Observations on Polluted Waters . 
387 
1883.] 
the Vesle above and below Rheims. The alleged changes 
are the more striking as the Vesle is not a river of enormous 
length. If we allow thirty-six hours as the length of time 
required by a drop of water from the clean regions above 
the “ French Leeds” to the clean regions below, we shall 
be on the outside of the truth. 
To throw a little more light upon the subje(5t I took three 
kinds of water : 1st, raw, undiluted sewage, which I ob- 
tained from Aylesbury ; 2nd, similar sewage partially puri- 
fied ; and 3rd, sewage fully purified, as it passes from the 
works of the Native Guano Company into one of the 
branches of the Thames. The sewage in question is strongly 
animalised, containing, in addition to the usual excrementi- 
tious matters and liquid household refuse, a somewhat 
unusual proportion of blood, derived from the cattle slaugh- 
tered in Aylesbury for the London dead-meat market. 
What may be called industrial contamination is totally 
absent. Of each of these three kinds of water the one-half 
was filtered and the other left in its original state. I had, 
therefore, now six kinds of water in my hands. Of each of 
the six I placed portions, differing in bulk, in a number of 
white glass pint bottles, loosely stoppered, and arranged on 
a shelf exposed to the morning sun. In some of the bottles 
the stratum of water was ij inches in depth ; in others 
3, 4, &c., up to 6 inches. The bottles were now regularly 
examined to see what changes would take place. In the 
bottle containing the best purified water, filtered, and in a 
shallow layer, a green confervoid vegetation appeared in a 
couple of days ; it increased, and bubbles of oxygen were 
formed and rose to the surface. There was no offensive 
odour. Similar phenomena were observed later in the other 
bottles ; but eight weeks passed over before green vegetation 
appeared in the bottle containing 6 inches in depth of raw 
unfiltered sewage. In the meantime the odour given off 
from this bottle had been very offensive. It must also be 
remarked that in this bottle, along with the green confervoid 
growths, there appeared a small quantity of white sewage- 
fungus, which was only gradually burnt up by the oxygen 
liberated by the green vegetation.* 
Hence it would appear that, according to common belief, 
the appearance of green vegetation, unaccompanied by 
white fungoid matter, is a favourable sign ; that sewage can 
purify itself, but that the process is very slow ; that the 
* This is the first time that I have watched the appearance of sewage- 
fungus in stagnant water. 
