BUFFALO SOCIETY OF NATURAL SCIENCES 113 



Temiscaming region and elsewhere. At the base of the series is the 

 Clinton followed chiefly by shales and limestones representing 

 the Rochester and Lockport, and finally by a dolomite. Since 

 the sea in which these deposits accumulated was a transgressing 

 one, it is apparent that in some sections the Niagaran deposits 

 would overlap the late Ordovicic deposits and come to rest directly 

 upon the crystallines of the Canadian shield. Furthermore, pro- 

 gressively higher members of the Niagaran would come to rest upon 

 the old land as the Niagaran sea continued to spread. By the end 

 of Lockport time, the greatest expansion was reached, and contraction 

 of the sea set in, the Guelph dolomites being deposited in this more 

 circumscribed sea. In some sections the change in deposition is in- 

 augurated by the argillaceous beds of the Eramosa formation, and 

 some of the late Niagaran beds are somewhat argillaceous. Beyond 

 the farthest line of expansion of the Niagaran sea, the crystallines con- 

 tinued to form the rocky surface of the land. The contraction of the 

 sea continued, until by the beginning of Salina time it had shrunk to 

 such an extent that only a small epi-continental sea remained. It 

 makes little difference whether we assume that this sea dried up en- 

 tirely during the period when the salt formed in central and western 

 New York and in Michigan, or whether we believe that the con- 

 tracted remnant of the Niagaran sea persisted, the greater part of the 

 North American continent is known to have become dry land during 

 Salina time. Many writers have pointed out the evidences of arid 

 conditions in the Salina, and I need not here repeat them. The en- 

 tire country was exposed to drying winds, rain fell but seldom, and 

 then it came as cloudbursts, filling river channels quickly and creat- 

 ing torrential streams of short duration. Whatever vegetation there 

 may have been upon that ancient land was destroyed by the heat, and 

 we may picture the country as a great desert where desiccation was 

 in progress and where the winds and the rivers of flood seasons were 

 the chief agents of transportation for the mechanically broken up 

 rocks. The Salina was by no means a period of short duration; the 

 thickness of the salt deposits alone shows that a long time was re- 

 quired for their formation. Throughout this whole period, disinte- 

 gration of the Niagaran and earlier limestones was in progress, until 

 there must have been piled up great limestone and dolomite dunes 

 with fine beds of impure clayey material wherever shales were exposed 

 to the clastation processes of the semi-arid climate. The crystallines 

 likewise suffered the same destruction, and they added their quota to 



