METALLURGY. 263 



state of fusion. The varieties in the colour, malleability, and 

 ductility of bra-s, proceed from the quantity and quality of the 

 calnmine imbibed by the copper ; and the quality of the copper 

 itself is a circuuiitance of no small importance in the making of 

 brass. " I Inve ob-iivcd, says Dr. Lewis*, in a large set of ex- 

 periments on (his subject, that a little of the calnmine (that is, of 

 the zinc contained in the calamine) dilutes the colour of the cop. 

 per, and renders it pale ; that when (he copper has imbibed about 

 one twelfth of it's own i:;h(. the colour inclines to yellow ; fliat 

 the jellowm-s in.Tiases more and more till the proportion comes 

 almost to one-ha'f; that on further augmenting the calamine, 

 the brass becomes paler and paler, and at last white. "' As to the 

 different quili'i-s of different kinds of copper, they are suffici- 

 ently knoun to woikmen emp'oyed in fabricating it ; and philo- 

 sophers hate so far observed them, as to distinguish the different 

 sorts of copper by the different weights which appertain to equal 

 bulks of them. The lightest copper which Musschenbroeck has 

 noticed, is that which is precipitated from the copper waters 

 in Hungary ; a cubic font of this sort weighed, when melted, 

 7242 ounces : and the heaviest sort he mentions is the Japan cop. 

 per ; a cubic foot of it, when simply melted, weighed 8726 

 ounces. The difference of the weights of equal bulks of these two 

 sorts of copper is very considerable; but jet it is much less than 

 what may be observed between two specimens of the same sort of 

 copper, one of which has been cast, and the other has been 

 wrought : the same Hungarian copper, which, when barely melt, 

 ed, weighed 7242 ounces to the cubic foot, when it had been con. 

 densed by being long hammered, weighed 9020. Many of our 

 English writers estimate the weight of a cubic foot of copper at 

 9000 ounces t, but they do not say whether the copper was melt- 

 ed merely, or hammered ; nor from what mine it was procured. 

 I found the weight of a cubic foot of plate-brass from Bristol to 

 be 8441 ounces, and that of a cubic foot of. old brass from the 

 bottom of an old kettle to be 8819 ; which shews (hat it approach, 

 ed to the weight of copper, and indeed from the redness of it's ap- 

 pearance it seemed as if all the zinc had been burned away. 1 

 had a present made me of a fine celt (the antiquaries are not 



* Newman'* Chem. by Lewis, noies, p. 66. 

 i Cotes, Ferguson, Martin, Camptx II. 



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