Daily Yellowstone journal., 1889-12-28
AMERICAN BRIDGES.
What several Famous French Engineers
Have TO say About Them.

What several Famous French Engineers
Have to Say About Them.
The Socicte dies Ingenious Civils re-
Gently discussed this question, and on
account Of this discussion, published
in The Revue lndustrielle. may be of
interest, as showing what foreign en-
gincoIS think OF American methods;
The ~, systems of construction en-
ployed N America for metallic bridges
are well luown. One OF the most no
ticeablc bridges is that at Pouchkccp-
sic, on the Hudson. which was opened
last year. RiyCts arc very Sparingly
used, large pins being substituted,
thus rendering the erection of the
trusses more economical and rapid.
Tie metallic portion of the large
bridge at Poughkecpsie was erected IN
a few months. Dir. L. de Gu2ly meE-
tons. in Il communication which he
has Just made Ia the Socicte DIES In
geniCurs Owls, a still more eXtraordi-
nary example. The large bridge al
the base of Niagara Falls is 200 feet
above the river, with central spans,
4SO feet long. Of tie same system as
those used in the bridge overthe Hud-
son. The shop work and erection of
Niagara bridge We're completed in the
short space of nine months and half.
The dimensions of the Poughkeepsie
bridge are given, followed by the
statement that this work was erected
very rapidly and economically, not.
withstanding It's magnitude. -Four Of
the spans are rigid trusses, which were
erected upon false work resting ON
enormous piles driven into the bed of
the river near its center. The three
remaining spans were erected without
scaifolding OF other false work. ac-
cording 10 the new system called by
the Americans ''cantileyer.'
To illustrate the great economy and
safety resulting from the simplicity OF
the American system, the author re-
calls the facts which occurred n few
years ago on the Oroya railroad, which
crosses the Cordilleras ut an alti.
tude of more than l2,C00 feet.
At the Ncrrugas viaduct. three short
spans on the Fink system, 100 feet
long, We're erected IN sixteen hours by
a force of City men at Il height of 215
feet above the ground. On the same
railroad, four spans, each 100 feet in
length, were erected. Two were built
by the English, with the old American
Town truss. The erection required
more than two mOnths. When tested
the first one fell into the myiuc. The
second also broke down, when loaded,
and fell upon the scatfolding which
had been left in place. The third
bsidge, OF French construction, and
whose lattice truSscs were riveted,
was erected in about a month, and
sustained the test perfectly. The
fourth, Of American construction, on
the Fink system, also sustained the
test without injury. 1t had been
erected in five days. An interesting
fact to be noted is that the three Euro
pean bridges weighed lG4 tons, while
the American bridge only weighed
siXty.six tons. These four bridges
were of iron, and their prices must
necessarily have been in proportion TO
their weights, apart from certain diff
ferences in the method of construc-
ton.
After t~har.ading Of this communi.
cation, Mr.. $. PerisSe expressed the
opinion that, when the question Of
time is a condition sine qua non, it
is well TO use American pinned
bridges; but that in all othercaseS the
preference should be given to riveted
bridges. Even though pinned bridges
Sustain tests just as well as riveted
bridges, there is reason 10 believe that
the latter will be more durable, since
the play which necessarily occurs be-
tween the pins and the no, is a sure
cause of destruction that does not exist
in riycted bridges.
On the other hand, TO compare the
economy Of n system with that of
the other, account should be taken
not only Of the weight, but also Of the
cost of construction per unit Of
weight, which, according to Mr.. Pc
RISE, must be much higher for pinned
than for rivcted bridges; but it is none
the less true that Americans know how
10 build fast and well.
Mr.. Regnard remarked that people
often made mistakes in talking about
the pins Of American bridges. They
+ not, properly speaking, bolts for
tightening joints, but, more accurate
ly, large Joint pins of great diameter,
turned and fitted TO within two ten
thousandths inch to the holes in the
parts which arc TO be united. AS TO
the question of price, Mr.. Regnard
thinks that the American system ought
TO be very cheap on account of its
lightness, and also because il is com
posed Of parts which require little or
no forge work.