The wonderful century - 1899 Author:Alfred Russel Wallace Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER VH. THEORETICAL DISCOVERIES IN PHYSICS. Has matter motion ? Then each atom, Asserting its perpetual right to dance, Would make a universe of dust! ... more » For the world was built in order, And the atoms march in tune. —Emerton. The theoretical discoveries in the domain of physica (besides those already referred to) have been very numerous, but only a few of them have enough generality or have become sufficiently popular to require notice in the present sketch. Two of these discoveries, however, stand above the general level as important contributions to our knowledge of the material universe. These are (1) the determination of the mechanical equivalent of heat, leading to the general theory of the conservation of energy, and (2) the molecular theory of gases. Down to the beginning of this century heat was generally considered to be a form of matter, termed caloric or phlogiston. The presence of phlogiston was supposed to render substances combustible, but when the chemical theory of combustion was discovered by Lavoisier, phlogiston, as the cause of combustion, disappeared, although caloric, as the material basis of heat, still held its ground. Close to the end of the last century Count Rumford showed that in boring a brass cannon the heat developed in 2£ hours was sufficient to raise 26£ Ibs. of water from the freezing to the boiling point. But, during the operation, the metal had lost no weight or undergone any other change; and as the production of heat by this process appeared to be unlimited, he concluded that heat could not be matter, but merely a kind of motion set up in the particles of matter by the force exerted. Bacon and Locke had expressed similar ideas long before; and, later, Sir Humphrey Davy showed that by rubbing together two pieces of ice ...« less