290 S. F. EMMONS UINTA MOUNTAINS 



expeditions that had penetrated it; but beyond this nothing was known 

 of its geological column. 



Methods of Work 



The work of the Fortieth Parallel geologists, it must first be noted, 

 did not claim to be a survey, but was explicitly called an exploration. It 

 was carried on in regions that not only had never been mapped, but of 

 which the topography, except in its very broadest features, was entirely 

 unknown. 



Each working, party consisted of a geologist, a topographer, and a 

 barometer-carrier, with the necessary camp men and military escort. 

 The necessities of topographic work required the occupation of every 

 peak in a mountain range; hence the location of the successive camps 

 was made rather with reference to the possibility of reaching such peaks 

 than because they were the best points from which to study the geology 

 of the surrounding country. In regions like the Uinta mountains, diffi- 

 cult of access and remote from any lines of communication, any revisit- 

 ing after the completion of field work was quite impracticable. 



So large were the areas laid out for the field work of each season that 

 the utmost speed was necessary in Order to go over the whole ground be- 

 fore snow rendered geological work impracticable. Thus the Green Eiver 

 sheet, which covers an area of over 15,000 square miles, including the 

 greater part of the Uinta mountains, was completed during the single 

 field season of 1871, and for the study of the Uinta mountains during 

 the two seasons of 1869 and 1871 less than three months could be given 

 to actual field work, no small part of which the geologist in charge of the 

 party had to devote to tasks not strictly geological. 



The general system of work was to construct in our minds, from field 

 observations, a tentative set of geological divisions, based primarily on 

 lithologic distinctions, and, from each successive peak visited, to work 

 out the structure of the surrounding country as-indicated by the lines of 

 outcrop exposed. As we had no maps, we used only breast-pocket note- 

 books in which to record our observations ; hence the ideas we formed as 

 to the geological structure of the country visited could not be fully put 

 on paper until the topographer's notes for the whole area surveyed had 

 been platted and engraved, and our tentative geological columns modified 

 or confirmed by the determination of our fossil collections by specialists. 

 Owing to a peculiar combination of circumstances, over two years had 

 elapsed after the final completion of our, seven years of field work before 

 all this was accomplished. 



