Paper on the Length of the Pendulum, S27 
the observations with the pendulum, on the northern sta- 
tions of our trigonometrical survey. An answer was immediate- 
ly returned by our Government, expressive of a wish to re- 
ceive them ; and, at the same time, it was proposed to request 
from the French a platina metre, taken exactly from the plati- 
na standard preserved at Paris. 
It was in consequence of these measures, that the Report, 
which has been recently printed by the House of Commons, on the 
length of the pendulum, was drawn up by Captain Kater ; so 
that Lord Stanhope’s measure in the House of Lords did not 
render the above address nugatory as has been asserted. 
Having been the means of directing Mr Gilbert’s atten- 
tion to the length of the pendulum, and feeling a deep inte- 
est in the subject, I have been induced to give Captain Ra- 
ter’s paper a careful examination ; and in doing this, I have 
noticed several minute errors in his calculations, which ought 
not to be overlooked, since the question is about very minute 
quantities, such, for example, as the 10,000th part of an inch, 
or the SOljSSOth part of the whole length of the pendulum. 
And since its length may be thus assigned to such a degree of 
exactness, it evidently follows, that the intensity of the force of 
gravity may be determined with the same degree of precision ; 
and thus one part in 39 I 5 S 86 will be rendered sensible. 
And as it seems probable, that the variation in the density of 
the strata immediately under the surface of the earth, may pro- 
duce a change in the intensity of the force of gravity much 
more considerable than one part in 391,386, it follows that this 
variation will so sensibly affect the movement of the pendulum, 
that it will not fail to give information of such irregularity in 
the density of the strata. 
The force with which Schehallien disturbed the plumb line, 
was found to be about the 34,376th part of the force of gravity, 
or about eleven parts in 391,386 ; and I think with the Edin- 
burgh Reviewers, that the presence of an extensive stratum of 
gneiss, or of hornblende-schistus, or of any great body of gra- 
nite, immediately under the surface at one place ; and of chalk, 
common sandstone, or limestone at another, — would produce a 
difference in the intensity of gravity, even greater than the force 
just now mentioned. 
