BRASS. 



intercepts more or less of the draught 

 from the furnace, as more or fewer of the 

 holes of the cover are left unstopped. 

 The crucibles are charged with the mix- 

 ed calamine and charcoal, together with 

 copper clippings and refuse bits of vari- 

 ous kinds, and sometimes brass clippings 

 also, most of which are previously melted, 

 and run into a small sunk cistern of water, 

 through a kind of cullender, which di- 

 vides the metal into globules, like shot. 

 Powdered charcoal is put over all, and the 

 crucibles are then covered and luted up 

 with a mixture of clay or loam and horse 

 dung. The time required for heating 

 the crucibles and completing the pro- 

 cess, varies considerably in different 

 works, being determined by custom, by 

 the quantity of materials, the size of the 

 crucibles, and especially the nature of the 

 Cii -; : :ine. In the great way, from 10 to 

 24 hours are required. At Holly well, in 

 Flintshire, about twenty-four hours are 

 taken. 



In the laboratory, brass may be made 

 veiy well in the small way in a short time. 

 Put into a crucible a mixture of calamine 

 and charcoal, bury it in the requisite pro- 

 portion of copper shot, cover the whole 

 with charcoal powder, lute on a cover to 

 the crucible, and heat .slowly in a wind 

 furnace for half an hour, till the zinc be- 

 gins to burn off in a blue flame round the 

 top of the crucible : then raise the fire, 

 and heat briskly for half an hour longer. 

 This process of cementation is also shown 

 by the following management. Put the 

 mixture of calamine and charcoal into a 

 crucible, cover it with a thin layer of 

 clay, over which, when dry, lay a thin 

 plate of copper, cover the whole with 

 fine charcoal powder, and lute on a co- 

 ver to the crucible. Apply heat gradu- 

 ally, and the vapour of the reduced zinc 

 will rise through the floor of clay, pene- 

 trate the red hot copper plate above it, 

 and gradually convert it into brass, which 

 at the end of the operation will be found 

 lying melted on the stratum of clay. The 

 increase of weight gained by the copper 

 in this operation will afford a good prac- 

 tical test of the goodness of the calamine, 

 and its fitness for brass-making in the 

 great way. The most important proper- 

 ties of brass, compared with copper, are 

 the following: the colour of brass is 

 much brighter, and more approaching to 

 that of gold ; it is more fusible than cop- 

 per ; less subject to rust, and to be acted 

 upon by the vast variety of substances 

 which corrode copper with so much 

 ease ; and it is equally malleable when 



cold, and more extensible than either cop- 

 per or iron, and hence is well fitted for 

 fine wire. Brass, however, is only mal- 

 leable when cold. Hammering is found 

 to give a magnetic property to brass, 

 perhaps, however, only arising from the 

 minute particles of iron beaten off the 

 hammer during the process, and forced 

 into the surface of the brass ; but this cir- 

 cumstance makes it necessary to employ 

 unhammered brass for compass-boxes, 

 and similar apparatus. The expansion of 

 brass has been very accurately determin- 

 ed, as this metal is most commonly used 

 for mathematical and astronomical instru- 

 ments, where the utmost precision is re- 

 quired. Mr Smeaton found that twelve 

 inches in length of cast brass, at 32, ex- 

 panded by 180 degrees of heat (or the 

 interval from freezing to boiling water) 

 225 ten thousandth parts of an inch. 

 Brass wire under the same circumstances 

 expanded 232 parts ; an alloy of 16 of 

 brass with one of tin expanded 229 parts. 

 The expansion of hammered copper is 

 only 204 such parts ; but that of zinc is 

 253 : so that brass holds a middle place 

 in this respect between its two compo- 

 nent metals. 



Analysis shows a vast variety in the 

 proportions of the different species of 

 brass used in commerce. In general, the 

 extremes of the highest and lowest pro- 

 portions of zinc are from 12 to 25 per 

 cent, of the brass. Even with so much as 

 25 per cent of zinc, brass, if well manu- 

 factured, is perfectly malleable, though 

 zinc itself scarcely yields to the hammer. 

 Mr. Dize analyzed a specimen of remark- 

 ably fine brass made at Geneva, for the 

 purpose of escapement wheels, and the 

 nicer parts of watch-making, the perfect 

 bars of which bear a very high price. 

 This metal unites great beauty of colour 

 to a very superior degree of ductility. It 

 was found to consist of 75 of copper with 

 25 of zinc, and probably too the copper 

 was Swedish, or some of the finer sorts. 

 The common brass of Paris seems to con- 

 tain about 13 per cent, of zinc, the Eng- 

 lish probably more. The uses of brass 

 are very numerous. It is applicable to a 

 great variety of purposes,is easily wrought 

 by casting and hammering, and by the 

 lathe ; its wire is eminently useful, and it 

 takes a high and very beautiful polish. 

 The appearance of brass is given to other 

 metals, by washing them with a yellow 

 laquer or varnish, a substitution often 

 very much to the detriment of the manu- 

 factured article. Many other yellow 

 alloys of copper are used, such as 



