m
of the siphon empties itself into the main receptacle, and by so doing
cleanses the screen. During a rain or the washing of the streets, the
siphon can work in concurrence with the ordinary discharge-pipe. It is
evident of course that these two--pipes can be placed on the same side of
the apparatus, if this prove the most convenient arrangement.

We will add that this apparatus can be applied not only to the Liernur
system, but also can be used for preventing the entrance of obstructions
into sewers of the ordinary type, where the grade is small or where the
quantity of water is insufficient; and if we adopt the system of
"everything to the sewer," can we not find in the employment of this
apparatus an element for the realization of the famous formula, "Always in
circulation, and never in stagnation?"--_Le Genie Civil._

* * * * *

[Concluded from SUPPLEMENT No. 454, page 7249.]

WATER-POWER WITH HIGH PRESSURES AND WROUGHT-IRON WATER-PIPE.

By HAMILTON SMITH, JR., M. Am. Soc. C.E.

METHODS OF CONDUCTING WATER AND TRANSMITTING POWER.

A description of the mode of using water-power for driving the North
Bloomfield tunnel in California, some years since, will give a good
illustration of some of the advantages of the hurdy-gurdy. This tunnel was
originally about 8,000 feet long, through a slate highly metamorphosed,
with its general line passing under a good-sized stream, at a depth of
about 190 feet. There were eight working-shafts, each about 200 feet deep,
which, with the lower entrance or portal, gave sixteen working faces.
Diamond drills were used at the lower heading requiring power; the other
fifteen headings were driven by hand-work. It was uncertain how much water
would be encountered; but from the location, it was evident that a large
quantity might be struck in any shaft, and hence it became necessary to
have ample power at hand at each opening, in readiness for such an
emergency. A pipe main was laid along the general line of the tunnel, with
its pen-stock 285 feet vertical above the surface at the upper shaft, and
549 feet above the lowest shaft. It was made of single riveted sheet-iron,
of No. 14 (Birmingham) gauge, in lengths of 20 feet, put together
stove-pipe fashion, with the joints made tight by cloth tarred strips and
pine wedges. This pipe had a diameter of 15 inches at the pen-stock,
diminishing from this to 13, 11, and 7 inches at its lower end. From it,