422 Proceedings of Royal Society of Edinburgh. [sess. 
is no doubt also truly solid, and the amount of this is being added 
to in consequence of the loss of heat from the surface. It seems 
probable also that any melted rock or other liquid matter which 
exists contracts on solidifying. If the earth were solid or liquid 
throughout the contraction due to the lowering of temperature 
which would be produced by the amount of heat emitted, accord- 
ing to any possible estimate of the specific heat and coefficient of 
expansion of the material, would be only a small fraction of that 
calculated above for a year. But if there is a slow solidification of 
liquid matter still going on with the much greater contraction of 
the material which generally accompanies change of state, a con- 
traction of the requisite amount might very easily be produced. It 
is to be noticed that such gradual solidification and consequent 
contraction supposes cooling to take place on the whole ; but the 
investigation shows that a very slight contraction would be effective 
in restraining very greatly the fall of temperature in the interior 
■of the earth.” 
{Issued separately June 5, 1903 . ) 
