In every branch of natural history the study of the science, in its manifold forms of classification, is constantly leading to the most valuable discoveries connected with our means of existence. Some twenty years ago all the timber of the Hartz Forest in Germany was destroyed by a species of beetle, which, gnawing completely round the bark, prevented the sap from rising. This destructive animal made its appearance in England; and science very soon discovered the cause of the evil, and provided for its removal. If there had been no knowledge of natural history here, not a tree would have been left in our woods: and what then would have been the cost of timber. The naturalist is now carrying his investigations, with the aid of the microscope, into the lowest departments of animal life. He finds the causes of blight and mildew, and knows the species of the minutest insect that mars the hopes of the farmer and the gardener. The chemist steps in; and the ravager is destroyed or rendered less noxious. It is to the scientific travellers that we owe the successive introduction of new materials of manufactures. Of the enormous extent in which such new materials affect production, we may form some adequate notion from the mention of three--India-rubber, Gutta Percha, and Palm-oil. In 1853 we imported 1,940,000 lbs. of caoutchouc or India-rubber. The gum of a Brazilian-tree, discovered by some scientific Frenchman in 1735, had been employed for nearly a century for no higher purpose than rubbing out pencil-marks. After 1820 the mode of applying the substance for the production of water-proof garments was discovered. But even in 1830 we only imported 50,000 lbs. Since then caoutchouc has become one of our great materials of manufacture, applied, not only to clothing, but to useful articles of every description. Its great property of elasticity has rendered it available in numberless instances beyond those of making cloth water-proof and air-tight. When we discovered how to make India-rubber soluble by spirit, we obtained our water-proof clothes, our air-cushions, and water-beds. When machinery drew out the lump of gum into the finest threads, and connected them with cotton, flax, silk, or worsted, in a braiding-machine, we became provided with every species of elastic web that can render dress at once tight and easy. But chemistry has carried the use of India-rubber further than the spirit which dissolves it, or the machinery which splits it into minute threads. Chemistry has combined it with sulphur, and thus added in a remarkable degree to its strength and its elasticity. It has made it independent of temperature. It has doubled its utility. "Vulcanized India-rubber" is one of the most valuable of recent inventions.