WITH THE CAVENDISH APPARATUS. 
229 
B 
n\Z 
might be weakened in any arbitrary degree by inclining it, or other modes of making 
the combination astatic, as for example by placing A and B (supposed equal or very 
nearly so) horizontal, and adding a 
small adjustable correcting magnet at n i— •- - I s 
C, &c. &c. &c. 
“The whole being then inclosed 
in a case, it was proposed to bring 
near to both A and B (and on oppo- A lilJ 
site sides) masses of various metals and other substances not usually considered as 
magnetic, with a view to increase by leverage and so place in evidence any very mi- 
nute magnetic forces which might reside in the substances used. 
“I think that such a course of experiments would not now be without its interest, 
and that the magnetic and diamagnetic powers of Faraday would be exhibited in 
such a course perhaps under new and remarkable light.” 
I have now only further to add, that I think it would very much conduce to our 
knowledge of the subject to make a new series of experiments with the Cavendish 
apparatus as used by Mr. Baily, but in this manner: — Carefully stating how the 
masses of balls were disposed previously to the commencement of the experiments, 
and continuing those experiments without interruption day and night by several ob- 
servers relieving each other through three or four successive days and nights, with a 
view to ascertaining the periodicity, &c. of the magnetic or diamagnetic forces. 
Of course when real magnets are attached to the rod, as I have advised when the 
object of investigation is the earth’s mean density, it would be necessary to render 
the torsion rod astatic by Sir John Herschel’s ingenious device, which, as he states, 
was contrived before he had had any knowledge of M. Nobili’s astatic combination 
of needles. 
