= 
Second Letter Srom Dr. Hare to Prof Fara aday. 5 
‘emi which may. be considered in the one case as ordinary, i in the 
, vers extraordinary. Thus, take the case cited in your reply, = 
(viii, ix, x.) Does the interposition of the spheres alter the char- 
acter of the inductive power in the sphere A? 
Hither the force exercised by the charge in A, is like that 
of gravitation, altogether independent of the influence of inter- 
vening bodies ; or, like that of light, it is dependent on the agency 
of an ininoeerding matter. Agreeably to one doctrine, the matter, 
by means of which luminous bodies act, operates by its transmis- 
sion from the luminous surface to that illumined. Agreeably to 
another doctrine, the illuminating matter operates by its undula- 
tions. If the inductive power of electrified bodies be not anal- 
ogous to gravitation, it must be analogous to the power by which 
light is produced so far as to be dependent on intervening matter. 
But were it to resemble gravitation, like that force it would be 
uninfluenced by such matter. If your experiments prove that 
electrical induction is liable to be modified by intervening matter, 
it is demonstrated that in its mode of operation it is analogous to 
light, not to gravitation, It is then proved, that, agreeably to 
your doctrine, electrical induction requires the intervention of 
matter, but you admit that it acts across a vacuum, and of course, 
_ acts without the presence of ponderable matter. Yet it requires . 7 
intervening matter of some kind, and, that> ‘matter oe i 
— it must of necessity be imponderable. en 
1s communicated from a luminous body in the centre of an’ 
a ted sphere, agreeably to the undulatory hypothesis, its otc” 
vis de spendent on the waves excited in an intervening impondera- 
_» ble medium. Agreeably to your electropolar hypothesis, the in- 
_ ductive efficacy of an electrified body in an exhausted sphere 
would be due to a derangement of electric equilibrium, by which 
an electric state opposite to that at the centre would be produced 
at the surface of the containing sphere, (xxvi, xxvii.) This 
o case you consider as one of extraordinary induction, but when air 
is admitted into the hollow sphere, or when concentric spheres 
2 are interposed, you hold it to be a case of ordinary induction. 
. t us then, in the case of the luminous body, i imagine that con- 
centric spheres of glass are interposed, of which the surfaces are 
roughened by grinding. In consequence of the roughness thus 
produced, the rays instead of proceeding i in radii from the central 
a 
