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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 of 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 out heat and light, 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 tho 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 to 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 wasteNo life, no motion, no sound around the whole vast globe to disturb the eternal still and silent void, a void which it is painfpl 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 our 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 tide, 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.
Thk Water Mills Of Aroostoll*
It was a good resolve of Professor Ansted to make a timely visit to the little septinsular republic of the Ionian Isles, to note their state and condition previous to any change which may fairly be expected to arise from the anticipated transfer of them from the guardianship of this country to their now legitimate sovereign. The great change will speedily come off, and it will be an interesting trial in the eyes of Europe to find whether the islanders know how to bear their good fortune. Meanwhile we have in the work before us the result of the Professor's observations at this turning point in the history of these islands; and, well known as they are, with their motley mixtuie of inhabitants, to our nautical readers, we propose giving some extracts from it. And first of the Argostoli Mills, that extraordinary phenomenon of a huge stream of sea water rushing down as it were into the bowels of the earth; sufficient, indeed, to convey the notion of ao underground river, such as was at one time supposed—but in an opposite manner—to have been the termination of the Niger, before Lander set that question at rest. There are, however, other highly interesting considerations presented by phenomena of the sea io the Mediterranean, some of which we shall be able to recur to from the valuable work before us.
The following is the Professor's account of the mills at Argostoli, driven by sea water running into the earth:—
A curious natural phenomenon occurs and is taken advantage of in the neighbourhood of Argostoli. At four points on the coast, the sea, at its ordinary level, enters a very narrow creek, or broken rocky channel, and after running somewhat rapidly through this channel and among broken fragments of rock for a short distance, it gradually becomes sucked into the earth and disappears. By conducting the water through an artificial canal for a few yards, and so regulating its course and forcing all the water that enters to pass in a single stream beneath an undershot wheel, power enough is obtained in two cases to drive a mill. Mills have in fact been placed there by an enterprising Englishman, and are constantly at work. The stream after being utilized, is allowed to take to its natural channel, and is lost among the rocks.
It is common enough to drive a wheel by a current of water going from the land towards the sea; but it is certainly rare, and, as far as I am aware, peculiar to the locality, to find mills driven by a current of sea water, acting quite independently of tide, the water constantly and steadily rushing in over the earth's surface and finally disappearing. It is not the river god pursuing the nymph, but the great Neptune himself invading the domain. No wonder the Cephalonians are proud of their mystery; and it will be interesting to consider the circumstance's attending it.
• The Ionian Islands in the Year 1863,—By Professor Ansted, M.A., f.R.8. Allen and Co., London.
Apart from the facts that the water sucked into the earth is sea water, and that it enters below the sea level, there is nothing extraordinary or unusual; for numerous instances occur in every limestone country of streams, often of very considerable dimensions, entering into open fissures and disappearing. In England there are two or three cases of this kind, and in the Ionian Islands absorption of water into the earth is so rapid, that there is hardly an instance of any appreciable quantity of the rain-fall being retained long enough on the surface to form streams and carry off- the water to the sea. Almost all the rain is there absorbed, and this is certainly the result of the cracked and broken nature of the limestone rock—of the numerous natural caverns penetrating every part—of the constant enlargement of fissures into caverns in one place, and the choking up of caverns by stalagmite and stalactite in another—and of the especially fissured and cavernous nature of certain kinds of limestone, of which the rocks found in the Ionian Islands and Greece afford notable examples.
But it is certainly very seldom that we are able to satisfy ourselves of the empty state of the limestone caverns close to the sea and below the sea level, as we can at Argostoli; and for this reason, if for no other, the phenomena are worthy of particular notice.
The general condition of the surface is as follows. The small harbour of Argostoli is enclosed on both sides by the hard, broken, limestone rock so common in the islands. On the east side it rises immediately into hills of moderate elevation; and on the west side, behind the town, there is a plateau, scarcely above the usual level of the water, rising about two or three hundred yards from the shore into a low ridge, which, in fact, by its projection into the gulf makes the harbour. Between the shore line and this low ridge there is an evident depression of the surface in all that part over which the sea, when it enters is sucked in. There is evidently beneath this part an extensive cavernous tract, which may well hold much more water than during any ordinary season or succession of seasons can drain naturally into it in consequence of the rainfall at the surface.
But what, it will be asked, becomes of the waters of the sea thus pouring in continually to fill the cavern? Certainly, in time, any cavity must be filled, if it has no natural outlet, and if water is constantly entering it. How, also, can the water run off, if its level in the cavern is below the sea level. It is not, perhaps, so difficult as may be thought to answer these queries.
The water that everywhere enters the earth is always circulating. It not only pours down into and amongst all rocks, but it is afterwards lifted, and the level of these subterraneous stores is greatly elevated by operations going on at the surface, often at a great distance above.
The cause of this is evaporation, which proceeds incessantly from the surface of all rocks, but especially from limestones. The narrow crevices, common in limestone rocks, act as capillary tubes. When water falls on the surface of such rock, it finds its way down readily, and this seems quite natural; but when, in hot countries, where there is a long summer season of great drought, the surface becomes dry and hot, moisture rises in steam from below; and, as the heat and dryness increase, the accumulated waters become more and more exhausted. All this goes on without reference to the actual level of the water line within the earth, which may be far beneath the level of the sea.
That this is the case in the softer limestone rocks, even when not cracked, has been proved by actual experiment. That it takes place to an enormous extent in the limestones of the eastern Mediterranean is proved, if in no other way, by the fact that vines, planted among bare stones, without soil, obtain an ample supply of moisture from the earth, and ripen their fruit to perfection in the hottest and driest seasons. No doubt the earth and rocks are hot, and appear dry; but Bo long as there remains any water below that has passed down during the rainy season, so long will a part of that water be given back to the dry and thirsty soil above.
If, then, as is probably the case, there is so large an evaporation from the part of the surface of the Island of Cephalonia, within range o.f this district, as to keep the water level of the year below the sea level, in spite of the joint supply of rain and sea water, it is clear that the water may run in for ever at the same rate without filling up the space. And this I believe to be the correct explanation of the phenomenon.
The influx of water, however, is not small. It amounts, as far as I could make out, to more than half a million of gallons per diem, for the two mills together. The fall of water from the sea level into the cavities, where it disappears, seems to be little more than a foot or eighteen inches.
There appears to be something like a lunar tide in the harbour and gulf of Argostoli, the water entering and flowing out twice a uay, and the level of the water varying about six inches in ordinary weather, and when there are no disturbing influences. Any wind blowing steadily for some time, and all storms, whether at a moderate distance or near, affect the water level in a marked degree, and complicate the apparent tide. In one of the cavities where the water disappears from the surface, the level of the surface of the water below may always be reached, and it is said to rise and fall with that of the sea, even when the influx of the water is stopped. This is quite possible, without assuming a free communication, which would of course at once fill the cavern to the sea level.
There is a constant tendency to choke up the crevices through which the water disappears, by a seaweed very common on this coast This and the silt would probably soon interfere greatly with the current that enters the crevices, if the channel were not kept artificially clear. The water, however, is greedily and rapidly absorbed by the whole surface of broken ground near the sea, between the two mills.
It will be evident that if the sea water finds its way into any large natural cavity from which it is afterwards evaporated, a deposit of salt must be taking place in this cavity, or in rocks adjacent or connected with it. Assuming the influx to be at the rate already mentioned,