Sir W. Bamsay and Mr. F. Soddy. [Apr. 14, 



burette. The emanation, too, was collected in a tube which had been 

 used for oxygen, the object being to keep nitrogen out of the tubes, 

 and so to avoid its spectrum, which is difficult to remove. 



The gas, of which there was about half a cubic centimetre, was 

 admitted into the gas-burette through the inverted siphon A ; the 

 stop-cock being reversed, it was passed slowly into the tube B, which 

 contained a spiral of thin, partially oxidised copper wire, and which 

 had previously been exhausted ; during the introduction of the gas the 

 copper spiral was kept red-hot by a current. The water produced was 



Fig. 2. 



absorbed in the tube C, which contained phosphorus pentoxide. 

 Mercury was then admitted into B and C, so as to displace the gas 

 through the stop-cock D, which was then shut. The vacuum tube 

 P had been previously glowed out until phosphorescent. This 

 vacuum tube is represented in natural size in fig. 3 ; its capacity was 

 about one-third of that of the U-tube and accessory tubing. The 

 spectrum of carbon dioxide was alone seen. With a jar and spark-gap 

 interposed, on comparing the spectrum with the jar discharge in a 

 .similar tube containing carbon dioxide, a yellow line was visible in the 

 gas from radium, and also a bright blue line, absent in the spectrum 

 of the pure dioxide. The spectrum of helium was then thrown in 



