Experiments and Obftrvatiobs - if 
fecond ftroke, in which cafe either the hammer or the anvil 
touched the brafs ; I hardened a piece of brafs by beating it 
between two large flints, viz. ufing one for the hammer, and 
the* other for the anvil. The piece of brafs became magnetic,- 
though in this cafe it feemed to have acquired not fo much 
power as when it had been hardened with the hammer; bur 
it muft be obfervedj that the flints being rough and irregular, 
the piece of brafs could not be hardened by them fo eafily, or 
fo equally,, as by the other method. 
The flints, being examined both before and after the experi- 
ment,. were found to have not the leaft degree of magnetifm, 
E X P E UM E NT XV. 
A piece of brafs, which by Hammering had been rendered" 
fo ftrongly magnetic as to attract either pole of the needle from 
about a quarter of an inch, was. put into a crucible, together 
with a confiderable quantity of charcoal draft; which furrounded 
it every where. The crucible was covered with clay, and 
being put into the Are, was kept red-hot for about ten minutes. 
After cooling, the piece of brafs was taken out of the crucible^ 
and "being* examined, was found to have entirely loft its mag- 
netifm. The objedt of this experiment was to afcertain whe- 
ther the loft of magnetifm, in a piece of brafs that was* 
foftened, was owing to the calcination of the ferrugineous par- 
ticles, which, notwithstanding the preceding experiments, 
might ftill be fufpe&ed to be imparted to it ; becaufe in this" 
way of foftening - the brafs, the ferrugineous particles being 
furrounded ; with charcoal duft, could not have been calcined; 
hence the brafs ought not to have loft its magnetifm, which ~ 
was. not the. refult of the experiment, 
E X P •£.: 
