IN the present state of the globe, a third part only of its surface is occupied by land, and probably not more than a fourth part of that is inhabited by man, but animals and vegetables have a wider range. The greater part of the land is clothed with vegetation and inhabited by quadrupeds, the air is peopled with birds and insects, and the sea teems with living creatures and plants. These organized beings are not scattered promiscuously, but all classes of them have been originally placed in regions suited to their respective wants. Many animals and plants are indigenous only in determinate spots, while a thousand others might have supported them as well, and to many of which they have been transported by man. Plants extract inorganic substances from the ground, which are indispensable to bring them to maturity, but the atmosphere supplies the vegetable creation with the principal part of its food. The black or brown mould which is so abundant is the produce of decayed vegetables. When the autumnal leaves, the spoil of the summer, fall to the ground, and their vitality is gone, they enter into combination with the oxygen of the atmosphere, and convert it into an equal volume of carbonic acid gas, which, consequently, exists abundantly in every good soil, and is the most important part of the food of vegetables. This process is slow, and stops as soon as the air in the soil is exhausted; but the plough, by loosening the earth, and permitting the atmosphere to enter more freely and penetrate deeper into the ground, accelerates the decomposition of the vegetable matter, and consequently the formation of carbonic acid. In loosening and refining the mould, the common earth-worm is the fellow-labourer with man; it eats earth, and, after extracting the nutritious part, ejects the refuse, which is the finest soil, and may be seen lying in heaps at the mouth of its burrow. So instrumental is this creature in preparing the ground, that it is said that there is not a particle of the finer vegetable mould that has not passed through the intestines of a worm: thus, the most feeble of living things is employed by Providence to accomplish the most important ends. The food of the vegetable creation consists of carbon, hydrogen, nitrogen, and oxygen—all of which plants obtain entirely from the atmosphere in the form of carbonic acid gas, water, and ammonia. They imbibe these three substances, and, after having decomposed them, they give the oxygen to the air, and consolidate the carbon, water, and nitrogen into wood, leaves, flowers, and fruit. The vitality of plants is a chemical process entirely due to the sun’s light; it is most active in clear sunshine, feeble in the shade, and nearly suspended in the night, when plants, like animals, have their rest.