CIVIL ENGINEERING.
GREAT BRIDGES--PNEUMATIC CAISSONS--TUNNELS--THE BEACH TUNNEL SHIELD
--SUEZ CANAL--DREDGES--THE LIDGERWOOD CABLEWAY--CANAL LOCKS--
ARTESIAN WELLS--COMPRESSED AIR ROCK DRILLS--BLASTING--MISSISSIPPI
JETTIES--IRON AND STEEL BUILDINGS--EIFFEL TOWER--WASHINGTON’S
MONUMENT--THE UNITED STATES CAPITOL.
Almost entirely of an outdoor character, and necessarily on public
exhibition, the engineering achievements of the Nineteenth Century have
always been conspicuously in evidence, challenging the admiration of the
public eye. They represent man’s attack upon the obstacles presented by
nature to his irrepressible spirit of progress. Difficulties apparently
insuperable have confronted him, only to melt away under his persistent
genius until nothing seems impossible. He has connected continents with
the telegraph, has crosshatched the land with railroads, penetrated the
bowels of the earth with artesian wells, opened communication between
oceans with the Suez Canal, reclaimed territory from the sea in Holland,
pierced mountain ranges with tunnels, drained marshes, irrigated
deserts, reared lofty structures of masonry and steel, spanned waters
with magnificent bridges, opened channel-ways to the sea, built beacons
for the mariner, and breakwaters for the storm beaten ship.
Probably the most important branch of engineering work is railroad
construction, already considered under steam railways. Closely related
to the railroad, however, is bridge building, and many of these noble
structures hang between heaven and earth, conspicuous monuments of the
engineer’s skill.
[Illustration: FIG. 228.--THE FORTH BRIDGE. LARGEST VIADUCT IN THE
WORLD. FROM A PHOTOGRAPH WHEN IN PROCESS OF CONSTRUCTION. LENGTH, 8,290
FEET; HEIGHT ABOVE WATER, 361 FEET; MAIN SPANS, 1,710 FEET LONG, 150
FEET HIGH.]
_The Forth Bridge._--This massive structure, of the cantilever type, is
shown in Fig. 228. It was begun in 1882 and finished in 1890, and is the
largest and most costly viaduct in the world. It is built across the
Firth of Forth, and is the most important link in the direct railway
communication of the North British Railway, and associated roads,
between Edinburgh on the one side, and Perth and Dundee on the other.
The total length of the viaduct is 8,296 feet, or nearly 1⅝ miles. The
extreme height of the structure is 361 feet above the water level, and
the foundations extend 91 feet below the water level. The two main spans
are 1,710 feet, and these both give a clear headway for navigation of
150 feet height. There are over 50,000 tons of steel in the
superstructure, and about 140,000 cubic yards of masonry and concrete in
the foundation piers. The three main piers consist each of a group of
four masonry columns faced with granite, 49 feet in diameter at the top,
and 36 feet high, which rest on solid rock, or on concrete carried down
in most cases by means of caissons of a maximum diameter of 70 feet to
rock or boulder clay.
No intelligent conception of the enormous size of this great structure
can be obtained except by comparison. Estimating from the bottom of the
masonry piers to the towering heights of the cantilevers, it reaches
above the dome of St. Peter’s at Rome, and is only a little short of the
height of the greatest of the pyramids of Egypt. The cost of the bridge
is given as £3,250,000 or nearly $16,000,000.
_The Brooklyn Bridge._--Having for its successful construction and
maintenance the same foundation principle upon which the spider builds
its web, this magnificent bridge of steel wires spans the East River
between New York and Brooklyn, with a total length of 5,989 feet, and in
length of span and cost is second only to the great Forth Bridge. It is
shown in Fig. 229, and among suspension bridges it ranks first. It has a
central span of 1,595½ feet between the two towers, over which the
suspension cables are hung, and has a clear headway beneath of 135 feet.
It has two side spans of 930 feet each between the towers and the shore.
[Illustration: FIG. 229.--THE BROOKLYN BRIDGE. LONGEST SUSPENSION BRIDGE
IN THE WORLD. TOTAL LENGTH, 5,989 FEET; SPAN BETWEEN TOWERS, 1,595 FEET
6 INCHES.]
The suspension towers stand on two piers founded in the river on solid
rock at depths of 78 and 45 feet below high water, and they rise 277
feet above the same level. There are four suspension cables 15½ inches
in diameter, each composed of 5,282 galvanized steel wires, placed side
by side, without any twist, and arranged in groups of 19 strands bound
up with wire. These cables have a dip in the center of the large span of
128 feet, rest on movable saddles on the top of the towers to allow for
slight movement of the cables due to expansion and contraction, and are
held down at the shore ends by massive anchorages of masonry. The bridge
has a width of 85 feet, and has two roadways, two lines of railway, and
a foot way. It was begun in 1876 and opened for traffic in 1883, and its
cost was about $15,000,000. It fulfills a great function for the busy
metropolis, and it hangs in the air a monument in steel wire to the
genius of the Roeblings.
_Masonry Bridges._--The largest and finest single span of masonry in
America, and believed to be the largest in the world, is to be found
about 9 miles northwest of the city of Washington. It is known as the
Washington Aqueduct or Cabin John Bridge, and is seen in Fig. 230. It
extends across the small stream known as Cabin John Creek, and carries
an aqueduct 9 feet in diameter, that supplies the National Capital with
water, its upper surface above the water conduit being formed into a
fine roadway. It is 450 feet long. Its span is 220 feet, the height of
the roadway above the bed of the stream is 100 feet, and the width of
the structure is 20 feet 4 inches. Gen. Montgomery C. Meigs was the
engineer in charge of its construction. It was begun in 1857 and
finished in 1864, with the exception of the parapet walls of the
roadway, which were added in 1872-3. Its cost was $254,000. Only one
other masonry arch has ever been built which equalled this in size. The
Trezzo Bridge, built in the fourteenth century, over the Adda in North
Italy, and subsequently destroyed, is said to have had a span of 251
feet, but the Washington Aqueduct Bridge at Cabin John is a noble work
in masonry, and when standing beneath its majestic sweep, and viewing
the regular courses of masonry hanging nearly a hundred feet high in the
air, and springing more than a hundred feet from the embankment upon
either side, one loses sight of the principles of the arch, and the
fear that the mass may fall upon him gives way to the impression that
nature has bowed to the genius of man, and suspended the law of gravity.
[Illustration: FIG. 230.--CABIN JOHN BRIDGE, NEAR WASHINGTON, D. C.
LARGEST MASONRY ARCH IN THE WORLD. LENGTH, 450 FEET; SPAN OF ARCH, 220
FEET; HEIGHT, 100 FEET.]
Among the patents granted for bridges the most important are those
relating to the cantilever type, among which may be mentioned those to
Bender, Latrobe, and Smith, No. 141,310, July 29, 1873; Eads, No.
142,378 to 142,382, September 2, 1873, and Clarke, No. 504,559,
September 5, 1893.
_Caissons._--For submarine explorations the ancient diving bell, which
was said to have been used more than 2,000 years ago, has given place to
diving armor, while for more extensive local work the pneumatic caisson
is employed. The latter was invented by M. Triger, a French engineer, in
1841. An early example of it is also given in Cochrane’s British patent
No. 3,226, of 1861. It consists of a vertical cylinder divided into
compartments, its lower open end resting on the river bottom. Compressed
air forced into the lower compartment forces the water back, while the
men are at work, the intermediate chamber forming an air lock, by which
entrance to, or egress from, the lower working chamber is obtained. The
pneumatic caissons of Eads (patents Nos. 123,002, January 23, 1872, and
123,685, February 13, 1872) and Flad (patent No. 303,830, August 19,
1884) are modern applications of the same principle. The sinking of
shafts through quicksand, by artificially freezing the same and then
treating it as solid material, is an ingenious modern method shown in
patents to Poetsch, No. 300,891, June 24, 1884; and Smith, No. 371,389,
October 11, 1887.
_Tunnels._--Less conspicuous than bridges, by virtue of their
underground character, but none the less important, are these mole-like
means of communication. Especially difficult of construction for the
reason that the nature of the soil or rock is largely unknown, and for
the reason also that the work may have to encounter faults in rocks, and
springs or quicksands in the earth; nevertheless the demands of the
railroads for shortening the distance of travel and economizing time
have stimulated the engineer to expend millions of dollars in piercing
the earth with these great underground passageways.
_The Mont Cenis Tunnel_ was constructed to establish railway
communication between France and Italy through the Alps. It was begun in
1857, and after having been in progress of construction for thirteen
years, was opened for traffic in 1871. This tunnel was commenced by hand
borings, being for the most part through solid rock, and its progress up
to 1862 was so slow that it was estimated that thirty years would be
required for its construction. Its earlier completion was due to the
introduction of rock drills operated by compressed air, which trebled
the rate of advance, and which device made a new epoch in all
rock-boring and mining operations. This tunnel was cut from both ends at
the same time, and so accurate were the surveys in establishing the
alignment of the two headings through the mountain mass, that, although
the tunnel was more than 7½ miles long, when the two headings came
together in the middle, only a difference of one foot in level existed
between them. When it is remembered that most of the 7½ miles of tunnel
was cut through solid rock, by boring and blasting, the immensity of the
undertaking can be appreciated. As completed the tunnel is 8 miles long,
and wide enough for a double track railway.
_The St. Gothard Tunnel_ is another tunnel through the Alps, which
involved even a longer and deeper cut through the mountains than the
Mont Cenis Tunnel. This is 9¼ miles long, and it was begun in 1872, the
headings joined in 1880, and the tunnel opened for traffic in 1882.
Although by far the largest undertaking yet made, the improvement in
rock-boring machinery enabled it to be constructed much more rapidly and
at less expense.
The Arlberg is still another Alpine tunnel. It is 6½ miles long, was
commenced in 1880, and opened for traffic in 1884.
Tunneling under rivers presents many more difficulties than driving
through the hardest rock. This is so by reason of the inflow of water.
Among successful tunnels of this kind may be named the Mersey and Severn
tunnels in England, opened in 1886, and the St. Clair tunnel between the
United States and Canada. The histories of the abandoned Detroit and
Hudson river tunnels are object lessons of the difficulties encountered
in this class of work.
An important engineering invention for tunneling through silt or soft
soil is the so-called “shield.” This was first employed by the engineer
Brunel in the construction of the Thames tunnel, which was begun in 1825
and opened as a thoroughfare in 1843. The shield, as now used, is a sort
of a cylinder or sleeve as large as the tunnel, which sleeve, as the
excavation proceeds in front of it, is forced ahead to act both as a
ring-shaped cutter and a protection to the workmen, its advance being
effected by powerful hydraulic jacks or screws which find a back bearing
against the completed wall of the tunnel. As the digging proceeds the
shield is advanced, and a section of tunnel is built behind it which, in
turn, furnishes a bearing for the jacks in the further advance of the
shield.
This latter improvement was the invention of the late Alfred E. Beach,
of the _Scientific American_, and was covered by him in patent No.
91,071, June 8, 1869, and was used in driving the experimental pneumatic
subway constructed by him under Broadway, New York, in 1868-9, and also
in the St. Clair River tunnel and the unfinished Hudson River tunnel and
other works.
Subsequent improvements made upon the shield by J. H. Greathead of
England and covered by him in United States patents Nos. 360,959, April
12, 1887; and 432,871, July 22, 1890, have greatly added to the value
and efficiency of this device, and made it one of the leading
instrumentalities in tunnel construction.
_Suez Canal._--It is said that the undertaking of connecting the
Mediterranean and Red Seas was considered as long ago as the time of
Herodotus, and a small channel appears to have been opened twenty-five
centuries ago, but was subsequently abandoned. In 1847 the subject was
again taken up for serious consideration, the work begun in 1860, and
finished in 1869, at a cost of £20,500,000, or more than a hundred
million dollars. The canal starts at Port Said, on the Mediterranean, a
view of which with its ships of all nations and the canal reaching far
away in the distance is seen in Fig. 231. The canal extends nearly due
south to Suez on the Red Sea, a distance of about 100 miles, through
barren wastes of sand and an occasional lake. It was originally formed
with a bottom width of 72 feet, spreading out to 196 to 328 feet at the
top, and of a depth of 26 feet, but has since been increased in
transverse dimension to accommodate the great increase in travel.
[Illustration: FIG. 231.--PORT SAID ENTRANCE TO SUEZ CANAL, SHOWING
HARBOR WITH SHIPS OF ALL NATIONS, AND THE CANAL REACHING AWAY IN THE
DISTANCE.]
Sixty great dredges were employed on the work, and the dredged material
was discharged in chutes on to the bank. The canal was the work of M. De
Lesseps, the eminent French engineer, and has proved a great success
from both an engineering and financial standpoint. The stock is mainly
held in England, having been bought from the Khedive of Egypt. In 1898
the ships passing through the canal during the year reached the
remarkable number of 3,503. The rate of tolls is 10 francs (about $2)
per net ton. The gross tonnage of ships passing through in 1898 was
12,962,632, the net tonnage 9,238,603. The total receipts for the year
were 87,906,255 francs (about $17,500,000), and the net profit
63,441,987 francs (about $12,500,000). An average size ocean liner pays
about $5,000 for the privilege of sailing through this great ditch.
Admiral Dewey’s ship, the “Olympia,” returning from the Philippines,
paid for her toll $3,516.04, and the “Chicago,” $3,165.95. Going the
other way, our supply ship “Alexander” paid $4,107.99, while the
“Glacier” paid $5,052.38. Ships making the passage through the canal
move slowly on account of the washing of the banks, about 22 hours
being required, but the shortening of the travel of ships going east and
west, and the saving of life, property, and time, involved in avoiding
the circuitous and stormy passage around the Cape of Good Hope, has been
of incalculable benefit to the world.
[Illustration: FIG. 232.--HERCULES DREDGER.]
With the construction of canals and harbors, great improvements have
been made in dredges. Some of these are of the clam-shell type, some
employ the scoop and lever, others an endless series of buckets. An
example of the latter, used on the Panama Canal, is seen in Fig. 232.
Still another form, and the most recent if not the most important is the
hydraulic dredger, which, by rotating cutters, stirs and cuts the mud
and silt, and by powerful suction pumps and immense tubes draws up the
semi-fluid mass and sends it to suitable points of discharge. The best
known of the latter type is the Bowers hydraulic dredge, covered by many
patents, of which Nos. 318,859 and 318,860, May 26, 1885; 388,253,
August 21, 1888; and 484,763, October 18, 1892, are the most important.
For surface excavations in solid earth the Lidgerwood Cableway is an
important and labor saving device. A track cable is stretched from two
distant towers, and a bucket holding well on to a ton of earth is made
to travel on a trolley running on said cable track, rising at one end
out of the excavation, and dumping at the other end to fill in the
excavation as the cutting progresses, all in a continuous and
economical manner. This device is made under the patent to M. W. Locke,
No. 295,776, March 25, 1884, and comprehends many subsequent
improvements patented by Miller, Delaney, North and others. The Chicago
Drainage Canal is a work just completed, which largely employed these
devices. This canal was designed to connect the Chicago River with the
Mississippi River, so as to send the sewage of Chicago down the
Mississippi instead of into Lake Michigan. Although it cost $33,000,000
and required seven years for completion, the labor-saving cableways
greatly cheapened its cost and shortened the time of its construction.
Among the leading inventions relating to canal construction may be
mentioned the bear-trap canal-lock gate (patents Nos. 229,682, 236,488
and 552,063), and the Dutton pneumatic lift locks. The latter provide
ease and rapidity of action by a principle of balancing locks in pairs,
and are covered by his patent No. 457,528, August 11, 1891, and others
of subsequent date.
_Artesian Wells_ represent an important branch of engineering work, and
they are so called from the province of Artois, in France, where they
have for a long time been in use. Extending several thousand feet into
the subterranean chambers of the earth, they have brought abundant water
supply to the surface all over the world, from the desert sands of
Sahara to the hotels of the modern city; they have contributed oil and
gas in incredible quantities to supply light and heat, and have made
valuable additions to the salt supply of the world.
They are driven by reciprocating a ponderous chisel-shaped drill within
an iron tube, six inches more or less in diameter, which is built up in
sections, and moved down as the cutting descends. The drill is
reciprocated by a suspending rope from machinery in a derrick, and in
order to give a hammer-like blow to the chisel a pair of ponderous iron
links coupled together like those of a chain, and called a “_drill jar_”
connect the drill to the rope. As the sections of the link slide over
each other they come together with a hammer blow at the moment of
lifting that dislodges the drill from the rock, and on the descending
movement they come together with a hammering blow immediately after the
drill touches the rock to drive it into the same. The first United
States patent for a drill jar is that to Morris, No. 2,243, September 4,
1841. When an oil well ceases to flow, it is rejuvenated by being
“shot,” which is quite contrary to the ordinary conception of prolonging
life. For this purpose a dynamite cartridge is exploded at the lower end
of the well, which shatters the rock, and, in opening up new channels
of flow for the oil, renews the yield. Many patented inventions have
been made in the field of well boring, and the discovery of coal oil in
the United States in 1859 has developed a great industry and built up
enormous fortunes. The amount of petroleum produced in the United States
in 1896 was 60,960,361 barrels, the largest yield on record. In 1897 the
amount was 60,568,081 barrels.
Of less consequence than the artesian well, but finding many useful
applications, is the drive well. A metal tube with a perforated lower
end is driven down by hammers into the ground, and furnishes a quick and
cheap source of water supply. This was invented by Col. Green in 1861,
in meeting the necessities of his military camp during the civil war,
and was patented by him January 14, 1868, No. 73,425.
_Rock Drills._--In mining and tunneling through rock, the rock drill has
been the implement of paramount importance and utility. For boring by
rotary action the diamond drill is most effective. This uses bits set
with diamonds which, by their extreme hardness, cut through the most
refractory rock with great rapidity. It was invented by Hermann and
patented by him in France, June 3, 1854.
More important, however, is the compressed air rock drill, in which a
piston has the drill bit directly on its piston rod and cuts by a
reciprocating action. The piston is actuated by compressed air admitted
alternately to its opposite sides in an automatic manner by valves. The
compressed air conveyed to the drill in the tunnel or mine not only
operates the drill, but helps to ventilate the tunnel. As early as 1849
Clarke and Motley, in England, invented a machine drill, and in 1851
Fowle devised a similar machine, having the drill attached directly to
the piston cross head. The Hoosac and Mont Cenis tunnels greatly
stimulated invention in this field, and among the notable drills of this
class may be named the Burleigh, Ingersoll, and Sergeant. The Burleigh
drill was brought out in 1866, and was covered by patents Nos. 52,960,
52,961 and 59,960 of that year, and 113,850 of 1871, and the Ingersoll
drill, by patents No. 112,254, and No. 120,279, of 1871.
[Illustration: FIG. 233.--BLOWING UP FLOOD ROCK.]
_Blasting._--The discovery of nitro-glycerine in 1846, followed by its
convenient commercial preparation in the form of dynamite, gave a great
impetus to blasting. Notable as the largest operation of the kind in the
century is the blowing up of Flood Rock, in the path of commerce between
New York City and Long Island Sound. The dangerous character of this and
other rocks in this vicinity gave long ago to this channel the
significant name of Hell Gate. The undermining of the rocks by shafts
and galleries is seen in Fig. 233, and the final blowing up of the same
in a single blast was the culmination of a series of similar operations
at this point tending to safer navigation. On October 10, 1885, 40,000
cartridges, containing 75,000 pounds of dynamite and 240,000 pounds of
_rack-a-rock_, were, by the touching of a button and the closing of an
electric circuit, simultaneously exploded. In the twinkling of an eye
nine acres of solid rock were shattered into fragments by the prodigious
force, and a vast upheaval of water 1,400 feet long, 800 feet wide, and
200 feet high, sprang into the air in tangled and gigantic fountains. As
the termination of the most stupendous piece of engineering of the kind
the world has ever seen, and with spectacular features fitting the
enormous expense of $1,000,000, which the work cost, this final scene
put an end to the menaces of Flood Rock, and wiped out of existence the
worst dangers of Hell Gate.
[Illustration: FIG. 234.--CROSS SECTION MISSISSIPPI JETTIES.]
_Mississippi Jetties._--The broad bar and shallow waters at the mouth of
the Mississippi involved such an obstruction to commerce that in 1872 it
received the attention of Congress, resulting in the building, by Capt.
Eads, of the celebrated jetties. They were begun in 1875 and finished in
1879, and cost $5,250,000. The channel obtained was 30 feet deep and 200
feet wide. Its construction involved the building across the bar and out
into the Gulf of Mexico two long reaches of parallel embankments, called
jetties. This was effected by sinking mattresses of willow branches
bound together and weighted with stone. These were laid in four layers,
and when submerged, and resting upon the bottom, were covered with a
layer of loose stone, and this in turn was surmounted with a capping of
concrete blocks, as seen in cross section in Fig. 234. These jetties so
concentrated the flow of waters into a narrow channel as to cause its
increased velocity to wash out the mud and silt and deepen the channel.
The immensity of the work may be measured by the quantity of material
used in its construction, which included 6,000,000 cubic yards of willow
mattresses, 1,000,000 cubic yards of stone, 13,000,000 feet (board
measure) of lumber, and 8,000,000 cubic yards of concrete. The
mattresses were laid 35 to 50 feet wide at the bottom, which width was
considerably increased by the superimposed layer of stone, and the
jetties extended 2¼ miles into the sea. Their influence upon commerce is
indicated by the fact that before their construction the annual grain
export from New Orleans was less than half a million bushels, and in
1880, the year following their completion, it was increased to
14,000,000 bushels.
[Illustration: FIG. 235.--INTERIOR CONSTRUCTION MODERN STEEL BUILDING.]
_High Buildings._--A distinct feature of modern architecture is the
enormously tall steel frame building known as the “sky scraper.” The
increasing value of city lots first brought about the vertical extension
of buildings to a greater number of stories, and the necessity for
making them fireproof, coupled with the desire to avoid loss of interior
space, due to thick walls at the base, made a demand for a different
style of architecture. To meet this a skeleton frame of steel is bolted
together in unitary structure, the floors being all carried on the steel
frame, and the outer masonry walls being relatively thin, and carrying
only their own weight. In Fig. 235 is shown an example of the interior
structure of such a building. The vertical columns are erected upon a
very firm foundation, and to them are bolted, on the floor levels,
horizontal I-beams and girders, stayed by tie rods, which I-beams
receive between them hollow fireproof tile to form the floor. The outer
masonry walls are built around the skeleton frame, as seen in Fig. 236,
and the details of connections for the floor members appear in Fig. 237.
[Illustration: FIG. 236.--ENCLOSURE OF STEEL FRAME BY MASONRY.]
[Illustration: FIG. 237.--DETAILS OF INTERNAL CONSTRUCTION.]
The construction of iron buildings began about the middle of the
century. In 1845 Peter Cooper erected the largest rolling mill at that
time in the United States for making railroad iron, and at this mill
wrought iron beams for fireproof buildings were first rolled. In the
building of the Cooper Institute in New York City in 1857 he was the
first to employ such beams with brick arches to support the floors. The
unifying of the iron work into an integral skeleton frame, for relieving
the side walls of the weight of the floors is, however, a comparatively
recent development, and this has so raised the height of the modern
office building as to cause it to impress the observer as an obelisk
rather than a place of habitation. An earthquake-proof steel palace for
the Crown Prince of Japan is one of the modern applications of steel in
architecture. It is being built by American engineers, and is to cost
$3,000,000.
[Illustration: FIG. 238.--THE EIFFEL TOWER. HEIGHT, 984 FEET. TALLEST
STRUCTURE IN THE WORLD.]
[Illustration: FIG. 239.--WASHINGTON’S MONUMENT. HEIGHT 555 FEET, 5½
INCHES. HIGHEST MASONRY STRUCTURE IN THE WORLD.]
_Eiffel Tower._--Loftiest among the high structures of the world, and
significant as indicating the possibilities of iron construction, the
Eiffel Tower of the Paris Exposition of 1889 was a distinct achievement
in the engineering world. It is seen in Fig. 238. It is 984 feet high,
and 410 feet across its foundation, and has a supporting base of four
independent lattice work piers. In the top was constructed a scientific
laboratory surmounted by a lantern containing a powerful electric light.
The total weight of iron in the structure is about 7,000 tons, the
weight of the rivets alone being 450 tons, and the total number of them
2,500,000. The level of the first story is marked by a bold frieze, on
the panels of which, around all four faces, were inscribed in gigantic
letters of gold the names of the famous Frenchmen of the century. The
summit of the tower was reached by staircases containing 1,793 steps,
and by hydraulic elevators running in four stages. The cost of this
structure was nearly $1,000,000.
_Washington’s Monument._--Next in height to the Eiffel Tower, and being,
in fact, the tallest masonry structure in the world, this noble obelisk,
by its simplicity, boldness and solidity, challenges the admiration of
every visitor, and gratifies the pride of every patriot. It is seen in
Fig. 239, and is 555 feet 5½ inches high, 55 feet square at the base,
and 34 feet square at the top. The walls are 15 feet thick at the base,
and 18 inches at the top, and its summit is reached by an internal
winding staircase and a central elevator. At the height of 504 feet the
walls are pierced with port holes, from which a magnificent view is had
of the capital city and surrounding country. The summit is crowned with
a cap of aluminum, inscribed _Laus Deo_. The foundation of rock and
cement is 36 feet deep and 126 feet square, and the total cost of the
monument was $1,300,000. The corner stone was laid in 1848. In 1855 the
work was discontinued at the height of 152 feet, from lack of funds. In
1878 it was resumed by appropriation from Congress, and completed and
dedicated in 1885, under the direction of Col. Thomas L. Casey, of the
United States Corps of Engineers.
_The Capitol Building._--Representing the heart of the great American
Republic, and overlooking its Capital City, this grand building, shown
in Fig. 240, is a poem in architecture. Massive, symmetrical and
harmonious, its highest point reaches 307½ feet above the plaza on the
east. It is 751 feet 4 inches long, 350 feet wide, and the walls of the
building proper cover 3½ acres. Crowning the center of the building is
the imposing dome of iron, surmounted by a lantern, and above this is
the bronze statue of Freedom, 19 feet 6 inches high, and weighing
14,985 pounds, the latter being set in place December 2, 1863. The dome
is 135 feet 5 inches in diameter at the base, and the open space of the
rotunda within is 96 feet in diameter and 180 feet high.
The corner stone of the original building was laid in 1793 by
Washington. The first session of Congress held there was in 1800, while
the building was still incomplete. The original building was finished
in 1811. In 1814 it was partly burned by the British. In 1815
reconstruction was begun, and completed in 1827. In 1850 Congress passed
an act authorizing the extension of the Capitol, which resulted in the
building of the north and south wings, containing the present Senate
Chamber and Hall of the House of Representatives. The corner stones of
the extension were laid by President Fillmore in 1851, Daniel Webster
being the orator of the occasion, and the wings were finished in 1867.
Since this time handsome additions in the shape of marble terraces on
the west front have added greatly to the beauty and apparent size of the
building.
[Illustration: FIG. 240.--THE UNITED STATES CAPITOL. LENGTH, 751⅓ FEET;
WIDTH, 350 FEET; HEIGHT, 307½ FEET; BUILDING COVERS 3½ ACRES.]
It is not possible to give anything like an adequate review of the
engineering inventions and achievements of the Nineteenth Century in a
single chapter, and only the most noteworthy have been mentioned. The
modern life of the world, however, has been replete with the resourceful
expedients of the engineer, and the ingenious instrumentalities invented
by him to carry out his plans. There have been about 1,000 patents
granted for bridges, about 2,500 for excavating apparatus, and about
1,500 for hydraulic engineering. In mining the safety-lamp of Sir
Humphrey Davy, in 1815, has been followed by stamp mills, rock-drills,
derricks, and hoisting and lowering apparatus, and lately by hydraulic
mining apparatus, by which a stream of water under high pressure is made
to wash away a mountain side. Apparatus for loading and unloading,
pneumatic conveyors, great systems of irrigation, lighthouses,
breakwaters, pile drivers, dry-docks, ship railways, road-making
apparatus, fire escapes, fireproof buildings, water towers, and
filtration plants have been devised, constructed and utilized. Many
gigantic schemes, already begun, still await successful completion,
among which may be named the draining of the Zuyder Zee, the Siberian
railway, the Panama and Nicaraguan Canals, the Simplon tunnel, the new
East River Bridge, and the Rapid Transit Tunnel under New York City;
while a bridge or tunnel across the English Channel, a ship canal for
France, connecting the Bay of Biscay with the Mediterranean, a tunnel
under the Straits of Gibraltar, and a ship canal connecting the great
lakes with the Gulf of Mexico, are among the possible achievements which
challenge the engineer of the Twentieth Century.