Merrill, Robert H., 1881-1955, “Glacial groove in Silurian Diabase,” Digital Collections, accessed December 12, 2025, https://digitalcollections.library.gvsu.edu/document/49684.
Black and white photograph of a glacial groove in Silurian Diabese on Mount Washington. Scattered rocks and stone are visible between two large boulders with field grasses in the background.