CHAP. XIV.] SUMMARY OF GEOGRAPHICAL EVOLUTION. 323 



probable, however, that the period in which we are now 

 living is one of those quiescent times which, as we have 

 seen, generally succeed periods of rapid movement and 

 disturbance. The earth's crust appears to be in a com- 

 paratively fixed and stable condition, and the movements 

 which are known to be in progress are so slight, or rather 

 the rate of change is so slow in relation to the short span 

 of human life, that we may safely rely on the permanency 

 of the present geographical conditions for a very long 

 period of future time. 



Professor Prestwich arrives at a similar conclusion from 

 somewhat different premises. He thinks that the great 

 cosmical cold of the Glacial epoch accelerated the con- 

 traction of the earth's crust, and that the disturbances 

 consequent upon this contraction were greater during the 

 prevalence of this cold than in the immediately preceding 

 and succeeding ages ; that, therefore, " during a certain 

 number of years succeeding to and to be measured by the 

 length of the Glacial period (whether that be 10,000 or 

 20,000, or any other number of years), the disturbances of 

 the crust would be at a minimum, and its stability at a 

 maximum. This is the condition under which I conceive 

 the crust of the earth is now placed, and which, as I have 

 before suggested, ensures that state of repose and immo- 

 bility which renders it fit and suitable for the habitation 

 of civilized man." l 



1 " Geology," by J. Prestwich, vol. ii. p. 549. 



