173 



with the banded jaspery concretions in the brecciated petrosilex 

 of Hyde Park. (See ante, p. 84.) Rocks which it seems 

 necessary to regard as belonging with the amygdaloid are some- 

 times decidedly arenaceous, ranging from a distinct sandstone 

 to a slightly micaceous quartzite. These may be observed one- 

 half mile south-east of Auburndale Station in Newton, and at 

 the corner of Lake and Washington Streets, Brighton. At 

 the latter place, however, the sand rock may belong with the 

 conglomerate. 



In Brookline and the southern part of Newton, especially, 

 the amygdaloid has frequently in some degree the aspect of 

 felsite or petrosilex, though never attaining the hardness proper 

 to these. At the corner of Newton and Vine Streets it holds 

 free quartz in a finely divided state and minute crystals of feld- 

 spar. To the west of this, on Nahanton Street, the rock is a 

 dark purplish slate, very compact. On Newton and Hammond 

 Streets, in Brookline, it is of various shades, purplish, brown- 

 ish, and dark-green, and very generally semi-brecciated, re- 

 sembling the felsitic rock in the section described on p. 171. 

 The northern amygdaloid area in Newton is largely composed 

 of a compact epidotic rock characterized by greenish tints. At 

 one point at least this rock is interstratified with a mottled 

 greenish and brownish argillite ; while in certain directions it 

 passes gradually into a less epidotic variety, which is quite 

 massive and decidedly porphyritic. 



The amygdaloids of this district are rarely quite free from 

 epidote ; in Needham, however, the chloritic character prevails. 

 Exposures are wanting over most of the area marked as amyg- 

 daloid in this town, but the rock can be seen to good advantage 

 along the roads running east and west from Charles River Vil- 

 lage, and on the line of the Sudbury River aqueduct, about 

 one mile W.S.W. from Newton Upper Falls. In both places 

 the amygdaloid is traversed locally by small parallel and inter- 

 secting veins of a brown, jaspery material in such a way as to 

 give it quite the aspect of a breccia. In the aqueduct cutting, 

 also, I have observed small irregular patches of a white jasper 



