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If Prof. J. J. Thomson's corpuscular hypothesis be absolutely demonstrated, our ideas in regard to chemistry will be revolutionized. In a recent lecture before the Royal Institution he selected as his subject "The Existence of Bodies Smaller than Atoms." He briefly referred to work which had been done by others in theory and practice, in order to determine the size of an atom. One method of doing this was by ascertaining the charge of electricity which an atom carried during the process of electrolysis, and from the charge to calculate the mass. The experiments of the lecturer were made with the view of ascertaining the mass of small particles which carry an electric discharge through attenuated gases. The next experiment was made with the object of ascertaining the mass of all the particles used to carry the charge and also their number. For this purpose some of the experiments of Mr. Wilson on the sudden expansion of a gas saturated with moisture were used. He found that a cloud was not produced by the sudden expansion if the air was quite free from dust. It was also found that if either the dust or the charged particles ot" gas were present a cloud was formed. The total quantity of moisture in the cloud can be calculated from the expansion. Some experiments of Prof. George Stokes were then employed to ascertain the volume of each particle. These experiments had for their end the careful determination of the rate at which particles of water would fall, the speed being dependent upon the dimensions. From the formula which Prof. Thomson obtained, he was able to ascertain the size of the particles by observing the time it took for the cloud formed in the tube by a sudden expansion to fall. Once he knew the size of one particle and the total mass, it was not difficult to make calculations. He concluded that the small particles carrying the charges of electricity were only one-thousandth of the size of an atom. These experiments were all made with discharges pf negative electricity. It was also found that these small particles negatively chrged were given off from incandescent matter and from radium. Prof. Thomson expressed mathematically the laws of Becquerel and cathode rays and then showed from his equations that the rays possessed momentum and, therefore, must have mass. When he first enumerated his theory to the scientific world three or four years ago, it was received with considerable incredulity, but has now been adopted by many scientists. He regards the chemical atom as made up of a large number of similar bodies which he calls "corpuscles." A normal atom forms a system which is electrically neutral. The electrification of a gas consists in the breaking off from the atoms of a few corpuscles. The remainder of the atom is positively electrified, and the more corpuscles that are broken off the stronger is the attraction that binds the remainder to the atom. Prof. Thomson has calculated from the results of his experiments on very different substances that the mass of a negative corpuscle is about the five-hundredth part of the hydrogen atom. The subject is treated at considerable length in the current issue of our SUPPLEMENT.