Mr. Cav allo’s Magnetical Experiments, &c. y 
fr.fpended by means of a chain of hair; which fort of fufpen- 
lion I find not only from the experiments then made, but alfo 
by feveral fubfequent trials, to be the nimbleft hitherto con- 
trived ; becaufe tome iubdances which feem to be quite dedi- 
tute of magnetitm, by not attra&ing any of the magnetic 
needles otherwife fufpended, will fentibly affect this. How- 
ever, notwithdanding the nicety of this method for difeovering 
a very low degree of magnetic attraction, it was found dill 
inferior to that of exploring fubftances floating on the furface 
of quickfdver, as ufed by M. Brugman *. It feemed, there- 
fore, neceffary to repeat fome of thole experiments on brafs, 
and alfo upon platina, by examining their magnetifm by this 
means, viz. by putting the pieces of brafs or grains of platina 
upon the furface of quickfdver, and then prefenting a drong 
magnet near them. The refult of thofe experiments was, that 
very feldom a piece of brafs, or grain of platina, occurred, 
which was not atfetded by the magnet ; and even when they 
were not affe&ed by it, their indifference, as may be expreded, 
was not very clear and decifive ; and indeed there are very few 
fubdances in nature which, when examined by this means, 
are not in fome degree attracted by the magnet, fo general is 
the difperfion of iron, or fuch is the tendency which mod: 
bodies have towards the magnet. 
Such brafs which in the former experiments appeared to 
have no magnetifm naturally, nor to acquire any by ham- 
mering, was now found to be modly magnetic, though in fo 
very fmall a degree as to be difcoverable only when floating 
upon quickfdver. The fame was the cafe with the grains of 
platina before they were hammered ; but after hammering 
* See his Magnet ifmus, feu de Affinitatibus Magneticis, printed at Lyons in 
1778 . . . 
their. 
