Joseph John Thomson

“ The circumstances are very unfavourable for a particle in the positive rays to get a negative charge, and we must not conclude that because an atom or molecule has not been observed to acquire a negative charge when in the positive rays it is incapable of doing so under more favourable circumstances. ”

“ As each parabola corresponds to a different kind of charged particle this shows that there are only a limited number of different kinds of particles in the discharge tube. The sharpness of the lines shows that all the particles of the same chemical element have to a very high degree of accuracy the same mass. If the atoms of hydrogen, for example, differed appreciably in mass it would not be possible to get on the photographic plates parabolas as sharply defined as those which can be obtained when the tube through the cathode has a very fine bore. ”

“ For in the dark space in front of the cathode there is an intense electric field in which the free corpuscles are moving far faster than the particles so that the relative velocity of the particles and free corpuscles is much greater than that of the particles and the corpuscles in the molecules, and therefore the union of the positively electrified particles and the free negatively electrified corpuscles is not likely to occur ”

“ We conclude that the ionization on the gas is not therefore in the main due to the fast cathode rays: It arises more probably from slow cathode rays and from positive particles. The positive ions from the negative glow when they get into the dark space soon acquire sufficient energy to ionize the gas, producing corpuscles and other positive ions. ”

“ We have seen too that the atoms of all the elements except hydrogen can acquire more than one unit of positive charge. The maximum number of such units seems to depend on the atomic weight of the atom, for mercury, the heaviest atom yet investigated, it Is as large as eight, for krypton four or five, for oxygen two, and so on. ”

“ It will be noticed that only a small fraction of the current is carried by free carbon and oxygen atoms, showing that in phosgene the carbon and oxygen atoms are so firmly united that the greater part of them remain together even when the gas is dissociated. ”

“ The particles which are produced near the cathode will not, when they reach the cathode, have fallen through as great a potential difference as those produced farther away and will therefore have a smaller velocity. ”

“ The positive rays are deflected by a constant electric field of such a magnitude that the heads of the parabolas are in line with one end of the slit The magnetic field is then increased by small increments and the deflection of the Wilson electroscope in ten seconds measured, Unless a parabola comes on the slit there Is practically no deflection ”

“ There are many cases, however, where concentration does not occur, and where the arcs of the parabolas are very long, indicating that there is a very considerable range in the kinetic energy of the particles, the uniform intensity of the lines shows that the number of particles is fairly equally distributed over a considerable range of kinetic energy. ”

“ On the Information Afforded by the Positive Rays as to the Constitution of a Gas, the Nature and Properties of the Molecules, and the Process of Ionization in a Discharge Tube The results we have given above enable us to appreciate the importance of the positive rays In Investigating the con- stitution of gases and the properties of atoms and molecules. ”

“ We find, however, on the same plate lines which are quite short, with all the intensity concentrated at the head, and others which are long and of equal intensity throughout The second suggestion, that positive particles are produced at different parts of the field by other positively electrified particles in rapid motion, seems to me to Indicate an effect which must undoubtedly be largely instrumental In increasing the length of the parabolas. ”