Eugene Griffin.

Sea-coast defences online

. (page 1 of 6)
Online LibraryEugene GriffinSea-coast defences → online text (page 1 of 6)
Font size
QR-code for this ebook


LIBRARY

OF THE

UNIVERSITY OF CALIFORNIA.
Deceived ^Zx^ - , 189 ff



^Accession No.



. Class No.






OUR



COAST
DEFENCES



BY



EUGENE GRIFFIN

First Lieutenant Corps of Engineers, U.S.A.




NEW YORK * LONDON

C. P. PUTNAM'S SONS

1885




Military Service Institution, U. S.



Monographs, No. i.



COPYRIGHT

THE MILITARY SERVICE INSTITUTION

1885



OUR SEA-COAST DEFENCES.

BY LIEUT. EUGENE GRIFFIN, U.S.A.,

CORPS OF ENGINEERS.

PART I. OUR SEA-COAST DEFENCES, PAST AND PRESENT.

ENGINEERS have divided our early fortifications into three
systems: (i) those built before and during the Revolutionary
War; (2) those built subsequent to the Revolution but previous
to the War of 1812 ; (3) those built since 1816. The last alone
arc of present importance, as they still constitute the major part
of our maritime defences.

The utter inadequacy of temporary sea-coast fortifications
was painfully evident during the second war with Great Britain,
and demanded immediate attention upon the declaration of peace.
In 1816, a comprehensive system was devised by a board of
engineer officers, approved by the Chief of Engineers and the Sec-
retary of War, and adopted by Congress ; and yearly appropria-
tions were thereafter made for the construction of the works.

In planning this system the board considered that " fortifica-
tions must :

" ist. Close all important harbors against an enemy and
secure them to our military and commercial marine.

" 2d. Deprive an enemy of all strong positions where, pro-
tected by naval superiority, he might fix permanent quarters in
our territory, maintain himself during the war, and keep the
whole frontier in perpetual alarm.

" 3d. Cover the great cities from attack.

"4th. Prevent, as far as practicable, the great avenues of
interior navigation from being blockaded at their entrance into
the ocean.

" 5th. Cover the coast-wise and interior navigation by closing
the harbors and the several inlets from the sea which intersect the



2 OUR SEA-COAST DEFENCES.

lines of communication, and thereby further aid the navy in pro-
tecting the navigation of the country.*

" 6th. Protect the great naval establishments." '

To accomplish these results fortifications were so placed as to
command the harbor entrances, channels, and rivers requiring de-
fence, and interior works constructed to command all positions
which might be occupied by the enemy should he succeed in for-
cing the main line. These works consisted mainly of masonry
casemates with two or more tiers of fire, surmounted by earthen
barbette batteries. Stone walls were less vulnerable than wooden
walls, and land fire more accurate and steady than that of ships ;
hence, while engineers had long recognized the principle that all.
masonry should be shielded, from land fire by earthen masks, the
same secure cover was not necessary for sea-fronts. Guns at
least equal in numbers and calibres to those of any possible
attacking squadron were mounted in these works; the several
tiers providing sufficient emplacements and permitting a great
concentration of guns on a comparatively contracted site.

The works were given but slight command, the better to
utilize the advantages of ricochet fire; and land-fronts of greater
or less strength were added, to enable the garrison to withstand
a siege of from ten to fifty days.

During the long periods of peace which followed the War of
1812, many conditions were altered both in the attack and de-
fence, and corresponding changes were required in the system.
The introduction of the steam-engine rendered ships independent
of wind and weather, and this advantage was so greatly increased
by the invention of the screw propeller, which placed the motive
power out of sight and reach of the guns, that channel obstruc-
tions, to prevent the ships from running by the batteries, became
an absolute necessity and an important feature of the defence.

The invention of the magnetic telegraph and the construction
of innumerable lines of railroads so facilitated the concentrations
and movements of troops that the costly land-fronts became un-
necessary, except in specially isolated works ; it being deemed
sufficient to provide such defences as would protect the garrison
from surprise or enable them to repel a sudden assault.

The latest and strongest of our granite forts were built with
eight-foot walls, reduced to five feet in the vicinity of the gun-
ports. Totten's iron casemate embrasure protected the can-

* Revised Report of the Board of Engineers, March 24, 1826.



OUR SEA-COAST DEFENCES. 3

noneers from direct fire when the shutters were closed, and from
glancing shots when open, -a degree of security not possessed by
the works of any other nation. This invention of our chief
engineer is of historic interest as the first instance of the use of
iron plating on land batteries.

These works were model sea-coast fortifications in their day,
and none better existed in the world ; but it should be remem-
bered that they were only intended to withstand the fire of the
old 10- and 1 3-inch smooth-bores, guns inferior in power to even
the 8-inch rifle of the present day, to say nothing of the 16-
and i /-inch guns.

The appearance of the French iron-clad floating batteries
during the Crimean War marked the beginning of a new era in
naval warfare ; and their engagement with the Russian forts at
Kinburn * gave rise to serious doubts as to the ability of masonry
casemates to withstand these new engines of attack. Heretofore
ships had been unable to remain under fire sufficiently long for
their guns to produce serious effect upon the batteries, but the
use of iron plating 1 reversed the conditions as to security of cover
and inclined the balance in favor of the attack.

The developments of our civil war, the broadside and
turreted iron-clads and the long-range heavy ordnance, both
smooth-bore and rifled, demonstrated this superiority beyond
question, and marked the complete downfall of our third system
of sea-coast defences.

The period since the close of that war has been prolific in great
advances in the means and methods of attack. The iron plating
of ships-of-war has been increased from four inches to twenty-
five inches on the English ship Inflexible, and when a practicable
limit as to the thickness of iron plates seemed reached, compound
armor and all-steel plates were introduced. Recent British ships
carry eighteen inches of compound armor, and the Admiral
Baudin and Formidable of the French navy are protected by
solid steel plates twenty-one and seven eighths inches in thickness.

Heavy ordnance has increased in weight and power to a like
extent. Whereas in 1862 our 2OO-pounder Parrott rifle was one of
the most effective weapons extant, we have, in 1872, the English
I7f-inch, loo-ton gun, firing a projectile weighing one ton with a

* Oct. 17, 1855. The three floating batteries (Devastation, Lave, and Tonnante)
were protected by iron plates each three feet long, twenty inches wide, and four and
one half inches thick.



4 OUR SEA-COAST DEFENCES.

powder charge of 550 pounds, and in 1884, the i6^-inch, no-ton
Armstrong, which fires an i,8oo-pound projectile, with the enor-
mous charge of 900 pounds of powder, giving a muzzle energy of
61,200 foot-tons, and a penetration of over thirty inches of wrought
iron at 1,000 yards. The recent Krupp I5|-inch steel gun weighs
119 tons, and penetrates 29.2 inches of iron at 1,000 yards; and
the projected French gun is to weigh 124 tons, with a calibre of
1 8. 1 1 inches, and to fire a projectile weighing 2,645 pounds, with
a powder charge of 575 pounds.*

Important improvements in the manufacture of powder have
greatly increased the power of heavy ordnance. The grains have
been made larger and denser, so as to burn more slowly and to
diminish the initial and dangerous strain on the gun. Grains of
uniform size insure uniform results, and perforated prismatic
grains give increasing surfaces of combustion, and hence increas-
ing volumes of gases during the movement of the projectile in the
bore. Where we used a 35-lb. charge for the 1 5-inch gun during
the war, we now use 130 Ibs. " Cocoa " powder, so called from its
color, is now superseding all other varieties for heavy ordnance.
The grains are dense hexagonal prisms about one inch long, and
one and a third inches across the hexagon, with a cylindrical per-
foration about one third of an inch in diameter. Its method of
manufacture is still a secret, but it is said to light with great
regularity, burn very slowly at first, and then with tremendous
rapidity. It is claimed that this powder gives less smoke than
any other variety, an important point when we consider the heavy
charges now used with sea-coast ordnance. It is rather a striking
fact that a six-gun field battery of three-inch rifles, firing two
rounds per minute from each gun, would, in an hour and a
quarter, only consume as much powder as is fired in one round
from the I lo-ton gun. The impenetrable veil of smoke surround-
ing a sea- coast battery after even a single discharge from its heavy
guns will, at times, be a great obstacle to accurate fire, and will
make well-scattered works a necessity.

To insure the complete combustion of such large charges of
slow-burning powder, guns have been gradually increased in
length up to the present limit of 35 calibres.

Important improvements have likewise been made in the
manufacture of projectiles. One measure of the efficiency of a
gun is its power of penetrating a wrought-iron plate at a dis-

* See Table I. Modern Heavy Ordnance, page 5.



SEA-COAST DEFENCES.



p

p^

w O



_ A ooo'i ;B uoji

iqSnojAV josaipui

ui i uop^ajguaj



'unS jo
uoj aad



unS jo



saipui ui



suoj ui unS
jo



ha
1



O CO M CM CO

^f O co C^ co



coOOcocoOM ^W O-fOO r^o

Oco -rr>.-HO '-H O MO r^cocoooco
-



M M cOvOOcoOvO



O oo xoco OMxn
Tj-como IN COM
O r^oooco t^>



<O r^ >-t oco
M <-T M" M"



O co r^ ci co r coo
oT *-T i-T i-T



OOvr>
o COM



O <N ^ 1-1 u->



OCOO-^OdMCO



MOOoO\r>O<NO
co" o" ^f coo" r>- r - . o* 1



O O
"? .
co <N



O u"> m



co 1-1 coo cooo>-<



W



M



w



o



6 OUR SEA-COAST DEFENCES.

tance of 1,000 yards. The shot is the medium through which the
power stored in the powder is rrrade effective on the plate ; and
the energy of the projectile depends directly upon its weight and
the square of its velocity. Every foot-pound of this energy which
is expended in distorting or disintegrating the shot itself is so
much wasted work, and in these days of armor plates of tremen-
dous resistance the necessity of having a perfect projectile
becomes more and more apparent. Cast-iron shots were
replaced by chilled iron years ago, and now forged steel has
come to be regarded as the best material that can be used
against armored ships or forts. The manufacture of steel projec-
tiles has been carried to the greatest perfection in France, Ger-
many, and England, and their great tenacity has been demon-
strated on many occasions.

To give a single instance: In August, 1883, Sir Joseph Whit-
worth, in testing a 2O-ton steel gun intended for the Brazilian
iron-clad, Riachuelo, fired a 4O3-lb. steel shell through eighteen
inches of wrought iron, thirty-seven inches of well-packed wet
sand, one and one eighth inches of steel, various balks of timber,
and about sixteen feet more of sand. The projectile was recovered
practically uninjured.

Against hard armor, however, such as cast iron, steel, and
compound, the superiority of steel projectiles is not so marked.
This point will be discussed later on.

As to the results of these successive improvements : The
ratio of the weight of the powder charge to the weight of the
projectile has increased from about \ in the loo-ton gun of 1872, to
J- in the no-ton gun, and to nearly unity in the iQ-ton Woolwich
wire gun of 1884; the calibre of the heavy Armstrong guns has
diminished from i/f inches in 1872 to 17 inches in 1882, and to
\6\ inches in 1884, yet the weight of the gun itself has increased ;
the initial velocity has increased from less than 1,700 f. s. to over
2,000 f. s., and the muzzle energy has been nearly doubled in the
past twelve years.

Recent experiments have demonstrated the entire feasibility
of firing shells containing nitro-gelatine bursting charges. Up
to the present, such trials have been limited to six-inch shells
holding about eleven pounds of nitro-gelatine; but there is
manifestly no limit as to their use for curved fire with reduced
powder charges, and it is highly probable that in future wars we
shall have to encounter horizontal fire of this nature from the



OUR SEA-COAST DEFENCES. 7

heaviest guns. The development of this use of high explosives
seems to rather favor the attack, and for distant bombardments it
will be found most effective.

As regards the so-called dynamite guns, in which compressed
air is used as the propelling force, while they may be found
economical and even highly effective for certain purposes, their
use against iron-clads will be very limited. Their penetrative
power is slight, the range is limited, and it will be found very
difficult, if not impossible, to throw charges of sufficient size to
seriously affect side armor of moderate thickness. The gun is of
great length and fires at high angles of elevation, which makes it
difficult to secure good cover. No one supposes, nor does the in-
ventor claim, that dynamite guns can ever replace heavy ordnance.*

The Gatling, Nordenfeldt, Hotchkiss, and other machine guns
now constitute an important part of the armament of every man-
of-war. Some of these guns are mounted in the tops, the gunners
being protected by steel or iron shields, and in this commanding
position their fire is extremely destructive when directed upon
barbette batteries of low command. It is said that two of the
Egyptian batteries at Alexandria were practically silenced by the
fire of machine guns alone.

The number of iron-clads has, of course, greatly increased.
Whereas England had but four such ships in 1861, she now has
fifty-seven ; and the six ships possessed by France in the same
year have been increased to thirty-eight.

Such has been briefly the progress of the attack. Let us now
see what we have been doing for our defences.

Soon after the close of the war, experiments were instituted to
determine the best method of ameliorating our existing masonry
forts to adapt them to the new conditions of sea-coast warfare.
These finally culminated in the destruction of the Fort Monroe
and Fort Delaware experimental casemates in the fall of 1868.
The object sought was to increase the resistance of that portion
of the scarp immediately surrounding the embrasure, which was
necessarily the weakest portion of the wall. Substantial iron
embrasure shields were tried, placed first, near the face of the
scarp, and secondly, on the interior. In the first position it was



* The 8-inch gun, now nearly completed, is 60 feet long, and will fire a 75-lb.
shell containing 125 Ibs. of nitro-gelatine. (Total weight, loaded, 200 Ibs.) It is ex-
pected that a 2,ooo-lb. pressure will give an initial velocity of 1,200 f. s., and a range
of two miles at an elevation of 30.



8 OUR SEA-COAST DEFENCES.

found that the transmitted shock of the projectile was sufficient
to detach fragments and splinters on the interior and in some
cases even entire stones, which were hurled across the gun
chamber to such an extent as would have endangered the lives
of any gun detachment had the casemate been so occupied. In
the second case the iron shield gave better protection to the in-
terior, but on the exterior the masonry was rapidly smashed to
pieces and the embrasure soon became choked by the debris.
Ultimately the entire wall between the piers was demolished and
the interior fully exposed. These experiments, while not entirely
satisfactory, plainly indicated the great difficulties which would
be encountered and the great expense which would be involved
in the application of iron armor to our masonry forts.

Recent experiments have shown that the Soton gun projectile
will penetrate twenty-five feet of granite and concrete masonry or
thirty-two feet of best Portland cement concrete, and it is now
universally admitted that no masonry should be exposed to such
fire ; but in 1868 the development of guns and armor was still in
its earlier stages, and the condition of our finances did not per-
mit of great outlays in experimental constructions. Earthen
barbette batteries were therefore provisionally adopted.

Our armament at this time consisted mainly of smooth-bores,
and for this reason the earlier works were built with slight com-
mand. Batteries were commenced in all the important harbors,
but work progressed slowly, owing to the limited annual appro-
priations, which fell to $725,000, in 1875, and then entirely ceased.
Since 1875 not one penny has been appropriated for the construc-
tion of sea-coast defences. The annual appropriation of $100,000
for preservation and repairs, increased to $175,000 since 1881, has
not even sufficed to preserve our unfinished works, and our defen-
ces are actually in a worse condition to-day than they were ten
years ago.

The fire of machine guns and small-arms, together with the
shell and shrapnel fire of the large guns and the greatly increased
length of modern breech-loading ordnance, have made the service
of barbette guns in low batteries an impossibility, and in batteries
with greater command so difficult as to be practically impossible,
without extensive modifications looking towards security of cover
for the cannoneers. The penetration of projectiles has greatly
increased, and it is now estimated that seventy feet of compact
sand, or equivalent thickness of other material, is necessary to



OUR SEA-COAST DEFENCES.



stop the heaviest projectiles at close range. Increased thick-
ness of parapets and traverses, bomb-proof shelters for relief
detachments, thoroughly protected magazines, good shelter for the
cannoneers, and arrangements for depressing carriages must all be
made before our batteries can be considered as even ready for
modern armaments.

TABLE II.

APPROPRIATIONS FOR FORTIFICATIONS SINCE 1866.



Year.


Appropriation.


Object.


Year.


Appropriation.


Object.


1866


$1,495,000


For construction,


1876


$IOO,OOO


For protection,


1867


1,080,000


preservation, and re-


1877


100,000


preservation, and


1868


200,000*


pairs, including pur-


1878


IOO,OOO


repairs.


1869


200,000*


chase and surveys of


1879


100,000




1870


1,311,500


sites.


1880


100,000




1871


I,627,5CO




1881


175,000




1872


2,037,000


* Contingencies of


1882


175,000




1873


I,579,OOO


fortifications.


1883


175,000




1874


7I9,OOO




-1884


175,000




1875


725,000




1885


100,000




Total.


$10,974,000


For construction.


Total.


$1,300,000


For repairs, etc.



Insufficient appropriations have also retarded the development
of our heavy ordnance, and while other nations have been making
great progress in this respect, we, at the present moment, do not
possess a single modern rifle.* For the defence of our entire coast,
we have only the following armament : (i) About 1 50 f 8-inch rifles
which have been converted from the old lo-inch smooth-bores.
These guns fire projectiles weighing 180 Ibs. with 35 Ibs. of
powder and can penetrate 8 inches of iron at 1,000 yards. (2)
About 310 15-inch smooth-bores. (3) A considerable number of
smooth-bores of smaller calibres and some cast-iron Parrott rifles.
(4) One modern 1 2-inch rifled mortar and a number of smooth-
bore 10- and 13-inch mortars. It has been proposed to convert
the 15-inch Rodmans into I i-inch breech-loading rifles, and several
have been so converted, but I believe this' project has been
abandoned since the Sandy Hook experiments of 1883 showed
that this gun, when fired with 130 Ibs. of hexagonal powder and a
steel or chilled cast-iron projectile, gave an initial velocity of 1,676



* Several modern steel rifles of 8- and 6-inch calibres are now being constructed,
but none are as yet completed ; naval guns are of course not included.
f Fifty more are now in progress of conversion.



10 OUR SEA-COAST DEFENCES.

feet and a penetration of 10 inches of wrought iron at 1,000 yards.
The shortness of the gun makes it difficult to completely con-
sume a large powder charge, and the shape and size of the projec-
tile cause its velocity to diminish rapidly with the distance ; but
still the results given above show that the 1 5-inch smooth-bore as
well as the 8-inch rifle are useful as subordinate weapons. We
cannot, of course, depend upon them alone ; a modern iron-clad
could lie beyond their effective range and destroy such works as
we have by piecemeal, dismount our guns, and drive away our
gunners.

Although appropriations have been made for the construction
and testing of various experimental guns, and boards have been
constituted whose labors have resulted in the accumulation of
much useful and important data, and whose reports have con-
tained urgent and specific recommendations, Congress has thus
far taken no decided action toward providing a suitable armament
for our sea-coast defences.

As the Italians were fourteen and one half months in con-
structing their first loo-ton gun, and the English took sixteen
months to build their first 8o-ton gun, it would seem the part of
wisdom to begin the purchase or manufacture of our heavy ord-
nance at once.

In one respect only have we made satisfactory progress. Our
system of fixed torpedoes has been gradually developed by ex-
periment and practice, and is now at least equal to any in the
world. Plans for the torpedo defence of every important harbor
have been prepared and filed ready for use, and torpedo cases,
anchors, and such heavy and imperishable parts of the apparatus
are being gradually .stored in the various works where they are
needed. Electrical operating-rooms, with shafts for submarine
cables, are being prepared as rapidly as the yearly appropriations
permit, and the torpedo corps (Engineer Battalion at Willets
Point) has recently been increased to 400 men.

But it should be remembered that torpedoes are of little
value without adequate land defences, and in this respect we are
lamentably deficient.

For a number of years past careful experiments have been
carried on at Willets Point with the Sim's electrical fish torpedo
a type of the offensive class. These torpedoes can be con-
trolled and steered from the shore while travelling at a speed of
from ten to twelve miles an hour, have a range of two miles, will



O UR SEA-COAST DEFENCES. 1 1

penetrate or dive under any ordinary obstruction, and carry
charges of four hundred pounds of dynamite, which can be ex-
ploded at will or by contact. Weapons of this class should be
provided as auxiliary defences of our harbors, but at present we
have but the single experimental one.

Such is briefly the history of our sea-coast defences, and such
their condition to-day. " With old casemated works designed
long before the introduction of the 800- to 2,ooo-pounder rifled
guns into modern warfare ; their walls pierced for guns long since
out of date ; without iron armor or shields, and but partially
armed, even with the old ordnance ; with old earthworks, some of
them built in the last century ; with new ones for modern guns
and mortars but partially built, and rapidly being destroyed by
the elements by reason of their incompletion ; with gun batteries
without guns, and mortar batteries without mortars ; with no
carriages whatever for barbette guns of large size, except such as
require the cannoneers to load from the tops of parapets, from
which they can be picked off in detail by the enemy's sharp-
shooters ; we can make but a feeble defence." * There is not a
harbor on our coast that cannot be captured with comparative
ease by an iron-clad fleet properly armed and equipped ; there is
not a single important power in the world which does not possess
such a fleet.

PART II. NECESSITY FOR SEA-COAST DEFENCES.

The great increase in cost of war material during the past
century is most striking. In 1873, the British navy included
about 118 actual sea-going line-of-battle ships, representing a total
original outlay of about twenty-two millions of dollars or $187,-
ooo per ship. Now England has only fifty-seven sea-going armored


1 3 4 5 6

Online LibraryEugene GriffinSea-coast defences → online text (page 1 of 6)