56 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



south. Still farther west, on the north side of Nahanton Street (Plate 

 2, Loc. 3), conglomerate occurs in a re-entrant angle between outcrops 

 of melaphyr. No actual contact is seen, but a large boulder, found 

 near to this conglomerate outcrop, shows both conglomerate and 

 melaphyr, the contact being apparently igneous. 



No other contacts are known on the southern border of the melaphyr 

 area. On the northern border contacts have been seen in but one locality. 

 East of Hammond Street (Plate 2, Loc. 4), opposite the cemetery, the 

 melaphyr has been exposed in two trenches. In both cases it is in con- 

 tact with conglomerate on its southern side. The contact is practically 

 vertical, while the conglomerate dips north at a moderate angle. A red 

 zone is developed in the conglomerate along the contact, and the sedi- 

 ment is penetrated by little tongues of the melaphyr. The north side 

 of the melaphyr is not shown. It seems reasonable to regard this small 

 body as an offshoot from the main mass to the south. The deeper of 

 the two trenches is now filled, while the sides of the other have fallen 

 in, obscuring the evidence. The main mass of melaphyr in this area is 

 separated from the conglomerate by a belt of low land. A ditch has 

 been dug along this belt from Hammond Street to Heath Street. At 

 present there is no exposure of rock in this ditch, but the debris taken 

 from it has been piled along its banks. A number of fragments have 

 been found in this debris which show the melaphyr in contact with the 

 conglomerate. Several of these bear witness to the igneous nature of 

 the contact, and one, in particular, shows the sediment penetrated by a 

 tongue of the melaphyr. In the same specimen a stringer from the 

 sediment has been partially fused and included within the igneous rock. 

 Under the microscope the feldspars are seen oriented in striking con- 

 formity with the boundaries of this included fragment. 



The melaphyr is seen in contact with the conglomerate in several 

 places on the bank of the Charles River north of Boylston Street, New- 

 ton Upper Falls (Plate 2, Loc. 5). It clearly penetrates the sediment 

 along the contacts. In two places it cuts, dike-like, across the bedding 

 of the conglomerate. Farther east, on Rockland Street (Plate 2, Loc. 6), 

 the two rocks appear together, the contact zone developed by the melaphyr 

 being quite evident. On the corner of Rockland Avenue and Boylston 

 Street the melaphyr, although not seen in direct contact with the sedi- 

 ments, is filled with fragments of sandstone, presumably derived from 

 the neighboring sedimentary rocks (Plate 2, Loc. 7). 



On the north side of Commonwealth Avenue, a little east of Auburn- 

 dale (Plate 2, Loc. 12), a ledge of coarse sandstone is cut by several 



