of the sour Living in uty and plenty. Ya key mamITE. -boats are again of the mas m .ultitudes fls the say, my ine amiens and every spot of eari em VIL g Ay persons regard the stage feat a he necessarily brings the of a · unfailingly produs in, as regards chimenes, the ari 1 s the same vegetables migrow, and the VALA, might find their being swym. namely, where heat about, we esta ungd ene of tropical fertility: for era eres int vegetation in endless lovey see, et s ard rocks festooned with grea, priza *** *** rich in its purple dem. It the rice $4 e, animal existence is equal womens, the he species are of surpassing benzey mays, if birds is as brilliant as the gaye toren. 1 vo is perfume from the spice-beda, the y en venda agr ten dyed in tints as brigit a false naAPE, UN appy human inhabitants e. the weeryadian thin vhere heat is absent, we have the dreary ph polar barrenness, namely, bare rock or mountain, marang of fertile field; water every where hardened to wildly, no rain, nor cloud, nor dew, few motions but de snow; vegetable life scarcely existing, and tro sheltered places tr to the sun and ir palms and oth-~ dia, whose single. pearance. But when that is the case, the plant or the animal fails not to be there. And if we have once properly informed ourselves of the circumstances under which it does appear, we can predict its appearance again under similar circumstances with the same certainty, and on the very same principles, that we predict the rising of the sun, or the succession of the seasons. Had the microscope no other recommendation than the pleasure which it thus brings, and the beautiful lesson that, in the sight of God, the extremes of measure are the same, just as the succession of duration, "A thousand years are as one day, and one day is as a thousand years," it would have abundant claims upon our attention. But it is the beauty of all natural subjects, and of all subjects founded upon nature, that we cannot study them without learning something which is useful to us. There are countless operations in the arts which could not be performed without the use of the microscope; and by the help of it, painters, engravers, jewellers, and many other artisans, are enabled to give to their productions a degree of finish and perfection which it would be impossible to give them by the naked eye. We cannot say that the microscope has furnished people with a new sense either for knowing or for doing; but it has given to the sense of sight a degree of improvement which, in some respects, makes man a new creature,-gives him a command over the productions of nature which, previous to its invention, he did not possess.-Readings in Science. THE IMPORTANCE OF HEAT. IN the winter of climates where the temperature is for a time below the freezing point of water, the earth with its waters is bound up in snow and ice, the trees and shrubs are leafless, appearing every where like withered skeletons, countless multitudes of living creatures, owing either to the bitter cold or deficiency of food, are perishing in the snows-nature seems dying or dead; but what a change when spring returns, that is, when heat returns! The earth is again uncovered and soft, and rivers flow, the lakes are again liquid mirrors, the warm showers come to foster vegetation, which soon covers the ground with beauty and plenty. Man, lately inactive, is recalled to many duties; his water-wheels are every where at work, his boats are again on the canals and streams, his busy fleets of industry are along the shores-winged life in new multitudes fills the sky, finny life similarly fills the waters, and every spot of earth teems with vitality and joy. Many persons regard these changes of season as if they came like the successive positions of a turning wheel, of which one necessarily brings the next; not adverting that it is the single circumstance of change of temperature which does all. But if the colds of winter arrive too early, they unfailingly produce the wintry scene; and if warmth come before its time in spring, it expands the bud and the blossom, which a return of frost will surely destroy. A seed sown in an ice-house never awakens to life. Again, as regards climates, the earthy matters forming the exterior of our globe, and therefore entering into the composition of soils, are not different for different latitudes, at the equator, for instance, and near the poles. That the aspect of nature, then, in the two situations exhibits a contrast more striking still than between summer and winter, is owing merely to an inequality of temperature, which is permanent. Were it not for this, in both situations the same vegetables might grow, and the same animals might find their befitting support. But now, in the one, namely, where heat abounds, we see the magnificent scene of tropical fertility: the earth covered with luxuriant vegetation in endless lovely variety, and even the hard rocks festooned with green, perhaps with the vine, rich in its purple clusters. In the midst of this scene, animal existence is equally abundant, and many of the species are of surpassing beauty-the plumage of the birds is as brilliant as the gayest flowers. The warm air is perfume from the spice-beds, the sky and clouds are often dyed in tints as bright as freshest rainbow, and happy human inhabitants call the scene a paradise. Again, where heat is absent, we have the dreary spectacle of polar barrenness, namely, bare rock or mountain, instead of fertile field; water every where hardened to solidity, no rain, nor cloud, nor dew, few motions but drifting snow; vegetable life scarcely existing, and then only in sheltered places turned to the sun-and instead of the palms and other trees of India, whose single leaf is almost broad enough to cover a hut, there are bushes and trees, as the furze and fir, having what may be called hairs or bristles in the room of leaves. In the winter time, during which the sun is not seen for nearly six months, new horrors are added; viz., the darkness and dreadful silence, the cold benumbing all life, and even freezing mercury— a scene into which man may penetrate from happier climes, but where he can only leave his protecting ship and fires for short periods, as he might issue from a diving bell at the bottom of the ocean. That in these now desolate regions, heat only is wanted to make them like the most favoured countries of the earth, is proved by the recent discoveries under ground of the remnant of animals and vegetables formerly inhabiting them, which now can live only near the equator. While winter then, or the temporary absence of heat, may be called the sleep of nature, the more permanent torpor about the poles appears like its death; and when we further reflect, that heat is the great agent in numberless important processes of chemistry and domestic economy, and is the actuating principle of the mighty steam-engine which now performs half the work of society, how truly may heat, the subject of our present chapter, be considered as the life or soul of the universe!-Dr. Arnott. THE WIND. WIND is produced by the expansion of the air by heat, and its condensation by cold. The heat of the sun expanding the air, and causing it to become lighter, it consequently ascends, while the circumambient air rushes in to supply its place. On this principle are those winds accounted for, which, within thirty degrees of the equator in each hemisphere, are constantly blowing. These are the trade winds, which, in some parts, blow for the space of six months in one direction, and during the six subsequent months in a direction completely opposite. That which blows in the northern hemisphere comes from the northeast, that in the southern hemisphere, from the southeast; and under these circumstances they are called monsoons. This variation in the trade winds is produced by the annual revolution of the earth round the sun, which causes the north pole to be directed towards that luminary one half of the year, and the south pole the other halfone being the summer of the northern hemisphere, the other the summer of the southern. We may often learn principles that can be applied to the investigation of nature from comparatively insignificant results. Artificial winds are constantly circulating through our houses. Smoke rises because it is mingled with hot air; and the deficiency of air which is thus produced in an apartment, is supplied by the cold air which rushes through the crevices of the doors and windows. But our fires communicate, at the same time, an increased temperature to a portion of the air in the room, which, consequently, rises; and it will always be found in every building, that the hottest air is at the top. On this account there are always two currents in a room, one outward and another inward, as may be easily proved; for, if a lighted candle be placed near the top of the door, the flame will be blown outward by the heated current which is making its escape; and if at the bottom, it will be blown inward by the cold current which is rushing in.. The same process is going on in nature, on a larger scale, and the principle which explains the one is applicable to the other. Take the land and sea breezes, which occur in all the islands of the torrid zone, as a proof of this statement. During the hottest part of the day, the winds set in from every direction towards the centre of the island; for the sun's rays produce more heat by their reflection from land than from water. When the sun ceases to throw its rays upon the region the land cools, and that portion of air which had been heated by them will begin to descend, and currents will be produced off the land, occasioned by the spreading or equalization of the atmosphere.-Higgins. THE THEORY OF TIDES. ALL water which has an uninterrupted communication with the main ocean, exhibits a continual change of alternate flux and reflux, which is called the flow and ebb of the tide. When it has advanced to its greatest height, and is for a few moments stationary, previous to its again |