§ 1. It has been often remarked, and with great truth, that the world abounds with life. In the remains of that which had once lived, which was at one period organic, the illustrious Cuvier and the great school to which he belonged saw the materials of life, the food, in fact, of that which exists; he held that between the inorganic and organic worlds there was an impassable gulf, or in other words, an inconvertibility or a metamorphosis, call it by what name you will. This plausible theory, with many others, is now controverted by modern chemists, who boldly assert that no organic atoms or molecules, as such, can serve as food for a plant or an animal. But be this as it may--for chemists admit that the incombustible constituents or the salts of the blood, so essential to the nourishment or support of animal life, must have passed through organic bodies[27]--one thing is certain, that the extent of life on the globe can scarcely be imagined. For first, as regards the vegetable kingdom, do we not observe how, as spring and summer advance, the organic beings which during winter had lain dormant at the bottom, or deeply entombed in the waters (I speak not of those to be seen at all times on the surface of the earth), rise to the surface, bringing with them countless myriads of the ova of aquatic animals and of those which haunt the surface of the water? Amongst these stand pre-eminent the infusoria or zoophytes; with these the atmosphere also becomes loaded. They form, in fact, the substratum of all animal life, constituting the food not only of animals somewhat larger than themselves, but of many much larger, as the various species of the cyprinus. Many valuable gregarious fishes, as the herring, char, and the finer species of trout, live on entomostraca; they in their turn become the food of larger and more voracious fishes. Even the whale lives on food a portion of which is almost microscopic. Now, withdraw the water by which all this life subsists, and putrescence, or fermentation and decay, must be the result upon a mass of life of which the amount may be faintly conjectured by the fact that 4,100,000,000 millions of infusoria may be found in a square inch. These insects, when dead, are found in strata extending to some acres, and many of the fossils thus discovered belong to species of genera now alive. The principles of life were at least as active in what we call the old world (though in reality the young world), as in the present; the researches of Ehrenberg, repeated by many others, have placed these opinions beyond dispute. [27] Liebig. Now, it is by no means improbable--nay, it is almost certain--that many species of these infusoria reside in the vapour of the atmosphere.