194 



On the north side of Hay ward's Creek the massive grayish 

 slate of the Paradoxides qimrry is well exposed, and may be 

 traced by almost continuous outcrops for nearly one-fourth of a 

 mile in a north-west direction, maintaining an approximately 

 E.— W. strike and nearly vertical dip.^ As before, it is cut off 

 abruptly and irregularly by the 'granite on the west, and the 

 slate near the contact is more or less altered. Layers of the 

 purplish-brown slate are now and then included ; and I ob- 

 served, in not a few ledges, a coarse amygdaloidal structure like 

 that at Mill Cove. The almost perfect agreement here demon- 

 strated in strike and dip, relations to tjie granite, and litho- 

 logical and mineralogical characters, of the slate on the north and 

 south sides of Hay ward's Creek and at Mill Cove, places their 

 essential identity beyond reasonable doubt. 



As Mr. Dodge has remarked,^ the slate along the Mona- 

 toquot River, in Braintree, is very like that of the Paradoxides 

 locality, and is similarly related to the granite ; and these tAvo 

 areas are doubtless continuous, under the bed of Weymouth 

 Fore River, with each other and the slate at Mill Cove. On 

 the west side of the river, at the first bend north of Weymouth 

 Landing, the slate is greenish-gray and purplish-brown. Be- 

 tween Quincy Point and the Old Colony Railroad there are 

 no outcrops ; but west of the railroad the slate is exposed im- 

 mediately north of the granite, and agrees in all important 

 respects with that at Hayward's Creek and Monatoquot River. 

 It can be shown that the slate in the vicinity of Mill Cove is 

 probably continuous across Weymouth Back River with the slate 

 in the north part of Hingham. 



This' species of investigation has been extended over the en- 

 tire basin, with substantially the same results ; the facts every- 

 where favoring the view that the slates are all of the same age ; 

 though of course the proof becomes, on the whole, less conclu- 

 sive the farther we recede from the fossiliferous beds. Occa- 



1 The first re-entrant angle in the boundary of the slates on this side of the creek is 

 not so deep as represented; in fact, it scarcely exists. 

 =" Proo. Bost. Soc. Nat. Hist., xvii., 403. 



