top and sunk by means of a dredge operated from
above taking out the material from the inside. The wonder of this is
hard to realise unless it is remembered that the steel hands of the
dredge were worked entirely from above, and the steel rope sinews
reached down below the surface more than one hundred feet sometimes;
yet so cleverly was the work managed that the excavation was perfect all
around, and the crib sank absolutely straight and square.

It is the fourth department of bridge-building that requires the
greatest amount not only of knowledge but of resourcefulness. In the
final process of erection conditions are likely to arise that were not
considered when the plans were drawn.

The chief engineer in charge of the erection of a bridge far from
civilisation is a little king, for it is necessary for him to have the
power of an absolute monarch over his army of workmen, which is often
composed of many different races.

With so many thousand tons of steel and stone dumped on the ground at
the bridge site, with a small force of expert workmen and a greater
number of unskilled labourers, in spite of bad weather, floods, or
fearful heat, the constructing engineer is expected to finish the work
within the specified time, and yet it must withstand the most exacting
tests.

In the heart of Africa, five hundred miles from the coast and the source
of supplies, an American engineer, aided by twenty-one American
bridgemen, built twenty-seven viaducts from 128 to 888 feet long within
a year.

The work was done in half the time and at half the cost demanded by the
English bidders. Mr. Lueder, the chief engineer, tells, in his account
of the work, of shooting lions from the car windows of the temporary
railroad, and of seeing ostriches try to keep pace with the locomotive,
but he said little of his difficulties with unskilled workmen, foreign
customs, and almost unspeakable languages. The bridge engineer the world
over is a man who accomplishes things, and who, furthermore, talks
little of his achievements.

Though the work of the bridge builders within easy reach of the steel
mills and large cities is less unusual, it is none the less adventurous.

In 1897, a steel arch bridge was completed that was built around the old
suspension bridge spanning the Niagara River over the Whirlpool Rapids.
The old suspension bridge had been in continuous service since 1855 and
had outlived its usefulness. It was decided to build a new