APPENDIX A. 
1, REMARKS UPON THE ASTRONOMICAL OBSERVATIONS. 
At Camp 1, near the mouth of the Colorado, the longitude was determined with a transit, 
and by observing occultations. Transit observations for longitude were also made at Camp 61, 
near the place where the land explorations from the Colorado were commenced. The longi- 
tudes of the other positions were determined by taking a mean of the results obtained from 
three chronometers. The chronometers were new, and furnished by Messrs. Bond & Sons, of 
Boston. They were carried, during the river survey, upon the steamboat, and, during the 
land explorations, by hand. The results of each day accorded very closely with the results of 
the compass survey. All the observations for latitude were made with a sextant. 
The observations were computed under the direction of Prof. G. P. Bond, of the Cam- 
bridge Observatory. The following communication was received from him in regard to the 
computations and the values of the results : 
CAMBRIDGE OBSERVATORY, January 14, 1859. 
Sir: In reducing the latitude observations of the survey of the Colorado, the results of 
which have been already communicated, I have used, in the first instance, approximate errors 
of the chronometer deduced from your own computations made in the field. The néw latitudes 
were then used to compute the hour angles of the time stars, giving more exact chronometer 
errors, with which the latitudes were again corrected, and lastly, the hour angles also, to 
accord with the latitudes as finally adopted. 
The tables of the Berliner Jahrbuch have been used, in addition to those of the Nautical 
Almanac, as a security against mistakes. Corrections for the barometer and thermometer have 
been applied to the refractions. 3 , . 
On the dates when transits were obtained, the latter have been used in preference to the 
sextant observations. * * Among the observations of time stars, whenever a difference 
exceeding 5s. between results by east and west stars has been found to exist, the work has 
been revised, and the single observed altitudes compared together to detect errors in the 
original record. In this way the corrections made in the note-books have been ascertained. 
Considering the disadvantages under which such observations are made, I think zou have 
reason to be gratified that so few discrepancies remain unaccounted for. 
The transit observations at Camp 1, from December 10 to 28, afford data for an accurate 
rating of the chronometers. Corresponding observations were obtained at Cambridge for each 
of your four moon culminations, two at Camp 1 and two at Camp 61, (in Sitgreaves’s Pass,) 
and also for the occultation of the Pleiades, December 27. These have afforded the following 
results for longitudes : 
