THE TRANSCONTINENTAL ARC. 
213 
which shows an error less than 1 o oVo 'i r part. This line is 
shorter on Bessel’s spheroid than on Clarke’s by 2,000 feet. 
Our uncertainty of 100 feet can therefore not affect the de¬ 
cision as to the proper figure to be adopted for the United 
States. 
A quarter of a century of hard work, sometimes under the 
most adverse circumstances, and an expense of half a million 
dollars is the price paid for the above result. In considering 
this outlay of money we must bear in mind that the occu¬ 
pation of one of the mountain stations alone cost $10,000, 
and required an entire season for its completion. Of the 
nine bases that have been measured on the arc, the most ex¬ 
pensive one was the Yolo, 11 miles long, and it cost in round 
numbers $10,000. The two measures of the Salina base, with 
a length of four miles, cost $2,610. The longest line observed 
was from Uncompahgre, with an elevation of 14,300 feet, to 
Mount Ellen, 11,300 feet high, giving the unprecedented 
single sight through a distance of 183 miles (294,104.05 
meters). Work of this magnitude has never been attempted 
by any nation hitherto. The nearest approach to it is by the 
French and Spaniards, who, in 1879, threw a quadrilateral 
across the Mediterranean from Spain to Algiers, but their 
highest station—the highest mountain in Spain—falls 3,000 
feet short of Uncompahgre, and their longest diagonal is 15 
miles shorter than our own. It is quite true that the English 
in India have seen the summits of the Himalayas at a dis¬ 
tance of over 200 miles, and have determined their direction, 
but these peaks have never been occupied and form no inte¬ 
gral part of their triangulation; so that the United States can 
boast of the longest line, the highest station, and the greatest 
continuous chain of triangles. Unlike some of the projects 
where Americans strive to attain the “ biggest on earth ” idea, 
the transcontinental arc can safely challenge comparison in 
any of its features with the best examples of similar work. 
The accuracy of the result and economy of execution are 
only surpassed by the difficulties of its details and the magni¬ 
tude of its conception. There are more than twenty lines 
30—Bull. Phil. Soc., Wash., "Vol. 13. 
