﻿50 JV. S. Shaler — Geology of Cobscook Bay District, Me. 



the slates of the Cambridge district in Massachusetts, and gen- 

 erally of the Cambrian slates about Boston, which they resem- 

 ble in a general way, especially in the remarkable absence of 

 lime in their composition. This Campobello series probably 

 rests immediately on the subjacent older series of Laurentian 

 age, and may represent the lower Cambrian section, but the 

 phenomena of contact with the underlying beds are unknown. 

 Above these Cambrian layers, and without observed contacts 

 with them but with scant place for any intermediate deposits, 

 lie the beds of the Cobscook series. This series has a thickness in 

 all of not less than four thousand feet, and on careful study 

 may be found to have much more than this depth. Although* 

 the contact between this series and the Campobello group is 

 not known, the facts justify us in saying that an expensive ele- 

 vation and erosion of the last named deposits took place before 

 the deposition of the Cobscook series was begun or after they 

 were formed, for they were not present on the Deer Island an- 

 ticlinal or on the banks of the St. Croix river, where the Perry 

 series was laid down. The presumption is that they were 

 originally in place on these surfaces, but were worn away 

 during the interval between the close of the Cobscook series 

 and the formation of the Perry beds. 



Last in this succession of deposits we have the coarse red 

 sandstones, conglomerates and reddish shales of the Perry 

 series. This deposit is certainly over two thousand feet in 

 thickness. It differs very widely from those which occupy a 

 lower level in this district ; nearly all the other deposits seen 

 are mainly if not entirely made up of materials such as may 

 be laid down in a tolerably deep sea. The Perry section was 

 clearly formed in shallow water in immediate proximity to the 

 land. 



If the lower part of the section at Perry should turn out to 

 be upper Devonian or Sub-carboniferous, as seems not improba- 

 ble, then the evidence will be to the effect that a period of 

 erosion occurred in the interval between the close of the middle 

 Devonian section and the formation of the Perry beds. This is 

 especially interesting, as it would seem to show that this por- 

 tion of the continent was above the sea during a part of the 

 Devonian, or of the Sub-carboniferous period. Moreover, the 

 character of the sediments which formed the Perry series favors 

 this view. Those are clearly materials which were derived from 

 neighboring lands. If we could assume with Sir A. C. Ramsay 

 that all such red sandstones as are found in the Perry section 

 were formed in fresh or brackish water, then this series would 

 perhaps indicate a time when the shore line was at or near its 

 present position. This view is rendered quite probable by the 

 fact that the Perry beds have yielded a certain number of land 



