TRANSACTIONS OF SECTION A. 



539 



There is indeed at first sight some analogy both in the caee of the sun and of 

 the earth between the eflects observed in their immediate surroundings and those 

 noticed in the neighbourhood of radio-active bodies. The earth we Imow must be 

 charged with negative electricity, and attention had already for some time been 

 drawn to the fact that this charge must constantly be renewed, as the leakage due 

 to the spraying of ocean waves and the hot gases escaping from every chimney 

 would ultimately dissipate the charge. But the normal electric conductivity of 

 the air has only recentlv been measured, and, according to Elster and Geitel, is, 

 under normal conditions, such that a body loses about 1^ per cent, of its charge 

 per minute. If the air in the immediate neighbourhood of the ground has this 

 conductivity (which is not quite certain) the earth would lose about half its charge 

 in an hour. 



We are living therefore— and there can be little doubt about the point— m an 

 electric field through which negatively charged particles are constantly driven 

 outwards (kathode rays), and which possesses an electric conductivity similar to 

 that found in the neighbourhood of radio-active bodies. The radio-activity of air 

 rising out of the ground or of water drawn out of wells may be the consequence 

 of emanations from a radio-active earth. 



The similarity of the rays of the solar corona to kathode rays has often been 

 pointed out, and I have maintained for a long time now that the assumption of a 

 greater conductivity of space at times of maximum sun-spots furnishes a simple 

 explanation of the connection between sun-spots and terrestrial magnetism. The 

 sun, therefore, like the earth, must be taken to discharge rays which seem to 

 possess all properties of kathode rays.^ 



The analogies I have pointed out are not complete, and may be found to be 

 false ; but we must, I think, keep our mind open to the possibility of a collective 

 radio-activity of matter which becomes apparent in celestial bodies. 



The continuous discharge of negative electricity from the earth renders it 

 necessary to find a cause leading to a continuous renewal, and it is extremely 

 diflicult to see what that cause can be. 



Though it is not directly connected with the subject under discussion, I may in 

 conclusion digress by recalling an old discussion on the cause of gravity. Lesage's 

 explanation involved the presence of ♦ corpuscles,' such as are now believed to exist 

 by some physicists. Maxwell's objection to Lesage's explanation, which at the 

 time seemed fatal, was that gravitation ought to be, but is not, accompanied 

 by a rise in temperature. Whatever we may think of the explanation on other 

 grounds, this particular objection would seem to lose its weight at present, when, 

 in the case of one body, at any rate, a rise in temperature above that of its sur- 

 roundings has actually been discovered, and when it is considered that the energy 

 which in one case accumulates as heat may in other cases be dissipated tlirough 

 other channels. 



5. Intensification of Chemical Action hy the Emanations from 

 Gold and Platinum. By G. T. Beilby. 



When a piece of gold or platinum foil is heated on a glass slip in an atmosphere 

 containing the products of combustion of coal gas, a halo is formed on the glass 

 surface surrounding the foil. This halo does not to any considerable extent 

 consist of metallic particles, but is chiefly made up of the products of decomposition 

 of the glass. If the halo is breathed on, the slight condensation of moist^ire on 

 the surface dissolves the soluble salts, and sets free silica or an insoluble silicate in 

 the form of thin films and spicules. When the water has evaporated a crystalline 

 deposit is left on the surface. 



By prolonged heating in the above atmosphere the whole of the exposed 



' The slight diminution of temperature at times of maximum sun-spots, which 

 seems to be indicated by recent discussion of thermometer readings, may be a result of 

 the increased absorption in space which we must expect to be caused by the presence 

 of a sufficient number of electrons. 



