Chap. 29.] finning of Iron. 17 r 



makes a deep black. He did net find any vegetable; 

 aftringent equal in all refpects to galls.' 



Mr. Nicholfon ftates an objection to the ufe of vine- 

 gar in the making of ink, which is, that it acts fo 

 ftrongly on the pens that they continually require 

 mending. Ink is very apt to become mouldy, which 

 is beft remedied by the addition of a few cloves re- 

 duced to powder; for hot arotnatics are excellent pre- 

 fervers of animal and vegetable matters. 



Iron detonates ftrongly with nitre. It appears to 

 combine with alkalis by fufion. The calx of iron 

 combines with earths, afiifts their fufion, and imparts 

 a green colour to the glafs. Iron has a remarkable 

 attraction for fulphur, and combines with it either by 

 the action of heat or moiftute. A mixture of equal 

 parts of iron filings and fulphur, made into a p;ifte 

 with water, becomes hot, emits watry vapours and 

 inflammable air, in a little time the mafs takes fire,* 

 and, by attracting the oxygen of the water, becomes 

 converted into green vitriol, in the fame manner as 

 pyrites. This is the mixture ufed in the production 

 of an artificial earthquake, which will be fpoken of 

 more fully under the head of earthquakes. 



With refpect to the relations of iron to the other 

 metals, there is little worthy of note, except its attrac- 

 tion for tin, on which is founded the procefs of tinning 

 iron. In fome countries iron is made into plates, by 

 being repeatedly heated and fubmitted to the action 

 of a heavy hammer. In England, however, the plates 

 are not hammered, but rolled out to the proper dimen- 

 fions, by being put between two cylinders of cafl iron, 

 cafed with fteel. When the iron plates have been 

 either hammered or rolled to a proper thicknefs, they 

 are fcoured with a weak acid, which renders their 

 furface perfectly clean and bright, and takes off all 



the 



