PHYSICAL HISTORY OF NEW HAMPSHIRE. 539 



Littleton, etc. Most of these patches contain crinoidal and coralline 

 limestones. It is hence inferred that the Connecticut valley was deeply 

 covered by the ocean, as polyps and crinoids do not flourish in limited 

 expanses of salt water. In New Hampshire crinoids, gasteropods, 

 brachiopods, corals, and fucoids are known to have flourished. The 

 ocean probably supported in addition echinoderms, trilobites, large crus- 

 tacea, and ganoid fish. The land may have been covered with the higher 

 cryptogams and coniferae. Numerous hills, covered with vegetation, 

 gave an unusual variety to the landscape. 



It is difficult to note precisely the limits of the Helderberg ocean. 

 There is reason to believe that northern New England and Canada sank 

 deeper than at any previous period, or at any time since. Outcrops of 

 the Helderberg rock abound in Quebec and northern Maine. The 

 locality at Lake Memphremagog may have been connected with the 

 New Hampshire ocean north of Essex county, as the highest of these 

 rocks in our state are elevated nearly one thousand feet above the level 

 of the sea. I have drawn the south-eastern shore line to correspond 

 with the second of our contour lines. The map also indicates that no 

 evidence exists of a submergence in this period in the south-eastern part 

 of the state. 



The age may be divided into three periods, first, the epoch of the 

 deposition of sandstone; second, of coralline limestone; third, of great 

 thicknesses of slate, schist, and conglomerate. The latter rock is com- 

 posed chiefly of pebbles derived from the Huronian and Atlantic rocks, 

 with a few of the Coos limestones. 



THE GLACIAL PERIOD. 



During the whole of the Devonian, Carboniferous, Permian, Mesozoic, 

 and Tertiary periods, New Hampshire stood above the level of the sea, 

 and may have included a considerable area beyond the Isles of Shoals. 

 No record has been left of any event that transpired within our limits 

 during this immense lapse of time. The land was probably covered 

 with vegetation, and animals roamed over the hillsides, judging from the 

 conditions known to have existed in the adjacent territory. In Vermont, 

 during the early Tertiary, there were certainly forests of hickory, beech, 



