EFFECT OF TROPICAL SUNLIGHT ON THE ATMOSPHERE. 275 



from land to places on mid-ocean before the activity is materially de- 

 creased. 



Boltzmann ls made daily observations on a voyage from Dover to New York, 

 xVugust 21 to 31, 1904. He found that the value of the ionization of the air 

 over the ocean does not differ materially from that which obtains in Germany, 

 Lapland, or Canada. Eve, 10 on a voyage from Montreal to Liverpool, June 21 

 to 30, obtained practically the same ionization of the air for the ocean as for 

 that over the land. He thinks the results may be due to air blown out to sea 

 from the land, and to a slower recombination of ions over the ocean, due to a 

 lesser quantity of dust particles in the air, but he admits that this explanation 

 is not adequate to account for the facts. 



From this evidence and from my own work I consider that other 

 factors, which I have outlined above, must be taken into consideration 

 in accounting for the ionization of the atmosphere. There is no question, 

 from the immense amount of experimental evidence gathered in the last 

 few years, but that radioactive substances do play a considerable role in 

 ionizing the air, but I do not consider that such radioactive processes 

 account for the whole phenomenon of the ionization of the atmosphere. 

 Quantites of experimental evidence are continually being brought forward 

 to prove that ions are given off in many chemical and physical processes 

 other than those known distinctively as radioactive, and such facts would 

 naturally be expected from the electronic constitution of matter. 



In connection with the work on the ionization of the atmosphere, I have 

 tested a number of substances from the Philippines to obtain an idea of 

 the distribution of radioactive substances in this part of the world. In 

 working with solids, one metal can was used in which the normal loss 

 of potential was 4 to 5 volts per hour. With liquids, another can was 

 employed in which the normal loss was 7 to 9 volts per hour. "When 

 testing various substances, losses greater than these amounts were con- 

 sidered to indicate- radioactivity. The results are given below. 



1. One liter of water obtained from the boiling lake of the crater of Taal 



Volcano. The water has stood in the laboratory in a tightly stoppered bottle for 



about two years. 



Time. Volts 



(p.m.) Volts. per hour. 



1.16 169.91 



146 



1.26 145.5] 



1.36 140.1 32.4 



2.21 131.8 10.4 



The water is active. 



2. One liter of Manila hydrant water drawn from a tap in the laboratory 

 February 3 and immediately tested. 



Time. 





Volts 



(p. m.) 



Volts. 



per hour 



3.15 



159.31 





3.25 



147.91 



68 



Phys. Ztschr. (1905), 6, 132. 

 Phil. Mag. (1907) (6), 13, 248. 



