Scientific Lectures. 87 



remain. When we trace the same beds beyond the influences which 

 have folded, contorted and crystalhzed them, we find that we have a 

 part of the same series of rocks which we know elsewhere as bearing 

 evidences of having been deposited in the ocean in the form of sedi- 

 ments. Sand, clay and carbonate of lime cannot be deposited in 

 regular layers in any way except by the action of water ; and there 

 is no other means of having them filled with these organic remains, 

 than by their gradual deposition in the ocean. More than this, we 

 have evidence of shallow water in the ripple marks, showing that the 

 bed of the ocean was sometimes near the surface, and at other times 

 was left dry by the receding tide and recovered by its flow ; for 

 it is well estabhshed that the tide ebbed and flowed during that time 

 as it does at the present. 



The results of the careful study of the geological structure of moun- 

 tains and the chemical nature of the rocks composing them, as well 

 as the paleeontological evidence when it can be had, all go to sustain 

 the views I have advanced. 



The rocks of the mountains are therefore a part of those of the 

 plain, and should, not be looked upon as having a different origin. 

 We have, also, the most positive and unequivocal evidence of 

 the manner and conditions under which the materials of these rocks 

 have been deposited upon the bottom of the ancient ocean, and we 

 are able to trace the successive stages of progress and development, 

 until finally, during the Coal period, we see this ocean bed becoming 

 dry land. Now, there is no evidence of any special disturbance 

 during the Coal period, or at its close, which would have raised the 

 ocean bed above the surface of the water. Moreover, this was no 

 local or limited influence ; for you will see, by reference to the map, that 

 it pervaded the entire country from the extreme northeast, from the 

 Gulf of St. Lawrence, and along this valley by the great lakes, far to 

 the westward beyond the Mississippi river, and southward to Georgia 

 and Alabama. Such a result, co-extensive in its operation with this 

 portion of the continent, cannot be due to influences like those 

 producing earthquakes or volcanoes. Tlie change from sea bottom 

 to dry land has been a gradual one ; the causes were inaugurated at 

 the commencement of the deposition of the Palaeozoic strata upon 

 the flanks of the old Laurentian continent, and they have continued 

 in operation throughout the entire time occupied in the accumulation 

 of these rocks, increasing in force, until at the close the greater part 

 had become a continental area. The change was a slow one, depend- 



