266 STRATIGRAPHICAL GEOLOGY. 



Eozoic age of the Green and White Mountain gneisses: — I. They are 

 the northward continuation of the Eozoic rocks of New Jersey, the high- 

 lands of New York, and their extension across the Connecticut hne. We 

 can trace them all the way from Alabama to Canada, — twelve hundred 

 miles, — and they are flanked by the same broad, fertile Cambro-Silurian 

 Appalachian valley on the west side all the way. An orographical map 

 of the coast regions of America will show this fact in a very satisfactory 

 manner. If the valley formations are the same through East Tennessee, 

 the great valley of Virginia, the limestone region of Pennsylvania, and the 

 Berkshire and Champlain valleys of New England into the St, Lawrence, 

 why should not the adjacent and continuous highlands, on their eastern 

 border, have been formed essentially in one and the same period, espe- 

 cially as they have been almost universally regarded as Eozoic south of 

 Connecticut ? 



2. Almost all the way the gneisses are bordered by a quartzite, usually 

 regarded as of Cambrian age. North of Adams, in Massachusetts, I have 

 examined four localities of a conglomerate connected with this quartz, 

 containing pebbles derived from the ruins of the formations to the east. 

 I suppose the whole mass has been derived from the same source, but 

 the fineness of the materials prevents its recognition. It should be re- 

 marked that there are no other formations from which it could have been 

 derived, save the Adirondack-Laurentian, which is from twenty to a hun- 

 dred and fifty miles distant. 



Two considerations are derived from the study of New Hampshire 

 rocks, 3. The discovery of the Labrador system, overlying the most 

 abundant and characteristic White Mountain strata, makes it clear that 

 the latter are older than the former, which are confessedly Eozoic, 4. 

 Fossiliferous Helderberg strata occur on the extreme west and north- 

 east of the White Mountains, the latter in Maine, There are no other 

 groups so likely to be metamorphosed into the Montalban schists as 

 these, yet they occur side by side with the metamorphic schists, with 

 their fossils. The schists occupy the elevated tracts, and they consti- 

 tuted the continental dry land when corals luxuriated in the calcareous 

 waters of the deep Connecticut Valley sea. 



5. The identification of the two oldest White Mountain groups with 

 the Laurentian is satisfactory, so that a portion of the debatable terri- 



