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evaporates the aqueous parts of the alum, and alfo 
renders it much lefs corrofive. The method of pre- 
paring faltpetre is the fame as that of alum j only 
the plate on which it is done muft have an upright 
rim all round it, to prevent the fait running off into 
the fire. 
In my next letter I fhall go through the method 
of differing birds and other fubjedts, and give di- 
rections for applying the varnifhand compound, with 
whatever elfe appertains to a perfedt prefervation. 
I am, with great deference and refpedt. 
Sir, and Gentlemen, 
Your moft obedient humble fervant, 
28 June, 1770. T. S. Kuckahn. 
LETTER IV. 
Sir, and Gentlemen, 
N my laft, I gave directions for prepar- 
ing the materials, which I ufe in pre- 
fervations. I fhall now proceed to defcribe the 
method of applying them. If a bird is killed by 
hand, a flop of cotton muft be put into the throat 3 
and if by fhot, into each of the (hot holes alfo, 
Vol. LX. Sf for 
