GEOLOGY OF THE CONNECTICUT VALLEY DISTRICT. 339 



ure an area of slates and limestones, the latter very scanty in amount, 

 upon the top of the hill east of the Reduction Works Company's mine, 

 near the house of D. Knapp. The limestone contains many small cri- 

 noidal fragments. The slate is friable, dipping 75° north-westerly, and 

 is eight hundred feet wide. This area has been preserved from denuda- 

 tion by the presence on the exposed side of a thick mass of conglomerate, 

 described upon page 305. On passing northerly the slates expand so as 

 to adjoin the conglomerate above the fault, and seem to extend nearly to 

 Young's pond. In this area are several veins of white cavernous quartz, 

 full of iron rust, which have been opened to a slight extent for gold, 

 though evidence that gold is present is meagre. It occurred to me, 

 when examining them, that these Helderberg veins might be distin- 

 guished from the Cambrian auriferous quartz by a very fetid odor and 

 the absence of ankerite. The very cavernous feature would hardly be 

 distinctive, since it may have arisen from a more perfect atmospheric 

 disintegration. North of Young's pond are some irregular slates, which 

 may perhaps represent the Helderberg. 



Still another possible locality of this formation exists about half a mile 

 from Mill brook in Lisbon, on the road running south-west from a saw- 

 mill. Loose blocks of crinoidal limestones were seen adjacent to an out- 

 crop of the auriferous conglomerate, which seem to have been derived 

 from a ledge. Without doubt other similar patches will be found in dif- 

 ferent parts of the Ammonoosuc gold field after further search. 



In my article upon the Helderberg of New Hampshire, published in 

 the American Jotirnal of Science, I remarked upon the probability that 

 the Dalton Mountain slates are of Helderberg age. Much of the rock 

 there is a fine argillaceous sandstone. Since the later reference of the 

 argillaceous rocks of Blueberry hill to the Cambrian area, this opinion is 

 greatly weakened. The possibility of the Helderberg slates back of the 

 Crawford house is set aside by further investigation. 



Fossils. We have found quite a number of fossils. The circumstances 

 of their original discovery have been noted in Volume I, page 48. Two 

 parcels of these organisms were forwarded to the late distinguished pale- 

 ontologist of Canada, E. Billings, who had special familiarity with the 

 fossils of about this period in the extension of the series northward. At 

 first he found Favosites basaltica and a ZaphrentiSy with small crinoidal 



