596 Dr. fothergill’s Account of 
retained the magnetic virtue in a manner much more 
fixed, than either any real load-hone or any magnetic bar, 
however well tempered. In the natural ones he could 
change the poles in an inftant, fo likewife in the hardeft 
bars ; but in the compolition the poles were immoveable. 
He had feveral fmall pieces of this compolition, which 
had ftrong magnetic powers. The largeft was about half 
an inch in breadth, very little longer than broad, and 
near a quarter of an inch thick. It was not armed, but. 
the ends' were powerfully magnetic; nor could the poles 
be altered, though it was placed between two of his largeft 
bars, and they were very ftrongly impregnated. The 
mafsj was not very heavy, and had much the appearance 
of a piece of black lead, though not quite fo fhining. * I 
believe he never divulged the compolition; but, I think, 
he once told me, the bafts of it was filings of iron, re- 
duced by long-continued attrition with water to a per- 
fectly impalpable ftate, and then incorporated with fome 
pliant matter, to give it due conliftence. Perhaps fome of 
his acquaintance may have been more fully informed of 
this circumft ance ; and it may be rendering great aid to 
future enquirer's, to know every thing that can be col- 
lected relative to fo curious a fubject. 
Left the machine itfelf fhoitld again be expofed to a 
like accident with that which deftroyed a part of it, I 
thought an exact reprefentation of it, and its feveral 
parts, might be the heft means of preferving it to future 
times, if inferted in the Tranfact ions of the Royal Society. 
e x- 
