[ 776 ] 
owing to the weaknefs of magnetifm in the brafs, or 
to fome other caufe, I don’t pretend to know. 
I have tried to infufe magnetic virtue into feveral 
pieces of copper, lead and pewter ; but all my en- 
deavours have not been able to make them attiad the 
needle at all. Indeed, when I have held a piece of 
pewter, that I have tryed to make magnetical, to the 
needle, the needle would tremble* but not approach 
the pewter. 
I fend you another piece of brafs, whofe either end 
attracts either of the poles; this I have infufed the 
magnetic virtue into, and can at any time, fo as to 
attrad and repel the needle; but, like ffeel that is fet 
a low blue, it lofeth that polarity in a few hours ; 
which may arife for its being too fhort for its weight, 
or from its different temper of hardnefs or foftnefs. 
A third piece I alfo fend you, which with all my 
endeavours I cannot make attrad the needle in the 
leaf! ; and yet I can perceive no difference between 
the appearance of this piece and that of thofe which 
do. 
Would fome ingenious man purfue thefe experi- 
ments, perhaps we might have needles made of brafs 
to ad as ftrongly as ffeel ones do, which would have 
the advantage of being lefs liable to ruff at fea than 
ffeel ones are. 
But my whole defign was to fhew, that brafs is 
by no means a proper metal to make compafs-boxes 
of, or to be employed in any inffrument where mag- 
netifm is concerned. For as it is demonffrable, be- 
yond all contradidion, that fome brafs is found en- 
dued with a power of attrading the magnetic needle; 
that other pieces are capable of receiving it either by 
accident 
