273 



compiiratively tliin ;ui(l easily (livertctl, and more soutlierly 

 diirino: the lonij intervcnino- period of maxiinuin olaciation. 



Of the local origin of the larger fragments, at least, in the 

 till, we have an impressive illustration in the numerous 

 bowlders on Pi'ospect Hill. This large drumlin is something 

 like Booth Hill in Scituate in being well sprinkled with 

 bowlders over a large part of its surface ; but owing, perhaj)s, 

 to aqueous erosion which has swept away the finer material, 

 they are especially abundant on the southwest and south sides 

 of the hill, these slopes being the most remarkable bowlder- 

 fields observed in the South Shore district and recalling the 

 bowlder-clad areas of Cape Ann. But among these thousands 

 of bowlders, of all sizes from six inches to six feet or more in 

 diameter, Mr. Bouve and I have observed very few that are 

 not granite ; and certainly the sedimentary and volcanic rocks 

 of northern Hingham are very sparingly represented. Still, in 

 a walk along the shore between Crow Point and Huit's Cove, 

 where the detritus is nearly all slate or slate and conglomerate, 

 one meets quite frequent bowlders of granite and felsitc, wliich 

 must have crossed Boston Harbor. The most impressive 

 example of this sort which I have observed is aiForded by the 

 two large bowlders of granite lying on the north side of Otis 

 Hill, They are coarsely crystalline, subangular, and from 10 

 to 12 feet in maximum diameter. Underlying this end of Otis 

 Hill and extending thence to the north shore of Hingham we have 

 quite certainly only the sedimentary rocks and intersecting 

 dikes of diabase ; and the nearest visible source of these 

 bowlders is the granite ledges of Saugus, 16 miles distant. 



The most notable bowlder in Hingham, so far as mere size 

 is concerned, is the large mass of granite on the north side of 

 Rockland Street, near the base of Old Colony Hill. It lies on 

 top of the ground and quite close to the road, but is partly 

 concealed by the young trees growing about it. It is an 

 irregularly angular block of granite ID feet long, IG feet 

 wide, and 17 feet higli ; and was prt)bably derived from one 



OCCAS. rAl'EKS li. S. X. If. JV. 18. 



