C. E. Dutton on the Contractional Hypothesis. 115 
movements, becoming more and more retarded, at length 
ceased, leaving a globe, departing from uniform temperature by 
differences not greater than the differences in congealing tem- 
peratures due to differences in pressure. e result would bea 
solid globe, with, perhaps, isolated reservoirs of liquid matter, 
which may have separated in the transition stage from fluid to 
solid by reason of a higher melting point. 
This assumption of the genesis of the earth, though regarded 
as preferable to all others that have been proposed, is by no 
means insisted on. It is selected because it gives to the con- 
tractional argument the fullest scope and widest range of 
conditions consistent with known physical laws. There is 
apparently no supposition which can reasonably allow a higher 
interior temperature consistently with the formation of a stable 
surface. To assume a lower temperature for the interior would 
take away from that argument pro rata a portion of the possible 
fore, from a globe possessing the highest degree of temperature 
nt. : 
r W. Thomson has very happily called Fourier’s solutions 
i ’ and the discussion 
Let V denote half the difference of the two initial temperatures. 
vu half their sum. ’ 
t the time. 
« the distance of any point from the plane. 
T the temperature of the point x at the time é : 
x the conductivity of the material in terms of its own 
thermal capacity. 
* Transactions Roy. Soc. Edinburgh, vol. xxiii. 
