Mr. Dalby’s Deduction, tzc. 2^7 
p. 232. mutt be nearly true, whatever may be the real figure 
of the earth. But, it may be faid, that the arc between the 
meridians of Botley Hill and Goudhurft (i/j) is too fhort to 
infer from obfervation the value of the arc between the meri- 
dians of Greenwich and Dunkirk (amounting to near a degree 
and a half), fufficiently accurate for finding the longitude to 
great precifion ; becaufe it has been remarked in the Appendix 
to the fame Volume, that an error of 1", in either of the 
horizontal angles at the above ftations, would caufe a variation 
of near 6 // of a degree in the longitude of Dunkirk or Paris. 
M. Bouguer’s fpheroid agreeing nearly with the meridional 
meafurements, it was adopted for the purpofes of latitude. But 
the degree perpendicular to the meridian in latitude 51 0 6 7 53" 
is found to be 61248 fathoms (Vol. LXXX. p. 215.) which 
falls fhort of M. t Bouguer’s degree about 22 fathoms; there- 
fore, fuppofing the directions of the meridians to have been 
very accurately determined, the earth cannot be this fpheroid, 
notwithftanding the ingenious hypothefis refpeCting the curve 
of the meridian. But it is alfo well known, that the mea- 
fured degrees of latitude in different places are inconfiflent with 
an elliptical meridian : for, fuppofe an ellipfoid to be deter- 
mined with the degrees found at the equator and polar circle,, 
the computed degrees in middle latitudes will be much longer 
than the meafured ones, as it is well known ; and the whole 
meridional arc between Greenwich and Paris will, on fuch an 
ellipfoid, exceed the meafured arc by a quantity anfwering to 
about 2i ;/ of latitude. It is evident, however, that if we fuppofe 
fmall errors to have taken place in determining the celeftial arcs, 
or differences of latitude in fome of the operations (for there 
is little doubt but the terreftrial menfurations in general have 
been 
