6/0 STRATIGRAPHICAL GEOLOGY. 



The greenstones of our state seem to be closely allied to the upper Hu- 

 ronian, and the porphyries of Lynn, etc., Mass., to the lower division. It 

 is possible that our supposed eruptive porphyries of the White Moun- 

 tains belong to this lower division. They certainly possess the same 

 lithological features, and in some cases have been protruded through 

 what we consider the upper division. A different view has been taken 

 of these greenstones. Sir W. E. Logan regarded them as the altered 

 Quebec group of the Cambro-Silurian ; and we find this view carried to 

 a fatal extreme by Prof. F. H. Bradley, who insists that the original typi- 

 cal locality on Lake Huron is the same Silurian group metamorphosed, 

 so that there is no such thing as Huronian in existence. If logic carries 

 the theory to such an extreme, we need not be troubled to defend the 

 Huronian, since there are few points in American geology better estab- 

 lished than the inferiority of the Huronian grits to the Cambro-Silurian. 

 We claim not merely lithological evidence to support the reference of 

 certain New Hampshire rocks to the Huronian system, but also that 

 the study of the stratigraphical relations of the several Canadian sec- 

 tions (Plates II, III, and IV) indicates a similarity in the order of the 

 various groups. The Green Mountain gneisses, being either of the Mont- 

 alban or Lake series, clearly underlie the Huronian in the East, just as 

 the ancient gneisses do in Ontario and Michigan. We have a different 

 classification of the Huronian in New Hampshire from t^at in Canada. 

 No one yet understands the system sufficiently thoroughly to institute 

 close comparisons, though only study is required to discover the proper 

 correlation. 



There is no reliable evidence yet in our possession to enable us to 

 locate the precise place of the Merrimack, Rockingham, and Kearsarge 

 groups of mica schist. The first is somewhat related to the Huronian, as 

 well as in its argillaceous beds to the Cambrian. They are all referred to 

 the Paleozoic system in our table, with a large interrogation point. The 

 slates of the Connecticut valley are called Cambrian, because they are 

 supposed to be the equivalent of the Paradoxides beds. The various 

 members of the Coos group are ranked as Paleozoic, without direct evi- 

 dence of their proper place. The same is true of the Calciferous mica 

 schist. Logan referred it to the Niagara limestone. No fossils, except 

 very obscure minute crinoidal fragments, have been found in it. Noth- 



