210 
PRESTON. 
whose perseverance is due the successful termination of the 
triangulation from the Sierra Nevada to the Mississippi val¬ 
ley, and the latter is Mr. C. A. Schott, to whose untiring in¬ 
dustry we owe the discussion of the results. 
From Cape May light-house, in New Jersey, to Point Arena 
light, in California, the distance is 2,625.6 miles. These points 
are within a very few miles on the same parallel of latitude, 
which, by the way, is that particular parallel on which the 
center of population of the United States seems to be tracing 
its course. 
In this grand network there are 266 primary stations, in¬ 
volving the measurement of many thousand angles; and if 
we consider the subsidiary points determined, it can truth¬ 
fully be said that the number of localities precisely estab¬ 
lished in latitude and longitude by this great chain exceeds 
that of the stars visible to the naked eye. 
There are several unique features. The arc consists ex¬ 
clusively of quadrilaterals or figures equally as strong. No 
single triangle has ever been permitted to carry the work 
forward, and where the diagonals of quadrilaterals were in¬ 
convenient or impracticable, pentagons or hexagons were 
substituted. Four stations are above 14,000 feet elevation 
and twenty are beyond 10,000 feet. Let any one imagine 
the difficulties of making observations at an elevation of 2f 
miles. Consider that at this altitude the barometer stands 
at 18J inches; that there is perpetual ice and snow; that 
water boils at 189 degrees, and that, there being only about 
one-half the usual amount of air, every one is more or less 
affected by mountain sickness. 
At one time it fell to my lot to occupy a station in the 
tropics at 14,000 feet, and I can certify that the experience is 
not altogether pleasant. Snow and ice in July, and in the 
tropics, and on a party coming but a few hours previous 
from a torrid atmosphere, where the system is debilitated by 
long months of sunshine, is to most persons the severest test 
of endurance. 
On the transcontinental arc 9 bases have been measured. 
