ALGONKIAN ROCKS IN VERMONT. 399 



below the Olenellus quartzite into two periods is thought to 



occur. 



GEOLOGY. 



Oiitlme of the views previously held regarding the structure and 

 age of the Green Mou?itai?is. — As far back as 1845, Adams in his 

 first Annual Report on the Geology of Vermont^ referred to the 

 "Primary" system the rocks of the main range of the Green. 

 Mountains as far as the state boundary, and eastward. Among 

 the rocks mentioned under this head which occur in the area 

 studied by me are Green Mountain Gneiss, Mica Slate and Tal- 

 cose Slate. In this report these horizons are placed below the 

 Stockbridge limestone and the associated quartzite of the Taconic, 

 but their relative age is confessedly unknown. In his second 

 annual report,^ however, he leaves the problem as to whether these 

 are "Taconic," "Primary," or " Metamorphic," an open question, 

 but still inclines towards a belief in their primary origin. This belief 

 is inferred from his statement that the evidence goes to show that 

 the limestone and quartzite of Plymouth valley on the east side 

 of the range is equivalent to the Stockbridge limestone and quarz- 

 ite on the west side, making the core of the Green Mountains the 

 older. Adams in no place makes the statement that the belt of 

 primary rocks represents the axis of the range, and it is doubted 

 if he had any clear conception of the relations of the rocks on 

 the east and west sides of the Green Mountain divide. In 1847, 

 however, Edward Hitchcock gave two sections in his text book of 

 Geology 3 of the Green Mountain anticline partially and com- 

 pletely folded as we see it to-day. The anticline is represented 

 as overturned slightly to the west, with a flat crest and a rude fan- 

 shaped cross-section; the texf^ mentions that the strata grow 

 newer as one goes westerly, although apparently the series is 

 descending. Such a conclusion reached at that time is the 

 happy result of a coincidence of schistosity and stratification at 



'p. 62. 



=^ Second Annual Report on the Geology of Vermont. Adams, 1846, p. 168. 



3 Elementary Geology, Edward Hitchcock, 1847, figs. 27 and 28, p. 37. 



"•Opus, cit., p. 36. 



