276 CARNEGIE INSTITUTION OF WASHINGTON. 



the aid of a suitably arranged series of taps, air from the atmosphere may be 

 admitted so as to wash out completely the residual gases from the furnace 

 and into the ionization chamber. Owing to the evolution of chlorine, it was 

 found necessary to allow the gases to pass into a flask loosely packed with 

 silver shavings before they passed into the ionization chamber. The wall of 

 the ionization chamber was supplied with a potential of 100 volts, and its 

 central rod was connected to the fiber of a unifilar electroscope. 



The specimens of salt having been dried out, they were sealed in thin-walled 

 glass tubes, provided with narrow openings which could be closed with a little 

 molten wax. After remaining sealed for an appropriate time, a tube was 

 introduced into the furnace and a determination was carried out. The wax 

 melted and released the gaseous contents before the pressure had risen suffi- 

 ciently high to burst the tube, and the glass tube itself became subsequently 

 dissolved in the process of heating the fusion mixture. The apparatus could 

 be subsequently standardized by fusing a known amount of analyzed carno- 

 tite with fusion mixture. 



The samples of salt examined were those collected by the Carnegie on her 

 fourth cruise in the Pacific and Sub-Antarctic Oceans. The radium content 

 was found to be negligibly small compared with the values found by J. Joly and 

 others for salt collected near land. It is to be noted, however, that the present 

 samples are from ocean areas far removed from land. Former observers, 

 including Joly, have concluded that the radium-content diminishes with 

 increase of distance from land, so that the Carnegie's results are in harmony 

 with this conclusion. 



The report on the above investigation appeared in the December 1917 

 issue of Terrestrial Magnetism. 



On the origin of the Earth's electric charge. W. F. G. Swann. [Abstract] Jour. Wash. 

 Acad. Sci., vol. 7, No. 9, 270-271 (May 4, 1917), Washington. Physical Rev. 

 ser. 2, vol. 9, No. 6, 555-557 (June 1917), Lancaster, Pa. (Papers presented 

 before the American Physical Society, New York, February 15, 1917, and the 

 Philosophical Society of Washington, March 17, 1917.) 



Measurements of the variation of the penetrating radiation, with altitude, 

 point to the upper atmosphere as the origin of a part of this radiation. The 

 whole of the penetrating radiation is probably of the 7-ray type, but the part 

 which reaches the Earth's surface from the outer atmosphere is naturally the 

 most penetrating part. Indeed, it is so penetrating that it passes through a 

 thickness of air which would be equivalent, in absorptive action, to a column 

 of mercury 76 cm. high, if absorption coefficients were simply proportional to 

 density and were independent of material. The 7-ray radiation from the outer 

 layers of the atmosphere is consequently very "hard," and, in accordance 

 with the known results of laboratory experiments, we must conclude that the 

 negative corpuscles which it emits from the air molecules are emitted almost 

 entirely in the direction of the radiation, and further, that they can have a 

 range in air at least equal to that of the swiftest |8-rays from radium products. 

 The emission of corpuscles by these 7-rays will consequently result, at each 

 point of the atmosphere, in a downward corpuscular current of negative 

 electricity. This corpuscular current will charge the Earth until the return 

 conduction current balances the corpuscular current at each point of the 

 atmosphere. 



Taking, for the purposes of this abstract, a simplified case where the pene- 

 trating radiation considered is all directed vertically downwards, if q is the 

 number of corpuscles liberated per cubic centimeter per second by the pene- 



I 



