416 _ Scientific Intelligence. 
increase in thickness of this shell would take place by the solidification 
of each of the surface strata of the nucleus in succession. If the matter 
composing the interior of the earth is subjected to the same physical laws 
as the material of the solid crust coming under our notice, the change of 
state in the fluid must be accompanied by a diminution of its volume. 
The contrary hypothesis has been hitherto always assumed in mathemati- 
esis has led show that it fundamentally affects the whole vila 
the 
the shell by congelation from the nucleus. 
