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[page 241:]
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STREET-PAVING.
There is, perhaps, no point in the history of the
useful
arts more remarkable than the fact, that during the last two thousand
years,
the world has been able to make no essential improvements in
road-making.
It may well be questioned if the Gothamites of 3845 will distinguish
any
traces of our Third Avenue: — and in the matter of street-pavement,
properly
so called, although of late, universal attention has been directed to
the
subject, and experiment after experiment has been tried, exhausting the
ingenuity of all modern engineers, it appears that we have at last
settled
on a result which differs in no material degree, and in principle not
at
all, from that which the Romans attained, as if instinctively, in the
Via
Appia, the Via Flaminia, the Via Valeria, the Via Tusculana, and
others.
There are streets in Pompeii to-day constructed on the very principle
which
is considered best by the moderns: or if there be any especial
variation,
it certainly is not to the credit of modern ingenuity.
The most durable and convenient of
the Roman roads
were thus composed: — The direction and breadth were first marked out
by
two shallow parallel furrows or trenches (sulci) from 15 to 8
feet
apart, according to the importance of the via. The loose earth
between
the trenches was then taken away, and the soil farther removed until a
sufficiently solid foundation was reached upon which to deposit the
materials
of the bed: — if from any cause, such as swampiness, no such natural
basis
was attainable, piles (fistucationes) were driven. Above the
natural
or artificial basis (the gremium) four strata were laid, of
which
the first (statumen) consisted of stones about three times the
size
of those employed by us in Macadamizing; next came the rudus,
broken
stones cemented with lime (answering to our rubble-work) — this was
generally
nine inches thick, and densely rammed. Then came the nucleus of
broken earthen-ware, six inches thick, and also cemented with lime.
Lastly
came the true pavement, (pavimentum) which was composed of
irregular
polygons of silex, commonly basaltic lava. These blocks,
however,
were fitted together with great nicety, and presented just such an
appearance
as do our best built polygonal stone walls. The centre of the way was
slightly
elevated, as with us, above the curb-stones. Now and then, in cities,
rectangular
slabs of softer stone were substituted for the irregular lava polygons
— and here the resemblance to the favorite modern mode was nearly
complete.
When the road or street passed over or through solid rock, the statumen
and rudus were neglected, but the nucleus was
never dispensed
with. On each side of the way were elevated foot-paths, gravelled, and
well supported; and at regular intervals were stone blocks,
corresponding
to our own steps, for the convenience of horsemen or carriages. Our
mile-stones
were also employed.
We are aware that all this is very
school-boyish
information — but we venture to place it before our readers by way of
fairly
collating the ancient and modern ideas on the general topic of
road-making,
and by way, also, of insisting on the observation with which we
commenced
— that it is exceedingly remarkable how little we have done to advance
an art of so vast an importance, notwithstanding the continuous
endeavors
which have been made, and are still making, to advance it.
The Roman road (and our own
quadrangular stone-block
pavement is but a weak imitation of it) is beyond doubt exceedingly durable;
and, so far, wherever the experiment has been
tried, it has
fully succeeded. By so far we mean so far as concerns
durability.
The objections are first, its cost, which is very great when the proper
material is employed; and secondly the street din which is
wrought
by the necessity of having the upper surfaces of the blocks roughened,
to afford a hold for the hoof. The noise from these roughened stones is
less, certainly, than the tintamarre proceeding from the round
ones
— but nevertheless is intolerable still. The first objection (cost) is
trivial where funds are at command; for in the end this species of
pavement
is the cheapest which has ever been invented, or probably ever
will
be invented — for repairs are scarcely needed at all. But it is cheap
only in a save-at-the spigot understanding of the term
— for our second
objection is one of a vital importance. The loss of time (not to
mention
temper) through the insufferable nuisance of street-noise in many of
our
most frequented thoroughfares, would overwhelm all reasonable people
with
astonishment if but once fairly and mathematically put; and
that
time is money — to an American at least — is a proposition not
for
an instant to be disputed. Nor have we dwelt upon the vast
inconvenience,
and often fatal injury resulting to invalids from the nuisance of which
we complain — and of which all classes complain, without ever
mentioning
the necessity of getting it abated.
It is generally admitted, we believe,
that as long
as they last, the wooden pavements have the advantage over all
others.
They occasion little noise (we place this item first and are
serious
in so placing it as the most important consideration of all); they are
kept clean with little labor; they save a great deal in horse power;
they
are pleasant to the hoof and thus save the health of the horse — as
well
as some twenty or thirty per cent. in the wear and tear of vehicles —
and
as much more, in time, to all travellers through the increased rapidity
of passage to and fro.
The first objection is that of injury
to the public
health from miasmata arising from the wood. Whether such
injury
actually does occur is very questionable — but there is no need of
mooting
the question, since all admit that the source of miasma (decay)
can be prevented. It is demonstrated that by the process very
improperly
called Kyanizing (since Kyan has not the slightest claim to the
invention)
even the greenest wood may be preserved for centuries, or if need be
for
a hundred, or far more. The experiments by which this effect is, as we
say, demonstrated, have been tried in every variety of way, with nearly
identical results. Blocks properly prepared, for example, were
subjected
for many years, in the fungus pit of the dockyard at Woolwich, England,
to all the known decomposing agents which can ever naturally be brought
to act against a wooden pavement, and yet were taken from the pit, at
the
close of the experiments, in as sound a condition as when originally
deposited.
The preservative agent employed was
that of corrosive
sublimate — the Bi-Chloride of Mercury. Let a pound of the sublimate be
dissolved in fifteen or sixteen gallons of water, and a piece of wood
(not
decayed) be immersed for seventy-two hours in the solution, and the
wood cannot afterwards be rotted. An instantaneous
mineralization can
be effected, if necessary, by injection of the fluid in vacuo into
the pores of the wood. It is rendered much heavier, and more brittle by
the process, and has altogether a slightly metallic character.
The cost of the Bi-chloride of
Mercury is we presume,
at present, something less than one dollar per pound — but the cost
would
be greatly reduced should the mineralizing process occasion an unusual
demand. The South American quicksilver mines, now unworked, would be
put
into operation, and we should get the article, perhaps, for forty or
even
thirty cents per pound. But even now the cost of Kyanizing is trifling
in comparison with that of cutting, squaring, and roughening stone — to
say nothing of the difference in cost between wood itself, and such
stone
as our present pavements demand.
Decay being thus prevented, all
danger from miasma is of course to be left out of the
question; and
although it has been
frequently asserted that the mercurial effluvium is injurious
to
the health — the assertion has been as frequently refuted in the most
positive
and satisfactory manner. The mercury is too closely assimilated with
the
wooden fibre to admit of any perceptible effluvium. Even where
sailors
have lived for months in the most confined holds of vessels built of
mineralized
wood, no ill consequences have been found to arise.
We write this article with no books
before us, and
are by no means positive about the accuracy of our details. The general
principles and facts, however, are not, we believe, matters of dispute.
We confess ourselves, therefore, at a loss to understand how, or why it
is, that a Kyanized wooden pavement to a limited extent, has not been
laid
(if only by way of a forlorn-hope-like experiment) in some of our
public
thoroughfares. Or are we merely ignorant of the case — and has the
experiment
been fairly tried, and found wanting? |
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