450 



Prof. J. C. Bose. On the Periodicity in 



11. " The Electrical Effects of Light upon Green Leaves. (Prelimi- 

 nary Communication.)" By A. D. Waller, M.D., F.R.S. 



IIL " The Nature and Origin of the Poison of Egyptian Lotus (Lotm 

 arahims):' By W. R Dunstan, F.R.S., and T. A. Henry. 



IV. " The Exact Histological Localisation of the Visual Area of the 

 Human Cerebral Cortex." By Dr. J. S. Bolton. Communi- 

 cated by Dr. Mott, F.E.S. 



V. " Data for the Problem of Evolution in Man. V. — On the Corre- 

 lation between Duration of Life and the Number of Offspring." 

 By Miss M. Beeton, G. U. Yule, and K. Pearson, F.E.S. 



VL " The Diffusion of Ions produced in Air by the Action of a Radio- 

 active Substance, Ultra-violet Light, and Point Discharges." 

 By J. S. Townsend. Communicated by Professor J. J. 

 Thomson, F.R.S. 



VII. " On an Artificial Retina, and on a Theory of Vision." By 

 Professor J. Chunder Bose, F.R.S. Communicated by Lord 

 Rayleigh, F.R.S. 



" On the Periodicity in the Electric Touch of Chemical Elements. 

 Preliminary Notice." By Jagadis Chunder Bose, M.A., D.Sc, 

 Professor of Physical Science, Presidency College, Calcutta. 

 Communicated by Lord Rayleigh, F.R.S. Received Decem- 

 ber 6, 1899,— Read January 25, 1900. 



In my previous communication"^ an account was given of the con- 

 tact sensitiveness of elementary substances to electric radiation. It 

 was shown that though many substances exhibit a diminution of con- 

 tact resistance, there are others, of which potassium may be taken as 

 an example, which show an increase of resistance — an increase which, 

 in some cases, lasts during the impact of electric waves, the sensitive 

 element quickly recovering on the cessation of radiation. There are 

 thus produced two opposite effects, which depend on the nature of 

 sensitive substance. 



As the normal action of radiation is to produce opposite effects on 

 the two classes of substances, it would be advisable, in order to avoid 

 confusion, to use a simple term to indicate these actions, and to dis- 

 tinguish them from one another, by calling the one positive and the 

 other negative. The sensitiveness is found confined to the outer 

 surfaces in contact, and not extended to the substratum ; I have there- 



* " Ou a 8elf-recovering Colierer, and the Study of Cohering Action of different 

 Metals," ' Roy. Soc. Proc.,' vol. 05. 



