View report page

113
Prof. Frankland's observations on the connection
between the flow of the Thames and its bacteriological
purity. The variations in the volume of the river
in 1895 are incorporated in Table 33, and it will be
seen that the number of microbes per c.c. varies with
the flow as measured at the Teddington "Weir. It
will be noted that in storage the number of microbes
is reduced, and it is generally said that sunshine
plays an important part in such reduction.
In connection with this, the results of certain
experiments detailed in the Report are of interest.
The details of the experiments are as follows:—
A sterile bottle was half filled with Thames water and violently
agitated for five minutes to ensure equal distribution of the organisms.
Immediately afterwards a number of sterile glass tubes were
partially filled with this water and hermetically sealed. Three
of these tubes were immediately packed in ice and the remainder
were attached in duplicate, at different distances apart, to a
light wire frame which was then suspended vertically in the river.
The experiments were made near the Grand Junction Water
Company's intake at a place favourable for the sun's rays to fall
on the river without any obstruction. The river was at the time in a
very clear condition and contained but little suspended matter whilst
the day was fine, although clouds obscured the sun occasionally. The
tubes were exposed to light in the river 4½ hours (from 10.30 a.m. to
3 p.m., on May 15th, 1895). At the end of this time the tubes were
packed in ice for transport to the laboratory, where the cultivations
were started immediately. The colonies were counted on the fourth
day, and yielded the following numbers:—
No. of
Colonies
per c. c.
Thames Water packed in ice immediately after collection 2,127
„ „ after exposure to sunlight for 4½ hours
„ „ „ „ at surface of River 1,140
„ „ „ „ 6 in. below surface 1,940
1ft. „ „ 2,150
„ „ „ „ 2 ft. „ „ 2,430
„ „ „ „ 3 ft. „ „ 2,440