1886.] Passage of an Electric Discharge through Nitrogen. 329 



May 6, 1886. 



Lieut.-General STRACHEY, R.E., Vice-President, in the Chair. 



In pursuance of the Statutes the names of the Candidates recom- 

 mended for election into the Society were read from the Chair as 

 follows : — 



Bidwell, Shelford, M.A. F 

 Colenso, William, F.L.S. E 

 Dixon, Harold B., F.C.S. 

 Festing, Edward Robert, Major- L 



General R.E., 

 Forsyth, Andrew Russell, M.A. 7 

 Green, Professor A. H., M.A. Y 

 Horsley, Professor Victor, F.R.C.S. 

 Lewis, T. R., M.B. Y 

 Meldola, Raphael, F.R.A.S. 



The following Papers were read : — 



Pye-Smith, Philip H., M.D. 

 Russell, Henry Chamberlaine, 

 B.A. 



Unwin, Professor W. Cawthorne, 

 B.Sc. 



Warington, Robert, F.C.S. 

 Wharton, William James Lloyd, 



Captain R.N. 

 Wilde, Henry. 



I. " On an Effect Produced by the Passage of an Electric 

 Discharge through Pure Nitrogen." By J. J. Thomson, 

 M.A., F.R.S., Fellow of Trinity College, Cavendish 

 Professor of Experimental Physics, Cambridge, and 

 R. Threlfall, B.A., Caius College, Cambridge, Professor 

 of Experimental Physics in the University of Sydney. 

 Received April 13, 1886. 



In the course of some experiments which we have been engaged 

 with for some time past, on the temporary increase in the volume of 

 a rarefied gas which takes place when an electric discharge passes 

 through it (De la Rue and Muller, "Phil. Trans.," 1880), we found 

 that the passage of the spark always produced permanent as well as 

 temporary effects when the gas was nitrogen and when the pressure 

 was less than that due to 20 mm. of mercury. The experiments 

 described below were undertaken to clear up this point, and from 

 them we have drawn the following conclusions : — 



1. That when a succession of electric sparks of the proper kind is 

 sent through a sealed discharge-tube containing nitrogen at a low 

 pressure (less than 20 mm. of mercury), a permanent diminution in 



