View report page

190
in the number of microbes in the filtered water compared with
those found in the raw river waters. He attaches the utmost
importance to this, on the ground that "the smaller the
number of microbes found in a given volume (of water) the
less is the probability of pathogenic organisms being present."
If there are no pathogenic organisms present, all is well. And
none have ever been found. Formerly, the water for this
bacteriological examination was collected with the samples
for analysis, but as it was found that microbes multiplied
rapidly during the tew hours which elapse between delivery
of the water from the filter beds and its arrival at the standpipes
in Town, arrangements were made, at the request and
expense of the Companies, so that the samples for microbecultivation
should be collected from the filter-wells (this being
"the only trustworthy method by which the efficient filtration
and comparative bacterial purity of the Metropolitan waters
can be ascertained"), with the result that almost complete
sterilization of the water is found to be effected by
filtration. The results of these examinations are duly set
out by Dr. Frankland. It will suffice to say here, that the
mean number of microbe colonies, per c.c. of the raw river
water, in May to December, 1892, was 2,908: the mean
number, after filtration, in the Local Companies' supplies,
was; Chelsea Company's water, 7; West Middlesex, 13;
Grand Junction, 48. The observations made go to show,
inter alia, "That the water in the gravel flanking the Thames,
is, bacterially, of enormously better quality than that of the
adjacent river," thus proving that " bacterially, as well as
chemically, filtration or percolation is immensely more efficient
for the purification of water, than mere flow for scores of miles
in a river," and that it is possible, by careful filtration, so to
arrest microbes and their spores as to transform the river water
into a beverage which, bacterially, is but little inferior to that
from deep wells in the chalk. Dr. Frankland observes that
his examination of the filtered river waters has not yet been
continued long enough to enable him to suggest a standard of