_The Unknown_.--I will be more minute. You will allow that the rendering skins insoluble in water by combining with them the astringent principle of certain vegetables is a chemical invention, and that without leather, our shoes, our carriages, our equipages would be very ill made; you will permit me to say, that the bleaching and dying of wool and silk, cotton, and flax, are chemical processes, and that the conversion of them into different clothes is a mechanical invention; that the working of iron, copper, tin, and lead, and the other metals, and the combining them in different alloys by which almost all the instruments necessary for the turner, the joiner, the stone-mason, the ship-builder, and the smith are made, are chemical inventions; even the press, to the influence of which I am disposed to attribute as much as you can do, could not have existed in any state of perfection without a metallic alloy; the combining of alkali and sand, and certain clays and flints together to form glass and porcelain is a chemical process; the colours which the artist employs to frame resemblances of natural objects, or to create combinations more beautiful than ever existed in Nature, are derived from chemistry; in short, in every branch of the common and fine arts, in every department of human industry, the influence of this science is felt, and we may find in the fable of Prometheus taking the flame from heaven to animate his man of clay an emblem of the effects of fire in its application to chemical purposes in creating the activity and almost the life of civil society. _Phil_.--It appears to me that you attribute to science what in many cases has been the result of accident. The processes of most of the useful arts, which you call chemical, have been invented and improved without any refined views, without any general system of knowledge. Lucretius attributes to accident the discovery of the fusion of the metals; a person in touching a shell-fish observes that it emits a purple liquid as a dye, hence the Tyrian purple; clay is observed to harden in the fire, and hence the invention of bricks, which could hardly fail ultimately to lead to the discovery of porcelain; oven glass, the most perfect and beautiful of those manufactures you call chemical, is said to have been discovered by accident; Theophrastus states that some merchants who were cooking on lumps of soda or natron, near the mouth of the river Belus, observed that a hard and vitreous substance was formed where the fused natron ran into the sand.