Rib) 
i 
592 On the Evidence that the Earth's Interior is Solid. (June, 
granite. If it be fluid or gaseous inside, and the crust a thousand 
miles thick, that crust must be stronger than granite, and if only 
two or three hundred miles in thickness much stronger than 
granite. This conclusion is obviously strongly confirmatory of 
Sir William Thomson’s view that the earth is solid throughout." 
This statement of Professor Darwin seems to me misleading, 
for if his paper is understood aright, he has proved nothing of 
the actual earth, but only of a hypothetical homogeneous elastic in- 
compressible or compressible globe, and for this assumed globe he 
has substituted the term earth, the same as the algebraist uses the 
terms x and y. 
Is there a single geologist who believes that it is possible for 
this earth to have any such structure as that assumed for it by 
Thomson, Darwin and others? The difficulties placed by the 
physicists in the way of a belief in the earth’s liquid interior, 
seem to be of their own making. These difficulties arise from - 
the assumptions and limitations that the physicists have m- 
pose upon the problem to bring it within the range of sat 
ical analysis. They have taken premises that no geologist would 
take, and having proved their point regarding these asst 
premises, then claimed that they have proved. it f p 
What physicist has taken as his basis the most probable rer 
tion of the earth if its interior is liquid ; a heterogeneous, pa 
elastic, liquid interior, irregularly inter-locked with and grać 
passing into a lighter heterogeneous crust? The problem ee 
lieved to be beyond the power of any transcendental ee 
now known, and it is not believed to be possible m e 
to prove, at present, anything regarding the actual state 
earth’s interior. 
Our conclusions as to that state appear to be dependent 0° o 
evidence that can be derived from geological and pet 
cal studies. Professor Hennessy appears to have taken, 
basis for his mathematical discussion, data that @ aay 008 
probable constitution of the earth than those assumed by 
else, and his results are entirely consonant with the 
a fluid interior. 
It is as necessary that physical an 
the state of the earth’s interior should conform to 
as it is that geological theories should conform to 
eee 
d mathematical discussi? 
physical 
1 Philos. Trans., 1882, cLxxul, 187-230. 
or this earth. 
re nearer the 
facts, 
geological and 
