JAN., 1893. CORRESPONDENCE. 79 
(Dr. DE VaRIGNY brings forward the statement that ‘‘we possess, in the facts of 
domestication,” &c., in support of his view that Professor Weismann goes too far 
when he asserts that we have no proof of the direct production of transmissible 
changes by means of external influences. As used, the sentence amounts to a single 
statement that we know many cases of variations due to environment being trans- 
mitted. 
The whole controversy to which Dr. de Varigny is alluding, concerns the state- 
ment which he brings up as an argument on one side of the controversy. 
In the matter of Le Conte, I am sorry that I attributed to Dr. de Varigny an 
approval he now disowns. He wrote (p. 229) :— 
‘What can the methods of experimental transformism be? The only answer 
to this question is based on the consideration of what the factors of evolution are, or 
are supposed to be. At the present moment five are usually recognised. I quote 
from Le Conte’s able paper of recent date.”’ 
In the two ‘‘factors’’ I quoted in my review, Le Conte runs together the 
observed facts of phylogenetic variation and phylogenetic decay of disused parts, 
with the theory that the result of the action of environment is inherited and integ- 
rated. Achief object of ‘experimental transformism”’ must be to decide on these 
theories, and any ‘‘ method” involving preliminary acceptance or rejection of them 
is valueless. 
I do not consider Dr. de Varigny’s statements heretical, but if I did it would 
be of no interest to anyone. I merely showed that they were confused. 
P.C. M.] 
THE INTERIOR OF THE EARTH. 
In the summary of my late paper in the Proc. Cambridge Phil. Soc., given in 
“Notes and Comments’’ of December, there are two points to which I wish to be 
permitted to refer. It is stated that I have ‘‘ reinvestigated mathematically”’ the 
effects of a tidal yielding of the earth on a tide of short period, according to the 
canal theory. Professor Darwin had already made that investigation, and there 
was, consequently, no need to do it over again. But he had left his result in the 
form of general symbols, and what I have done is to carry his calculation a step 
further by substituting for the symbols their known astronomical values. It was in 
this way that I arrived at a conclusion to what extent the ocean tide might be 
expected to be diminished if the interior of the earth is liquid. 
. The Reviewer has, however, given my result incorrectly in saying that I have 
found that the tide, in the case of a liquid interior, ‘‘would be about two-fifths of 
what it would be’’ in the case of the earth being solid. What I did say was, that 
it would be diminished by two-fifths if the earth was taken as homogeneous, but only 
by one-fifth when the fact is taken into account that the outer parts of the earth are 
of half the mean density. This, of course, will leave four-fifths of the height on a 
solid earth for the height ona liquid earth. For instance, if the height of the tide 
from highest to lowest on a solid earth were fifty inches, it would still be forty 
inches if the interior were liquid. Since we donot know what the exact height of the 
tide would be on a solid earth, it is perfectly possible that the tides actually expe- 
rienced may be of the height appropriate to a liquid interior, seeing the diminution 
caused by liquidity to be so small. 
On a review of the whole question, it appears to me that what had been pre- 
viously done by Lord Kelvin and Professor Darwin, and other mathematicians, had 
been to show that, unless the earth is excessively rigid, the tidal forces must deform 
it. But it had been asswmed that, if so deformed, it would carry the water up and 
down with it, so that the ocean iides would not be noticeable; but the question 
whether or not this assumption was valid, had never, so far as I know, been brought 
to the test of numbers until I made the attempt. 
O. FISHER. 
Harlton, Cambridge, December 12, 1892. 
