36 AMERICAN MANURES. 



liancy and rapidity. Some substances unite 

 with oxygen at the common temperature, as is 

 the case of the rusting of iron when moisture is 

 present. Oxygen unites with all the elements 

 entering into the composition of plants, in one 

 or several proportions, as in the following sub- 

 stances, viz : One equivalent of calcium unites 

 with one equivalent of oxygen to form oxide 

 of calcium, commonly called quicklime; one 

 equivalent of sulphur unites with three equiva- 

 lents of oxygen to form anhydrous sulphuric acid. 

 One equivalent of phosphorus unites with five 

 equivalents of oxygen to form anhydrous phos- 

 phoric acid. 



Mechanically mixed with nitrogen, oxj^gen 

 forms about 21 per cent, by volume of the 

 atmosphere, and is heavier than common air in 

 the proportion of 11 to 10. Much more than one 

 half of the weight of plants and animals is 

 oxygen. How wonderful, that a gas should by 

 powerful affinities be bound up in such vast 

 stores in rocks and the solid mountains of the 

 earth, as well as in the ocean, pervading all 

 created matter, and being itself the essence of 

 life; and that without it, plants and animals 

 would speedily die. 



Oxygen serves both as material for the 

 production of matter in combining with other 

 substances, as with carbon, forming carbonic 



