McClelland am) Kknnkdv — The L-irgc Ions in the Atmosplerc. 91 



agreemeut with the results of Bloch/'' These results would suggest that 

 possibly a large proportion of the large ions ma}' be clue to such causes, and 

 that a much smaller number would be found in air at a distance from large 

 towns. On the other hand, we have frequently observed the large ions present 

 during the night and in the early hours of the morning, and, although on several 

 such occasions the air was being rapidly renewed, the numbei- present was not 

 abnormally small We hope at an early date and with a more portable form 

 of apparatus to obtain measurements at other places outside the city. 



In conclusion we may emphasize the necessity for a more careful study of 

 the action of the recording apparatus used at many stations to measure the 

 ionisation m the atmosphere, as at present it is by no means clear what is 

 being measured. 



* Sociele l'"riiiic:iise de Piiysiqiiu, 190.5, p. 4-56. 



S.I. A. PROC, VOL. XXX., SECT. A. 



[15] 



