the mean Denjiiy of the Earth. 7 1 1 
The other meafures that were taken for determining 
the fedlions will be delivered afterwards, when the re- 
fults or computed altitudes have been obtained, in order 
to be placed oppofite to their correfpondent angles. 
Having now obtained, to a great degree of accuracy, 
the meafured lengths of two lines which were to ferve 
as bafes for all the future calculations, the next confide- 
ration was how to make the propereft ufe of them. 
Every other line or diftance, drawn or conceived to be 
drawn, muft be calculated from them by the help of the 
angles obferved either at their extremities, or at all the 
other points and ftations in the furvey and plan. As thefe 
two bafes are fituated in the low parts of the country, 
from whence but a very few of the other principal na- 
tions are vifible, one method evidently is to compute im- 
mediately from thefe bafes fuch of the great lines in the 
furvey whofe extremities are vifible from them; and 
then from thefe calculated lines to compute others next 
to them, and fo on quite around and within the whole 
figure. In this manner feveral values of each line will 
arife, both from the double computations by the two 
meafured bafes, and from the various fets of triangles 
which can be formed from the very numerous ho- 
rizontal angles which were obferved at the feveral 
ftations. But in this mode of computation, after 
6 
great 
