204 Gen, Roy’s Account of a 
1773. I am aware that experiments with the pendulum have 
not yet been made with that accuracy that the delicacy of their 
nature 
With the accelerations, indicated in that page as arifing from different experi- 
ments, or depending on the fyftems of different philosophers, the length of the 
Spitzbergen pendulum, and confequently the ratios, fhould have flood as in the 
annexed table, with which it will be perceived they differ very confiderably. Sir 
Isaac Newton’s ratio is placed lad, as probably differing mod from the truth. 
Experiments. 
Ac 
From the 
equator to 
London. 
celeration 
From Lon 
don to 
Spitzberg. 
Total. 
Length 
of the 
Spitzberg. 
pendulum. 
Ratio of the 
lemi diameters 
of the earth. 
Said to be, but erro- 
II 
J II 
In. 
neoufly, SuLNewton’s 
■> 
r 
+ 66.9 
222.9 
39.1964 
194-5 to 193-5 
Mr. Campbell’s 
+ 76.6 
232.6 
3 9 . 2°52 
186.5 to 185.5 
M. Maupertuis’s 
+ 86.5 
242.5 
39.2141 
178.8 to 177.8 
LdMuLGRAVE’scorreft. 
+68.5 
224.5 
39- 1 97 ^ 
1 93. 1 to 192. 1 
Sir Isaac Newton’s 
J 
s. 
+ 3 2 -4 
1 SB. 4 
39.1652 
230. to 229. 
In this manner the lengths of the pendulum having been found for all the 
latitudes where the bed or mod confident experiments had been made on its 
acceleration, and thefe lengths having been fucceffively compared with each other 
from Spitzbergen to the equator, 1 19 refults in the whole were produced. But as 
this number comprehended the comparifons of thofe at the Cape of Good Hope and 
the Ifle of France, both in fouth latitude, thefe being thrown out, as well as the 
Porto Bello pendulum, and fotne few others more irregular than the red, there 
remained at lad 75 refults, the arithmetical mean of which gave the ratio 
\ 
179.047 to 178.047, as mentioned in the text. 
In cafe Mr. Cumming’s machine fhould at any time hereafter be employed in 
the fame fort of experiments, it may be proper to obferve, that the diameter of 
the brafs ball is 3.906 inches, and its weight 63726 Troy grains. The weight 
of its bulk of mercury is 106980 Troy grains. Hence the weight of mercury 
is to the weight of this ball of brafs, in air of the heat of 62° of Fahrenheit, 
as 1.678752 to I ; and the weight of this brafs to air is as 7673 to 1. The 
experiments for this purpofe, in which Dr. George Fordyce adided, were 
made in the houfe of Mr, Alchorne, at his Majedy’s Mint in the Tower, on 
the 
