255
as the tunnel
the most important element. So far has been formed the rock stands without lining and the probability is that a similar character of rock will be found throughout.
The condunt from the tunnel to the town presents no special difficulties. The syphous will be simple in construction. The Surveyor Ieneral proposes to use duplicate pipes each of 2 feet diameter. One such pipe will however convey
almost double the volume of water to be
passed through the syphous. I therefore would only use one such pupe to cross the valleys.
In the best regulated towns in England, where water is supplied at constant service and high pressure, for such a population as that of Hong- Hong, 12 or 14 gallons of water per head of the population will be sufficient for all purposes,
so that there will be water sufficient for
a
population of 180,000 and
up
to 200,000.