with shops, a school, and a surgery. Two
fire-engines and large tanks of water were kept in constant readiness in
case of fire, and for many months rivet-making machines, punching
machines, shearing machines, etcetera, were in full work. There were
two million rivets used altogether, and the quantity of
three-quarter-inch iron rod used in making them measured 126 miles. The
total weight of iron used was nearly 12,000 tons. The bridge was
strengthened by eighty-three miles of angle iron. For many months the
outlay in wages alone was 6000 pounds a week, and the cost for the whole
of the works more than 600,000 pounds. A curious fact connected with
this enormous mass of iron is, that arrangements had to be made to
permit of shrinkage and expansion. The tubes were placed on a series of
rollers and iron balls, and it was afterwards found that in the hottest
part of summer they were twelve inches longer than in winter--a
difference which, if not provided for, would have caused the destruction
of the towers by a constant and irresistible pull and thrust! The Menai
Bridge was begun in 1846 and opened for traffic in March 1850.

Space would fail us were we to attempt even a slight sketch of the great
engineering works that railways have called into being. We can merely
point to such achievements as the high-level bridges at
Newcastle-on-Tyne, Berwick-on-Tweed, and at Saltash, over the Tamar.
There are viaducts of great height, length, and beauty in all parts of
the kingdom; there are terminal stations so vast and magnificent as to
remind one of the structures of Eastern splendour described in the
_Arabian Nights Entertainments_; and there are hundreds of miles of
tunnelling at the present time in the United Kingdom.

The Metropolitan Railway is the most important and singular of these
tunnels--for it is entitled to be regarded as a gigantic tunnel--which
burrows under the streets of London.

This stupendous work was undertaken in order to relieve the traffic in
the streets of London. The frequent blocks that used to occur not many
years ago in the main thoroughfares of the Metropolis, had rendered
relief absolutely necessary. When the increase of railways began to
pour human beings and goods from all parts of the kingdom into London in
a continuous and ever-increasing stream, it became obvious that some new
mode of conveyance must be opened up. After much deliberation as to the
best method, it was finally resolved