[ 3 2 7 ] 
at the fame time touching the other cheek, the moveable cheek was fcrewed fad ; and 
thus the toile was exactly contained between the cheeks without any (hake, and it is 
evident that the interval between the cheeks was exactly equal to the length of the toife. 
In order to meafure this interval, the toife being taken away, very tine lines were 
drawn with a fine point, at the end of each cheek, upon the brafs pins which were in 
the fame plain with the board : then the cheeks were removed, and fine points made 
at the outer extremity of each line, and this diftance being taken between the fine 
points of a beam compafs, was transferred to the fcale, and thus the length of the toife 
was found in meafures of the fcale, which is divided by a vernier to thoufandths of an 
inch. The toifes and brafs fcale had been left together in the fame room, and near 
one another all the night before, and till the very time of making the comparifon of the 
toifes with the fcale, in order to be fure that they were all afFedted with the fame de- 
gree of heat. 
As it may be agreeable to the reader to fee the refult of the principal meafures of 
degrees of latitude, that have been taken with later inffruments and proper accuracy, 
brought together into one view, the following table is here added. 
Length ot a 
degree in 
Paris toifes. 
Mean 
latitude. 
Names of the obfervers. 
Years m wlncn 
the degrees were 
meafured. 
57422 
20' N 
M. de Maupertuis, &c 
1736 and 1737 
57°7 4 
49 23 N 
M. de Maupertuis, &c. and M. Caflini 
1739 and 1740 
1768 
57091 
47 4 ° N 
P. Liefganig 
57028 
45 0 N 
M. Caflini 
1739 and 1740 
57069 
44 44 N 
P. Beccaria 
1768 
56979 
43 0 N 
Le Pere Bofcowich and Le Maire 
* 75 2 
56888 
39 12 N 
MefT. Mafon and Dixon 
1764 to 1768 
5 6 750 
57037 
0 0 
33 *8 S 
M. Bouguer and M. de la Condamine 
Abbe de La Csiille .... 
1736 to 1743 
1752 
If this degree be compared with the degree meafured at the equator 56750 toifes, 
in the hypothefis of the earth’s being an oblate fpheroid, the ratio of the equatorial to 
the polar diameter will come out as 494 to 493. But, if it be compared with the 
degree meafured in Laplandy, in the latitude 66° 20', — 57419 toifes (I have fubtradted 
3 toifes, becaufe the toife ufed in Laplandy was T-th or J.-th of a line lefs than the 
toife ufed in Peru, fee M. De la Lande’s Aftronomy, Article 2107), the ratio of the 
diameters will be as 142 to 141. The great difference of thefe refults is a frefh proof 
of what has appeared from the comparifon of the meafures of the feveral degrees taken 
before, either that the figures of the meridians are not accurately elliptical, or that the 
inequalities of the Earth’s furface have a ccnfiderable effedt in deflecting the plumb- 
line from its true fituation, or both. I, had indeed fuppofed that any defledtions of the 
plumb-line were not to be feared with refpedt to this particular meafure of a degree, at 
the end of my Introduction to Meffteurs Mafon and Dixon’s account of the fame, by' 
arguing 
