28 PLATEAU ON THE FIGURE OF A LIQUID MASS 
tiful ring, is about three turns per second. The ring thus ob- 
tained has a mean diameter of 9 to 10 centimetres. 
12. When, at the instant of the formation of the ring, the 
mass of oil which constitutes it separates from the disc, a sin- 
gular circumstance is observable: the ring remains united to 
the disc by an extremely thin pellicle or film of oil, which fills! 
all the space between them. But at the instant that, the ring 
having reached its greatest extent, we stop the motion of the 
disc, this pellicle breaks and disappears of itself, and the ring 
then remains perfectly isolated. 
It may be conceived that this pellicle is not a circumstance 
essential to the phenomenon of the formation of the ring; and || 
we shall see, in another part of these experiments, that it is pro- 
bably connected with an order of facts wholly different. 
13. The heavens exhibit to us also a body of a form analo- 
gous to our liquid ring. I allude to Saturn’s ring. That, in- 
deed, is flattened, whilst the transverse contour of ours appears 
altogether round; but I do not think that this difference is so 
great as it appears at first. 
In fact, the centrifugal force, which goes on increasing from 
the inner circumference of the ring of oil up to its outer cireum- 
ference, necessarily tends to stretch this ring in the direction of 
its breadth, or, in other words, to flatten it. But the flattening 
must be of very small amount; for, on account of the inconsi- 
derable dimensions of the ring, and the slowness of its angular 
movement, the kind of traction which results from the variation 
of centrifugal force must be very trifling in comparison with the 
forces developed by molecular attraction. 
14. It appears to me, then, that we may reasonably admit 
that our ring of oil is in reality slightly flattened, and that in 
consequence it only differs from that of Saturn, with regard to 
general form, in the less quantity of flattening*. But further, 
in the system of Saturn, the flattening of the ring is in part de- 
termined by the attraction of the central planet. Now, at the 
first moment of the formation of the ring of oil, the latter is sub- 
mitted to a particular force, which plays a part analogous to that 
of the above attraction. In fact, this attraction acts with the 
greatest intensity at the inner circumference of Saturn’s ring, 
—_— = = cs oa 
Se am 
* I leave out of the question here the subdivision of the ring of Saturn; 
this subdivision, as is known, is not essentially connected with the conditions 
of equilibrium of the ring. 
