36 STRATIGRAPHICAL GEOLOGY. 



The Problem to be Solved. 



With the preceding general statements in mind, it will be proper now 

 to hasten to the special task before us of unravelling the tangled strati- 

 graphical structure of the New Hampshire formations. That the Atlantic 

 gneisses differ radically in lithological features from the Adirondack 

 schists, is universally admitted ; that they differ more markedly from the 

 Paleozoic groups of the St. Lawrence and Champlain valleys will be 

 obvious after detailed comparisons. That there are lithological resem- 

 blances between the porphyritic gneiss and hydro-mica schists of New 

 Hampshire, with portions of the typical Laurentian gneiss and the Huro- 

 nian rocks, every one will admit, and, if the order of their succession in 

 our field of labor agrees with that in the states and provinces adjacent 

 to us, where the structure has been determined, we shall be justified in 

 believing what is suggested by the similarities in mineral composition. 

 The satisfactory reference of our formations to those elsewhere described, 

 or else the establishment of a new series of groups, is the problem before 

 us to be solved. We propose now to describe the rocks in detail, taking 

 in order each of the topographical districts into which our territory may 

 be naturally divided, as stated in Volume I, page 171, beginning with the 

 most northern, and proceeding southerly. After the presentation of all 

 the facts, we shall be better prepared to discuss the correspondences 

 between our formations and those adjacent to us. Though the field may 

 now seem full of perplexity and confusion, we shall undoubtedly discover 

 the clue to complete order, and be surprised at the simplicity of the con- 

 ception which has determined the building up of our stratigraphical 

 column. 



Fig. 2. — TESCUEMACHER's figure of crystals of tin ore from JACKSON. 



