No. 2. 
REPORT 
UPON THE 
PROGRESS OF THE PACIFIC RAILROAD EXPLORATIONS AND SURVEYS. 
NOVEMBER, 1855. 
BY CAPTAIN A. A. HUMPHREYS, CORPS OP TOPOGRAPHICAL ENGINEERS. 
War Department, 
Office Pacific Railroad Explorations and Surveys , 
Washington , November 29, 1855. 
Sir: Since my report to you of February 5, 1855, the general map of the territories of the 
United States lying between the Mississippi river and the Pacific ocean has been completed as 
far as the materials collected admit, and is in the hands of the engraver. The labors of the 
parties organized for continuing explorations will afford data for still further additions. 
Many of the maps, drawings, and scientific papers intended to form part of the reports 
submitted to you by the first exploring parties, soon after their return from the field, could 
only he prepared after an elaborate use of the materials collected. In some instances hastily 
prepared drawings and preliminary reports were temporarily substituted for the more elaborate 
results, which are now, for the most part, complete. 
The results of the investigations in the various branches of physical science in connexion 
with the expeditions are of great practical value, and full of scientific interest. The geological 
and meteorological reports are eminently so in many points of view. By the former it will be 
perceived that the sources and quality of building materials at various remote and important 
localities have been determined, and rich deposits of gypsum and limestone have been marked 
out. On the routes of the 35th and the 32d parallels, the structure of desert areas has been 
minutely studied with special reference to the practicability of obtaining water by wells or by 
boring, and generally with the most satisfactory results. From the report of Mr. W. P. 
Blake, the geologist of the expedition in charge of Lieutenant R. S. Williamson, it appears 
that the structure of the Colorado desert, between Fort Yuma and the Coast mountains is very 
favorable to the success of artesian borings, and it is considered probable that an abundant 
supply of water would be obtained by boring to a moderate depth. Such a result would be 
of extreme importance, not only by facilitating communication between Fort Yuma and the 
coast for government trains, but as a relief to the emigrant parties which are constantly cross¬ 
ing to California through New Mexico and Sonora. The general nature and composition of 
the soils and sub-soils over tbe region explored has been determined, and analyses of the most 
