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.

III.

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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. In 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

ful to the eye, but green substances are among the best radiators of heat, and are therefore most liable to condense the moisture of the surrounding air. Thus the leaves of plants, which require a constant supply of moisture, being mostly of a green color, are admirably fitted to procure it.

In warm and settled weather, when the hot day is succeeded by the calm clear night, dew is most abundant. Now, it is just then that it is also most necessary; for the heat of the sun, unmitigated by any cloudy screen, increases greatly the general evaporation, and there is no rain to compensate for the increased quantity of moisture of which plants are thereby deprived. In cloudy weather, when the solar heat is mitigated, and rain is more abundant, dew is less necessary to the health and nourishment of plants; and it is precisely such weather that is most unfavorable to its formation. The clouds, as we have already seen, radiate back the heat transmitted from the earth, and thus prevent the temperature of the ground from sinking to the dew-point. Frequently, when a clear nocturnal sky is suddenly covered with clouds, the dew already formed is evaporated, as the temperature of the earth is increased by the counter-radiation from above. And, again, should the clouds clear away, and the sky become serene, dew immediately begins to form. Thus, there is not unfrequently an alternate formation and evaporation of dew in the course of the night, as the aspect of the sky fluctuates between clear and cloudy. In covered or shady spots, it has been observed that there is always the least dew. The shade or covering radiates back the heat, and thereby keeps up the temperature of the ground below. Thus, in the recesses of the wood, where, on account of the impervious shade, there is least evaporation during the day, little or no dew is formed upon the rank grass, which is otherwise well provided with moisture so little superfluity of means is there in the works of Nature. In the production of any given effect, there is an economy of resources, which, while it greatly enhances to our apprehension the wisdom and skill of the Creator, is well fitted to teach us a useful moral lesson.