media, without increasing their temperature; and that a cloudless sky is essential for radiation to ensue, and that it will ensue with the greatest rapidity from rough surfaces; let us now venture upon the application of these facts to the phenomenon of "ground-ice."

The beds of the rivers or streams already mentioned, consist of rugged rocks and stones; these contain a certain degree of heat, and part with it, not by conduction, not by convection to the water, but by direct radiation through it to the cloudless sky; thus losing heat, they quickly cool the water in their immediate contact, and suddenly freeze it in films upon their surfaces; which films remain so long as radiation and the cloudless sky continue, but radiation ceases when clouds appear.

The solid surfaces then communicate sensible heat to the ice, or the clouds may send forth radiant heat downwards through the water to the ice; which unlike common ice, is not smooth and glassy, but rough and porous; therefore capable of converting radiant into sensible heat, in a degree sufficient to cause thawing to take place; and therefore the detachment of part of the ice from the solid rocks and stones, and its floating upon the surface of the water; it there opposes all further radiation from below, and by actual contact, cools the water until a perfect sheet of ice is formed as usual.

Let us now turn to the contemplation and investigation of another beautiful attribute of Winter, that displays the wisdom and power of God:

"Great things doeth He which we cannot comprehend; for He saith to the snow, be thou on the earth."

"By his commandment he maketh the snow to fall apace; as birds flying he scattereth the snow; and the falling down thereof is as the lighting of grasshoppers, the eye marvelleth at the beauty of the whiteness thereof; and the heart is astonished at the raining of it."

Snow thus eloquently and impressively described, very probably depends for its formation upon the gradual congelation of watery vapour in clouds amid the higher and colder regions of the air, where its capacity for heat is increased by expansion; the water thus becoming solidified, loses the support of the air, and the newly-formed crystalline snow-flakes, in obeying the attraction of gravitation, descend, and cover the earth with a mantle of spotless white.

This perfectly conceals the lowly remnants of vegetation from our sight, but we have reason to be grateful for its presence; the chemist discovers that snow is solid water in loosely compacted crystalline flakes, the beautiful form of which may be readily determined by catching them on a piece of black cloth, or on the top of a black hat, and immediately examining them with a high magnifier; they will be found to present the regular figures as shown in the engraving; and these may be regarded as the framework or skeleton of the solid six-sided prism into which water is more compactly frozen to constitute hail.

Like more massive ice, snow is a bad conductor of cold; it therefore protects seeds, bulbs, and roots from the chilling winds that sweep over its surface, as effectually as the shield of ice protects the beings of the wave; in fact, vegetable productions are thus preserved from intense cold by snow flakes, as they would be by a fleece of wool.

Thus in the beautiful and impressive language of Scripture," He giveth snow like wool."

This passage refers to the similarity between flakes of snow and fleeces of wool, in whiteness and lightness; and also to their similarity in power of preserving warmth around the bodies which they shield and clothe.

Snow is a great. preservative against the effects of cold; wheat will continue growing beneath deep snow, whilst every blade would be killed by hard frost without snow ;-beneath the surface the temperature of

snow is very little colder than 32 degrees, whilst the air above is frequently 20 or 15 degrees.

If a piece of ground be left covered with snow, and another contiguous piece of ground be swept clean, after a day or two, upon digging both, it will be found that the frost has penetrated very considerably below the surface of the piece unprotected by the snow; indeed it is recorded, in illustration of this protecting power of snow, that in "Holland, during the cold winter of 1776, the surface of the earth was frozen to the depth of twenty-one inches on a spot of garden ground, kept free from snow, but only to nine inches on an adjacent spot, covered with four inches of snow."

"In the northern regions, snow lying twelve feet deep during Winter, preserves the vegetables which are destined to adorn the Summer, although the cold may be many degrees below zero."

The Esquimaux have learnt to convert snow into building materials, by which means they can raise a dwelling for their families in a few hours; a dwelling which, from the purity of the material of which it is composed, the elegance of its construction, and the translucency of its walls, gives it an appearance superior to a marble building.

Having selected a spot where the snow is sufficiently compact, they commence by tracing out a circle of from eight to fifteen feet in diameter, proportioned to the number of occupants the hut is to contain.

They then prepare a number of oblong slabs of snow,

of six or seven inches thick, and about two feet in length, which are tenacious enough to admit of being moved without breaking, or even losing the sharpness of their angles.

These slabs, which have a slight degree of curvature corresponding with the circular foundation, are piled upon each other exactly like courses of hewn stone, and care is taken to make them fit closely to each other, by running a knife adroitly along the under part and sides, and to cut them so as to give the wall a slight inclination inwards.

Tier after tier is thus laid on by one man standing within the wall, who is supplied with material by one or more assistants from without.

But for the better convenience of transmitting this supply to the workman, when the wall has attained a height of five or six feet, a hole is cut on the south side close to the ground.

Thus they continue labouring till they have brought the sides nearly to meet in a perfect and well-constructed dome, sometimes nine or ten feet high in the centre; and this they take particular care in finishing, by fitting the last block or key-stone very nicely in the centre, dropping it into its place from the outside, though it is still done by the man within; the people outside are in the mean time occupied in throwing up snow with the snow-shovel, and in stuffing in little wedges of snow where holes have been accidentally left.

The builder next proceeds to let himself out, by en