Henry L. (Henry Larcom) Abbot.

Hasty notes relating to military engineering in Europe : mad in the autumn of 1883, submitted to the Chief of Engineers online

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Online LibraryHenry L. (Henry Larcom) AbbotHasty notes relating to military engineering in Europe : mad in the autumn of 1883, submitted to the Chief of Engineers → online text (page 1 of 2)
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Fabrication of Compound Armor, Cammell & Co 5

Fabrication of Compound Armor, John Brown & Co 6

Fabrication of Forged Steel Armor at-foj Cr^u^ot 7

Masonry Targets at Shoeburyness ..'...'.' 8

The Dover Turret for two So-ton guns 9

Engineer Establishment at Chatham 1 1

Electrical Crane at Bourges 13

Danish Submarine Mines 14

Torpedo Cable 15

Torpedo Boats in Europe .15

New Organization of Engineer Troops in Russia 16


November i, 1883.
Brig. Gen. H. G. WRIGHT,

Chief of Engineers, U. S. A.,

Washington, D. C.

So far as my duties as a member of the Gun Foundry Board would allow, I took
advantage of my recent visit to Europe to obtain all possible information respect-
ing matters of professional interest to the Corps of Engineers.

Some matters were communicated confidentially thus I was permitted to in-
spect the new iron defenses at Cronstadt, but with the request that nothing should
be made public ; and I was shown some recent improvements in the English sub-
marine mining service, which, although no conditions were imposed, I judge
more fitting for a confidential paper to be printed here for our own use.

Other matters were of a general character with no such restrictions as to pub-
licity, and during the return voyage I have hastily thrown my notes into the form
in which I now transmit them. Of course matters pertaining to the special duties
of our Board are not included.

The Board was everywhere received with great courtesy; but I feel under obli-
gations personally to Major General Sir A. Clarke, Inspector General of Fortifi-
cations ; Colonel E. D. Malcolm ; Lieutenant Colonel W. Grossman ; Major R.
H. Vetch ; Major R. G. Armstrong; Major M. T. Sale; Captain F. R. de Wolski ;
and Lieutenant G. A. Carr, all of the Royal Engineers, and to Captain A. Van der
Howen of the Russian Artillery Guard.

Very respectfully, your obedient servant,

Lieut. Col. of Engineers, Bvt. Brig. Gen., U. S. A.


The Gun Foundry Board, of which I am a member, witnessed the fabrication of
compouftd armor both by the Wilson and by the Ellis patents ; also the forging
and tempering of steel armor at Le Creusot. As these matters hardly come within
the scope of our official report, the following brief account may be of interest:


This establishment manufactures compound plates under the Wilson patent, as
is also done at St. Chamond, and by Marrel Freres in France. We saw at Shef-
field a plate ordered for the Italia and made by this process, which was igX
inches thick and weighed 50 tons. The one we saw manufactured was not quite
so large, being only 18 inches in final thickness.

The wrought iron backing was intensely heated in the furnace when first seen.
It had been previously formed by the usual process of rolling. Six plates, each
4 inches thick, had been thus prepared, and they were now to be rolled into a sin-
gle one 1 8 inches thick.

An iron box mould was ready, lined with a fire-proof coating. In length and
width it slightly exceeded the dimensions of the proposed compound plate, but
in thickness it was exactly the same. This mould, open on one side, was provided
with trunnions, so that it could easily be revolved from a horizontal to a vertical

The furnace doors were thrown open, and the white hot mass was drawn down
and quickly entered between the rolls, which were of the most massive character.
During its reduction from 24 to 18 inches in thickness, care was taken to remove all
oxide scales by scrapers and by jets of water.

After the completion of the rolling, the plate still intensely heated, was run on
its truck carriage to the mould, slid in horizontally, and wedged in position by iron
strips and moulding sand at the ends. The mould was then revolved to a ver-
tical position, leaving an open space of 10 inches on one side of the plate for the
reception of the steel. Over the top of this space was placed a long receiver,
pierced with ten holes. Two ordinary ladles filled with fluid steel, prepared by
the Bessamer process, were moved up and so tapped as to discharge rapidly into
the cavity, soon filling it with the white hot metal.

We were informed that after cooling for two hours in the mould the compound
plate would be reheated in the furnace, and again rolled down to a thickness of
1 8 inches. After cooling the edges would be planed straight; the bolt holes would
be tapped and the plate would be ready for delivery. We saw samples at various
stages of these operations, and in all the union between the steel and iron ap-
peared excellent.


At this establishment the armor plates are manufactured under the Ellis patent,
the essential difference being that the face is formed of a hard rolled steel plate
cemented to the wrought-iron backing by a fluid layer introduced between them.

The largest plates weigh 50 tons, being 2o / Xio / X'io // , or other equivalent di-
mensions. The weight fixes the limits as to size. We saw one 22 / X9X / Xio //
actually manufactured. This plate consisted of a 1 2-inch wrought-iron plate and
a 4-inch steel-plate, separated by a space of 4 inches. This space was preserved
by five rows, each of 8 steel pins, and by flanged side and bottom strips (mostly
to be subsequently cut off). A clutch hold was prepared by a mid-top strip of
like nature. ^

After carefully covering all exposed steel surfaces with gannister brick to pre-
vent melting or oxidation, the mass was placed in a rcverberatory furnace, and
brought to a white heat. It was then drawn out, the bricks were removed* and an
ingenious clamping clutch was adjusted to the top, so that the mass could be raised
vertically and lowered into a sunken iron moulding pit, one side of which was
movable by hydraulic power. This side was forced up against the steel plate,
holding the whole firmly in place.

The space between the iron and steel was then filled with fluid Bessamer steel
poured from a ladle into a top receiver pierced with several holes. When full
the whole was covered with moulding sand and weighted with a heavy mass of

After cooling about two hours the mass would be reheated and rolled down to a
thickness of 10 inches, the ends and sides would be sawed off hot or planed off
cold, and the bolt holes would be tapped into the wrought-iron backing.

Several plates completed and in progress were examined. They showed dis-

tinctly the three kinds of metal composing them. Indications of bad union were
very few and small in extent. Where small plates are ordered, for economic
reasons they are made by cutting large ones.

The largest plates cost from ^85 to ^90 per ton, there being no difference in
this respect between the two processes of manufacture, nor does there seem to be
any marked difference in the quality of the work done under the two patents.


The armor-plates manufactured at this establishment are of cast steel made by
the open hearth process, forged under the loo-ton hammer, and tempered in oil.

The largest size is 60 centimetres thick, 3 metres wide, and of sufficient length
to weigh 40,000 kilos. Such a plate would require a 75-ton ingot, the loss being
chiefly in the sinking head. We saw many 40 centimetre plates now making for
the French navy. The price delivered at Havre, if the plates were ordered of
complex forms (as for ships) would be I T % francs per kilogram if flat it would be
less. They are, therefore, cheaper than compound plates at present.

We witnessed the process of casting an ingot, forging a plate, and tempering
one in oil.

Seven Siemens furnaces are arranged, three on one side and four on the other,
of a double railway track leading to a deep pit containing the flask. The capacity
of each furnace is 15 tons, giving the power of casting an ingot exceeding 100
tons in weight. In front of each is an hydraulic turn table, which can be lowered
below the floor a dozen feet or more, and revolved at pleasure. Railway cars
carrying ladles are placed in front of each furnace on these tables, and are filled
and then run over the flask in succession by a locomotive. Here they are tapped
from the bottom, the flow being led into the bottom of the flask. Three ladles
were used in casting the ingot (45 tons) witnessed by us, and the total time was
thirty-three minutes. Care was taken to keep the flow uniform throughout.

All these armor-plates are forged by the loo-ton hammer, the largest in the
world. The ingot we saw treated (75 tons) had been heating about forty hours.
We were informed that it would be reduced in thickness from 1.4 metres to 0.55
metres by about a dozen successive hammerings, requiring ten days in all. The
area of the face of the tup was about 6 / Xi / -5 = 9 square feet; its weight was 100
tons ; and its fall was 5 metres, or less as desired. The porter bar for moving the
ingot was a massive iron beam about a square foot in cross section. It served
both to direct and to counterpoise the ingot, the hold of the crane being adjusted
to effect .the latter object. To prevent the vibration from breaking this huge por-
ter bar, it had been warmed by suspending fires under it.

When the crane took the weight, a crowd of men with bars engaged in square
nuts slipping on the beam, directed the white hot mgot under the hammer so that
the blow would fall on one side, and near the sinking head end. After a few pre-
liminary aims the blow fell, then another harder, and then a couple from the full
height. The concussions were tremendous, and an indentation about 6 inches deep
and the full size of the head was made about two-thirds across the plate. The lat-
ter was then drawn back, and a similar dent was made by the side of the first.
This operation was repeated until the forging extended to the end of the ingot.
The remaining third was next treated in the same manner, reducing the whole to
a uniform thickness of about 4 feet. The end showed two slight bulges, the lines
of greatest extension being about a foot above the bottom, and a foot below the
top. The action of the hammer evidently extended to the middle of the mass, but


not quite so effectually as at points nearer the seat of the blow. The spectacle of
this forging was grand beyond words, especially as seen at night by its own light.

The tempering was done in an immense iron tank half raised above the bottom
of a pit 15 metres deep. It contained 180 tons of colza oil. The plate was
brought to a dark red heat in a special furnace, also in the pit. The plate stood
vertically on one edge, and the side walls of the furnace formed wide flues on
each side for the passage of the gases and flame from six grates near the bottom
(three on each side). The draught was through the top cover.

When the requisite temperature was reached the top was removed, and the
ends were thrown open. A traveling crane was run over the plate and hooks
were engaged under the ends. The whole was moved over the tank and the
plate was lowered quickly into the oil, which at first boiled furiously. We were
informed that it would remain submerged about four hours. Mention was made of
subsequent annealing, but no definite information was given.

It is impossible to witness the manufacture of one of these immense plates
without being impressed with the thorough manner in which all the processes are
carried out at Le Creusot.


The most important object of my vist here was to examine the targets, still
in position, designed to determine the best method of strengthening masonry
against modern ordnance. The following statement is chiefly based on what I saw
and was told on the spot.

The end proposed in the firing was to learn the power of the So-ton gun, loaded
with 450 pounds of powder and a chilled projectile of 1,700 pounds weight, and
fired at a range of 200 yards, giving a striking velocity of about 1,580 feet per
second, and an energy roughly of 30,000 foot-tons, upon masonry resembling
that existing in many British reinforced sea-coast defenses. The target was a solid
granite wall 14 feet high and 9 feet thick, backed with 6 feet of good Portland
cement concrete, and faced in rear by a wall of brick 5 feet thick, the whole
forming a substantial mass 20 feet thick and about 80 feet long. Against its left,
and upon the same line, was placed a mass of Portland cement concrete to serve
as an end buttress, and also to receive one shot. Its height was the same as the
rest of the target ; its length was 30 feet ; its thickness about 40 feet. About
25 running feet of the right of the target was reinforced at the back by a mass
of concrete to the same depth, and the middle was supported by an earth embank-
ment similar in mass. This target was constructed between October, 1882, and
March 31, 1883, and the firing was done during the past summer and autumn,
z. <?., before the concrete could have fully hardened. Immediately over the plates
to be tested, an attempt was n*ade to increase the stability by weighting the top
with old armor-plates, but this was not done elsewhere.

The first shot (August 21) struck the masonry on the right where it was without
any protection. It penetrated the granite and concrete to the brick wall, which
deflected it to the right, and finally to the front, so that the projectile came to rest
in a reversed position after traversing about 25 feet. The hole as seen by me
was large enough for a boy to enter, and the masonry around it was somewhat
cracked, but not very seriously. The shot broke up.

The second shot (September 11) was fired at a 12-inch compound plate, 7 feet
by 7 feet, made by Cammell Co. (Wilson's patent), and secured directly to the
masonry without any elastic backing. It was bordered by an iron frame. The


shot penetrated the plate, bulging the back into the granite, and showing its point
entirely through the iron, although fast in position. The rear of the shot broke
up. The blow upon the granite fell on a vertical joint between two blocks, both
of which were badly shattered throughout their whole extent. The indent was
about 6 inches. The lower edge of the next course above resisted the shock so
well that the wrought iron projection was pressed into a flat shelf at right angles
to the plane of the plate, and about 3 or 4 inches wide. In fine, the injury to the
masonry in this case was insignificant.

The third shot (September 1 1 ) was fired at a wrought iron shield, 12 feet by 7 feet,
composed of two 8-inch plates separated by 5 inches of wood and backed by same,
t. <?., of 1 6 inches of iron and 10 inches of wood. Six Palliser bolts held the plate
to the granite. The shot penetrated the shield and granite, and rested at the con-
crete just behind it going, say 10 feet in all. The hole through the shield was
sheathed by the iron forced back, and that in the granite was larger than the shot.

The plate covered so much of the face of the granite that the local extent of the
cracks was hidden ; but a few appeared beyond its border, chiefly radial. The
shot broke up.

The fourth shot (September 20) made a hole 32 feet deep straight into the con-
crete, which nearly closed the opening. The mass was badly cracked, and quite
a large surface had fallen down around the point of entrance. Considerable fir-
ing was witnessed by me at Shoeburyness, but it had no special interest with one
exception. This was the practice of an 8-inch rifled howitzer of 70 hundred
weight firing shells weighing 180 pounds at a siege battery constructed in the
marsh at a distance of 500 yards. The howitzer was fired over the parapet which
completely covered it, being pointed by sighting back at a target placed in rear.
The gunner placed his eye in front of a rimbase sight, and brought the rear sight
into line. Five shots were made, and they all fell with great precision into the
battery serving as a target passing over and dropping quite near the crest.


I was permitted to examine this work in detail. The following points were of
interest, in addition to what I already knew from the writings of Colonel Inglis,
Royal Engineers.

The turret forms at present the end of the breakwater; but it is proposed to ex-
tend the latter with a view to enlarge the harbor. If this be done the turret will
be left inside the line of the work, which its position on a sort of return will facil-
itate. The sea side of the breakwater is raised into a parapet against the waves,
serving to protect a passage-way on the harbor side ; and this passage-way ex-
tended under the return at the end forms the entrance to the work.

Ordinary high-water at Dover is 19 feet above ordinary low-water; the extreme
range being about 23 feet. In great storms the waves break over the entire
structure of the breakwater, and difficulty is experienced in keeping things dry
inside the turret. Once, before it was quite completed, the engines were flooded
and it was needful to send divers down into the room. This liability has caused
some of the peculiarities of the construction.

Advantage is taken of the horizontal space afforded by the breakwater. Thus
the magazines are not crowded under the turret, but are at some distance laterally,
and the engine-room is placed so near the harbor side as to permit high win-
dows for light. The reference of the magazine floor is that of ordinary high-
water, and the engine-room floor is 4 feet lower. The engines are placed in a


water-tight iron caisson, forming the floor and sides of the room. The magazines
are lioed with asphalt throughout, but I noticed marks of leakage on the walls
and dampness everywhere. There are two magazines for powder, designed to-
gether to hold about 70 rounds. The explosive is stored in boxes holding 112
pounds each, four of them constituting one charge. The projectiles are kept in
other rooms. A passage-way with a railway track leads from the magazine to the
lifts, so there is no carrying by hand. The cars are small enough to just hold
their load ; and their bodies form the semi-cylinder, which, when raised to the proper
height, bridges the interval between the depressed muzzle of the gun and the
head of the chain-rammer. This arrangement renders the loading by steam-
power rapid and comparatively simple. It involves the revolving of the turret
always to a fixed position, and the depressing of the gun to about 16 below the

The engine, which revolves the turret works the lifts and chain-rammers and
in fact does all the hard work required for operating the two 8o-ton guns, is of 200
horse power.

The magazines and engines are separated completely by masonry. This in-
volves narrow and winding passages with occasional ladders, but probably habit
would accustom the gunners to use them. Indeed one is impressed with the care
which has been observed to reduce all dimensions to the minimum possible. The
guns fill the turret so completely that no space is lost, and yet they are of the old
short muzzle-loading pattern. Perhaps the explanation of what appears to be
rather unnecessary crowding, may be found in the fact that the turret was begun
with the intention of arming it with 38-ton guns. This reason was assigned for
the peculiar base-revolving arrangement (withdrawn inward from under the armor-
plating) which has been a standing cause for speculation to our officers. Certainly
in planning turrets for ourselves this one may be accepted as too small in every
respect for the most recent patterns of this calibre of ordnance.

The actual weight of the turret and guns slightly exceeds 1,000 tons the esti-
mate was 800 tons, but it has been increased. The weight rests on 32 steel cones
16 inches in diameter and 16 inches long, revolving on rails. The centre pintle
bears no weight. The mass of armor constituting the turret proper is held by fric-
tion alone upon a sort of independent carriage supported by these cones, the object
being to save the gearing from part of the shook caused by the impact of a pro-

The armor consists of three 7-inch plates, two 2-inch plates, and 6 inches of
wood total 25 inches of iron and 6 inches of wood. The embrasures show the
cross-section, there being no inner rings. The top is covered by about 2 inches
of iron, which is arched over each gun a little to give more space; and over the
breech is a lattice work. To point the guns the officer looks through a simple
hole in the top, through which he thrusts his head ; but this will be modified by a'
plated protection.

The glacis is of stone masonry covered with 2 feet of concrete on top. It
varies in thickness from 9 feet on the harbor side to a minimum of 23 feet on the
front. The plan of the turret being circular and of the masonry an irregular poly-
gon, the latter thickness is exceeded at most points. The magazines are covered
only by 23 feet of masonry granite faced, concrete filled, and brick backed, prob-
ably in about the proportion of the recent Shoeburyness targets. At no place is
there any surface armor over the masonry, and no projects have yet been sug-
gested for applying any. A provision, however, has been made to reinforce the

1 1

base of the turret against projectiles striking the top of the concrete near it. The
heavy armor extends only 2 feet below the glacis crest, leaving a free space of 7 in-
ches (which is closed against water by a cover secured to the turret). One 8-inch
plate is bedded vertically in the masonry, a few inches in front of the interior slope
on the exposed sides of the work. Its top appears at the surface of the concrete,
and it extends only a short distance down. About 2 feet outside and parallel to
this is a lo-inch plate, also vertical. Its top is at the reference of the bottom of
the other, and its bottom reaches the plane of the traverse plates on which the
cones revolve. In my judgment some radical changes will be necessary in this
mosonry glacis when the results of the recent Shoeburyness trials have been
fully considered. Indeed they were made for solving such problems.

It only remains to consider the mode of operating the turret. This is controlled
by an ingenious system of signals from the officer above to the engine-room. At
the latter place is a dial-plate like the face of a clock, showing azimuths. Two
indices revolve on it. One is moved by the revolution of the turret, the other by
gearing under control of the officer above. The officer adjusts his sights on the
object and keeps them there, while the person in charge of the engine works
the gearing until his index comes under that of the officer. An electrical bell
continues to ring until all is right, being started by the officer when he is ready to
begin pointing. A speaking-tube is also available for his use.

This system was tested practically for the first time a few weeks before my visit.
Each gun was fired five times, some with half and some with full charges. Every-
thing worked satisfactorily except in one respect. The recoil of the first gun
caused the turret to revolve about 10 inches, so that repointing was needful for the
other. This difficulty it is proposed to meet by a brake.

Dover is strongly fortified against a land attack, as well as on the sea side. Be-
side the turret about thirty g-inch and lo-inch guns, in cliff batteries, defend the
harbor. I noticed one 7-inch gun mounted on a Moncrieff carriage, but the
others seen by me were behind earthern parapets very much after our own sys-


There were at my visit only about 85 Royal Engineers and 40 officers of other
branches of the service under instruction, rather less than usual. The course is
for two years, and includes theoretical as well as practical work.

The companies of enlisted men are largely instructed by non-commissioned


Online LibraryHenry L. (Henry Larcom) AbbotHasty notes relating to military engineering in Europe : mad in the autumn of 1883, submitted to the Chief of Engineers → online text (page 1 of 2)