274 Archdeacon Pratt on the Solidity and 
just as before. The irrationality is merely one of form*, What 
then? In the place of an objection to my method, has sprung 
up a verification of it. 
All Mr. Cockle’s other objections tend, in like manner, by 
their failure, only to make more palpable the validity of the 
method to which they are opposed. But of these hereafter. 
March 1860. 
XXXVI. Js the Problem, “ How far is the mass of the earth solid - 
and how far fluid?” excluded from the domain of positive 
Science? By the Venerable Joun Henry Pratt, Arch- 
deacon of Calcutta. 
To the Editors of the Philosophical Magazine and Journal. 
GENTLEMEN, 
fl me question I have placed at the head of this paper, Prof. 
Haughton has answered in the affirmative in his paper in 
the Transactions of the Royal Irish Academy, vol. xxi. p. 251, 
“ Qn the Original and Actual Fluidity of the Earth and Planets.” 
If this conclusion be correct, it must render altogether useless 
such investigations as that by Mr. Hopkins regarding the thick- 
ness of the earth’s crust. This consideration invests Professor 
Haughton’s conclusion with so much importance, that it demands 
attentive examination. It was upon this ground that I pointed 
out in your Number for May 1859, what I conceived to be—and 
still conceive to be—a fallacy in the reasoning which brought out 
this conclusion. In his last paper, in your Number for December, 
which reached me yesterday, Professor Haughton does not, n my 
view, clear away the difficulty. 
2. In his original communication to the Irish Academy he 
deduces the following equation (I here use his own notation) :— 
e(* 2 1% d.ae_ a? te Re ("pat 
AN sal? da 5) Pda 2a8 |}, Pe pes a 
and by differentiation obtains from it 
d?e | 2pa? de ea pa? ) 
—.+5>-5 5-3 lems = 2v lsubeaor (13) 
leh Te sites th nice 
Two lines further on he states that this is “independent of 
the law of density and ellipticity of the solid parts of the earth.” 
* At the time of writing art. 104 of my ‘Essay,’ this second mode of 
arriving at the equation 
Ep—t{Pye} =0 
presented itself to my mind. But I did not like to deviate too widely from 
the route I had taken in 1845. 
