The chemist removes the Oxygen, and supplies its place with an equal volume of Chlorine; but this will weigh 2470 parts; it is more than twice the specific gravity of the Air, or decimally thus :-S. G. of Chlorine = = 2.470.

The place of the Chlorine is then supplied with a volume of Carbonic acid, and it will weigh 1500 parts; it therefore is exactly one and a half times heavier than air, or its S. G. is 1.500.

=

Proceeding in this manner with Nitrogen, its volume will not weigh even 1000 parts, but only 972 parts; it is therefore lighter than air, or its S. G. is= 0.972.

Lastly, if the globe be filled with Hydrogen, its volume will not weigh even 972 parts, but only 69 parts; it is therefore lighter than either Nitrogen or Air, or its S. G. is = 0.069; and as Platinum is the heaviest, so is Hydrogen the lightest form of ponderable matter.

Observation, experiment, and analogy, tend to excite our wonder, admiration, and gratitude, regarding the miraculous provision that is made by the Almighty for the protection of His creatures.

How admirably adapted to their purposes are the substances provided for the clothing of animals, and which man strips from them to form garments for his own protection! Animals are preserved from the piercing blasts of winter by clothing which retains nearly the whole of their vital heat; what is its composition?

Almost incredible is the answer of the chemist, namely, that it consists of the ultimate elements of the atmosphere, Nitrogen, Oxygen, Hydrogen, and Carbon-most wonderfully, most mysteriously elaborated under the influence of vitality, protecting and at the same time adorning.

" Clothing which grows from the bodies of animals, in quantity suiting the climate, the season, and reproducible if partially destroyed by accident; in hot climates, the coat of quadrupeds is short and thin, but it thickens with increasing latitudes, and yields soft and abundant fleeces."

"At the poles it is externally shaggy and coarse, internally shorter and fine, as in the skin of the arcticbear;-how defensive is the fur of amphibious animals, the beaver for example;-how abundant and smooth upon birds, as feathers shutting up the heat of their warm blood, and opposing no resistance to the air through which they fly!"

"The birds of very cold regions have plumage almost as bulky as their bodies; and those which live much in the water, have additionally both a defence of oil on the surface of the feathers, and the interstices of the ordinary plumage filled with delicate down, a bad conductor, which abounds particularly on the breast, as it in swimming first meets and divides the cold wave."

"Then there are animals with warm blood which live in the water; for example, the whale, seal, and

X

walrus; but neither hair nor feathers oiled would have been a fit clothing for them; they accordingly derive protection from the cold water, by the enormous amount of blubber or fat which surrounds their bodies; it is a non-conductor."

The bad conducting power of the earth as regards heat and cold, has been already mentioned; and hence in Winter, springs of water never freeze; they become remarkable features in a snow-clad country, the warm liquid water gushing from the earth, and flowing for a considerable distance before the cold air can chill and bind it in icy fetters.

Throughout the Creation everything is admirable, everything is beneficently fitted for its destined purpose; and the more that we learn, the more do we wish to learn, for we soon become sensible of the extreme insignificance of our knowledge, when we compare it with the contents of the mighty volume that is unfolded for our perusal.

"He sendeth forth His word and melteth the snow."

As we discovered the transition of flowing water into solid ice to be a slow and gradual process, so shall we discover that the conversion of solid ice into flowing water is unattended by sudden and abrupt disturbance of physical state, and thus gain another proof of the wisdom and beneficence of The Creator, and of the miraculous order and harmony of His works.

A few experiments of the chemical laboratory will serve as introductory to the extraordinary phenomena

attendant upon the liquifaction or thawing of ice and

snow.

Place a lump of clean dry ice in a basin; carry this into a warm room, at the temperature of 70 degrees for example; the thaw of the ice will commence, and continue ;-immerse the bulb of a thermometer into the water resulting from the thawing or liquifaction; it will indicate 32 degrees;-and will again and again do so, whilst a particle of ice remains; when it vanishes, the water will gradually acquire the temperature of the room.

During the progress of thawing, heat must be entering and unbinding the ice; but, strange to say, it does not confer the slightest temperature, it merely causes liquifaction, or, in other words, the sensible heat of the room combines with the ice to produce liquid water, and is then rendered insensible to the thermometer.

By what term does the chemist denote this extraordinary habitude of heat? He denotes it as combined heat, hidden heat, or more commonly Latent heat; and discovers most important results of its agency throughout the realms of Nature and the provinces of Art.

Select two wide-mouthed bottles, of the same size, and resembling each other in all other respects as nearly as possible; put into one bottle a pound of small pieces of ice at 32 degrees and pour into the other a pound of water at 33 degrees; place a thermometer in each bottle, and carry them both into

a room having a temperature of 47 degrees, and set them side by side, as at page 106; they are thus placed under similar circumstances as regards the heat of the room; and they differ only in the physical nature of their contents, the one holding solid, and the other liquid

water.

Preserve the air of the room undisturbed by draughts, observe the thermometers occasionally, and note the progress made by the contents of the bottles in heating; if the liquid water arrive at 40 degrees in the course of an hour, the ice will not melt into water, and attain the same temperature, until twenty-one hours later.

The heat of the room is uniform all this time, but twenty one times more of it is required in the one case than in the other to produce the thermometric temperature of 40 degrees; or, to place this easily-ascertained, yet extraordinary fact, in another point of view, suppose that, during the twenty-one hours the water received heat, as regularly as during the first hour, namely, 7 degrees, or from 33 to 40 degrees, the whole heat would be expressed by twenty-one times seven, or 147 degrees; the difference between the gain of temperature by the ice and by the water, with equal accessions of heat, is, therefore, 140 degrees; hence 140 degrees become the expression for the amount of thermometric temperature which disappears, which is hidden, or rendered latent during the liquifaction of ice heat enters the ice, rendering it liquid, but does not produce the slightest rise of temperature.