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has attracted attention since the fii'st settlement of the town, 

 was described by Prof. Edward Hitchcock, in his final report 

 upon the geology of Massachusetts, under the head of por- 

 phyry, as occurring in ridges a little north of tiie village. 

 Such ridges do not exist now ; and the statement of this 

 accurate observer should, p('rha[)s, be interpreted as referring 

 to ledges along the line of Lincoln Street which have probably 

 been effaced by tlie sul)sequent grading of tlu; street. At the 

 present time, the only actual exposui'c of tlu; I'ock iv sifii is 

 an obscure outcrop in the roadway at the junction of Crow 

 Point Lane and Downer Avenue. This was formerl}^ a some- 

 what protruding ledge, but it does not now rise above the 

 level of the street, and might easily be overlooked. It is in 

 an area colored as melaphyr on the map, and it is regarded 

 as a l)Oss of the felsite projecting, as the result of erosion, 

 through the sheet of melaphyr. The character for felsite also 

 appears on the map (PI. 9) behind Mr. Bradley's l)arn, west of 

 Thaxter Street and south of Lincoln Street. No actual ledge 

 of felsite has been observed here, but a number of excep- 

 tionally large, angular l)owlders in the drift, some of which 

 can be seen on the surface, while others were exposed in a 

 temporary excavation, suggest that the ledge is close by. 

 Immediately north and west of this point there are outcrops 

 of melaphyr. and no bowlders of felsite can be seen. Hence 

 the northern boundary of the felsite may be regarded as 

 accurately located at this point. But the boundary between 

 it and the granite on the south is a mere matter of conjecture, 

 although the line on the special map extending from P>rond 

 Cove, south of the solitary house on Lincoln Street, across 

 Bradley's Hill and Thaxter Street, is probably an approxima- 

 tion to it. The distribution of the bowlders certainly suggests 

 an east-west belt of the red felsite along the northern edge of 

 the granite, and passing under Bradley's Hill. That it 

 extends east under Broad Cove is at least probable ; and 

 that it extends west beneath Squirrel Hill we have some 



