REVIEWS 433 



brought to a condition of old age, it has been rejuvenated and more 

 maturely dissected than the Piedmont upland of Virginia, the type of 

 renewed dissection in a second cycle. The ice-sheet therefore advanced 

 over a region of distinct hills and valleys, not over a peneplain. The 

 implication that the ice-sheet was an effective agent of destruction is 

 confirmed on reading that the traces of glacial action "here consist 

 mainly of features of erosion. But little matter was deposited by it, 

 that little consisting of what is known as 'erratics,' or granite bowlders, 



which are scattered freely over the country A great deal of 



erosion, however, was done by the ice-sheet. It searched out very- 

 keenly the soft spots in the granite surface of the country and scoured 

 them away, leaving depressions and, between such depressions, rounded 



hills of granite All of the soil or disintegrated rock was scraped 



away, leaving the granite bare ; hence it is that the soil covering of 

 southern Maine is very thin, for it has been derived mainly from the 

 disintegration of rocks since the passing of the glacier." Apart from 

 the implication that the hills today result from the glacial excavation of 

 depressions between them, and from the implication that granite is the 

 only kind of rock in this region whose linear ridges and fiords give 

 so strong an indication of foliated or stratified structures, it is unfor- 

 tunate that the common veneer of till, the relatively plentiful deposits of 

 washed gravel and sand, and the important cover of marine clays in the 

 valley floors of southern Maine should pass unnoticed. The farmers 

 of that region very rarely depend on soil of postglacial weathering. 

 The rocky ridges with a thin soil, partly of glacial drift, partly of post- 

 glacial weathering, are left in uncultivated forests and woodlots. 



It is further to be regretted that, after showing by the first four 

 types that time is an important element in geographical description, 

 no sufficient mention is made of the element of time in connection 

 with the two examples of shore-line features. It is of course recog- 

 nized that the irregular coast line of Maine is a result of the partial 

 submergence of a rugged land ; but no consideration is given to the 

 evidence that the submergence is recent ; so recent that wave action 

 has not yet cut back the headlands, and that river action has not yet 

 filled up the bay heads. Hence the account of shore lines is not 

 homologous with that of land surfaces, in which the stage of advance 

 reached by destructive processes is carefully considered. The oppor- 

 tunity for teaching an important principle in the evolution of shore 

 lines is thus lost. W. M. Davis. 



