He stationed one of his assistants at the point where the Rhone again comes to the surface and with the help of others, miles above at the mouth of the cavern, he sent in logs of wood, bladders and other buoyant objects, none of which were observed to pass through by the watcher below.

The last and deciding experiment, was sending in a pair of live ducks and these, also were lost.

He then concluded to start below the cavern and selected the little village of Seyssel as the best point to prepare for the voyage.
The Rhone when high is one of the most rapid rivers in the world, and Paul's trip from Seyssel to the Mediterranean was the swiftest he ever made.

The entire distance is five hundred kilometers, or three hundred miles, and his actual running time was sixty hours.

He was enabled to push along at this unusual rate on account of the freshets swelling the river to a flood.