208 Dike — Recent Observations in Atmospheric Electricity. 



riers of different velocities and different sources. The presence 

 of both radium and thorium emanations was shown, and the 

 specific velocities of the positive carriers of radium emanation 



were found to be in region between 25 and tt-t^t — ' / , 



6 40,000 sec./ cm.' 



while that of thorium emanation lay in the region between 15 



n cm / volt mi , , .. . 1 _ 



and 0*2 ■ — •' / . Ine negatively charged carriers could not 



sec./ cm. iD j n 



be collected in sufficient quantity to give a quantitative measure- 

 ment. From the specific number of the carriers found in the 

 atmosphere the ionization caused by them was computed and 

 found to be only a small portion of the total ionization of the 

 atmosphere. Most of the authorities agree in concluding that 

 the radio-activity of the atmosphere can play only 'a minor role 

 in its ionization, and that the ionization must be referred to 

 other causes. My own experience at sea led me to the same 

 conclusion, for there no measurable amount of induced radio- 

 activity could be collected, while the ionization was as great 

 as on land if not greater. Eve, on the other hand, reports that 

 he has found the amount of emanation in the air over the 

 Atlantic Ocean to be as great as over the land. Freshly fallen 

 rain and snow on land ordinarily are very noticeably radio-active, 

 but 1 could find no trace of radio-activity in rain water collected 

 at sea. Observations on a mountain peak in South G-ermany 

 at a height of 2954 meters at intervals throughout a year 

 showed no trace of radio-activity in the rain water collected there, 

 while it was present in that collected on the plains below, show- 

 ing that the rain must pick up its radio-activity in the lower 

 layers of the atmosphere. Observations in balloons have shown 

 that the ionization increases with the altitude, proving that the 

 ionization is not proportional to the emanation. It is a well- 

 known fact that the ultra violet rays, the Rontgen, cathode and 

 Becquerel rays are all capable of causing ionization, and it seems 

 very plausible that coming from the sun they may produce a 

 high degree of ionization in the upper regions of the atmos- 

 phere,, and, to a less degree, in the lower regions, while in the 

 lower regions the radio-active substances may add a certain 

 portion to the ionization. In this connection the investigation 

 of the problem of the spontaneous ionization of air in closed 

 vessels may be cited. Campbell and Wood, at the Cavendish 

 Laboratory, have made a long study of the subject and found 

 that air enclosed in a vessel and left undisturbed is constantly 

 being ionized and that the rate of ionization undergoes a peri- 

 odic diurnal variation with pretty well-defined maxima and 

 minima. Screening the vessel with masses of lead reduces the 



