904 
LOGARITHMS. 
If fi. or 3° fhould be the firft term of the proportion, 
the logarithm of the fourth term is found by adding to¬ 
gether the logarithms of the fecond and third terms; but 
in thefe cafes, none of the terms mult exceed 3 h. or 3 0 , 
as the Tables go no farther. 
Ex. 3. What is tht fourth proportional to 3 0 , z° 44/ 7", and 
15 3 
" g 
44 
15 
log. 
Fourth prop. 1 S 25 
- o’ 04 oi 
o - 38 oo 
„ - 0'420I 
diftance of the higher ftation from the earth’s centre) to 
C Q, (a third proportional to C /, the diftance of the lower 
ftation from the earth’s centre, and C A, the earth’s femi* 
diameter,) is the logarithm of the ratio of the denfity at 
- B, to the denfity at /, (that is, of the columns of quick- 
filver fuftained in the barometer at B and /,) in the at- 
molpherical fyftem. Therefore, as the difference of the 
tabular logarithms of thefe columns, to the fubtangent of 
the tabular fyftem, fo fhould B/, diminifhed as hath been 
faid, (that is, fo fhould / 3 £,) be to the fubtangent of the 
atmofpherical logarithmic. The utraoft height to which 
we can afcend, above the level of the fea, is fo fmall. 
equal 
