424 Capt. Kater’s experiments for determining the variation 
Report, it appears probable, that if the uncertainty which 
must exist in the allowance for the height above the level of 
the sea be excepted, the error in the number of vibrations of 
the pendulum at any particular station, does not amount to so 
much as one tenth of a vibration, which is nearly equivalent 
to 4 q'o’qo o part of the length of the seconds pendulum. To 
this degree of accuracy consequently may gravitation be 
determined by the apparatus I have employed ; and in passing 
through a country composed of materials of various densities, 
the pendulum may be expected to indicate such variation with 
very considerable precision. 
The diminution of gravity from the Pole to the Equator is 
derived from the decrease which is observed to take place 
between any two given latitudes ; consequently if no irregular 
attraction occurred, the results, computed from different por- 
tions of the meridian, should be the same. But it may be seen 
in the preceding table, that the number expressing the diminu- 
tion of gravity, from the observations at Unst and Portsoy, is 
less than that deduced from the arc between Unst and Leith, 
and that this number goes on increasing to Clifton, diminishes 
at Arbury Hill, and increases again at London. It may also 
be remarked, that the diminution of gravity, derived from 
Unst and Dunnose, is less than that deduced from Portsoy 
and Dunnose ; from all which it seems probable that in ad- 
vancing southward, gravity decreases more than it ought to do 
from theory ; that there exists an assemblage of materials of 
greater density than common in the vicinity of Portsoy, and 
that the density of the strata to the southward becomes less 
and less until we arrive at Clifton, where it seems to be con- 
siderably in defect. 
At Arbury Hill, a sudden increase of gravitation is percep- 
