a downward course, on account of its gravity. It is thus that an interchange of air is constantly taking place between the equator and the poles. This disturbance has an extensive influence; because, when any considerable portion of the air is removed, the surrounding atmosphere must rush in to fill the vacant place, and thus currents are formed in all directions; while these, again, in their passage, producing condensation or evaporation of moisture, as has been said, by that very process, alter the equilibrium of the air, and increase or diminish the force of the wind. There is thus a very complicated operation continually going on in the atmosphere, which forms the machinery of the weather.

The circumstance to which we have at present to attend, is the formation of clouds; and I have to state, with regard to this subject, that there is here, as in every other atmospherical arrangement, abundant proof of providential superintendence. There are, indeed, so many and such powerful agents in operation, in constant opposition or combination, that it may be difficult, if not impossible, to trace the law by which the effect is produced; but that the alternations of clouds and sunshine, of moisture and drought, taken at an average, are salutary to vegetation, no person need be informed.*

* " In the midst of all this apparent confusion, however,” says Mr. Whewell, after enumerating the effects produced by the different laws regulating air and evaporated moisture, "we can see much that we can understand; and, among other things, we may notice some of the consequences of the difference of the laws of temperature, followed by steam and by air in going upward. One important result is, that the atmosphere is much drier, near the surface, than it would have been, if the laws of density and temperature had been the same for both gases. If this had been so, the air would always have been saturated with vapor. It would have contained as much as the existing temperature could support, and the slightest cooling of any object would have covered it with a watery film like dew. As it is, the air contains much less than its full quantity of vapor. We may often cool an object ten, twenty, or thirty degrees, without obtaining a deposition of water upon it, or reaching the dew-point, as it is called. To have had such a dripping state of the atmosphere as the former arrangement would have produced, would have been inconvenient, and, so far as we can judge, unsuited to vegetables, as well as animals. No evaporation from the surface of either, could have taken place under such conditions."Whewe!! Bridgewater Treatise, pp. 104, 105.

Now, what is particularly worthy of notice, is the controlled and regulated nature of this arrangement. There is no reason that we can perceive, why the relations between moisture and heat might not have been different from what actually exists, and a very slight change in these relations would apparently be sufficient seriously to affect the welfare of plants and animals. Why are clouds formed at all? Or, being formed, why is the place assigned to them so high in the atmosphere? And, again, why is the sun not constantly obscured by clouds; and why are these clouds liable to be formed into rain, and to fall in such genial showers upon the earth? We well understand the final cause of all this. We perceive in these arrangements a remarkable suitableness of atmospherical influences to the nourishment and health of organized existences; but it seems impossible to maintain that there is any thing in the mere mechanical powers existing in the atmosphere, which, of themselves, and without a wise adaptation to each other, could tend to produce these salutary consequences. No one can say that thus it must necessarily have been. That it is so, therefore, implies benevolent design. The only account that can be given of such facts is, that an intelligent Creator has so modified and adjusted the powers which exist in the atmosphere, as to fit them for the uses to which they are applied.

Nor must we forget, that while the existence of clouds, and the peculiar laws by which they are regulated, are beautifully adapted to the heat and light, so as to conspire with these agents in promoting the growth and perfection of the organized world, they also form appearances exceedingly grateful to the taste which the Creator has implanted in his rational offspring, and conducive to enjoyment. The vicissitudes. of sunshine and shade, which the formation and dispersion of clouds produce, form an agreeable variety. The lights and shadows cast over a landscape, by the operation of this cause, are frequently productive of much pleasure, from the effects of contrast and of harmony in the scenery. Whether the sun bursts in his glory from a cloud, or casts a mod

est veil over a neighboring slope, or rests calmly on the distant hills, or drives fleeting shadows across the fields and meadows, while a pleasing warmth pervades the softened air, and mingled sounds of industry and enjoyment are heard on every side, the mind experiences a delightful emotion, which cannot easily be defined, but is obviously derived from the constitution bestowed upon us by a benevolent Creator,

Nor, when we look from the earth to the sky, do we find less reason for acknowledging that a paternal attention has been paid to the gratification of our feelings. The clouds are made to assume a variety of shapes and shades, sometimes beautiful, sometimes sublime, almost always interesting and agreeable, especially during the summer months. The delicate tints which streak the morning sky, when the sun shoots his earliest beams from beneath the horizon, and seems to "rejoice as a bridegroom to run his race;" the fervid glow which is shed over the heavens, when he "looks in his beauty from the clouds, and laughs at the storm ;" and especially the magnificence with which he sinks to rest, while the clouds, which calmly await his departure, resting on the verge of the horizon, appear to be clothed in their gorgeous drapery of gold, scarlet, and purple, in honor of the retiring monarch;-all these appearances are undoubtedly calculated, it cannot be too much to say intended, to fill the heart of the spectator with admiration and delight.

These feelings, when associated with religious sentiments, become exalted and refined. The man who has been accustomed to see God in every thing, receives from all his blessings a satisfaction peculiar to himself; but the pleasure which he derives from objects of taste are especially affected by this principle. He owns them as a direct emanation from a Father's love; he feels a present Deity; and, while his heart expands with a sense of the beautiful, and sympathizes with sounds and sights of enjoyment, he rises beyond the boundaries of earth, to the infinite and self-existent Creator, and expatiates on the perfections of Him who is the source of all beauty and all happiness.

FIRST WEEK-SATURDAY.

DEW.

ALL have been struck with the beautiful phenomenon of dew, and must have had frequent occasion to observe its beneficial effects. A single dewdrop, so beautifully pure and clear, and so lustrous in the morning sunshine, is an object well worthy our attention and admiration. And when we see the fields and lawns, with their innumerable plants, strewn with "orient pearl," and sweetly refreshed by the copious moisture, so as to be prepared for the scorching heat of day, can we fail to be delighted by the beauty of the scene, and profoundly impressed by the inimitable skill with which all vegetation is thus watered and revived?

If we inquire into the causes of dew, and the periods of its more abundant formation, we shall find the same marks of Creative skill and benevolence that meet us in every other field of physical research. These causes may be very briefly stated. In all substances, heat exists in a greater or less quantity; and from these it radiates in all directions, like light from a luminous body. Thus there is a constant and mutual interchange of heat between all kinds of bodies on the earth's surface, and, consequently, a tendency to a universal equalization of temperature. Heat is also given off from bodies by conduction; but conduction, strictly speaking, is only a particular, though a very remarkable, case of radiation. The process of conduction, moreover, is much less general and important than of direct radiation, which, in the great operations of Nature, is the chief means of transmitting heat from one substance to another.

A great portion of the solar heat absorbed by the earth in the course of the day, is radiated into the cooled air during the night; and the radiation proceeds till the surface of the ground is at a lower temperature than the surrounding atmosphere, provided only the sky be serene.

IX.

If the sky be cloudy, most of the radiated heat is retransmitted from the clouds to the earth, so that the temperatures of the earth and atmosphere remain nearly equal. When the heat is not radiated back, but allowed to escape into the higher regions of the atmosphere, and the exposed surface of the earth, and of the substances upon it, thereby becomes colder than the air, it results from the principle of the condensation of vapor by cold, that a deposition of the invisible moisture floating in the air takes place. This moisture generally exists in the greatest quantity when the heat of the sun is powerful and continued; and at nightfall it is ready to be condensed into visible globules by the relatively cold substances with which it every where comes in contact. These globules of condensed vapor form what is called dew, and should be carefully distinguished from the moisture which is formed into clouds, and which visibly descends in the shape of rain or fog. Thus, dew cannot properly be said to fall, as it has been erroneously supposed to do. It is merely caused by the condensation of moisture contained in the air that is in contact with a cold substance; and its formation is strictly analogous to that of the moisture which appears on the inside of windows when the external air is suddenly chilled, of that which appears on a cold stone or piece of metal when we breathe upon it, or of that which is observed on a glass of cold spring-water, in hot weather, or in a warm room.

It has been ascertained, by experiment, that dark-colored bodies radiate heat, and therefore cool, with greater rapidity than bodies of a light color. A dark or green substance, if it be exposed to the night air, will be covered with dew, while substances of a brighter color, in similar circumstances, will remain almost dry. If the surfaces of the latter be smooth or polished, their radiation will be still less perfect, and their dryness consequently greater. our morning walks we frequently see the green grass and bushes plentifully bedewed, while the light materials of the road remain untouched. Here we perceive a new and beneficial effect of the prevailing color of vegetables. Green is not only a lively and beautiful color, and less hurt