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§§ 270, 271] presented by the various planets, and in particular studied the visible features of the moon with a minuteness and accuracy far exceeding that of any of his predecessors, and made some attempt to deduce from his observations data as to its physical condition. His two volumes on the moon (Selenotopographische Fragmente, 1791 and 1802), and other minor writings, are a storehouse of valuable detail, to which later workers have been largely indebted. 23