The first Suspension Bridge--The Railway Suspension
Bridge--Extraordinary vibration given to the Railway Bridge by the
fall of a mass of rock--De Veaux College--The Lewiston Suspension
Bridge--The Suspension Bridge at the Falls.
On the partial completion of the Hydraulic Canal, the principal
stockholders, with a number of invited guests, celebrated the event on
July 4, 1857, by an excursion from Buffalo in the _Cygnet_, the first
steamer that ever landed within the limits of the village of Niagara.
The same route is followed during the season of navigation by tugs
towing canal-boats and rafts out and in. No passenger boat, however, has
been placed on the route, although the sail on the river is a charming
one.
[Illustration: HOW THE SUSPENSION BRIDGE WAS BEGUN]
Mr. Charles Ellet, in 1840, built the first suspension bridge over the
chasm. He offered a reward of five dollars to any one who would get a
string across it. The next windy day all the boys in the neighborhood
were kiting, and before night a youth landed his kite in Canada and
received the reward. The first iron successor of the string was a small
wire cable, seven-eighths of an inch in diameter. To this was suspended
a wire basket in which two persons could cross the chasm. The basket was
attached to an endless rope, worked by a windlass on each bank. At an
entertainment given on the occasion of the completion of the bridge,
the good people of the embryo village at the bridge, elated with their
new acquisition, were inclined to regard their neighbors at the Falls
with patronizing sympathy. One of the latter said to Mr. Ellet, "This
bridge is a very clever affair, and you only need the Falls here to
build up a respectable village." "Well," he replied, "give me money
enough and I will put them here." He had great faith in dollar-power.
This bridge was an excellent auxiliary in the construction of the
present Railway Suspension Bridge, built by Mr. John A. Roebling. It was
begun in 1852, and the first locomotive crossed it in March, 1855. It is
one of the most brilliant examples of modern engineering, and stands
unrivaled for its grace, beauty, and strength. Seizing at once upon the
natural advantages of the location, the engineer resolved to combine the
tubular system with that of the suspension bridge. The carriage way was
placed level with the banks of the river at the edges of the chasm. The
railway track was placed eighteen feet above, on a level with the top of
the secondary banks across which the two railroads were to approach it.
The plan was perfect, and perfectly and faithfully executed in all its
details. It is practically a skeleton tube. As the traveler passes over
it in a carriage or a railway car, from the almost total absence of any
vibratory motion he feels at once that he is on a safe basis, and his
sense of security is complete.
One feature of the construction of the bridge may be noticed as having a
bearing on the question of its durability. It is well known that when
wrought-iron is exposed to long continued or oft repeated and rapid
concussions, its fibers after a time become granulated, whereby its
strength is greatly impaired and finally exhausted. It is also known
that the effect of rhythmical or regular vibrations is more destructive
than the effect of those which are inharmonious or irregular. Because of
this, a body of men is never allowed to march to music across a bridge,
nor is a large number of cattle ever driven across at one time, lest
they should, by accident, fall into a common step and so overstrain or
break down the bridge. It is the difference between a single heavy blow
and an irregular succession of light ones. Hence, when harmonious,
regular vibrations can be broken up, the destructive influence is
greatly modified and retarded.
The bridge is supported by two large cables on each side, one pair above
the other, the lower pair being nearer together horizontally than the
upper pair, so that a cross section of the skeleton tube would be shaped
somewhat like the keystone of an arch. Each of these large cables is ten
inches in diameter, and is composed of seven smaller ones, called
strands. These smaller strands are made of number nine wire, and each
one contains five hundred and twenty wires. Each of these wires was
boiled three several times in linseed oil, giving it an oleaginous
coating of considerable thickness and great adhesive power. Each wire
was carried across the river separately, from tower to tower, by a
contrivance of the engineers, the chief feature of which was a light
iron pulley about twenty inches in diameter, suspended on what might be
called a wire cord. This apparatus was called a traveler, and curious
and interesting was its performance as seen from below. It looked like a
huge spider weaving an iron web.
Six of the seven strands forming each of the cables were laid around the
seventh as a center, and when all were properly placed they were again
saturated with oil and paint. After this, by another contrivance of the
engineers, they were wound or wrapped with wire, like winding a rope
cable with marlin, and thus the whole cable was made into a thoroughly
compact, huge, round, iron rope. This was covered with numerous coats of
paint to prevent the oxidation of the inner wires. The oleaginous
coating of the wires, together with the small triangular spaces between
them, would seem to reduce the destructive power of the vibrations to
zero. But the vibrations are very greatly reduced and the stiffness of
the structure is greatly increased by the use of a series of triangular
stays, the triangle being the only geometrical figure whose angles
cannot be shifted. There are sixty-four of these triangles. Their
hypothenuses are formed by over-floor stays of wire rope reaching from
the tops of the towers to different points in the lower floor, this
latter, of course, forming their common base and the towers their
altitude. The stays are fastened to the suspenders so as to form
straight lines. As the towers and the floor are rigid and solid in the
direction of the lines they represent, it follows that the intersections
of the hypothenuses with the common base form so many stationary points
in the latter. These stationary points present a powerful resistance to
vibrations. The side trusses, with their system of diamond-work braces
and the weight of the railway track on the upper bridge, also help to
stiffen the structure. There are likewise fifty-six under stays or guys
of wire rope fastened to the rocks below, designed to prevent upward and
lateral vibrations. A heavy locomotive with twenty loaded cars produced
a depression of the upward curvature of the track of nearly ten inches.
The ordinary loads make a depression of only five inches.
In Part II., attention was directed to a point on the American side of
the river, just below this bridge, where the disintegration of the shale
and abrasion of the superposed rock is strikingly exhibited. A singular
phenomenon was witnessed here in 1863. A mass of rock and shale, about
fifty feet long, twenty feet wide, and sixty feet deep, fell with a
great crash. Directly following the fall a remarkable motion was
developed in the bridge itself. A strong wave of motion passed through
the whole structure from the American side to the opposite shore, and
returned again to the same side.
Some twelve or fifteen mechanics, who were at work on the upper or
railway track, were so alarmed that they fled with all speed to the
shore. The motion imparted to the bridge was incalculably greater than,
and of a different character from, any motion imparted by the crossing
of the heaviest trains. The rocky mass which fell was forty rods below
the bridge, and the hard floor on which it struck was more than two
hundred and thirty feet beneath it. The mass itself fell about sixty
feet average distance, and might have weighed five thousand tons. The
extraordinary motion imparted to the bridge by the concussion must have
been transmitted along the bed-rock to the anchorages on the American
side, thence through the cables and the bridge across to the anchorages
on the Canadian side, whence it returned to the American side.
Mr. Donald McKenzie, master carpenter and superintendent of repairs, who
has been connected with the bridge constantly since its erection, and
all the men under him at the time, confirm this statement, and declare
it is impossible to exaggerate or describe the wave-like motion which
they experienced while escaping to the shore.
Half a mile further down is De Veaux College, a noble charity endowed by
the late Mr. Samuel De Veaux. He was for many years an active business
man at Niagara, and by his integrity, industry, and wise enterprise
accumulated a handsome fortune. His death occurred in 1852, and by his
will he left nearly the whole of his estate to certain trustees to
establish an institution for the care, training, and education of orphan
boys. In addition to these, other pupils are received who pay a fixed
price for their tuition, board, and incidentals. The institution has
gained a high reputation for the thoroughness of its instruction and the
excellence of its discipline. One of its sources of income is the amount
received annually for admissions to the Whirlpool. Every visitor to that
interesting locality will cheerfully pay the fee charged when he
understands this fact.
The suspension bridge below the mountain near Lewiston, spanning the
river where the water emerges from the fearful abyss through which it
dashes for five miles, was built in 1856, by Mr. T. E. Serrel. The guys
designed to protect it from the effect of the wind were fastened in the
rocks on either side at the water's edge. The great ice jam of 1866
tore from their fastenings, or broke off, many of these guys. Before
they were replaced a terrific gale in the following autumn broke up the
road-way, severed some of the suspenders, and left the structure a
melancholy wreck dangling in the air.
The New Suspension Bridge, as it is called, just below the ferry at the
Falls, was built in 1868. It is a light, graceful structure, standing
one hundred and ninety feet above the water. Its length is twelve
hundred feet, after the Brooklyn bridge the longest structure of the
kind in the world, and it is the narrowest of those designed for
carriage travel. To its narrowness it probably owed its safety from
destruction during a fierce gale which occurred in the fall of 1869. The
fastenings or dowels of several of the guys on the Canadian side were
torn out, and the bridge at its center deflected down-stream more than
its width, so that the surface of its road-way could not be seen half
its length. Then its undulations from end to end--like a stair-carpet
being shaken between two persons--were frightful, and for a time it was
feared that either cables or towers must give way. After the gale
subsided the old guys were made fast again, new ones were added, and two
two-inch steel wire cables were stretched from bank to bank, and
connected with the bridge by wire stays. Wrought-iron beams were
afterward placed on the bottom stringers, and channel irons on the top
beams of the side trestles, all of which were strongly bolted together.
These improvements added much to the strength of the whole structure,
and greatly increased its ability to resist horizontal deflection.