idges the old form of the arch was
adopted, the stability of the structure depending wholly on compression,
the only novel feature being the use of iron instead of stone. But in a
large proportion of cases, the arch, with the railroad over it, was found
inapplicable in consequence of the limited headway which it provided.
Hence it early occurred to George Stephenson, when constructing the
Liverpool and Manchester Railway, to adopt the simple cast-iron beam for
the crossing of several roads and canals along that line--this beam
resembling in some measure the lintel of the early temples--the pressure
on the abutments being purely vertical. One of the earliest instances of
this kind of bridge was that erected over Water Street, Manchester, in
1829; after which, cast-iron girders, with their lower webs considerably
larger than their upper, were ordinarily employed where the span was
moderate; and wrought-iron tie rods below were added to give increased
strength where the span was greater.

The next step was the contrivance of arched beams or bowstring girders,
firmly held together by horizontal ties to resist the thrust, instead of
abutments. Numerous excellent specimens of this description of bridge
were erected by Robert Stephenson on the original London and Birmingham
Railway; but by far the grandest work of the kind--perfect as a specimen
of modern constructive skill--was the High Level Bridge, which we owe to
the genius of the same engineer.

The problem was, to throw a railway bridge across the deep ravine which
lies between the towns of Newcastle and Gateshead, at the bottom of which
flows the navigable river Tyne. Along and up the sides of the valley--on
the Newcastle bank especially--run streets of old-fashioned houses,
clustered together in the strange forms peculiar to the older cities.
The ravine is of great depth--so deep and so gloomy-looking towards dusk,
that local tradition records that when the Duke of Cumberland arrived
late in the evening at the brow of the hill overlooking the Tyne, on his
way to Culloden, he exclaimed to his attendants, on looking down into the
black gorge before him, "For God's sake, don't think of taking me down
that coal-pit at this time of night!" The road down the Gateshead High
Street is almost as steep as the roof of a house, and up the Newcastle
Side, as the street there is called, it is little better. During many
centuries the traffic north and south passed along this da