202 w ALL'S MANUAL 



most abundant, of elementary substances. It enters 

 into the composition of almost everything we use 

 around us. It constitutes eight-ninths the weight of 

 water, and nearly one-fifth of the air. It is an 

 abundant clement in rocks and soil, and in nearly all 

 vegetable and animal substances. The presence of 

 oxygon in the air is necessary to support combustion, 

 and, also, to sustain life. A mixture of oxygen 21 

 part?, and nitrogen 79 parts, is the air wo breathe. 

 Its action upon the soil is very beneficial, and will be 

 noticed more fully hereafter. 



Hydrogen (Symbol II ; combining weight 1). 



The name of this gas is derived from two Greek 

 words signifying "generator of water,' 7 because with 

 oxygen it forms w r ater, H, IxO, 8 or 1 part hydrogen 

 and 8 parts oxygen forms water, = 9. The union of 

 hydrogen and nitrogen forms ammonia, one of the most 

 active fertilizers known to agriculture. 



Carbon (Symbol C ; combining weight 6). 



Carbon is a very important element in nature. It 

 constitutes the greater part of both plants and 

 -inimals. It is the chief ingredient in the vast beds 

 of mineral coal. The diamond is the present form of 

 carbon. With oxygen it forms carbonic acid ; thus, 

 one part of carbon added to two parts of oxygen, or 

 C, GxO, 1622 carbonic acid, which forms somewhat 

 less than half the weight of limestone. Combustion 

 and respiration consume oxygen, arid generate 

 carbonic acid, while vegetation consumes carbonic 

 acid, and generates oxygen ; thus, the equilibrium of 

 the air is preserved in reference to these two gases. 



Nitrogen (Symbol ]S ; combining weight 14). 



This gas, as before stated, constitutes about 



