Atlantic Monthly, Vol. 11, No. 63, January, 1863 by Various

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"_23d Dec. 1790._ About 3 o'clock A.M., I heard a sound and felt a shock
like unto heavy thunder. I went out, but could not observe any cloud.
I therefore conclude it must be a great earthquake in some part of the
globe."

In April, 1800, he writes:--

"The first great locust year that I can remember was 1749. I was then
about seventeen years of age, when thousands of them came creeping up
the trees. I imagined they came to destroy the fruit of the earth, and
would occasion a famine in the land. I therefore began to destroy
them, but soon saw that my labor was in vain. Again, in the year 1766,
seventeen years after their first appearance, they made a second. I
then, being about thirty-four years of age, had more sense than to
endeavor to destroy them, knowing they were not so pernicious to the
fruit as I had imagined. Again, in the year 1783, which was seventeen
years later, they made their third appearance to me; and they may be
expected again in 1800. The female has a sting in her tail as sharp and
hard as a thorn, with which she perforates the branches of trees, and in
the holes lays eggs. The branch soon dies and falls. Then the egg, by
some occult cause, immerges a great depth into the earth, and there
continues for the space of seventeen years, as aforesaid."

The following is worthy of Pliny:--

"In the month of January, 1797, on a pleasant day for the season, I
observed my honey-bees to be out of their hives, and they seemed to be
very busy, excepting one hive. Upon examination, I found all the bees
had evacuated this hive, and left not a drop behind them. On the 9th of
February ensuing, I killed the neighboring hives of bees, and found a
great quantity of honey, considering the season,--which I imagine the
stronger had taken from the weaker, and the weaker had pursued them
to their home, resolved to be benefited by their labor, or die in the
contest."

Mr. Benjamin H. Ellicott, who was a true friend of Banneker, and
collected from various sources all the facts concerning him, wrote in a
letter as follows:--

"During the whole of his long life he lived respectably and much
esteemed by all who became acquainted with him, but more especially
by those who could fully appreciate his genius and the extent of his
acquirements. Although his mode of life was regular and extremely
retired,--living alone, having never married, cooking his own victuals
and washing his own clothes, and scarcely ever being absent from
home,--yet there was nothing misanthropic in his character; for a
gentleman who knew him thus speaks of him: 'I recollect him well. He
was a brave-looking, pleasant man, with something very noble in his
appearance. His mind was evidently much engrossed in his calculations;
but he was glad to receive the visits which we often paid him.' Another
writes: 'When I was a boy I became very much interested in him, as his
manners were those of a perfect gentleman: kind, generous, hospitable,
humane, dignified, and pleasing, abounding in information on all the
various subjects and incidents of the day, very modest and unassuming,
and delighting in society at his own house. I have seen him frequently.
His head was covered with a thick suit of white hair, which gave him
a very dignified and venerable appearance. His dress was uniformly of
superfine drab broadcloth, made in the old style of a plain coat, with
straight collar and long waistcoat, and a broad-brimmed hat. His color
was not jet-black, but decidedly negro. In size and personal appearance,
the statue of Franklin at the library in Philadelphia, as seen from the
street, is a perfect likeness of him. Go to his house when you would,
either by day or night, there was constantly standing in the middle of
the floor a large table covered with books and papers. As he was an
eminent mathematician, he was constantly in correspondence with other
mathematicians in this country, with whom there was an interchange of
questions of difficult solution.'"

Banneker died in the year 1804, beloved and respected by all who knew
him. Though no monument marks the spot where he was born and lived a
true and high life and was buried, yet history must record that the most
original scientific intellect which the South has yet produced was that
of the pure African, Benjamin Banneker.

* * * * *

THE SLEEPING SENTINEL.

When the great Theban, in his midnight tramp,
A sleeping guard beside the postern saw,
He slew him on the instant, that the camp
Might read in blood a soldier's swerveless law.

"Blame not your General!"--pointing to the slain,--
The wise, severe Epaminondas said,--
"I was not cruel, comrades, for 't is plain
I only left him, as I found him, dead!"

IRON-CLAD SHIPS AND HEAVY ORDNANCE.

The new system of naval warfare which characterizes the age was proposed
by John Stevens of Hoboken during the War of 1812, recommended by
Paixhans in 1821, made the subject of official and private experiment
here and in Europe during the last ten years especially, subjected to
practical test at Kinburn in 1855, recognized then by France and England
in the commencement of iron-clad fleets, first practised by the United
States Government in the capture of Fort Henry, and at last established
and inaugurated not only in fact, but in the principle and direction of
progress, by the memorable action of the ninth of March, 1862, in the
destruction of the wooden sailing-frigates Cumberland and Congress by
the steam-ram Merrimack, and the final discomfiture of that powerful and
heavily armed victor by the turreted, iron, two-gun Monitor.

The consideration of iron-clad vessels involves that of armor, ordnance,
projectiles, and naval architecture.

ARMOR.

_Material_. In 1861, the British iron-plate committee fired with
68-pounders at many varieties of iron, cast-steel and puddled-steel
plates, and combinations of hard and soft metals. The steel was too
brittle, and crumbled, and the targets were injured in proportion to
their hardness. An obvious conclusion from all subsequent firing at
thick iron plates was, that, to avoid cracking on the one hand, and
punching on the other, wrought-iron armor should resemble copper more
than steel, except that it should be elastic, although not necessarily
of the highest tensile strength. Copper, however, proved much too soft.
The experiments of Mr. E.A. Stevens of Hoboken, with thick plates,
confirm this conclusion. But for laminated armor, (several thicknesses
of thin plates,) harder and stronger iron offers greater resistance to
shot, and steel crumbles less than when it is thicker. The value of hard
surfaces on inclined armor will be alluded to.

_Solid and Laminated Armor compared. Backing_. European experimenters
set out upon the principle that the resistance of plates is nearly as
the square of their thickness,--for example, that two 2-inch plates are
but half as strong as one 4-inch plate; and the English, at least, have
never subjected it to more than one valuable test. During the last year,
a 6-inch target, composed of 5/8-inch boiler-plates, with a 1-1/2-inch
plate in front, and held together by alternate rivets and screws 8
inches apart, was completely punched; and a 10-inch target, similarly
constructed, was greatly bulged and broken at the back by the 68-pounder
(8 inch) smooth-bore especially, and the 100-pounder rifle at 200
yards,--guns that do not greatly injure the best solid 4-1/2-inch plates
at the same range. On the contrary, a 124-pounder (10 inch) round-shot,
having about the same penetrating power, as calculated by the ordinary
rule, fired by Mr. Stevens in 1854, but slightly indented, and did not
break at the back, a 6-5/8-inch target similarly composed. All the
experiments of Mr. Stevens go to show the superiority of laminated
armor. Within a few months, official American experiments have confirmed
this theory, although the practice in the construction of ships is
divided. The Roanoke's plates are solid; those of the Monitor class are
laminated. Solid plates, generally 4-1/2 inches thick and backed by 18
inches of teak, are exclusively used in Europe. Now the resistance of
plates to punching _in a machine_ is directly as the sheared area, that
is to say, as the depth and the diameter of the hole. But, the argument
is, in this case, and in the case of laminated armor, the hole
is cylindrical, while in the case of a thick armor-plate it is
conical,--about the size of the shot, in front, and very much larger in
the rear,--so that the sheared or fractured area is much greater. Again,
forged plates, although made with innumerable welds from scrap which
cannot be homogeneous, are, as compared with rolled plates made with
few welds from equally good material, notoriously stronger, because the
laminae composing the latter are not thoroughly welded to each other,
and they are therefore a series of thin plates. On the whole, the facts
are not complete enough to warrant a conclusion. It is probable that the
heavy English machinery produces better-worked thick plates than have
been tested in America, and that American iron, which is well worked in
the _thin_ plate used for laminated armor, is better than English iron;
while the comparatively high velocities of shot used in England are more
trying to thin plates, and the comparatively heavy shot in America prove
most destructive to solid plates. So that there is as yet no common
ground of comparison. The cost of laminated armor is less than half that
of solid plates. Thin plates, breaking joints, and bolted to or through
the backing, form a continuous girder and add vastly to the strength of
a vessel, while solid blocks add no such strength, but are a source of
strain and weakness. In the experiments mentioned, there was no wooden
backing behind the armor. It is hardly possible,--in fact, it is nowhere
urged,--that elastic wooden backing prevents injury to the _armor_ in
any considerable degree. Indeed, the English experiments of 1861 prove
that a rigid backing of masonry--in other words, more armor--increases
the endurance of the plates struck. Elastic backing, however, deadens
the blow upon the structure behind it, and catches the iron splinters;
it is, therefore, indispensable in ships.

_Vertical and Inclined Armor_. In England, in 1860, a target composed of
4-1/2-inch plates backed with wood and set at 38 deg. from the horizon was
injured about one-half as much by round 68-pounder shot as vertical
plates of the same thickness would have been. In 1861, a 3-1/4 plate at
45 deg. was more injured by elongated 100-pounder shot than a 4-1/2 vertical
plate, both plates having the same backing and the weights of iron being
equal for the same vertical height. When set at practicable angles,
inclined armor does not glance flat-fronted projectiles. Its greater
cost, and especially the waste of room it occasions in a ship, are
practically considered in England to be fatal objections. The result of
Mr. Stevens's experiments is, substantially, that a given thickness of
iron, measured on the line of fire, offers about equal resistance to
shot, whether it is vertical or inclined. Flat-fronted or punch shot
will be glanced by armor set at about 12 deg. from the horizon. A hard
surface on the armor increases this effect; and to this end, experiments
with Franklinite are in progress. The inconvenience of inclined armor,
especially in sea-going vessels, although its weight is better situated
than that of vertical armor, is likely to limit its use generally.

_Fastening Armor_. A series of thin plates not only strengthen the whole
vessel, but fasten each other. All methods of giving continuity to thick
plates, such as tonguing and grooving, besides being very costly,
have proved too weak to stand shot, and are generally abandoned. The
_fastenings_ must therefore be stronger, as each plate depends solely on
its own; and the resistance of plates must be decreased, either by more
or larger bolt-holes. The working of the thick plates of the European
vessels Warrior and La Gloire, in a sea-way, is an acknowledged defect.
There are various practicable plans of fastening bolts to the backs of
plates, and of holding plates between angle-irons, to avoid boring
them through. It is believed that plates will ultimately be welded.
Boiler-joints have been welded rapidly and uniformly by means of light
furnaces moving along the joint, blowing a jet of flame upon it, and
closely followed by hammers to close it up. The surfaces do not oxidize
when enveloped in flame, and the weld is likely to be as strong as the
solid plate. Large plates prove stronger than small plates of equally
good material. English 4-1/2-inch armor-plates are generally 3-1/2 feet
wide and to 24 feet long. American 4-1/2-inch plates are from 2 to 3
feet wide and rarely exceed 12 feet in length. Armor composed of light
bars, like that of the Galena, is very defective, as each bar, deriving
little strength from adjacent, offers only the resistance of its own
small section. The cheapness of such armor, however, and the facility
with which it can be attached, may compensate for the greater amount
required, when weight is not objectionable. The 14-inch and 10-inch
targets, constructed, without backing, on this principle, and tested in
England in 1859 and 1860, were little damaged by 68-and 100-pounders.

The necessary thickness of armor is simply a question of powder, and
will be further referred to under the heads of Ordnance and Naval
Architecture.

ORDNANCE AND PROJECTILES.

_Condition of Greatest Effect_. It is a well-settled rule, that the
penetration projectiles is proportionate directly to their weight
and diameter, and to the square of their velocity. For example, the
10-1/2-inch Armstrong 150-pound shot, thrown by 50 pounds of powder at
1,770 feet per second, has nearly twice the destructive effect upon
striking, and four times as much upon passing its whole diameter through
armor, as the 15-inch 425-pound shot driven by the same powder at 800
feet. The American theory is, that very heavy shot, at necessarily low
velocities, with a given strain on the gun, will do more damage, by
racking and straining the whole structure than lighter and faster shot
which merely penetrate. This is not yet sufficiently tested. The late
remarkable experiments in England--firing 130-and 150-pound Whitworth
steel shells, holding 3 to 5 pounds of powder, from a 7-inch Armstrong
gun, with 23 to 27 pounds of powder, through the Warrior target, and
bursting them in and beyond the backing--certainly show that large
calibres are not indispensable in fighting iron-clads. A destructive
blow requires a _heavy charge of powder_; which brings us to

_The Strain and Structure of Guns, and Cartridges_. The problem is, 1st,
to construct a gun which will stand the heaviest charge; 2d, to reduce
the strain on the gun without reducing the velocity of the shot. It
is probable that powder-gas, from the excessive suddenness of its
generation, exerts a percussive as well as a statical pressure, thus
requiring great elasticity and a certain degree of hardness in the
gun-metal, as well as high tensile strength. Cast-iron and bronze are
obviously inadequate. Solid wrought-iron forgings are not all that could
be desired in respect of elasticity and hardness, but their chief defect
is want of homogeneity, due to the crude process of puddling, and to
their numerous and indispensable welds. Low cast-steel, besides being
elastic, hard, tenacious, and homogeneous, has the crowning advantage of
being produced in large masses without flaw or weld. Krupp, of Prussia,
casts ingots of above 20 tons' weight, and has forged a cast-steel
cannon of 9 inches bore. One of these ingots, in the Great Exhibition,
measured 44 inches in diameter, and was uniform and fine-grained
throughout. His great success is chiefly due to the use of manganesian
iron, (which, however, is inferior to the Franklinite of New Jersey,
because it contains no zinc,) and to skill in heating the metal, and to
the use of heavy hammers. His heaviest hammer weighs 40 tons, falls 12
feet, and strikes a blow which does not draw the surface like a light
hammer, but compresses the whole mass to the core. Krupp is now
introducing the Bessemer process for producing ingots of any size at
about the cost of wrought-iron. These and other makes of low-steel
have endured extraordinary tests in the form of small guns and other
structures subject to concussion and strain; and both the theory and all
the evidence that we have promise its superiority for gun-metal. But
another element of resistance is required in guns with thick walls. The
explosion of the powder is so instantaneous that the exterior parts of
the metal do not have time to act before the inner parts are strained
beyond endurance. In order to bring all parts of a great mass of metal
into simultaneous tension, Blakely and others have hooped an inner tube
with rings having a successively higher initial tension. The inner tube
is therefore under compression, and the outer ring under a considerable
tension, when the gun is at rest, but all parts are strained
simultaneously and alike when the gun is under pressure. The Parrott and
Whitworth cannon are constructed on this principle, and there has been
some practice in winding tubes with square steel wire to secure the most
uniform gradation of tension at the least cost. There is some difficulty
as yet in fastening the wire and giving the gun proper longitudinal
strength. Mr. Wiard, of New York, makes an ingenious argument to show
that large cannon burst from the expansion of the inner part of the gun
by the heat of frequent successive explosions. In this he is sustained
to some extent by Mr. Mallet, of Dublin. The greater the enlargement of
the inner layer of metal, the less valuable is the above principle of
initial tension. In fact, placing the inner part of the gun in initial
tension and the outer part in compression would better resist the
effect of internal heat. But Mr. Wiard believes that the _longitudinal_
expansion of the inner stratum of the gun is the principal source of
strain. A gun made of annular tubes meets this part of the difficulty;
for, if the inner tube is excessively heated, it can elongate and slip
a little within those surrounding it, without disturbing them. In fact,
the inner tube of the Armstrong gun is sometimes turned within the
others by the inertia of the rifled projectile. On the whole, then,
hooping an inner steel tube with successively tighter steel rings, or,
what is better, tubes, is the probable direction of improvement in heavy
ordnance. An inner tube of iron, cast hollow on Rodman's plan, so as to
avoid an inherent rupturing strain, and hooped with low-steel without
welds, would be cheaper and very strong. An obvious conclusion is,
that perfect elasticity in the metal would successfully meet all the
foregoing causes of rupture.

In America, where guns made entirely of cast-iron, and undoubtedly the
best in the world for horizontal shell-firing, are persisted in, though
hardly adequate to the heavy charges demanded by iron-clad warfare, the
necessity of decreasing the strain on the gun without greatly reducing
the velocity of the shot has become imperative. It would be impossible
even to recapitulate the conflicting arguments of the experts on this
subject, within the limits of this paper. It does appear from recent
experiments, however, that this result can be accomplished by
compressing the powder, so that, we will suppose, it burns slowly and
overcomes the inertia of the shot before the whole mass is ignited; and
also by leaving an airspace around the cartridge, into which the gases
probably expand while the inertia of the shot is being overcome, thus
avoiding the excessive blow upon the walls of the gun during the first
instant of the explosion. Whatever the cause may be, the result is of
the highest importance, not only as to cast-iron guns, but as to all
ordnance, and warrants the most earnest and thorough investigation. The
principles of the Armstrong gun differ in some degree from all those
mentioned, and will be better referred to under the head of _Heavy
Ordnance Described_. The Armstrong gun is thus fabricated. A long bar of
iron, say 3 by 4 inches in section, is wound into a close coil about 2
feet long and of the required diameter,--say 18 inches. This is set upon
end at a welding heat under a steam-hammer and "upset" into a tube which
is then recessed in a lathe on the ends so as to fit into other tubes.
Two tubes set end to end are heated to welding, squeezed together by
a heavy screw passing through them, and then hammered lightly on the
outside without a mandrel. Other short tubes are similarly added. Five
tubes of different lengths and diameters are turned and bored and shrunk
over one another, without successively increasing tension, however, to
form a gun. The breech-end of the second tube from the bore is forged
solid so that its grain will run parallel with the bore and give the
gun longitudinal strength. Both the wedge and the screw breech-loading
apparatus are employed on guns of 7 inches bore (110-pounders) and
under. It will thus be seen that the defects of large solid forgings are
avoided; that the iron may be well worked before it is formed into a
gun; and that its greatest strength is in the direction of the greatest
strain; and on the other hand, that the gun is weak longitudinally and
excessively costly, (the 7-inch gun costs $4,000, and tin 10-1/2-inch,
$9,000,) and that the material, although strong and pretty trustworthy
in the shape of bars, has insufficient elasticity and hardness. Still,
it is a formidable gun, especially when relieved of the weak and complex
breech-loading apparatus, and used with a better system of rifling and
projectiles than Armstrong's. The 110-pounder Armstrong rifle has 99-1/2
inches length and 7 inches diameter of bore, 27 inches maximum diameter,
and weighs 4-1/3 tons. The "300-pounder" smooth-bore has 11 feet length
and 10-1/2 inches diameter of bore, 38 inches maximum diameter, and
weighs 10-1/2 tons. The Mersey Iron-Works guns are of wrought-iron, and
are forged solid like steamboat-shafts, or hollow by laying up staves
into the form of a barrel and welding layers of curved plates upon
them until the whole mass is united. But few of these guns have
been fabricated. The most remarkable of them are, 1st, the Horsfall
smooth-bore, of 13 inches bore, 44 inches maximum diameter, and 24
tons weight,--price, $12,500; 2d, the "Alfred" rifle, in the recent
Exhibition, of 10 inches bore,--price, $5,000; 3d, the 12-inch
smooth-bore in the Brooklyn Navy-Yard, which, though very light, has
fired a double 224-pound shot with 45 pounds of powder: if properly
hooped, it would make the most formidable gun in America. Blakely has
constructed for Russia two 13-inch smooth-bore guns, 15 feet long and 47
inches maximum diameter, of cast-iron hooped with steel: price, $10,000
each. He has also fabricated many others of large calibre, on the
principles before mentioned. The 15-inch Rodman smooth-bore cast-iron
gun is of 48 inches maximum diameter, 15 feet 10 inches long, and weighs
25 tons. The cost of such guns is about $6,000. The Dahlgren 15-inch
guns on the Monitors are about four feet shorter.

_Results of Heavy Ordnance_. The 10-1/2-inch Armstrong gun sent a round
150-pound shot, with 50 pounds of powder, through a 5-1/2-inch solid
plate and its 9-inch teak backing and 5/8-inch iron lining, at 200
yards, and one out of four shots with the same charge through the
Warrior target, namely, a 4-1/2-inch solid plate, 18-inch backing, and
5/8-inch lining. The Horsfall 13-inch gun sent a round 270-pound shot,
with 74 pounds of powder, entirely through the Warrior target at 200
yards, making an irregular hole about 2 feet in diameter. The same
charge at 800 yards did not make a clean breach. The Whitworth
shell burst in the backing of the same target has been referred to.
Experiments on the effect of the 15-inch gun are now in progress. Its
hollow 375-pound shot (3-inch walls) was broken without doing serious
damage to 10-1/2-inch laminated armor backed with 18 inches of oak.
The comparative test of solid and laminated armor has already been
mentioned. The best 4-1/2-inch solid plates, well backed, are
practically proof against the guns of English iron-clads, namely,
68-pounder smooth-bores and Armstrong 110-pounder rifles, the service
charge of each being 16 pounds.

_Rifling and Projectiles_. The spherical shot, presenting a larger area
to the action of the powder, for a given weight, than the elongated
rifle-shot, has a higher initial velocity with a given charge; and all
the power applied to it is converted into velocity, while a part of the
power applied to the rifle-shot is employed in spinning it on its axis.
But, as compared with the rifle-shot, at long ranges, it quickly loses,
1st, velocity, because it presents a larger area to the resisting air;
2d, penetration, because it has to force a larger hole through the
armor; and 3d, accuracy, because the spinning of the rifle-shot
constantly shifts from side to side any inaccuracy of weight it may
have on either side of its centre, so that it has no time to deviate in
either direction. Practically, however, iron-clad warfare must be
at close quarters, because it is almost impossible to _aim_ any gun
situated on a movable ship's deck so that it will hit a rapidly moving
object at a distance. It is believed by some authorities that elongated
shot can be sufficiently well balanced to be projected accurately
from smooth-bores; still, it is stated by Whitworth and others that a
spinning motion is necessary to keep an elongated shot on end while
passing through armor. On the whole, so far as penetrating armor is
concerned, the theory and practice favor the spherical shot. But a more
destructive effect than mere penetration has been alluded to,--the
bursting of a shell within the backing of an iron-clad vessel. This
can be accomplished only by an elongated missile with a solid head for
making the hole and a hollow rear for holding the bursting charge. The
rifle-shot used in America, and the Armstrong and some other European
shot, are covered with soft metal, which in muzzle-loaders is expanded
by the explosion so as to fill the grooves of the gun, and in
breech-loaders is planed by the lands of the gun to fit the
rifling,--all of which is wasteful of power. Whitworth employs a solid
iron or steel projectile dressed by machinery beforehand to fit the
rifling. But as the bore of his gun is hexagonal, the greater part of
the power employed to spin the shot tends directly to burst the gun.
Captain Scott, R.N., employs a solid projectile dressed to fit by
machinery; but the surfaces of the lands upon which the shot presses are
radial to the bore, so that the rotation of the shot tends, not to split
the gun, but simply to rotate it in the opposite direction.

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