RECORDS 79 



of the lact that in the air near dry thorium compounds a nega- 

 tively charged body, corresponding to the kathode, becomes 

 radioactive, while a positively charged body, corresponding to 

 the anode, is not made active. The activity of the anode used 

 in the electrolysis of a thorium nitrate solution can become much 

 more intense, for a given extent of surface, than that shown by 

 a thick layer of thorium oxide. 



The solution under electrolysis rapidly loses its power of im- 

 parting radioactivity, so that after four hours of electrolysis with 

 a current of half an ampere, a solution of 20 g. of thorium ni- 

 trate in 100 c.c. water had lost 95 per cent, of its power of im- 

 parting activity to the anode. This radioactivity of the anode 

 increases for a while after being taken out of the solution, then 

 its intensity falls off at the rate of half its value in eleven hours, 

 which has been shown by Professor E. Rutherford to be the 

 rate of decay in the case of surfaces made active by exposure to 

 the emanation from a dry thorium compound. The radiation 

 is not homogeneous, as is shown by a study of its absorption 

 by successive layers of metal foil. 



The activity of the anode seems to increase directly with the 

 concentration of the solution for short periods of electrolysis, 

 but its relation to the current strength and the duration of the 

 electrolysis appears to be less simple. 



Solutions containing radium impart activity to both anode 

 and kathode, but this activity decays very rapidly, falling off 

 half its value in about 35 minutes. 



S. A. Mitchell, 



Secretary of Section. 



SECTION OF BIOLOGY. 



November 10, 1902. 



The Section met at 8:15, P. M., Professor Bashford Dean 

 presiding. 



The minutes of the last meeting were read and approved. 



The Nominating Committee appointed at the October meet- 

 ing presented the following nominations : 



