[ 3i ] 
of the earth, that of X to i : We fhall have, by 
the general law, the Moon’s fall in W, equal to 
jp 
^ ; but the fame fall is equal to VxDxXj whence 
F 3 / p — 
X 3 — yyjy and X — V is the diftance fought,. 
in femidiameters of the equator. 
Nowafimple pendulum which beats feconds, mea- 
furing, at London, 39.1 26 inches ; if the ufual al- 
lowance is made for the weight of the air, and for 
the Newtonian figure of the Earth *, the weight 
taken off by the centrifugal force being like- 
wife reftored, a fecond-pendulum at the equator would 
be 39.154 inches long. And, by Huygens’ rule,, 
half this length is to the initial fall in one jecond, in 
the duplicate ratio of the diameter of a circle to it’s 
circumference: that fall therefore, at the equator, 
and in vacuo, is 16.ro 1 85 feet y the logarithm of 
which number is 1.2068645 — l°g- F. 
The toifss in a degree of the equator, or, which 
is the fame, in a degree of the meridian at lat. 544, 
being nearly 57200, the logarithm of the number 
of feet Englifh in the femidiameter of the equator. 
that is log. D will be nearly — 
And the log. verfed fine of the Moon’s 
arc in 1" , being — — — 
7.3211900,, 
2.5492882, 
Their Sum — — — — .—.5.8704-82 
taken from log. F, leaves + 5.3363863, a third of 
which is 1.7787954, the logarithm of X — 
60.08906 femidiameters of the equator. 
* See die Eflay quoted above. 
And ! 
