102 THE ADVANCE OF SCIENCE 



vessel; and, on this theory, the already 

 ascertained relations of gaseous bodies to 

 heat and pressure have been shown to 

 be deducible from mechanical principles. 

 Immense improvements have been effected 

 in the means of exhausting a given space 

 of its gaseous contents ; and experimenta- 

 tion on the phenomena which attend the 

 electric discharge and the action of ra- 

 diant heat, within the extremely rarefied 

 media thus produced, has yielded a great 

 number of remarkable results, some of 

 which have been made familiar to the 

 public by the Gieseler tubes and the ra- 

 diometer. Already, these investigations 

 have afforded an unexpected insight into 

 the constitution of matter and its rela- 

 tions with thermal and electric energy, 

 and they open up a vast field for future 

 inquiry into some of the deepest problems 

 of physics. Other important steps, in the 

 same direction, have been effected by in- 

 vestigations into the absorption of radiant 



