367 
February 22, 1875. 
The PRESIDENT (PROFESSOR BABINGTON) in the Chair. 
On the Formation of Mountains on the hypothesis of a 
liquid substratum. By Rev. O. Fisuur, F.G.5. 
This paper was a sequel to one read in December, 1873, in 
which it had been shewn that, upon the supposition that the 
inequalities of the earth's surface have been formed by con- 
traction of its volume through cooling, they are too great to be 
so accounted for if the earth has cooled as a solid body. In the 
present communication it was therefore assumed that there is a 
liquid layer beneath the cooled crust. After discussing several 
of the hypotheses of geologists regarding the formation of con- 
tinental areas and ocean-basins, and of mountain-ranges, an 
enquiry was made regarding the form which a flexible crust 
would take, if it rested in corrugations on a liquid substratum. 
The answer arrived at was, that a section carried across the 
corrugations would approximately present at the lower surface 
a series of equal portions of circular arcs, concave upwards, and 
arranged end to end in a festoon-like manner. 
Their common radius would be 26 c, where p, o are the 
densities of the crust and liquid respectively, and ¢ the thick- 
ness of the crust. The horizontal pressure would be zero at the 
highest points. 
In applying this result to the crust of the earth, it was 
admitted that it can give only a very approximate solution of 
the problem. Owing to the defect from flexibility, and from 
absolute fluidity in the substratum on which it rests, the con- 
ditions assumed would not be strictly fulfilled, and they would 
also vary from place to place, so that no uniform result could 
be expected. Nevertheless it seems tolerably certain that 
