APPENDIX A. 
REMARKS ON METEOROLOGY AND BAROMETRIC RESULTS, WITH 
METEOROLOGIC PLATES. 
BY ALBERT H. CAMPBELL, A. M. 
CIVIL ENGINEER TO THE EXPEDITION. 
Washington, January 1, 1857. 
Sir : I herewith transmit the results of a cursory discussion of the barometric observations 
taken during the progress of your surveys and explorations to determine the practicability of a 
railroad from the Mississippi river to the Pacific ocean, both in California, from the Bay of 
San Francisco to Los Angeles, and near the 32d parallel of north latitude. 
Respectfully, your obedient servant, 
ALBERT H. CAMPBELL, 
Civil Engineer and Surveyor. 
Lieut. John G. Parke, Corps U. S. Top. Engineers, 
In charge of Pacific Railroad Explorations, dec., dec., dec. 
METEOROLOGICAL. 
DATA FOR THE PROFILES. 
The corrections for the temperature of the mercury were obtained from the tables of the 
Smithsonian Institution, prepared by Professor Guyot. 
The corrections for constant error were obtained by mutual comparisons among all the baro¬ 
meters at almost every camp between the Pueblo de San Jose and the city of Los Angeles. 
At the latter place was obtained barometer No. 790, (Green’s cistern,) which was left there by 
Captain A. W. Whipple, United States Topographical Engineers, after the completion of his 
explorations near the 35th parallel, and by long comparisons with it and those of our own at 
San Bernardino and Jarupa, a chain of connexion through all the work in California, and a 
favorable reference to Green’s standard at New York, was secured, No. 790 having differed hut 
.001 from its former reading, after an interval of two years and five months. All the obser¬ 
vations were, therefore, referred directly to the standard. From a careful discussion of these 
comparisons, it appears there is still a small but appreciable error, the source of which it is 
