390 A. \\'IN< IIKI.I. — RESULTS OF A.RCHEAN STUDIES. 



Waiving the question of the taxonomic separability of the granitoid and 

 gneissoid rocks, the fundamental contrasts in condition seem fully to justify 

 the conclusion thai a historic break occurs above the gneissoid rocks and 

 another above the crystalline schists. A.bove the Bemi-crystalline .-dusts a 

 wide stratigraphic unconformity adds its evidence thai we find lure also a 

 boundary between two systems. The stratigraphic conformity between the 

 second and third, and the third and fourth systems is probably at variance 

 with prevailing opinions, and such a persistenl conformity of structure is a 

 fit subject for careful consideration. As I desire in this place simply to pre- 

 Benl tacts. [ will only Bay thai I do not imagine the present conformity im- 

 plies an original parallelism of beds of sedimentation. 



The crystalline gradation, from bottom to top of the general aeries, is 

 simple and remarkable. There are no granites superior to the gneissic zone; 

 there are no gneisses superior to the zone of crystalline schists. A.bove the 

 zone of crystalline schists no true crystalline schists occur again. The 

 " nascent mica schists'' of the fourth section retain the palpable evidences of 

 their fragmental origin. We arc not mel by the anomaly of recurring mica 

 schists at two or three different horizons. As there was only one age of 

 gneisses, so there was only our age of mica schists. So, again, the fourth 

 was the age of argil lites, felsite schists, and volcanic tuffs, while the fifth lies 

 ou the hither side of a great continental movement, and is marked, like the 

 preceding ages, by characteristic lithologic conditions — its carbon-freighted 

 argillites, and its floods of silicated wat< rs. 



With this observed simplicity of structure, we should entertain great con- 

 fidence in proposing a final classification were it not necessary to correlate 

 the results with those announced by eastern investigators. Where docs the 

 Huronian belong ? Where the Taconic? Where the Moutalban? Where 

 the l - -roup, and the other divisions of Ne\t Hampshire? We wish to 

 know, also, how these divisions stand correlated to the Dimetian, the Lewis- 

 ian, the Arvonian, and the iVlu'dian of ( Meat Britain, and with the divisions 

 of the Scandinavian scale. To some of these questions I have formulated 

 answers in my own mind: hut I do not deem it judicious to extend this me- 

 moir, for the same reason, 1 defer all the more detailed discussion on the 

 petrography of the Bevera] aystema and on all theoretical questions, such a- 

 the origin of the iron ores ami the accompanying Biliceoue and jaspi ry Bchiste ; 

 the conditions of origin of the pyro-clastic rocks; the cause .it' the foliation 

 in crystalline rocks; the relative agee of the granite- and gneisses; and the 



testa and history of massive rocka which, by recenl opinion, have been by 

 • neral consent relegated to the class of eruptives. 



