en iron
bridges? To this, it may be replied, that no iron bridge, made by a
reliable company, has ever shown the slightest indication of any
thing of the kind, though they have been used for many years in
Russia, Norway, Sweden, and Canada, and nothing that we know in
regard to iron gives us any reason to suppose that any thing of the
kind ever will happen. But here, again, every thing turns upon the
quality of the iron. Iron containing phosphorus is "cold-short," or
brittle when cold, and will break quicker under repeated and sudden
shocks in cold weather than when it is warm. With good iron, properly
used, we need have no fear on this point. The securing such iron is a
matter to which the utmost attention is paid by our first-class
bridge-building firms, but it is a matter to which no attention is
paid by the builders of cheap bridges. We might suppose that a
person, in putting an insufficient amount of iron into a bridge,
would be careful to get the best quality; but exactly the reverse
seems to be the case, on the ground, perhaps, that the less of a bad
thing we have, the better.

Many persons, in building wooden bridges, take no pains to get iron
rods which are suitable for such work, but purchase what is easiest
to be had in the market, and in many cases never find that the iron
was bad until a bridge tumbles down. There are, without the slightest
question, hundreds of bridges now in use in this country, which, as
far as mere proportions and dimensions go, would appear to be
entirely safe, but which, on account of the quality of the iron with
which they are made, are entirely unsafe; and there always will be,
as long as public officials purchase iron which they know nothing
about, to put into bridges. When a bridge is finished, the ordinary
examinations never detect the quality of the iron; so that the wise
remarks of many inspectors, or the opinions of those in charge of
these structures, as to the exact condition of a bridge, are of
little or no value.

We often hear iron bridges condemned, while wooden ones, so called,
are supposed to be free from defects. It does not seem to occur to
persons holding such ideas, that wooden bridges rely just as much
upon the strength of the iron rods that tie the timbers together, as
upon the timber. As a matter of fact, where one iron bridge falls, a
dozen wooden ones do the same thing. One very decided advantage which
an iron bridge has over a wooden one, is that we can ma