INTRODUCTORY LETTER. 



United States Engineer Office, 

 Geographical Explorations and Surveys 



West of the One hundredth Meridian, 



Washington, D. C, February 1, 1875. 



Sir : The following brief statement of the operations of the zoological 

 work of the expedition for the years 1871, 1872, 1873, and 1874, based upon 

 the collections made by different members of the party in this period, and 

 embracing an epitomized account of certain portions of the different Terri- 

 tories visited by the collectors, may prove of interest, besides assisting in 

 giving an idea of the features of the several regions as regards geographical 

 distribution. 



Although the active operations of the expedition were inaugurated in 

 1869, owing to various circumstances it was not until 1871 that facilities 

 adequate to a proper prosecution of natural history work, as an item of 

 interest collateral to the special object of the survey, topography, were 

 available. Anticipating at this time that the country through which the 

 expedition must pass, being but little known and seldom visited, would 

 prove a rich field for the study of the naturalist in developing the existence 

 of many forms of animal and vegetable life, rare, if not new, to science, the 

 services of Acting Assistant Surgeon W. J. Hoffman, United States Army, 

 were secured, together with those of Mr. F. Bischoff, a collector of recog- 

 nized skill and enthusiasm, to whom was confided the task of collecting. 



The points of departure in 1871 were: Carlin and Battle Mountain, 

 Nev., on the Central Pacific Bailroad; the point of disbandment, Tucson, 

 Arizona; the area between these places extending about eight degrees in 

 latitude, and longitudinally from the 110th to the 119th degree. 



The several rendezvous were: Belmont, Nev.; Camp Independence, 

 Cal.; Cottonwood Springs, Nev.; Crossing of the Colorado River, Truxton 

 Springs, Prescott, and Camp Apache, Arizona. 



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