28 
The Chairman (0. Brooke, Esq., M.D., F.R.S,). — I am sure that we all 
u nite in returning our best thanks to Professor Birks for the very able paper 
which he has read.* It is now open for those present to make observations 
thereon. 
Rev. Prebendary Currey, D.D. — I feel incompetent to enter upon the 
details of the arguments which have just been presented to us with reference to 
the special theories which Professor Birks has discussed ; in fact, the accumula- 
tion of scientific research and of learning in his paper has been so great as 
wholly to bewilder me. But what I want to point out is this, that the ques- 
tion before us is “ modern cosmogonies examined in their bearing upon the 
antiquity of man,” and I confess that to me it is very difficult to under- 
stand what bearing a great deal of this paper has upon the subject of 
the antiquity of man. Let us suppose for a moment that all the conclu- 
sions which Professor Birks seeks to set up are clearly established, and 
that all the theories which he attacks are completely overthrown, still, in my 
opinion, that would not affect the question of the antiquity of man. All that 
it would do would be to show us that certain theories put forward by par- 
ticular philosophers are liable to exception, and are, perhaps, unsound ; but it 
would not necessarily follow that other theories may not be quite sound. The 
destruction of each theory can only affect such others as proceed upon similar 
lines ; and even those only so far as they concern the subject in hand. 
Professor Birks’s arguments have to do with the antiquity of the earth, rather 
than with that of man. Now if you can prove that certain strata, containing 
the remains of man, are not so old as has been represented, you may make 
it probable that man has not been so old an inhabitant of the earth as 
some suppose. The paper does not refer to any special antiquity of man, 
* Since the meeting Mr. Brooke has sent the following observations, 
which he intended to have made towards the close of the discussion : — 
“ I wished to have made a remark, had time permitted, on § 13 of Pro- 
fessor Birks’s paper. I cannot see that, ‘ the hypothesis that the heat trans- 
ferred from a hot to a cool body is strictly as the difference of their tem- 
peratures, and that the temperature is the quotient of the heat in any body 
divided by the mass,’ implies the corpuscular theory of heat. Speaking 
logically, it must be borne in mind that heat has no objective existence ; it is a 
subjective impression on the organs of sensation produced by certain molecular 
wave-motions. If we now suppose two contiguous particles of different bodies 
to be affected by different amounts of wave-motion, and that the whole motion 
be then shared between them, it is clear that one must have gained, and tho 
other lost half the difference ; which is the same thing as saying that the amount 
of heat transferred is as the difference of the temperatures of two bodies. 
It also appears to me equally clear that if a given amount of heat wave- 
motion, distributed through a given number of particles, be shared with an 
equal number previously at rest, each particle of the whole will have half 
tho wave-motion that previously affected each of tho first-mentioned par- 
ticles : this amounts to the same thing as saying that the temperature is the 
quotient of the heat in any body divided by the mass. It therefore appears 
to me that the matter-theory of heat is not involved, as stated by Pro- 
fessor Birks.” 
