402 W. H. Hobbs — Instance of the Action of the 



basalt within the valley. . The position and direction of this 

 train is brought out in fig. 2, which is a sketch map of the 

 Pomperaug Yalley. Upon the south-southeastern flank of 

 Sherman Hill the train begins as a collection of irregular 

 blocks of basalt, occupying a belt about one hundred feet in 

 width and extending from the present low tower-like crest of 

 the hill to the corner of the highway, where is the edge of the 

 terrace floor of the valley and where the train appears to end 

 abruptly. Within this portion of the train are a dozen or 

 more blocks six to eight feet in diameter, and very many 

 smaller ones. Fig. 1, PI. IX is a view looking up the train 

 from a point near the road corner toward the summit of Sher- 

 man Hill. 



Lost in the terrace deposits of the valley the train is again 

 picked up upon the south side of the valley so soon as the 

 slope begins to rise above the level of the terrace. This local- 

 ity is near and west of the road from South Britain over 

 Georges Hill (see fig. 2) and just above the great fill upon the 

 railroad. The sand and gravel for this fill was obtained from 

 the area immediately north where indicated upon the map 

 (A of fig. 2). Mr.' Henry M. Campbell of South Britain 

 pointed out to the writer a place where three large blocks, of 

 the basalt, one of them six feet or more in diameter, were 

 unearthed and removed by blasting during the excavation of 

 this section of terrace. The location would fall within the 

 line of the train from Sherman Hill. 



The blocks now in evidence south of the railroad fill are of 

 special interest because of their location in the line of the train 

 and because of their unusual size. Fig. 2, PL IX, which looks 

 northwestward along the train, includes two of the largest. 

 The hill from which they were separated is visible in the dis- 

 tance (more than a mile and a half away) between their tops. 

 There are several blocks of this size (15 to 25 ft. in largest 

 dimensions), some partially buried in earth along with many 

 smaller blocks, but all located within a belt less than a hun- 

 dred feet in width. The train does not appear to extend south- 

 ward beyond this point, but no attempt has been made to 

 follow it farther. The direction from Sherman Hill of these 

 great blocks of basalt, which form a landmark in the valley, is 

 S. 28° to 29° E., a value near that of the average movement of 

 the ice over the higher points in the vicinity. 



The conditions seem here to be best explained by assuming 

 that from the pre-glacial surface produced by subaerial erosion 

 the faulted prisms of basalt projected in pinnacles above the 

 softer sandstones, in part opposing to the ice stout walls and in 

 part comparatively slender walls and towers. Sherman Hill, 

 as indicated by the geological map in the report here cited, 



