32 PLATEAU ON THE FIGURE OF A LIQUID MASS 
swell out all around. Now as soon as this phenomenon takes 
place, it will be conceived that the attraction exerted by this 
bourrelet on the liquid remaining around the axis must be an ad- 
dition to the action of the centrifugal force, and contribute to 
increase the volume of the Lowrrelet at the expense of the central 
liquid. Hence, therefore, it may evidently result that all the 
liquid shall leave the axis for the dourrelet, and the latter be- 
come in a manner a veritable ring. 
This generation of the annular figures would therefore be in- 
dependent of the law which the attraction follows, and would be, 
in consequence, the same in the case of universal attraction and 
in that of molecular attraction. 
17. It is easy to verify this mode of generation upon our mass 
of oil, or at least to assure ourselves that during the formation 
of the Jourrelet and of the ring, the angular velocity is much 
less at the equator of the mass than towards the axis. For this 
purpose I shall first point out that when a certain number of 
experiments have been performed upon the same mass of oil, 
and this has been several times disunited and re-formed into a 
single sphere and into a ring, it always holds within it a multi- 
tude of small bubbles of alcoholic liquor, which, borne along by 
the oil that surrounds them, render the movements of the differ- 
ent points of the mass perfectly observable. Now, if the ex- 
periments which we have described be repeated with the aid of 
a sphere of oil thus filled with alcoholic bubbles, the following 
results are observed. So long as we give to the disc such slight 
velocities only as are sufficient to produce a simple flattening, 
there is not a great difference of angular velocity between the 
portions next to the axis and the portions adjoiming the equator ; 
but this difference becomes very considerable when the disc turns 
more rapidly, and the Jourrelet and the ring are developed. 
We may thus prove, by means of the small alcoholic bubbles, 
that the mean angular velocity is established in the ring once 
formed, and that all the points of the latter perform their revo- 
lutions in the same time. 
Furthermore, in our experiments upon the masses of oil, there 
are two foreign forces which act, in addition to the causes which 
we have noticed, to facilitate the development of the bourrelet 
and of the ring. One is the resistance of the ambient liquid, 
which contributes to weaken the angular velocity of the equator 
of the mass; the other is the action of the hand which keeps up 
