Marci 15, 1873.]

     

The St, Gothard Tunnel,

The machine piercing of the Swiss tunnel through the
Alps commenced last month, The cost of the preliminary
arrangements, plant, etc., is estimated at about $400,000.
The compression of the air for the rock-boring machines
and the machine work of the shops will be effected by hy-
draulic motors*of acombined power of 500 horses. At the
northern extremity of the tunnel, there is an available fall
of water of about 95 feet, close to the entrance, which will
be utilized for turbines. At the southern end the waters of
the Tremola, with an available fall of 984 feet, will be turned
to account with turbines or by a hydraulic machine with ver-
tical column of water. It is expected that upwards of 100
yards at each end of the tunnel will be driven each month,
or considerably over a mile by the end of the year.

The Swiss Times says: The first monthly report with ref-
erence to the state of the works of the St. Gothard line has
just been published. This report, which has already been
communicated to the govertinients interested, shows that on
the 31st of December the tunnel at the Gdschenen end has
been pierced 60 feet, at the Airolo end 336 feet, or nearly 400
feet altogether. At Airolo 43 feet of the masonry of the
arch has been completed. The average number of workmen
employed during the month of December was 272—171 at
Airolo, and 101 at Géschenen. In addition to the work al-
veady executed on the tunnel proper, about 60 feet of the
cutting at the opening of the tunnel have been completed.
At this side the boring has hitherto been entirely through
hard granite. At Airolo, although softer descriptions of
stone have been met with, operations have been carried on
with extreme difficulty, on account of the water filtering
very abundantly through the rocks. Strata of dolomite and
mica-schist, with veins of quartz, have been met with.

—_—___—__—_—__2-+@>

BRIDGE OVER THE MISSOURI RIVER, NEAR
LEAVENWORTH,’ KANSAS,

There is no branch of engineering in which the native ge-
nius of America is more effectively displayed than the con-
struction of bridges. The almost illimitable West presents,
in its rivers, gofges, and mountain sides, localities difficult
enough to trouble the ingenuity and numerous enough to
weary the patience of any ordinary mortal. But these things
are to our engineers merely opportunities to display their skill
and perseverance, and the clever devices and fertile inven-
tion of our railroad constructors have always been equal to
the occasion, and have elicited the admiration of the civil
engineers of the old world. Our present instance is a bridge
for both railroad and highway traffic, erected over the river
Missouri at a distance of 18 miles north of Leavenworth,
Kansas. It is entirely of iron, and very substantial; and it
presents a fine appearance. The funds required to construct
it were principally raised by bonds, which nearly all the pro-
minent citizens personally pledged themselves to redeem,
and which were thus negotiated in New York.

Work on the approach was commenced on July 20, 1869,
but the piers were not started until October following. On
October 20 the first column was placed in position, and on
July 1, 1871, the whole substructure was completed. The
bridge would have been completed fully twelve months

 

Scientific American.

earlier, had not many vexatious delays occurred. The total
weight of wrought iron in the bridge is 2,093,300 Ibs., and
of cast iron 700,417 Ibs., making a weight of iron per lineal
foot of 2,812 lbs. “exclusive of the floor. The bridge consists
of three spans, the western and middle being each 340 feet,
and the eastern, 314.. Being intended for both railway and
highway traffic, a single railway track is laid in the middle
ot the roadway, and the top course of floor planks is laid even
with the top of the iron rails, so that wagons can pass freely
from one side to the other. The western railroad approach
may be considered as extending from the end of the bridge
to a point where any railroad desiring can connect with it.
This point is about 1,500 feet from the bridge, and is reached
by a cutting through a hill, witha maximum depth of 50 feet.
The eastern railroad approach commences at the bridge, with
a substantial wooden trestle 50 feet high, decreasing in hight
to 35 feet in a distance of 1,600 feet; it is then continued by
an earth embankment 2,400 feet further, to a point where
the grade is but 10 feet above the natural surface, and where
all desired railroad connections can be easily made.

The most remarkable feature about the bridge, and the one
which, by its comparative cheapness and peculiar adapta-
tion to the conditions of the Missouri river, enabled the work
to be undertaken and completed, is the use of pneumatic
iron columns for piers. In no case had this principle been
carried to such a depth or to so great a hight. How success-
ful the experiment has proved is best seen and appreciated
by an inspection of these graceful and substantial piers.

The total cost ef the bridge was $800,000. The whole
work was planned by the engineer in chief, General W. W.
Wright, under whose personal supervision it has been exe-
cuted,

_ OO em

 

Rather Foggy.

There often appears in Europe and in some parts of
America, a peculiar kind of dry fog which is visible during
the early morning of summer days, and is regarded as a
presage of fine and warm weather. It is of a reddish tinge
and is hardly visible except through distances of several
miles, when it appears near or above the horizon in propor-
tion as the dryness and heat of the atmosphere are less or
more augmented.

In explanation of this phenomenon, M. Collas, in Les
Mondes, advances the theory that it is due to the combustion
of aerolites or shooting stars. These bodies, coming within
the sphere of attraction of the earth, are precipitated to its
surface at a speed which is considered to exceed twelve
miles per second. By this great rapidity, they are heated,
inflamed, and finally volatilized. The vapor thus produced
is rapidly condensed into particles so extremely small that
they may be regarded as the last limit of the divisibility of
solid matter. These descend to the earth with great slow-
ness on account of their tenuity, and are scattered, by the
winds, to various quarters where they appear as the dry
fogs.

1 er ee
Ruins of the Boston Fire,

Although it is some months since the great fire, the rains

and snows of winter have not succeeded in entirely quench-

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

THE GREAT KANSAS

 

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ing it. In many parts of the burnt district, dense columns of
smoke are still ascending, and bright flames dart out from
beneath piles of brick and granite. The influence of heat
upon various kinds of merchandise found among the ruins
has afforded, says the Boston Journal of Chemistry, examples
of metamorphosis interesting and curious in a high degree.
Huge piles of leather in some cases were precipitated into
cellars, and so covered with débris as to undergo a kind of
dry distillation or fusing, out of contact with air. The re-
sultant mass resembles a dry gum, with a clean vitreous
fracture, upon the surfaces of which are seen the lines be-
tween the hides, like thin strata in a mass of silt. We have
a lump of coke, produced from clover seed, which closely re-
sembles cannel coal, It came from a mass of two thousand
bushels which tumbled into a cellar, and was subjected to”
dry distillation under the bricks and mortar. Many other
substances have undergone curious changes, and we may
allude to some of them at a future time.

+ 9 -e————$$_—____—

The Bar at the Mouth of the Mississippi.

A correspondent, E. B. B., of Cal., refers to the report of
Mr. C. W. Howell, U. 8. engineer, on the value of the screw
dredging machines employed. He states that between
December, 1868 and May, 1869, a channel originally 12 feet
in depth was dug down to 17 feet at mean low tide, and
nearly to 18 feet at high tide; and to show the efficiency of
this apparatus, he mentions that the channel began to fill
up when the screw ceased working. In another instance,
22,400 cubic yards of earth was dug out in 28} hours; a
channel was cut to a depth of 19 feet and another to 18 feet
10 inches. The work was done so thoroughly that, during
one year, all vessels drawing not more than 19 feet water
went over the bar, and one ship of 20 feet draft passed over ;
and he avers that there has been a depth of from 17 to 19
feet on the bar for three years and more, for proof of which
he refers to the official reports of the government engineers,

He quotes these facts to show that Mr. Stewart's state-
ment that costly dredge boats can hardly keep a channel
open to a depth of 14 feet is erroneous. The work which
he describes was done with Bishop’s submarine screw, with
spiral boiler-iron scrapers.

oo

Novel Life Preserving Apparatus.

M. Tellier, in Les Mondes, proposes a new method for
saving shipwrecked persons. His apparatus consists in a
life preserving vest, a balloon of a few cubic yards capacity
attached to the belt of the swimmer, and a receptacle for
holding liquefied ammoniacal gas which is fastened to the
life preserver. When the vessel strands, the person to be
saved turns a cock which allows the gas to flow through a
long rubber tube and distend the balloon, As the latter
rises, he jumps overboard. He is then buoyed up by his
life-preserving waistcoat and also by the balloon which, being
acted upon by the wind, tows him to the shore. “ By this
means, it is suggested that a person might carry a line from
the wrecked vessel to the beach, or an apparatus might be
devised to contain several individuals who could thus be
drawn ashore in safety.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

AND MISSOURI BRIDGE,