326 RED SANDROCK. 



Windmill Point, W. Alburgh, Sand and pebbles. 



Savage Point, W. Alburgh, Utica slate. 



South end of Alburgh, Utica slate. 



Alburgh Springs, Utica slate. 



Hog Island, Hudson River slate, mostly covered with alluvium. 



Highgate Springs, Trenton limestone. 



East part of Missisco Bay, Limestone of the upper part of the Hudson River 



Group. 



RED SANDROCK SERIES. 



GEAY SANDSTONE (Upper Silurian): Geology of the Second District of New York. By 

 E. Emmons, page 282 ; 1842. 



RED SANDROCK (Lower Silurian) : Second Annual Report on the Geology of Vermont. By 

 C. B. Adams, pages 85, 163 ; 1846. 



AGE OF THE MEDINA SANDSTONE : In a paper communicated to the American Association 

 for the advancement of Science at the Albany meeting, 1851 (not published) . By W.B. 

 Eogers. 



LOWER PART OF THE QUEBEC GROUP AND EQUIVALENT TO THE ONEIDA CONGLOMER- 

 ATE (Middle Silurian) : Canada Eeports. 



POTSDAM SANDSTONE AND CALCIFEROUS SANDSTONE: American Geology. By E. Emmons, 

 Vol. I, Part II, pages 88, 128 ; 1855. 



"Or THE PRIMORDIAL ZONE: " Eemarks on the Fauna of the Quebec group of Hocks, and 

 the Primordial Zone of Canada ; addressed to Mr. Joachim Barrande. By Sir W. E. Logan, 

 Director of the Geological Survey of Canada, Jan. 3, 1861. 



The following is an extract from a paper entitled "Notes on the Geological Structure of Western 

 Vermont, etc.," communicated by Prof. William B. Rogers, of Boston, to the American Association for 

 the advancement of science, at its Albany meeting in 1851, but not printed in the proceedings of that 

 Society. It may be useful in the investigation of the history of the red sandrock series : 



" The general geological position of the red rocks here spoken of, is clearly seen by following either of the 

 sections, from the western base of the Snake and Buck Mountains, across the trough or valley above 

 described. Here we ascend through the various divisions of the matinal series, from the Trenton to the 

 top of the Hudson River Group as here denned, each marked by characteristic fossils, and all maintaining 

 a nearly uniform eastern dip; and above the latter we find a series of red and greenish and gray sandstones 

 and shales of great thickness, succeeded, where the exposures are unbroken, by arenaceous and argillaceous 

 reddish and gray limestones, alternating with beds of sandstone similar to that beneath. 



" Stratigraphically considered, this series of beds occupies the position of the Medina group of New 

 York, or its equivalent, the Levant series of Pennsylvania and Virginia. The sandstones and shales bear 

 a close resemblance to those of the latter, not only in color, but in the profusion of fucoid-like markings 

 which they display on some of the parting surfaces. The series of reddish and gray limestones which rest 

 upon these massive arenaceous beds form an interesting feature in the geology of Vermont. Their alterna- 

 tion with layers of sandstone and shale, and their frequently reddish tint, would lead us to regard them as a 

 continuation of the lower "mass under somewhat new formative conditions. In the prolongation of this 

 belt of sandstones and limestones toward the north, as at Winooski Falls, near Burlington, the latter mass 

 is seen to consist, in great part, of a pinkish white fine-grained limestone, which toward the base contains 

 layers of reddish limestone, interstratified with red sandstone, marking the transition from the arenaceous 

 to the calcareous form of deposit. 



