( 205 ) 
« one {hall find the Length of the Chords H I r I > , 
66 comprehended between each Degree. 
Monf. CaJJin'h in the Memoirs for the Year 1718, re- 
peats the fame Demonftration ; except that, before it, ne 
fhews, that if feveral Points be taken upon a Terrettrial 
Meridian, on the Surface of an Elliptick Earth, asG, o, 
I,K,*in fuch Manner, that their refpedive Zeniths Z, L, 
M, N, are diflant from one another, an equal Number 
of Degrees meafur’d in a Celeftial Meridian. The Lines 
Z G, L H, M I, N K (which are perpendicular to the 
Ellipfe) being produced, ' will meet in the Points O, K, 
and S, making equal Angles, but as thofe angular Points 
are not equally diftant from the Curve of the Elliple, 
that Elliptic Arc muft be the longed w-hofe angular 
Point is farthefl off. Now, by the former Demonitra' 
tion, it appears, that thofe Arcs, which are taken neareft 
to the leifer Axis, will have their angular Points farther 
remov’d, ^ 
IfMonf. CaJJIni'i Meafures ofTerreftrial Degrees, 
decreafino- from the iEquator towards the Pole, were 
erounded’on Obfervations liable to no Error, he wou’d 
have fully prov’d his Figure of the Earth. But nnce 
thofe Meafures (however accurately taken) are not built 
upon a mathematical Certainty, his Premiles may be 
call’d in Queftion, and 'his* Conclufion, tho mathema- 
tically drawn from thefe Premifes, is only 
Now therefore, if I can fhew from undoubted x/jss- 
nomena,that his Conclufion will lead to an Abfurdity, 
his Meafures muft be falfe ^ becaufe his Reafomng 
from them is This I (hall, endeavour to do firft, , 
which will difprove his Figure of the Earth ; and after- 
wards endeavour to point out fome of the Errors which 
* Fig. II, :. 
