tives of these Arctic Regions, is the oily nature of their diet. Here, however, we find that Providence had another end in view in affording to the inhabitants of these countries so large a supply of fat and oil as that which is obtained from several of the cetaceous tribes which frequent their stormy seas. Nor is this an end less essential to the preservation of human life. There, where no other fuel could be had, and where, without fire, the race of men must soon have been extinguished, were fixed these living reservoirs of combustible fluid, which it only needed the exercise of reason, of perseverance, and of ingenuity, to bring within the power of the human family, by which a provision has been made for their wants, infinitely better suited to the circumstances of their lot, in their inhospitable deserts, than any other description of fuel that could be named. Coals would have required the assistance of large beasts of burden, and the convenience of roads to remove them from the pits to the places where they were to be consumed, and the very nature of the climate, rendered both of these equally impossible to be obtained. Wood, even supposing it could have been had, would have been almost as inconvenient; but the seals are generally to be met with readily, and killed with ease, affording, for a moderate degree of labour and of ingenuity, not only an ample banquet, but a very considerable quantity of the best oil, to feed the flame on which their food, their drink, and their comfort mainly depend. How can we contemplate such facts as these, without admiring the goodness and the care of that God who has so liberally furnished the means of subsistence, even in this wild, desolate, and barren country! G. J. C. D.

TENTH WEEK-WEDNESDAY.

I. FROST.-PROVISION FOR CAUSING ICE TO FLOAT ON THE

SURFACE.

WITHOUT heat, every thing would be solid; the true way, therefore, of viewing liquids, is to consider them as solids in a melted state. Bodies melt at different temperatures, according to their capacity of receiving heat, and to the nature of the action which this subtle principle has on their particles. Thus, it requires one degree of intensity to melt stone, another to melt iron, another to melt lead, and another still to melt ice. In this view, ice may be considered as the natural state of the element, and water to be nothing else than ice rendered liquid, like other substances, by heat. When the short continuance of the sun above the horizon in winter, and his oblique rays, have greatly diminished the force of his influence, he is no longer able to preserve water in a state of fusion, and then the process of crystalization takes place, and ice is formed. But there is a remarkable difference between ice and other solid bodies, in the laws regulating its passage from a liquid to a crystalized state, which manifests beneficent intention.

Take water in its common state, and observe what occurs in reference to heat. It is the property of water, in common with other liquids, to communicate heat not so much by conduction, as it is called,—that is, by transmitting the temperature from particle to particle,-as by a motion among the particles themselves. Liquids, like solids, expand by heat and contract by cold. When heat, therefore, is applied to the bottom of a vessel, the expansion diminishes the specific gravity of the particles affected by it, and they rise to the surface, making place for the colder and heavier particles, which again are heated in their turn, and ascend; and thus the process

proceeds, till the whole liquid is of equal temperature. In cooling, the opposite process takes place; the particles, as they become colder at the surface, subside, while others, of higher temperature, supply their place, and this interchange and mixture goes on till the whole body of the liquid becomes as cold as the surface. This remarkable property we have already noticed in speaking of the effects of the waters of the ocean in mitigating the temperature of different climates. Let us now see what would be the consequence if the same laws were to hold without limitation or exception. The cooled particles constantly descending, in virtue of their relative specific gravity, would, when the freezing point was reached, suddenly convert lakes and rivers, and the bed of the ocean itself, into a solid mass of ice, the congelation beginning at the bottom, and quickly spreading upward. Nor, when our deep waters were once frozen, would there be any natural means in existence by which they could be thawed to the bottom, because, the heated particles being the lightest, would constantly float at the top, and the warmth could only be diffused, as it is in solids, by the slower and less equable means of conduction. The experiment has been made, and water has been caused to boil by the application of heat to a vessel partly filled with ice, without thawing the congealed cake below.

Now, this would be attended with many disadvantages. The utility of our seas and lakes, in our own and similar latitudes, would be destroyed as means of commerce and of subsistence; and that element which, by its equal and mild temperature, contributes so essentially to the salubrity of all climates, from the tropics to the polar regions, would serve only to chill the atmosphere, and render even our temperate climates inhospitable.

What is worthy of serious attention, is the modification of the law by which this inconvenience is provided against. Water continues to contract by the application of cold, till it approaches the freezing point; but

here a most remarkable deviation takes place. When it has cooled down to 40°, instead of continuing to contract, it suddenly begins to expand, and it proceeds in this new course, till, at 32°, it becomes ice. The fluid is, therefore, at its greatest density, when its temperature is just 8° above the freezing point; and hence the bottoms of our seas and lakes will be generally found, in winter, not to exceed this extent of coldness.* The coldest water, as it approaches the freezing point, rises to the surface. There the ice is formed, exposed to the first return of a more genial temperature, and ready to dissolve, with the earliest influences of a warmer sun.

Another remarkable circumstance, which secures the floating of ice on the surface of the water, is, that in the very act of freezing, a further expansion takes place. By this operation, the specific gravity of ice becomes less than that of water under any circumstances, and it is thus prevented from sinking to the bottom. Did no expansion take place in the process of congelation, ice would continue to float only so long as the water on the surface of which it was formed remained below the temperature of 40°. If the temperature happened to be raised above this point, it would immediately sink, and be overwhelmed, giving rise to various inconveniences, though not of so formidable a nature as those already alluded to.

It is not easy for the most sceptical to avoid the conclusion, that the marked and salutary deviation in this case, from the law by which matter is expanded by heat and contracted by cold, is an arrangement of an intelligent and beneficent Creator. The general rule is followed down to the point where it ceases to be beneficial; and then, by a sudden and surprising change, the very opposite rule takes place, by which disastrous effects are prevented, and various important advantages are se

* It seems unnecessary to notice some remarkable facts which have lately attracted public attention, that appear somewhat to modify this conclusion, ice having been found formed at the bottom of some deep lakes.

cured. Where could we look for a clearer or more satisfactory proof of wise contrivance?

“We do not know," says Whewell, “how far these laws of expansion are connected with, and depend on, more remote and general properties of this fluid, or of all fluids. But we have no reason to believe, that by whatever means they operate, they are not laws selected from among other laws which might exist, as, in fact, for other fluids, other laws do exist. We have all the evidence, which the most remarkable furtherance of important purposes can give us, that they are selected, and selected with a beneficial design."

TENTH WEEK-THURSDAY.

II. FROST.-THE EXPANSIVE AND NON-CONDUCTING POWER OF ICE.

OUR attention was yesterday directed to some of the peculiar provisions by which the freezing of water is so modified, as to prevent the fatal effects that would ensue were the general law of expansion and contraction which regulates heated bodies, to operate without being arrested and altered. But there are one or two other beneficial operations of frost in our climate, which must not be passed without notice.

The expansive power of water, when passing into ice, has already been stated. This power operates with great force, as has been ascertained by experiment. A familiar instance occurs in the bursting of bottles filled with water or other liquids, when corked up and exposed to its influence. The same power affects the soil, when saturated with moisture, heaving up and separating the particles of earth and gravel. This sometimes acts disadvantageously, by throwing out the plants of young

* Bridgewater Treatise, p. 85.