BAROMETRIC OBSERVATIONS. 5 
The mean of all the readings, observed and interpolated, as thus corrected by the curve, 
was then found, and the difference taken between it and each of the readings; affecting these 
differences with the sign + when the mean was the greater, and with the sign — when it was 
the less. 
The corrections from this table (corresponding in date and hour to that of the observation to 
be computed) were applied to all observations taken during the period of time covered by the 
table. The observatiors were then ready for computation, for which purpose the tables of 
Prof. Guyot, in the Smithsonian collection of meteorological and physical tables, were used. 
The mean of all the observed temperatures at each station was used in making the computations. 
In order further to correct the results of the observations made at camps upon the Colorado, 
a profile of the river, as determined by the computed altitudes, was plotted, the distances 
from camp to camp being laid off on a scale of five miles to the inch, and the altitudes on a 
scale of 100 feet to the inch. The profile exhibiting considerable irregularities, a mean line 
was drawn to represent the slope of the stream, and the tabulated altitudes of the camps 
increased or diminished by the amount that the corresponding point upon the profile fell below 
or above the mean line. The final results are given in the column of altitudes in Appendix B. 
