240 



ledge on Beacon Street, immediately north of Baptist Pond. 

 It is of a pure gray color, and so massive that I could not 

 determine the dip. Beyond this there are no outcrops for 

 more than a mile ; but the slate-belt is well exposed between 

 Woodward Street and the Charles River. It here experiences 

 a southerly deflection, the strike of the beds shifting to north- 

 east. The strike of the conglomerate, south of and under the 

 slate, also changes, so that the two rocks remain entirely 

 conformable. The southern portion of this conglomerate, 

 where it adjoins the amygdaloid, is exceedingly coarse, and 

 lies almost horizontal. A good point to observe this is on the 

 new street leading south from Newton Highlands Station on 

 the New York and New England Eailroad (Woonsocket 

 Division). Proceeding northward the dip in that direction 

 gradually increases, and the pebbles become smaller. 



Between the railroad and Boylston Street the river has cut 

 a gorge through high masses of conglomerate ; and just south 

 of Boylston Street these include gritty layers, M^hich show a 

 north-west dip of 35° to 40°. One-fourth mile north-east 

 of this point, on the line of the Sudbury River aqueduct, the 

 same horizon of conglomerate crops again. The beds tran- 

 siently exposed here during the construction of the aqueduct 

 contain a large amount of pinite, resembling the con- 

 glomerate at the east end of the petrosilex in Milton. It is 

 traversed along the strike by a mass of amygdaloid, apparently 

 in the same way as in the glen east of Newton Centre. The 

 dip and strike are the same as on Boylston Street, and toward 

 the north-west the conglomerate passes into and is conformably 

 overlaid by a distinct, ripple-marked, brownish-gray sandstone, 

 which becomes finer away from the conglomerate. This pas- 

 sage can be traced in almost continuous outcrops, the ledges 

 having trends conspicuously parallel with the strike. North- 

 west of the sandstone, after two hundred feet concealed, is an 

 outcrop of brownish or purplish-gray arenaceous slate, also 

 ripple-marked, and dipping north-west 35°. Following this 

 line of strike back to the river, we have, at a distance of 



