LETTER TO CAPTAIN HUMPHREYS, TOPOGRAPHICAL ENGINEERS. 



Smitiisoxian Institution, Washington, Jilarch 1, 1850. 

 Sir : Daring the first organization of the parties for tlie survey of a railroad route to tlio 

 Pacific, application was made to the Smithsonian Institution, by the officers in charge, for in- 

 structions and suggestions in reference to the investigation of the Natural History of tlicir 

 respective lines. These were cheerfully furnished, as in accordance with the objects of an 

 establishment intended for the increase and diiiusion of knowledge. The specimens in Zoology, 

 as collected, were transmitted from time to time to the Institution, and properly preserved 

 until the return of the parties. A series of special reports was prepared by the naturalists of 

 the expeditions ; but as these were necessarily disconnected and incomplete, it was deemed 

 advisable to furnish a general systematic report upon the collections as a whole ; and this being 

 sanctioned by the War Department, the materials were entrusted to competent individuals for 

 this purpose, the necessary drawings being made by a skilful artist within the walls of the 

 Institution. 



The first part of the general report having been already furnished, I now transmit the 

 remainder, with the hope that its execution will be satisfactory to the Department. 

 Very respectfully, your obedient servant, 



JOSEPH HENRY, 

 Secretary Smithsonian Institution. 

 Captain A. A. HuMPiiREYd, Topographical Engineers, 



In charge of Office of Explorations and Surveys, War Department. 



