INTROD.] UNORGANIZED BODIES. 5 



weather, mosses often become completely desiccated and appear 

 quite dead, but will speedily revive on the application of moisture. 

 And the common wheel animalcule,, although apparently killed by 

 the drying up of the fluid in which it had been immersed, will 

 speedily resume its active movements on being supplied anew with 

 water. 



Inorganic bodies may be resolved by ultimate analysis into 

 Oxygen, Hydrogen, Nitrogen, Carbon, and about fifty other sub- 

 stances, which Chemists regard as simple, because they appear to 

 consist of one kind of matter only ; that is to say, they have hitherto 

 resisted further decomposition. These elements unite in certain de- 

 finite proportions to form the compound inorganic substances. And 

 this union may consist either of two simple elements as oxygen 

 and hydrogen, to form water; oxygen and the metal sodium, to 

 form soda ; chlorine and sodium, to form common salt ; or, of 

 one binary compound with another similar one, as of sulphuric acid 

 (sulphur + oxygen) with soda (sodium + oxygen), to form sulphate 

 of soda; or, again, of two such salts as the last with one another, 

 as alum, which consists of sulphate of alumina united with sulphate 

 of potassa. 



As regards the mode of combination in the first of the examples 

 enumerated in the preceding paragraph, where single equivalents 

 of the elementary bodies unite, there can be but one opinion. In 

 the formation of water, one equivalent of hydrogen combines di- 

 rectly with one equivalent of oxygen. But when one equivalent of 

 one element is united with two or more of the other, to form the 

 compound substance, the mode of combination is not so evident. 

 Peroxide of hydrogen, for example, may either result from the 

 direct combination of one equivalent of hydrogen with two of 

 oxygen, or it may be a compound of one equivalent of water with 

 one of oxygen. 



In the second example, in which two binary compounds unite 

 to form a salt, two modes of constitution have been suggested. The 

 first supposes a direct union of a basic oxide with an acid oxide, 

 as of soda (sodium -f oxygen) with sulphuric acid (sulphur + 

 oxygen) in sulphate of soda; and that each constituent preserves 

 its proper nature in the compound. According to the second view, 

 one of the constituents of the salt is supposed to undergo decom- 

 position, yielding up to the other an element, which, joined to it, 

 forms a compound radicle, to which the remaining element is united ; 

 as hydrogen would be to a simple, or compound radicle (chlorine or 

 cyanogen), to form a hydro-acid. Thus, in the salt commonly 



