l6o Natural Properties 'of Iron. [Book VI. 



argument againft the abfurd and ignorant hypothefis 

 of the eternity of the world. 



The external appearance of this metal is well known* 

 and its hardnefs and elafticity are feen in the various 

 inftruments and utenfils which are formed of it. 



It is the moft fonorous of all the metals, except 

 copper j but in fpecific gravity it is inferior to moft of 

 them, being only about feven times and a half the weight 

 of water. Iron has a considerable finely efpecially when 

 rubbed or heated. It like wife has a very perceptible 

 ftyptic tafte. 



Iron is very ductile, and may be drawn into wire as 

 fine as a human hair ; and it is fo tenacious, that an iron 

 wire of one tenth of an inch diameter will fupport a 

 weight of fifteen hundred pounds. Iron may be ig- 

 nited, or at leaft made fufficiently hot to fet fire to 

 brimftone, by a quick fuccefllon of blows with a ham- 

 mer j but it requires a moft intenfe heat to fufe it, on 

 which account it is brought into fhape by hammering 

 while it is in a heated ftatc. Iron is alfo poflefled of 

 another property, which fupplies in a great meafure 

 the purpofes of fufion. When pieces of common foft 

 iron are heated to a certain degree, and are fuddenly 

 taken out of the furnace and expofed to the air, we 

 obferve their furface covered over with an appearance 

 of varnifh, which proceeds from the furface of the 

 metal being partly fufed. If two pieces of iron in this 

 ftate are ftruck together, they unite very firmly, and 

 this procefs is called welding. It is diftinguiftted from 

 all other metals by being attracted by the loadftone. 

 Another property, which diftinguifhes iron from ail 

 other metals, is that of ftriking fire with flint. This 

 phenomenon depends oh the actual inflammation of 

 fmall particles of the metal, which prefent a large fur- 

 face to the action of the air, and which are heated by 



the 



