222 SURFACE GEOLOGY. 



interesting case of intersection, S. 3° x 21° x 36° E. On tlie east rim of 

 the basin are higlier figures. Belmont, 32°-42°; Gilmanton, 32°-52°; 

 Loudon, 40°; Pittsfield, 42°; Deerficld, 40°; Northwood, 32^-37°; east 

 part of Hooksett, 41^; ridge east of Manchester (quarries), 40°; Candia, 

 2i°-4i°; Londonderry, 41°. It would seem as if these observations 

 might be interi^reted as indicating a difference between the direction of 

 the forces down the valley and over the eastern rim. There are a few 

 strongly marked south-east courses on the west rim, as through Wash- 

 ington and Springfield, that are between 20° and 30°. Hence there is 

 not that definiteness of demarcation between the rims and the valley 

 courses that we found in the Connecticut. The three courses in Hud- 

 son may perhaps be regarded as typical of as many different movements. 

 The unusual direction of S. 72° E. in Deerfield, on the north side of Mt. 

 Pawtuckaway, may have been due to the presence of the mountain mass. 



There is one example of striae sliding N. 40° W. on the east side of the 

 valley. It is at the Amoskeag granite quarry in Manchester. Its exist- 

 ence would not be known save for the removal of the earth for quarrying. 

 Who knows how many more such cases may exist under these loose 

 materials, sufficient to make sure the presence of the glacier in the 

 Merrimack valley ! 



In the Contoocook valley we find no evidence from stride to suggest 

 the northward motion of the ice. Unusual accumulations of till at Hills- 

 borough Bridge and in the west edge of Henniker are suggestive of ter- 

 minal moraines pushed forward by such a movement. The striae in An- 

 trim follow the course of the valley, but may have gone southerly. The 

 North Branch valley, in the same town, is deep and narrow, and hence 

 well fitted for the passage of a glacier. We find marks indicating that 

 it was crossed by the main ice-sheet without regard to the depression. 



Our final conclusion, from all the facts, must be, that the Merrimack 

 movement was largely a topographical modification of the course of the 

 main ice-sheet. As occasional remnants of the genuine south-east cur- 

 rent occur, it may be proper to say that the modification would naturally 

 take place in the interval of time between the predominance of the south- 

 east current and the local glaciers. And in the latter period the Mer- 

 rimack ice became still more restricted, and feebly imitated the local 

 action elsewhere. 



