ales

Atv1:Ea.1oA_N RAILROAD JOURNAL.

been extracted. The average thickness ot this lode
is not more than one root, and though sometimes
thinning out to less than half this width, it is never
found, I believe, of more than two feet thickness.———
It has furnished of stamp work about 700 tons, oi
quality not inferior to the stamp work of the Cliff
mine, and the supply is now rapidly increasing-
there being 24 miners below engaged in “sloping
backs,” including those driving the bottom levels.

A steam engine has been put up this summer to
drive the stamps. There are eight of these, each
weighing-—3the heads 350 lbs., the shafts and iron
work about 150 lbs.-, their lift 12 inches. It is esti--
mated they will stamp about ten tons of stone at day.
The machinery is of the most efficient character and
well arranged.

The expenditures up to the present time have been
about $’;¥,:=l.‘3,000; of which about $310,000 were for ex-
ploring at. various points before striking the main
lode. The remainder hasbeen for surface work, as
building houses and roads, and cleating land, for
mining, and for the purchase of the engine and 800
acres of land.

The mine is properly regarded now as having as-
sumed a decided character, and must well reward
the outlay made upon it. its success, for which the
whole credit is due to the perseverance of Mr. Ba-
con, is ofno small consequence to the whole region
——for with the most insignificant show originally to
encourage mining operations, the veins of quartz,
laumonite, and chlorite in the greenstone being
proved to lead to rich veins in the amygdaloid, pre-
cisely as at the Cliti mine, a character is given to a
multitude of other points presenting similar features
scattered throughout the country, which others will
hereafter take up and prosecute with confidence and
success.

ALBION AND Munomt.

Next to the North American Mine, a mile fur-
ther on, on the same ridge, are the veins of the Al-
bion and Medora companies. These companies
have now been consolidated into one. Operations
were commenced at this tractabout the same time
as on the North American; and during the summer
of 1846 1 had an opportunity of witnessing their
progress for some time. The outward show of
their veins was similar to that of the Cliff and N.
A. mines, and was generally regarded much more
promising than thatoi thelatter. In position on the
ridge, and in mineral composition there was no
essential difference in the veins of all these mines
as seen in the greenstone trap; excepting only on
the top of the ridge, the vein called the Medora af-
forded solid sheets ot a metallic substance, which I
found to be composed of copper and arsenic,associa-
ted with a small portion of sulphur; perhaps what
is described under the name of “white copper.”——
It is the onl_y substance oi the kind I have seen in
the country. At the base of the cliff the feeders,
strttck in search of the vein, contain copper bttt
none ofthis compound. The amygdaloirl here lies
much deeper than on the exterior of the ridge east-
ward. The veins have never yet been proved in
this rock, To do this the Albion vein requires an
expenditure of from 1,000 to $2,000 in running up
an adit from the swamp to the rock——a distance of
480 feet; from the east ot which, 72 feet below the
surface, as proved by some experimental workings,
a shaft may be be carried down on the vein in the

amygdaloid. The promise of the vein richly war-
rents this expenditure. So of the Medora, which
may be proved with considerably less expense; the
adit being already completed. At present nothing

 

 

l

(160 acres) is secured by purchase of the govern-
ment at the maximum price of $5 per acre--this
tract. covers all the veins.

On the exterior oi this range of trap to the east oi
the Cliff mine are found the mines ofthe late Lake
Sztperior Com_72a.ng/ of Boston, now the P/taznia; Com-
PMIZ/, on Eagle river, the Cnppcr Falls Compcmy, the
North I/Veslern Covztpasny, and the North W/est Min-
ing Company——a description of which will be given
in the order in which they are named. I-1.

 

" ‘ Crcvasses.

The occurrence of a new crevass at Point Cou-
pee. on the l\/lississippi, leads us to offer some re-
marks on the. subject of crevasses generally. The
volume of the Missisippi is so immense that peo-
ple are apt to look on the task oi filling up breaches
in its etnbankments as almost hopeless 2 we may
therefore give more correct views on the subject by
showing the actual amount of force to be overcome
in the case.

The depth of the Mississippi has nothing to do
with the amount of rush through a crevasse in its
levee: neither indeed has the width of that river.——
The velocity of the water passing through the
breach is also calculated to give an erroneous idea
of the power exerted. The impact of the stream
on any surface that may be opposed to it directly,
is simply the weight of a column of water having
that surface for its base and the mean height of the
head corresponding to the velocity for its altitude.—-
The proofof this is clear enough: the pressttrc of
that altitude had met from the levee previous to the
breach an equivalent of rcsis/.c7t.cc; and this reszhtcvzcc
being simply that necessary to hold in eqztalibrio a
certain temlcrtcy la motimt, the motion resultingfrom
the withdrawal ofthe resistence is therefore neither
more or less than this pressure. N ow as water pres-
ses equally in every direction, one foot exerting lat-
erally a force equal to a column six inches high-
two feet aforce equal to a column twelve inches
high, and so on in arithmetical progression, the to-
tal impact on a dam resisting the stream through a
crevass is equal to the weight of a column of water

the water at the face of the dam for its altitude.
The following will, we should think, he found an

effective means of stopping crcvasses :—First where

the depth as in the existing crevass at Point Cou-

of best wrought iron be secured by a nut and wash-
er to the face of a pile planed and straightened on
one of its sides ; these ringbolts to be so placed that
when the pile shall have been driven to the depth
required, the lower bolt will have reached the bot-
tom of the channel while the upper shall remain
some twelve inches above the water. Forge a col
lar and screw—tliread on one end of a wrought iron
jagged bar ofsuch a length that when the collar is
screwed home to the under side of the upper ring-
bolt, the other end ofthe bar shall be a few inches
below the lower ringholt. One bar of this descrip-
tion is to be bound on firmly to each side of a sheet
of strong canvass so that the top of the canvass fits
up to the collar; and, being bound along the bar to
within a few inches of the point, the tail of the can-
vass, extending for five or six feet beyond this, is to
be loaded with narrow strips of lead sewn on to the
canvass vertically. This tail will lie closely to the
-indentations of the bottom. A pile driver may then
be brought along side; and (the bars of the sheeting
being fastened into the ringbolts by the collar and
screw-nut,) the piles may be driven into position.-

is doing at these mines. A quarter section of land Another sheet may then be sunk on another pair of

having that dam for its base and half the depth of

pee is not greater than five feet, let two ringbolts,

piles, the inside pile of thelast sheet making a close
joint with the outside pile of the first; and so on pair
after pair until the chasm be closed up. In order
to save the sides of the crevass, it would be well to
commence the operation by spreading canvass or a
few sheet piles around them: the canvass of the
dam should always be sunk width for width at each
side, so that the closing width shall be in the mid-
d e.

Secondly, V‘Vhere the depth is more than five feet
we would suggest the following: Take two piles,
(straightened as in the above case, or if necessary
ploughed and tongued on the edges,) and mount on
each an iron bar with ringbolts, as before described,
except that in this case the necks of the ringbolts
must project from the pile a suiiicient length to leave
a clear space between the pile and the bar of from
three to six or eight inches, as may be reqt1ited.——
In this space fit over two {piles a timber sheeting
oi the necessary scantling, leaving it room vertical-
ly to play without straining with any inequality in
the driving of the piles. When the piles have been
driven into position, close up the joints of the sheet-
ing by drivingfwedges between the, ringbolts
and the upper batten of the sheeting. It would be
well to attach to the lower timber of the sheeting a
tail of canvass loaded as iii the former instance, and
if found practicable light sheeting piles of some
three feet long. In this last case the lower timber
must be secured to the piles in a manner to resist
upward pressure. If there should be any tendency
in the sheeting to slip endwise out ofits place, it had
better be held by wooden keys resting against the
insides of the piles. Piles sheeted in this way to
the required depth may be sunk pair after pair at
each side until the chasm is closed; always taking
care that the sides of the crevass for some six or
eight feet at each side of the dam be protected by
sheeting piles. It may be found necessary to sheet
the piles on the inside as well as the outside. For
this purpose a number of wrottght iron screw-bolts
should be fitted into each pile, the head, resting on
a wrought iron plate at the outside and the screw
point projecting beyond the inside for the necessary
length. Wlien the piles have been driven home,
sheeting may be secured to them on the inside,
always placing a washer under the nut. As each
tier of inside sheeting is bolted on, thebottom be-
ing cleared out for ten or twelve inches, tough clay
well puddled, is to be beaten in between the sheet-
ings. In greater depths than nine or ten feet, an
additional row of piles would be necessary, these to
be driven first and secured by waleing pieces to the
outside row.

Wheti the dam is made across the chasm the em-
bankment is to be carried up in the usual way, and
proportioned in the ratio of the force exerted against
its several parts. The minimum force is at the wa-
ter line, the increase going on in an arithmetical
progression until the force becomes a maximum at
the bottom. This defines the inside slope of an
embankment resting against piles as a slope ofone
to one. The specific gravity of earthwork may be
taken at one-third more than that of water; and
therefore this embankment is more than an equiva-
lent for the resistence of the water at its face; but
the difficulty of making it perfectly water-tight cou-
pled with that property of water by which a verti-
tical film, ever so thin, insinuating itself into the
body of the embankment, exerts the same pressure
on the portion within it as the total pressure on the
face of the dam, requires that a wall ot tough clay,
tree from vegetable matter, well rammed and ther-
oughly puddled, be carried up from the foundation

._.