48o Mr, Babbage and Mr, Herschel's account of the 
for copper and antimony, the proportional intensity of mag- 
netic action for each respectively will be 
Zinc 
1.11 
Copper 
1.00 
Tin 
0.51 
Lead - - - 
0.25 
Antimony - 
0.01 
The smallness of the number for antimony is here also 
very remarkable. That for bismuth deduced by this means 
would be still more minute, so small indeed that the torsion 
of the thread would not allow of its magnitude being fairly 
determined, the suspended system merely performing exten- 
sive oscillations in very long times. 
18. This method however requires us to operate on very 
considerable quantities of the substances under examination, 
a great disadvantage, as it cannot be applied to the scarcer 
metals, and does not admit of the use of the common ones in 
a state of rigorous purity. A method at once more simple 
and expeditious, and allowing of our acting on small quan- 
tities of matter, is to suspend portions of the different bodies 
we would try, similar in form and exactly equal in size, over 
the revolving magnet, and noting either, dynamically the 
times of successive revolutions, or, statically the point of equili- 
brium between the rotatory force and the torsion of the string. 
This method we pursued in a very interesting part of the 
enquiry, viz. in investigating (after M. Arago) the effect of a 
solution of continuity, partial or total in the mass acted on. 
19. A disc of lead of 2 inches in diameter and ^ thick, 
was suspended in a small thin wooden tray at a given distance 
from the horse-shoe magnet, revolving with the usual velo- 
