3°6 
Correspondence . 
[May, 
be found out might have been death ; and so with Zq rbi, of 
Verona ; Berenger, of Carpi ; and the great Vesalius, later on, 
whose students used to go and dig up their ghastly objedts from 
their graves, and steal at midnight, tumbling back with their 
loathsome burdens. — I am, &c., 
D. Y. C. 
Leeds. 
FISHER’S “ PHYSICS OF THE EARTH’S CRUST.” 
(“Journal of Science,” No. XCIX., March, 1882, p. 168.) 
7 'o the Editor of The Journal of Science, 
Sir, — The Reviewer states that “ an attempt has been made by 
an eminent authority to fix a maximum limit for the time which 
has elapsed from the solidification of the Earth’s surface down 
to the present day,” and adds that “ the results reached . . . vary 
from 33 to 300 million years.” The period of 33 million years is 
one obtained, not by the “ eminent authority,” but on his hypo- 
thesis, with the assumption of a lower temperature of solidifica- 
tion, by Mr Fisher (“ Physics of the Earth’s Crust,” note, p. 71). 
It appears from the Review as if Mr. Fisher attributes to Sir W. 
Thomson the conclusion that the rate of increase of the temper- 
ature within the Earth becomes nil at about 5000 feet below the 
surface. This is not Sir W. Thomson’s conclusion, but Prof. 
Mohr’s, and was deduced by him from an erroneous method of 
interpreting the Sperenberg observations (“Physics of the Earth’s 
Crust,” p. 12). Sir W. Thomson states, on the contrary, that 
the increase will not diminish sensibly for 100,000 feet or so. 
(“ Secular Cooling of the Earth,” Nat. Phil., p. 720). 
Thirdly, the Reviewer has attributed to Prof. Tait a passage 
quoted by Mr. Fisher from a trad! by the Bishop of Carlisle, in 
which the concluding clause alone is taken by the Bishop from 
Prof. Tait (“ Physics of the Earth’s Crust,” note, p. 74). 
