With the single exception of water, all sub-stances in nature expand or hecome larger when heated, and contract and hecome smaller when cooled. A church-steeple is higher in summer than in winter. Metals show this action plainer than other hodies ; and, as a consequence, Soutliwark Bridge, (London,) being constructed entirely of iron, is shorter in cold weather than in warm. If the sun sliiues hut for a few minutes on the great iron tubular bridge, near Bangor, its length is visibly increased. A cannon ball which would pass through a certain ring while cold, would not do so after being placed in boiling water. The tires of wheels, previously to their being fixed, are made hot, in order that, by their contraction when cold, they may bind the. work the firmer. The least alteration in the temperature of any material produces a corresponding alteration in the size of it, but no modification in its weight. By one of those wise provisions of nature with which the universe may be illustrated, water, as we have just observed, is an exception to this rule of contraction and expansion. From a certain fixed temperature (4'44 C.) it expands either by cooling or heating. The force with which it expands io enormous. It has been calculated that a globe of water, one inch in diameter, expands in freezing with a force superior to the resistance of thirteen and one-half tuns weight. Major Williams attempted to prevent this expansion ; but during the operation, an iron plug which stopped the orifice of the bombshell containing the freezing water, and which was more than two pounds in weight, was projected several hundred feet with great Telocity. A simple experiment to illustrate this fact may easily be tried on any frosty day, by filling a common ginger-beer bottle with water, corking it tightly, and afterwards tying it down. If it now be placed in a situation where the water will freeze, the bottle will be sure to be broken. It is from this cause that pipes which supply town houses with water frequently burst, showing the whereabout by leakage directly a thaw begins. This peculiar property ef water is taken advantage of in splitting slate. At Colley Western, the slate is dug from the quarries in large blocks ; these are placed in an opposite direction to that which they had in the quarry, and the rain is allowed to fall upon them ; it soon penetrates their fissures, and the first sharp frost freezes the water, which, expanding with its usual force, splits the slate into thin layers. With a knowledge of these facts, we can easily understand how it is that a succession of frosts and thaws so completely pulverizes and breaks up the surface soil of the farmer's field. A sharp frost, followed by a rapid thaw, plows a field in a few hours better than hands could do it i n ages. In an agricultural point of view, then, the great utility of this crumbling of the soil is obvious ; by this means a much larger surface of the earth is exposed to the action of the air than it otherwise would be ; and it enables the plants growing upon it to extract those saline materials without which their existence would soon terminate. Much of the cultivated land was originally produced by the action of frost and thaw upon the rocks which are now below the verdant fields. The lapse of time which it takes to break up a certain portion of rock in this way must of course vary according to the original structure of the stone. Some stone buildings have crumbled to dust within the history of the English nation ; while others, erected three thousand years ago, appear the same as ever—such are the Pyramids of Egypt. The preservation in form and shape in stone that is exposed to the atmosphere, depends entirely on climate, and whether its grain be close or open. If the climate be not subject to variations of extreme heat and cold, the stone will be, very lasting if of either nature ; but if, on the contrary, the climate exposes ? the stone to frost and thaw, and the stone is porous, so as to draw in water or rain in contact with it, the destruction of the surface is inevitable ; and thus " the palaces of the proud pass away." Philosophers consider cold, not as an abstract principle, but as an effect produced by the mere absence of heat. Few persons have any idea of the effects produced upon the ordinary substances with which we are surrounded on their being exposed to an extreme degree of cold ; many gases which are only known to exist in an aeriform state in our climate, become first liquids, and then solid substances ; reminding one of the various states in which water is familiar to us, namely, as a vapor, as a liquid, and as a solid. Mercury or quicksilver is always fluid in our country; but in the Arctic regions, it is frequently solidified, and in this state it can be beaten and rolled out into sheets, like tin or silver. It is certain that were it not for the counter-influence and genial warmth produced by the sun's rays, the whole of our world would become a vast sterile waste, for cold would predominate, and solidify everything therein. We cannot conclude this cold subject without repeating an anecdote told by Bishop Watson, who relates 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 rooms, was built with large blocks of ice; the furniture of the apartments, even the nuptial bed, was made with ice, covered with sheets of the same material; and the icy cannon, which were fired in honor of the day, performed their oflice more than once without bursting." This is also noticed by Cowper :— " Thou dirist hew the floods. And ninlte thy marble of the glassy iravc." SEPTIMUS PIESSE
This article was originally published with the title "Frost and Thaw"