FORM AND CONSTITUTION OF EARTH—STEWART. 167 
they prepared eight wooden rods each five toises in length and termi- 
nating in metal studs, which were used in measuring the base. 
This work was begun on December 21, the party having been 
divided into two, each taking four rods and working independently, * 
the rods probably being laid upon the snow with their ends in contact. 
The difference between the measurements was only 4 inches in a 
length of 7,406.86 toises. 
It only remained now to compute the length of the meridian are 
contained between the parallels of the two terminal stations. This 
was found to be 55,023.5 toises. 
Seeing that the resulting length of a degree would be far in excess 
of that in the latitude of Paris, they submitted their work to a rigid 
examination. An investigation of the division errors of the are of 
their sector was made, and the amplitude of their are redetermined 
increasing it to 57’ 30.42’’.. Observations for azimuth were made at 
Tornea, and it was found that the resulting azimuth differed by 34’ 
from the value computed through the triangulation from the observa- 
tions at Kittis; but this would have but a trifling effect upon the 
length of the meridian are. 
Their final value for the length of a degree was 57,437.9 toises. 
Meanwhile the Peruvian party had selected as the scene of their 
operations the valley in which Quito is situated, and which lies be- 
tween the double range of mountains into which the Andes are there 
divided. By placing the stations of their triangulation alternately 
on opposite sides of the valley, they were able to form extremely well- 
conditioned triangles, though the labor involved in occupying the 
stations may be inferred from the fact that seven of them were sit- 
uated at heights exceeding 14,000 feet. A base line was measured 
near each extremity of their chain of triangles, the northern base 
being near Quito, and having a length of 7.6 miles, and the southern 
base a length of 6.4 miles. In their astronomical work they observed 
the absolute zenith distances of stars, thus finding the latitudes of 
their terminal stations, and not merely their difference of latitude. 
The same stars, however, were observed at the two stations, so that 
their difference of latitude was unaffected by errors in the star places. 
The amplitude of their are was 3° 07’ 01’’, and its length 176,945 
toises, thus giving 56,753 toises as the length of 1° at the Equator, 
which was about 685 toises shorter than the value found in Lapland, 
the length of a degree in France being intermediate between these. 
Thus was 1t demonstrated finally that the form of the earth is that 
of an oblate spheroid, and subsequent arc measurements have only 
served to confirm this conclusion. 
The problem that now presented itself was the determination with 
all possible precision of the exact dimensions of the terrestrial spheroid. 
Geodetic surveys were soon in progress in every civilized country. 
