52 NEW YORK STATE MUSEUM 



grit. There does not seem to be good evidence to show that 

 the sea covered this area after the Green Mountain upHft until 

 later Upper Siluric or Devonic time. This is made apparent 

 when we consider that the Rensselaer grit occupies an area that 

 was highly involved in the disturbances at the close of the Cham- 

 plainic period. 



In tracing the Siluric formations north from Ulster county,, 

 the Shawangunk conglomerate is the first to fail, and the suc- 

 ceeding formations fail by overlap in regular order until at 

 Becraft mountain in Columbia county the Manlius as already- 

 pointed out rests unconformably upon the Champlainic strata.. 

 This shows that as we approach the Rensselaer grit area, only 

 the highest members of the Upper Siluric are present, and the- 

 conditions of overlap of these formations clearly indicate that 

 the Rensselaer grit is not of Shawangunk age. 



In tracing the Upper Siluric formations eastward from centra! 

 New York, the Oneida is overlapped by the Clinton, and irt 

 Albany county but 17 miles from the Rensselaer grit plateau, the 

 Manlius and a few feet of the Rondout are the only members of 

 the Upper Siluric present. From this it does not appear that the 

 Rensselaer grit can be correlated with the Oneida conglomerate.* 

 The submergences and emergences, which involve the conditions 

 of overlap following the Taconic revolution, have been stated i» 

 detail by Ulrich and Schuchert.^ 



Structural relations of the Townsend iron mine. The Town- 

 send iron mine was fii*tet described by Horton^ in 1839 ^-S follow^s: 

 " Two and a half miles west of Canterbury, in Cornwall, is the 

 hematite or limonite mine of Mr. Thomas Townsend. For the 

 last two years this ore has been considerably used and although 

 a lean ore, it makes excellent iron. It is mostly in powder, or 

 very small fragments, mixed with balls and pieces of the hema- 

 tite, of a few pounds weight. It lies in a limestone rock, and 

 between the limestone and the grit rock. These rocks where 

 connected with the ore, are decomposed to great extent, and 

 mixed in a state of powder wdth the ore ; hence the ore requires- 

 washing." 



This limestone was definitely correlated by Mather *'^ with 

 what are now recognized as the New Scotland beds. He states, 

 "The Strophomena rugosa Dalman and S. r a d i a t a: 

 Sowerby are very common fossils at the above locality, and the 



iSee Dale, U. S. Geol. Sur. Bui. 242. 1904. p. 53. 

 2N. Y. state Pal. An. Rep't, 1901, p. 647. 66°- 

 3An. Rep't ist Dist. 1838 (1839) p. 165. 

 4Geol. N. Y. ist Dist. 1843. p. 351. 

 5See also plate 5, figure 14. 



