place
of our common dome for the drying of the steam, and the other is
constructed for the receival of all saliferous and calcareous sediment
that may separate from the mine waters used in such boilers. For
instance, a couple of boilers, each 16 feet long, and 54 inches
diameter, the steam-pipe connects with each boiler in their centre, and
here the safety-valve is also placed on the branch connecting with the
steam cylinder. The "mud" drum underneath these boilers is connected
and placed rectangular with the boilers, about 18 inches from the stack
end. It measures 14 feet 9 inches in length, with a diameter of 30
inches, and a cast-iron pipe leads from the bottom of the mud drum
outwards, the same as with ordinary blow-off pipes, with a proper
stop-valve. The steam drum, placed on top and also connected by means
of a short cast-iron pipe with the boilers, besides drying the steam as
with our domes, assists also in the general circulation of the water,
whilst the mud drum prevents, in a very considerable degree, the
incrustation of the boilers, tubes, and drums, thus obviating
altogether the frequent necessity of their being cleaned ; because,
likewise, the more rapid circulation in these boilers prevents
sediments forming as in boilers where the water is less subjected to
ebullition whilst under great temperatures and steam pressure.
WINDING OR HOISTING MACHINERY.
The
American winding machinery for very deep mining is characterised by a
proportionate strength, great weight of metal, compactness, and
unusually effective brake power. Amongst these winding machines, one
had just been built in San Francisco by the Messrs. Prescott, Scott,
and Co., who very kindly afforded me every opportunity to inspect same,
and to procure full working tracings, with other particulars. As this
machine had been calculated to wind from the future 4,000-foot level by
the Yellow Jacket Company, Comstock lode, if required, I was very glad
to get this information as a guide for our future endeavors in the same
directions. The two coupled cylinders were each 26 inches in diameter,
with a stroke of piston of 6 feet; and both cylinders, drums, and gear
are all fixed to one solid bedplate. The cranks—Californian engineers
discard cranks, and have solid hammered-iron "discs" instead—and the
winding shaft is made of best hammered iron, splendidly finished. The
winding shaft, 16 inches in diameter, is round, except at the boss for
spiders, where it obtains an octagon shape for a diameter of 18 inches.
The ordinary speed for winding is not less than 55 feet per second, and
by means of clutches winding can be done from any given depth, or also
at various speeds. These large engines are all worked, in California
and Nevada, and looked after by a double set of drivers each shift, or,
in other words, each driver has one drum and half the machine under his
control, whilst firemen look after the boilers. The machine in
question, inclusive of an equally powered pumping engine, would consume
30 cords of firewood (pine and oak) every twenty-four hours, which fuel
is delivered at the mines at 14 dollars per cord, or about 55
shillings. The poppet-heads, or " gallows," for this same plant are to
be of clear sugar-pine, the two principal supports, or legs, measuring
18 inches by 24 inches diameter, and 50 feet high. These are to be
fixed, like all others in those mines, 10 feet clear of the ends of the
shaft, thus being—as the shafts are generally 20 feet long in the clear
of timber—40 feet apart, giving good room all around the pit's mouth.
The sheaves are of cast iron, with wrought-iron "rims" shrunk on, and
measure from the centre of the
