COMPOSITION OF WATER. 51 



Condensed by the contact of the colder air, which 

 deprives it of the heat necessary to keep it in a state 

 of vapor (43, 73). 



67. The consideration of these facts makes the com- 

 position of water appear far less wonderful; for we 

 have little difficulty in believing that steam is com- 

 posed of two gases, and we know that steam, water, 

 and ice, are, chemically speaking, the same. 



68. One element of water is oxygen gas (28), that 

 part of the air which is so essential to life and com- 

 bustion : it constitutes eight-ninths of the weight of 

 ice, water, and steam. One thousand parts of water, 

 therefore, consist of 



889 parts of Oxygen 

 111 " Hydrogen 



1000 " Water. 



69. The other element, or the remaining one-ninth, 

 is called hydrogen gas, or inflammable air, because 

 it is very combustible, being the basis of the common 

 coal gas used for lighting the streets, and entering 

 into the composition of the inflammable air or fire- 

 damp of mines, and many other combustible sub- 

 stances (82). 



70. Water is not, like common air, a mere mixture 

 of two gases: it is a compound, and therefore is quite 

 different in its properties from either of its two ele- 

 ments. The very inflammable gas, hydrogen, having 

 combined with a certain quantity of oxygen, which 



