360 A. WTNCHELL — RESULTS "l AJtCHEAN STUDIES. 



strikes. The late survey of New Hampshire is apparently compelled to 

 limit itself largely to a Btudy of the surface distribution of the crystalline 

 rocks. It seems to be impossible to grasp the general structure in one con- 

 ception. In the pages of description little use is made of phenomena of dip 

 and Btrike. It is true thai pages are devoted to tables of dip and strike, but 

 they stand a- Isolated and meaningless facts. The neglect to unity them in 

 a structural conception is apparently due t<> the extreme difficulty of the 

 task. There is little persistence of dip or continuity of strike. The figures 



in contiguous regions are as diverse as can be c seived . In the midst ol 



this bewildering chaos Professor Hitchcock has recognized certain generali- 

 sations which lie on the road to a correct interpretation, but it was impos- 

 sible, in the light of facts then in possession of geologists, to follow their 

 leading to a full solution of the Archaean problem. To these I shall refer on 

 some Bubsequent occasion. 



The intricacies of rock-arrangement through western Massachusetts are 

 represented in the conflict over the Taconic question, the Bounds of which 

 have not yet ceased to reverberate. These obscurities were traced by the 

 brothers Rogers into Pennsylvania and Virginia. In eastern Massachusetts 

 the lithologic arrangements are so ambiguous that the able geologists who 

 live upon them are undoing each other's schemes of interpretation with a 

 zeal and emphasis which would seem to imply that opposites must both and 

 all be true. In the Canadian field the remarkable structural investigations 

 of Sir William Logan and his co-laborers have long since shown a state of 

 disturbance which sets all method at defiance. The truth of this is illus- 

 trated in almost every annual report published from 1842 to 1866. 



Quite in contrast with these structural complications is the lithologic Bys 

 tern of northeastern Minnesota. From Vermilion lake to South Fowl lake 

 the semi-crystalline Bchists pursue a Btrike varying little from east-northeast 

 for a distance of twenty ranges of townships, or about 130 miles along the 



strike. Beyond this they extend, largely <• sealed by overlying pre-Silurian 



rocks, in the same genera] direction to Thunder bay, 15 miles further. 

 Throughout tin- distance the schi>t> present hut a single told, and their 

 structural relation- to each other and to the crystalline schists and gneU 



of higher antiquity bee ■ a matter of comparatively easy observation. In 



tin- regions west and northwest of Vermilion lake, at least as tar a- tie- Lake 

 of tin- Woods, similar simplicity of structure prevails, though, so tar a- I 

 know, there is no other area of equal extent in whioh a single system of dip- 

 ami striki - persists throughout. 



i ii Bltehcocl and J. H. Hunting! '■ I. II. 1877. chapi r to *, 



pl.xxl, p coroplejfiv <>( tho 



e<] in the tweli llona acroa* the State shown In the Vila- rlbed in 



Vol li. i In the numerous and i < -'•' forth In the 



• i lie Bui i ■ 



