88 CHEMICAL AFFINITY. 



to the lungs, although it does no good to them), 

 see what happens. [The Lecturer inhaled 

 some hydrogen, and after one or two ineffectual 

 attempts, succeeded in blowing a splendid 

 bubble, which rose majestically and slowly to 

 the ceiling of the theatre, where it burst.] That 

 shows you very well how light a substance this 

 is ; for notwithstanding all the heavy bad air 

 from my lungs, and the weight of the bubble, 

 you saw how it was carried up. I want you 

 now to consider this phenomenon of weight as 

 indicating how exceedingly different particles 



Fig. 29. 

 JTydroyen. 



Platinum. 



Water 

 O 



are one from the other : and I will take as 

 illustrations these very common things, air, 



