GEOLOGT : NORTH SHORE. 15 



Literature. 



Jagger, T. A., Jr. — An occurrence of acid pegmatite in diabase. 

 (Am. Geol., vol. 21, pp. 203-213.) 



Merrill, G. P. — Rocks, rock-weathering and soils. 181)7, pp. 218-222. 



GLOUCESTER MORAINE. 



Route. — By boat, from Central wharf , Boston, to Gloucester; single 

 fare, 8.50 ; round trip, 8.75. 



By rail, Eastern division Boston and Maine road, to Gloucester ; fare 

 8-72. 



From Gloucester, take electrics for Bockport, alighting when most 

 convenient; or better, walk eastward along electric track, turning south 

 at any desired point. The excessively rocky portion lies chiefly on that 

 side. Again, take electrics for Lanes ville, alighting at Riverdale, and 

 walking up to the morainio field. Visit Bail Cut hill. A good view can 

 be obtained from near the signal staff, and a heavy moraine lies west of 

 the hill. 



All the central part of the island of Cape Ann is occupied by 

 morainal material ; but the portions most interesting are the "dog- 

 town commons," formed of excessively bouldery drift, and so 

 stony as to be worthless for cultivation. These form some of the 

 roughly parallel ridges running northeast. They lie mainly in two 

 or three lines, on both sides of the railroad to Rockport. The 

 electric line is nearer the outermost or southern ones. Their posi- 

 tion can be found best from the map opposite page 608 in the 

 paper noted below. Among other interesting problems connected 

 with the region are differential postglacial weathering, postglacial 

 and preglacial stream erosion, and the composition of the moraine. 



Literature. 



Shaler, N. S— Geology of Cape Ann, Mass. (U. S. Geol. Surv., 9th 

 An. rep., pp. 529-611.) 



ARLINGTON MORAINE. 



Route. — By electrics (Harvard square car) to Harvard square ; change 

 to Arlington car, stopping at Highland avenue, Arlington. Follow this 

 street to the end, where a road leads north to water tower. Strike into the 

 fields on the southwest where, on the hillside, the moraine will be seen. 



This is an excessively rocky moraine, composed of medium-sized 

 granite boulders, all of which are well rounded by weathering. 

 The moraine trends generally northeast and southwest, and its 

 northern margin is very strongly defined. It can be traced south- 



