540 RESULTS OF THE LABORS 
by the moon. These points were connected by a chain 
and compass survey, accompanied by a line of levels, as 
far as San Antonio. From El Paso the survey was 
continued to the Initial Point of the southern boundary 
of New Mexico on the Rio Grande, making altogether a 
distance of between nine hundred and a thousand 
miles surveyed. 
At nearly all the astronomical stations on this line, 
upwards of fifty in number, observations were made 
by a Fox dip circle for magnetic inclination, declina- 
tion, and intensity. 
An accurate meteorological register was kept 
through the whole line of march. An interesting com- 
parison of the aneroid and ordinary barometer was 
made, extending over elevations varying from the level 
of the sea to an altitude of six thousand feet. A com- 
plete set of barometrical and aneroid observations were 
taken for the construction of a profile, which shows 
the contour of the whole country from San Antonio 
to San Eleazario, on the Rio Grande, exhibiting not 
only the most prominent points, but likewise the ele- . 
vations and depressions in each day’s march. 
The astronomical and magnetic observations were 
made by Lieutenant A. W. Whipple, of the corps of 
topographical engineers, acting chief astronomer in 
- charge of the party, and under whose direction the 
whole work was carried on. 
The survey was performed by John Bull, Esq., frst 
assistant surveyor. 
The map of this survey was plotted on a scale of 
one inch to the mile, and the topography accurately 
laid down by M. Von Hippel. 
