January 8, 1897.] 



SCIENCE. 



43 



existed were those giving the general fea- 

 tures of the larger drainage systems on 

 which was no connected or systematic rep- 

 resentation of the surface features ; in cer- 

 tain limited areas the relief was sketched 

 in by hachures, or, as in Egglofstein's maps, 

 by delicate shading. 



On the Great Plains it was known that 

 Mesozoic and Tertiary formations formed 

 the greater part of the surface, and the 

 Cretaceous rocks had been divided by Meek 

 and Hayden into five subdivisions. Around 

 the Black Hills, Lower Silurian and Car- 

 boniferous rocks had been identified. Car- 

 boniferous limestones were known to have 

 a considerable extension in the interior re- 

 gion in middle and southern latitudes, and 

 to have been seen in the northern part of 

 the Sierra Nevada. The age of the up- 

 heaval of the latter range had been deter- 

 mined to be post- Jurassic, by the discovery 

 by Clarence King, of the State Geological 

 Survey of California, of Jurassic fossils in 

 the auriferous slates. It was conjectured, 

 reasoning from their association in the 

 Black Hills, that Silurian beds would ulti- 

 mately be found associated with the Car- 

 boniferous, but the discovery of Devonian 

 fossils in central Nevada by Engelmann in 

 1859 had not yet been made public. It 

 was known in a general way that igneous 

 rocks, granites and metamorphic rocks 

 were widely distributed throughout the in- 

 terior, but of their mutual relations, or 

 the actual structure of the mountain ranges, 

 there was little but surmise, and not very 

 much of that. 



As regards the physical conditions of the 

 interior, although the region east of Salt 

 Lake was known to be well watered, in the 

 desert region of the Great Basin to the 

 westward, it was not supiposed that cam- 

 paigning was possible, except along certain 

 lines of emigrant travel, and on these it 

 was known that there were inconveniently 

 long stretches without water. 



King Survey. The Geological Explo- 

 ration of the 40th Parallel, as it was offi- 

 cially known, was entirely the creation of 

 its chief, Clarence King. The first concep- 

 tion of the feasibility of making a geologi- 

 cal cross section of this, the longest moun- 

 tain system in the world, at its widest part, 

 had come to him during his long three 

 months' journey with an emigrant train 

 from Missouri to the Sierra Nevada, which 

 he undertook in the summer of 1861. His 

 personal influence had, during the winter 

 of 1866-7, secured the passage of a bill 

 through Congress creating the 40th Parallel 

 Survey, whose duty it was to examine into 

 and report upon the geology and mineral 

 resources of the country to be opened up 

 by the Pacific railroads. At his suggestion 

 it was placed under the oflicial direction of 

 Gen. A. A. Humphreys, Chief of Engineers, 

 in whose scientific ability he had the great- 

 est confidence. 



His plan of work contained much that 

 was novel and startling, especially in con- 

 sideration of the desert character of the re- 

 gion in which it was to be carried out. 

 This plan contemplated making a topo- 

 graphical map of the region surveyed, not 

 simply a map of meander lines, with 

 sketches in hachures of the hillsides, which 

 was the only form of relief map known at 

 that time, but a contour map on the same 

 general plan with the Survey maps of the 

 present daj'^, controlled by systems of pri- 

 mary and secondary triangulations, the 

 relative elevations to be determined by fre- 

 quent observations of cistern barometers. 

 The scale adopted was four miles to the inch. 

 Besides the usual botanical and zoological 

 assistants, an excellent photographer was 

 attached to the party. The area to be sur- 

 veyed, which was always to include the 

 line of the projected railroad, was divided 

 into rectangular blocks or atlas sheets, about 

 165 miles in length by over 100 miles in 

 width. The original plan contemplated 



