the mean Denfity of the Earth. 721 
Thus then every line in the table contains the folutions 
of the two triangles, the one horizontal and the other 
vertical, ufed in finding the altitude of each point or pole 
in the feilion. The addition of the conftant logarithm of 
the bafe rs to the logarithms in the feventh column, is 
moft eafily performed by writing it on the bottom of a 
little flip of paper, and fo Aiding it down fucceflively 
over each of tliofe numbers, and in that pofition adding 
them together, and placing the fums immediately oppo- 
fite in the next column. 
And in this manner were computed the relative alti- 
tudes of the points in the other vertical fedlions ; except- 
ing two or three cafes, in which the conftant angle formed 
by the feftion and the bafe was a right angle ; and one 
cafe in which the vertical angles were not taken at the 
beginning of the feition line, but at the other end of the 
bafe line where the horizontal angles were alfo obferved. 
It may be neceflary, therefore, to infert and explain an 
example of each of thefe cafes, and the more fo as they 
point out the propereft means of meafuring thefe flec- 
tions fo as to fave moft part of the labour in the compu- 
tation, in which the trouble chiefly confifts. 
Of the cafe of the right angle, the 
firft fedlion is an inftance, where alfo rs 
is the bafe as before, and the angle rs p 
being = 90°. 
Vol. I XVIII. 4U 
••• P 
R 
S 
Poles. 
