PALEOZOIC TIME LOWER SILURIAN. 633 



easterly, nearly parallel with the Appalachians. But at the north, in Ohio, 

 it extends northwesterly, and has also a northeastern branch in the direction 

 of Findlay, Ohio, toward Lake Erie. That this was the time of the uplift is 

 proved by the absence of Upper Silurian and Lower Devonian beds over the 

 region, these formations thinning out toward the axis, where the Cincinnati 

 limestone is the surface rock ; and, in Tennessee, as Safford states, by the 

 Devonian black slate resting directly on the Lower Silurian beds. The line 

 of the axis presents now no conspicuous topographical feature; but the 

 direction of the draining streams, which follow the strike of the strata on 

 either side, indicates that it once formed a watershed that gave the initial 

 bearing to their flow. The part of the arch about Cincinnati has been more 

 deeply and extensively removed than farther north, though higher now than 

 elsewhere, and, therefore, " this probably was originally the highest part of 

 the arch within the limits of the state of Ohio." 



According to R. Bell, of the Canada survey, the geanticline is continued 

 northward across the west end of Lake Ontario to Lambton, in Ontario, 

 Canada, and perhaps beneath Lake Huron, but its emergence to this distance 

 is not proved. This range of broad islands and shallows had great influence 

 on the rock-making of later Paleozoic time — a view first recognized by 

 James Hall in 1859 {Pal. ]Sr. Y., in.). 



Upturnings in Nova Scotia and New Brunswick. — Unconformability 

 between the Upper Silurian and Lower Silurian rocks has been observed 

 in Carleton County, K.B., just north of the boundary near Metapedia Lake, 

 and also on Lake Temiscouata, and elsewhere (L. W. Bailey); and in Nova 

 Scotia at Cape St. George, Arisaig, Lochaber, and from Kerrowgane down 

 the East Eiver of Pictou, and north of Sunderland Lake. 



But through this epoch there was comparative quiet north of Gaspe in 

 the northern part of the St. Lawrence Gulf ; for the great limestone forma- 

 tion of Anticosti, which was begun in the Lower Silurian era, continued its 

 unbroken progress through the whole prolonged era of revolution, and after- 

 wards far into the Upper Silurian era. 



EUROPEAN. 



In America the disturbances closing the Lower Silurian were confined to 

 regions of very thick depositions, and mountain-making was the final result 

 of the upturning. Over central New York and farther west in the Conti- 

 nental Interior, the beds of the Lower and Upper Silurian eras follow one 

 another without any marked unconformability. Cases of intervening erosion 

 may be found ; for every period loses by erosion a large part of its depo- 

 sitions in the supply of material for the beds of the following period ; but no 

 case occurs of horizontal deposition on upturned Lower Silurian strata. 



In Eui-ope the facts are similar. Over the Continental Interior of Europe, 

 which includes all European Eussia up to the Archaean mountains on either 

 side, and the surface south to the foot hills of the Alps, the Upper Silurian 

 beds lie conformably on the Lower Silurian. The cases of unconformability 



