( zi8 ) ' ' 
Now if we go back to the Obfervations of the Baro- 
meter, made by the Gentlemen that drew the Meri- 
dian in France , we fhall find, that on the Mountain of 
Rhode z> in the Latitude of 44 0 , 7 1' the Barometer fell 
24 Lines below the Level of that in the Cbfervatory, 
and they allow’d only 274* Toifes to correfpond to that 
Fall ; whereas, according to Dr. Halley s Proportion of 
a Tenth of an Inch for 90 Feet, they fhou’d have taken 
300 Toifes j and tho’ the Hypotenufes A B, and B C, 
* were taken longer than the bare Declivity of the 
Mountain (which wou’d make the Error lefs than the 
79 Toifes I mention’d above) yet if my Proportion be 
made ufe of, viz. of 80 Feet for each Line of Mer- 
cury , that will make the Mountain 320 Toifes, which, 
being higher, will therefore fhew the Bafe to be yet 
fiiorter, and confequently the Error, at that Rate, will 
be greater. 
This Error (and fuch like, if any more were made) 
will encreafe the Meafure of the 44th Degree of Lati- 
tude on the Earth ; and, by obferving what was done 
in the next Degree, we fhall find that that Degree was 
taken too fhort. In the Latitude of 47°, 38', the 
Mountain of Cofte is made 817 Toifes high j whereas 
the 54 Lines of the falling Mercury in the Barometer, 
faid to anfwer to that Height, will give but 705,6 Toi- 
fes (which we will call 705,5) even according to my 
Computation of 80 Feet to a Line, which is the greateft 
Allowance. If we fuppofe this Mountain to rife in an 
Angle of 26°, 33 ', as we did that of Rhode z, the Sides 
of the Mountain, or Hypotenufes A B, and B C, j will 
be each equal to 1 577,5*4 Toifes* and the whole Bafe 
A C, to 2822 Toifes. Now, when the Height of this 
Mountain is call’d 815 Toifes, the Bafe A D, or DC 
