In order to divert the water into this canal, it was necessary to raise its level 5 meters.  The dam, then, had to support a strong pressure, and it could not be built upon sand.  It therefore became necessary to build a temporary dam and to turn the river into a plank flume, so as to make it possible to dig at the location of the permanent dam in order to reach a solid bottom at a depth of nearly 4 meters.  The permanent dam thus had a total height of 10 meters, with a thickness of 15 at the base and 7 at the top.  It was constructed of dry stone, grass, and earth, with the addition of strong wood-work.  The rocks upon which it had to be built were full of fissures, and when it was desired to close it great leakages of water occurred, which came near ruining it and necessitated the construction of a second wall behind it and a talus of earth in front.  The dam as shown in Fig. 1, when finished, had a thickness of 25 meters at the base.  It was closed on the second of July, and had a storage capacity of 55,000 cubic meters.

The principal excavation was begun at the point where the bed was deepest, and which consequently the older miners must have had most trouble in reaching.  Here were set up two Letestu pumps that were actuated by a four-horse wheel.

These pumps lifted 50 cubic meters per hour.  All except the pump chambers and pipes was made of wood on the spot.  The water that was lifted was carried away from the works in a flume 160 meters in length, which likewise removed the water from the motive wheels.

For the service of the same excavation two simple acting inclined planes were installed that were moved by a four-horse wheel.  Fig. 2 gives a general view of the arrangement.

The tracks of these planes were made of wood.  Steel rails, however, had been brought for the cars, along with the cables and the metallic parts of the windlass; but all else was made upon the spot, including all the wooden pulleys for transmitting motion from the wheel to the windlasses.

This excavation reached bottom at a depth of 16 meters.  The second touched bottom at about 10 meters, and gave access to a subterranean canal, which was followed for about 20 meters.  The extraction of sand was effected here by an inclined plane moved by a Gramme machine.  The generatrix had to make 1,500 revolutions, and be set in motion by an overshot wheel.  As time was wanting, it became necessary to diminish to as great a degree as possible the number of parts to be employed in the transmission of motion, and since there was an abundance of water, a velocity of 15 revolutions was accepted for the wheel, which, with a total fall of 4.8 meters, had to give a power of eight horses.  A three meter pulley was placed upon the shaft of the wheel.  This was made of freshly cut wood that had been exposed to the sun.  In order to give it sufficient stability and prevent its warping, it was placed against the wheel in such a way as to rest upon the latter’s spokes.