106 



THE CAMBRIAN. 



[BULL. 81. 



The Red sand rock is described as extending- from St. Arm and, prov- 

 ince of Quebec, to Bridport, Vermont. 



The brightest red rocks are found along the western border ; so that while the alli- 

 ance of the red rock of Burlington and the quartzite of Bennington seems incongru- 

 ous, it is otherwise with the reddish rocks of Monktou and the brown quartz of 

 Starksboro' and Bristol. 1 



It is stated that the name Georgia was applied to the group of slates 

 carrying Olenellus. It was then supposed that the slates were entirely 

 distinct from the sandstones, but further investigation has shown an 

 interstratification, with the presence of the characteristic trilobites 

 throughout the beds. 



Of the " Granular Quartz " on the western slope of the Green Moun- 

 tains he says : 



No rock can be more distinct from all others than the quartzite from the State 

 line north to Starksboro', consisting chiefly of pure vitreous silica, sometimes hardly 

 showing a sedimentary composition. * * * The group makes a mountain range 

 throughout, some of the peaks exceeding 3,000 feet in height. * * * An abun- 

 dance of Scoliihus linearis appears in this formation, and the rock was referred to the 

 Potsdam in 1841 by H. D. Rogers and W. B. Rogers, in opposition to E. Emmons, who 

 subsequently called it " granular quartz," lying at the base of the Taconic system, 

 thousands of feet below the former. 1 



In 1871 Mr. S. W. Ford 2 published an account of a section of rocks at 

 Troy, New York, in which he had found the Olenellus fauna. In 1884, 

 he added 3 a description of a section near Schodack Landing, south of 

 Troy, in Columbia County, New York. By the contained fauna the 

 strata were correlated with those described by Sir William Logan, in 

 Vermont, Canada, and Newfoundland. 



Prof. J. D. Dana, 4 from 1872 to 1877 worked out, with considerable 

 detail, the stratigraphic relations of the " Granular Quartz," of Berk- 

 shire County, Massachusetts, to the subjacent Archean and the super- 

 jacent Silurian limestone, adding many details to the general outlines 

 published by Messrs. Eaton, Dewey, and Emmons. In the description 

 of the quartzite, limestone, and associated rocks of Great Barringtou, 

 Berkshire County, Massachusetts, 5 it is stated that the quartzite of Great 

 Barrington alternates with mica schist, and that both of the rocks for 

 the most part overlie the Stockbridge limestone. Of the Green Moun- 

 tain quartzite, Prof. Dana says: 6 "In the first place there are quartzites 

 of more than one age in New England, west of the Connecticut River." A 



•Op. cit., p. 3. 



2 Notes on the Primordial rocks in the vicinity of Troy, New York. Am. Jonr. Sci., 3d ser., vol. 2, 

 1871, pp. 32-34. Can., Nat., new ser., vol. 6, 1872, pp. 209-212. 



3 On the age of the glazed and contorted slaty rocks in the vicinity of Schodack Landing, Rensselaei 

 County, New York. Am. Jour. Sci, 3d ser., vol. 28, 1884, pp. 206-208. 



4 Green Mountain geology. On the quartzite. Am. Jour. Sci., 3d ser., vol. 3, 1872, pp. 179-186, 250- 

 256. An account of the discoveries in Vermont geology of the Eev. Augustus Wing. Am. Jour. 

 Sci., 3d ser., vol. 13, 1877, pp. 332-347, 405-419 ; vol. 14, pp. 36-37, 1877. 



6 On the quartz, limestone and associated rocks of the vicinity of Great Barrington, Berkshire 

 County, Mass. Am. Jour. Sci., 3d ser., vol. 4, 1872, p. 3G2. 

 6 Green Mountain geology. On the quartzite. Am. Jour. Sci., 3d ser., vol. 3, 1872. p. 181. 



