Abstract
THE address of the president of Section A, Prof. E. W Hobson, was read oh Thursday, September 1; this has appeared in full in these columns (NATURE, September i, p. 284). It was succeeded by a paper—probably the most important paper read at the meeting—by Sir J. J. Thomson on positive rays. By the use of very large vacuum tubes Sir Joseph has been able to investigate the discharge at higher vacua than hitherto. Specially studying the rays which pass through a hole in the kathode, he detects:—(i) Rays undeviated by magnetic or electric forces. (2) Secondary positive rays, produced by these, which are deflectable by both forces, have a constant velocity of about 2x10″ cm./sec. at all pressures and potential differences. The value of ejm for these is loV They are accompanied by negatively charged ones similar in every respect to the positive ones, except in respect to, charge. (3) Rays characteristic of the gases in the tube,, conspicuous only when the pressure is low. Their velocity varies with the potential difference. When several gases are present, the maximum kinetic energy of the rays from; each gas appears to be the same and equal to that due to a fall through the potential difference between the negative glow and the kathode. The value of elm is inversely proportional to the atomic weight of the gas-They are probably atoms carrying unit positive charge; in the case of hydrogen there are rays corresponding to-the molecule as well. Some of these have negatively charged rays associated with them. In a magnetic field the rays from a mixture of gases spread out into a sort of spectrum. With carbon monoxide two bands are formed, one due to carbon, the other to oxygen. As exceedingly small quantities of gas may be dealt with in this way, it appears probable that interesting results may follow from the application of this method to the analysis of gases in vacuum tubes. (4) Retrograde rays, travelling; from the kathode in the same direction as the kathode rays. These are of types (i) and (2). They have negative-constituents.
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Mathematics and Physics at the British Association . Nature 84, 513–517 (1910). https://doi.org/10.1038/084513a0
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DOI: https://doi.org/10.1038/084513a0