" The wind bloweth where it listeth, and thou hearest the sound thereof, but canst not tell whence it cometh, and whither it goeth." WE are not about to write a sermon, although we have commenced with a text; but the sentiment conveyed by it is so beautiful and appropriate to our subject that we cannot resist its introduction. And surely it may be both advantageous and interesting to many of our seafaring readers to study reverentially, and somewhat more attentively than they may have already done, that mysterious phenomenon, the mighty gale, which, though they see it not, they both sensitively hear and keenly feel; whose effects, so far as evident to them, may have seemed J» be only or chiefly evil; and on which, in moments of anxiety or self-reproach, some of them may even have looked with fear and trembling, as an agent of Divine wrath, strewing its pathway with devastation and woe.

Now, we hope to make it clear to such persons that the fiercest gale, however calamitous in some of its effects, is not an instrument of anger, or the result of a fortuitous chance; but that, on the contrary, it is a part of a well-considered and benevolent plan, chiefly an instrument of good, and that its partially destructive effects are only sufficient to place it in the category of imperfection, in which all things in this temporary world must be classified. And surely they may derive from such knowledge that calm and resolute acquiescence in God's providence as shall come to their aid when danger threatens, and impart to them the coolness of head and strength of nerve which shall best enable them to successfully battle with and avert its consequences.

If in any cases such should be the result, we shall have attained the practical end which we have in view. For how many valuable ships, and still more valuable human lives, annually perish from the want of that cool judgment and presence of mind in those in command, which, in moments of extreme peril, is beyond price! It is, of course, known to every one that the wind is merely the air in motion; but the nature of the air, the reason why it is put in motion, and what occasions its being so, is known to comparatively few. We will briefly attempt to supply that rudimentary knowledge of the subject which should be possessed by every one, and which cannot but be both interesting and useful.

The air, which is the first essential to all animal and vegetable life, is what is termed an elastic fluid : although invisible to us, it is as much a fluid as water and the many other ordinary liquid bodies which are visible to the eye, and with which every person is familiar; but it is much lighter than liquids, or, technically speaking, it has less density. It also possesses the property of elasticity to an indefinite extent, which water and other liquid bodies do not. Thus water, even under enormous pressure, can only be slightly compressed into a smaller compass; but air can be compressed by force, or expanded by the withdrawal of pressure, to an amazing extent. For instance, a thousand cubic feet of air, by the aid of sufficiently powerful machinery, might be compressed into the space of one cubic inch, whilst, on the other hand, if from an airtight vessel, of sufficient strength, holding a thousand cubic feet of air, the whole of it except one cubic inch could be artificially abstracted, the remaining cubic inch would, from its own elasticity or expansive power, completely fill the whole vessel.

The air which surrounds this globe is a compound- body-—that is to say, it is composed of different bodies, which can be separated one from the other. Its principal ingredients are two gases, called oxygen and nitrogen; these are mechanically combined in the proportion of four measures of nitrogen to one measure of oxygen. In the great laboratory of nature they are being constantly separated the one from the other, by the respiration or breathing of animals and of plants, and by combustion or burning, and also by the oxidation of metals, fermentation, &c.

This important body, the air, without which no animal or vegetable life could for a moment exist, and on the purity of which the healthy state of each so greatly depends, has been generally supposed to be of essentially a local character, being confined to a comparatively short distance above the earth's surface, and which distance has been variously computed by astronomers at about 40 or 45 miles. Such, however, is the elasticity of the air, that at the height of about 3 miles above the sea-level, the aeronaut, or mountain traveller, has ascended through one half of the atmosphere; the remaining half being less subject to pressure and the attraction of gravitation, occupying no less than 40 or more miles in vertical height. At the level of the sea the barometer stands at the mean height of 30 inches; but at the height of 3'4 miles it stands at only 15 inches, at 6'8 miles at 7 • 50 inches.

Some idea of the attenuation of the air at a short distance above the earth's surface has been lately exemplified by Messrs.

Glaisher and Coxwell, in their perilous balloon ascents in this country, when, on one occasion, at a few thousand feet above the earth's surface, the pigeons they threw out, beating the " thin air" with their powerful wings, obtained no support therefrom, but fell rapidly, as though lifeless, towards the earth; and when at the extreme height of 6i miles, to which they ascended, the combined effects of the reduced pressure on their bodies and the more rarefied food to their lungs reduced Mr. GLAISHER to a state of insensibility, and almost overpowered Mr. COXWELL, thus proclaiming, as in so many words, to the race of man, " So far canst thou come, but no farther, and hither shall thy proud course be stayed." We have stated that the air is a compound body, and that its component parts are readily separable the one from the other by various means. It is also capable of holding foreign bodies, such as aqueous and other vapours and exhalations, and minute particles of vegetable and mineral solids, in the shape of dust; and of retaining in connection with it other gases, the products of the decomposition of animal and vegetable matter, and of combustion. It follows, therefore, that its properties near the earth's surface, as a respiratory and alimentary medium, must be of a varying character, according as foreign bodies, by exhalation or otherwise, have mingled with it. It is, however, a remarkable proof of design that the two chief constituents of the atmosphere are always in the same proportion ; for whether in a fever hospital or on the top of a mountain, the nitrogen and the oxygen are in the ratio of four to one.

But, even if experience did not prove such to be the case, we might reasonably expect, from the analogies of nature, that some one especial state and proportional combination of the ingredients of the air would be fitter for the respiration and health of animals and vegetation than any other, and that, therefore, some plan would have to be devised and arranged to maintain generally that happy equilibrium. We need not, however, theorize on this point; for the statistics of health and the returns of the registrars of deaths only too plainly record the often dreadful effects of poisoned air in our larger cities and towns, from want of ventilation in the dwellings of the poor, and from insufficient or imperfect sewerage in general; and in many of our rural districts, from the malaria arising from undrained marshes and swamps.

Before, however, seeking for that machinery in nature, devised to compensate for such local disturbances of the purity and life-supporting properties of the air we breathe and live on, it may be worth while to consider for a moment some of the known important properties of the air, although all those properties which Infinite Wisdom has planned may not, and perhaps never will, be discovered by man. In describing, or rather briefly relating, some of these wondrous properties, we shall not attempt to enter into an explanation of them, this not being a scientific treatise, and our only object being to convey some faint impression, in this one phase of nature, to the minds of the more unscientific of our readers, of the wisdom, and power, and contrivance that have been, and are being, exerted by the Great Creator of all things for the sustenance and welfare of his creatures.

1. SUPPORT OF ANIMAL AND VEGETABLE LIFE.—The first and highest function of the air, if we may reverently use the expression, is the support of the life of man, of intelligent beings; the support of the life of all the inferior races of animals and of the vegetable world being subservient to it. It will be sufficient to state that this wonderful power is effected through the medium of organs which, in the higher classes of animals, reside in the lungs and in the skin, and in plants in their leaves, which organs have the power of decomposing the air, and appropriating that portion of it which is necessary for the growth or support of animal or plant, and discarding that part which would be useless or injurious to it. It will be sufficient to further state generally that that part of the air which is exhaled by the animal as a product oi respiration is necessary to the plant, and that that part which is changed by the animal and by combustion is vivified so to speak, by the expiratory organs of the vegetable world, and that thus the general equilibrium or purity of the atmosphere is maintained.

2. COMBUSTION:—Without the medium of the air there could be no combustion, as the process is commonly understood, since fire cannot under ordinary circumstances exist unless fed by oxygen gas; and inflammable bodies, in giving oat heat and Jight, decompose the air and consume its oxygen.

Indeed, the process by which the air is decomposed and its oxygen appropriated by the breathing organs of animals, thereby producing animal heat, is a species of combustion.

How great a necessity, therefore, is this property of the air must be felt by every one.

3. EVAPORATION. — Another important property of the air or atmosphere, caused by its density and weight, is the distribution of moisture. The minute aqueous particles which now float upwards through the air become partially condensed under change of temperature; they congregate in clouds, and are carried by the winds of heaven over the dry land, there to1 fall in refreshing rain, revivifying the face of nature, and replenishing the lakes and springs and rivers for the use of man. If there were no atmosphere, the ocean, to be sure, and the dry land would still exist; but the former would be calm, and still, and lifeless, a veritable " dead sea," and the latter one great waste.

No life, no motion, no sound around the whole vast globe to disturb the eternal still and silent void, a void which it is painful even to contemplate.

4. REFLECTION OF LIGHT.—A fourth remarkable property of the air is the reflection and diffusion of light. If there were no air there would be perfect darkness on every spot on which the sun's rays did not fall; no object would be visible, even under the shadow of a house or a wall, and intense darkness would be in all onr dwellings, for, as already stated, without the air there could be no combustion, and, therefore, no artificial light.

5. TRANSMISSION OF SOUND.—Without the air there would be no sound, all sound being occasioned by a motion or vibration of the particles of the air, so that without the air there could be no speech.

Our space, however, will not allow us even to enumerate all the known properties or functions of this wonderful and beautiful fluid. Without it, we could not navigate the ocean—we could work no metals; indeed, as we have already shown, without it we could not live.

Such being, then, the all-important character of this surrounding medium in which " we live, and move, and have our being," we might feel sure, as inferred under a previous heading, that some adequate machinery would be set in motion to preserve it in the purest and most fitting condition to fulfil the important functions required from it.

Such a machinery exists in the wind— that is, in the motion given to the air itself; through which motion as complete a circulation and intermingling of parts and purification of the whole is provided as exists in the animal body by the circulation of the blood, and in the waters of the globe by the system of ocean currents and tides, and rivers, and streams. The great " trade winds," as they are termed, near the ocean's surface, and the great counter or return currents, in the higher regions of the air, being, as it were, the gigantic arteries and veins of the system, and the lesser and more temporary winds being subsidiary to them.

It will be sufficient here to state that the chief cause of the wind is change of temperature in the air over large surfaces: the heated air, for instance, as in the tropics, becoming lighter by expansion, and ascending into the higher regions, and the colder and heavier air from the Poles rushing on, like an ocean tidej to supply its place. The winds are also affected by the motion of the earth on its axis, and probably, to some extent, like the waters of the sea, by the moon's attraction.

That, however, with which we have chiefly to do is the point from which we started, that the great object of the wind, even of the fiercest gale, is a benevolent one, affecting the whole human race; that any evil which accompanies it is minor and temporary, affecting comparatively but few persons ; and that the loss of human life which is occasioned by it at sea arises, for the most part, from the unskilfulness or ignorance, and only too often from the culpable neglect, of the owners of shipping property, and of seamen themselves.