TINNING, PLATING, &C. 307 



trappings of horses, metals, which their ancestors could not use in 

 drinking vessels, without being astonished at their own prodigality : 

 we are not yet, however, arrived at the extravagance of Nero and 

 his wife, who shod their favourite horses with gold and silver. 



Pliny mentions an experiment as characteristic of tin that when 

 melted and pouted upon paper, it seemed to break the paper by 

 its weight, rather than by its heat; and Aristotle, long before 

 Pliny, bad remarked the small degree of heat which was requisite 

 to fuse Celtic (British) tin.* This metal melts with less heat than 

 any other simple metallic substance, except quicksilver ; it re- 

 quiring for its fusion not twice the heat in which water boils ; but 

 compositions of tin and lead, which are used in tinning, melt with 

 a still less degree of heat, than what is requisite to melt simple lin : 

 and a mixture composed of 5 parts of lead, 3 of tin, and 8 of bis. 

 muth, though solid in the heat of the atmosphere, melts with a 

 less degree of heat, than that in which water boils. 



[Watson's Chemical Essays. 



SECTION I. 

 Of tinning iron Of plating, and gilding copper. 



IBON is tinned in a different manner from copper. In some foreign 

 countries, particularly in France, Bohemia, and Sweden, the iron, 

 plates, which are to be tinned, are put under a heavy hammer which 

 gives in some works, 76 strokes in a minute : they can in one 

 week, with one hammer, fabricate 43-20 plates ; the iron is heated 

 hi a furnace eight times, and put eight times under the hammer 

 during the operation, and it loses near an eighth part of its 

 weight. Iron and copper are both of them very apt to be scaled 

 by being heated, and they thereby lose greatly of their weight. 

 Twenty.four hundred weight of pure plate copper will not, when 

 manufactured into tea-kettles, pans, &c. give above twenty- 

 three hundred weight. Twenty one hundred weight of bar iron 

 will give a ton, when split into rods; but taking into consideration 

 all iron and steel wares, from a needle to an anchor, it is estimated 

 that thirty hundred of bar iron will, at an average, yield a ton of 

 wares. + '''''___ 



DeMirab. 



t See an instrucfiTe pamphlrt, intitled, A Reply to Sir L. O'Briea, by W. 



Gibbooi, 1785. 



x 2 



