64 APPENDIX. 



waters from coming in contact with the outer waters. The 

 remaining vacant space is filled up with the filtering medium, 

 which is composed of various layers of coarse and fine gravel and 

 of- sand, whilst above is the filtered water of the Saane and the 

 clear spring water which was discovered by the building of the 

 dam and sluice works. That clear water from the spring, which 

 is led in by a cement pipe of peculiar shape, forms no inconsider- 

 able part of the supply of drinking water for the town. A 

 further part of the supply required for the use of the town is 

 obtained by filtering the waters of the Saane, which have to pass 

 through the various levels of coarse and fine pebbles and of 

 sand, and become perfectly pure. In order to arrive at this 

 issue more easily the tower-shaped vessel is surrounded with 

 suitable stone and gravel beds, and these are supported by a 

 horizontal bed of cement, from the under parts of which they 

 are made impervious. (See section sketch, fig. 4.) In the 

 same manner the piping through the underground canal is 

 connected with the filtering works and with the pumping work in 

 the south-west wing of the turbine house, where there is a shaft, 

 in which the water comes in by natural pressure from the lake and 

 where the pumps siick it up. All this is well made, and the further 

 introduction of discoloured water is guarded against. In order to 

 prevent the cloudy water of the lake from entering the filter, the 

 upper part of the arrangement is closed, but in order that the 

 level of the purified waters may rise and fall inside, there is a 

 long open pipe (see fig. 4) placed on the filter, which in this way 

 keeps up a constant connection with the outer air. By means of 

 the pumps, when the works are all finished, the drinking water 

 that is collected in the water vessel will be forced up 160 metres, 

 525 feet, to the high reservoir at Quintzet, the highest point of 

 PeroUes, from whence it will afterwards be conducted by its own 

 gra\ntation to all parts of the town of Freiburg. 



The filtering works, with the connecting canal of the pumps, 

 have been finished for a long time ; and the experience of this 

 spring during the thawing weather, and the freshes in the river 

 which produced much muddy water, goes to prove how very 

 excellent have been the arrangements for the filtering, inasmuch 

 as only water as clear as crystal, and no discoloured water, is 

 delivered into the town. But how long this present perfect 

 working of the filter may last is another question which the 

 future will only be able to determine. But it is certain that the 

 great advantages of the present excellent filtering arrangements 

 are never likely to be hereafter lost for the possible necessity of 

 renewing them. The whole estimate for the filtering works was 

 £2,000 at the commencement, whilst the actual cost of the same, 

 from the last statement of the director (Mr. Hitter), only came 

 to £1,366 8s. lOd. 



