The times., 1901-03-17
BY THOMAS c. CLARKE.


Steep grades soon developed a better
brake system. and these heavier trains
have led to the invention OF the auto
matte brake worked from the engine, and
also automatic couplers, saving time and
many lives. The capacity Of our raslways
has been greatly increased by the use
of electric block signals.
The perfecting of both the railway and
its rolling stock has led to remarkable
results.
We have no accurate statistics of the
early operation of American railways In
1861 "Poors Manual estimated their to-
tai freight tonnage at 75,000O0O tons, and
the total freight receipts at si0o, 600 coo.
This was an average rate per ton of So
In 1899 Poor gives the total freight ton
mage at 975 7s9 ,94I tons and the freight
receipts at 1922. .4363l4, or an average rate
per ton of IS cents. Had the rates OF
1861 prevailed, the additional yearly cost
TO the public would have been si.275, 600 coo
or sufficient to replace the whole railway
system In two and a half years.
This is an illustration only, but Il very
striking one. Everybody knows that such
high rates of freight as those of 1856
would have checked traffic. This much
can surely be said: The reduction in cost
of operating our railways and the conse'
quent fall in freight rates have been po-
tent factors in enabling the United States
to send abroad last year S1,455, coo, ,0ot
worth of exports and flood the world
with our food and manufactured prod
ucts.
BRIDGE BUILDING.
In carly days the building of bridge
was a matter Of great ceremony, and II
was consecrated to protect it from evil
spirits. It's construction was controlled
by priests, as the title Of the Pope OF
Rome. "Pontlfex Maximus,' indicates.
Railways changed all this. Instead oi
the picturesque stone bridge, whose long
line of low arches harmonized with the
landscape, there came the straight girdei
or high truss. ugly indeed, but quickly
built, and costing much less.
Bridge construction has made greater
progress in the United States than
abroad The heavy trains that we have
described called for stronger bridges. The
large American rolling stock is not used
in England, and but little On the Cont
neut of Europe, as the width Of tunnels
and other obstacles viii not allow Of il
II is said that there is an average of one
bridge for every three miles Of railway
in the United States. making $500
bridges. most of which have been re
placed by new and stronger ones during
the last twenty years.
This demand has brought into existence
many bridge-bullding companies, some OF
whom make the whole bridge, from the
ore to the finished product.
Before the advent Of railways, highway
bridges in America were made of wood
and called trusses. Few of them existed
before railways. The large rivers and
estuaries We're crossed in horse boats, a
trip more dangerous than an Atlantic
voyage now is. a few smaller rivers had
wooden truss bridges. Although origi-
nally invented by Leonardo da Vinci, in
the sixteenth century, they were re
invented by American carpenters. Some
of Burr's bridges are still standing after
moro than one hundred years use. This
shows Whit wood can do when not over,
strained and protected from weather and
fire
The coming Of railways required Z
stronger type Of bridge TO carry con
centrated loads, and the Howe truss
with vertical iron rods. was invented
capable of l5o-foot spans
About 1863 iron bridges began to TAX,
the place of wooden bridges. Die-forgcl
eyebars and pin connections allowed o
longer panels and longer spans The frs
long-span bridge was a single-track ran
way bridge of 400-foot span over tn,
Ohio at Cincinnati, which was considered
to be a great achievement in 1870.
The Kinzua viaduct, 80 feet high anC
over half mile long, belongs to thi.
era. 1t is the type Of the numerous high
viaducts now so common.
About 1855 a new material was given L
engineers, having greater strength anC
tenacity than iron, and commercially
available from its low cost. This is basi,
steel. After many experiments. tn,
proper proportions Of carbon, phosphorus
sulphur and manganese were ascer
tanned, and uniformity resulted. Th'
opcn-hearth process is now generally
used This new chemical metal for sucl
il is, is 20 per cent stronger than iron
and can be tied in a knot when cold.
The effect of improved devices and tn,
use of steel is shown by the weights o
the ioD-foot Ohio River iron bridge, bull
in 1870. and a bridge at the same place
built ia 1856.
The bridge Of 1870 was Of iron ha,
panels = feet long, and its height was 1
| feet. and span 100 feet.
The bridge Of 1876 was Of steel. ha,
panels 80 feet long. and its height was 8
feet Its span was $50 feet The weight
of the two were nearly alike.
The cantilever design, which is a reviva
Of a very ancient type. came into use
The great Forth Bridge. in Scotland
.Go1-foot span. is of this style, as are tn
5o0-foot spans at Pouehkeepsie, and nov
new one is being designed to cross tn
/ st. Lawrence near Quebec, Of l,s00-foo
span.
This is probably near the economic limi
of cantilever construction, but the sus
/ pension bridge can be extended mucl
/ farther. as il carries no dead weight 0
! compression members.
The Niagara Suspension Bridge of SO
/ foot span, built 10y Roebling. in 1852, an'
/ the Brooklyn Bridge, of / 500 feet. bull
! by Roebling and his son, twenty year
after. marked a wonderful advance il
] bridge design.
/ Thirty years later when new bridg
! Oe /, 500 feet was wanted TO cross anothe
nart Of the East River at New York. tn
same lines Of obstruction were followed
and they will be followed in the 2,701-foo
/ span. designed u cross the North River
! some time in the twentieth century
I The only radical advance is the use of
/ better steel than could be had in Garlic
/ DAYS
! Steei-arched bridges are now sciehtih
caHy designed. Such are the new Mag