278 GEOGNOSY OF THE APPALACHIANS. [XIII. 



land is regarded as Laurentian. This, on Credner's map, is 

 also made to include, with the exception of the White Moun- 

 tains themselves, all the rocks of the third or White Moun- 

 tain series, which cover so large a part of New England. Those 

 who have followed the historical sketch already given can see 

 how widely these notions of Credner differ from those of Em- 

 mons, and from all other American geologists, and how much 

 they are at variance with the present state of our knowledge. 

 It is much to be regretted that so good a geologist and litholo- 

 gist should, from a too superficial study, have fallen into these 

 errors, which can only retard the progress of comparative ge- 

 ognosy, for which he has done so much. In England, again, 

 Credner confounds the Cambrian and Huronian, referring to 

 the latter system the whole of the Longmynd rocks with their 

 characteristic Cambrian fauna, a view which is supported only 

 by the conjectured Cambrian age of the crystalline schists of 

 Anglesea, which are pre-Cambrian and probably Huronian, like 

 the Urschiefer of Scandinavia, which Credner correctly refers 

 to the latter system, as Macfarlane and Bigsby had done before 

 him. He, moreover, recognizes in the similar crystalline schists 

 of Scotland, the Urals, and various parts of Germany, includ- 

 ing those of Bavaria and Bohemia, a newer system, overlying 

 the primary or Laurentian gneiss, and corresponding to the 

 Huronian or Green Mountain series of North America ; while 

 he suggests a correspondence with similar rocks in Japan, Ben- 

 gal, and Brazil. In a collection of rocks brought from the 

 latter country by Professor C. F. Hartt, I have found, as else- 

 where stated,* what appear to be representatives of the three 

 types of crystalline schists which have been distinguished in 

 eastern North America. 



[I have not in the preceding discussion alluded to the Norian 

 series, otherwise called the Labradorian or Upper Laurentian, 

 for the reason that although largely developed in the southern 

 part of the Adirondack region, it does not occur on our line of 

 section, and, moreover, was not certainly known in the Appala- 

 chians. Subsequent observations of the Geological Survey of 



* The Nation, December 1, 1870 ; and Hartt's Geology of Brazil, p. 550. 



