266 
Dr . ingenhousz on Air . 
bable, becaufe thofe very particles, which had acquired 
by electricity their increafed magnetical force, did lofe it 
again after being heated upon a piece of charcoal, which did 
not happen in the particles of iron. Platina mixed with 
lead w r as put upon an ordinary cupel in a docimaftic fur- 
nace itrongly heated. When the metal came to a folid 
ftate, it was a flat rough lump, much heavier than the 
crude platina . I put frefh lead to it, and cupelled it 
again as before. I repeated it ten times, when I obtained 
a large lump, fomewhat lefs flat, pretty fmooth, but not 
bright; of about the fame weight as after the firit cupel- 
latiom*;. This lump did not give the lead flgn of mag- 
netifm, and even would not receive any by being applied 
to ftrong magnetical bars (I forgot to try this after the 
firft cupellation) and the fubftance was very brittle, nearly 
of the fame colour as platina , and took a fine polifh. If 
it could tend to any ufeful purpofe, I would repeat thele 
experiments oftener, to be quite fure whether the event 
would be conftantly the fame. 
Though a piece of loft iron attracts the two poles of 
a compafs indifcriminately, and is incapable of acquiring 
polarity itfelf, yet I have never been able to feparate a 
Angle particle of the fofteft iron, even when I fepa- 
rated it carefully with a flint, or other body containing 
no fteel or iron, without its giving evident figns of two 
diftinCt poles when floating upon water, nay even upon 
paper. I could alfo never find iron filings of ever lo loft 
(b) I loft the paper that contained the exa& weight before and after the cu- 
pcllation. 
a fubfiancc, 
