( 718 ) 



Two further questions connected with those views and perhaps 

 liable also to be answered by way of experiment, are these: 



1. whether the air molecules on the outside of the aluminium 

 window of Lenard emit R.-rays in appreciable quantity; 



2. whether the y-rays of a radio-active substance, except by the 

 substance itself, are to a considerable extent emitted also by the 

 atoms of air in its neighbourhood on their being pierced by the 

 electrons constituting the /J-rays. 



Physics. — "On the motion of a metal loir e through a piece of ice." 

 By Dr. J. H. Meerburg. (Communicated by Prof. H. A. Lorentz). 



(Communicated in the meeting of January 26, 1907). 



During the last and the preceding winter I made some measurements 

 with a purpose of testiug the formulae, expressing the velocity 

 of descent of a metal wire through a block of ice, which Mr. L. S. 

 Ornstein had derived from the theory of regelation J ). 



■Ï-I-I-H-I-'I" 



** 



In my experiments the metal wire was fastened at both ends to 



l ) L. S. Ornstein. These Proc. VIII, p. 653. 



