walls (the plates are seven-sixteenths to three-
quarters of an inch in thickness), requires no
chains to hold it up, and scarcely yields
either to railway trains or to hurricanes of
wind.  The present is, indeed, a very hollow
time; but what a triumph is this hollowness
when considered (as it ought to be) in
connexion with strength and efficiency.

This tubular bridge, this Menai marvel,
has produced mighty results in the few short
years which it has yet lived.  Engineers and
machinists are becoming quite tubularly
inclined; cast-iron is at a discount, and plate-
and-rivet is above par.  Iron is used in
bridges in various ways.  In the simple cast-
iron arch there are often difficulties as to the
height of the water-way beneath; in the
simple cast-iron girder, the difficulty of casting
and the weight in handling, give a limit of
something like fifty or sixty feet to the length
attainable; in the built-up girder, formed of
separate castings fitted closely at the joints
and bolted together, bridges of a hundred
and twenty feet long have been obtained; in
the trussed girder there are separate castings
strengthened by tension rods, but the
union of cast-iron with wronght-iron is seldom
a happy one.  They cannot agree, and
disastrous family jars often result.  They cannot
expand and contract equally, and thus (as is
supposed) originated the disastrous fall of
the Dee bridge a few years ago.  In the bow-
string girder, with a roadway suspended from
an iron arch, there has been found an efficient
principle for many recently-built bridges.
But the tubular bridge differs from all these
in the simplicity of its construction, and the
profitable way in which every ounce of iron
renders its due service.  Mr. Fairbairn's
experiments led to his being invited to make
two tubular bridges for the Bolton and
Blackburn railway, of about seventy feet span;
and the excellence and cheapness of these
bridges have had their wonted effect.  A
cockney may see how ugly these girder
bridges may be made, in the examples
furnished by the railway which rejoices in
the ample name of "The London and Birmingham
and East and West India Dock Junction;"
but as there is no good reason why
that which is statically beautiful should
be aesthetically ugly, we may yet hope to see
graceful forms here married to structural
efficiency.

The route across North Wales has afforded
us the first example of this tubular plate-
and-rivet system of bridge-building; but
let us not forget that the route to South
Wales has just furnished another, comprising
a double application of this singular principle.
When the South Wales Railway was about
to be carried over the Wye, the tremendous
tide of that river at Chepstow (sixty feet
difference of level between high and low
water!) puzzled the engineer exceedingly, and
led him to adopt a strange form of bridge,
in which one-half is supported and the other
half suspended.  The bridge itself belongs to
the plate-and-rivet genus; and the suspended
portion hangs from enormous tubes, which
are themselves plate-and-rivet.  Each tube is
above three hundred feet long by nine feet in
diameter; it is circular in section, and was
built up on shore of plates and rivets.  The
hoisting of the first of these tubes, in April
1852, was a great work.  The traveller over
this unique bridge has rivets above him,
rivets around him, rivets beneath him: he
would be riveted to the spot, if he were not
whizzed away by the train.

The plate-and-rivet bears its honours
proudly in our noble iron steamers, and
in nothing does the system display itself
more remarkably.  Is it not noteworthy, for
instance, that the Great Britain, which bore
its rude fate so bravely on the Irish coast,
and which is now going to show its iron
sides among the Australians, should be built
up of sheet-iron, much in the same way as a
boiler or a funnel?  An iron keel, six inches
deep by three in width, will suffice for a ship of
a thousand tons burden; the ribs, analogous
to the futtocks of a timber ship, are often
smaller and less heavy per yard than ordinary
rails for railways; and the sheets of iron are
cut and punched and bent and riveted with an
ease which shows that the thickness is to be
measured, not by inches, but by eighths of
an inch.

The hollowness of the present time is well
illustrated by certain lighthouses; built to
bear the bluff attacks of wind and rain.  A few
years ago, Mr. Gordon constructed an iron
lighthouse on a lagoon in Jamaica; where,
owing to local difficulties, it was computed that
a tower of masonry could not have been
constructed for less than twenty thousand pounds,
or in a less period than six years, with the
almost inevitable loss of many lives.  Mr.
Gordon designed an iron tower, formed on
the model of the round towers of Ireland; in
eight months after the plan was determined
on, the iron skeleton was ready for shipment
from England; and in nine months after
that, the lighthouse was erected and ready for
lighting.  This lighthouse is formed of nine
tiers of cast-iron plates, each about ten feet
by five, each curved to the required degree of
convexity, and each fastened to its neighbours
by bolts and screws, and nuts and rivets.
So well did this iron novelty do its duty, that
another such lighthouse was built a few
years afterwards at Bermuda; it is a hundred
and five feet in height, and is formed by
about a hundred and fifty curved iron plates,
connected in the way before noticed.  These
lighthouses are not strictly examples of riveted
wrought-iron, but of bolted cast-iron;
nevertheless, the two methods are first cousins, and
serve to illustrate the economy of material to
which our modern industry is tending.

Surely, if solidity be looked for anywhere,
it might be expected in gates and barriers
against which water is pressing.  But in