FUNGUS DEPOSITS IN UNFILTERED WATER MAINS 
Places Where Examinations were Made 
i . Lake Vyrnwy — 
[a) Water of lake. 
(b) Bottom of lake. 
1. Surface of straining gauge. 
3. Water at intake and exit of aqueduct. 
4. Deposit along sides of aqueduct at numerous points both in the brick culverts 
and in iron pipes. 
5. Reservoir at Oswestry — 
(a) Water of reservoir. 
(fi) Bottom of reservoir. 
6. Surface of filter beds. 
7. The filtered water. 
8. The sides of the filtered water pipes. 
Methods 
In the case of water, I have found by far the best method of examining solids 
in suspension to be to centrifugalize definite quantities and to read off the amount 
deposited in special centrifuge tubes. In this way it can be determined that the 
solids in suspension are more abundant in the lake at the origin of the aqueduct than 
at the Oswestry end, and that filtration removes the greater part. 
In the case of the bottom of the lake at Vyrnwy and of the settling reservoir at 
Oswestry, I use a special suction apparatus, operated from the boat on the surface of 
the water. By this apparatus I have been enabled to thoroughly examine the bottom 
of deposits at very numerous points, and at depths varying from eighty feet to a 
few feet. 
In the case of the aqueducts, I have scraped off the deposit from the interior of 
the iron pipes and brickwork when the water has been turned off. 
Character of the Deposit 
Wherever it occurs the appearance of the material is very characteristic, it very 
closely resembles a fine coffee ground deposit, it has a golden brown colour, but in 
any quantity it is a very dark brown. It is heavy, and falls to the bottom. I have 
found it distributed over considerable areas of the bottom of the lake, in some places 
more abundant than at others. A very considerable deposit of the coffee ground 
material has formed where the compensation water passes from the lake to form the 
River Vyrnwy. On the bottom of the settling reservoir at Oswestry, especially near 
the mouth of the Vyrnwy Aqueduct, there is also a large deposit. 
