276 GEOGNOSY OF THE APPALACHIANS. [XIII. 



regarded by the Messrs. Rogers as belonging to the Champlain 

 division, led them, in 1846, to look upon the White Mountains 

 as altered strata belonging to the Levant division of their 

 classification, corresponding to the Oneida, Medina, and Clinton 

 of the New York system. In 1848, Sir William Logan came 

 to a somewhat similar conclusion. Accepting, as we have seen, 

 the view of Emmons, that the strata about Quebec included a 

 portion of the Levant division, and regarding the Green Moun- 

 tain gneisses as the equivalents of these, he was induced to 

 place the White Mountain rocks still higher in the geological 

 series than the Messrs. Rogers had done, and expressed his 

 belief that they might be the altered representatives of the 

 New York system, from the base of the Lower Helderberg to the 

 top of the Chemung ; in other words, that they were not 

 Middle Silurian, but Upper Silurian and Devonian. This view, 

 adopted and enforced by me,* was further supported by Lesley 

 in 1860, and has been generally accepted up to this time. In 

 1870, however, I ventured to question it, and in a published 

 letter, addressed to Professor Dana, concluded, from a great 

 number of facts, that there exists a system of crystalline schists 

 distinct from, and newer than, the Laurentian and Huronian, 

 to which I gave the provisional name of Terranovan [since 

 called Montalban], constituting the third or White Mountain 

 series, which appears not only throughout the Appalachians, but 

 westward to the north of Lake Ontario, and around and beyond 

 Lake Superior, f Although I have, in. common with most other 

 American geologists, maintained that the crystalline rocks of 

 the Green Mountain and White Mountain series are altered 

 palaeozoic sediments, I find, on a careful examination of the 

 evidence, no satisfactory proof of such an age and origin, but 

 an array of facts which appear to me incompatible with the 

 hitherto received view, and lead me to conclude that the whole 

 of our crystalline schists of eastern North America are not only 

 pre-Silurian but pre-Cambrian in age. 



* Geological Survey of Canada, Report 1847-48, p. 58; also American 

 Journal of Science (2), IX. 19. 



t American Journal of Science (2), L. 83. 



