In the White River basin only the valleys are wooded, the timber extending less than a thousand feet up their sides, while the greater part of the plateau surface is practically treeless. The timber line on the northern side of the St Elias mountains has an altitude ‘of about 4,500 feet. The Chittenah and Copper river valleys feel the influence of the coast climate, and their vegetation is consequently much more luxuriant than in the valleys of White River basin. Character of the Observations.Any attempt to solve the many difficult problems connected with the geology of the region traversed would necessitate detailed study of large areas. The op-portunities afforded by a hasty reconnaissance along a single line of travel are obviously inadequate to the solution of these problems, particularly when the greater part of the geologist’s energy is absorbed in overcoming the physical obstacles to his progress and in making even the crudest topographic map to which to refer his observations. The most satisfactory information on the hard geology of any portion of this region is contained in Dawson’s report, already cited, on the geology of the Yukon district. Dr Dawson had the great advantage of familiarity with similar rocks and geologic problems from previous study in British Columbia. He was also in a position to control the movements of his party, and so was able to give more than a passing glance to points of special importance. Since the writer was without previous acquaintance with the rocks of the Cordilleran system and had no opportunity for observation, except as it was afforded along the route or at stops selected without reference to the geology, the information obtained is offered only as supplementary to the observations made by others and as preliminary to the more thorough study of those who may hereafter visit the region.