Measurement of three Degrees of the Meridian. 327 
Latitude, 
51° 3*' 4" 
51 25 18 
3 1 13 18 
31 ^ 34 
60849 
60864 
60890 
60884 
The singularity of these results excites a suspicion of some 
incorrectness in the observations themselves, or in the method 
of calculating from them. The author has not informed us in 
his Memoir, what were the formulae which he employed in the 
computations of the meridian ; but one sees, by the arrange- 
ment of his materials, that he made use of the method of the 
perpendiculars without regard to the convergence of the me- 
ridians ; and although this method is not rigorously exact, it 
can make but a very few fathoms more in the total arc, and 
will have very little effect on the magnitude of each degree. It 
is therefore a more probable supposition, that, if any errors 
exist, they have occurred in the astronomical observations. But 
it is scarcely possible to determine the amount of the errors, or 
in what part of the arc they may have occurred, excepting by 
direct and rigorous computation of the geodetical measure- 
ment. I have therefore been obliged to have recourse to cal- 
culations, which I have conducted according to the method and 
formulae invented and published by M. Delambre. 
The means generally employed for finding the extent of a 
degree of the meridian, consists in dividing the length of the 
total. arc in fathoms, by the number of degrees and parts of a 
degree deduced from observations of the stars ; but if these 
observations are affected by any error, arising from unsteadi- 
ness of the instrument, from partial attractions, or from any 
other accidental causes, then the degrees of the meridian will 
U u 2 
