October 14, 1898.] 



SCIENCE. 



487 



must be due to reduction of some of its glass ; and its presence in the glass, if 

 lead, probably by hydrogen evolved on proved, would be a long step toward prov- 



Chart Showing Relative Heat Conductivity of Gases. 



heating. If so, I argued that the hydro- ing the normal presence of hydrogen in the 



gen must have been absorbed from the at- atmosphere. 



mosphere since the manufacture of the Following the line of experiment thus 



