NEW HAMPSHIRE. 393 



Washington River, .... there is a limited synclinal of ossipyte resting upon 

 the upturnt'tl etlges of the andalusite gneiss." (Proc. Bost. Soc. Nat. Hist., 

 1873, XV. pp. 30-1-310.) 



In the second volume of the New Hampshire Geology, Prof. Hitchcock 

 writes as follows : — 



" Another important doctrine relates to the identification of formations in 

 our field of labor by means of mineral characters The style of similar- 

 ity made use of for identification is better shown in the porphyritic gneisses. 

 There are over thirty areas of porphyritic gneiss, in which the feldspar crystals 

 are very conspicuous for their size, the rock being the Augen gneiss of Europe I 

 assume that all the areas of this rock are identical in age, and, in speculating 

 upon the relative positions of the intervening groups, rely upon the correctness 

 of this starting point The fact of minor differences would seem to con- 

 firm our assumption of their identity in age, just as the paleontologist finds, 

 from the presence of the same fossils, proof of contemporaneity in rocks with 

 dissimilar mineral character. From these facts [the supposed relations of the 

 rocks] it is inferred that the porphyritic gneiss is older than either the Lake or 



the Montalban gneisses, the last being the newest It may as well be 



said now as at any time, that nothing older than the porphvritic gneiss has 

 yet been discovered. This formation constituted the first dry land in the 

 state." (1. c, pp. 659, 660, 663, 664.) 



The equivalency of the New Hampshire formations with others is in 

 part stated as follows : — 



" The first two of our groups may be referred to the oldest of these, the Lau- 

 rentian, without great hesitation A porphyritic or augen gneiss is emi- 

 nently characteristic of the fundamental rocks in every part of the world, and 



hence ours may readily be called Laurentian Those who are familiar 



with the cr\"stallines, as Prof. Dana and Dr. Sterry Hunt, after examining some 

 parts of the Bethlehem group in New Hampshire, say that there is a close 



resemblance between them and the Laurentian I have grouped these 



rocks, the porphyritic and Bethlehem gneiss, as Laurentian. 



" The next division, the Lake gneiss, cannot be so readily assigned. Its 

 affinities are strongly with the Laurentian, but it is not pyi'oxenic nor jjorphy- 



ritic, nor does it abound in any triclinic feldspar In Massachusetts this 



group carries the Eozoon, but that fossil is not confined to the Laurentian, 

 .... The Montalban series are certainly not characteristic of the Laurentian. 

 .... Dr. Hunt is satisfied that they overlie the Huronian or greenstones. 

 Our own observations lead to the \'iew that the typical Montalban rocks un- 

 derlie the same, as recently stated, though the precise relationship is not beyond 

 controversy." (I. c, pp. 668, 669.) 



The other formations are in like theoretical manner referred to their 

 supposed places, with the exception of the Helderberg series. 



