y'z Mr. Cavallo v s Magnetica 1 
ehofen of fuch a fort as will not be made magnetic by hammer- 
ing, which fort however does not occur very eafily. 
Examination of the Magnetic Properties of fame other Metallic 
Subftances . 
The refult of the experiments on brafs induced me to exa- 
mine other metallic fubftances, and efpecially its components, 
«viz* copper and zinc : though the refult of the experiments has 
not been very remarkable, -excepting with platina, which metal 
has properties in great meafure analogous to thofe of brafs. 
Having examined various pieces of copper, by means of the 
fufpended magnetic needle, and having never found them mag- 
netical, except only fometimes in fuch places which had been 
filed, and where feme particles of fteel might have been left 
by the file, I next proceeded to hammer fome pieces of it, not 
only in the ufual way, but likewife between flints : the refult, 
however, was very dubious ^ for though, in general, they had 
no effe£t whatever on the needle, yet fometimes I thought the 
needle was really attracted by fome pieces of hammered copper ; 
but then this attraftive power was fo exceedingly fmall as nc)t 
to be depended upon. 
Zinc, either not hammered, or hammered as far as could be 
done without breaking it, ihewed no figns of magnetifm what- 
ever, when prefented to the magnetic needle. A mixture of 
zinc and tin neither had any adtion upon the needle. 
A piece of a broken refledlor of a telefcope, which confided 
of tin and copper ; a mixture of tin, zinc, and a little copper; 
a piece of filver, both foft and hammered; a piece of pure 
gold, both foft and hammered ; a mixture of gold and filver, 
both hard and foft ; and another mixture of a great deal of 
i filver, 
