FUNGUS DEPOSITS IN UNFILTERED WATER MAINS 
4i3 
the hyphal character of the flakes is much more evident, and long unbranched threads 
can be seen possessing a greater or lesser amount of sheath. Professor Campbell 
Brown has drawn attention to this organism, and there is every probability that it is 
a gelantinous iron forming thread fungus of the Cladothrix, Leptothrix, Crenothrix 
group. In none of the deposits which I have examined, have I been able to detect 
active growths of the organism, it almost invariably occurs in the short, irregular, 
broken fragments or flakes described above, a group of such fragments is well seen 
in Fig. 4 embedded in a gelatinous matrix. A most remarkable feature is that the 
gelatinous material appears to increase with age ; it is not on the actively growing fila- 
ments that it is most abundant, it is thickest on the broken and apparent dead fragments. 
The history of the deposit would appear to be as follows : — 
The iron fungus grows in some parts of the watershed, fragments are carried 
with other debris into the lake, and they fall to the bottom, other larger and younger 
threads float in the water of the lake and are caught on the copper gauze strainer, 
innumerable small fragments however pass through the strainer into the aqueduct 
and gradually collect at the sides and form a coat on brickwork, wood, or iron of the 
pipe. Their gelatinous nature facilitates their adhesion, and they entangle with them 
all kinds of other debris as sand, diatoms, etc. With age the lower layers of the 
deposit appear to become more and more compressed and to lose all resemblance of 
fungus origin. 
Not all the particles are deposited on the sides of the pipe line, some pass on 
with the water into the Reservoir at Oswestry, and no doubt also particles are con- 
tinually being detached from the surface of the aqueduct. But the filters remove them. 
There is no doubt that the gelatinous sheath makes it exceedingly difficult for them 
to be carried through the sand of the filters. The result is that there is no deposit 
in the filtered water pipes. 
As mentioned at the outset, Lille and Berlin were greatly troubled by deposits 
produced by Crenothrix, in the case of Berlin it is stated that they found a sediment 
many inches deep in the reservoirs. 
Relation of the Organism to the Iron 
There are numerous examples of bacterial activity leading to the oxidation of 
dissolved iron, and a group of organisms have been called ' Iron ' and ' Manganese ' 
bacteria from their power of producing the oxide of these metals from the soluble 
forms dissolved in the water. To this group Crenothrix and allied thread forms, 
including the present one, belong, and if Winogradskv is correct, the filament 
absorbs the soluble iron salt and deposits the oxide in its sheath. 
Zopf regarded the process as mechanical. It appears to me to be exceedingly 
difficult to interpret the abundant formation of gelatinous material, and the abundant 
oxidation in the oldest filaments. The presence of the fungus is not peculiar to the 
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