PUIIIFIC-ATION OF COPPER-. 101 



The hiftory and tletailofmanufadlories condudledinead^ place Sorr.e objetlloni 

 ought, I prefame, loform a principal object with the writers of'^" ^^'"'^^'* 

 local liifiories ; yet very few of tbofe gentlemen are enabled to 

 obtain fuch accounts as they can depend on, from the felfifh 

 and monopolizing jealoufy of manufacturers in general. To 

 thcfe various advantages an obje^lion may be offered, ** That 

 difplay is placing objeds of taxation in the hands of niinifters : 

 be it fo; difplay will make it eafier to colled the tax, will 

 make it more certain, and it may be, lejs opprejjive : if to 

 thefe be added the above advantages, it may fairly be pre- 

 fumed, that difcovery and confequent improvement is the 

 moft advan:ageous track to be purfued ; but, my dear Sir, I 

 beg your pardon, on this fubjeCl I did not mean to offer my 

 own opinion fo much as to folicit information from that of 

 others. 



I am truly your*s, 



JOHN CLENNELL. 



How far literary purfuits are compatible with the duties ofl/iterarypurfuits 



{he commercial man, or the manufadurer, feems a queftion ^^^ /^""^P^,^'^'^ 



1 with the duties 



fo completely decided in the affirmative, in the firft volume of of merchants and 

 the Manchefler Memoirs, by Mr. Henry ; in the lecond volume nunufafturers, 

 of the fame work, by Dr. Barnes; and in the hundredth num- 

 ber of the Lounger, — that the above paper aifumes the prin- 

 ciple as being fully eflablifhed. J. C. 



X. 



Sueftiori refpeSiing the Purification of Copper. By ]. P. With 

 a concije Reply. W. N. 



Jt\S copper in its purefl flate (efpecially out of London) for Qiieftion re- 

 raanufadurine: different articles, cannot be obtained without ^P^'^'fS ^^'^ I"** 



,. ° - . r I • • I • T • riiication of cop- 



a very tedious procels j as it forms the principal ingredient in per. 

 mirrors for refiefting telefcopes, and likewife is much ufed 

 'as an alloy for gold ; if it is impure, it never fails to render 

 the gold fo alloyed brittle, and not to be reftored to its duc- 

 tility until the impure alloy be wafled by fubfequent meltings, 

 to the lofs and difeppointmcnt of the workman. Required, 



therefore. 



