the mean Denjity of the Earth. 719 
f.R-f.f> + RS+tang. elev.=log. of the altitude of the point. 
Wherefore having taken, from a table, the fines of p. and 
p, and placed them in the fifth and fixth columns, fub- 
tradt the latter from the former, and write the remain- 
ders in the next or feventh column ; to thefe add the con- 
ftant logarithm of rs, and write the fums in the eighth 
column ; take out then the tangents of the angles in the 
fecond column, and having placed them in the ninth co- 
lumn, add together the adjacent numbers of the eighth 
and ninth columns, placing the fums in the tenth co- 
lumn, which being the logarithms of the altitudes or 
depreffions of the points />, take the correfponding num- 
bers from a table of logarithms, and write them in the : 
eleventh or laff column, for thofe altitudes or depreffions - 
with refpedt to the point s, with the height of the theo- 
dolite included, and which is afterwards allowed for, its 
height being generally about 4} or 4| feet. In the fecond 
column D denotes depreffion and e - elevation; in the laft. 
column d denotes depreffion and a altitude. 
N° 
