The character and extent of Frémont's astronomical and other physical observations on this long, arduous, and dangerous journey constituted the great value of his exploring work. In few instances did it fall to Frémont's lot to first explore any section of the country, but it was his good fortune, as it was his intent, to first contribute systematic, extended, and reliable data as to climate, elevation, physical conditions, and geographical positions. The hypsometrical work begun by Frémont culminated, indeed, in the unparalleled collation of elevations by Gannett; his climatic observations have been perfected by the Signal Corps; his astronomical and geological data have been overwhelmed by the magnificent collections and field work of the United States Coast and Geodetic and Geological Surveys; but it is to be noted that Frémont's observations, which he gave in detail, were so honest and good that they have withstood successfully the test of hostile examination. Frémont's scientific spirit was strikingly exemplified in this terrible mid-winter journey through the mountains of Nevada, when observations for time, latitude, elevation, or temperature were daily and regularly made despite snow, extreme cold, and physical weakness from semi-starvation. On the recommendation of General Winfield Scott, in a special report, the unprecedented honor of double brevets--of first lieutenant and captain--was conferred on Frémont for gallant and highly meritorious services in connection with these two expeditions. Frémont's third expedition consisted of sixty men. They left Bent's Fort, on the Arkansas, August 16, 1845. Its object, as far as exploration was concerned, included a survey of the head-waters of the Arkansas, Rio Grande, and Rio Colorado, the basin of the Great Salt Lake and the practicable passes of the Cascade and southern Sierra Nevada. It was during this journey that Frémont quite fully surveyed the southern shores of Salt Lake. The water was then at an unusually low--possibly at its lowest known--level, and having been informed by the Indians that it was fordable to Antelope Island, Frémont with Kit Carson rode to the island, the water nowhere reaching above the saddle-girths of their horses. Dividing his party Frémont crossed the Utah desert between the thirty-eighth and thirty-ninth parallels, while his subordinate, Walker, explored the valley and sink of the Humboldt. Rendezvousing at Lake Walker and again separating, Frémont reached Sutter's Fort through the American River route, while Walker and the main party crossed the Sierras into the extreme southern part of the San Joaquin Valley, opposite Tulare Lake. Of the survey and explorations made by the expedition it may be briefly said that they added very greatly to a knowledge of Upper California, and resulted in the publication in 1848 of the most accurate map of that region extant.