Brass . 
n 
will be dissipated. This is a very large proportion of 
sine, and would form what is called Prince Rupert’s me* 
tab 
The following observations of Bishop Watson, are- 
worth attention. 
The calamine of Bohemia contains iron :■ most of our 
English calamine contains lead ; and there are some sorts 
which contain both iron and lead, and other metals in dif- 
ferent proportions : these sorts can seldom be freed from 
the extraneous metals, and hence, in the ordinary method 
of making brass, they will be mixed with it, being fusible 
in the degree of heat usually employed in making brass,, 
Cramer mentions, a very ingenious method of making 
brass, by which, if it should be thought necessary to do it, 
the brass may be preserved pure from these heterogene- 
ous mixtures. He orders the calamine and charcoal to 
be mixed with moistened clay, and rammed to the bot- 
tom of the melting pot, and the copper mixed with char- 
coal to be placed upon the clay ; then, the proper degree 
of heat being applied, the vapour of the zinc contained in 
the calamine will ascend through the clay, and attach itself 
to the copper, but the iron, or lead contained in the cala- 
mine, not being volatile, will remain in the clay, and the 
brass when the whole is melted will not be mixed with 
them, but rest pure on the surface of the clay. Mr. John 
Champion , brother to him who first established the manu- 
factory of zinc at Bristol, is a very ingenious metallurgist, 
and he has lately obtained a patent for making brass by 
combining zinc in vapour with heated copper plates, and 
the brass is said to be very fine ; whether the process he 
uses has any correspondence with this mentioned by Cra- 
mer, or not, his brass will certainly be free from the mix- 
ture of lead, foe. But the care to purify brass from such 
metallic mixtures as may be accidentally contained in the 
calamine, is, or is not necessary, according to the purposes 
