PALEOZOIC TIME. 461 



work, American geology owes much to De Verneuil for his " note " of 64 pages in the 

 Bulletin of the Societe Geologique de France, iv., 1847, "On the Parallelism of the Paleo- 

 zoic Formations of North America with those of Europe," which is followed by a list of 

 the species of fossils common to the two continents, and of the rocks in which they occur, 

 with critical remarks respecting each species ; and to the paper of D. Sharpe, " On the 

 Fossil Mollusks from the Paleozoic Formations of the United States," contained in the 

 collections of C. Lyell, Q. J. G. Soc, 1848. 



AREAS OF GEOLOGICAL PROGRESS. 



Archgean geograpliy, as has been explained, largely determined the areas 

 of later geological progress, and the character of continental geography 

 through all the ages. The prominent points in North American geography, 

 besides the fundamental one of the Archaean nucleus, are the defining of the 

 two great Archaean chains of islands or island ridges, the Appalachian pro- 

 taxis on the east, the Rocky Mountain protaxis on the west (page 24). By 

 this means a vast Interior Continental Sea was divided off from an Atlantic 

 border region on the east, and a Pacific border region on the west, the former 

 (reckoning to the 100-fathom line, or the steep border of the Atlantic depres- 

 sion) averaging 300 miles in width, but becoming three times this in the 

 latitude of ISTewfoundland ; the latter, 1000 miles in mean width. 



Besides this, the shorter Archaean ranges of the Atlantic border region 

 to the north (see the map) divide the surface into a parallel series of broad 

 channels or troughs, all of which open northward into the St. Lawrence 

 valley region. 



1. The Champlam and St. Lawrence channel : between the northern part 

 of the protaxis and the Archaean lands ; on the west stand the Adirondacks, 

 and on the north the Canada Archaean. 



2. The Connecticut valley channel, or trough, along the Connecticut 

 valley, and reaching Long Island Sound at New Haven Bay, Conn. 



3. The Maine-Worcester channel : covering Maine and western New Bruns- 

 wick and extending down to Worcester, Mass. ; apparently fading out south- 

 ward. The fiord of the Thames River, from Norwich to New London, Conn., 

 lies in its course. 



4. The Acadian channel : extending from St. Lawrence Bay and western 

 Newfoundland over eastern New Brunswick and much of Nova Scotia, with 

 the Bay of Fundy between, as the remains of this part of the depression ; 

 thence southeastward along and off the coast regions of Maine to Massachu- 

 setts Bay, and over eastern Massachusetts to Narragansett Bay, on the 

 Atlantic border. 



5. The Exploits River channel of central Newfoundland, and two others 

 to the eastward. 



The importance of these channels, or troughs, becomes strongly pronounced 

 in the course of Paleozoic history. 



Over the Pacific border region the areas are less plainly indicated than 



