In the summer of 1921 the Montana Bureau of Mines and Geology commenced a reconnoissance survey of western Montana, following the completion of a reconnoissance of the central and eastern part of the State. During the first summer, G. S. Lambert, Arthur Bevan, and C. H. Clapp were the geologists, and in 1923 Roy Wilson joined the survey. From 1924 to 1928 the work was carried on in an unsystematic manner by C. H. Clapp, except in the summer of 1925 when he worked with J. H. Bradley, Jr., for three weeks in the confused group of mountains near the south end of the Flathead Range where it is joined by the Lewis and Clark Range. In 1929 C. H. Clapp, accompanied by G. E. Megathlin, began a more systematic study of the Lewis Range of Glacier Park and of the Flathead, and Lewis and Clark ranges. In 1930 . . .