THE GROWTH OF OUR KNOWLEDGE OF HELIUM. 283 



EFFECTS OF DIFFUSION. 



A diffusion experiment described in their paper enabled 

 Messrs. Runge and Paschen to go a stage farther, and to 



x 



a 



<-$ w w TJ 



announce that of their two constituents the gas-giving D 3 

 was the heavier one. They also add :— 



" From the fact that the second set of series is on the 



