Don J. Rodriguez's Observations on the 
336 
From what has been above stated, it seems almost beyond a 
doubt that it is to errors in the observations of latitude, that the 
appearance of progressive augmentation of degrees towards the 
equator, as represented by Lieut. Col. Mudge in his paper, are 
to be ascribed, and that it is especially at the intermediate sta- 
tion at Arbury Hill, that the observations of the stars are erro- 
neous nearly 5 seconds, notwithstanding the goodness of the 
instruments, and the skill and care of the observer. But, be- 
fore I insist farther on this head, I will answer one objection 
that may be made to the principles of the method that I have 
pursued in this Memoir. 
Those astronomers, who have hitherto undertaken the mea- 
surement of degrees of the meridian, have deduced their 
measures by simply dividing the linear extent by the number 
of degrees and minutes found by observation of the fixed stars 
taken at the two extremities of the arc. This is indeed the 
most simple that can be adopted ; and it has the advantage of 
being independent of the elliptic figure of the earth, especially 
in arcs of small extent. The elements dependent on this 
figure, are too uncertain to be employed in calculating the 
angular intervals in the short distances between successive 
stations, even as a means of verification, without risk of com- 
mitting greater errors than those to which astronomical ob- 
servations can be liable. Accordingly one cannot safely make 
any use of it in cases where great accuracy is required. 
I must admit the justness of this objection, and must there- 
fore shew the extent to which it really applies to the present 
subject* 
In the first place, I may suppose, that in consequence of 
some fault in the instrument, with respect to vertical position, 
