12. Various special duties as commissioner of District of
Columbia, superintendent military academy, commandant engineer
school, instructors at both of these schools, attaches to
several foreign legations, for the collection of military
information, etc.
It would, of course, exceed the proper limits of a single lecture to
go into the details of these many duties, but we may take only a
passing glance at most of them, and give more special attention to a
few that may involve some points of interest. Perhaps the most
interesting branch of the subject would be that of permanent
fortifications, or what amounts to almost the same thing in this
country, sea coast defenses. And here our trouble begins, for, while
civil engineers have constant experience to guide them, their roads,
bridges, and other structures being in constant use, the military
engineer has only now and then, at long intervals, a war or a siege of
sufficient extent to furnish data upon which he can safely plan or
build his structures. Imagine a civil engineer designing a bridge,
road, or a dam to meet some possible future demand, without having
seen such a structure used for twenty years or more, and you can form
some estimate of the delightful uncertainties that surround the
military engineer when called upon to design a modern fort. The
proving ground shows him that radical improvements are necessary, but
actual service conditions are almost entirely wanting, and such as we
have contradict many of the proving ground theories. Thus we have the
records of shot going through 25 inches of iron or 25 feet of concrete
on the proving ground; but such actual service tests as the
bombardment of Fort Sumter, Fort Fisher, and the forts at Alexandria
contradict this entirely, and indicate that, except for the moral
effect, our old forts, with modern guns in them and some additional
strengthening at their weaker points, would answer all purposes so far
as bombardment from fleets is concerned. This is not saying that the
forts are good enough in their present condition, but simply that they
can readily be made far superior in strength, both offensive and
defensive, to any fleet that could possibly be provided at anything
like the same expense, or in fact at any expense that would be
justified by the condition of our treasury, either past, present, or
probable future. It might be added that a still more serious
difficulty in the way of the military engineer, so far as practice and
its consequent experiences are concerned, is that for many years past,
until quite recently, there have been no funds either for experiments
or actual work on fortifications, so that very little has been done on
them during the last twenty years.
Without going into the question of the necessity for sea coast
defenses, we may assume that an enemy is likely to come into one of
our harbors and that it is desirable to keep him out. What provisions
must be made to accomplish this, i.e., to secure the safety of the
harbors and the millions of dollars' worth of destructible property
concentrated at the great trade centers that are usually located upon
those harbors? We must first take a look at the enemy and see what he
is like before we can decide what will be needed to repel his attack.
For this purpose we need not draw on the imagination, but we may
simply examine some of the more recent armadas sent to bombard
seaports. For example, the fleet sent by Great Britain to bombard the
Egyptian city of Alexandria, in 1882. This fleet consisted of eight
heavy ironclad ships of from 5,000 to 11,000 tons displacement and
five or six smaller vessels; and the armament of this squadron
numbered more than one hundred guns of all calibers, from the sixteen
inch rifle down to the seven inch rifle, besides several smaller guns.
But this fleet represented only a small fraction of England's naval
power. During some recent evolutions she turned out thirty-six heavy
ironclads and forty smaller vessels and torpedo boats. The crews of
these vessels numbered nearly 19,000 officers and men, or about three
times the entire number in our navy. Such a fleet, or, more likely, a
much larger one, might appear at the entrance say of New York harbor
within ten days after a declaration of war, and demand whatever the
nation to which it belonged might choose, with the alternative of
bombardment.
The problem of protecting our people and property from such attacks is
not a new one, and, in fact, most of the conditions of this problem
remain the same as they were fifty years ago, the differences being in
degree rather than in kind. The most natural thought would be to meet
such a fleet by another fleet, but the folly of such a course will
become apparent from a moment's consideration. The difficulties would
be:
1st. Our fleet must be decidedly stronger than that of the enemy, or
we simply fight a duel with an equal chance of success or failure.
2d. In such a duel the enemy would risk nothing but the loss of his
fleet, and even a portion of that would be likely to escape, but we
would not only risk a similar loss, but we would also lose the city or
subject it to the payment of a heavy contribution to the enemy.
3d. Unless we have a fleet for every harbor, it would be impossible to
depend upon this kind of defense, as the enemy would select whichever
harbor he found least prepared to receive him. It would be of vital
importance that we defend every harbor of importance, as a neglect to
do so would be like locking some of our doors and leaving the others
open to the burglars.
4th. It might be thought that we could send our fleet to intercept the
enemy or blockade him in his own ports, but this has been found
impracticable. Large fleets can readily escape from blockaded harbors,
or elude each other on the high seas, and any such scheme implies that
we are much stronger on the ocean than the enemy, which is very far
from the case. To build a navy that would overmatch that of Great
Britain alone would not only cost untold millions, but it would
require many years for its accomplishment; and even if this were done,
there would be nothing unusual in an alliance of two or more powerful
nations, which would leave us again in the minority. _Fleets, then,
cannot be relied on for permanent defense_.
Again, it may be said that we have millions of the bravest soldiers in
the world who could be assembled and placed under arms at a few days'
notice. This kind of defense would also prove a delusion, for a
hundred acres of soldiers armed with rifles and field artillery would
be powerless to drive away even the smallest ironclad or stop a single
projectile from one. In fact, neither of these plans, nor both
together, would be much more effective than the windmills and
proclamations which Irving humorously describes as the means adopted
by the early Dutch governors of New York to defend that city against
the Swedes and Yankees.
Having considered some of the means of defense that will _not_ answer
the purpose, we may inquire what means _will be_ effective. And here
it should be noted that our defenses should be so effective as not
only to be reasonably safe, but to be so recognized by all nations,
and thus discourage, if not actually prevent, an attack upon our
coast.
In the first place, we must have heavy guns in such numbers and of
such sizes as to overmatch those of any fleet likely to attack us.
These guns must be securely mounted, so as to be worked with facility
and accuracy, and they must be protected from the enemy's projectiles
at least as securely as his guns are from ours. Merely placing
ourselves on equal terms with the enemy, as in case of a duel or an
ancient knight's tournament, will not answer, first, because such a
state of things would invite rather than discourage attack, and
secondly, because the enemy would have vastly more to gain by success
and vastly less to lose by failure than we would. This can be
accomplished much easier than is generally supposed, either by earthen
parapets of sufficient thickness or by iron turrets or casements. It
is evident that the weight of metal used in these structures may be
vastly greater than could be carried on shipboard. Great weight of
metal is no objection on land, but, aside from its cost, is a positive
advantage. This is evident when we consider the enormous quantity of
energy stored in the larger projectiles moving at high velocities. For
example, we often hear of the sixteen inch rifle whose projectile
weighs about one ton, and this enormous mass projected at a velocity
of 2,000 feet per second would have a kinetic energy of 60,000 foot
tons, or it would strike a blow equal to that of ten locomotives of 50
tons each running at 60 miles an hour and striking a solid wall. Any
structure designed to resist such ponderous blows must, therefore,
have enormous weight, or it will be overturned or driven bodily from
its foundations. If the armor itself is not thick enough to give the
required weight as well as resistance to penetration, the additional
stability must be supplied by re-enforcing it with heavy masses of
metal or masonry. It is evident, therefore, that _quality_ of metal is
less important than _quantity_, and that so long as it is sufficiently
tough to resist fracture, a soft, cheap metal, like wrought iron or
low steel, is better adapted for permanent works than any of the fancy
kinds of armor that have been tested for naval purposes. As an
illustration of this, we may compare compound or steel-faced armor
with wrought iron as follows: The best of the former offers only about
one-third greater resistance to penetration than the latter, or 12
inches of compound armor may equal 16 inches of wrought iron, but the
cost per ton is nearly double; so that by using wrought iron we may
have double the thickness, or 24 inches, which would give more than
double the resistance to penetration, in addition to giving double the
stability against overturning or being driven bodily out of place. But
our guns may be reasonably well protected by earthen parapets without
any expensive armor by so mounting them that when fired they will
recoil downward or to one side, so as to come below the parapet for
loading. This method of mounting is called the disappearing principle,
and has been suggested by many engineers, some of whose designs date
back more than one hundred years. We may also mount our guns in deep
pits, where they will be covered from the enemy's guns, and fire them
at high elevation, so that the shell will fall from a great height and
penetrate the decks of the enemy's ships. This is known as mortar
firing, but the modern ordnance used for this purpose is more of a
howitzer than a mortar, being simply short rifled pieces arranged for
breech loading. All our batteries should, of course, be as far from
the city or other object to be protected as possible, to prevent the
enemy from firing over and beyond the batteries into the city.
But, with all these precautions, the enemy might put on all steam and
run by us either at night or in a dense fog, and we must have some
means of holding him under the fire of our guns until his ships can be
disabled or driven away. This object is sought to be accomplished by
the use of torpedoes anchored in the channels and under the fire of
our guns, so that they cannot be removed by the enemy. These torpedoes
are generally exploded by electricity from batteries located in
casements on shore, these casements being connected with the torpedoes
by submarine cables. It is easy to see how the torpedo may be so
arranged that when struck by a ship the electric current will be
closed, and, if the battery on shore is connected at the same instant,
an explosion will take place; on the other hand, if the battery on
shore is disconnected a friendly ship may pass in safety over the
torpedoes. Many ingenious contrivances have also been devised by which
the torpedo may be made to signal back to the shore station either
that it has been struck or that it is in good order for service, in
case the enemy should undertake to run over it. One simple plan for
this is to have a small telephone in the torpedo with some loose
buckshot on the diaphragm, which is placed in a horizontal position,
and will be slightly tilted as the torpedo is moved about by the
waves. By connecting the shore end of the cable with a telephone
receiver, the rolling of the shot may be distinctly heard if the
torpedo is floating properly, but if sunk at its moorings, or if the
cable is broken, no sound will be heard.
The use of torpedoes involves the use of both electricity and high
explosives, and a careful study based upon actual experiments has been
carried on for many years, by the engineers and naval officers in all
civilized countries. Some of these experiments have supplied
interesting and useful data, for the use of the agents in question,
for various industrial purposes.
Another form of torpedo is that known as the locomotive torpedo, of
which there are several kinds; some are propelled by liquid carbonic
acid, which is carried in a strong tank and acts through a compact
engine in driving the propeller. One of these is steered by
electricity from the shore, and is known as the Lay-Haight torpedo,
and can run twenty-five miles per hour. The Whitehead torpedo is also
propelled by liquid carbonic acid, but is not steered from shore. Its
depth is regulated by an automatic device actuated by the pressure of
the water. The Howell torpedo is driven by a heavy fly wheel which is
set in rapid rotation just before the torpedo is launched. It has but
a short range and is intended for launching from ships. Another
torpedo is propelled and steered from shore by rapidly pulling out of
it two fine steel wires which, in unwinding, drive the twin screw
propellers. This is the Brennan torpedo. The Sims-Edison torpedo is
both propelled and steered by electricity from the shore, transmitted
to a motor and steering relay in the torpedo by an insulated cable.
This cable has two cores and is paid out by the torpedo as it travels
through the water just as a spider pays out its web. The cable is
about half an inch in diameter and two miles long, and the torpedo can
be driven at about eighteen miles per hour with a current of thirty
amperes and 1,800 volts pressure.
Still another auxiliary weapon of defense is the dynamite gun, or
rather, a pneumatic gun, that throws long projectiles carrying from
250 to 450 pounds of dynamite, to a distance of about two miles. The
shells are arranged to explode soon after striking the water, by an
ingenious battery that ignites the fuse as soon as the salt water
enters it. The gun, which is known as the Zalinski gun, is some sixty
feet long and fifteen inches in caliber, the compressed air being
suddenly admitted to it from the reservoirs at any desired pressure by
a special form of valve that regulates the range. These guns are to be
mounted in deep pits and fired at somewhat higher elevations than
ordinary guns, but it has great accuracy within reasonable limits of
range.