Crosby's map of eastern Massachusetts represents an area of slate, or argillite, as it is termed, running from Worcester through Lancaster and Pepperell to the New Hampshire state line. The eastern part of this argillite, two and one-fourth miles wide on the map, but four miles wide according to the text, continues north into New Hampshire just west of the Nashua River. On the east of the argillite lies mica schist in an area very narrow (three-fourths of a mile) near the state line, but much wider toward the southern part of the township of Dunstable. On the west of the argillite lies gneiss close to the state line, but mica schist a little farther southwest (in Townsend).
Proceedings of the Iowa Academy of Sciences
©1895 Iowa Academy of Science, Inc.
Tilton, J. L.
"The Area of Slate Near Nashua, N.H.,"
Proceedings of the Iowa Academy of Science, 3(1), 66-71.
Available at: https://scholarworks.uni.edu/pias/vol3/iss1/19