the
" die," or our " false bottom," is somewhat different in form, as its
base for 2 inches thick is made in an octagonal form and then
contracted to a solid cylinder of the same diameter as the shoe falling
upon it, and both are cast of the best white iron. The stem is mostly
made of 3 to 3J inch diameter round wrought iron, 12 feet long, and
finished off in a lathe so as to be true cylindrical, and, except at
the lower part, which tapers a little, is equal in diameter everywhere,
so that its fall or rotation is not impeded in the guides. This taper
fits the shoe, and both are secured in the ordinary way, thus
resembling ours with exception of the disc, or " tappet," which is
secured to the stem in a very effective manner, and this is preferred
to our screw-threaded shanks, which were found in* America to wear out
too quickly from the continual jarring, and the repairs of which added
unnecessarily to the expenses for keeping them in working order. The
American smooth stem c receives the tappet d d as it is
pushed down from the top to its proper place; the tappet is of cast
iron (except at the bottom, where a wrought-iron ring is let into it),
and it has in the inner side of the round hole for the stem c a cavity or recess a for
about two-thirds of its height; a piece of wrought iron completely
fills that recess and also surrounds the segment of the stem opposite
same for the whole width of this gib a, as it is termed. A
couple of square holes are left at the back of the gib in the solid
tappet, where the latter is square, and into these holes two steel keys
b b are driven from opposite sides, thus fixing by means of this
gib the tappet or disc more securely to the stem than such could
perhaps be effected by any other method, whilst permitting likewise its
shifting as required by simply driving back the two keys mentioned. The
weight of these stampers varies greatly throughout the mining regions I
visited. At Grass Valley they ranged from 720 lbs. to 1,000 lbs. each;
ofthese, those of the Idaho Company weigh 830 lbs, each, they have 70
drops of 11 inches per minute, with a duty of 1-3/4 tons of quartz
crushed per diem. The Empire Company's stampers are very heavy at 1,000
lbs. each, with 70 drops of 9 inches per minute, and they put through,
during the same time, 40 tons with the 20 heads employed. Without
particularizing the very many machines I have inspected, I would
observe that the heavier stampers are preferred in California,
and that the drop ranges from 8 to 12 inches in depth, or taking it on
the average of 10 inches ; the curve of the cams would measure 21-1/4 inches.
The stampers are all revolving the same as in Victoria, and they fall
through their guides of sugar-pine, which last, if well seasoned, over
eight months in a perfectly satisfactory manner. The water used for
crushing is conveyed to the mortars in a similar way to ours, but
instead of one or even two jets feeding each mortar, it has been found
judicious to give each head a separate jet, so that the gratings are
equally washed and cleared in order to facilitate a rapid discharge of
the crushed quartz or ore through the same. The quantity of water
needed of course depends on the character of the ore, which, if heavily
charged with pyrites, requires more, or, if not so, less water. The
boxes, i.e. " mortars," are similar to ours, but a few
improvements are worthy of our attention. They are fed, as already
stated, by circular self-feeders (Hendy's*), and the Americans make it
a rule to feed " very thin" in order to give the gratings or "screens" every
opportunity to discharge the pulverized ore quickly, because of the
very great fineness or extra numbers of holes per square inch in such
gratings. These mortars average over 4 feet in length,
* These self-feeders were imported since, patented in this colony, and can be seen at Sandhurst.
