Page:The Journal of geology (IA journalofgeology11893univers).pdf/361
the west, in a very undulating course, and marked by several transverse depressions, to a high isolated summit,[1] adjoining the north lines of the east of the North Ponds[2] (Salisbury)." (P. 129).
In a paper read before the American Association in 1873[3] Professor J. D. Dana quotes Percival as stating that the mica schist in which he found garnets in the township of Salisbury, is below the "Stockbridge or Canaan Limestone," but giving it as his own view that the schist is the overlying rock. This observation of Percival has considerable interest, for though the "Stockbridge or Canaan Limestone" has been shown to consist of two members, one of which is below and the other above the Staurolite-bearing rock, it is probable that Percival discovered a locality at which the Riga Schist comes out from below the Egremont Limestone.
On the map accompanying Professor Dana's paper entitled Taconic Rocks and Stratigraphy,[4] a number of schist areas are represented within the area here treated, which he correctly described to be, in some cases at least, "isolated within the limestone area,—as isolated as islands in a sea."[5] He mentions eleven of them in Salisbury and eight in the part of Sheffield township just north. He believed that there is but one schist horizon, which overlies the limestone, and described three localities, nearly or quite within the area studied, to sustain his views. These are, (1) the hill three miles north of Gallows Hill (locality 4, l. c., p. 213) where the schist "overlies the limestone"; (2) Turnip Rock (locality 5, l. c., p. 213) where schist overlies limestone in a shallow synclinal; and (3) Tom's Hill in Salisbury, which is described as a very flat trough of schist toward the north, but developing farther south into an overturned synclinal with its axis dipping east (l. c., p. 214). The observations made by