to detérmine the Figure of the Earth. 121 
‘an assembly to the brilliant reveries of his imagination ; and the 
genius of a Descartes would be constrained faithfully to adhere 
to that mode of cbservation and of doubt which he himself had 
promulgated, and not pretend to exhibit truth unmixed with 
error: nor with all their glory could Plato and Descartes be now 
regarded as more than mere elementary branches of this great 
orzan of the sciences :—its force wou!d outlive their genius, and 
carry into futurity the gradual development of their thoughts. 
—Such is now the noble, destiny of learned societies. The simul- 
_taneousness and the durability which their institution gives to 
the efforts of mortals, complete the power of the experimental 
method. They alone can in future give continuity to the pro- 
gress of knowledge; they alone can develop grand theories, and 
produce results which, by their difficulty, by their diversity, by 
the perseverance and the extent of exertion which they require, 
could never be attained by individuals. 
To determine the size and figure of the earth; to measure 
the gravity at the surface, to ascertain its connexion with the 
interior construction, with the disposition of the strata, and the 
jaws of their densities, are of the number of those important ques- 
tions which learned societies alone could resolve. During a 
century and a half they have formed a chief object of the 
Academy of Sciences. The first exact measurement of a degree 
of the terrestrial meridian was made in France by Picard in 1670, 
Newton availed himself of it, in order to establish the law of 
utiversal gravity. Richer, who was sent by the Academy to 
Cayenne, two years after, to make astronomical researches, dis- 
covered that his clock, which at Paris beat the seconds, went 
gradually more slowly as he approached the equator; and that 
it again went quicker, by the same degrees, in returning towards 
thenorth, so as to resume exactly its original motion at the point 
‘of his departure. Again, according to the discoveries of Huy- 
gens, the quickness of the oscillations of a pendulum augments 
or diminishes with the intensity of the gravity which causes its 
motion. - His observation proved that this intensity was different 
in different latitudes, and that it increased in going from the 
equator to the pole. Newton in his Principles of Natural Phi- 
losophy connected all these results with the law of attraction. 
He showed that the variation observed in gravity disclosed a 
flattening of the earth at the poles; a circumstance which is also 
observable in the form of Jupiter, Saturn, and the other planets 
which turn upon an axis. He conceived that this fattened form 
was a.consequence of the even attraction of the portions of every 
‘planet, combined by the centrifugal force of its rotatory motion. 
But in order that the arrangement determined by these two 
kinds of forces should thus have been able to make itself ef- 
fectual, 
