74 Mr* Cavallo's Magnetical 
in the leaft attracted by it. One of thofe grains was then 
hammered; by which means, after about eight or ten ftrokes, 
it was fpread into a plate, about a tenth of an inch in diameter, 
and nearly circular ; afterwards the magnet being prefented to 
it, the former attracted it from the diftance of about one-twen- 
tieth of an inch. The other grains being all hammered ono 
after the other, were rendered by it fo far magnetic as to be 
attrafted by the magnet, and to difturb the fufpended needle 
when they were prefented to it. But there were fome amongft 
them which acquired no magnetifm at all, though they had 
been purpofely hammered much longer than the others. 
As far as I could obferve, thofe pieces which would not ac- 
quire any magnetifm by hammering, had not a very Aiming 
appearance before the hammering, though afterwards they 
could not be diftinguifhed from the others by their appearance ; 
and they feemed not to fpread under the hammer fo eafily as the 
others. 
In general three or four ftrokes are fufficient to render a grain 
of platina evidently magnetic, but about ten ftrokes give it the 
full power it is fufceptible oft 
EXPERIMENT . IV. 
Thofe grains of platina, which in the preceding experiments 
had been rendered magnetic by hammering, being put upon a 
charcoal* were made red-hot by means of a blow-pipe ; and 
afterwards being prefented to the magnet, and likewife to the 
fufpended needle, they (hewed not the leaft fign of magnetifm. 
Heat, therefore, deprives them as well as brafs of the mag- 
netifm acquired by hammering. A fecond hammering ren- 
dered them magnetic, though not fo quickly, nor to fo great a 
3 degree, 
