40 JOURNAIy OF THE 



SO too the larg-e amount of sandy matter even in the 

 slates affords a presumption that the reg-ion was not 

 remote from the coast line. The rocks from which 

 the pebbles were taken were mainly identifiable in the 

 western portion of the field above described. " 



The g^eneral inference is then that during- a large 

 part of Cambrian time the shore line was in a g-eneral 

 way coincident with the present shore-line from Mass- 

 achusetts northward; that- a gradual subsidence of 

 parts of the coast region ensued by which the ocean 

 transgressed the land, accumulating, as it moved 

 inward, a sheet of coarse deposits which were in turn 

 covered by fine argillacious and calcareous sediments 

 forming slate and limestone. These seem to have 

 been formed in a sheltered sea, hence the opinion is 

 that the land barriers existed somewhere to the east. 

 During this inward march of. the shore-line there must 

 have been many partial returns to its former position 

 but the general result was an inward extension, amount- 

 ing in some places to fifty, and in other places to one 

 hundred miles, from its present position. 



When we attempt to reckon upon the southward 

 extension of the Cambrian shore-line we are entirely at 

 a loss, for, in the first place, we have no known Cam- 

 brian deposits south of New England which can be 

 clearly ascribed to the Atlantic field of deposition. 

 Apparently the Cambrian, as well as the whole of the 

 Paleozoic rocks are entirely missing from the southern 

 Atlantic province. This has led to the belief, which is 

 supported only by negative evidence, however, that 

 during the whole of the Paleozoic era the eastern 

 extension of the continent was much greater than it is 

 now. There is really little doubt that this was the 

 case, and the evidence of land barriers lying to the 



