Mr. Cay allots Magnetlcal 
-jpp 
EXPERIMENT V. 
One* of thofe pieces of brafs which had been ufed for the 
foregoing experiments, and which had been deprived of mag- 
netifm by fire, was hammered between two large and pretty 
thick pieces of copper, which were not in the leaft magnetic ; 
and, after a few ftrokes lof the hammer, it became fenfibly 
magnetic* 
EXPERIMENT VI. 
In order to examine the difference of this property in brafs of 
various kinds, I have tried a great many pieces of Englifh as 
well as foreign brafs ; fome of which was very old, and fo 
fine and uniform, that an eminent watch-maker of my ac- 
quaintance ufed it for the very beft fort of watch work. But 
I find, that they moftly have the property of becoming mag- 
netic by hammering, and of lofing that power when foftened. 
There are, however, fome pieces which acquire no magnetifm 
by the hammering, though they are rendered equally hard by 
it as thofe which acquire the magnetifm. By attentively exa- 
mining them, I have not yet been able to diftinguifh, without a 
trial, which pieces are capable of acquiring magnetifm, and 
which not ; the colour, apparent texture, and degree of ducti- 
lity feeming to afford no fure indication. In fhort, what I have 
obferved relating to the magnetic properties of brafs is : 
i ft, That moft brafs becomes magnetic by hammering, and 
lofes the magnetifm by annealing or foftening in the fire. 
idly, That the acquired magnetifm is not owing to particles 
o£ iron of fteel imparted to the brafs by the tools employed. 
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