The Chairman. — The action is quantitative. The question is, is the 
force quantitative ? 
Mr. Challis. — I do not think there is any ground of objection there. The 
action of gravity, as due to the ether, is a step beyond the action measured 
experimentally. 
The Chairman. — Then, with regard to the idea that is expressed in this 
paper, — with regard to the force being entirely due to the ether, — it seems 
to me the idea conveyed is that, in gravitation, the tendency of bodies to 
fall together in consequence of the force of gravitation, depends, not on the 
bodies themselves, but on their being pushed against each other by the force 
of this hypothetical ether. This appears to me the gist of the hypothesis. 
Mr. Challis. — It results from the application of mathematics to that 
ether, as it is defined. 
The Chairman. — The difficulty appears to me that, granting that ether, 
and granting these molecules impinging in countless multitudes and with 
immense velocity upon the particles of matter, I do not see why they should 
impinge on one side more than another ; and if they impinge on all sides 
alike, it seems to me that would have no effect at all. I do not see why the 
supposed impact of molecules should tend to bring the particles together. 
Rev. J. Fisher, D.D. — Professor Challis has made some good points against 
the authors of the Unseen Universe. I think the three hypotheses which he 
lays down as the foundation of a general physical theory are all sound and 
good. With regard to the atom, although we have never seen one and 
never shall, his argument is of the highest degree of probability. Then as 
to his different classes of facts, physical science consisting not only in 
experiment but reasoning, the one giving laws, the other reasoning from 
laws, I think that is a point he brings out very clearly. As to the 
two classes of fact, primary and derivative, I think that is very clear and 
plain ; as also are a great many other points. There are some things at 
the end of the paper with which I do not fully agree ; for instance, where he 
says he leaves those who do not like his argument to prove the negative. 
Now we cannot call upon any one to prove a negative. The name of the essay 
is “ On the Indestructibility of Matter.” But he has only one sentence 
about that, while he goes on to prove the creation of matter. Having done 
that satisfactorily, he says the other is of small importance. He has proved 
the creation, and it is very good proof too, but I think he would have done 
well to have brought out the other a little more clearly. 
A Visitor. — I think there is one point of considerable importance which 
has not been touched upon. Professor Challis says in his paper, 
“ If the foregoing course of reasoning has sufficed to certify that matter 
must have come into existence by the will and operation of a personal and 
intelligent Creator, by the same reasoning it is proved that matter is de- 
structible, inasmuch as a power that created it can destroy it.” 
I think we should agree with this. I think it is the main argument 
of the paper, that matter does possess what the Professor calls primary 
qualities, which are being impressed upon it in a way we cannot account 
