7.0 p.m. to 7.0 a.m | 22.7 | 21.2 | 21.4 | 21.3 | 21.5 | 21.2 | 21.3 | 21.8 |
Maximum 12 hrs. | 84.0 | 83.6 | 82.6 | 81.7 | 81.0 | 80.6 | 79.7 | 78.2 |
" 10 " | 72.8 | 72.8 | 72.1 | 71.4 | 70.0 | 69.8 | 69.2 | 68.5 |
" 9 " | 66.3 | 66.6 | 66.1 | 65.6 | 64.5 | 64.8 | 64.2 | 63.3 |
" 8 " | 61.8 | 62.1 | 61.4 | 60.8 | 59.5 | 59.0 | 58.2 | 57.5 |
" 6 " | 48.8 | 49.1 | 43.1 | 47.5 | 46.8 | 46.5 | 46.0 | 45.8 |
" 3 " | 23.0 | 28.8 | 27.11| 27.3 | 26.8 | 26.5 | 26.2 | 25.8 |
" 2 " | 21.5 | 22.3 | 21.3 | 20.3 | 19.3 | 18.5 | 18.2 | 17.3 |
" 1 " | 11.0 | 11.3 | 10.8 | 10.3 | 9.8 | 9.5 | 9.2 | 9.0 |
Minimum 9 " | 3.4 | 3.9 | 5.2 | 6.6 | 7.5 | 6.9 | 8.8 | 10.0 |
" 10 " | 6.9 | 7.4 | 8.7 | 9.8 | 10.7 | 10.4 | 11.8 | 13.0 |
---------------------+-------+-------+-------+-------+-------+-------+-------+--------+

The data in the foregoing table, so far as they relate to
populations of one, five, and ten thousand respectively, are
reproduced graphically in Fig. 12.

This table and diagram relate only to the flow of sewage--that
is, water which is intentionally fouled; but unfortunately it
is almost invariably found that the flow in the sewers is
greater than is thus indicated, and due allowance must be made
accordingly. The greater the amount of extra liquid flowing in
the sewers as a permanent constant stream, the less marked will
be the hourly variations; and in one set of gaugings which came
under the writer's notice the quantity of extraneous liquid in
the sewers was so greatly in excess of the ordinary sewage flow
that, taken as a percentage of the total daily flow, the hourly
variation was almost imperceptible.

[Illustration: Fig 12 Hourly Variation in Flow of Sewage.]