the hardest rocks†, and may be formed by the chisel of the statuary, like stone.

Crystallization is a kind of precipitation which the salt as it separates from the solvent assumes peculiar determinate forms. Mr. Smithson has shown that crystallization cannot take place while solution subsists, and that the only requisite for this operation is a freedom of motion in the masses which tend to unite. Phil. Trans. for 1803, page 27.

There happen cracks at certain times in the ice mountain of Switzerland, which have shown the great thickness of the ice; some of these cracks have measured 300 or 400 ells deep. Near Hudson's Bay there are islands of ice which are immersed above 100 fathoms beneath the surface of the sea, and which measure three or four miles in chicumference. Phil. Trans.

"There can be no doubt but that the quantity of ice at the north pole is the principal source of the coldness of our winters, and that it is brought hither by the regions of air blowing from the north." Dr. Darwin.

Where, for relentless months, continual night
Holds o'er the glittering waste her starry reign.

THOMSON.

The ice at each pole of the earth forms an immense cupola, the arch of which extends some thousand miles over the continents; the thickness of which is several hundred feet beyond the 60th degree of latitude. Naviga tors have assigned to detached masses, which are met with floating at sea, an elevation of from 1500 to 180c feet. See Ellis's Voyage to Hudson's Bay.

There can be no doubt but that the thickness of these cupolas of ice is much greater nearer the poles; for astronomy sometimes presents in the heavens so vast an image of them, that the rotundity of the earth seems to be considerably affected thereby. Captain Cook could never approach nearer the south pole, where there is no land, than the 70th degree of latitude; that is, no nearer than 1500 miles; though he had coasted round it for a whole summer; and it was only under favour of a bay that he was permitted to advance even so far. St. Pierre's Studies,, vol. i. 129-132. From a late memoir by Mons. Perron, there is reason to believe that these mountains of ice at the poles, which have hitherto impeded the progress of European navigators, have been detached from the depths of the sea to float at the surface. All the results of observations made by him and other navigators concur in proving that the temperature of the sea decreases according to the depth; and that the deepest gulfs of the sea are continually covered with ice, even under the equator. A translation of this interesting memoir may be found in the 21st volume of the Philosophical Magazine.

"It is related that at the whimsical marriage of Prince Gallitzin, in 1739, the Russians applied ice to the same purposes as stone. A house consisting of two apartments was built with large blocks of ice; the furniture of the rooms, even the nuptial bed, was made with ice; and the icy cannon, which were fired in honour of the day, performed their office more than once without bursting." Bishop Watson.-See Additional Notes, No. xvii.

Is this great solidity of the ice at the poles, owing to its being frozen in such large masses?

No: it is owing to its being so much divested of caloric*; for in very cold countries ice may be ground so fine as to be blown away by the wind, and will still be ice.

Is ice the only instance of water existing in a state of solidity?

No: water becomes still more solid in mortars and cements, having parted with more of its caloric in that combination than it does in the act of freezingt.

What other instances are there of water taking a solid form?

Water is combined in a state of solidity in marble, in crystals, in spars, in gems, and in all alkaline and earthy salts; to all of which substances it imparts hardness, and to most of them transparency‡.

In the most northern part of the Russian territory, the cold is sometimes sufficient to freeze mercury. It is so intense in some seasons that the poor inhabitants cannot venture out of their miserable huts but at the hazard of their lives.

There, through the prison of unbounded wilds,
Barr'd by the hand of Nature from escape,
Wide roams the Russian exile. Nought around
Strikes his sad eye, but deserts lost in snow,
And heavy-loaded groves, and solid floods,
That stretch athwart the solitary vast
Their icy horrors to the frozen main.

THOMSON.

* We need not look for any cause for the conversion of water into ice, but the loss of its caloric; the situation or the season of the year has no influence; for "in the Grotto of Besançon, water is frozen during the heats of summer. In this singular place the variation of the thermometer between winter and summer is very inconsiderable." Madame de Genlis.

Though water be converted to ice by the loss of caloric, there is reason to suppose that ice, notwithstanding, contains more caloric than was disengaged between the state of vapour and that of congelation. See Berthollett's Statics, vol. i. 134.

I have been informed by some intelligent workers in iron and steel, that they have great difficulty in making tools hard enough to cut ice in very cold winters; and that in such seasons the workmen are under the necessity of having them very frequently repaired.

†Though water takes a solid form in its various combinations, such as with lime, saline crystals, &c. we know of no method of compressing it when in a fluid state. The Florentine academicians filled a globe of gold perfectly full of water, and submitted it to a very powerful press; but could not perceive that they were able to make it occupy less space than it did at first. They gave it such a degree of pressure, that at length the water exuded through the pores of the metal.

Most stones and salts lose their solidity and transparency by being deprived even of a part only of the water which they contained, and generally become pulverulent. It is by a combination with water that the gases are rendered liquid substances, and that some liquids acquire the property of

What are the general and more obvious advantages which we de rive from water?

Water is a necessary beverage for man and other animals; is perpetually used as a solvent * for a great variety of solid bodiest; acts an important part in conveying nourishment to the vegetable world, and giving salubrity to the atmospherical regionst; and lastly, by its accumulation in the oceans, affords a ready communication with distant countries;-the whole of which evidently teaches how provident the great AUTHOR of nature has been in his attentions to the comforts and conveniencies, as well as to the wants of his numerous creatures.

becoming fixed. This may be satisfactorily shown by boiling a few copper filings in concentrated sulphuric acid, with a small portion of nitric acid, till the copper is dissolved; then adding water, and leaving the mixture to cool gradually; when beautiful crystals of blue vitriol will be found, as hard as some minerals. It is the water which gives them their solidity;

"That chief ingredient in Heaven's various works,
Whose flexile genius sparkles in the gem,
Grows firm in oak, and fugitive in wine.”

ARMSTRONG.

If water be thrown on quick-lime, it will be retained by it with such force that nothing less than an intense red heat will separate it. In its combination with lime it becomes much more solid than when in the state of ice, which may be proved by direct experiment. Calcined plaster of Paris, in a pulverulent state, becomes quickly solid by mixing it with water. Saussure has proved that alumine, when mixed with water, retains a tenth of its weight of that fluid at a heat which will melt iron.

It should be remembered, that all bodies which are soluble in water, form, during their solution, a chymical combination with the water, and cannot be separated therefrom by any mechanical means. This is not the case with aqueous mixtures.

Water is not only employed as a solvent for many solid substances, but has important uses in a variety of compounds. Besides imparting solidity to the classes of salts, it gives energy to the action of many of the acids, and is even necessary in their formation. Muriatic acid gas and nitrous acid gas are condensed so as to form muriatic and nitric acid only by its

means.

See Note, Chap. ii. page 80.

Some late experiments of Mr. Harrop's, related in the fifth volume of the Philosophical Journal, render it probable that the ocean and other large bodies of water may have been designed by nature as reservoirs for supplying an increased population with the oxygen necessary for its consumption, and for producing a regular renovation of the atmosphere. The immense quantities of marine productions found at very great heights above the present level of the sea, seem to indicate that there has been a prodigious recession of the ocean. While water was conceived to be a simple and indestructible substance, innumerable conjectures were afloat as to the channels which had been found for such an immense body of water. The new chymical doctrines have afforded us a clue by which to unravel this mystery, and fresh motives for admiring the exquisite contrivance of the great Author of all things.