Thus in the Sandwich Islands the god Oro gave his oracles through a priest who "ceased to act or speak as a voluntary agent, but with his limbs convulsed, his features distorted and terrific, his eyes wild and strained, he would roll on the ground roaming at the mouth, and reveal the will of the god in shrill cries and sounds violent and indistinct, which the attending priests duly interpreted to the people."
The Rhone continues to roll on southwards, but no longer (as no doubt it did in ancient days) enters the Lac du Bourget, of which it receives the waters through a canal, and then leaves it on the east in order to run along the foot of the last spur of the Jura.
This is equivalent to imagining the polygon Jii Jar J14..., supposed fixed in the l~mina, to roll on the polygon J12 Jar which is supposed fixed in space.
We have seen (~ 3) that the sequence of possible positions is obtained if we imagine the body-centrode to roll on the spacecentrode.
Hence the meridian section of the film may be traced by the focus of such a conic, if the conic is made to roll on the axis.