44 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. 



come adjusted to its surroundings. That which does not change 

 becomes extinct, and the world is inherited by the changed and 

 best adapted. No sooner, however, has adjustment come in a time 

 of geologic quiet than an epoch of earth unrest starts again the 

 turning wheel of change. New migrations begin, and new con- 

 flicts arise between the forces of earth and her living forms : only 

 the best of each kind is spared to carry forward the web of life. 

 Thus it is that the changing environments resulting from the shift- 

 ing vicissitudes of the battle between the forces of earth and sun, 

 as marked by the advancing and retreating strand-lines, and the 

 fall and rise of mountains, have made for progress, and have 

 stimulated the evolution of all that higher life which dwells upon 

 the lands, and of that highest life which has begun to look with 

 understanding into the depths of space and time. 



In the shifting scenes which have been followed are shown, 

 graphically expressed for one locality, this warfare whose com- 

 prehension is a key to the history of the earth. 



