630 HISTORICAL GEOLOGY. 



as they advanced, may have made their ebb or their flow over this more 

 ■western part of the bay-like channel; and, by their rapid movement, have 

 produced the assorting of the gravel and the accumulations of large stones 

 or pebbles ; and they may also, by some variation in their route, as time 

 passed, have made pebble deposits locally at different levels. Such rapid 

 tidal flows, causing the stones in shallow waters to slip over one another 

 with each return of the current, would tend to make them flat, as in the 

 Panama conglomerate, and not round as in ordinary round-pebble con- 

 glomerates, the latter being work of plunging waves along a beach and of 

 strong currents. 



BIOLOGICAL PROGRESS. 



The progress of the systems of life through the Devonian era was con- 

 tinued into and through the following era without any abrupt transition, 

 and the review of the subject is given for both eras after the account of the 

 Carbonic era. 



UPTURNING OR MOUNTAIN-MAKING AT THE CLOSE OF THE 



DEVONIAN. 



Through nearly all of N'orth America, where Devonian and Carboniferous 

 rocks occur together, the two formations pass into one another continuously, 

 as if one in series. But in eastern Canada at Gaspe, in Maine, and in Nova 

 Scotia, and at Perry in southern New Brunswick, as reported by Dawson and 

 Logan, there was an upturning of the Devonian and inferior beds, so that 

 the overlying Carboniferous rests upon them unconformably. Dawson 

 makes the unconformability general for the Acadian Provinces. 



The upturning and crystallization of the Devonian and Upper Silurian 

 beds of the Connecticut valley, as well as of those of Lake Memphreraagog 

 and the St. Lawrence valley, may have been a part of the events of this 

 epoch. But it is equally possible and probable that the upturning took 

 place at the close of Paleozoic time. 



In Great Britain, Russia, and Bohemia, some evidences of upturning 

 between the Devonian and Carboniferous have been' observed, and not in 

 central and southern France. But all these cases are small exceptions to 

 the general fact that the Lower Carboniferous and the underlying rocks 

 are conformable almost the whole world over. The epoch of transition Avas 

 not an epoch of general disturbance. There were extensive oscillations of 

 level ; but for the most part they involved no violent upturnings. The 

 following era opens with a period of marine formations ; and the beds accu- 

 mulated, in most regions where they occur, are a direct continuation of the 

 deposits of the Devonian. 



