Page:Popular Science Monthly Volume 68.djvu/55

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accurate reconnaissance map, with elevations indicated by contours; but where time pressed, a canoe traverse, with estimated distances, was substituted. Fortunately it proved possible to carry a rough triangulation, checked by latitude and azimuth observations, throughout much of the explored regions. The topography was sketched, on a field scale of about three miles to the inch, with the aid of a plane-table. Altitudes were determined as far as possible by vertical angles, but in many instances depended solely on the readings of aneroid barometers. Contours were sketched at intervals of 200 feet, or, if the topography was very rugged, 500 feet. In some cases it was possible to run stadia lines along the rivers, and salient topographic points were located by intersections. Though some of the journeys were accomplished under exceeding difficulties, in no instance were the surveys entirely interrupted.

The movements of the party were guided more by the requirements of the topographic than of the geologic surveys, and the geologist was perforce required to get such information as he could. Continuous series of notes were kept and specimens were assiduously collected. Special attention was given to the occurrence of placer gold and other metalliferous deposits, but all phases of geologic problems were studied as far as circumstances would permit. Probably the most important scientific results were those that had to do with the general physiographic problems. In most cases only the broader features of the stratigraphic succession could be determined, but even these results,