appendix:. 61 



pressure. This work of cutting, or rather of picking out, was 

 considered to be of the greatest consequence, as may be imagined 

 when we find that the surface of the foundation exceeded 1 acre. 



An idea of the difficulties that were attendant on the building 

 of this dam may be formed, when we are told that in getting 

 the foundation alone built there Avere five locomotive engines 

 and eight centrifugal pumps kept going night and day, and 

 every day, for a long period, as method of keeping the waters 

 lifted and diverted from the foundation by means of a tunnel 

 through the range at the side. It is a source of congratulation 

 that this cement concrete work has here proved its eflicacy. 

 The pebbles in the river, together with the stone in the immediate 

 position of the dam, were mixed with hydraulic cement, sand, 

 and water, into a concrete, which was immediately laid in its 

 place on the works. The cement came in the usual form of casks 

 of cement, whilst the pebbles, the stone, and the sand were 

 obtained from the bed of the river in any required quantity. 

 Last winter, and under the severest cold, but assisted by some 

 warming appliances, the work was carried on uninterruptedly 

 and prosperously. 



The sluice-gate with the inlet canal for the outflow and for 

 the occasional cleaning out of the new lake of Perolles is now 

 finished. A casting, which is 23 feet long, 8 feet 2 inches broad, 

 and 8 to llj inches thick, serves for the basis of the same. It 

 is formed out of one vertical cast-iron frame, made from four 

 pieces of T-formed shape, in which a guideway wall is set, and 

 which is made out of 7 inch square timbers of oak. The tunnel, 

 which is cut through the rocks on the left side of the dain, was 

 for the purpose of diverting the waters of the river whilst the 

 dam was building, is now about to be closed again. 



Through this damming up of the Saane the waters, which have 

 a flow equal to 30 cubic metres, equal to 6,6l7i gallons per 

 second of time, are raised 31<i feet to 39^, and thereby a dis- 

 posable water-power is obtained which is equal to 2,600 and up 

 to 4,000 horse-power. 



By this embanking the water is at the same time thrown back 

 over a considerable surface, much in the same way that we observe 

 the formation of lakes in our Alpine country ; and through the 

 swelling and backing up of the waters a new lake has been formed 

 which Mr. Hitter has named the " artificial lake of Perolles" ; 

 but it is expected that the present depth of the lake at starting 

 will not be maintained, because of the sediments of sand and earth 

 masses, which in course of many years will be sure to afl"ect its 

 depth. However, the flow of water per second of time througb 

 the artificial fall will not thereby be altered, and therefore the dis- 

 posable power will remain unchanged. 



