BURR: MELAPHYR OF BROOKLINE, BRIGHTON, AND NEWTON. 5/ 



irregular, dike-like intrusions of the melaphyr. The two rocks look 

 much alike upon the weathered surface, so that it is difficult to differ- 

 entiate them in the outcrop. The main body of melaphyr does not 

 appear in contact with the sandstone, but is to be seen in an outcrop 

 fifty yards eastward. A half-mile farther east, on the corner of Prince 

 Street (Plate 2, Loc. 13), the melaphyr is in contact with similar sand- 

 stone. The contact is unmistakably igneous. The sandstone dips north 

 at an angle of 15°. The plane of contact also dips north, but at, a much 

 higher angle, approximating 50°. The effect of the igneous rocks upon 

 the sandstone is plainly visible. Structures are obliterated and a distinct 

 contact zone is developed, while the irregularity of the contact is such as 

 could hardly be produced except by igneous action. Under the micro- 

 scope the feldspars are seen to be aligned along the contact. 



The melaphyr is not again seen in contact with sediments for three 

 miles toward the east. On Cambridge Street, Brighton, a short distance 

 west of Foster Street, a cliff of sandstone and conglomerate is capped by 

 melaphyr. The contact shows abundant signs of igneous action. This 

 would, however, be true if the melaphyr were a flow. In the Allstou 

 area, bounded approximately by Cambridge and Warren Streets and Com- 

 monwealth and Harvard Avenues, contact exposures are fairly numerous 

 and frequently satisfactory. The relations of the rocks in this area 

 have been discussed by several writers, notably W. 0. Ci'osby, E. R. 

 Benton, and H. G. Woodward. Benton concludes that the melaphyr is 

 intrusive into the sediments. Crosby and Woodward do not accept this 

 conclusion, their idea being that the melaphyr masses are made up of 

 successive flows. W r oodward has mapped the area with great care, and 

 has differentiated six flows. His work has not been published, and 

 is, therefore, not subject to criticism. His map, however, was printed 

 and distributed by Professor Crosby in connection with a course of lec- 

 tures given at the Boston Society of Natural History in 1889-90. As 

 this map shows very clearly the location of the six supposed flows, it 

 seems fair to discuss thern, not foi'getting that Woodward may have been 

 in possession of evidence which has escaped the writer. 



The most southerly of these supposed flows is not well indicated in 

 the field. It is not seen in contact with the sedimentary rocks. The 

 second " flow " is indicated by three outcrops. One of these, lying north 

 of the elbow in Commonwealth Avenue, shows amygdaloidal melaphyr 

 overlain by patches of sandstone and slate. The contact is not striking, 

 as the melaphyr and the sandstone are of the same dull green color, and 

 not unlike in texture. It becomes clear, however, on examination,: that 



