142 



STRATIGKAPHICAL GEOLOGY. 



PEMIGEWASSET SERIES. 



In Chapters III and XV of the first vokime I have set forth in a his- 

 torical way the reasons which led me to describe the Pemigewasset series 

 of rocks, chiefly eruiDtive, as the probable equivalents of the Labrador 

 system of Logan and Hunt. I stated finally that the several rocks were 

 arranged in the following order, beginning with the lowest: Conway 

 granite, Albany granite, Chocorua granite, Ossipyte or labradorite rocks, 

 and various compact and crystalline feldspars or porphyries. Owing to 

 their particular geographical grouping, I believed all these members to 

 constitute parts of one grand system. This conclusion was derived from 

 the study of the specimens obtained from every part of the White Moun- 

 tain district, and was not properly comprehended till the field-work had 

 been essentially completed. There are difficulties in the way of accept- 

 ing these views, and I desire to investigate the subject further before 

 committing the report to the view already presented. I will not, how- 

 ever, depart from the established order in the description of localities and 

 other important matters, only premising that there may be some modifi- 

 cations of our general conclusions hereafter. One is often staggered 

 when attempting to realize the greatness of the task imposed upon us, — 

 to delineate truthfully the geological sequence of all the formations in 

 this unexplored territory. The difficulties in the way must bespeak the 

 indulgence of the scientific public in our favor, should we fail to discover 

 fully the true theory of the structure of the White Mountains. 



The Conway and Albany Granites. 



It will be convenient to describe both of these granites together, when 

 speaking of their occurrence on the sides of the mountains, and thus 

 avoid needless repetition. 



The Comvay granite was first described as the "common" variety in 

 the report for 1871, page 6. Its type appears at the Basin, Pool, and 

 Tlume in P'ranconia, Goodrich's falls in Jackson, and throughout the town 

 of Conway. The minerals composing it are the three normal constitu- 

 ents of granite, — quartz, feldspar, and mica, — each one being well devel- 

 oped, and so large as to be recognized without difficulty. The microscope 



