CLASSIFICATION OF MOLECULES. 173 



The older known metals are classified in chem- 

 ical vocabularies by their original Latin names, 

 all having a terminal in um, as ferrum, iron ; 

 argentum, silver ; aurum, gold ; &c. 



To the elementary molecules of a doubtful kind 

 is given the terminal ine, as chlorine, bromine, 

 iodine, fluorine, &c. 



To designate the unions of molecules in differ- 

 ent relative proportions, Latin terms and Greek 

 numerals are used ; as protoxide, deutoxide, or 

 binoxide, &c. : the highest combining portion of 

 one kind of molecule with another is designated 

 by the prefix per ; as the /^r-oxide of iron, per- 

 oxide of hydrogen, &C. 1 



In the formation of the atmosphere, which 

 entirely covers the surface of the planet, and of 

 the waters beneath it, that cover nearly four-fifths 

 of the surface of the globe, the four most freely 

 movable and readily excitable kinds of molecules 

 are employed, on account of their superior effi- 

 ciency. 



1 The latter compound is water, united with an extra proportion of 

 oxygen ; similar to the surcharge of soda water with carbonic-acid gas. 

 A surcharge of water with molecules of oxygen is produced by bringing 

 steam into contact with particles of air in "surface condensers." This 

 excess of oxygen being set free by heat in boilers on ocean steamers, 

 where " surface condensers " are used to obtain fresh distilled water for 

 supplying the boilers, it is found that the free oxygen rapidly corrodes 

 the iron plates. This difficulty, which countervails the theoretical ad- 

 vantage of the use of fresh water in marine boilers, might probably be 

 obviated by passing the condensed water through a tube containing 

 waste chips of iron turnings, with which oxygen combines with almost 

 explosive rapidity. This may be tested by dropping iron filings into 

 water, containing a surcharge of oxygen, in the state of " peroxide of 

 hydrogen." 



