174 BULLETIN: MUSEUM OF COMPARATIVE ZOÖLOGY. 
larger slate areas to the north and south. This relation, however, 
has been questioned and will be discussed in the following chapter. 
——:— Associated Melaphyr. Accompanying the conglomerate 
series are important masses of melaphyr that occur in isolated areas. 
The main exposures are indicated on the map. At Brighton the 
melaphyr is seen in contact with sandstone and slate. South of Bald 
Pate Hill in Newton, at Hingham, and at Nantasket it is seen in 
contact with conglomerate. Thus the occurrence of the melaphyr 
does not appear to be confined to one horizon. In addition to the 
actual exposures of the melaphyr there are a number of places where 
the conglomerate has been impregnated with the melaphyr in the 
manner described in the preceding chapter. This fact, together with 
the fact that at certain places, as at Nantasket and at Hingham, the 
«conglomerate is interbedded with the melaphyr, so that fragments of 
@ latter occur in the former, indicate that the melaphyr is contem- 
poraneous with the sediments and was intruded or outpoured before 
the latter were consolidated. 
Texture of the Conglomerate. In general it may be said that there 
is a gradation in the coarseness of the conglomerate toward both the 
north and the south from the slate belts. Just north of the Chestnut 
Hill slate belt the pebbles of the conglomerate average three or four 
inches in diameter while farther north along the main line of the Boston 
and Albany Railroad outcrops show a somewhat smaller average, two 
or three inches. The conglomerate along a north-south line from 
Newton Center to the railroad shows many alternations of sandstone 
and grit. South from the same slate belt the alternations of sandstone 
and conglomerate give way to very coarse conglomerate, with little 
indication of bedding. At ledges three-quarters of a mile west of 
Walnut Hill (Boston III, Y Z 12) the boulders of the conglomerate 
attain the size of two and one-half feet. At other localities in the 
region of Brookline and Newton similar coarse conglomerates are 
found. South toward Roslindale, the conglomerate again shows 
alternations of grit and sandstone which appear to pass conformably 
into the slates. Eastward the conglomerate has smaller pebbles and 
becomes more gritty. At the Tremont Street quarries (Boston v, 
S T 35), for example, the pebbles average one-half to two inches and 
at the quarries a mile and a half south (Boston VI, U 4) they average 
three inches in diameter. Similar features are noted, though not so 
well defined, in the southern conglomerate area. 
The distribution of the conglomerate and slate areas and the fre- 
quent alternations of coarser and finer material near the slates indicate 
