CLASSIFICATION OF THE NEW HAMPSIIIRE FORMATIONS. 669 



The ]\Iontalban series are certainly not characteristic of the Lauren- 

 tian. Dr. T. Sterry Hunt has thoroughly discussed this formation in his 

 recent publications, to which repeated reference has been made in the 

 foregoing chapters. In Volume I, page 526, I proposed to have the word 

 Atlantic include the Bethlehem, Lake, Montalban, and Franconia groups, 

 signifying a system between the Laurentian and the Labrador, and 

 intending to restore an ancient use of the new word. After consultation 

 with geologists, I find this usage not altogether satisfactory. Hence in 

 the final classification I will drop the word Atlantic as applied to a dis- 

 tinctive system, using Montalban in its place. We retain the term 

 Atlantic, however, in a geographical sense, and understand it as defined 

 upon page 6. The Atlantic area includes geographically all the crystal- 

 line terrancs that aid in building up the mountains adjacent to the ocean 

 on the eastern border of the continent. There are Laurentian, Montal- 

 ban, and Huronian rocks within it. The Montalban will certainly em- 

 brace the characteristic rocks of the White Mountains, the Concord 

 granite, various ferruginous and fibrolite gneisses carrying the gigantic 

 veins, and the Franconia breccia. 



There is a point not yet made clear in the discussions about the rela- 

 tions of the Montalban rocks. Dr. Hunt is satisfied that they overlie the 

 Huronian or greenstones. Our own observations lead to the view that 

 the typical Montalban rocks tmderlie the same, as recently stated, though 

 the precise relationship is not beyond controversy. There can be no 

 doubt of the relation between the Berlin range of Lake gneiss and the 

 Huronian, as shown in Fig. 6 and Section XI. These statements indi- 

 cate the proper place to refer our Lake series. Inasmuch as it has cer- 

 tain affinities with the Laurentian, and clearly underlies the Huronian, 

 we may for the present place it with the former, and leave the question 

 of the relations of the Huronian and Montalban to be settled by other 

 considerations. Our Laurentian column will therefore consist of the 

 porphyritic, Bethlehem, and Lake gneisses. 



The word Huronian has just been applied to the greenstones. Much 

 has been said about this formation in the report, particularly a sketch of 

 its distribution in the best known localities in eastern America (pages 

 457-465). It appeared that there are two well marked divisions of this 

 system, the upper quite chloritic, and the lower quartzose and feldspathic. 



