STUDIES IX ATMOSPHERIC ELECTRICITY. H 



observations on Mount Tsukuba during January and February, 

 1893,'^ point to similar results. There the inversion of temperature 

 ■\vns observed mainly during the night time when the sky was clear, 

 namely, when the temperature at the lower regions Avas falling very 

 low. Considering all these circumstances, I believe that it is not too 

 much to say that under normal conditions a certain layer of air, say 

 between 800 m. and 2000 m. or oOOO m., has temperature above 0°, 

 even if the temperature near tlie surface be several degrees below 0°. 



The second objection has no significance. For, if the general 

 distribution of atmospheric electricity be already determined by the 

 isothermal of 0^ and other circumstances, and if then the earth's 

 surface a7id layer of air near it be gradually cooled b}^ radiation, so 

 that the temperature sinks below 0° and there is formed a second 

 isothermal of 0"", there can be no other result than the augmentation of 

 the potential ol the air near the ground. 



EFFECT OF WIND. 



Strong wind is generally acccnnpanied by a low potential. 

 Especially when the wind is strong enough as. to raise dust in the 

 atmosphere, the potential becomes negative even under a perfectly 

 clear sky. (See Fig. 2.) It is worthy of notice that the potential 

 remains positive, however violent the wind may be, provided the 

 ground be wet with the previous précipitât iori and in consequence the 

 dust does not rise in the atmosphere. 



We may explain the phenomena by considering that the friction 

 of dust particles on terrestrial objects gives a negative charge to the 

 former and a positive to the latter, as Experiment I shows. 



The following instances are picked out of the Report. 



1) Annual Report of the Central Meteorological Observatory of Japan for the Year 1893. 

 Pt. II, p. 62. 



