[ 77 + J 
CVI. AbJiraB of a Letter fr om Mr. Wil- 
liam Arderon, F.R.S. to Mr. Henry Baker, 
F. R. S. on the giving Magnet if m and 
P olarity to Brafs . Communicated by Mr. 
Baker. 
Dear Sir, 
R^d Nov. 16, T^OR fome time part I have been 
JL making experiments on the magne- 
tifrn of brafs, and amongft many pieces that I have 
tried, find feveral that readily attract the needle ; but 
whether they have had this property originally, or 
have received it by hammering, filing, clipping, or 
any other fuch-like caufe, I cannot yet determine. 
I have a very handfome compafs-box made of pure 
brafs, as far as I can judge: the needle being taken 
out, and placed upon a pin fixed properly in a board, 
and clear of all other magnetics, the box will attract 
this needle at half an inch diftance j and, if fuffered 
to touch, will draw it full 90 degrees from the north 
or fouth points j and I think thofe parts of the box 
marked north and fouth attratf: the ftrongeft. The 
cover of the box alfo attradls the needle nearly as much 
as the box itfelf. 
As to your fuppofition, that iron may be mixed 
with the bi afs, I do not know ; but I have been in- 
formed it cannot be, as brafs fluxes with a much lefs 
degree of heat than iron, and iron naturally fwims on 
fluid brafs. Befides, many of the fpecimens of brafs 
I have tried were new as they came from the mill, 
where they were wrought into plates, and I prefume 
were 
