280 STRATIGRAPHICAL GEOLOGY. 



ated with veins carrying galena. Though high, the dip increases its 

 angle till the western border is reached. The auriferous conglomerate 

 and beds of dolomite are met with near the western border of the group, 

 the former being about seventy-five feet thick. Near Parker hill the Lis- 

 bon group reappears, dipping south-easterly. This undoubtedly unites 

 beneath the Lyman and Cambrian rocks, completing the synclinal. No 

 effort has been made to measure its thickness beyond Parker hill. 



Detailed Maps. Of these there are two. One has been referred to in 

 Volume I, pages 22 and 46. This shows the result of a protracted survey 

 of four square miles in the south corner of Lyman, the principal object 

 being the accurate delineation of the formations with reference to aurif- 

 erous veins. The other embraces the country between the Connecticut 

 and Ammonoosuc rivers, and illustrates the topography of the region by 

 means of contours, with the locations of the several mining properties 

 Constant reference should be made to these maps for the purpose of 

 verifying our statements. 



Lisbon Group. At the south end of the field in Haverhill there seems 

 to be only one range of the green schists, in proceeding north-easterly. 

 This constitutes the floor spread out underneath the whole Ammonoosuc 

 area, the subdivisions about to be indicated being produced by lines of 

 superior groups. In this subdivision we first separate the ranges on the 

 extreme borders, the western being the most extensive, and following 

 Connecticut river to Dalton. The eastern is continuous to the south 

 part of Lisbon, and then seems to pass under the Swift Water series, 

 perhaps unconformably, to reappear in a modified form on the south 

 branch of the Ammonoosuc, terminating at Streeter pond. For the last 

 part of its course, it adjoins the Bethlehem gneiss. Towards the interior 

 parts of the basin we find limited areas of the green schists. First, there 

 is one in the north-east part of Bath, running into Lyman. This may 

 be ranked as Lyman schist upon the map, as both the green and white 

 schists are represented within it. It is separated from the slates at its 

 blunt south end by means of a fault; and very fine specimens of con- 

 torted strata came from this dislocated line. Second, a small area has 

 been discovered in the blank space of Fig. 27, Bald hill, Lyman. Third, 

 there are two narrow bands in Littleton, crossing Parker brook, in the 

 midst of Heldcrberg exposures. F'ourth, I think there is a line of out- 



