Q. Can any reason be given why bodies, as they are more or less dense, should generally have more or less of power to conduct heat?

A. This, it is supposed, may be connected with their being more or less porous, and the quantity of air they contain: the less air, the more rapidly caloric is conducted; the more air, the less of facility do bodies possess to do this.

Q. Hair, wool, fur, down, are light bodies. Are they good or bad conductors of heat?

A. They are bad conductors of heat.

Q. May not the wisdom and goodness of divine Providence be seen in this fact?

A. It certainly may, and ought to be noticed.

Q. So I thought. But can you distinctly state why? A. In reference, especially, to the covering of animals, and the garments of men. Birds which pass rapidly through the air, or swim on the waters, have their temperature preserved by their thick plumage; most thick where they directly meet the air or water. Animals also, as exposed to the cold, are in this respect mercifully preserved, the wool passing to hair in tropical climates; the hair passing to wool, fur, &c., in frigid zones; the coloured also to white. The comfort of garments made of these, man knows well, in the heat they afford.

Q. Do down, fur, and woollen garments really give heat?

A. Correctly speaking, they do not; but being bad conductors of heat, they prevent its rapid escape from the body. Flannel, for example, does not so much give heat, as it keeps it; that is, prevents its escape; and in very hot weather, flannel, as a bad conductor of heat, keeps it out.

Q. Is the difference which is felt between linen and woollen garments, and when the feet rest on carpeted, wood, and stone floors, connected with this power to conduct or retain heat?

A. It is the linen permits heat more quickly to escape. Stone floors, and especially siliceous slate, rapidly take heat from the body; wood flooring less speedily; and carpeted

But, in truth, the carpet, the flannel, the fur, the wool, &c., are bad conductors of heat, and do not take it from the body. Snow, in winter, serves the same purpose on the surface of the earth; it prevents the heat from escaping, and keeps the cold from so penetrating to the roots of plants, as to destroy vegetation. The snow of winter as much proclaims the divine government, as the warmth of spring, by which all nature teems with new life.

Q. Is the atmosphere a good conductor of heat?

A. No: the pure atmosphere is said to be a perfectly transparent medium, which simply transmits the rays of the

sun to us.

Q. How then does the air become heated?

A. By contact with the earth, which is constantly radiating the heat which it receives.

Q. How is this effected?

A. The stratum of air which immediately covers the surface of the heated earth becomes hot by the contact; this warmth causes it to be specifically lighter than the portion of air immediately above; and it ascends, leaving the colder to take its place. This lower stratum is soon heated ; and in its turn ascends, to be succeeded by that which is colder : by a series of these changes we feel a heated atmosphere. During a hot summer day, this ascent, the radiation of caloric in the vapour that is taken up with it, becomes visible in the glassy, liquid-like, tremulous appearances on the earth's surface.

Q. Why is the air so warm in valleys, and between hills? A. First, because in these situations it is heated by a greater extent of the earth's surface, from which caloric is radiated; and, secondly, the heat in those situations is not so rapidly carried off by winds.

Q. But if the heated air ascends, why should it be cold on the top of mountains?

A. Because the atmosphere diminishes in density as it increases in height. When the heated air has reached the stratum of its own weight, it will ascend no higher; and the lower parts of the atmosphere are never all so heated

Q. Is there any thing that should especially arrest the attention of man, in the fact that the atmosphere is a bad conductor of heat?

A. There is if the air conducted heat as some bodies do, in many parts of the earth man could not exist; and in all, his life would be placed in jeopardy by every change of temperature.

THE TRUE CHRISTIAN.

A REAL Christian, whose heart is thoroughly imbued with the love and fear of God, can no more enjoy the amusements of the world, than a philosopher can be refreshed with the diversions of the vulgar, or a man be amused with the recreations of a child.-Mrs. Hannah More.

THE ADVANTAGES OF PIETY.

IN the solitude of grief, a pious man has the advantage over another who has cultivated no habits of intercourse with heaven. He is never alone. That divine Saviour with whom he walks is always at his side. To other friends he has often to say, farewell; other connexions frequently call for the parting tear; but of the Lord, who deigns to walk with him, his most faithful Guardian and Comforter, he has never to lament the absence.-Fawcett.

THE MARMOT.

(Concluded from page 353.j

THE PRAIRIE MARMOT.

THE vast solitudes of our remote territories, where man has not yet established his abode, are generally overshadowed by dense forests, which, during an unknown lapse of ages, have there successively flourished and decayed; imparting to the landscape a character of grand though sombre uniformity, broken only by the courses of rivers, the ruggedness and sterility of some portions of soil, or

where the furious hurricane has swept along, prostrating the giant sons of earth with a destructiveness proportioned to their resistance. The traveller who, impelled by curiosity, advances beyond the "father of western rivers," with delighted admiration finds himself gradually emerging from these apparently interminable shades, and entering upon a new world. Before him, spreading as far as vision can extend, he beholds fields of richest verdure, interspersed with clumps of slight and graceful trees, as if with an exclusive view to ornament, and discovers the far distant windings of the river as it steals through the plain, by the cottonwood and willows fringing its banks. After traversing such scenes, enlivened by numerous herds of browsing animals that here find a luxurious subsistence, and arriving at the higher and more barren parts of the tract, he is startled by a sudden shrill whistle, which he may fear to be the signal of some ambushed savage; but, on advancing into a clearer space, the innocent cause of alarm is found to be a little quadruped, whose dwelling is indicated by a small mound of earth, near which the animal sits erect in an attitude of profound attention. Similar mounds are now seen to be scattered at intervals over many acres of ground, and the whole forms one village or community, containing thousands of inhabitants, whose various actions and gambols awaken the most pleasing associations.

In some instances these villages are limited, or at most occupy but a few acres ; but still nearer to the rocky mountains where they are entirely undisturbed, they are found to extend even for miles. We may form some idea of the number of these animals when we learn that each burrow contains several occupants, and that frequently as many as seven or eight are seen reposing upon one mound. Here in pleasant weather they delight to sport, and enjoy the warmth of the sun. On the approach of danger, while it is yet too distant to be feared, they bark defiance, and flourish their little tails with great intrepidity. But as soon as it appears to be drawing rather nigh, the whole troop precipitately retire into their subterranean cells, where they securely

forth, and vigilantly scrutinize every sound and object, before they resume their wonted actions. While thus near to their retreats they almost uniformly escape the hunter; and, if killed, they mostly fall into their burrows, which are too deep to allow their bodies to be obtained.

The villages found nearest to the mountains have an appearance of greater antiquity than those observed elsewhere. Some of the mounds in such situations are several yards in diameter, though of slight elevation. These, except about the entrance, are overgrown by a scanty herbage, which is characteristic of the vicinity of these villages. Say has observed on this subject, that it is not easy to assign a reason for the preference shown by the prairie marmot, which lives on grassy and herbaceous plants, in selecting the most barren places for its dwelling, "unless it be that he may enjoy an unobstructed view of the surrounding country, in order to be seasonably warned of the approach of wolves or other enemies." This reason may be sufficiently valid of itself; but we would suggest another in the difference of soil, rendering such barren places fitter for the burrows. It is by no means necessary to suppose that this marmot obtains its food exclusively near its own dwelling. We know that this is not the case with the Maryland marmot, which so closely resembles this species in every respect, and goes to considerable distances in search of food, even in the immediate vicinity of man.*

The mound thrown up by the prairie marmot consists of the earth excavated in forming the burrow, and rarely rises higher than eighteen inches, though measuring two or three feet in width at the base. The form of the mound is that of a truncated cone, and the entrance, which is a comparatively large hole, is at the summit or in the side; the whole surface, but especially the top of the mound, being well beaten down like a much-used foot-path. From the entrance the hole descends perpendicularly for a foot or two; and then is continued obliquely or somewhat spirally downwards, to a depth which has not been determined.

Pike says of the prairie marmot, that "they never extend their excursions more than half a mile from their burrows."