= 2 
14 Second Letter from Dr. Hare to Prof. Faraday. 
they might be inferred to cooperate in the transmission of that 
species of inductive influence. But if the induction takes place 
without the ponderable matter, is it right to assume that this mat- 
ter azds because it does not prevent the effect? Might it not be as 
reasonably inferred in the case of light, that although its transmis- 
sion does not require the interposition of a pane of glass, yet that 
when such a pane is interposed, since the light is not intercepted, 
there is reason to suppose an active cooperation of the vitreous 
particles in aid of the radiation? It may be expedient here to 
advert to the fact that Prof. Henry has found a metallic plate to 
interfere with the dynamic induction of one flat helix upon an- 
other. I have myself been witness of this result. 
Does not magnetic or electrodynamic induction take place 
as well in vacuo as in pleno? Has the presence of any gas been 
found to promote or retard that species of reaction? It appears, 
that agreeably to your experiments, ponderable bodies, when 
made to intervene, did not enhance the influence in question ; 
while in some of those performed by Henry it was intercepted 
by them. Does it not follow that ponderable particles may im- 
pede, but cannot assist in this process. 
n happy to find, that among the opinions which I ex- 
ressed in my letter to you, although there are several in which 
you do not concur, there are some which you esteem of impor- 
tance, though you do not consider yourself justified in extending 
to them your sanction ; being constrained, in the present state of 
human knowledge, to hold your judgment in suspense. For the 
present, I shall here take leave of this subject, having already so 
extended my letter as to occupy too much of your valuable time. 
fam aware that as yet I have not sufficiently studied many of 
the results of your sagacity, ingenuity, and skill in experimental 
investigations. When I shall have time to make them the sub- 
ject of the careful consideration which they merit, I may venture 
to subject your patience to the additional trial resulting from some 
further commentaries. I remain, with the highest esteem, re- 
spectfully yours, Rosert Hare. 
es 
‘ae 
