LETTER TO THE SECRETARY OF WAR. 
Washington, December 31, 1854. 
Sir : I have the honor herewith to submit to you the following report of a reconnaissance 
and surveys on partial routes in California, connected with surveys for ascertaining the most 
practicable railroad route from the Mississippi river to the Pacific ocean. 
I present in connexion with this report a geological report by Mr. W. P. Blake, geologist 
and mineralogist of the expedition, illustrated by maps, sections, and views. 
Dr. A. L. Heermann, the physician and naturalist of the expedition, made a large natural 
history collection ; and among the fish, reptiles, and plants are found many species hitherto 
unknown. The collection of California birds is a very fine one, it containing more than one 
hundred and twenty species. 
These collections in different departments of natural history have been examined, and the 
descriptions, accompanied by figures, will appear in a separate volume. Dr. Heermann will 
present a report on the birds ; Professor Spencer F. Baird, of the Smithsonian Institution, on the 
mammalia; Dr. E. Hallowell on the reptiles; and Charles Girard on the fish. The plants will 
be described by Dr. Hilgard and Mr. Durand, of Philadelphia. 
The sketches which accompany this report were made by Charles Koppel, assistant civil 
engineer, and they will serve as aids in forming a correct idea of the nature of the country. 
I have to thank my associates in this survey for the great interest they took in the expe¬ 
dition, and the cheerful and thorough manner in which the work was performed. Lieutenant 
Stoneman, commanding the escort, rendered me every assistance in his power. Lieutenant 
Parke was of very great assistance to me, taking charge of a party whenever the main party 
was divided, which was generally the case. Mr. Smith proved himself to be a very competent 
civil engineer. The reports of Dr. Heermann and Mr. Blake at once show the nature of their 
labors, and the manner in which they were performed. In fact, every member of the party 
was unceasing in his endeavors to advance the objects of the expedition. 
I have the honor to be, very respectfully, your obedient servant, 
R. S. WILLIAMSON, 
Lieutenant U. S. Top. Engineers. 
Hon, Jefferson Davis, 
Secretary of War. 
