Dodgeville chronicle. [volume] (Dodgeville, Wis.) 1862-current, 1866-12-13

Lake Michigan. Inc hfSt 80 feet or the
shore shaft is inclosed in iron cylinders,
three in number, one resting upon another
and firmly bolted together. Each cylinder
is ten feet long, nine feet in diameter, two
and half inches in thickness, and weighs
about 10000 pounds, or, in the aggregate,
the three together reach the enormous
weight of $4,000 pounds. When the first
of these cylinders was placed IN position on
the surface Of the ground, the miners COM
menced the work OF, excavation On the lnslde.s
As the earth was thrown out, the cylinder
OF course, settled Another section
of the cylinder was placed IN position upon
the top3of the first; when it had sunk to q
level with the surface. of the ground, the
two were finally bolted together, and the.
work of excavation proceeded. The third
having been attached in its turn, the
work was pushed forward until the shaft
reached depth Of thirty feet. This
brought the miners through the soil and
qufeksands, and some feet into the fine clay
formation, wherein they were safe from the
eruption Of water! After reaching the
above named depth, the shaft was coItract-
ed to diameter of eight feet, and thence
pushed downward to the depth Of AZ feet
| below the bottom of the cylinder, or n feet
| from the surface Of the ground. From the
| cylinder downward the shaft is lined with
brick measuring twelve inches thick, laid
! in three shells in the best Of cement. The
shore shaft, then, as completed, measures
! III feet in depth, nine feet in diameter for
the first 80 feet, and SIX feet diameter for
the remaining At feet r. " Ct r
THE TUNNEL Ok
! commences at the bottom Of the shore shaft
| II feet below the sea-sarface of the earth,
and extends, a.. right angles, q distance of
exactly two miles. It is almost circular IN
form, being feet 8 inches in height an@
5 feet wide, (ingthe clear, the variation
from al true circle being made ON account Of
the keystone of the arch. It is lined with
brick masonry, inches thick. The brick
is laiu lengthwise of the tunnel in two
shells, with 'toothing- joints" None but
hard-burned, clear-ringing, well-formed
bricks, entirely free from lime, and 8inches
long by 4 incLes wide and . inches thick,
were used in the construction of the tunnel
and they were laid in the best of cement,
only one measure Of clean, sharp sand be-,
lug allowed to one measure Of cement. In
Guiding the shore shaft, there. are nearly
5000 cubic yards of masonry, which re-
auired in round numbers about 1000, 900
bricks. The actual excavation of the tun
mel in order to give it diameter Of feet
inside the masonry, is about feet in diam
eter, requiring the removal of about 10000
cubic yards Of earth. s.-rl,
THE CRIB,
When the tunnel was. first projected, it
was objected by many persons, including
even some eminent engineers, that no prac-
ticable plan could be devised for the con-
struction of the outer or lake shaft. The
difficulty aof sinking shaft through the
water of the lake was thought to be an in
superable obstacle. 1t would be necessary,
Of course, to erect some permanent struct-
uFe to shut out the water Of the lake while
the shaft was in process Of. construction,
and the storms and gales which often rage
on Lake Michigan with violence hardly sur
passed by the most terrific ocean hurri-
cane, would, It was thought, render it ut
terly impossible to accomplish the desired
object. But the projectors of the under
taking, with resolute confidence in the fea-
sibility Of their project, had devised the
plan Of huge crib or Golfer dam. This
crib was constructed upon the North Pier,
near the entrance to the harbor, and was
one of the most monstrous structures ever
~
feet hi I'll, and had five sides, each of which
was fifty eight feet long, making the struct-
ure about ninety feet in diameter. It had
three walls--the outer wall, the centre wall
and the inner wall, each constructed of
twelve inch square timber, and-cauiked and
| paid like first class vessel. The frame
work as thus constructed, formed power
full combination of massive timber and irons
firmly bolted and braced ia every direction.
Within the wells of the crib were fifteen
separate water tight compartments, and the
inside wall inclosed a cylindrical well, open
at the top ard bottom, and twenty five feet
in diameter. Each angle Of the structure
was protected from ice by an iron armor
two and a-half inches thick. After its COM
pletion, thissmarine structure was launched
| insJune 1865, and towed to its position over
the outer terminus Of the tunnel, where
each of it's fifteen water-tight oompar tments
was filled with clean rubble stone. By this
means, the crib was sunk until its bottom
rested upon the bed Of lake, where it was
securely moored by immense cables reach
ing in every direction to huge mooring-
screws forced 10 feet into the earth. The
water here is, So, feet deep, and the top. of
the crib was therefore five feet above the
Some idea Of the magnitude Of this part
Of the work may be inferred from the fact
that the cost Of the crib exceeded $500, 600,
or nearly one-third the total contract cost
of the tunnel. There were used in the con-
struction 6186G5 feet of lumber, 6, 02G
cubic yards Of stone, 400 bales of oakum,
and IS tons of iron bolts. n 97rfiuinerr'
] After the crib had been securely moored
| &c Of nj
ing the lake shaft was commenced An
immense cylinder 81 feet in length, divided
into seven sections like that used in the
shore shaft already described, and weigh
/ ing in the aggregate 100000 pounds, was
first sunk in the well in the centre Of the
crib, of which mention has been made above.
The bottom section having been first sus-
pended in the well the next was placed up
on and firmly bolted to it, the joint being
entirely water-tight.s The Two were then
lowered when another section was placed
upon the top and SO on until all were firmly
bolted together and the bottom rested Oh
the bed of the lake.. A few inches of sand
covered the clay at the bottom of the lake
through which the cylinder forced itself by
reason of its great weight. BY means OF
a steam engine working upon the crib, the
water was pumped cut OF the cylinder.
After this, the sinking of the cylinder to
the required depth in the clayey bed of the
! lake was accomplished by the pneumatic
!, process, which operated so successfully in
securing foundations for the Harlem bridge,
New York, the bridge across the Pedee
! River, in South Carolina, and the railroad
I bridge across the Savannah Railway A
brief description of the process is worthy
| oc al sHa
l. The cylinder being in position in the GEN.
! If arIh opd oil. vr,o AZ, hor