CONCLUDING REMARKS. 43 
60 observations for time, and 83 for latitude. At the Depot camps we had opportunities of 
multiplying observations, so as to test thoroughly our chronometers, and the results were very 
satisfactory, as far as the Mohave river. The chronometers were enclosed in leather cases, and 
these were placed in a valise made for the purpose, and were transported in the spring-wagon, 
except where the road was rough, in which case they were carried by hand. Upon leaving the 
Mohave Depot camp, to follow down the river, I was obliged to pack them on a mule, and 
though the mule was led, and every precaution taken, we found that they changed their rates, 
and the longitudes obtained by calculation were not reliable. 
A party properly equipped for the field should be provided with at least three chronometers. 
Having but two, if one suddenly changes its rate there are no means of ascertaining which one 
it is without a series of observations, which would cause delay and might much embarrass the 
operations of the party. It is my opinion that little reliance can be placed upon chronometers 
which are transported on pack-mules. 
The barometers which were used in the survey were constructed by James Green, of New 
York. Two of these were syphon barometers and two cistern, of the pattern used by the 
United States Medical Department. An aneroid barometer was also carried. 
As the observations for the profiles of the Tejon Pass and the Cañada de las Uvas were made 
by both barometer and spirit-level, I have been enabled to compare the results by each, and 
have presented them in the profiles of these passes attached to the maps. These profiles show 
that, by the ordinary methods of computation, the results from the barometer and level agree 
very closely, the difference not being sufficiently great to affect the questions of grade and 
practicability. But it is believed that, from the data obtained during the survey, an improved 
method of computation may be deduced, and the deviation of the barometric from the true 
altitude very much reduced. If this should prove to be the case, it will add greatly to the use- 
fulness of the barometer as a surveying instrument. 
