600 The Method of Positive Rays [Jan. 17. 



power of combining with glass. I prefer to defer expressing any 

 opinion as to the actual nature of the gas until I have had the oppor- 

 tunity of making further experiments upon it. It is only about 

 two months ago that I found how to get the gas with any certainty, 

 and, as the method involves long bombardments, each experiment 

 takes a considerable time. This has prevented me from making 

 several experiments which suggest themselves, and which ought to be 

 made before coming to a final decision. I thought, however, that 

 the investigation, though incomplete, might not be unsuitable for a 

 Friday evening discourse, as the gas, whatever its nature, is certainly 

 one of considerable interest, and its detection illustrates the delicacy 

 of this new method. 



[J. J. T.] 



