1875.] 395 [Dodge. 



the extreme westerly point of Brookline. Very likely the extensive 

 masses of diorite in this vicinity should be classed among the " crys- 

 lines"; and if so, this range extends across Newton, and about a mile 

 into Brookline, where there are great masses of cliorite and amygda- 

 loid well exposed to examination on Hammond Street between New- 

 ton and Boylston Streets. Then the line is deflected to the westward 

 as far as Charles River again, to exclude conglomerates lying in 

 Newton and West Roxbury, and asserting itself again in the south- 

 eastern part of Needham, runs across Dedham Island to the corner 

 of Beach Street and Shawmut Avenue in West Roxbury. At this 

 place, the continuous area is mostly included by drawing the line 

 south-south-east toward Hyde Park village ; but to the east of this lies 

 the breccia above mentioned, and there are slates and puddingstones 

 about Hyde Park which again turn the outline we are tracing to the 

 south-west. Passing around these, we find crystallines again on the 

 south side of Mill Creek, and the line is thence more easily deter- 

 mined in an east-north-easterly direction across Milton, running about 

 quarter of a mile south of the Town House; and Quincy, intersect- 

 ing Adams Street at the corner of Common Street, as far as the Old 

 Colony R. R. Here it turns south-south-east once more, and then 

 indents to the westward about Town River, before continuing the 

 east-north-east course to Quincy Point. Weymouth Fore River 

 makes a convenient easterly and southerly limit here, the south-east 

 corner of the area approaching very closely to the second crystalline 

 band above described, at East Braintree. This easterly limit is far 

 from geometrically accurate, however. The trilobite slates, so well 

 known at Hayward's quarry, indent it on Quincy Neck and in Brain- 

 tree; and the slates continuing these in North Weymouth, Hingham 

 and Cohasset, are separated and disturbed by crystalline outcrops or 

 outflows which continue this range as far as the coast. These again 

 present the recurring difficulty of determining whether to consider 

 them as isolated outcrops of elevated metamorphic crystallines, or as 

 intrusive outflows. From East Braintree, the southern line of this 

 third band diverges about 6° from the northern limit of the second 

 as given above; runs through Braintree along, or in some places 

 south of West Street; across Randolph, Canton, and the eastern 

 part of Norwood, crossing the New York and New England Railroad 

 a little south of Winslow's Station, and turning here more to the 

 south-west, Walpole, and the south-eastern corner of Medfield. 



