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Grinnell and Sperry Glaciers, in Glacier National Park, Mont., have both shrunk considerably since their discovery in 1887 and 1895, respectively. This shrinkage, a reflection of climatic conditions, is evident when photographs taken at the time of discovery are compared with later photographs. Annual precipitation and terminus-recession measurements, together with detailed systematic topographic mapping since 1900, clearly record the changes in the character and size of these glaciers.
Arthur M. Johnson (Tue,) studied this question.