the merits of the American swivelling truck or bogie. In the
article on Railways in the last edition of the "Encyclopædia
Britannica," speaking of locomotives, the author of the article,
who is an English engineer of high authority, says: "American
practice, many years since, arrived at two leading types of
locomotive for passenger, and for goods traffic. The passenger
locomotive has eight wheels, of which four in front are framed in
a bogie, and the four wheels behind are coupled drivers. _This is
the type to which English practice has been approximating._" The
italics are ours.
[2] The statistics of ten leading English and ten leading American
lines, given by Dorsey, show the following results: 1. The cost
per year of the rations, wages, fuel of an American locomotive
is $5,590; of an English locomotive, $3,080. 2. Average yearly
number of train-miles run by American locomotive, 23,928; English
locomotive, 17,539. 3. Yearly earnings: American locomotive,
$14,860; English locomotive, $10,940, although the English freight
charges are much greater than those of the United States.
[3] The writer has obtained many of the statistics used in this
article from A. M. Wellington's "Economic Theory of Railway
Location," a perfect mine of valuable information upon all such
matters.
[4] The amount of permanent wood and iron truss bridges, and of
temporary wooden trestles on the Chicago, Milwaukee, and St. Paul
is as follows:
Truss bridges, 700 spans, average 93 feet, 12-4/5 miles.
Trestle " 7,196 " " 77 " 103-1/10 "
------ --------
Total, 7,896 115-9/10 "
The approximate total number of bridges in the United States was in
1888:
Iron and wood truss bridges, 61,562 spans, 1,086 miles.
Wooden trestles, 147,187 2,127 "
-------- ------
Total, 208,749 3,213 "
Probably three-fourths of the truss bridges are now of iron
or steel, and may be considered perfectly safe so long as the
trains remain upon the rails and do not strike the side trusses.
The wooden trestles are a constant source of danger from decay
or burning or from derailed trains, and should be replaced by
permanent structures as fast as time and money will allow.
[5] See following article on "Feats of Railroad Engineering," page
86.
[6] For fuller description of work in a caisson see "Feats of
Railway Engineering," page 69.
[7] See "Feats of Railway Engineering," page 55.
FEATS OF RAILWAY ENGINEERING.
BY JOHN BOGART.
Development of the Rail--Problems for the Engineer--How
Heights are Climbed--The Use of Trestles--Construction on a
Mountain Side--Engineering on Rope Ladders--Through the Portals
of a Cañon--Feats on the Oroya Railroad, Peru--Nochistongo
Cut--Rack Rails for Heavy Grades--Difficulties in Tunnel
Construction--Bridge Foundations--Cribs and Pneumatic
Caissons--How Men work under Water--The Construction of Stone
Arches--Wood and Iron in Bridge-building--Great Suspension
Bridges--The Niagara Cantilever and the enormous Forth
Bridge--Elevated and Underground Roads--Responsibilities of the
Civil Engineer.
There are one hundred and fifty thousand miles of railway in the
United States: three hundred thousand miles of rails--in length
enough to make twelve steel girdles for the earth's circumference.
This enormous length of rail is wonderful--we do not really grasp
its significance. But the rail itself, the little section of steel,
is an engineering feat. The change of its form from the curious and
clumsy iron pear-head of thirty years ago to the present refined
section of steel is a scientific development. It is now a beam
whose every dimension and curve and angle are exactly suited to the
tremendous work it has to do. The loads it carries are enormous,
the blows it receives are heavy and constant, but it carries the
loads and bears the blows and does its duty. The locomotive and the
modern passenger and freight cars are great achievements; and so is
the little rail which carries them all.
The railway to-day is one of the matter-of-fact associations of
our active life. We use it so constantly that it requires some
little effort to think of it as a wonderful thing; a creation
of man's ingenuity, which did not exist when our grandfathers
were young. Its long bridges, high viaducts, and dark tunnels may
be remarked and remembered by the traveller, but the narrow way
of steel, the road itself, seems but a simple work. And yet the
problem of location, the determination, foot by foot and mile by
mile, of where the line must go, calls in its successful solution
for the highest skill of the engineer, whose profession before the
railway was created hardly existed at all. Locomotives now climb
heights which a few years ago no vehicle on wheels could ascend.
The writer, with some engineer friends, was in the mountains
of Colorado during the summer of 1887, and saw a train of very
intelligent donkeys loaded with ore from the mines, to which no
access could be had but by those sure-footed beasts. Within a year
one of that party of engineers had located and was building a
railway to those very mines. No heights seem too great to-day, no
valleys too deep, no cañons too forbidding, no streams too wide; if
commerce demands, the engineer will respond and the railways will
be built.
The location of the line of a railway through difficult country
requires the trained judgment of an engineer of special experience,
and the most difficult country is not by any means that which might
at first be supposed. A line through a narrow pass almost locates
itself. But the approach to a summit through rolling country is
often a serious problem. The rate of grade must be kept as light
as possible, and must never exceed the prescribed maximum. The
cuttings and the embankments must be as shallow as they can be
made--the quantities of material taken from the excavations should
be just about enough to make adjacent embankments. The curves must
be few and of light radius--never exceeding an arranged limit.
The line must always be kept as direct as these considerations
will allow--so that the final location will give the shortest
practicable economical distance from point to point. Many a mile
of railway over which we travel now at the highest speed has been
a weary problem to the engineer of location, and he has often
accomplished a really greater success by securing a line which
seems to closely fit the country over which it runs without marking
itself sharply upon nature's moulding, than if he had with apparent
boldness cut deep into the hills and raised embankments and
viaducts high over lowlands and valleys.
[Illustration: View Down the Blue from Rocky Point, Denver, South
Park and Pacific Railroad; showing successive tiers of railway.]
But roads must run through many regions where very different
measures must be taken to secure a location practicable for
traffic. For instance, a line at a high elevation approaches a wide
valley which it must cross. The rate of descent is fixed by the
established maximum grade, and the sides of the valley are much
steeper than that rate. Then the engineer must gain distance--that
is to say, he must make the line long enough to overcome the
vertical height. This can often be accomplished by carrying it
up the valley on one side and down on the other. Tributary
valleys can be made use of if necessary, and the desired crossing
thus accomplished. But at times even these expedients will not
suffice. Then the line is made to bend upon itself and wind down
the hillside upon benches cut into the earth, or rock, curving at
points where nature affords any sort of opportunity, and reaching
the valley at last in long convolutions like the path of a great
serpent on the mountain side. These lines often show several tiers
of railway, one directly above the other, as may be seen in the
illustrations on pages 49 and 51.
The long trestle shown in the illustration opposite is an
example of an expedient often of the greatest service in railway
construction. These trestles are built of wood, simply but strongly
framed together, and are entirely effective for the transport of
traffic for a number of years. Then they must be renewed, or, what
is better, be replaced by embankment, which can be gradually made
by depositing the material from cars on the trestle itself. The
trestle illustrated is interesting as conforming to the curve of
the line, which in that country, the mountains of Colorado, was
probably a necessity of location.
* * * * *
Where the direct turning of a line upon itself may not be
necessary, there may and often must be bold work done in the
construction of the road upon a mountain side. It must be supported
where necessary by walls built up from suitable foundations,
often only secured at a great depth below the grade of the road.
Projecting points of rock must be cut through, and any practicable
natural shelf or favorable formation must be made use of, as in the
picture on page 61. In some of the mountain locations, galleries
have been cut directly into the rock, the cliff overhanging the
roadway, and the line being carried in a horizontal cut or niche in
the solid wall.
[Illustration: Loop and Great Trestle near Hagerman's, on the
Colorado Midland Railway.]
The Oroya and the Chimbote railways in South America demanded
constant locations of this character. At many points it was
necessary to suspend the persons making the preliminary
measurements from the cliff above. The engineer who made these
locations told the writer that on the Oroya line the galleries
were often from 100 to 400 feet above the base of the cliff, and
were generally reached from above. Rope ladders were used to great
advantage. One 64 feet long and one 106 feet long covered the
usual practice, and were sometimes spliced together. The side
ropes were ¾ and 1¼ inches in diameter, and the rounds of wood 1¼
inches in diameter, and 16 inches and 24 inches long. These were
notched at the ends and passed through the ropes, to which they
were afterward lashed. These ladders could be rolled up and carried
about on donkeys or mules. When swung over the side of a cliff
and secured at the top, and when practicable at the bottom, they
formed a very useful instrument in location and construction. For
simple examination of the cliff, and for rough or broken slopes
not exceeding 70 to 80 degrees, an active fellow would, after some
experience, walk up and down such a slope simply grasping the
rope in his hands. If required to do any work he would secure the
rope about his body, or wind it around his arm, leaving his hands
comparatively free for light work.
The boatswain's chair--consisting of a wooden seat 6 inches wide
and two feet long, through the ends of which pass the side ropes,
looped at the top, and having their ends knotted--is a particularly
convenient seat to use where cliffs overhang to a slight degree.
The riggers were generally Portuguese sailors, who seemed to have
more agility and less fear than any other men to be found. At
Cuesta Blanca, on the Oroya, a prominent discoloration on the cliff
served as a triangulation point for locating the chief gallery.
Men were swung over the side of the cliff in a cage about 2½ feet
by 6 feet, open at the top and on the side next the rock. This
was a peculiar cliff about 1,000 feet high, rising from the river
at a general slope of about 70 degrees. The grade line of the
road was 420 feet above the river. The Chileno miners climbed up
a rope ladder to a large seam near the grade, where they lived;
provisions, water, etc., being hoisted up to them. The first men
sent over the cliff to begin the preliminary work were lowered in
a cage and took their dinners with them, for fear they would not
return to the work, and that unless a genuine start was made others
could not be induced to take their places. It is safe to say that
80 per cent. of the sixty odd tunnels on the Oroya and the seven
tunnels on the Chimbote lines were located and constructed on lines
determined by triangulation, and the results were so satisfactory
that the method may be depended upon as the best system for
determining topographical data or for locating and constructing the
lines in any similar locality.
[Illustration: Denver and Rio Grande Railway Entering the Portals
of the Grand River Cañon, Col.]
Where the rocks close in together, as in some of the cañons of our
Southwest, the railway curves about them and finds its way often
where one would hardly suppose a decent wagon road could be built.
The portals of the Grand River Cañon, as here shown, present such a
line, passing through narrow gateways of rock rising precipitously
on either side to enormous heights.
When such a cañon or a narrow valley directly crosses the line of
the road, it must be spanned by a bridge or viaduct. The Kentucky
River Bridge, shown below, is an instance. The Verrugas Bridge, on
the Lima and Oroya Railroad in Peru, is another. This bridge is at
an elevation of 5,836 feet above sea-level. It crosses a ravine at
the bottom of which is a small stream. The bridge is 575 feet long,
in four spans, and is supported by iron towers, the central one
of which is 252 feet in height. The construction was accomplished
entirely from above, the material all having been delivered at the
top of the ravine, and the erection was made by lowering each piece
to its position. This was done by the use of two wire-rope cables,
suspended across the ravine from temporary towers at each end of
the bridge.
[Illustration: The Kentucky River Cantilever, on the Cincinnati
Southern Railway.]
On the line of the same Oroya Railroad is a striking example of
the difficulties encountered in such mountain country and of
the method by which they have been overcome. A tunnel reaches a
narrow gorge, a truss is thrown across, and the tunnel continued.
Nature's wildest scenery, the deep ravine, the mountain cliffs, and
the graceful truss carrying the locomotive and train safely over
what would seem an impossible pass, here combine to give a vivid
illustration of an engineering feat.
[Illustration: Truss over Ravine, and Tunnel, Oroya Railroad, Peru.]
The location of a part of the Mexican Central Railway through the
cut of Nochistongo is peculiarly interesting. Far underneath the
level of this line of railway there was skilfully constructed,
in 1608, a tunnel which at that period was a very bold piece of
engineering. It was designed to drain the Valley of Mexico, which
has no natural outlet. This tunnel was more than six miles long
and ten feet wide. It was driven through the formation called
_tepetate_, a peculiar earth with strata of sand and marl. It was
finished in eleven months. At first excavated without a lining, it
was afterward faced with masonry. It was not entirely protected
when a great flood came, the dikes above gave way, and the tunnel
became obstructed. The City of Mexico was flooded, and it was
decided that, instead of repairing the tunnel an open cut should be
made. The engineer who had constructed the tunnel, Enrico Martinez,
was put in charge of this enormous undertaking, and others took his
place after his death. The cut is believed to be the largest ever
made in the world. For more than a century the work was continued.
Its greatest depth is now 200 feet. It was cut deeper, but has
partially filled with the washings from the slopes. The cost
was enormous, more than 6,000,000 dollars in silver having been
actually disbursed! Wages for workmen were then from 9 to 12 cents
a day. All convicts sentenced to hard labor were put at work in the
great cut. The loss of life was very great. Writers of the time
state that more than 100,000 Indians perished while engaged in the
work.
[Illustration: The Nochistongo Cut, Mexican Central Railway.]
[Illustration: The Mount Washington Rack Railroad.]
When a line of railway encountered a grade too steep for ascent
by the traction of the locomotive, the earlier engineers adopted
the inclined plane. Such planes were in use at important points
during many years. Notable instances were those by which traffic
was carried across the Alleghany Mountains, connecting on each side
with the Pennsylvania railway lines. These old planes are still
visible from the present Pennsylvania Railroad where it crosses
the summit west of Altoona. The planes were operated by stationary
engines acting upon cables attached to the cars. These cables
passed around drums at the head of the planes, the weight of the
cars on one track partially balancing those on the other. Similar
planes were in use also at Albany, Schenectady, and other places.
[Illustration: Trestle on Portland and Ogdensburg Railway, Crawford
Notch, White Mountains.]
Another effective expedient is the central rack rail. No better
or more successful example of this method of construction can be
given than the Mount Washington Railway, illustrated above. The
road was completed in 1869. Its length is 3-1/3 miles and its
total rise 3,625 feet. Its steepest grade is about 1 foot rise in
every 3 feet in length; the average grade is 1 in 4. It is built
of heavy timber, well bolted to the rock. Low places are spanned
by substantial trestle work. The gauge of the road is 4 feet 7½
inches, and it is provided with the two ordinary rails and also the
central rack rail, which is really like an iron ladder, the sides
being of angle iron and the cross-pieces of round iron 1½ inches in
diameter and 4 inches apart. Into these plays the central cog-wheel
on the locomotive, which thus climbs this iron ladder with entire
safety. Very complete arrangements are made to control the descent
of the train in case of accident to the machinery. The locomotive
is always below the train, and pushes it up the mountain. Many
thousands of passengers have been transported every year without
accident.
[Illustration: A Series of Tunnels.]
The rack railroad ascending the Righi, in Switzerland, was
copied after the Mount Washington line. Some improvements in the
construction of the rack rail and attachments have been introduced
upon mountain roads in Germany, and this system seems very
advantageous for use in exceptionally steep locations.
* * * * *
When a line of railway meets in its course a barrier of rock, it
is often best to cut directly through. If the grade is not too
far below the surface of the rock, the cut is made like a great
trench with the sides as steep as the nature of the material will
allow. Very deep cuts are, however, not desirable. The rains
bring down upon their slopes the softer material from above, and
the frost detaches pieces of rock which, falling, may result in
serious accidents to trains. Snow lodges in these deep cuts, at
times entirely stopping traffic, as in the blizzard near New York,
in March, 1888. A tunnel, therefore, while perhaps greater in
first cost than a moderately deep cut, is really often the more
economical expedient.
[Illustration: Tunnel at the Foot of Mount St. Stephen, on the
Canadian Pacific.
(The glacier 8,200 feet above the Railway.)]
[Illustration: Peña de Mora
on the La Guayra and Carácas Railway, Venezuela.]
And here is as good a place, perhaps, as any other in this chapter,
to say that true engineering is the economical adaptation of
the means and opportunities existing, to the end desired. Civil
engineering was defined, by one of the greatest of England's
engineers, as "the art of directing the great sources of
power in nature for the use and convenience of man," and that
definition was adopted as a fundamental idea in the charter of
the English Institution of Civil Engineers. But the development
of engineering-works in America has been effected successfully by
American engineers only because they have appreciated another side
of the problem presented to them. A past president of the American
Society of Civil Engineers, a man of rare judgment and remarkable
executive ability, the late Ashbel Welch, said, in discussing a
great undertaking proposed by an eminent Frenchman: "That is the
best engineering, not which makes the most splendid, or even the
most perfect, work, but that which makes a work that answers the
purpose well, at the least cost." And it may be remarked, as to
the project which he was then discussing, that after a very large
expenditure and an experience of eight years since that discussion,
the plans of the work were modified and the identical suggestions
made by Mr. Welch of a radical economical change were adopted
in 1888.[8] Another eminent American engineer, whose practical
experience has been gained in the construction and engineering
supervision of more than five thousand miles of railway, said,
in his address as President of the American Society of Civil
Engineers: "The high object of our profession is to consider and
determine the most economic use of time, power, and matter."
[Illustration: Perspective View of St. Gothard Spiral Tunnels, in
the Alps.]
That true economy, which finally secures in a completed work the
best results from the investment of capital, in first cost and
continued maintenance, is an essential element in the consideration
of any really great engineering feat.
* * * * *
The difficulties involved in the construction of a tunnel, after
the line and dimensions have been determined, depend generally
upon the nature of the material found as the work advances. Solid
rock presents really the fewest difficulties, but it is seldom
that tunnels of considerable length occur without meeting material
which requires special provision for successful treatment. In some
cases great portions of the rock, where the roof of the tunnel is
to be, press downward with enormous weight, being detached from the
adjacent mass by the occurrence of natural seams.
At other places soft material may be encountered, and the passage
then is attended with great difficulty. Temporary supports,
generally of timber, and of great strength, have often to be used
at every foot of progress to prevent the material from forcing its
way into the excavation already made.
In long tunnels the ventilation is a difficult problem, although
the use of compressed air drills has aided greatly in its solution.
[Illustration: Plan of St. Gothard Spiral Tunnels.]
Among the great tunnels which have been excavated, the St. Gothard
is the most remarkable. It is 9¼ miles long, with a section
26¼ feet wide by 19-2/3 feet high. The work on this tunnel was
continuous, and it required 9¼ years for its completion.
The Mont Cenis tunnel, 8-1/3 miles in length, was completed in 12
years.
[Illustration: Profile of the Same.]
The Hoosac Tunnel, 4¾ miles in length, 26 feet wide and 21½ feet
high, was not prosecuted continuously; it was completed in 1876.
These tunnels are notable chiefly on account of their great length;
there are others of more moderate extent which have peculiar
features; one, illustrated on the preceding page, is unique. This
tunnel is a portion of the St. Gothard Railway, and not very far
distant from the great tunnel referred to above. In the descent
of the mountain it was absolutely necessary to secure a longer
distance than a straight line or an ordinary curve would give;
the line was therefore doubly curved upon itself. It enters the
mountain at a high elevation, describes a circle through the rock
and, constantly descending, reappears under itself at the side;
still descending, it enters the mountain at another point and
continues in another circular tunnel until it finally emerges
again, under itself, but at a comparatively short horizontal
distance from its first entry, having gained the required descent
by a continued grade through the tunnels. The profile above shows
the descent, upon a greatly reduced scale, the heavy lines marking
where the line is in the tunnel.
[Illustration: Portal of a Finished Tunnel; showing Cameron's Cone,
Colorado.]
[Illustration: Portal of a Tunnel in Process of Construction.]