Their early acquisition of the horse may have allowed the Shoshone to penetrate the northern plains as far as Saskatchewan in the early eighteenth century, for David Thompson's journals tell of warfare between the Blackfoot and Shoshone in that region at some time in the 1720's or early 1730's (Tyrell, 1916, pp. 328 ff.). The northerly extension of the Shoshone in the early horse period, and perhaps before, has been discussed and generally accepted by many students of the area (cf. Wissler, 1910, p. 17; Shimkin, 1939, p. 22; Ewers, 1955, pp. 16-17; Hultkrantz, 1958, p. 150). There is little information on Shoshone population movements between this date and the journey of Lewis and Clark. In 1742 the de la Verendrye brothers undertook an expedition into the northern plains of the United States and reported upon the ferocity of a people known to them as the "Gens du Serpent," presumably the Snake, or Shoshone. De la Verendrye wrote of these people (Margry, 1888, p. 601): No nation is their friend. We are told that in 1741 they entirely laid waste to seventeen villages, killed all the men and old women, made slaves of the young women and traded them to the sea for horses and merchandise. The Gens du Serpent are not precisely located, but the explorers were told by the "Gens de Chevaux" that they lie in the path to the western sea. Later, a "Gens d'Arc" chief invited them to join in an expedition against the Gens du Serpent on "the slopes of the great mountains that are near the sea" (p. 603). They later found an abandoned enemy village near the mountains, but returned without further contact. Shimkin believes that this village was in the Black Hills (Shimkin, 1939, p. 22), but the journals are most hazy on geography. The previously cited information from the Gens d'Arc chief suggests that the group was located farther west, in the vicinity of the Rocky Mountains. It must be remembered, however, that there has been considerable contention among historians, not only over the route of the de la Verendrye brothers, but over the identification of the Gens du Serpent. L. J. Burpee has reviewed (1927, pp. 13-23) various conflicting interpretations of the journals, and the matter can hardly be considered settled.