[ 6 3 
III. Magnetical Experiments and Obfervations. 
By Mr . Tiberius Cavallo, F . R. S. 
The Le&ure founded by the late Henry Baker, Efq. F.R. 3 . 
Read Nov. 1 6, 1 786. 
T HE Bakerian Le&ure, which laft year I had the honour 
to deliver to the Royal Society, contained the account of 
fome magnetical experiments, particularly concerning the mag- 
netifm of brafs, from which it appeared, that moft brafs be- 
comes magnetic, fo far as to attract the magnetic needle, by 
being hammered, and lofes its magnetifm by annealing or 
foftening in the fire ; but that there is fome brafs, which pof- 
feffes no magnetifm naturally, nor acquires any by ham- 
mering. 
Several experiments, made fince the reading of that paper, 
having fhewn a few particulars, which tend to correct what 
was advanced in the faid Paper, I fhall in the prefent le&ure 
mention, fird:, thofe particulars, and fhall then proceed to 
relate other experiments and obfervations relating to other 
branches of the fame fubjeft of magnetifm. 
In performing the experiments on the magnetifm of brafs, 
I generally ufed a magnetic needle fufpended in a peculiar 
manner, as it is defcribed in my laft: le£ture ; viz. a common 
fewing needle, or a piece of Reel wire rendered magnetic, and 
fufpended 
