PART II -THE AIR. 



" THE FIRMAMENT SHOWETH HIS HANDIWORK." 



CHAPTEE I. 



ITS PHYSICAL CONSTITUTION. 



WE who have been for so long a time with 

 our thoughts directed earthward, must now turn 

 them toward the sky, and look into the che- 

 mical mysteries of the blue heaven above us. 

 Can chemistry inform us, then, upon the 

 changes which take place in the invisible sea 

 of matter which on every side surrounds us? 

 We might suppose it could not, for we can 

 scarcely appreciate by any of our senses the 

 presence of this amazingly thin and transparent 

 fluid the air. Yet the chemistry of creation, 

 thanks to the well-directed labours of talented 

 men, so far as it relates to the air, is more exact 

 and complete in its information, than in any 

 other of its departments. It is expedient, 

 however, before we listen to the wonders of 



