C SIS ] 
tained between the Weftern earn and the pole placed on 
theoppolite hill in a line with the Eaft earn and Southern 
obfervatory, which is the fame with the angle contained 
between the Weftern earn and Southern obfervatory. 
Thus were the three angles found of the triangle made 
by the Southern obfervatory and two earns. In the like 
manner were the angles of the triangle made by the 
Northern obfervatory and two earns found afterwards. 
And, as a proof that the angles of the two triangles were 
rightly determined, their fum in the firft cafe differed 
from 1 8o° by little more than two minutes; and in the 
fecond cafe by only half a minute. 
Notwithftanding the advantages which attended this 
method of finding the diftance of the two ftations of the 
obfervatory, I thought it proper to make ufe alfo of the 
other method of doing the fame thing by a fmall num- 
ber of triangles carried diredUy acrofs the hill, thinking 
it expedient,, in a matter of fuch confequence, to rely on 
no fingle operation;, but, as far as pollible, to confirm 
every deduction by another found in an independent 
manner. I had caufed two poles to be fet as far up the 
hill of Schehallien as they could be* placed ; one as near 
the Weftern, and the other the Eaftern earn as they 
could be, fo as to be vifible from the Southern ftation of 
the obfervatory : alfo two others in like manner vifible 
from the North obfervatory ; one of which was very near 
the Eaft carn^ and the other only 269 feet diftant from 
the Wefternmoft of the two poles vifible from the South 
obfervatory ; fo narrow was the ridge of the hill in that 
part, although it grew wider both to the Weft and 
Eaft, 
