East Haven-Branford Region. 375 



Sandstone containing trap. — This rock may be separated 

 into two classes : (a) the contact breccia, which is the result of 

 the rubbing of the trap against the sandstone on its upward or 

 onward passage, (b) trap conglomerate, which is, probably, the 

 effect of the action of aqueous forces. The contact breccia 

 occurs on the east side of the range E. 2, (B), on the southern 

 slope of the northern hook of the main ridge (H), and on the 

 northern slope of the southern hook of Toket Mt. The trap- 

 and sandstone rock lying upon parts of the range E. 2, may 

 possibly belong to this class. The trap conglomerate lies on 

 both sides of the northeastern extension of E. 2, and east of 

 its end, and, as has already been stated, the northern limit of 

 the area is about a third of a mile from Pond Rock where 

 nearest to it. 



The region containing the most interesting part of the con- 

 glomerate, i. e. the ridges, is about three- fourths of a mile long 

 from S.W. to ISLE, and perhaps half a mile wide. There are 

 several of these ridges each of which is from 300 to 400 yards 

 long ; and their general trend is N. 25° E. They are narrow, 

 begin and end abruptly, have almost precipitous sides, and rise 

 about 125 feet (aneroid measurement) above the brook and 

 meadow bounding their region on the east and south. The 

 valleys between them are narrow and from 40 to 60 feet deep. 

 The outlines of the bowlder ridges are indicated on the map 

 by dotted lines. 



The rock of the ridges is exceedingly coarse. Well rounded 

 bowlders a foot in diameter are very numerous, while others 

 two, three and even four feet long are by no means rare. 

 Much trap is present in the rock. In some of the western 

 ridges the conglomerate is mainly composed of trap fragments 

 with a small amount of coarse sandstone cement ; the middle 

 ridges contain many bowlders of quartzite, mica- and horn- 

 blende-schist, gneiss and granite ; while the eastern ridges seem 

 to have rather more of the latter constituents than of trap. 

 Bowlders of coarse sandstone also occur in this rock, and many 

 of the fragments of trap have coarse sandstone adhering firmly 

 to them and forming a part of the bowlders imbedded in the 

 conglomerate. The pieces of trap are either angular, subangu- 

 lar, or well rounded, compact or amygdaloidal, and quite fresh 

 or much decomposed. Many of them contain long, vermiform 

 cavities, either empty or filled with calcite, like the trap of the 

 southern end of the ridge next west of Pond Rock. But few 

 trap bowlders and those widely scattered occur in the western 

 and southern part of the conglomerate area. 



Main theories as to the origin of the trap. — Prof. Davis, 

 in connection with his bibliography of the subject,* has given 



* Bull. Mus. Comp. Zool., vii, 1883. 



