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HENRY LILLIE PIERCE,

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Under a vote of the Presideat and Fellows,
October 34, 1898,

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MANUAL

iLiTARY Field Engineering

FOR TH£ 178B OF

OFFICERS AND TROOPS OF THE LINE.

PRBFARED AT THE

UNITED STATES INFANTRY AND CAVALRY SCHOOL

BY THE

Department of Ex(;ixeering,
Capt.

KFAKTMKN r OK IL N ( i I N KKRING,

Wm. IJ.^'beax^hTsrd Cavalry, Instructor.

THIRD EDITION

REVISED BY

} Capt. Wm. D. Beach, 3RD Cavalry,

\ First Lieut. E. A. Root, iqth Infantry,

- First Lieut. T. H. Slavens, 4th Cavalry.

august, 1897.
IB Hudson- K1MBER1.Y Publisuino Co.,
Kansas City, Mo.

LONDON :
W. H. ALLEN & CO., (Limited),

13 Waterloo Place, S. W.
Publishers to the India Office.

Bhtered accordiho to Act of Congress ih thb Year X897, by thb

hudson-ktmberly publishino cc, ih the office of thb

Librarian of Congress, at Washington.

PREFACE.

The necessity existing at the Infantry and Cavalry Sdhool
for a text-.book on Field Engineering, incluiling the various
military expedients recognized in our service, is deemed suffi-
cient reason for the following pages.

Most of the subjects treated of in this volume may be found
in various military works published in our country during the
past twenty-five years, but the fact remains that no one book
has covered the required groun<i, nor has their revision been of
very recent date; wliile, at the same time, the new field gun and
small calibre rifle have necessarily modified previously exist-
ing profiles of Field Works and Shelter Trenches.

Access has been had to corresponding publications of the
Germans, French, English and Austrians, as well as to our
own Official Rebellion Records and many other available
sources, native and foreign.

It has been the endeavor to limit the scope of this work to
subjects considered indispensable as a part of a line officer's
education.

The following Assistant Instructors in the Department of
Engineering— viz. : 1st Lieut. E. A. Root, 19th Infantry; 1st
Lieut. W. C. Wren, 17th Infantry, and 1st Lieut. T. H. Slavens,
5th Cavalry, have been associated with the undersigned in the
preparation of this volume.

WM. D. BEACH,
Captain, 3rd Cavalry.
U. S. Infantry and Cavalry School,

Part Leavenworth, Kansas, July, 1894.

U**aflr|uarters of the Army, Adjutan't-Generars Office,

Washington, March 25, 1896.
Circular No. 4.

With the approval of the Secretary of War, the special study
€f the books, pamphlets, orders, etc., hereinafter named, by
officera of the army subject to examinations for promotion, is
recommi^nded:

^ ■ * * * * 4t * «

Manual of Field Engineering— Captain W. D. Beach, Srd

Cavalry.

* * * * oo * «

By command of Lieutenant-General Schofield.

[Signed] GEO. D. RUGGLBS,
AdjwtanP-GmemL

PREFACE TO SECOND EDITION.

TMie cordial reception accorded the first edition of this bocA
has confirmed the revisers in their belief that a distinctively
Americam manual of military engineering will increase in pop-
ularity with both the army and the national guard.

Based mainly on data gleaned from a war which marked the
first extensive use of shelter trenches on the battle-field, and
in which a most important part was played .by what are usual-
ly termed military expedients, it is believed that this manual
sets forth clearly and concisely certain necessary facts and
methods, modified to fit modem requirements, which all officers
will be glad to have at hand for occasional reference.

W. D. B.
V, S. Infantry and Cavalry School,

4!\)rt Leavenworth, Kansas, August, 1897.

List of Books Consulted in the Preparation of this Work.

Aide Memoire, R, E Vols, i-2»

A Move for Better Roads L, A, Haupt.

Ap]3leton's Cyclopaedia of Applied Mechanics. Vols. 1-2,

Civil Engineering Wheeler.

Cours de Fortification Passag^re De Guise.

Ecole de Fortification de Canipagne French.

Elements of Field Fortification Wheeler.

Engineering News Magazine.

Engineer's Pocket-Book Trautwine.

Field Fortification Turner.

Field Fortification Hulchinson.

Field Works Brackenbury.

Field Works Used in War. (Translation

from the German) Wilson.

Good Roads Magazine.

Gun Powder and High Explosives Walke.

International Cyclopaedia Daddy Mead & Co.

Journal of the Military Service Institution

of the U. S.
Journal of the U. S. Cavalry Association.

Manual for Engineer Troops Duane.

Manual of Military Engineering Ernst.

Manual for Railway Engineers G. L. Vose.

Manuel de Fortification de Campagne Brialmont.

Manuel des Travaux de Fortification de

Campagne, par un CapJtaine d'Infanterie.

Manuel de P^ortification Plessix and LegrantU

Manual of Heavy Artillery Tidball.

Military Bridges Haupt.

Military Bridges Chester.

Military Engineering, Instruction in Chatham Course.

Military Transport Furse.

Modern Hi^h Explosives Eissler.

Notes on Military Hygiene A. A. WoodhulL

Official Records of the Rebellion, U. S .. . . War Department.

Organization and Tactics Wagner.

Pionier Taschenbuch, Berlin, 1893 Official.

Report of Chief Signal Officer, U. S., 1893. . War Department.

Roads and Railroads Chester.

Roads and Railroads Gillespie.

Roads, Streets, and Pavements Gillmore.

Temporary Fortification Chester.

The American Railway Scribner,

U. S. Bridge Equipage and DriU War Department.

WLJs.lSlZJJs.I^

MILITARY FIELD ENGINEERING.

CHAFTEB I.— General Principles.

1.— Military Field Engineering may be defined to be the art
of iitiliziDg the materials at hand for the attainment of the secur-
ity, effectiveness, health and comfort of an army in the field.

The modern rifle has vastly increased the value of cover, both
ill attack and defense, and rendered necessary the application of
ilie principles of fortification to an army in the field. The result
to be obtained in all fortification is to so strengthen a position, by
artificial means, that a force may successfidly resist or subdue
another.

2.— Fortification is divided into two general classes, viz.:

fa j— Permanent.

f'fe^— Temporary or Field Fortifications.

With the former this manual has nothing to do.

3.— The latter division includes three quite distinct classes.

The first comprises all works devised for the temporary protec-
tion of important points, such as cities, arsenals, bridges, fords,
positions, etc., and are technically known as Field Works.

8 General Principles.

The second comprises the various devices of the engineer for
reducing a fortified place by means of parallels and approaches,
called Siege Works.

The third division relates particularly to the quickly made
defenses by which an army in the presence of an enemy protects
itself; these are known as BaUlc Intrencfimcnts or Hasty Intretwh-
ments.

4.— A Defensive Position is one affording protection from
tlie shot and observation of an enemy and, at the same time, com-
manding the ground in front, within range.

A position of perfect defense is not possible, but the following
general principles are to be fulfilled as nearly as circumstances
will permit.

(1) The defenders' position should conform to the special tacti-
cal requirements of the occasion* and should be such as to favor
the use of their relatively strongest arm.

(2) It should be made impossible for the enemy to obtain nat-
ural cover during his advance. In other words, the position should
have a free field of fire.

(3) The defenders should be protected from the fire and view of
the enemy by cover so arranged as not to interfere with counter-
attacks.

(4) The advance of the enemy should be hindered by obstacles
so arranged that he may be checked while, under the fire of the
defenders.

(5) Communications should be such that the defenders may
freely move from one part of the position to another, while the
contrary should obtain with respect to the enemy's ground in
front.

The chief requisite of a defensive position is a free field of fire,
especially at short and mid ranges. If the position is judiciously
selected the field of fire will generally be obtained without much
diflaculty, but the advantages of the position and the effect of the
fire may be enhanced by temporary fortifications. The cutting
down of slight ridges which might afford cover for the enemy

♦A purely defensive position, forinstatife. might hav its anks resting rn im
passable obstac'es, and thus be secure from a turning movement, but this same
position t^ight be found to be a faulty one were a quick offensive movement, by
the defenders, contemplated.

General Principles. 9

within effective range ^r the removal of hedges, fences, etc., may
sometimes be of more benefit than the actual preparation of
defenses.

In the present advanced state of efficiency of fire-arms, artificial
cover is, however, of greater importance than ever before. Con-
structed in the right place, at the proper time, field fortifications
raay render indispensable service, while their neglect may Insure
defeat.

5. — ^While formerly it was the special province of the Engineer
to lay out and supervise the construction of defensive worlis, it
\\as now, under the changed condition of warfare, become the worlt
of the Line as well, and it may be laid down as an accepted rule
that the defensive arrangements for a given position are to be
made by the troops whicli are to occupy it.

These changes have affected the art in many ways. The field
works now constructed are simpler, ruder, less regular, and less
angular than before. An army in the presence of an enemy always
fortifies, whether in camp, in bivouac, or in line.

6.— Kapidity of execution renders necessary the adoption of
fixed types of worlvs in the exercises in time of peace; but these
types will sometimes be susceptible of modification in their real
application. However, even in war, the endeavor should be to
approximate to the regulation forms, for they are deduced from
experience and observation, and realize, as well as possible, for
each particular case, the best conditions of resistance compatible

with rapidity of execution.

The advantage of regulation types is understood at once when
it is borne in mind that, upon the battle-field, there should be no

hesitation; everyone should sticli to his individual role in order

to unite efficiently in combined action.

Thorough study and frequent practical exercises, conducted

methodically, are indispensable in order to escape feeling one's

way, with t-he loss of time that an insufficient instruction renders

inevitable. Upon the battle-field a few minutes may decide the

fate of armies in each other's sight.

7.— Fortification, which at first glance may appear to dominate,
as representing the "security" and "effectiveness" of an army,

10 General Principlea,

the other and apparently less important su\?jects relating to health
and comfort, is, however, so intimately connected with them tbat
neglect of one may render all the others useless. Thus, ^'bridges,'*
"roads," and "railroads" may, under certain conditions, relate par-
ticularly to the effectiveness and security of an army, in con-
nection with Fortification, while under other circumstances they
may be as important as various "camping expedients" in the
attainment of "health" and "comfort."

CHAPTER II.— Fire, Projectiles and Penetration.

8.— Fire as regards its direction is classified as follows:

(1) Frontal, when it is delivered at rifclit angles to the front
of the enemy's line, and sometimes so termed when delivered
straight to its own front.

(2) Oblique, when the direction of the fire is at an oblique angle
to the front of the enemy's line.

(3) Enfilade, which is delivered from positions on the prolon-
2:ation of the enemy's line. In this case, the line of fire sweeps
the enemy's front. When fire is useil to sweep along the front of
a defensive line and thus enfilade the assailants as they approach
the position, it is known as flanlving fire.

(4) Beverse, when delivered so as to strike troops or lines of
defense from the rear.

(5) Cross, when the lines of fire from different positions cross
on or in front of the enemy's line.

As regards its trajectory it is classified as

(1) Direct, when delivered at seen objects at moderate angles
of elevation— in the case of artillery when delivered at seen objects,
with service charges at elevations not exceeding 15°.

(2) Indirect or Curved, when delivered with small-arms against
an unseen object protected by a seen covering obstacle— in the case
of artillery, as above, or with guns, howitzers or mortars with
reduced charges at angles not exceeding 15°. Thus firing over an
intervening hill at troops sheltered behind it would be an example
of indirect fire.

(3) High Angle, when used at angles exceeding 15°.

(4) Grazing, when the projectile travels approximately parallel
to the gi'ound.

9.— The Artillery Projectiles used in the U. S. Army are shell,
shrapnel and canister.

12 Fire, Projectiles and Penetration.

Shell.— Shell may be classified as common shell and torpedo
shell. The common shell is "a hollow cast-iron or steel cylinder
with an ogival head closed at one end and filled with powder."
The torpedo shell Is filled with gun-cotton, or other high explo-
sive. Either shell may be characterized as a flying mine, the
chief object of which is to destroy material objects at a distance,
though the common shell may also be effectively used against
troops.

10.— Shrapnel differs from common shell in being filled with
bullets, and having only a sufficient bursting charge to rupture
the envelope and release the bullets, which then move with a veloc-
ity which the projectile had at the moment of bursting. The bul-
lets are assembled in circular layers and held in position by "sep-
arators," which are short cast-iron cylinders with hemispherical
cavities into which the bullets fit. The shrapnel for the 3.2 inch
gun contain 162 bullets Yj in. in diameter, and weighing 41 to the
lb. The total number of bullets and individual pieces in the shrap-
nel is 201.

11.— Canister, which is practically obsolete, is made of sheet-
iron or tin in the shape of an ordinaiy can, and is filled with bul-
lets held in place by filling the interstices between the bullets with
saw-dust, sulphur or rosin; the can is ruptured and its contents
dispersed by the discharge of the piece.

12.— The charges in the shell and shrapnel are exploded by
means of a combination fuse; by combination fuse is meant one
that may be arranged to explode the charge either on impact, by
percussion, or at a given time by certain arrangement of the parts
of the fuse.

13.— Field Guns range up to 6000 yds., but will be seldom used
at a range greater than 2500 yds.

14.— The U. S. Magazine Rifle, when used as a single loader,
has fired 21 aimed shots in one minute, and when used as a maga-
zine rifle, 23 shots in one minute; its range is over 3000 yds. and it
is sighted to 1900 yds.

The average heights over which fire may be delivered are as
follows: Man standing, 4 ft. 4 in.; kneeling, 3 ft.; lying down, 1 ft;
field guns, 3 ft.

Fire, Projectiles and Penetration. 13

15.— The following thickness of material may be considered as
proof against small-arm projectiles at all ranges:

Sand .30 in.

'Boggy or turfy ground ' (50 in.

Gabion filled with earth 1

Sand bag well packed, header 1

" " " stretcher 2

Packed snow , 6 ft.

Soft wood 40 in.

Oak or other hard wood ; 24 in.

Grain sheaves piled ^ 10 ft.

Iron plate 7-1(5 In.

Steel plate % in.

Masonry 20 in.

Against field artillery.

Earth 10 to 13 ft.

Snow well packed 27 ft.

Masonry (for a short time) 40 in,

CHAPTER III.— Field Geometry.

16.— Before proceeding to that portion of field engineering
which involves geometry some of its simplest applications will be
explained.

17.— Slopes. The usual description of a slope is by a fraction,
the numerator being the height and the denominator the base.
Thus, in PI. 1, Fig. 1, the vertical height is 1-Gth part of the base,
and the slope is read as 1 on 6. In Fig. 2, the slope is G on 1.

18.— To lay out a Right Angle: First Method. Let A be a
point in the line BC, Fig. 3. Lay off from A the equal distances
AD and AE. With a radius greater than AD, and with D and E
as centers, describe arcs cutting each other at X. Join X with A.
Then is XA perpendicular to BC.

Second Method. Find a point such that tlie distances are in the
proportions of 3, 4 and 5: then will the angle included between the
two shorter sides be a right angle. Thus (Fig. 4) with chain or
tape measure the distance AD equal to 4 yds. Place one end of
tape at D, the other at A, pulling it out and making XD equal to 5
yds., XA equal to 3 yds.

Third Method. At extremity of line, as A (Fig. 4), assume any
))oint as C. Measure distance CA, set a stalie on line BA at a dis-
tance from C equal to CA, as D. Set a third stalie on line CD at X,
making CX equal to CD. Then will XA be perpendicular to
BA.

19.— To erect a perpendicular to a line from a point ^y^ithout.
I/et X (Fig. 5) be the point without, then, with X as a center, and
a distance greater than XA as radius, describe an arc cutting BC
at D and E. With D and E as centers, and with a radius greater
than DA, describe arcs cutting each other at Y. Join X and Y.
Then will XY be perpendicular to BC.

20.— To bisect a given angle. Let ABC (Fig. 0) be the angle.
With A as a center, and with any convenient radius, as AD,

PLATE 1

Figure 1.

Figure 2.

Figure 3.

S '.D

Figure 4

.'E c

b"^.* J k

Figure 5 .

..--'A

B D^ A

E C

A' C

' B

Figure 10

B C

Figure 11.
pA

Field Geometry. 17

describe an arc cutting AB and AC at B and D. With D and E as
centers, describe arcs cutting eacli other at X. Join X with A.
The line XA bisects the angle ABC.

21. — To lay out an equilateral triangle constructing adjacent
angles of 60° and 120°. I^t AB (Fig. 7) be a given line. Lay
off from B any convenient distance, as BE. Then, with B and E
as centers, and a radius equal to BE, describe arcs cutting each
other at D. Join D with p] and B. The angles DEB, DBE and
EDB are each equal to 00°. The angle AED is equal to 120°.
Combining this method with that of slopes an angle of almost any
number of degrees can be laid out.

22. — To lay out an angle equal to a given angle. Let X
(Fig. 8) be a point in the line AB, from which it is required to lay
out an angle equal to OEC. Fix the points O and C at convenient
distances from E. From X lay off XG equal to OE. Then, with
X and G as centers, and EC and OC as radii respectively, strike
ares intersecting at F. Join X and F. The angle FXG is equal to
the angle CEO.

23. — To draw a line parallel to a given line and at a given
distance from it. Let AB (Fig. 9) be the given hue. From any
two points, as C and D, erect perpendiculars. On these lay off the
required distance CE and DF. Join E and F.

24.— To find the distance between any two points when it
cannot be measured directly. First Method. To find AO, take
a point B in line with AO and from this point (Fig. 10) lay off any
convenient angle, as ABC. At D make EDC equal to ABC. Meas^-
ure BC, DC and DE, putting E in tlje line CO. From similar
triangles

BC X DE

BO : BC :: DE : DC ;•. BO =

From the result thus found, subtract the distance AB. The
remainder is the distance AO.

Second Method. (Fig. 11.) Mark B in prolongation of the line
AO. Assume any point as C. Lay off AF, making AC equal to
CP: also BE, making BC equal to CE. Prolong EF until a point
K is found in line with CO. Measure FK. This is the required
distance.

-2-

18 Field Oeometry.

25. — Areas. To find the area of a rectangle. Multiply the
base by the height.

To find the area of a trapezoid. Multiply the sum of the t^wa
parallel sides by the perpendicular distance between them and
take half the product.

To find the area of a triangle. Multiply the base by the alti-
tude and take half the product. Or,

Area = V^ (s— -a)"(8^^b) (8~~~c)~
in which s is the half sum of the three sides a, b, and c. Or,

Area = % a b sin C
in which a and b are two sides and C the included angle.

26.— The Field Level (PI. 2, Fig. 1) consists of three strips of
wood, A, B and C, each 14 in. thick and 2 in. wide. A being 62 in.
long, B and C each 44.42 in. The distance between centers on A is
60 in., on B and C 42.42 in. Tliis makes a right angle between B
and C. There is a thumb nut at E clamping the arm B to the arm
A when the level is used. The screw at F projects, holding the
arm B, when folded, up. There is a stud at II, affording an attach-
ment for a plumb bob. There are permanent joints between B
and C, and A and C.

¥\g. 1 shows the level and its joints, plumb bob for reading
slopes, and spirit level. Fig. 2 shows side for protracting angles.

27. — Uses of Level. The level may be used as follows:

(1) As a spirit-level, the level being on the edge C.

(2) As a square for setting out a right angle.

(3) As a protractor.

(4) For setting off slopes.

(5) As a mason's level with a plumb bob.

PLATE 2.

PLATE 3.

SHELTER TRENCH.

-LYINO.-

SHELTER TRENCH.

-KNEELINQ-

-iFTSifit.

SHELTER TRENCH.

- STAN DIN G.-

HEAD LOG ANb
IRUSH-WOOD LOOPHOLE

atelt9T

CHAPTER IV.— Hasty Intrenchments, Gun Pits and
Epaulements.

28.— The intensity of fire made possible by the fire-arms of
to-day renders some form of shelter on the field of -battle impera-
tive. Circumstances may occur when advancing lines of skirmish-
ers will find natural shelter, but in many cases artificial cover will
have to be constructed on the spot.

Fortifications used on the field of battle depend, as to their posi-
tion, extent and use, on the ground; in conformity to this idea
they are constructed at the time of the battle, and not before.

They are called ''Battle'' or ''Haatqf' Intrenchments, and should
fulfill the foUoTving conditions:

(a) The thickness of earth embankment should be such that it
will not be liable to penetration by small-arm projectiles or shrap-
nel fragments.

(b) The intrench ments should conform to the average heights
over which men can fire in the various positions,— viz.: lying prone,
1 ft.; kneeling, .3 ft; standing, 4 ft. 4 in.; and at the same time the
height of earth embankment above the natural surface of the
ground should be small, for the reason that the trenches can thus
be more easily concealed and are less liable to be struck by artil-
lery projectiles.

Hasty or Battle Intrenchments consist of cover for

(1) Skirmishers, lying, kneeling or sitting.

(2) Firing Ijine, Supports and Reserves, kneeling, sitting or
standing.

(3) Gun Pits and Epaulements.

29. — The shelter trench for skirmishers lying down is shown
in PI. 3, Fig. 1. It gives earth protection of a thickness of 2^ feet;
this thickness of loose earth will stop small-arm projectiles under
ordinary circumstances. The average time required by one man
to make 5 ft. (2 paces) of this trench is, with large pick and shovel,
Ky minutes; with small intrenching spade, 20 to 25 minutes.

The number of skirmishers that can use this trench is usually
computed as two for each five feet of length, although three may
occupy this space by lying partially on their left sides. In firing,
the left elbow rests on the berm.

30. — For men kneeling in two ranks, cover is gained by deep-
ening the trench already dug to 1 ft. 8 in. and making it 5 ft. wide

24 Hasty IntrenchmentSy Oun Pits and Epaulementa,

with an embankment in front liaving a lieiglit of 1 ft. 4 in. an<i a
resulting tliickness of about 5VL» ft. (Fig. 2.)

Tlie average time required by one man to transform 5 ft. of tbe
trencli "lying" into the trench "kneeling" is, with large pick and
shovel, 25 minutes; with small intrenching spade, 45 minutes.

Infantry in double rank kneeling can fire from this trench, the
number of rifles being computed at 4 for each 5 ft. length of trencli.
The kneeling trencli affords protection to men sitting, but hori-
zontal fire from this position is impossible. The step at a \srould
only appear in the converted trench.

31. — Cover standing is obtained by deepening the kneeling"
trench to 4 ft., leaving a stt^p 20 in. high and 3 ft. wide next
the front wall, so as to facilitate leaving the trench to the
front and at the same time allowing a protected passage in
rear. The step serves as a banquette for men firing over the
embankment.

The embankment is given a height of 2 ft., the resulting thick-
ness being about 51/2 ft. (Fig. 3.)

The average time required by one man to transform 5 ft. of
the trench "kneeling" into the trench "standing" is, with large
pick and shovel, 1 hour.

32. — When isolated trenches for single skirmishers lying are
desirwl, they should be made with the same section as that shown
in Figure 1 and have a length of 1 pace. Isolated kneeling trenches
for two men should also have a length of 1 pace, but the
rifle pit, or isolated shelter standing should be 5 ft. in length on
account of difficulty in constructing a smaller one. The last read-
ily accommodates three men, two of whom can fire over the
embankment, while the third, standing in the 4 ft. trench, pro-
tects the flanks.

33. — When necessary to intreneh^ mpportJi and reserves, the cover
kneeling or standing should be used in parallel rows close to one
another. (Fig. 5.)

In the construction advantage should be taken, 'Where possible,
of plows for loosening the earth. Two or three plows following
each other at intervals can be used to great advantage.

34. — The trenches here illustrated are all made on level
ground and are simply types showing the l>est forms and giving
general ideas as to the time i-^quired to construct cover.* On

♦Cover from view only can. of course, be obtain«^d much more quickly, but a
penetrable cover is hard'ly more than a target to invite an enemy's fire.

Hasty IntrenchmenUy Oun Pita and Epaulements. 25

slopes they must be modified so that the tops of the embank-
ments are, in general, parallel to the ground; they may also be
varied according to the kind of earth, sand requiring less thick-
ness of embankment and gentler slopes than clayey soil, while
sod mixed with earth allows greater penetration than earth
without it.

35. — The location of trenches depends primarily on tactical
situations, and secondarily on the nature of tlie ground.

Primarilyy they sliould always occui)y a position giving the
greiitest development of fire, and lience are generally located
near the crest of the most abrupt sUxpc-^. c, near the ''military
crest.'* (See par. 153.) The exact position is determined by plac-
ing the eye at a distance above the graund equal to the proposed height
of t-mhankmentj and then selecting that line which gives a clear field of
fire to the frotit.

As to the secondary consideration, it is desirable in locating
trenches to avoid stony ground and that close to the edges of
woods, the former on account of the liability to flying frag-
ments should the embankment be struck by an artillery projectile,
and the latter by reason of the difficulty in constructing the
trenches.

36. — ^Intervals in line of trenches. In all trenches except
those for skirmishers lying down, intervals in the line should be
left for the passage to the front of artillery and cavalry— tliis
is especially necessary when cover standing is used. The inter-
vals may vary in width according to circumstances, but sliould
never be so wide as to preclude their defense by the trenches
adjoining the opening.

37. — Splinter-proofs. When troops are required to remain
In the trenches for any considerable period, they should be pro-
vided with splinter-proofs or slielters of some kind, blanks, old
lumber, doors, etc., or, in their absence, small poles, may be used.
They sliould be laid with one end on the embankment, the other
resting on the ground in rear of the trench, and then covere<l with
3 or 4 Inches of earth. This defense, while not proof against burst-
ing shells, will protect the men from dropping bullets and shrapnel
fragments. (Fig. 4.)

38. — Concealment of shelter trenches. Endeavor should
nhoays be made to disguise the location of shelter trenches
by covering the sides toward the enemy with branches, weeds,
sod, etc.

26 Hasty Intrenchmenis, Chin Pits and Epaulements.

39.— The advantages and disadvantages of the shelters for
men lying and kneeling may be briefly summarized as follows:
Advantages.

(1) They present but little difllculty to the advance of the
defenders' cavalry or artillery over them, and are easily sur-
mounted by the occupants when the advance is ordered.

(2) They will stop rifle bullets.

(3) They offer but a small target to the enemy's artillery fire.

(4) They are quiclily and easily made.
Disadvantages.

(1) The embanltments being low, the field of fire may be lim-
ited by small folds in the ground (care in selecting their position
may partially remedy this disadvantage).

(2) In wet weather they may become untenable by reason of
mud.

40.— Loop-holes may be provided by half imbedding head-logs
in the embankment, or resting them on sand-bags on top of it, and
leaving spaces beneath for the rifle. Or the loop-hole may be
formed with four sand-hags, as shown in Fig. 7. Brushwood may
also be used with an earth cover, either alone or in connection with
a head-log, as shown in Fig. 0.

Loop-liolos for rifles splay inward, for field guns, outward.

The hc\8t practice is not to use head-logs or loop-holes (unless in
case of an inferior force acting solely on the defensive), as their
use impels men to hesitate to leave cover when the advance is
ordered.

40a. — Cover for guns may be obtained in two ways.

(1) By means of Qun Pits; made by digging a hole of a size suflS-
cient to partially conceal the gun and gun detachment, and form-
ing an embankment in front with the excavated earth. (PI. 4,
Figs. 1, 2 and 3.)*

(2) By means of Oun Epanlernents; made by constructing an
embankment in front of the gun which rests on the natural surface
of the ground. In this form the gun detachment would be par-
tially sheltered in the pits from which the earth for the embank-
ment is taken. (Figs. 4 and 5.)

Circumstances would control the selection of the kind of cover,
if any, for field guns. The disadvantages of gun pits are the same
as those of shelter trenches, but pits give more complete protection
to the gun. (See par. 153.)

♦Figs. 1, 2 and 4, PI, -1, are from U, S. Artillery Drill Regulations.

PLATE 4.

FIGURE 3.

■"SS

»»

,,^

-45^

FIGURE 4.

FIGURES.

fTTF-TT

PLATES.

CHAPTER v.— Clearing the Ground.

41. — The tools more especially used in the field may be divided
Into two classes.

(1) Intrenching tools, such as the pick, the shovel (long and
short handled), the spade, the picket shovel, and the hunting knife
^Infantry equipment).

(2) Cutting tools, such as the ax, the hand ax, the log saw,
the hand saw, the linked felling saw, the gabion knife (pruning
knife), the hunting knife, the bush hook and the wire cutter.
(PI. 5 and 6.)

42. — The choice of a defensive position in which the foreground
is free from obstructions and favorable to the defenders' fire is of
the utmost importance: more or less clearing, however, will usu-
ally be necessary^ Clearing must be systematically (Jone, and, as
in all other work, should be undertaken by complete organizations
or parts of organizations under their own officers.

43.— The extent (theoretical) to which the foreground should be
cleared is equal to the eftective range of the defenders' weapons.
Practically, as wide a space within this limit, is to be cleared, as
is consistent with the time and labor available. Brushwood and
standing timber must often screen the enemy's advance and steps
should be taken to remove them.

44.— The tools usually employed in felling heavy timber are
the ax and the log saw, the former being the most common, al-
though inexperienced men acquire familiarity with the latter more
quickly. When using the ax the cut should be commenced on the
side toward which it is desired the tree should fall, ropes being
used to incline it in that direction, if necessary; if immaterial
which way the tree falls, then attack it on the side toward which
it leans; after cutting it a little more than half through change
over to the other side and commencing about six inches higher
up, cut until it falls. In using the saw it may be necessary to

PLATE 7.

Figure 1

Figure 2,

Figure 12

CHAPTER VI.— Obstacles.

49. — Obstacles have for their object the holding of the enemy
under fire while checking his advance and breaking up his
formation.

(1) They must be within the effective zone of the defenders' fire
and must be so arranged as to offer tlie least obstacle possible to
an advance from the side of the defense.

(2) They must be concealed as far as possible from the view of
the assaulting party, so that they may come upon them as a
surprise.

(3) They must be diflficult of removal under flre, and, if possi-
ble, should be of such construction as will necessitate the use of
tools not usually carried by troops.

(4) They should, if possible, be so placed as to be secure from
the fire of the enemy's artillery, and so constructed that, if strtick
by his projectiles, they will suffer small damage.

(5) They must offer no shelter to the enemy.

50.— Abatis, on account of the ease with which it can be con-
structed, is the obstacle most used.

It consists of branches of trees, about 15 feet long, laid on the
ground, butts pointing to the rear, all small twigs being cut off, and
all large branches pointed and interlaced. The abatis should be
5 feet high.

The branches are secured to the ground by forks, wire, or by
logs laid over the butts of the branches. The use of wire to hold
down the branches is recommended, and when used should be also
passed from branch to branch so as to form an extra form of en-
tanglement. When more than one row of abatis is used the
branches of one row overlap the butts of the next one in front.
(PI. 7, Figs. 1 and 2.)

The abatis most easy of construction is that made by felling
trees towards the enemy in such manner as to leave the fallen
part still attached to the stump; the branches are then pointed as
described before. (Fig. 5.)

51.— Abatis is often placed in the front of works when the
ditch is so shallow as to present little or no obstacle to an assault.
When so used they are placed upright and well tamped in. In all
cases, especially when small bi*anches are used, it is better to sink

38 Olstacles.

the butts in triangular pits, and, when the branches are in place,
fill in with earth and tamp well. (Figs. 3 and 4.)

In all cases where exposed to artillery fire a glacis should be
constructed in front of an abatis, so as to protect it from injury.

52. — Low Wire entanglements are formed by driving into the
ground stalies about 18 in. long. The stakes should be driven in
rows about 6 feet apart, the staljes in each row being opposite in-
tervals in adjacent rows. The heads of the stakes are connected
by stout wire wound around them. To make this more effective,
do not clear the grouud, but allow bushes, brush, etc., to remain in
place. (Fig. 6.) Use 1 ft. of wire to 1 sq. foot of ground covered,

53. — High Wire entanglements are constructed in the same
manner, except that the stakes should be at least 4 ft. high, and
placed 6 to 8 feet apart. The head of each stake is connected
with the foot of the stake diagonally opposite, the line of posts in
front and rear being finished off as fence panels with barbed
wire. The use of barbed wire is not advised for the interior
crossed work on account of the danger and diflSculty in working
with it.

Roughly, 1 yard of wire is necessary for each square foot of
entanglement. Ten men can make about 9 square yards of this
entanglement in one hour. This work does not require trained
men. Wire entanglement, either high or low, is useful on the
glacis of field works, as it holds the attacker under fire at the most
favorable point. (Fig. 7.)

54. — ^Palisades consist of rows of trunks of trees or of squared
trunks, 8 or 10 feet high, planted close together and pointed on
top. When material is at hand, ribband pieces should be spiked
on the inside along their tops about a foot or two below the
points to hold them steady. They are used to advantage in the
bottoms of ditches or to close the gorge of field works. (PI. 8,
Fig. 1.)

55. — Fraises are palisades arranged horizontally or much in-
clined and are much used at the foot of the exterior slope and at
the top of the counterscarp; in the first position they point down
and in the second upward. In each case, the ribband or strip is
spiked on and laid against the ground near the edge. of scarp or
counterscarp, as the case may be, another one being spiked to the

PLATE a

Figure 1 .

Figure 2 *

Figure 5. U

^^^^

1...J

Tig. 6.

Ohst€U)le8. 41

inner end of the fraise; thus the outer ones give good bearing sur-
faces and do not brealj up the crest, and the inner one gives a bear-
ing for stalling and tying down. The slopes described above are
given so that unexploded shell will always roll away from the
parapet. (PI. 7, ITigs. 9, 10, 12 and 13.)

Fraises may with advantage be made of barbed wire in the
form shown, care being talien that all wire when finished is on
top of the wooden supports. The advantage of this variety of
fraise is that it is little damaged by artillery fire and is very diffi-
cult of removal.

When time is pressing fraises may be made of branches of trees
with the butts well sunken and staked down.

56. — Crows' feetj Chcvaux-de-frisey and planks full of spikes have
been used in the past as obstacles to an advance^ but the two
former are not now issued for use in our service, and the latter is
one not easily made in the field. Such obstacles require much
time and material in their construction and are not treated of
here, as they do not fall properly in the domain of Field Engineer-
ing; their value in any event is not commensurate with the diffi-
culty of their preparation. (PI. 8, Figs. 2 and G.)

57. — Small Pits are square on the top, 3 feet on a side, and are
pyramidal in shape; they are 2 ft. 6 in. deep, and have a pointed
picket driven in the center of each.

In digging these pits a glacis should be formed in front of the
row nearest the enemy, and, to avoid filling the pits with earth
thrown from the others, the row fartliest from the glacis should
be commenced first. One man can make 10 pits per day in easy
soil. (PL 7, Figs. 8 and 11.)

Small pits may be surmounted by a low wire entanglement,
making a very serious obstacle.

58. — Fords may be made impassable by strewing them with
harrows, points up.

59. — A Fougass is a mine so arranged that upon explosion a
large mass of stones or shells are projected towards the enemy.
(PI. 8, Fig. 3.)

To make a fougass, dig a hole in the shape of a frustum of a
cone, inclining the axis in the direction of the enemy, so as to
make an angle with the horizon of about 45 degrees. The sides

42 Obstacles.

should splay outwards at an inclination of 12 degrees from the
axis. The powder charge is placed in the bottom of the hole —
preferably in a box— and in front of this a platform of wood
about 3 inches in thickness: on this are piled stones, brick, etc.
The mine is exploded by means of electricity or common fuse.
Care must be taken in digging the hole for the fougass that the
line of least resistance is in all cases in the axis of the hole; to be
sure of this, throtc the excavated earth upon the crest totoirds the
defenders* side and ram well, allowing earth to enclose the sides of
the excavation in the manner shown in cut.

Fougasses are useful in defending boat-landings, roads, etc.

The following empirical formula may be taken for determining
the charge of powder for fougasses: P = j^, in which P and s
represent the weight in pounds of the powder and stone.

When broken up, a cubic foot of limestone weighs 96 lbs.

60. — Land Mines are small mines placed in the line of ad-
vance of the enemy and exploded either by electricity or fuse
from the defense. The small mines are made by digging holes
from 2 to 3 yards deep, placing the charge in a box in a recess
excavated in one side of the hole, and refilling with the excavated
earth, tamping well. The wires are carried back in a small trench
to the work. In common earth, the charge for 2 yards deep is
about 25 lbs., and for 3 yards deep about 80 lbs.; the diameter
of the crater formed will be about twice the depth of charge.
(Pig. 4.)

61. — Barricades are used to prevent the passage of the enemy
through roads, streets, and defiles generally.

They may be made of any material at hand, paving stones,
overturned carts, barrels filled with earth, stones, and articles of
like nature. They should be built so that a passage is always left
for the defenders, but means should be at hand to close the open-
ing quickly— a wagon may be used for this purpose, being drawn
away from the opening when a passage is desired.

The houses on either side should be loop-holed and used to
flank the defense. Overturned wagons, broken furniture and
debris from the adjacent houses make a very good obstacle and
should be placed in front of the barricade to ward off cavalry
charges. (Fig. 5.)

PLATE .9.

Figure. 1

CHAPTEB. VII.— Field Works.

62. — When a position is to be held for a considerable period and
when time is available, more deliberate defenses than the Hasty
or Battle Intrenchments (Chapter IV.) are constructed. These are
known as Field Works and usually require a minimum of 6 hours
for construction. The conditions to be fulfilled, besides those nec-
essai-y for a defensive position (Chapter I.), are.

(1) That they must afford protection against both rifle and artil-
lerv fire.

(2) That they must be of suitable size for the garrison that is
to occupy them.

(3) That they should have suitably constructed casemates to
shelter the garrison at night.

Field works may be constructed for the defense of a single ob-
ject, as a bridge, a ford, etc., or they may occupy the key points in
a long line of defense, in which case they should be located so as
to afford mutual protection, the intervening siiace either being left
open or occupied by shelter trenches.

Before proceeding to the study of Field AVorks, a brief synopsis
of the technical terms used in connection with them will be
necessary.

63.— A Parapet is a bank of earth thrown up to cover the
defenders while firing.

64. — The Trace of a work is its outline in plan: the term is
often applied to the horizontal projection of its interior crest.
(PI. 9, Fig. 1.)

65. — The Profile is a cross-section of the work made by a plane
perpendicular to the interior crest. (Fig. 2.)

In the protile, the various parts are nfimed as follows:

a. Banquette slope, e. Exterior slope, d. Ditch.

b. Banquette tread, f. Berm. i. Interior slope of glacis.

c. Interior slope. g. Escarp. k. Glacis.

d. Superior slope. h. Counterscarp, t. Trench.

66. — The Interior Crest is the intersection of the Interior
and Superior slopes: sometimes called the magistral line, ("a"
Fig. 1.)

4() Field Works.

67.— The Exterior Crest— that of the Superior and Exterior
slopes, ("b" Fig. 1.) The thickness of parapet is the horizontal
distance between interior and exterior crests.

68. — A Traverse is a banlv of earth inside a worlc to protect
some portion of it from direct fire. When the protection afforded
is from reverse fire, the traverse is sometimes called a Parados.
(Figs. 3 and 4.)

69. — An Embrasure is a revetted opening in the parapet,
through which field guns may fire. It is said to be Direct or
Oblique according to whether its axis is perpendicular or inclined
to the line of parapet.

70. — A Gun Bank or Gun Epaulement is a raised mound, by
means of which field guns may fire over the parapet. Guns thus
placed are said to be en harhette.

The relative advantages of Embrasures and Gun Banks are as
follows:—

Embrasures afford greater protection to the gunners, but

(a) They afford a very limited field of fire.

(b) They weaken the parapet and require frequent repairs.

The conditions as to Gun Banks are the converse in each case.

71. — The Command of a work is the height of its interior crest
above the ground on which it is constructed. (*'m" Fig. 2.)

72.— Its Relief is the height above the bottom of the ditch,
("o" Fig. 2.)

73.— The Plane of Site is a plane tangent to the ground on
which the work is constructed.

74. — The Terreplein is the surface of the ground inside the
work and does not, of necessity, coincide with the plane of site,
since the whole interior of the work— i. e., the terreplein— may be
lowered for the purpose of securing more cover.

When the banquette tread is more than 2 feet above the terre-
plein, its slope may be stepped with fascines or planks: this has
the advantage of giving more interior space, but tends to produce
confusion on the part of the defenders, especially In a night
assault.

Field Works. 47

75. — The interior slope is usually made as steep, up to four on
one, as the revetment will stand.

76. — The superior slope is necessary in order to secure the best
fire effect on the ground immediately in front of the work. It
weakens the parapet near the interior crest, however, and this
defect increases as the slope is made steeper; hence, it should be
as slight as is consistent with good fire effect.

The degree of this slope is regulated by the principle that fire
from rifles resting on its surface should not pass more than three
feet above the glacis, or, when there is no glacis, above the outer
edge of the ditch. It will thus depend on

(1) The command of the work.

(2) The inclination of the plane of site.

(3) The distance from the interior crest to outer edge of ditch.
The slope should not exceed one on four; one on six (normal) is

better, and then, if necessary, make a glacis of the requisite
height.

77.— The exterior slope should be as gentle as two on three, if
possible, owing to the fact that steeper slopes are soon destroyed
by artillery fire.

78. — The Berm may be as great as 6 ft. in width ; ordinarily It
would not be greater than 2 ft., while in favorable soil none may
be left at all.

Advantages of berm:

(1) It relieves the edge of the ditch from the weight of the par-
apet and thus prevents caving, in loose soil.

(2) It enables the parapet to be thickened.
Disadvantages:

(1) It affords a footing in an assault. (This, however, may be
partially remedied by use of obstacles.)

79. — The slope of the escarp and counterscarp should be equal
to or greater than the exterior slope, the latter being as steep as
the earth will stand.

80.— The Glacis should be parallel to the superior slope, in
order to get the best fire effect from the crest.

81. — If the parapet does not require much earth, and the ditch
is required as an obstacle, it may be made triangular in cross-sec-

48 Field Works.

tlon. This form gives tlie greatest depth and prevents the assail-
ants from forming in the ditch, but it is difficult of construction.
Kight feet may be talien as the extreme depth of ditch and twelve
feet as the extreme height of parapet. The width of the ditch
varies with the amount of earth required— 12 ft. at the top being
a minimum.

A parapet with trench and ditch affords cover in the shortest
time possible: each foot of depth in the trench means 2 ft. of
cover, plus the additional protection afforded by the earth from
the ditch.

A parapet with ditch alone affords greater cover to the ground
in rear and better command of ground in front, but its height
makes it more conspicuous.

82.— Referring to traces of various works (PI. 9, Fig. 5)—

a, is a salient angle,
a' is a shoulder angle.

b, is a reentrant angle.

c, c, c, are faces. e, e, is the gorge.

d, d, d, are flanks. f, is the capital.

83. — Field Works are classified with reference to their
trace, as

(1) Open, which have thick parapets on exposed sides, the rear
or gorge being open.

(2) Closed, in which the thick parapet is continuous.

(3) Half-Closed, which only differ from the "open" in that
the gorge is closed by obstacles, stockade work, or shelter
trenches.

Advanced works within rifle range of the main defensive line,
as well as those in positions where the flanks are secure (as a
bridge head), should usually bo "open." Works in main line and
advanced works beyond rifle range should be "half-closed"; those
in isolated positions or on the flanks of a defensive line— "closed."

Open works have the advantage over closed, of affording greater
freedom of movement to the defenders, and, in the event of cajv
ture, of being exposed to fire and assault from the works in rear.

Closed works, while affording greater protection from assault,
are liable to have their parapets exposed to enfilade or reverse fire,
besides which the available interior space is much reduced.

PLATE 10.

Field Works, 51

S4.— -Forts and Redoubts (Closed Works) are distinguished
by the former having reentering angles, thus affording defense
of the ditch from the parapet, both conditions being lacl^ing In
redoubts.

Redoubts, as compared to forts, are of simpler trace, do not re-
quire so large a garrison, and afford better fi*ontal fire; but, as
they have no ditch defense (unless caponiers and counterscarp
galleries are constructed), they should be traced to support one
another.

85. — With respect to caponiers (PI. 20) and counterscarp gal-
leries—the former, if sunken, as is usually necessary for protection
against artillery fire, may become untenable in rainy weather;
while communication with the latter is difficult and may, by the
enemy, be rendered impossible. The objections to these forms of
ditch defense are so great, and their use so limited, where proper
frontal fire and obstacles are possible, that their construction is
seldom necessary.

86.— The Sector of Fire is a term used to designate the angular
space in front of a work which is swept by its fire (30° on each
side of a perpendicular being considered the limit of oblique rifie
fire.) Thus, a straight line of parapet has a sector of fire of 60**
(PI. 10, Fig. 1), while, in a redan, it varies with the angle at the
salient. With a salient of 120°, the sector of fire is evidently 120°
(Fig. 2); with a 60° salient, there will be an undefended space of
00°. (Fig. 3.) This undefended space may be done away with by
blunting the redan. (Fig. 4.) A redan with shoulder angles
(Fig. 5) furnishes a ditch defense in front of the shoulders and does
away with part of the dead space in front of the salient, but it is
difficult of construction and is not usually resorted to.

87.— For reasons given in Chapter XI., it is often desirable to
place the guns outside the work: in which case some plan like
Fig. 6 may be adopted, the single line representing a shelter
trench.

88.— Defilade of Field Works. In order that Field Works may
fulfill the condition of screening the occupants from the fire and
view of an enemy, the problem of defilade arises.

This may be defined as the operation of regulating the direction
and command of the earth cover so that the Interior of the work
is protected from the direct fire of an enemy.

52 Field Works.

The problem resolves itself into two distinct parts—

(1) DefiJadiufj in plan,

(2) Deflladwp in section.

89. — Defilading in plan. This involves the selection of the
trace of the work (its position having been previously chosen).
The trace will vary with the plane of site, the terrain in the im-
mediate vicinity, the proximity of high ground that the enemy
may occui)y, and the time available for construction. A plane of
site sloping to the rear is obviously the easiest to defilade, and
one sloping toward the enemy the most difficult. Salients should
occupy commanding ground, the lower portion being taken for
the reentrants or for the gorge. Tlie longer faces of a work should
lie in the direction of lower or inaccessible ground, so that they
cannot be enfiladed.

With commanding ground in front, the work is more diflicult
to defilade in proportion to its depth; therefore, have longer faces
opposed to the high ground and make the work as shallow as is
consistent with other conditions.

As a rule, the longer faces of a work must lie so that the de-
fenders can bring as direct a fire as possible in the direction of
expected attack.

All the foregoing conditions as to defilading in plan cannot, in
the usual case, be satisfie<l, but the object to be attained must be
kept constantly in view, and, in selecting the trace for a work, an
officer's ability will be shown by the skill with which he harmon-
izes the various diverse requirements.

After the careful selection of the trace, as already indicated,
and marking it by pickets, the problem is completed by defilading
the proposed work in section.

90. — Defilading in section. With a horizontal site and only
level ground toward the enemy, a constant command of 8 ft. is
sufficient to protect the whole interior of the work.

On an irregular site, or when necessary to place a work in a
position commanded by higher accessible ground, the necessary
protection of 8 ft. may be attained in one of three ways—

(1) By raising a parapet.

(2) By lowering the terreplein.

(3) By use of traverses, parados, bonnets, etc.

PTrATF, 11

Pigrure 1.

Figure. 2.

^,, |J*v<i47gk«rt5w^ —

Figure 3.

-I ^

Figure 4 .

Field Works. 55

To determine how much protection is needed, suppose, for ex-
ample, the proposed work is a lunette. Plant poles at the salients
of suflacient length to reach the interior crest of completed work.
Place two pickets at the gorge, about 6 ft. apart, one on each side
of the capital, and a third 8 ft. to the front. Tie a. string to the
rear pickets, 3.5 ft. from the ground, the string passing round the
third stake. (PI. 11, Fig. 2.) Taking position behind the horizontal
string, have an assistant move the string on the forward picket
until it comes into the plane fixed by the eye, the horizontal string
and the highest point of the dangerous ground. This plane,
which is now established by the string triangle, is called the; tan-
gent plane, A plane parallel to this and 4.5 ft. above it is known
as the plane of defilade. (Fig. 1.) The proper height of parapet at
the salient and shoulder angles is now fixed by sawing off the
poles 4.5 ft. above the points in which the tangent plane cuts them.
This will evidently give 8 ft. cover at the gorge, at which point
the height of parapet of the flanks is 8 ft.

If it is found that the required height of parapet exceeds 12 ft.,
the plane of defilade may be lowered not to exceed 1.5 ft. This will
still give 6.5 ft. protection at the gorge.

If this proves insufficient, either traverses must be resorted to
or the terreplein at the gorge lowered.

91. — To defilade a work from two or more heights, the plane
must be tangent to the two heights to which angles of elevation
are the greatest. As three points fix a plane, it follows that the
tangent plane would usually contain but a single point of the
string at the gorge; hence, the problem is solved by reversing the
string triangle— i. e., fixing the apex at the gorge 3.5 ft. above the
ground, and the two extremities of the base within the proposed
work and far enough apart to allow the two heights to be seen
between them. An assistant at each of the forward stakes ad-
justs the string as directed. (Fig. 3.) The problem Is then com-
pleted as in the previous case.

92.— It is sometimes advisable, when a single plane of defilade
gives too great a command, to use two planes; the portion of the
interior of the work on the side toward H (Fig. 4) being defiladed
from it, and that on the other side from the height H'. This
method exposes the faces and flanks to reverse fire and renders
traverses (parados) necessary.

56 Field Works.

93. — The height of a traverse (which should be such that a
shot grazing it will pass 2 ft. above the parapet It is to cover) is
found as follows:

Assume that the traverse is to be on the capital of a lunette.

The problem of direct defilade with two planes having been
solved, and the poles at angles of the works having been sawed off
to indicate the proper height of interior crest in order to defilade
the work as far as the capital, the height of traverse to protect a
flank from reverse fire is found thus: Measure down from the
tops of the poles at the extremities of the flank any convenient dis-
tance, as 3 feet,* mark the points and connect them by a string.
This string and the opposite height determine a plane which will
cut rods held vertically on the capital, at a distance of 5 feet below
the required top of the traverse (2 ft. plus the distance measured
down on the poles). Pi'oceed in a similar manner, using the other
hill and its opposite flank. The greater of the two results fixes
the height of that portion of the traverse. In the same manner,
Its height to protect the faces from reverse fire may be found.
By reference to Fig, 4 this will be readily understood.

This method, while not absolutely accurate, will give results
near enough for all practical purposes, with the error on the side
of safety. Traverses or Parados are the usual protection against
reverse and enfilade fire, and, although sometimes used to protect
parts of a work from direct fire, this is usually attained either by
raising the parapet, by lowering the terreplein, or by both these
methods combined.

94.— Profiling. After the trace of the work has been decided
upon, the problem of defilade solved, the poles at the angles cut
off as indicated, and the cross-section of the parapet decided upon,
the next step is to erect profiles which shall correspond to this
cross-section. These profiles are, if practicable, to be made of
strips or battens 1 in. x 2 in., and placed at intervals of about 10
yds. along each face and flank, as well as at each angle.

For parapets not over G ft. in height, stakes may at once be
driven into the ground and strips nailed to them, but for higher
parapets It is more convenient to make the profile on the ground,
merely driving short pickets in place of the long stakes in the first

♦The idea being- to have the string- behind which the observer stands, when
looking towards the height, at about the level of the eye.

PLATE 12.

PLATE 13

Field Works. 61

mstauce. When completed, the profile is up-ended and nailed to
the pickets. (PI. 12, Fig. 1.) If strips cannot be obtained, the
entire profile, except the uprights, may be made of twine. The
profiles at the angles of the works, known as oblique or angle pro-
files, will evidently differ from the others in length, while their
height, on level ground, remains the same. The position of any
point of tiie angle profile, as, for example, the exterior crest, is
fixed by finding the intersection of the prolonged exterior crest
lines of the face profiles. This result is accomplished by standing
on the fartlier side of the second profile from the angle and lin-
ing in an assistant who holds a rod vertically at the angle, one end
of the rod resting on the ground. After the profiles are in place,
tAvine should be stretched between them to indicate the various
crest lines. The outer edge of the battens marks the extent of
tlie fill, except in the case of the interior slope, which is marked by
the inner edge when the slope is to be revetted.

95.— Calculation of Dimensions of Earthworks. The Com-
mand of the proposed work having been fixed by the requirements
of defilade, and the thickness by tlie character of fire expected,
it becomfs nccnssary to calculate the dimen»ioris of the excavations,
so that they will ftumish enough^ and fio more, earth than is required.
The size of embankments and trench are, by the nature of the
problem, fixed, as is the depth of ditch; hence the only variable is
width of ditch, which is found as follows:

Assuming the relief to be constant and the profile, for example,
to be as shown in PI. 13, make a sectional sketch of the proposed
work at any pomt except an angle. Calculate the sectional area
of parapet, glacis, and trench, in square feet, and from the sum of
the first two subtract the last: the remainder divided by the as-
sumed depth of ditch, in feet, will give the mean Avidth of ditch,
from which, knowing the slope of escarp and counterscarp,
the width at top and bottom can readily be found.

96.— Earth in embankment occupies, for a time, about one-
twelfth more space than it did originally, but this increase is
not usually taken into account in the computations for ascertain-
ing the width of ditch. When the relief of a work is not constant,
it is evident that, in order to get the proper amount of earth,
either the depth or the width of ditch must vary. - On account of

62 Field Works.

the labor required in raising earth, the limit of depth is taken at
8 ft.; for a similar reason, the maximum height of parapet is
taken at 12 ft. Whatever the depth of ditch assumed, it is always
constant. The required width at any point is found by means of
a section of the work, as already explained, a section near the
extremities of each face determining the width of ditch for that
entire face.

97. — An excess of earth will occur at the salients and a defi-
ciency at the reentrants, although this may be partially obviated
by maliing the shovelers throw toward the reentrants.

98. — Drainage of the trench must be provided for at the time
the work is constructed. If the fall is toward the gorge, an open
drain will sufiice; but if in any other direction, a covered drain
(PL 50) should be left to carry the water to the ditch.

Construction of Field Works. The details of construction and
dimensions of earthworks will change with varying requirements
and soil, but tliere are certain general principles that should be
followed in all.

99.— As to profile: The Normal (PI. 14, Fig. 2) fulfills the
conditions as to simplicity, protection against field artillery (in
most soils), command of the ground in front, and cover standing,
in the trench. The trench is stepped and steps revetted to facili-
tate mounting the banquette, while the berm is omitted to deprive
the assailants of a foothold. The command may be increased
eitiier with or without constant relief, the parapet thickened or
reduced, and the trench made into a casemate without changing
the type of this profile.

100. — As to garrison: For ordinary field works, the garri-
son is usually computed at 2 men per yard of interior crest; but
for isolated works, this estimate should be increased by one-half.
Embrasures and gun-banks each reduce the interior crest line
available for troops, by 5 yards.

101. — ^As to laying out tasks: Cutting lines must be marked
by tape or pick, computations made, and the exact size of the task
for each relief determined in accordance with the rules given in
Chapter VIII.

As an example of laying out tasks, assume that an earthwork

PLATE 14.

Sj^ti/mate yt#^ iO(?/^ yMt>rand (di4Sia4Af^/^^

T^-^'^ ffr.

Men.

rfieuef. 2'fhuer. 5'ffsusF.

-a...itq aL.l.iO

S/Wej Pccl^ SttoyelaS^ r/ltl ?Vft/ i'/fel

Oitch /

Trmncfl {

■Ih

'.v.zo":.'.'.i'o.

too.

~SS7.
At

rz.

6 J

dL • cUffj^ers • g • shays'/era

.. 40..\. 23

Pcirapet

Zkd' ly /man \

7huA - Imem

/^ ^_

Task - J mar*

ift Rtiisf

-Ist BelU/^

TasM - fpna**
i^ Relief

Plar

Ta^k ;| I man.

Tat.k

/Sklu^

I f mat

"^^
<^^

^«

4.4 i'l

PLATE 15.

FIG. 1

FI&.2.

,-^ IMO to 300O yarcfs ^i^^-s.-^

r^-^ s

|5|

-*-

Field Works. 67

with uormal profile and constant command of 6 ft. is to be made
on a level site.

Before work is commenced, the outer and the cutting lines of
ditch and trench must be marked. As fatigue parties cannot be
expected to excavate eartli and at the same time preserve the
proper slopes, the usual method followed is to dig vertically as in-
dicated by the cutting lines and afterward form the slopes by cut-
ting off the steps.

The cutting lines for the task of the 1st Relief would be made
on the ground, as indicated in section and plan. (PI. 14, Fig. I.)
The 1st Relief having finished, cutting lines for. task of 2d Relief
would then be marked out; and finally, the 3d Relief would com-
plete the slopes of ditch and parapet, and finish any work not com-
pleted by the other reliefs.

When not practicable to revet the banquette and trench steps,
the risers may be sloped back at about six on one.

When necessary to throw earth more, than 12 ft. horizontally,
extra shovelers should be provided at the rate of 1 to each 2, or 2
to each 3 diggers, depending upon the soil and the distance it is to
be thrown.

102.— Oun-banks, when made, are usually placed in the sali-
ents, for the reasons that the guns will have a greater field of
fire and it is at this point that the earth of which tliey are made is
in excess. PI. 12, Fig. 2 shows a gun-bank on a straight line of
parapet, and Fig. 3 one at a salient. The top is horizontal and 3.5
ft. below the interior crest: this distance may vary, however, for
different pieces. All slopes are one on one, except the ramp, or
roadway leading up to the bank; this may be as steep as one on
four, but a gentler slope is better. The width of ramp should be 8
ft. The level surface of the bank extends back 24 ft. from the para-
pet and a log or fascine is half sunken and picketed near the front,
for a hurter. The width of bank for a single gun is 15 ft. At a sali-
ent (PI. 12, Figs. 3 and 4) the angle is filled in by a straiglit revet-
ment from 6 ft. to 15 ft. long and the superior slope reduced to cor-
respond to lines joining its extremities with the exterior crest
salient. This forms what is known as a "pan coup€."

103. — Embrasures for field guns would be used in positions
where the fire is required to be in one direction only; for example.

68 Field Works.

to sweep a road, bridge, or ford; or in the flanli of a work to
cover ground in front of an adjacent work.

PI. 15, Fig. 1, shows the horizontal projection and the section of
an embrasure. It is made at the same time as the parapet, by
making the sole "s" parallel to the superior slope. The cheeks,
"c, c," are vertical at the throat, "e," and have a slope of one on
one at the other extremity; their height should never exceed 4 ft.

The usual method of forming an embrasure is to stretch a string
along the line of fire; at tlie throat lay off 1 ft. on each side of it,
and at a distance of 5 ft. from the throat lay off 1.5 ft. in a similar
manner. Right lines joining the corresponding points so deter-
mined will mark the outer lines of the sole, which will splay one
on ten. Kach throat gabion is vertical, the extreme ones being in-
clined three on one: the slope of the intermediate ones is secured
by alignment top and bottom on the extreme ones. Each gabion
is anchored independently of the others, so that one may be torn
out without seriously injuring the embrasure.

104. — By the Merlon is meant that portion of the parapet be-
tween two embrasures and above the soles. Embrasures should,
as a rule, never be closer together than 15 ft.; otherwise the metlon
is too much weakened.

TLATE 16.

•Fig. 1.

Fig. 3.

-r^^

jr'

(5-

□

Fig. 4.

^- ^' ^' ^?' V'

.^6^

CHAPTER vni.— Working Parties.

Occasion may arise, as, for example, at night, in the presence of
an enemy or even with a large working party, when a well-estab-
lished system of taking and handling tools, distributing and reliev-
ing working parties, etc., will be a paramount importance.

105. — Organization of Working Parties. The nature of the
required work having been decided upon, the estimate of and the
application for the requisite number of men and tools devolves
upon the otlicer charged with its execution.

A working party of the requisite strength (which should include
a reserve of 1-lOth) should be furnished, as far as possible, from a
complete organization, a company, a battalion or brigade, and not
from detachments of different organizations.

106. — Rei^ponsibility. The party should be divided into re-
liefs and the task each is to accomplish made plain before it begins
work. The officers and non-commissioned officers of the working
party are responsilile for the amount of work done.

107. — Taking Tools. The first relief, having been formed
in single rank with rifles slung across the back, is marched to the
park where the tools have previously been laid out, either in rows
(PI. 16, Fig. 1) or in heaps. (Fig. 2.) The relief in the former case
is advanced in line to the row and each takes a pick in the left
and a spade in the right hand; in the latter case the party in col-
umn of files is marched between the piles, each in turn receiving
a pick in the left and a spade in the right hand. The relief is
then marched in column of fours or twos to the point where the
work is to begin.

108. — Carrying Tools. In carrying picks and spades the
handles are grasped near the iron, which is held vertically, the
arms extended and the hands close to the side. In turning, the
point of the pick should be lowered and the blade of the shovel
raised, and when marching, either in line or in column, the han-
dles should be splayed outward, in order to prevent interference.
The necessity under certain circumstances of preserving silence
makes the above precautions important at all times as a matter of
training.

72 Working Parties.

109.— Extending the Working Party. When the first re-
lief approaches the designated point it is halted, then brol^en in-
to column of files and direction changed, if necessary, so that the
head of the column approaches in a direction parallel to and about
3 yds. in rear of the tape marking the front edge of proposed exca-
vation. (Fig. 3.) When the leading file is opposite his place the
command is given:

(1) On right (or left) into line at two paces interval. (2) March.
(3) Detachment. (4) Halt.

The command "Halt" is given when the leading file is 1 yd. in
rear of the tape. Wliile the line is forming, the correct positions
are at once taken, as follows:

Each man on arriving at the line extends his arms horizontally,
holding them thus until his own position and that of the man fol-
lowing him are established by touching hands. As soon as each
man has his position he drives his pick into the ground on the left
of his own task and lays his shovel on the ground, parallel to and
at a distance in the rear of the tape equal to the width of his task
from front to rear.

Rifles are then unslung, belts and canteens removed, and all
having been placed on the ground three paces directly to the rear
of task, butts of rifles toward the front, the men sit or lie down be-
hind their shovels until the order ''Commence tcork.''

110.— Extension of 2d and 3d Beliefs. Each man of the 1st
relief, after completing his task, scrapes his tools and lays them
together in rear of the trench.

The task being completed, each man secures his accoutrements
and rifle, and then, under direction of his officers, closes in to the
left (or right), forming column of fours, w^hich is then marched
back to camp.

As an incentive to rapid work, each relief should be allowed to
return to camp on the completion of its task.

If the working party be large and the work of a complicated
nature, each relief should arrive in successive detachments and
their location on the work should have l>eon previously designated,
so that there need be no delay or confusion, even at night.

Work should not be commenced until the distribution of the
entire relief is complete, since any change after work has begun
tends to confusion, loss of tools, and delay.

Working Parties. 73

111.— Tasks. An untrained workman can excavate in ordi-
nary soil one cubic j^ard of earth per liour for four consecutive
liours. As some men vrovk slower than others, however, it is
usual to estimate at G hours per man for the lifting of 4 cu. yds.
of earth from a trench 3.5 to 5 ft. deep and throwing the same a
horizontal distance of 10 ft.

When it is necessary to throw the earth more than 12 ft. hori-
zontally, extra shovelers should be provided for rehandling it, in
the proportion of 1 shoveler to every 2 diggers.

When exposed to the enemy's fire, a sliirmish line is kept well
to the front and the earth first excavated is thrown close to the
edge of the ditch, forming a screen which is gradually thickened;
under other circumstances the earth first excavated is thrown
farthest.

Five feet, or two paces, is the usual distance apart for men to
work, but they may be posted as close together as 4 ft., while using
the heavy pick and shovel. As a precaution against injury to ad-
jacent workers, the men should swing the pick in a direction per-
pendicular to the tape.

112.— Working parties may be extended at less or greater in-
tervals by making the corresponding changes in the commands:
when this is done, it will usually be necessary to verify intervals.

When necessary to complete a task in the shortest possible time,
or when the men available greatly exceed the number of tools,
working parlies should be formed in double rank, two men being
assigned to each set of tools, which should be carried by the front
rank man. When working in this manner with a double relief,
the men, under direction of non-commissioned oflScers, should
change off every 10 or 15 minutes.

Oflicers having general supervision of the work should not be
changed at the same time the reliefs are.

The sizes of tasks based on the 4 yd. rule may be arranged as
shown in diagram. (Fig. 4.) For arrangement of tasks in difficult
soil, see PI. 14.

CHAPTEB IX.— Bevetting Materials and
Bevetments.

113.- A Revetment is a facing used to hold up an embank-
ment at a steeper slope than it would assume naturally.

114.— Bevetting Materials. The revetments most commonly
used in field engineering are made either of brushwood in the
rough, fascines, gabions, hurdles, planlis, timber, sods, sand-bags,
pisa, adobe, or of a combination of two or more of these.

115.— Brushwood, which is used in mailing the first four,
should be of willow, birch, ash, hickory, or hazel, and is most pli-
ant when not in leaf: it may be of any size when used in the rough,
but should not exceed an inch in butt diameter for gabions and
liurdles and 2.5 in. for fascines and pickets.

The working party cuts and binds the brushwood in bundles
of about 40 lbs. each, putting the large and small in separate piles
with butts in the same direction. For convenience, the detail
should be divided into thrc^ parts— one for cutting, one for sort-
ing and binding, the other for carrying and, if necessary, loading.
Tools required and time necessary are as in "Clearing the Ground"
(Chap. v.).

116.— Withes (PI. 17, P'ig. 1), which are used for binding and
sewing, are made by twisting pliant rods. The butt is held under
the left foot and the twisting commenced at the small end, care
being taken to avoid breaking or kinking the rod. The pliancy' of
the rod may be increased by heating it. In using the withes for
binding, an eye is made at the small end, then the withe is passed
round the bundle, the butt passed through the eye and twisted
until a kink is formed, when the butt is thrust (buried) in the
bundle.

117.— Fascines. A fascine is a bundle of rods tightly bound
together. It has a length of 18 ft., a diameter of 9 in., and weighs
about 140 lbs.

Fascine Back. The fascine is made in a cradle rack of five
equidistant trestles (Figs. 2 and 4), the outer ones being 16 ft.
apart; the crotches are each 2.5 ft. above the ground and aligned.
The stakes for the trestles should be from 2.5 to 4 in. In diameter

PLATE 17

Fiff.K

-„-v.

a \ 6' Figure 4

Fig. 5.
Fig.6 Fig. 7 ^

Revetting Materials and Revetments. 77

and from 5 to 6 ft. in length. Those for the outer trestles are first
driven and securely bound together with wire or rope, then a line
is stretched from crotch to crotch and the interior trestles made
in a similar manner; the stakes should be driven firmly into the
ground and each should have a length of 2 ft. above the crotch.

Fascine Choker. For the purpose of gauging the circum-
ference of the fascine and for cramping it in binding, the fascine
choker (Fig. 3) is used. It consists of two stout bars or hand-
spikes, 4 ft. long, to each of which is attached a collar T8 in. from
the end, the collars being connected by a stout chain, to which
are attached two gauge links 28 in. apart. The choker is used by
a man on each side of the rack taking a bar of it and resting the
short end on top of the fascine, chain being underneath (Fig. 4,
*'a"); then each passes his bar over to the other (the short ends
passing around and under the fascine), and each bears down on
the end of his lever. (Fig. 4, "b.")

Making the Fascine. The trestles having been prepared,
the fascine is made by laying brushwood, trimmed if practicable,
in them, the pieces breaking joints and crooked ones being partly
sawed or cut through. The rods should extend from 18 in. to 2 ft.
beyond the extreme trestles and the bunch made of uniform size
throughout. (Fig. 4.) .

The choker should be used occasionally for testing the size, and
when of such dimensions throughout that the gauge rings meet,
the fascine is bound. This should be done with wire or tarred
rope, which is passed twice round the fascine and securely fas-
tened, the bindings being 12 in number, the two outer ones 3 In.
outside the extreme trestles and the others at intervals of about a
foot and a half. This allows the fascine to be cut into lengths of
6 or of 9 ft. Five men require about an hour to make a fascine.

118.— Gabions. Gabions are open cylinders 2 ft. in exterior
diameter by 2 ft. 9 in. in height, varying in weight from 35 to 50
lbs.: they are made of hrusJiicood, strap iron, iron bands or sheet iron
and from 9 to 14 pickets each. The interlaced brushwood in gabions
is called the watling or web. Gabion pickets should be 3.5 ft. in
length and from an inch to an inch and a half in diameter. The
rods for the web should be from one-half to three-fourths of an
inch in diameter, although smaller may be used. Wicker gabions
are most easily made with the aid of a gabion form, which Is a

78 Revetting Materials and Revetments,

circular piece of board 21 in. iu diameter, with equidistant notches
on its circumference, the number of notches depending on the size
of the brushwood and running from 9 to 14. (Fig. 5.)

The construction of the Wiclter Gabion (Fig. 7) is as follows:
Watling. The gabion form is laid on level ground and a
picliet driven vertically in each notch, the thick and thin ends of
the pickets alternating. The form is tlien slipped up the pickets
about a foot and held firmly in place by means of a rope, which is
tied loosely round the pickets just below the form and then tight-
ened by a rack stick (Fig. 6), the rope holding the pickets firmly
in the notches. The rods for the web having been stripped of
tlieir leaves, the web is commenced by laying the butts of two rods
in adjacent spaces between pickets, resting on the form. The rear
rod, passing outside the second picket, is then bent inward, pass-
ing over the first rod, inside the third picket, and then out. (Fig.
5.) The other rod, which is now the rear one, is similarly treated
and the watling continued by using the rods alternately. This
method of watling is called pairing. On coming to the end of a
rod a fresli one is laid alongside and woven with it for a short dis-
tance. The web is continued to within 3 in. of the ends of the
pickets, care being taken to keep the pickets vertical and to make
the web close by frequent use of the mallet.

Sewing. To prevent the web from coming off the pickets it
is then sewed with wire, heavy twine, or withes, in four places, as
follows: Take an end of a withe in each hand, the middle of it
resting on the web, pass the ends of it through the web about 6
in. down the sides, one from without inward and the other from
within outward; pull taut by bearing downward. Pass the ends
through the web again (5 in. farther down and tighten as before.
Proceed in the same manner a third time and then bury the ends
of the withe in the web. The sewing should be at equal inter-
vals and the two ends of the withe, when pushed through the
web, should be separated by two or three of the watling rods; wire
is much easier worked and more durable than withes. The partly
completed gabion is now inverted, the form removed, and the wat-
ling continued as before, until the gabion has a height of 2 ft. 9 in.,
when it is completed by again sewing as before explained. The
ends of the pickets that were driven into the ground are now
trimmed to within 3 in. of the web and sharpened, the opposite

Revetting Materials and Revetments, 79

ends sawed off to within an incli of the web, and a carrying picls:et
driven through the sides of the gabion perpendicular to the axis
and a few inches from it.

Three men should make a gabion in an hour.

119.— Wicker Gabion Without the Gabion Form. Where
the form is not at hand, the wicker gabion is made by first
describing on the ground a circle with a 10.5 in. radius and then
driving the pickets at equidistant intervals on this line. The
watling is commenced at the ground and run up to the full height,
care being taken by frequent " gauging to keep the dimensions
accurate. It will be necesary for one man to devote his entire
attention to keeping the pickets in position, While a second makes
the web, and a third prepares the rods. Three men should
make a gabion, without the form, in an hour and a half to two
hours. Instead of sewing, the gabion may be finished by driving
four forked pickets ^Fig. 8) in the web alongside of the gabion
pickets.

120.— The Hoop or Strap Iron Gabion. This is more dura-
ble and more quickly made than the wicker gabion, but is
heavy, weighing 55 lbs., and liable to splinter dangerously. The
form for this gabion is used solelj^ for gauging and shaping the
bands.

To make the hoops, ' describe on a wooden platform a circle
with a 1 ft. radius and divide it into (5 equal parts. Make auger
holes at points of division and insert in them wooden pins about
5 in. long and triangular in cross section, the bases of the tri-
angles being on the interior of the circle. (Fig. 9.) Wrap the
strap iron once tightly round the pins, thus forming an hexagonal
hoop. Mark the point where the hoop is to be joined, then remove,
punch, and rivet it. As the iron is usually 1 in. wide, the com-
pleted gabion will require 33 of these hoops.

To make the gabion, place a hoop on the ground and an-
other on it in the positions shown. (Fig. 10.) Drive a picket
vertically in each of the triangular spaces, then place the remain-
ing hoops alternately over the first and second. Drive nails in
four of the pickets outside the extreme hoops to keep the gabion
intact.

121.— The Sheet Iron Gabion. This gabion is made of a piece

80 Revetting Materials and Revetments.

of sheet iron 2 ft. 9 in. x 6 ft. 4 in., riveted or wired together along
its shorter edges.

122.— Hurdles. The hurdle is a brushwood mat 2 ft. 9 in.
wide by 6 ft. long, the length corresponding very nearly to the
circumference of the gabion. xVn even number of picliets, usually
10, is used in mailing it, the extreme picliets being somewhat
heavier than the interior ones. {Fig. 11.)

Construction of Hurdles. Describe on the ground an arc
with an 8 ft. radius, measure off 6' ft. of this arc and drive 10
gabion piclcets along it at intervals of 8 in. (Fig. 11.) Commence
the watling in the center space on the ground by randing— i. e.,
working with a single rod alternately inside and outside of the
pickets; on reaching the end picket the rod should be twisted as
a withe, so as to avoid breaking it, and then returned toward the
center in the same manner as at first. When approaching the
end of a rod another should be laid alongside of and randed with
it for a distance of two or three pickets. Pairing, as in gabions,
should be resorted to in finishing the top and bottom of the web,
and the hurdle should then be sewed as described for the gabion.
When the rods used in watling are very small the process of slew-
ing should be resorted to: this is the same as randing with the
exception that 2 or 3 rods are laid alongside each other instead of
using them singly. Slewing makes weaker work than randing.
Three men should make a hurdle in two hours; two work at the
web and the third prepares the rods. The completed hurdle
weighs about 50 lbs. The hurdle is made on a curve and after-
ward flattened as much as possible, because it is found that by
so doing it is less liable to warp than if made flat. It should be
placed in a road or revetment with the concave side toward the
earth.

123.— The Continuous Hurdle is usually preferred for revet-
ting purposes to single ones joined. It differs from the latter
in-that the pickets are driven at once, at intervals of 12 to 18 in.
according to their thickness, in the position the revetment is to
occupy, but at a slightly gentler slope, so as to allow for straight-
ening when the earth is tamped. It is constructed by randing or
slewing, two men being assigned a task of 10 or 12 ft. in length,
which they should finish to a height of 4 ft. and anchor, in from
one-half to three-quarters of an hour.

PLATE 18.

Revetments.

Revetting Materials and Revetments. 83

124.— Flanks, when used for revetting, should be placed
edgewise and held in position by stout stakes, which should be
anchored. They make a neat, durable and quickly made revet-
ment.

125.— Bound timber from 3 to 8 in. in diameter may be used
in the same manner as planks, but the revetment is more difficult
of construction and is not so durable.

126.— Sod for revetting purposes is cut of a uniform size— 18
in. long, 9 in. wide, and 4 in. thick. They should be laid in alter-
nate rows of headers and stretchers, grass down, breaking joints,
and perpendicular to the slope. The top layer should be all head-
ers and have the grass up; alternate rows should be pinned secure-
ly, using split pickets, if possible, as with them there is less liabil-
ity of splitting the sod than when round ones are used. Two men
should lay from 70 to 100 sods per hour, depending upon whether
or not pickets are used.

127. — Sand-bags are made of coarse canvas or bagging
material, and, when empty, measure 2 ft. 8 in. by 1 ft. 4 in. When
filled they are supposed to contain 1 cubic ft. of earth; it is found
in practice, however, that a cubic yard will fill from 48 to 50, mak-
ing their average size 1 ft. 6 in. long, 10 in. wide, and in. thick.
Each bag has eyelet holes near the mouth through which a stout
cord passes, to expedite tying, when filled.

For filling sand-bags the working party is divided into squads
of 6: 2 with shovels, 1 with a pick, 1 to hold the bag, and 2 to tie.

Each squad fills 150 bags per hour. This task may be consid-
erably increased, however, in easy soil or with trained men, and
the rapidity of the work more than doubled by having a double
relief and keeping the men constantly changing.

128.— Bevetments. Brushwood Bevetment is made by driv-
ing pickets at intervals of about 12 in. along the foot of the
proposed slope. The top of the pickets when driven should be
as high as the proposed revetment, and the pickets should be
anchored by wire to logs or stout stakes in the parapet. Loose
brushwood is laid closely behind the stakes and earth tamped
against it, the construction of the parapet going on at the same
time.

Brushwood revetment is rapidly made in daylight, but is neither
durable nor sightly.

84 Revetting Materials and Revetments,

129.— The Fascine Revetment. iPl. 18, Fig. 1.) This is
made by laying the fascines in single rows of stretchers, breaking
joints, each fascine being pinned to the parapet by 5 or 6 pickets,
and every second or third row securely anchored.

Six-foot fascines should be used occasionally as headers. The
bottom fascine is sunk about one-third of its diameter by excavat-
ing a shallow trench. The construction of parapet and revetment
proceed simultaneously. Slope should not be greater than four
on one. The defects of this revetment are the weight of the fas-
cines, the large quantity of brushwood required, and the fact that
the fascines are held in place by anchors and pickets in the earth
which they support.

130.— The Gabion Revetment. (Fig. 2.) This is made by
first sinking a row of fascines about 3 in. at the foot of the slope,
so as to give an inclination of four on one to the gabions resting
partially on them. Earth is tamped behind and in the gabions,
and sod or sand-bags placed on top. Where greater height is
required two rows of gabions may be used with two fascines, well
picketed, between them.

Gabions make one of the strongest and most durable revet-
ments, their own weight when filled being usually sufficient to
retain the embankment.

131.— Hurdles. These malce a poor revetment unless the
method is followed of constructing a '^ continuous hurdle" at the
same time with the parapet. To do tliis, the pickets are driven
along the foot of the slope at an inclination of about three on one,
when the final slope is to be four on one. The watling is made
continuous by randing or slewing, each two men having four
paces of hurdle as a task, and taking care to work in their rods
with those of adjacent sections. (Fig. 3.)

132.— Plank or Timber Revetment. (Fig. 4.) This is made
by driving heavy stakes into the ground at the proper angle, plac-
ing the planks or timbers behind them, then filling in and tamp-
ing firmly. The stakes must be anchored. This revetment is
neat and durable.

133.— Sod Revetment. (Fig. 5.) This is made by laying the
sod in alternate layers of headers and stretchers, grassy side down,
breaking joints and perpendicular to the face of the revetment.

Revetting Materials and Revetments. 85

Bach sod should be well setUed before another Is placed on it and
the top layer should be headers with grass up. It is well to
pin alternate rows by means of split pickets, three-fourths of an
inch in diameter and 9 in. long. This revetment is made of uni-
form thickness throughout by using double rows of stretchers.
If the grass is long it should be mowed. If the sod is very wet
when laid the revetment will crack in drying. Two men well
supplied with sod should lay two paces of revetment, four and
one-third feet high, in an hour.

This revetment has the advantage of not splintering like
gabions, fascines and boards, but should not be used when other
material is obtainable, because ordinarily it will not stand long
at a steep slope (three on one being about the limit), cannot be
used when very dry or frozen, and requires great care to build
properly.

134.— Sand-bag Bevetment. (Fig. 6.) This is made by lay-
ing alternate rows of headers and stretchers, breaking joints, and
perpendicular to slope, seams of stretchers and chokes of headers
being put in the embankment. Men working in pairs lay the
bags, settling them firmly in place with a mallet or spade. This
revetment is not very durable, but the bags are easily transported,
may be used with any soil, and are invaluable in making hasty
repairs and loop-holes.

135.— A very durable revetment (Fig. 7), much used in the
defenses of Washington, 18()l-5, was made of posts (oak, chestnut,
or cedar) cut in lengths of 5.5 ft. and placed side by side, at a slope
of six on one. The footing was a 2 in. plank laid in a trench exca-
vated for the purpose. The tops of the posts were sawed off 16
in. below the interior crest and capped by a half-round timber,
all being securely anchored in the parapet. Crowning was com-
pleted to the requisite height with sod.

All revetments that are liable to splinter should be crowned to
a height of at least 8 in. with sods, sand-bags or earth.

136.— Pisa Revetment is made of earth and clay, to which
has been added enough water to reduce the mixture to a working
consistency. A trench 6 in. deep and 18 in. wide is first dug, its
nearest edge marking the toot of the revetment. Pickets, of
suflftcient length to reach the top of the proposed revetment, are

Revetting Materials and Revetments.

firmly driven, at the proper angle, about 2 in. from the near edge
of the trench, at intervals of about a yard, and then anchored.
Boards placed horizontally are now laid against the pickets on
the trench side. The trench is then filled with the mixture,
tamped, and more added, other boards being placed on top of the
first, as required, and the mixture forced closely against them.
The construction of the parapet goes on at the same time with
the revetment. When completed, the pickets and boards are
removed. This revetment is neat and durable, but cannot be
rapidly made.

137.— The Adobe is a sun-dried brick, about 18 in. x 9 in. x
4.5 in., and when carefully laid with the same bond as given for
sod or sand-bag, forms a neat and very durable revetment, exceed-
ing in the latter respect any of the other varieties mentioned.

The following table shows amount of various materials re-
quired for 300 running feet of 4 ft. 4 in. high revetment:

Kind of Revetment

Fascines

Gabions

Sod

Sand-bags

Pickets

Fascines

Gabion

Sod

Sand-bag

30
6

267

400

1867

867

150
1000

PLATE la

CHAPTER X.— Field Casemates and Magazines.

138.— In all field works, protection against both weather and
hostile fire must be provided for the garrison.

These shelters are constructed by building a chamber of wood
sufficiently strong to bear the necessary earth covering, and by
protecting this in front by an embankment thick enough to with-
stand direct artillery fire.

Two general forms are used:

(1) Those which, after providing complete protection from
direct fire, have their roofs sloped to the rear at an angle greater
than the angle of descent of the enemy's projectiles, generally
about one on four; and

(2) Tiiose which have horizontal roofs, the earth covering being
so high and massive as to protect against artillery fire by its thick-
ness alone.

The first class is preferable, the work of construction being very
much less than in the second class, as the embankment is not so
high and the earth on the roof does not require to be thicker than
16 in., as it has to resist only the dropping fire of small-arms and
the fragments from bursting shrapnel. Moreover, it gives much
easier drainage to the ditch in rear.

139.— The construction of the timber part of the casemate is
practically the same in both cases. The vertical timbers being
rough tree trunks, about 1 ft. in diameter, placed at intervals of
3 or 4 ft., and strutted when necessary. The roof timbers in sim-
ple casemates being not less than 8 in. in diameter and the inter-
stices filled with small poles or brush. In case the protection has
to be proof against vertical fire of mortars, the earth mask on the
roof must be 6 ft. in thickness and a correspondingly stronger
timber construction must be provided: these are shown in PL 19,
Figs. 1 to 7.

In calculating floor space, each man should have from 9 to 18
sq. ft.; the former when crowded, the latter when not.

140.— Magazines are of two kinds: Fiist, those Intended to
hold the temporary supply for guns or troops when in action; and.

90 Field Casemates and Magazines.

Secmid, those intended for the purpose of storing ammunition in
large quantities.

The first variety consists of recesses in the interior slope of the
epaulement— barrels or gabions are excellent and when not obtain-
able may be replaced by empty ammunition boxes placed in holes
excavated for their reception.

Magazines of the second class are used only in works of great
defensive value and then only when ample time is available.
They are made in the same general manner as the casemates
heretofore described, except that great care must be taken to
render the structure as dry as possible and to secure good venti-
lation.

141.— The general plan of execution of these works is as
follows:—

(1) Magazine shown in PI. 20, Fig. 1.

The mask in front should be 20 ft. thick. The roof consists of
a row of timbers or logs 8 in. in diameter, overlaid with steel rails,
and then covered with a paulin, well tarred if possible. On this
is placed IG to 18 in. of earth. The ends are made of logs, 12 in.
in diameter, planted in a double row, breaking joints. The en-
trance is at either one or both ends according to circumstances.
The doors, 2 ft. G in. in width, are made of planks crossed, and are
hung next to the front wall of trench, opening into a passage
formed by a row of upright logs parallel to those on the end of
the magazine. At the end of the passage farthest from the first
door a second one is hung, opening into the magazine. The ver-
tical timbers in front and rear of trench support a revetment of
planks or hurdles. The floor should be raised at least G in. from
the bottom of the trench to guard against dampness. Care should
be taken to facilitate the draining of all water that fails on the
roof, and that the trench itself is drained away from the ends of
the magazine.

142.— Another form is as follows:— Determine the space need-
ed for storage of ammunition. Then build the timber work as
in the preceding, first excavating to a depth of 4 or 5 ft. over
the entire site. There will be no ends to be closed by timbers.
The roof is made of timbers 12 in. in diameter, well supported by
npriffhts of same size and long enough to give sufficient head

PLATE 20.

JWacKUtine behind naranet.

Field Casemates and Magazines. 9Ii

room. The sides and ends should be revetted with plank, if pos-
sible, and the floor raised 6 in. above the earth. The center of
the roof is raised a foot above the sides and surmounted by a
layer of 6 in. of earth, well tamped; over this is laid a paulin and
the earth mask is then placed over all to the thickness of 8 ft.;
the covering mass in front should not be less than 20 ft. in thick-
ness. Entrance is gained by means of a doorway opening into
a passage which communicates through a return with the inte-
rior of the magazine. Doors made of crossed planks are hung
as indicated in the plan. If time is available, and the planks
at hand, an interior chamber should be formed, leaving an air
space around the magazine proper; and inlets may be constructed,
care being taken that they are not situated in exposed positions
and that their course is such as to prevent the entrance of sparks.
The roof should be rounded off so as to afford the easiest drain-
age. If the earth excavated is not suflacient to cover the roof,
the necessary amount may be taken from a trench dug around the
outside.

This form of magazine may with advantage be placed in a
traverse.

143.— In case timber is not at hand, gabions and fascines may
be used to build the magazine in the manner shown in PI. 20.

144.— Block Houses are defensible shelters for infantry, al-
though, under certain circumstances, they contain artillery.

They are generally used for the purpose of flanking defenses
whose fire cannot reach into the ditch.

They are constructed either of upright timbers set in the ground
close together, or horizontal timbers laid one upon the other; the
timbers being in two rows, breaking joints in each case, or, if both
methods are used, the outside row should be horizontal and the
inner vertical. They should have at least C ft. of head room and
should not be less than 9 ft. wide, as this allows one row of beds
only. The roof should be of solid construction and covered with
earth to the thickness of 2 ft. and should project 2 ft. over the
wall to protect from dropping fire.

The walls should be masked with earth as high as possible and
a ditch dug around the entire building. Loop-holes are made at
the height of 4 ft. 4 in. and are cut according to circumstances,
as described in Chap. XIII. If necessary, block houses may be

M FieM Casemates and Magazines.

sunk in the ground, but a limit of 4 ft. in depth should be observed.
The shape will conform to the necessities of the case.

145.— In isolated positions they are advantageously made
cruciform, thus presenting an opportunity for flanking each face
of the house. When in wooded and mountainous countries,
where artillery is not to be feared, these houses may be made with
two stories, built so that the angles of the upper story project over
the sides of the other, forming a machicoulis gallery, thus prevent-
ing the occupation by the enemy of the dead space in front of
the straight walls.

146.— Caponiers are sunken block houses placed in the ditch
of fortified places to prevent their occupation by the enemy: they
are loop-holed about 18 in. from the ground, so as to have the most
effective plane of fire. (PI. 20.)

147.— Tambours are essentially block houses, having for their
object the protection of angles, and the flanking of sides of build-
ings, and are especially useful in defending doors of buildings.

CHAPTEB XI.— Field Works in Combination.

148.— Where several field works are used In conjunction, either
as an intrenched position or in the investment of a fortress, city,
or other important point, they constitute what is known as a Line
of W(yrks.

A Line of Works may be continuous, that is, forming, together
with natural obstacles, an unbroken line, or, with intervals, by
which it is understood that the works are distinct, either support-
ing each other or not, and the spaces between them not impassable
by reason of natural obstacles.

149.— Lines with intervals have the following advantages over
continuous lines, viz. :—

(a) They involve less labor.

(b) The garrison of the defenders may be smaller.

The general principle to be followed in their construction con-
sists in forming a line of fortified points or pivots. These points
or pivots detain the enemy's advance, since he would hardly pass
them and expose his flanks and rear, while a continued unsuccess-
ful attack on the strongly fortified pivots would open the way for a
counter-attack by the defenders.

When, however, the defense is intended to be solely passive,
which would be the case while awaiting reinforcements, or when
the enemy greatly outnumbers the defenders, the intervals would
be obstructed by felling trees or using any available obstacles,
since counter-attack is not contemplated.

In the use of lines with intervals, if the general defensive line
is straight the works could be blunted lunettes with flanks traced
so as to protect the front of adjacent works. If on a convex curve,
the capitals should radiate from a common center, while on a curve
concave toward the enemy, the capitals should converge and the
front of each work might be a straight line.

When impracticable to construct the main works of a line with
intervals, within supporting distance (600 yds. for infantry and
2000 yds. for artillery)* of each other, intermediate works retired

♦Continuous dangerous space for Springfield Magazine rifle is 610 vards.

96 Field Works in Combination.

from the main line, not more than half the interval, may be
used.

In PI. 21, Fig. 6, is shown sucli an arrangement, the pivots being
single, works while the artillery is retired from the main .line and
supported by infantry in shelter trenches.

Where the interval is as great as 1500 yds. it is advisable to
strengthen the pivots considerably, forming groups, the individ-
ual works of each group being so traced as to afford mutual de-
fense. (PI. 15, Fig. 2.) Each group is this latter arrangement
forms a strongly fortified point of support and would usually have
sufficient strength in itself to resist assault.

150.— Sometimes, when the defense of a line is of vital import-
ance to the defenders, a double Une of works is employed, the front
line being shelter trenches or open field works of slight profile,
the second line, not over 500 yds. in rear of the first, being field
works of strong profile.

151.— Artillery should, as a rule, be placed outside of and some-
what retired from the works and protected by their own gun-pits
or epaulements, for the reasons—

(1) That the works gain much in simplicity and rapidity of
construction.

{2) That this disposition draws the enemy's artillery fire from
the works and renders it more scattering.

(3) Greater mobility is given to the defender's artillery in case
of advance or retreat.

(4) A bettor tactical position for this arm can often be secured
than the one selected for infantry.

152.— As examples of continuous lines, PI. 21, Fig. 1, is known
as the redan trace with curtains. Fig. 2 is a modification of Fig.
1, the redans being blunted. Fig. 3 is the tenaille trace. Fig. 4
is a tenaille and redan trace. The cr6maillere trace (Fig. 5) has
long faces and short flanks.

With respect to the continuous lines above mentioned, the
preference on a level site would usually be given to the trace shown
in Figs. 1 and 2, the artillery being placed in the most favorable
position along the curtains, with machine guns in the most im-
portant redans.

The tenaille and the tenaille and redan trace (Figs. 3 and 4)
are objectionable, in that they involve more labor, cannot bring as

PLAtE 21.

FIG.1.
FI6.2.

FIG.5.

Field Works m Gomhinaiion. 99

direct a fire to the front, and the faces are liable to enfilade when
the salient angles approach 90°, while on the other hand, if a
salient, as "S," Fig. .4, approaches 120°, mutual defense of the
faces, "f* and "g," would be lacking, thus making the redan, "R,"
necessary. This trace may, however, be rendered unavoidable by
the conformation of the ground.

The cr^maillere trace finds special application in a position such
as is indicated in Fig. 5, viz., joining two points, one at the top and
tlie other at the bottom of a slope, the short flanks affording but
limited opportunity for enfilade fire.

153.— The strength of a defensive position lies in a great
measure in the proper utilization of the accidents of the ground;
thus, the traces that have been mentioned may have to undergo
considerable modification to be appropriate to the varieties of
terrain constantly met. It is evident that, in a broken or hilly
country, one by preference would occupy the heights. These, from
a tactical point of view, possess tlie advantage of overlooking
the low ground in front, besides the great advantage of conceal-
ing from the enemy the movements of our own troops in rear; but,
since all else must be subordinated to fire effect, it is evident that
such a line on the heights should be selected that the defenders
may completely cover the ground over which the enemy^must
approach. This naturally leads to the inquiry as to how that line
may be determined.

Heights, great or small, usually present the profile shown
in Fig. 7, that is to say, they have a steepest slope, "b c," which
is joined to the crest and to the valley below by the two gentler
slopes, "a b" and "c d." In order, then, to beat the :fone "b c'* it ,
is necessary to occupy the crest "c" or some point below it on this
slope. To distinguish this crest from others, it will be called the
military crest.

With the Inclination of this steepest slope greater than one on
four, it is unusual to construct anything but shelter trenches
along the military crest, the artillery being retired sufficiently and
placed in such positions as to command a good view of the rest of
the field. With gentler slopes, however, the artillery may be
placed at intervals along the military crest, the intermediate spaces
being held by infantry in shelter trenches. /

A better disposition than this, where t^ ground permits of it,

100 Field Works in Combination.

is to place the infanti-y trenches part way down the slope in front
of the military crest, the artillery occupying a position in rear of
and close to the crest, so that little more than the muzzles of the
pieces are visible. In this case, care must be taken that the infant-
ry trenches do not mask the fire of the artillex'y.

In choosing a defensive position the ground should be viewed
from the highest point in the vicinity, and by frequent practice the
eye so trained that the military crest is at once apparent and the
slopes instinctively classified with respect to their use by the
different arms.

Finally, the distance to a number of visible permanent points
in front of the works should be determined and recorded, so that
there may be no necessity for range finding during the enemy's
advance.

PLATE 22.

Plfif.l

-f< Fig. 2

mg.3.

Flsr,4

CHAPTER XII.— Siege Works.

154.— When it becomes necessary to besiege a place, it may be
approached by common trench work or by some form of sapping.
As the common trench and the flying sap are the work of infantry,
they alone will be referred to.

155.— The method of providing the working party with tools,
laying out the work, and extending the working party is described
in Chap. VIII. It is to be noted, however, in work of this char-
acter, t?KU when extending along a zig-zag^ upon reaching the angle
the order of forming up must be reversed. Thus, if the column from
b to c (PI. 22, Fig. 1) were forming on the left, upon reaching e f,
it would form on the right.

156.— Common Trench Work. This may be used as a par-
allel, an oblique approach, or communication. The work done
by reliefs in constructing a parallel is shown in Fig. 2. In this
case, as musketry fire must be provided for, the second relief cuts
out the top step. Should it be necessary to revet the bottom step,
fascines for this purpose may be carried by the second and third
reliefs. This may be and usually is omitted until the parallel is
completed. Fig. 3 shows the common trench used as an oblique
approach or communication. Should the trench be found wide
enough the task of the third relief may be omitted.

157.— The Flying Sap (Fig. 4) is similar to common trench
work, except that in the former case the embankment is revetted
with gabions.

In taking tools, each man of the first relief is, in addition to bis
pick and shovel, provided with two gabions. In laying out the
tools, a shovel should be fastened in one ga'bion by being placed
between two of the gabion pickets, handle of the shovel inside.
A pick should be secured in the other gabion by having its point
pushed under the pairing rods, handle inside. The gabion with
shovel is taken in the right hand, the one with pick in the left:
both gabions being carried by carrying pickets.

158.— The extension in the flying sap is made from single
rank on the right or left, and differs from the extension in com-

k.-

104 Siege Works.

mon trench work in that the interval, In the former case, is the
width of two gabions. Each man, on coming into line, places
his gabions so that they touch each other along the inner edge of
the tape, takes out his tools and lays them down, as explained for
working parties in Chap. VIII., and waits for the command, "Com-
mence work." In commencing work, the gabions should first be
filled; hence the position of each pair of gabions should be recti-
fied before this command is given.

159.— Each branch of a zig-zag should receive such direction
as not to expose it to enfilade fire from any point of the defenses.
Its prolongation should, therefore, fall outside of the most ad-
vanced salient of the collateral works. Ordinarily it would not
be longer than 100 yds. A parallel should be stepped in order to
facilitate an advance from it.

160.— A portion of the parallels and approaches used in the
capture of Fort Wagner, Morris Island, S. C, September 7th, 1863,
is shown in PI. 23,

PLATE 23.

TLATE 24.

R|ur* 1

CHAPTER XIII.— Defense of Localities.

161.— Walls. Should the enemy close on them, walls must be
so prepared that they will neither screen nor cover him, nor per-
mit his firing from them. To prevent this, obstacles may be
l>laced in front, or a ditch may be dug outside which will place him
Ko far below the top of the wall or the bottom of the loop-holes
that he cannot fire over the one or through the other. A total
height of 6 ft. will prevent this, or, in case of loop-holes close to
the ground, the maximum height should not be greater than 1 ft.
from the outside, or an embankment made in rear 18 in. high.

Notwithstanding these precautions, walls may still give cover;
hence they should be flanked wlien possible.

162.— In preparing walls for defense, tlie following cases
arise:—

(1) A wall less than 4 ft. liigh. Sinlv a small trencli on the in-
side to gain additional cover. P^ire over the top. (PI. 24, Fig. 1.)
Head cover should be provided with logs, sand-bags, or sods, sand-
bags being the best, sods next.

Additional protection against artillery may be obtained by heap-
ing earth from the ditcli in front against tlie wall, the thickness
depending on the kind of artillery the wall is to resist.

If this should be done, the ditch should not be too close to the
wall. A trench should be dug in rear to give cover to the supports,
or for the firing line when not firing from the wall.

(2) A wall between 4 and .5 ft. can be used as it stands, subject
to the same modifications as in the preceding case. (Fig. 2.)

(3) Between 5 and ft. a wall can be notched. The tops of
the notches may be filled with sand-bags, sods. etc. (Fig. 3.)

(4) Should the wall be higher than ft., a platform or staging
must be raised inside to enable the men to fire over the wall or
through the notches, or else the wall must be loop-holed.

163.— Loop-HoHng. Loop-holes for fire should not be closer
than 2 ft. 6 in.; ordinarily they should be 3 ft. To find the height.
hold the rife in the position intended to he vsed.

164.— To make a loop-hole in a wall (Fig. 4), 14 in. or less in
thickness, begin on the inside, to prevent the splay being toward

110 Defense of Localities.

the outside, by detaching a stretcher: the adjacent header on the
outside can then be knoclied out and the loop-hole roughly shaped.
Outside dimensions, 4 in. wide by 3 in. high. Interior dimensions
will depend on the nature of the ground over which fire is to be
delivered. For horizontal fire increase the bi'eadth, for elevated
or depressed fire increase the height.

In walls of ordinary thickness, a loop-hole can be made in
about 15 minutes, a notch in about 5 minutes.

165.— For a thick wall (Fig. 4), the small part should be at the
center, the loop-hole splayed to the front and rear, for it will do
this anyway. The side toward the enemy may be stepped, in
order tlmt bullets striking it may flatten. Loop-holes of observa-
tion should splay towards the outside.

All loop-holes, when not in use, should be blinded.

166.— The height or position of the loop-hole Is influenced as
follows:—

(1) 1 ft. above the ground. Men lying down in a shallow exca-
vation. Earth heaped up to 18 in. in rear prevents the enemy
from using the loop-holes should he close on the wall. The loop-
holes are a difficult mark for the enemy and sentries at night can
watch the sky line. Cannot be used where ground in front is
broken.

(2) Loop-holes 2 ft. 3 in. Sitting. Position easy, but must have
a deep ditch in front.

(3) Loop-holes 3 ft. Kneeling. Position strained and must
have a deep ditch in front.

(4) Loop-holes 4 ft. 4 in. Standing. Good command, but easier
mark for enemy: ditch necessary, but not so deep as in cases 2
or 3.

(5) Loop-holes G ft. or more. Men standing on banquette. Best
position for view or fire; no ditch in front; banquette strengthens
wall, but takes longer to prepare wall in this manner; more sus-
ceptible to artillery fire.

167.— In order to allow a double tier of fire, walls should be at
least 9 ft. high. (Figs. 5 and 6.)

168.— Fences. Fences should be removed or left standing
according to thoir position or direction. Wire fence forms a good
obstacle; a rail or plank fence forms a screen and may be banked

114 Defense of Localities.

(2) Broad Embankments. By occupying the front edge, a bet-
ter field of fire is obtained, but less cover can be provided for
the firing line, and the supports are exposed when coming into
action. (Fig. 2.)

171.— Cuttings are usually defended on the defenders' side,
since in this case retreat is easy and the cutting itself forms an
obstacle to the enemy's advance. But for active defense the front
edge may be held, and then a forward movement is possible. In
this case a means of retreat must be provided.

172.— Fig. 3 shows a case where the fall of the ground admits
of both sides of the cutting being occupied, giving a double tier of
fire. The command of the higher edge over the lower should be
about 6 ft.

173.— In case of a road cut, as in Fig. 4, the upper fence may
be used to sustain a breastwork, while the hedge below may be
converted into an obstacle.

174.- Woods.— (PI. 20, Fig. 6.) Preparation of edge of wood
occupied. The edge of a wood should be put in a state of de-
fense and an abatis is the readiest means of doing it. The sali-
ents should first be prepared, the reentrants next, and then roads
entering the wood from the enemy's side. Instead of an abatis,
the outer trees may be left standing and an entanglement made
by packing in among them smaller trees cut about 10 to 20 paces
to the rear. This clearing will serve as a communication all round
the edge of the wood.

If a reentrant bend is deep the abatis or entanglement may be
carried straight across it and flanked from the adjacent salients.
In case of a road, a lunette may be used instead of the abatis or
entanglement. In case there is not time to prepare the entire
edge of the wood, the salients may alone be prepared, the flanks
of the defense being turned back for a short distance into the
wood.

175.— Preparation of woods lying beyond. Woods beyond,
within rifle range of the line of defense, but too far to the front to
be occupied, and too extended to be felled, should have an abatis
or entanglement on the rear side to act as an obstacle.

176.— Cover. Trench digging is difl^cult on account of the
roots, but when possible it should l>e done. Cover is generally
obtained from the natural features. Trees, unless very large and

PLATE 26.

▼^ Fig. 6.

Defense of Localities. 117

standing thickly, do not give complete protection against artillery
fire. Troops as supports and reserves, if not so far to the rear as
to preclude their seeing through the wood to the front, may be
covered by log walls and trenches.

177. — Gommunications. (a) There must be good radial com-
munication as well as free movement along the boundary in rear
of the firing line.

(b) Roads and paths for bringing up the supports must be clear-
ly marked by blazing as well as by posting sentries at all cross
roads.

(c) In dense woods, preparations should be made for blocking
up roads by cutting trees on either side of them nearly through,
to be pulled down across them in case of retreat.

178.— Second and third lines may be placed along any open
space, brook, or broad road, parallel to the front. In case of brook,
the brook should be in front of defenders' position.

179.— Artillery should generally be placed outside of the
wood on the flanks. If placed in the wood, batteries should be
placed far apart, near good roads, masked as much as possible,
and each gun having more than one position. Reentrants are
desirable.

The number of defenders is estimated at 2 to 3 men per yard of
front.

180.— Stockades. Stockades are timber defenses, made by
placing one or more rows of timbers or rails upright or horizon-
tally, and so close to one another as to keep out rifle bullets, loop-
holes being made, through which fire is delivered. They have the
advantages of combining a parapet and an obstacle in one, giving'
good cover and ample interior space, and of being easily guarded
against surprise. On the other hand, -they require considerable
time for construction, a certain amount of skilled labor, and are
easily destroyed by artillery fire.

181.— Stockades would be employed:—

(1) Where timber is plentiful.

(2) When artillery fire is not to be resisted.

(3) When acting purely on the defensive. They are useful for
the rear faces or gorges of enclosed works, and may be a good deal
used in the defense of houses, streets, villages, and even woods.

118 Defense of Localities.

182.— Stockades of vertical timbers. Vertical timbers should
be close together, planted in the ground to a depth of 3 or 4 ft.,
according to their size and weight, pointed or spiked at the top,
and loop-holed at intervals. A ribband must be spiked along the
inside, near the top, to keep the timbers close together.

183.— PI. 25, Figs. 5, 6, and 7, show stockades with squared tim-
bers; Fig. 8 with round timbers squared where they touch and the
joint between every two trees made good on the inside by a
smaller tree.

184.— The loop-holes should be made in the crack between the
timbers, in order to avoid weakening them, half being cut out of
each. (Fig. 9.) In round timber, two saw cuts will make a loop-
hole. (Fig. 10.)

185.— The loop-holes should be cut before the timbers are placed
in position and the same precautions in regard to them as given
in walls should be observed. A loop-hole can be cut in from 10 to
15 minutes.

186. —In the foregoing cases, where the stockade is built of tim-
bers placed vertically, squared timbers are preferred, as they are
more easily fastened together and the joints made bullet-proof.
In round timbers the logs should be as straight as possible. If
very crooked, two complete rows will be required.

One N. C. O. and 10 men will erect 15 running feet of stockade
of squared timber, with one tier of loop-holes, in 8 hours.

187.— Stockades of horizontal timbers, iron rails, fascines, or
logs. (PI. 26.)

Fig. 1 shows stockade of rails and ties. Can only be used for a
very short distance, as it will involve an immense amount of plant.
Can be used to cover guns, close a road, and is more properly a
barricade.

Fig. 2 shows a stockade or log breastwork, banked in rear with
earth held in place by planks or hurdles and stakes.

Fig. 3 shows a stockade or breastwork of logs and fascines.

188.— Stockade work, both vertical and horizontal, can be used
for the construction of tambours (Figs. 4 and 5) and caponiers for
flanking walls or stockades and covering entrances. Tambours
may be triangular or rectangular in shape, arranged for one or two
tiers of fire, and covered with a splinter-proof roof.

Defense of Localities. 119'

189.— Buildings. Buildings may be used for defense, either
singly or in combination:—

(a) As tactical points in the battle-field, held either as advanced
posts or as supporting points in the line, or on the flanks, or as
rallying points to cover retreat.

(bj As lieeps to a more extensive position, such as a wood, vil-
lage, etc.

190.— In order to admit of use as a defensible post, a building
should possess the following requisites:—

(1) Solidly built of soft stone, brick, or adobe.

(2) Large enough to hold at least half a company.

(3) Sheltered from distant artillery fire; otherwise the building
cannot be held against infantry or cavalry.

(4) Well selected for the object in view.

(5) Low, fiat roof.

(6) Clear field of fire obtainable.

(7) Shape in plan affording fiank defense.

191.— The building should be looked upon as a fceep, or second
line of defense, a first line being prepared at a nUnimum distance
of 40 yds. to the front, this distance being the least that will
give the defenders immunity from splinters caused by shells strik-
ing the building.

192.— In falling back, the first line should retreat past, not
into the house, which should by this time be occupied By the sup-
ports. The garrison of the house may be estimated at two men to
each door, window, or loop-hole, with a reserve of one-fourth, tac-
tical unity being in this, as in all similar cases, adhered to as much
as possible.

193.— The following are the steps which must be taken in has-
tily preparing a house for defense:—

(a) Remove the inhabitants, also all easily combustible mate-
rial, and provide water and heaps of earth in each room.

fh) Barricade doors and ground-floor windows (bullet-proof if
possible), also mask inaccessible windows, and remove all glass.

120 Defense of Localities.

(d) Clear away cover in the vicinity as far as time and means
will allow.

(e) Open up communication throughout and prepare a means of
retreat.

194.— The same precautions as to loop-holing walls apply in case
of buildings. On the ground floor the horizontal dimensions of a
loop-hole should be greatest; on upper floors, the vertical dimen-
sion. If an artillery attacli is feared, slieltor trenches should be
provided outside the building on the flanks.

195.— Barricades for Doors may be made in the following
ways:—

(a) Fill boxes, barrels, cupboards, etc., with earth and place
them against the door itutidv.

(b) Build a wall of bricl^, stone, flag-stones, or hearth-stones,
against the door inside, and support by a shutter or another door.

(cj If railway plant is available, pile ties horizontally on one
another and secure with telegraph wire.

(dj Pile lumber inside the door and fix with blocks nailed to
the floor.

(e) Other methods may be employed in accordance with mate-
rial available.

196.— Should a door be reserved for use, it should be in a re-
entering angle of the building, if possible, and protected from fire.
A couple of cliests filled with earth and placed on rollers may be
used to secure the door. Similarly it may be possible to place iron
or wood on the door, thus rendering it bullet-proof.

197.— Windows. Windows must be barricaded as explained
for doors. If provided with shutters, these should be utilized.
Upper windows require to be bullet-proof only high enpugh to
cover the defenders. Bedding is no protection against modern
rifles, but may be used to mask windows of upper floors. If tim-
ber is used it should be placed vertically and nailed to horizontal
ribbands strutted back to the floor.

198.— If the house is large and strong and is to be held to the
last, in addition to the foregoing the following preparations should
be made:—

(1) Arrange for storage of provisions and ammunition.

(2) Set apart a place for a hospital.

PLATE 27

Fig.l

Flg2.

Fig.6,

TiTfWTtTmfllTmtinfrW

Defence of Localities. 123

(3) Prepare latrines.

(4) Loop-hole partition walls and upper floors.

(5) Make ready barricades to cover retreat from one part of the
building to another.

(6) If artillery is feared, shore up the floors and cover them
with about 3 in. of earth.

199.— Should the construction of the house not afford suffi-
cient" flank defense, it can be improvised in the shape of tambours
or caponiers, but the labor involved in their construction is consid-
erable and they would only be undertaken for the defense of a
very long wall or to cover an important entrance or communi-
cation.

For the latter purpose a machicoulis gallery is sometimes em-
ployed. (PI. 27, Fig. 3.) This is made by removing the wall of
the upper story where a window occurs down to the level of the
floor, running out two or three long balks so as to project a few
feet beyond the wall, the other ends being secured down to the
floor. On these planks are nailed, with holes cut through to act
as loop-holes, and a musket-proof parapet of planking, sand-bags,
etc., is built all around. A projecting veranda offers a favorable
position for this arrangement.

Second method: If a regular gallery can not be made, holes
may be cut in the w^all at a convenient height for a man to fire
downwards when leaning over, and a screen of wood or other
material may be secured outside for protection. (Fig, 4.)

If neither of the foregoing methods be possible, holes may be
made in the roof, through which grenades may be thrown on the
enemy.

200.— The materials most likely to be useful in preparing a
house for defense are sand-bags, stout timbers, such as railway
ties, large boxes, chests, barrels, coal-boxes, furniture and bed-
ding.

201.— PL 27, Figs. 1, 2, and 5, illustrate the more important
points in the defense of a house.

202.— Farms. Farms should be defended according to the
nature of the surface covering, the ground and the improvements,
and may involve the preparation for defense of walls, hedges, cut-
tings, embankments, buildings, woods, etc. Owing to their posi-
tions, farms may become very important and a great amount of

124 Defense of Localities.

fighting take place for their possession. They may occur either
in the main line of a position, as an advanced post in front, or as a
reserve station or rallying point in rear.

203.— Fig. 6 shows the principles of defense applied to a farm
lying in advance of a stream, which is a point that requires to be
strongly held. From the position of the farm it must be held sls
an advanced post.

The firing line is established along the fences bounding the
fields and orchard. The farm buildings are loop-holed and can
be held should the firing line be forced, while the fire from the
house would render occupation of the farmyard by the enemy
diflficult. Further to the rear, the wood is strongly prepared for a
final position, as shown in the figure.

204.— The rear of an advanced post should be left weak and
open to facilitate recapture.

205.— Villages. Villages can be rapidly prepared for defense
and, under favorable circumstances, obstinately defended; conse-
quently they are valuable supporting points in a defensive line.
Owing to the effect of modern artillery and the ability of burst-
ing shells to set villages on fire, great precautions have to be taken
in the preparation for defense.

206.— A village, when properly prepared and defended, may
have the following advantages:—

(a) Can be rapidly placed in condition for defense.

(hj Defense may be obstinate— tkus giving time.

(dj Provides a 'certain amount of cover from fire.

(e) Shelter from the elements.

On the other handl-
er/; The garrison is scattered, and hence the diflSculty of
supervision.

(h) When under artillei-y fire, splinters may cause many
casualties.

fc) Liability to be set on fire by shells.

207.— A village may be held with the following objects in
view:—

fa) As a supporting point in the main line of defense.

(h) As an advanced post in front of the main line.

PLATE 28.

Defense of Localities. 127

(cj As an independent post.

(d) As a reserve station or rallying point in rear.

In the first case, strengthen the front and flanks. The rear
should be prepared to resist infantry. In the second case, the
distance from the main line will govern the amount of prepara-
tion. If very distant, should be prepared for all-round defense.
If within rifle range, the rear should be left open, so that in case
the village is talsen, recapture will be facilitated. In the third
case, if an independent post, must be prepared for an all-round
defense. In the fourth case, if in the rear of the main line, must be
prepared for a protracted, all-round defense.

208.— Whether or not a village is to be held will depend on:—

(1) Its tactical value as compared with the number of men re-
quired to defend it.

(2) Whether it is practicable to provide a sufficient garrison for
its defense.

(3) Wliether it will be possible to demolish the village entirely,
in order to deprive the enemy of the cover it provides.

(4) On the form and nature of the surrounding country— i. e.,
no commanding ground within artillery range, foreground easily
prepared and the unimpeded advance of the defenders' troops in
the required direction easily arranged.

(5) On the shape of the village— whether broadside, salient, or
circular.

(6) Nature and materials of the houses.

209.— The first points to determine in preparing a village for
defense are how much of it will be defended, whether there are
buildings suitable for a keep or citadel, and whether or not these
are properly located.

210.— The arrangements for defense would be made in the fol-
lowing order:—

(1) Clear the ground toward the enemy. (See Chap. V.)

(2) Cover for the firing line, supports, and reserves. (See
Chap. IV.)

(3) Creating obstacles. (See Chap. VI.)

(4) Preparing communications. (See Chap. XVII.)

(5) Constructing retrenchments, citadels, or keeps. (See "Build-
ings.")

128 Defense of Localities.

211.— The garrison of a village may be estimated at two men
to the yard of perimeter to be defended.

212.— Salient Village. (PL 28, Fig. 2.) The successive lines
of defense must be carried well out to both sides and the flanks
well protected; otherwise the enemy may turn them and avoid
fighting in the streets.

213.— Broadside Village. (Fig. 1.) Here the outside fences
must be more utilized than the actual buildings, as the latter are
open to fire from artilleiy.

214.— Circular Village. (PI. 29.) Great attention must be paid
to the proper division of the village into sections for defense and
preparing and making the communications.

215.— In any of the foregoing cases, if cover does not exist for
supports and reserves, it must be provided, as the village will prob-
ably be shelled before being assaulted.

If artillery is to be used it should be placed on commanding
ground, inaccessible, if possible, to the enemey, and so that its
fire will sweep those parts most favorable to the enemy's advance.

PLATE 29.

^8-

CHAPTEB XIV.— Use of Cordagre and Spars.

216.— A rope is composed of three or more straads of fibrous
material, iron or steel, twisted together. The strands of fibrous
ropes are formed of threads; of iron and steel ropes, of wires. The
size of rope is denoted by its diameter in inches,* and is generally
sold by the pound. Fibrous ropes when new and dry stretch con-
siderably, when wet they contract; advantage is often taken of
the latter fact to tighten temporary lashings. Manila rope is only
about % as strong as hemp rope; tarred ropes only about % as
strong as untarred.

217.— A rule approximating to the breaking weight of a new rope,
in tons of 2,000 lbs., is to take one-fourth the square of the circum-
ference in inches. The strength of pieces from the same coil may
vary 25 per cent.

Ropes in daily use should not be worked up to greater than 1-5
their breaking loads, to meet the reduction in strength by wear
and exposure.

218.— The following table gives the approximate breaking
loads and weights of new Manila ropes, Swede's hemp center
Iron pliable ropes of 6 strands of 19 wires each, and hemp center
Steel pliable ropes of 6 strands of 19 wires each, Manufacturers*
Tests:

Diani. in

Breaking: loads i

nlhs.

Weight per 100
ft. in lbs.

Minimum Size of

Sheaves in feet
for Iron and Steel

inches

Manila

Iron

Steel

Manila ^-f

1-4

780

3 ... 1

3-8

1,280

5,000

7-16

1,562

6,200

12,000

61-8

1-2

2,250

7,600

15,000

5-8

4,000

11,000

24,000

13.5

3-4

5,000

17,500

36,000

16.5

3V4

7-8

7,500

23,000

50,000

120

9,000

32,000

66,000

158

14,000

54,000

104,000

250

20,250

78,000

154,000

365

30,250

108,000

1 212,000

525

36,000

130,000

250,000

115

630

♦In the Nnvv the size of rope is denoted by its circumference in inches. The
method used should be distinctly stated.

132 Use of Cordage and t^para.

219.— EnotSy Hitches, etc. The standing part of a rope is any
part not an epd.

A bight is a loop formed in a rope. (PI. 30, Fig. 1.)

Whipping is securing the end of a rope with twine to prevent
it from fraying out. (Fig. 1.)

Parceling is wrapping a rope to prevent chafing or cutting
against a rough surface or sharp edge. (Fig. 1.)

Stopping or seizing is fastening two parts of a rope together
without a crossing or riding. (Figs. 1 and 17.)

Nippering is taliing turns crosswise between the parts to jam
tliem. (Fig. 1.)

Splioinij is joining the ends of ropes by opening the strands
and placing them into one another (Figs. 2 and 3), or by putting
the strands of the ends of a rope between those of the standing
part. (Fig. 4.)

Rolling or stopper Mich, for fastening a rope to a strap or tail
block, and to secure a fall while being shifted on a windlass or
capstan. (Fig. 5.)

Or)crhand hrvot, to prevent the end of a rope from fraying out,
from slipping through a blocli, and the beginning of several other
knots. (Fig. 6.)

Figure of 8 knot, used in making cask piers. (Fig. 7.)

Square or reef knot, for joining the ends of two ropes the same
size. (Fig. 8.)

Thief knot (Fig. 9), with ends on opposite sides, and Granny knot
(Fig. 10), by crossing the ends the wrong way, both looking like
square knots, are to be avoided, as they will not hold.

Single bote or slip knot. (Fig. 11.)

Square hoiv, which can be cast off. (Fig. 13.)

Marlinspike hitch, used in putting on lashings, etc. (Fig. 12.)

Sheepshank, used to shorten a rope temporarily without cutting.
(Fig. 14.)

Two half hitches, for fastening the end of a rope around Its own
standing part. (Fig. 15.)

Round turn and two h^lf hitches, to secure guys to stakes, etc.
(Fig. 16.)

Jf*isherman*s bend or Anch4)r knot, for fastening a rop^ to ^n
anchor or ring. (F^g. 17.)

PLATE 30.

FIG.1.

:axaja

, — I 111 niiiiiiii I

ZZ2ZZ?

Fiot^^*^^ ^^-^ .:

FIG.8> ""

i^-W.^ fig;

Si^e^bau,^^h^ ;fc&,X^..'^7jQ;jfy ^^"^

£M

PLATE 31

nG.i5.

FIG.16.

Vse of Cordage and Spars. 137

Weaver's knot or sheet hend, for joining ropes of different sizes
without jamming. (Fig. 18.)

Double sheet bend, more secure than the single bend. (Fig. 19.)
Clove hitch, for fastening a rope to a spar; the end may after-
wards be stoppered to its own part. The clove hitch differs from
two half hitches only in being made around a spar or other rope
instead of around its own standing part. (Fig. 20.)

Timber hitch jams when made round a timber. (Fig. 21.)
Bowline, to form a temporary loop at the end of a rope. (Fig.
22.)

Bowline on a Ught, to make a loop on a bight. (PI. 31, Fig 1.)
Cafs paw, for applying a purchase or tacltle to the fall of an-
other. (Fig. 2, the beginning; Fig. 3, how applied.)
' Blackwall hUch, for fastening the end of a rope on a block in the
simplest manner, or fastening a rope in a hook. (Fig. 4.)

Mousing is a seizing placed around a hook to prevent it from
spreading or unhooking. (Fig. 4.)

Carrick bend, to fasten guys to a derrick. (Fig. 5.)
Lark's head, for fastening a bight to a ring. (Fig. 6.)
Capstan or Prolonge, making fast a spar. (Fig. 7.)
Wall hnot, for finishing off the end of a rope to keep from un-
stranding (Fig. 8), by passing the strands, as shown, then drawing
them down into a knot.

Wrapping is passing a rope around a lashing to keep the turns
together. (Figs. 14, 15 and 16.)

Straps are rings used for attaching tackles to spars or ropes.
(PI. 33, Figs. 1, 2 and 6.)

220.— To make a short splice. (PL 30, Fig. 2.) Unlay strands
of each end for a convenient length; take an end in each hand,
place end to end, strands sandwiching, and grasp the three strands
from opposite rope in left hand. Take a free strand, pass it over
the first strand next to it, then through under the second and out
between the second and third from it, then haul taut. Pass
each of the remaining six strands in same manner, first those of
one end and then those of the other, and so continue ^s far as
desired.

221.— To make a long splice. (Fig. 3.) Unlay strands of each
end, three or four times longer than for short splice, and place end
to end as described. Unlay one strand a considerable distance and

138 Use of Cordage and l^pars.

fill up its space with opposite strand from otlier rope, and twist
them together. Do the same with two strands on other rope.
Open remaining strands, divide in two, mal&e overhand knot with
opposite halves, and lead ends as in short splice. Gut off the other
two halves. Do the same with the other pairs of strands
where twisted together. Before cutting off any of the half strands,
first stretch, roll under the feet, and pound the rope well. This
splicing does not Increase the size of the rope and is used where
the splice is to run through blocl^s.

222.— To make an eye splice. (Fig. 4.) Unlay one end for
short distance, lay strands upon the standing part so as to form
the desired sized eye. Put first end through the strand next to
it. Put second over that strand and through second. Put third
through third strand on other side of rope and so continue. This
forms a permanent loop in end of rope.

223.— To sling a box or barrel. Lay a strong strap under
it, spreading the parts, and pass one bight through the other; or
malce a long loop with a bowline and sling as shown on PI. 31,
Fig. 9. If one head is out stand barrel up, put one part of a strap
under middle of bottom, take a half hitch over top with each part
just over bilge hoops and exactly opposite; or place rope under
barrel, bring up over top, make overhand knot, open it out and slip
each half down over hoops, fasten end to standing part with bow-
line. (Fig. 10.)

224.— Back lashings (Figs. 11, 12 and 13) are made with a 1-3
in. rope, 18 ft. long, with a loop at one end, and a rack stick 2 ft.
long, 1% in. in diameter, having a cord 4 ft. long through one end,
by passing the rope two or three times around the side rail and
balk, and, after making it fast, twisting it tightly with the rack
stick.

225.— Transom lashing. (Fig. 14.) The spars are laid across
each other at right angles, a clove hitch is made on one of the
spars, the end then twisted around its standing part, then three
or more turns are taken around the spars, under one and over the
other, keeping outside previous turns on one spar and Inside on the
other. Several frapping turns are then taken between the
spars and the end fastened on one of the spars with a clove
hitch. Used in lashing transoms to standards in bridge-building.

iFiai. ' FIG.2 PIG.3. ■ mA FIG. 5,

TiTn ^ fjnatchmock ^

Use of Cordage and Spars. 141

226.— Shear lashing. (Fig. 15.) The spars are laid parallel, a
couple of inches apart, on a block, a clove hitch made on one spar,
then five or six turns taken around both spars without riding.
Several frapping turns are then taken between the spars and the
end fastened on one of the spars with a clove hitch. This is used
in rigging shears for hoisting heavy weights, etc.

227.— Gin lashing. (Fig. 16.) The three spars are laid par-
allel, a couple of inches apart, the butts of the two outside ones
in one direction, that of the middle one in the opposite direction.
A clove hitch is made on one spar, then five or six loose turns
taken, passing over and under, without riding. Several frapping
turns are taken in each interval and the end fastened on one of
the spars with a clove hitch.

228.— Blocks, Tackles, etc. A pulley consists of a wheel, hav-
ing a grooved rim for carrying a rope, turning in a frame. (PI.
32, Fig. 1.)

A hlopJc (Figs. 2 and 3) consists of one or more grooved pulleys
or sheaves turning on an axle, called a pin, mounted in a casing
or shell, which is furnished with a hook, eye or strap on one end,
by which the block may be attached to something, and sometimes
with a becket on the other end for attaching ropes, etc. It is
used to transmit power, or change direction of motion, by means
of a rope or chain passing round the movable pulleys. Blocks are
single, double, treble or fourfold, according as the number of
sheaves or pulleys is one, two, three or four. The size of blocks
is expressed by the length of the shell in inches. A common style
of Ferry Block Is shown in Fig. 5.

A match hlocJc (FIcr. 4) is a single block with a notch cut in one
cheek so as to receive the standing part of a fall without the trou-
ble of reevincr and unreevlng the whole.

A rv/nninn hloek is one attached directly or indirectly to the ob-
ject to be raised or moved; a standing hlock is one fixed to some
permanent support.

229.— A tacJcle consists of two or more blocks- with a rope rove
through them for use in hoisting.

230.— The parts of all ropes between the points of fastening
and sheaves are called standing parts: the parts between the
sheaves are called nmnlng parts; the part to which the power !s
applied Is called the fait.

142 . Use of Cordage and Spars.

231.— To overhaul a tackle is to separate the blocks; to round in
is to bring the blocks closer together.

A tackle is said to be block and block or two blocks when the en-
tire fall is hauled through so the blocks are in contact.

232.— Before reeving a rope in a block, it should be stretched
out its full length. Tackle should not be allowed to twist; to pre-
vent it, insert a bar in the block or between the running parts and
use it as a lever to hold straight. If allowed to make one complete
turn with two single blocks, the friction will increase the resist-
ance about 40 per cent. Ropes should not be too large for blocks,
the rule being, ''Small ropes and big blocks"

233.— Power of Tackle. Theoretically, the power necessary
to just balance a weight, with a tackle of two blocks, is equal
to the weight divided by the number of ropes at the running
block.

234.— To produce motion, however, a greater power is required
to overcome friction and stiffness of rope. It has been found by ex-
periment that to do this about 10 per cent of the theoretical power
necessary to balance must be added to itself for each of the
sheaves over which tlie rope passes, the blocks being in good con-
dition and well oiled. If not in good condition and not well oiled,
the per cent may be as high as 30 for each sheave.

235.— The formula P = — ^--^ is used to determine the power
required to raise a weight with a simple tackle, in which P = the
power required, W = the weight to be raised, S = the number
of sheaves, and R = the number of ropes at running block, in-
cluding standing part if attached to it. If it is required to find
how great a weight a certain power will lift, the formula is
W =^Y^- Power is gained only at the loss of time. The power
moves as many times faster and farther than the weight as the
number of ropes at the running block. No advantage is gained
by using, in one fall, a greater number of sheaves than two
treble blocks, but may be by a combination of blocks and
tackles.*

236.— A squad of men hauling on a fall exert a pull of about

*The formula P = ^ ' is merely a simpli6ed forn; Qf tlie equation
P = (W + A W S) -H R, (^ee par.234.)

PLATE 33.

field. Capstan

' \

F1G.7

^>?;:-:-^^* .;■••;■;

'^■^s^^/^

"fie/t.

J^l

Use of Cordage and Spars. 145

80 lbs. (or half their weight) each, the fall being nearly horizontal.

237.— A Derrick (Fig. 7) usually consists of a single spar or
leg, held up by four guys, and having a tackle lashed to the top,
used for hoisting or lowering heavy bodies within a circle whose
diameter equals % the height of the spar. When made of two
legs (Fig. 8), they are mortised into a cap on top and a sill at the
bottom, only two guys being required, a fore and back, but three
are better, one fore and two back. The weight can only swing
between the legs. The holdfasts for the guys should be at a dis-
tance from foot of derrick at least twice its height. The foot
should be secured from slipping by being let into a hole in the
ground or otherwise.

238.— Shears (PI. 33, Fig. 1) consist of two spars, of a size suita-
ble for the weight to be raised, lashed together at the cross.

A tackle is fastened at the lashing by a strap passed around it
or otherwise, the hook moused, and holdfasts are required as for
two-legged derrick.

Two-legged derricks and shears should not lean to exceed 1-3
of their height, and each leg should have about % this inclination,
or 1-6 their height.

239.— A Gin (Fig. 2) is a tripod formed of three poles. The two
outside ones are called legs, the third one the pry-pole. Gins re-
quire no guys. Weights can only be lifted vertically.

240.— In using derricks, shears, and gins, the fall is generally
led through a snatch-block lashed on a leg near the bottom,
thence to a crab, windlass, or capstan. Derricks frequently
have fastened on their legs a winch for transmitting the power.
(PI. 32, Fig. 10.)

241.— A Windlass (Fig. 12) consists of a horizontal axis fast-
ened in a frame and turned by means of cranks or handles. The
rope may either be fastened to the axis or passed two or three
times around it, hauled taut, the free end being held, and taken
in by men in the rear.

242.— A Capstan (PI. 32, Fig. 9, and PI. 33, Fig. 3) consists of
'an upright barrel, either smooth or ribbed, arranged about a spin-
dle. Above the barrel is the head with holes to receive the ends of
levers or bars by which the barrel is revolved. The rope is passed
and held as explained for a windlass.
-10-

140

Use of Cordage and Spars.

243.--Holdfasts are stout wooden stakes driven into the
ground, or other arrangements used for securing purposes.

An essential point to be considered before moving or suspend-
ing heavy weights is the nature and condition of the securing
points, together with the strain that will be brought upon them.
In the first instance, it is better to make them more secure than
seems to be absolutely necessary, as, when they once begin to
give way, it is difficult to strengthen them. PI. 33, Figs. 4, 5, 6
and 7, show some of the various methods of making them,
also PL 40a.

243a.— An improvised Field Capstan, which is but an adapta-
tion oi the Spanish windlass, is shown in cut. One end of the rope
is made fast to the object which is to be moved and the other end
to a holdfast. A lever, a, is inserted in a bight of the rope and one
end of it placed against an upright bar, 6. The lever is then car-
ried round and round the bar, which revolves and gradually winds
the rope upon itself as it approaches the holdfast. The bar b can
be held upright more readily if the lever a is long enough for men
to work at both ends of it.

''^-

PLATE 34.

CHAPTEE XV.-Spar Bridges.

244.'-Military Bridges are not required to fulfill all the condi-
tious of ordinary bridges. They are constructed for special and
immediate purposes, usually with unskilled labor, and of such
materials as can be procured on or near the spot. That the bridge
built shall be strong enough to bear the heaviest load intended to
be crossed is the first requisite; celerity and simplicity of con-
struction next.

245.— PL 34 is an illustration of what was done in building
Militai-y Railroad Bridges under unfavorable circumstances in
time of war with troops of the line, very few of whom were
mechanics, many could not even handle an ax, none were trained
to the duty, and none w^ere engineer troops. This bridge was built
by General Haupt over Potomac Creek, Va., during the Rebellion,
and was 80 ft. high and 400 ft. long. It consisted of three tiers
of trestles on top of cribs 12 ft. high. The timber used was chiefly
round sticks, cut in the woods near by, and put together without
bolts, simply with spikes and wooden pins, and when finished, was
crossed by 10 to 20 heavily loaded trains per day. This kind of
work, however, properly belongs to a special construction corps,
but it falls to the lot of the oflflcers and men who first arrive at a
stream on the ordinary roads, where there are no means of cross-
ing, to construct an improvised bridge with such tools and of such
materials as may be available.

246.— The plans and expedients which follow have been select-
ed with a view to their being types of bridges that can be con-
structed by troops having no other tools than axes and augers, and
such materials as growing trees found in the vicinity, and beams,
lK)ards, ropes, wire, nails, etc., obtained from neighlwring houses
and towns. The purposes for which tlie bridge is to be used, the
nature of the crossing, velocity of stream, and kind of bottom, will
determine its strength, kind, size, etc.

247.— For a common road bridge, the load is assumed to be a
maximum when covered with men, estimated at 120 lbs. to the
square foot, plus the weight of the bridge, usually taken at about
80 lbs. per lineal foot. For reasons which are evident, the bridge
should be as short as possible, with good approaches. Swampy,
high, or steep banlvs should be avoided.

248.— Bridges usually take their names from some part of their

150 Spar Bridges.

construction, as Trestle^ Truss, Pile, Siirspension, or Floating Bridges,
The distance between supports (determined by the strength of
the balks to bear the desired load) is called the hay or spa/ti, and
the corresponding part of the bridge the span. The superstrvct-
ure, consisting of the stringers or ballis, the floor, the side-rails
and the fastenings, is of the same nature for each liind, as showu
in PI. 35, Fig. 1. The ends of the ballis rest on cross-pieces of the
supports called transoms; on the ballis (of which there are usually
five) are laid chess or poles, forming the floor; on top of the
floor, over the outside ballis, are laid side-rails or poles, which
are securely fastened every 4 or 5 ft. to the ball^s beneath by
racli lashings. Hand-rails (Fig. 2) should always be provided on
each side of the roadway. The usual width of military bridges is
9 ft. in the clear, between side-rails; 6 ft. will answer for Infantry
in column of twos, and Cavalry by file; 2.5 ft. for Infantry in
single file.

249.— For determining the strength of the materials to be used,
all errors should be on the side of safety. The practical method
is to place the ends of the timber on low supports, as far apart
as they will be in bridge; as many men as can then step on it
and jump up and down; or it is otherwise arranged so as to
bring as great a weight upon it as it will have to bear at any time
in bridge.

Where small poles of the usual number would not be strong
enough, a greater number must be used until the desired strength
is gained.

250.— Transoms must be strong enough to bear all the weight
that may be brought upon one bay of the bridge, considered as
distributed dead load on the transom. -

261,— The load in pmmds which any timber resting on two

points of support will safely bear, concentrated at Its center, may

bd*
be approximately determined by the formula 1-3 x -j— x O, in

which b = the breadth in inches, d = the depth in inches, 1 = the

length in feet between supports, and O is a constant in pounds for

the particular material of the beam,* 1-3 is the fraction of the

♦C is determined by takine a piece 1 in. square and 1 U. longbetween supports,
loading: it at the center until it breaks, then to the applied load adding one-half
the weight of the piece belween supports, and the sum will be C; or. a piece of
any convenient siise and length can be used, afterwards deducing what the
breaking weight would be for a piece 1 in. square and 1 ft. long, remembering
that the ^reakinv weight varies directly with the width, as the square of the
depth, and inversely as the length.

PLATE 35.

Spar Bridges. 153

breaking weight used for safety. It would, in all cases, be better
to use a smaller fraction of the breaking weight, as 1-5 or 1-6; or
even 1-8 in structures designed to be of a lasting character. The
formula is for a rectangular beam, but for a cylindrical timber
whose mean diameter equals the side of a square beam, use 6-10
of what the formula gives.

262,— Weight brought on a bridge by the pmsage of troops, taken
as distributed live load for Infantry and Cavalry: Infantry in
column of twos or fours, about 225 lbs. per lineal foot. Infantry
when crowded at a check in fours, about 550 lbs. per lineal foot.
Cavalry in column of twos, about 230 lbs. per lineal foot. Cavalry
when crowded at a check, about 350 lbs. per lineal foot. When
Artillery carrl^ages cross a bridge, the weight is not equally distrib-
uted, but is greatest when the wheels bea/ring the heaviest load are on
the center,

253.— A uniformly distributed dead load produces only one-
half the strain of an equal dead load concentrated at the cen-
ter. A moving or live load produces twice the strain of a dead
load. A uniformly distributed live load equals a concentrated
dead load.

Table of Constants C, for finding the breaking load of various

bds

materials by the formula -y-x C when concentrated at cen-
ter of beam supported at both ends. From Trautwine's
"Engineer's Pocket Book":

Ash, white 650 Elm 350 Oak, red & black..550

Ash, swamp. . . . ..400 Hemlock 400 Pine, white 450

Ash, black 300 Hickory .700 Pine, yellow 500

Beech, white 450 Hickory, pig nut. . 500 Pine, pitch 550

Beech, red 550 Locust 600 Poplar 550

Birch 450 Mahogany 450 Spruce 450

Cedar 250 Maple 550 Sycamore 500

Chestnut 450 Oak, white & live.600 Walnut 450

25^— The cubic contents of a log is approximately equal to
0.7854 times the square of the mean diameter times the length,
or the area of the mean section multiplied by the length; or the
square of one-fifth the mean circumference times twice the length,
all in feet.

255.— In calculating the strength of a round timber or spar,.

154 Spar Bridges.

its mean diameter is used, because such a spar, if overloaded, will
break at center, instead of at small end.*

256.— The following table gives the weights in pounds per
cubic foot of various materials:

Iron, cast 450 Chestnut 40 Spruce 31

Iron, wrought 487 Cottonwood 35 Sycamore 37

Lead 710 Hickory 43-49 Walnut 38

Steel 488 Maple 48 Clay 120

Ash 38-47 Oak 45-60 Earth 72-120

Cedar 35 Pine 34-40 Gravel & sand..90-130

Green timbers weigh from 1-5 to 1-2 more than those in table.

257.— When spars are used for balks, they must be arranged
so as to have all butts or all tips together on a transom. They
should have good overlap and be well lashed to each other and to
the transoms. To allow for settling, the center is generally made
higher by about 1-30 the span.

258.— For spa/ns of 25 feet or less, if timber is available, the sim-
plest form of stringer bridge could be built, as in Fig. 2, of 6
balks, 30 ft. long, reaching clear across, coverei^ with small poles
4 to 6 in. in diameter, 12 ft. long, for a floor. Side-rails would be
laid on the floor over the outside balks and either lashed or pinned
to the balks. Hand-rails would be as shown, or a rope stretched
across would answer. Time of construction— 1 hour. The balks
could be Jumped across as shown in either Figs. 3 or 4.

250.— If stringers of length to reach across cannot be obtained

♦For a bridare constructed as in Fie. 2, with six balks, to determine the safe
load it will carry, the application will be about as follows:

The balks being of yellow pine, 10 in. in diameter at the center, 25 ft. be-
tween supports, the formula gives ^(^ x J^ X J^' x 500 = 4,000 lbs. as the safe load
each balk will bear concentrated at the center, including its own weight. Cal-
culating for five balks, on the supposition that the two outside ones receive only
one-half the strain of the center ones, thev will bear 5 x 4,000 lbs. =- 20,000 lbs.
concentrated at center. From this deduct naif the weight of the balks and floor
concentrated at center, found bv multiplying one-half the cubic contents by the
weight per foot; for the six balks this will be

« X i [ (8)« X .7854] X 25 x 40 -= 1,636.25 lbs.
For the floor of seventy-five 4-in. poles, each 12 ft. long, the weight will be

76 X i X [ (^)» X .7854] x 12 x 40 = 1,570.86 lbs
20,000 lbs. — 3,207.11 lbs. ^ 16,792.89 lbs., ihe capacity of the bridge concentrated at
the cen«er. Infantry marching in column of fours crowded by a check would
cause a load of only about 13,760 lbs. Cavalry in column of twos crowded by a
check only about 8,750 lbs.

Similarly, knowing the span, the kind of material at hand, the weight to be
borne, etc., the size of timbers required can be deduced; or, having the size and
kind of the timbers, weight to be borne, etc., the greatest lengthUhat can be
spanned can be determined by the above for mul a.

PLATE 36.

FIG.1.

FIG.3.

Spar Bridges. 15/

or are too heavy to handle easily, a bridge as in Fig. 5 might be
made, requiring only axes and augers. The shore stringers, 25 ft.
long, 10 in. in diameter, six on each shore, have their bridge ends
scarped on upper side 18 in., then pushed out 10 ft., their shore
ends being well anchored down and loaded with roadway. Six
short stringers, 8 ft. long, 10 in. in diameter, three on each shore,
scarped 18 in. on under side of each end, are passed over gap and
laid on shore stringers. Two 2-in. auger holes are bored at each
end through both stringers and wooden pins driven through, and
the flooring completed.

260.— Paine's Bridge. (Fig. G.) If timber is abundant and
stream not over ft. deep, select trees up stream. Fell, and trim
off branches. Bore two 3-in. auger holes near butt ends 3 in. apart,
making an angle of 30° with each other, and a third hole, making
an angle of 45°, between them nearer the butt. Cut and insert in
outside holes legs long enough to raise the butt the desired height
of bridge. Float down stream, butt end first, to position of bridge.
On arriving in line of bridge, the log is turned on its feet, the tip
sinking to bottom. The brace leg is then inserted down stream
in last hole, making an angle of 45°. Log after log is thus placed,
balks rolled up and put into position and leveled, and the floor laid
in the usual way.

261,— For spans of 25 ft. or over, when bottom can be touched
clear across, some form of treble bridge will be the easiest of
construction.

262.— In PI. 36, Fig. 1, the trestle consists of G legs, 4 vertical
and 2 inclined; the two vertical legs on each side are fastened to
two short sills by 2-in. pins. The ends of the two inclined legs
are cut on an angle, driven into position, and held by 2-in. pins
passing through the transom from above. They serve as braces
and supports. A short horizontal piece pinned to each pair of ver-
tical legs supports the transom, which is also pinned. On top
of the projecting ends of the vertical legs a cap piece can be
pinned to form hand-rails. The trestle is made on shore, floated
to its place in bridge, and erected with the aid of a float held at
the proper distance from last trestle by a pole on each side, hav-
ing the lengths of the spans marked by pins which engage the
transoms of the trestles. The transoms are only temporarily
lashed in position at first, but after the trestle is erected in its

158 Spar Bridges.

proper place the proper height for it is determined by bringing
the 2 distance poles horizontal, or a little above the horizontal if
a camber is to be given, then pinning or spilting on the short hori-
zontal pieces. If accurate soundings have been made across' the
stream on the lines of the legs of the trestles, then the trestles can
be completed on shore before launching. The ball^s are then
run across and pinned and roadway finished. If there occurs
unequal settling, the roadway can be raised by blocking up under
tlie transoms on the short horizontal pieces.

263.— Fig. 2 is another form of trestle, called the Tie-block
Trestle, consisting of only two legs, about 8 in. in diameter.
The transoms are in pairs, across which two blocks are spiked at
each end into notches, as shown. This trestle can be used on
hard, uneven bottom. The trestle is formed on shore, held in
shape by the rope, and rack stick across the top, then floated Into
place. Two poles, longer than two spans, are then run out; on the
projecting ends are pins to prevent the trestle slipping off, and on
near end a rope for fastening to transoms of second trestle back.
Having caught the trestle on the ends of the poles under the
transom, it can be raised to a vertical position by men bearing
down on the rear, and held by means of ropes; it is then lowered
into position, legs in a vertical plane. The transoms are then
adjusted to their proper elevation by striking on under side, if
too low, then tightening rope; or by slackening the rope and stril?-
ing on upper side if too high. When properly adjusted, the rope is
tightened, pinching the legs between the blocks; the braces are
then spiked or pinned on, the rope removed, the balks laid and
pinned, and the poles shoved out for the next trestle.

264.— Where sufficient lumber can be procured, the most ex-
peditious and probably the best method will be as follows: (Fig.
3.) With the balks and chesses for each span, form a raft, or as
many as may be desired, the length of a span. Form a trestle
by placing four legs parallel and 4 ft. apart from center to center.
Spike a pole across near the bottom and one near the top to keep
them together. The first, or any trestle, having been set, float
a raft against it and make fastr bring the trestle to be set up to
the other end; force the legs under the raft a distance a little less
than the depth of the water. Tie a rope around the outside legs
at *T' with a bow-knot, to hold from slipping under, and others

8par Bridges. 159

to the top prfe, by means of which it is raised to a vertical position,
when it is dropped to the bottom by slackening off on lower ropes.
As soon as it is dropped, another raft is brought up, tied, and an-
other trestle put into position, and so continued. Each trestle, as
soon as it is in position, is then capped by nailing two boards
horizontally on opposite sides of legs with tops in same plane.
(Fig. 3, a.) Braces are then spiked on the legs. Saw off the two
inside posts even with the tops of boards. Spike a 2-ln. plank
across the top of posts and boards. Lay the balks, spike them,
remove the raft, and move it into position to raise another trestle.
If boards cannot be procured for capping, round sticks may be
used as in Fig. 3, b, by cutting the two inside legs off 5 or 6 in.
above the horizontal poles, then spiking two short pieces across
the poles against the outside legs and one In center on which the
cap piece or transom will rest. Advantages are— work can be
commenced in any number of places at the same time; no accu-
rate soundings required so long as poles are sufficiently long; cap-
ping and bracing do not retard work; different squads can be at
work at same time, etc.

265.— If only axes and rope are available, trestles may be made
by lashing their parts together. Fig. 4 shows the Two-legged
Trestle. Having determined the height of the roadway above
the bottom of the stream, mark this height from the butts on
both legs, then mark the position of the transom on the legs,
allowing for the thickness of the balks; also mark on the transom
for the width of roadway between side-rails plus 3 ft., for points
of crossing of legs, the distance apart of legs depending on
width of roadway. Give the legs a splay outwards at the bottom
of 1-6 and mark on legs and ledger the points of lashing. All be-
ing ready, lay the transom on a couple of supports 3 or 4 in. high,
inside the position of the legs, lay on the legs in their proper posi-
tions, on the legs lay the ledger. With the square lashing fasten
the four points of crossing. Next, lay on the braces, butts and
one tip on same side as ledger and one tip on side of transom.
Lash the butts with square lashings. Square the trestle by mak-
ing the diagonals equal, measuring from the center of ledger lash-
ing on one leg to the center of transom lashing on opposite leg.
When these diagonals are made equal the tips are lashed with
square lashings and the braces at the middle with a cross lash-

IGO Spar Bridges.

ing. Ledger and braces can be of rather light timber. The tres-
tles can be floated into position and raised as already described,
or run out and down from the end of the bridge, which is more
diflicult. They are kept vertical by lashing the balks to the
transoms, and longitudinal bracing from one to another.

266.— A Three-legged Trestle (PI. 37, Fig. 1) may be made
by first lashing two legs together considerably higher than the
roadway is to be, then lashing the pry-pole just below to one of
the legs, all with shear lashings. Stand the trestle up, spread
out legs till butts rest on the vertices of an equilateral triangle
whose sides are Vj height of trestle, then lash three light ledgers
to the legs by round lashings. On the outside of the pry-pole
and leg to which it is fastened are lashed short pieces, by square
lasliings, on which rest two longer pieces, separated by the legs,
which are lashed together by the shear lashing. On these longer
pieces rest the transoms. With these trestles lighter material
can be used; they stand without bracing, but are difficult to place;
accommodate themselves to inequalities of surface; the roadway
may be readily raised or lowered. If material is available, they
are readily made with spikes.

267.— Fig. 2 is another form of trestle of four legs. Two two-
legged trestles are made, one being 12 to 18 In. narrower than the
other, depending on the size of legs, so that they will lock when
put together. The transoms are placed on same side as ledgers.
Instead of on opposite sides. The butts of the single trestles are
placed a distance apart equal to half the height, then locked at
the top, the transoms lashed at the ends, longitudinal braces
lashed at the ledgers, the tips tied and racked together. Some-
times used with light material, also as steadying points in a long
bridge of two-legged trestles. One similar to it can be made of
sawed timber and spikes and placed in position as shown in Figs.
3 and 4, if the materials are available.

268.— In sluggish streams with muddy bottoms and not over
6 ft. deep, where timber is abundant, crib piers may be used.
(Fig. 5.) The cribs are built in the w^oods, the foundation logs be-
ing pinned together, the others simply notched. The logs are
then marked, taken down, carried or floated into position, and re-
built, poles being generally set to mark the corners. As the crib
Is built up it gradually sinks, or a tray may be formed inside and
loaded with stones. The balks and flooring are laid as usual.

PLATE Z7.

-11-

PLATE 38.

Spar Bridges. 165

S6t>w. — i't/e Ot iautis aie bcuiceiy aaapietl to au emeigeucy, Iroiii
the time and preparation requiiea in tneir construction, but on
lines of communication, trom tne cnaracter of tne bottom or ttie
dangers trom floating objects, resort may be bad to them.

270.— For driving the piles, a monltey (Fig. 8) is made of a
blocl^ of wood 3 ft. long, 12 in. in diameter, with four 1.5 in. pins
at top and four on the sides for handles. Four men standing on
a platform on the pile drive it down, their own weight thus assist-
ing, or they naay be driven from a raft built as in Fig. 6. After
the piles are driven they are straightened, braced, their tops sawed
off level, the caps placed on and pinned (PI. 38, Fig. 1), and the
roadway laid as usual. Piles near shore may be driven as in Fig. 7.

271.— For cros^ngs greater than 25 ft. and too deep to use any
of the above forms, resort must be had to some form of truss
bridge. The trusses may be put together either by lashing or
with pins, or by combinations of both.

272.— PL 38, Fig. 2, represents the ordinary King-post Truss
for spans up to 40 ft. The bridge is put together on the banlc,
then pushed forward half its length, using rollers under each
truss, as shown. A trestle is then leaned forward from opposite
bank, and, when truss is over it, the trestle is raised and the end
of the truss carried over to the opposite banlc.

273.— Fig. 3 represents the Queen-post Truss for spans up
to 50 ft. It is constructed and carried across similar to the pre-
ceding one.

274.— Fig. 4 shows the Single Lock for spans of 30 ft. It con-
sists of two frames similar to the two-legged trestle on PL 36,
Fig. 4. A section of the gap is first marlsed out on the ground on
each bank with the positions of the footings indicated. On these
the legs are laid and the positions for lashing the transoms and
ledgers marked. The frames are then put together opposite the
position they are to occupy (one on each bank), butts towards the
gap. One frame is made 15 to 18 in. wider than the other so they
will lock, and the footings should be likewise prepared. The dis-
tance between legs at transom of narrower frame is 18 in. more
than width of roadway between side-rails. With the above excep-
tions the frames are made like the two-legged trestles. The splay
of the legs is very slight, generally about 1 ft. between transom
and ledger. Stout stakes are then driven at the rear, fore and

IGG Spar Bridges.

back guys are attached to the tips of each frame, the fore guys
crossed over the stream, those of narrower frame in center. Foot
ropes are also attached to each leg near the butts with timber
hitches and a turn taken around the stakes at the rear. The frames
are then shoved over the banks till they balance (PI. 40, Fig. 1),
then brought to a vertical position by hauling on the fore guys,
and lowered into their places by easing off on the foot ropes,
after which they are pulled over and locked. A couple of balks
are then run out, then the fork transom is put into place and the
balks rested on it. The remainder of the balks are then run out,
placed on the fork transom, lashed, and the roadway completed
as usual. If good places for footings cannot be secured, then
other means must be provided.

27b.— For spcms up to 45 or 50 ft., the Double Lock (PI. 39,
Fig. 1) may be used. In this it will be noticed that the balk-
bearing transoms are not the transoms first lashed to the frames
in making them, but those which are sent out after the frames
are in position. This must be remembered in marking the posi-
tions of the transbms on the legs of the frames. In this the
two frames are made as described for the single loclc, except that
they are of the same width. They are launched as described,
and pulled forward until their tops are about 1-3 the span apart.
Two straining beams are then run across, the road-bearing tran-
soms fastened on top of them in the positions previously marked.
The frames are held by the back guys until all is ready, when
they are eased off and the bridge locked. The roadway is then
laid as usual.

27Q.— For spans greater than 45 or 50 ft., where timber of suffi-
cient size is obtainable, the Single Sling or Treble Sling may be
used. The frames are made as has been described, with the fol-
lowing additional observations:

In the Single Sling (Fig. 2), in marking the positions of the dif-
ferent spans, the three locking pieces must be at least 9 or 10 ft.
above the roadway. The fork piece is hauled into position by
snatch blocks lashed to the top of each leg of narrower frame,
after which the blocks are used to get the center transom tempo-
rarily into position, when it is slung by the ropes that are to hold
it, by taking several turns around it and the locking pieces with-
out riding, and afterwards twisted up to the proper height with
a pole.

PLATE 39.

. Double Lock

£/4

PLATE 4a.

Spar Bridges. 171

277.— In the Treble Sling (Fig. 3) there are three slung tran-
soms, one from the forks and one from the standards on each side
of the middle. The frames are constructed as already described
(PL 40, Fig. 2, being one in plan.) If necessary, the fmmes may
be strengthened by additional braces on them and further braced
back to the banks by ropes attached to holdfasts and otherwise
as suggested on PI. 40, Figs. 4 and 5, vertical braces being shown
in Fig. 3.

278»— Other expedients for crossing small gaps are the use of
wagons in various ways for supports, brushwood made into
gabions, fascines, etc. (P'lgs. 6 and 7.)

279.— A light, portable truss (Fig. 11) can be made, where
boards are obtainable, by describing two arcs of circles with
radii 151 ft., on opposite sides of a 60 ft. chord, then driving
stakes on the arcs at intervals of about 2 ft., against which 5
layers on top and 6 layers on bottom of boards 1 in. thick x 12
in. wide, breaking joints, are bent and securely nailed together
every 4 in. with tenpenny nails. The lower side of truss is made
one board thicker than the hpper and is completed by driving
6 in. spikes through every 6 in. This truss will be about 6 ft.
deep, and, allowing 2 ft. at each end for resting on supports, will
bridge a span 56 ft.'

The sides are connected every 5 or 6 ft. by vertical pieces of
plank and two 1-in. iron rods, the latter on the sides of the verti-
cals, towards the middle. If iron rods are not obtainable, rope or
wire should be wrapped around both and twisted tightly. The
angles at the ends are filled with wedge-shaped pieces and the
ends securely bolted, hooped, or wrapped. (Fig. 9.) For greater
rigidity, light diagonal braces may be inserted in the panels.
The top can be made straight instead of curved if so desired.

These trusses are used in pairs and are applicable to a variety
of structures and to spaces of considerable width. Two such
trusses with a central support of trestles, crib-work, or boats, may
be used for 116 ft. (Fig. 11); three such trusses for 176 ft., etc.
In experiments with such trusses in bridges, 1800 lbs. per lineal
foot has been applied before breaking; and by covering the boards
with pitch and tar before nailing together, inserting 14 in. bolts
in pairs every foot of length on lower side, and nailing boards
against the edges, 3500 lbs. per lineal foot was applied before
breaking.

172 Spar Bridges.

280.— Sxispension Bridges. l^or spans greater tliau 00 it.,
and when timbers for frames cannot be procured, some form of
suspension bridge migiit be used. Aitliough applicable to longer
spans, and the materials more easily transported, they take longer
to make than other kinds.

The cables may be of iron chains, iron, steel or fibrous ropes,
or of boards nailed together.

281.— PI. 40a, Fig. 1, shows one with the roadway hung below
the cables, with a camber 1-30. At the center, the roadway
should be at least 1 ft. below the cables. The width of roadway
between side rails should be only slightly wid^r than wagon-wheel
tracks. (Fig. 2.) On the banks, the cables are supported by tim-
ber piers (Fig. 3), having a broad cap (Fig. 4), rounded on top,
over which they pass at a distance apart of 9.5 ft. The cables
must be securely anchored at the rear to heavy logs sunk 4 or 5
ft. in the ground, or otherwise, and drawn in until the sag is only
1-10 or 1-12 of the span.

282.— In Fig. 5, part of the roadway is hung below and a part
rests on the cables, the greatest slope of road being 1 on 6 for 100
ft. span and 1-10 sag. The cables are only 7 ft. apart.

283.— In Fig. 6, the roadway is built on trestles supported on
the cables. For spans 130 ft. sag 1-12, the frames form the sides
of equilateral triangles of 10 ft. each. To construct it, the curve
of the cables is traced on the ground, the trestle legs laid on it and
marked where they cross the road and cable; those for each half
of the bridge are ranged in order on the banks, connected together
as placed on the cables and hauled out, connected at the center,
the curve of the cables adjusted and the bridge completed.

284.— Fig. 7 is a suspension bridge of which the cables are
made of boards nailed together in several thicknesses laid hori-
zontally, breaking joints; the ends are spread apart and wedge-
shaped blocks inserted and anchored by several rows of posts, as
shown in Fig. 8. Each cable, as made, is drawn across by ropes,
anchored, and the trestles placed from both ends at the same
time. liast of all, spikes long enough to reach entirely through
the cable are driven every 4 to 6 in.

285.— Fig. 11 is a similar bridge supported on trestles 16 ft.
long, not exceeding 20 ft. high, placed at intervals of 40 ft., over
which suspends the two board cables, 14 ft. apart. On these are

PUTE 40a.

Spar Bridges. 173

placed low trestles, 3 ft. high, dividing the spans into lengths of
20 ft. each; 25 ft. ballis are used and the roadway laid as usual.
The cables are made of six thiclinesses, of 1 in. boards 12 in.
wide, breaking joints, nailed and spilied every 4 to 6 in., and bolt-
ed by pairs of % in. bolts every foot. Three thiclinesses of boards
are first nailed together and drawn across, the ends anchored, and
then the other three boards added.

286.— For light foot bridges (Fig. 10), across narrow gaps, wire
from fences, if available, could be used for the cables by twisting
a number together and passing them over crotches of trees and
anchoring to stumps, etc., in rear, and then laying the walk simi-
lar to some of the methods previously shown.

287.— So various are the conditions to be met in constructing
bridges that seldom will any one type meet the requirements, but
by the application of good judgment and resource, with the sug-
gestions here offered, almost any gap of reasonable width may be
crossed, if not by one type or another, then by a combination of
several to meet the emergency.

The varying strength of timbers makes it almost impossible to
give exact dimensions for the different spars to be used in the
different types, but a general idea may be obtained below of the
amounts and average dimensions of medium strength timber, as
yellow pine. For weaker timbers some of the sizes will have to
be increased, while for stronger ones there will be an excess of
strength if the sizes given are adhered to, but the desire to be on
the side of safety warrants the use of amounts which might, by a
careful mathematical calculation, appear to be excessive.

The timbers for transoms, ledgers, braces, balks, flooring and
side rails should be selected of as nearly a uniform diameter
throughout as possible and will be so considered in giving dimen-
sions. For legs or standards the diameter at tip will be given.

For a 9 ft. roadway withlS ft. spans, 5 balks 20 ft. long x about
6 in. in diam. are used, and placed 2^4 ft. apart from center to cen-
ter. For the flooring are used poles 11 to 12 ft. long x 4 to 5 in.
in diam. For side rails 2 poles 20 ft. long, 4 to 6 in. in diam.

For each Six-legged Trestle (PI. 36, Fig. 1) 4 vertical and 2
bracing legs 6 in. diam.; 1 transom 12 ft. x 8 in.; 2 foot pieces 3 ft.
X 8 in.; 10 oak pins 2 in. diam.

For each Tie-block Trestle (Fig. 2) 2 legs 8 in. diam.; 2 tran-

174 Spar Bridges.

soms 15 ft. X 8 in.; 4 tie blocks 2 f t. x 5 in. x 6 in.; 2 braces 3 ft. x
2 in. X 6 In. ; 24 spikes, 1 rope, 1 rackstick.

For each Capped Trestle (Fig. 3) 4 legs 8 in. diam.; 2 braces
12 ft. X 4 in.; 2 braces 15 ft. x 5 in.; 3 boards 12 ft. x 2 in. x 12 in.;
4 ropes, spikes.

For each Two-legged Trestle, lashed (Fig. 4), 2 legs 4 ft.
longer than height of trestle, 5 to 7 in. tip; 1 transom 15 ft. x 9 in.;

1 ledger 16 ft. x 4 to 6 in.; 2 braces 3 to 5 in. diam.; 6 ropes 30 ft. x
^^ in. diam.; 3 ropes 15 ft. x i/^ in. diam.

For each Three-legged Trestle, lashed (PI. 37, Fig. 1), 6 legs 3
to 5 in. tip; 4 transom bearers 6 ft. x 3 to 4 in.; 4 sticks 2 ft. x 2 to
3 in.; 6 ledgers 2 to 3 in. diam.; 1 transom 15 ft. x 9 in.; 12 ropes
30 ft. X Va in. diam.; 6 ropes 15 ft. x ^ in. diam.

For each Four-legged Trestle, lashed (Fig. 2), twice the
amount given for each two-legged trestle, plus 2 ledgers, and 6
lashings 15 ft. long.

For each Single Lock (PI. 38, Fig. 4) 4 legs 22 to 25 ft. x 7
in. tip; 1 fork transom 15 ft. x 10 in.; 2 frame transoms 15 ft. x 6
in.; 2 ledgers. 15 ft. x 4 to 6 in.; 4 braces 20 ft. x 3 in.; 2 shore sills
15 ft. X 6 in. Lashings, 4 transom 50 ft. x % in.; 14 ledger and
brace 30 ft. x ^^ in.; 10 balks 20 ft. x 1-3 in.; 4 foot 50 ft. x lin.; 8
guy 150 ft. X 1 in.

For each Double Lock (PI. 30, Fig. 3) 4 legs 22 to 25 ft. x 7 in.
tip; 2 straining beams 25 ft. x 8 in.; 2 road transoms 15 ft. x 10 in.:

2 frame transoms 15 ft. x 6 in.; 2 ledgers 15 ft. x 5 to 6 in.; 4
braces 20 ft. x 3 in.; 2 shore sills 15 ft. x 6 in. Lashings, 8 transom
50 ft. X % in.; 14 ledger and brace 30 ft. x % in.; 10 balk 20 ft. x
1-3 in.; 4 foot 50 ft. x 1 in.; 8 guy 150 ft. x 1 in.; besides axes and
other tools, and anchorages, holdfasts, etc., on banks.

For each Single Sling (Fig. 2) 4 legs 35 to 45 ft. x 6 in. tip;

3 top and fork transoms 15 ft. x 6 in.; 3 road transoms 15 ft. x 10
in.; 2 ledgers 15 ft. x 4 to 6 in.; 4 braces 20 ft. x 3 in.; 2 shore sills
15 ft. X 6 in.; 10 balks 30 ft. x 6 in.; 4 side rails 30 ft. x 4 to 6 in.
Lashings of same number, size and length as for Double Lock.
Stiffening will require additional spars and lashings, depending
upon the method used.

For each Treble Sling (Fig. 3) 4 legs 50 ft. x 6 in. tip; 5 road
transoms 15 ft. x 10 in.; 3 top and fork transoms 15 ft. x 6 in.; 2

&par Bridges. 175

lower ledgers 15 ft. x 4 to 6 in.; 4 lower braces 20 ft. x 3 in.; 4 upper
braces 18 ft. x 3 in.; 2 shore sills 15 ft. x 6 in.; 15 balks 5 ft. longer
than 1-3 span x 6 in. ; 6 side rails 5 ft. longer than 1-3 span x 4 to
6 in.; 6 sling racking sticks 10 ft. x 4 in. LashingSy 4 foot 50 ft.
x 1 in.; 8 guy 1.50 ft. x 1 in.; 24 ledger and brace 30 ft. x l^ in.;
8 transom 50 ft. x % in.; 40 or 50 balk 20 ft. x 1-3 in. Stiffening
will require additional spars and lashings, depending upon the
method used.

For Suspension Bridge 200 ft. long (PI. 40a, Fig. 1) 4 to 8 ca-
bles 180 ft. X 1 in.; 16 cable seizings of yarn 18 ft. long; 12 lash-
ings 50 ft. X 2-3 in.; 10 lashings 30 ft. x Va in.; 100 lashings 20 ft.
X 1-3 in.; 2 steel wire cables 400 ft. x 1 2-3 in.; 4 standards 26 ft. x
10 in. tip; 4 braces 22 ft. x 3% in. tip; 2 caps 12 ft. x 10 in.; 2 sills

15 ft. X 10 in.; 4 back struts 36 ft. x 4 in. tip; 4 side struts 32 ft. x
3 in. tip; 4 cable props 30 ft. x 5 in. tip; 4 horizontal ties 30 ft. x
3 in. tip; 21 transoms 10 ft. x 6 in.; 80 balks 13 ft. x 6 in.; 40 side
rails 20 ft. x 6 in.; for anchorages 16 spars 5 ft. x 7 in. tip; 2 spars

16 ft. X 20 in.; 2 spars 16 ft. x 12 in. % round; 10 spars 16 ft. x 8
in. % round; 4 back ties 50 ft. x 2-3 in. steel rope; 4 ties 35 ft. x V2
in. steel rope; 40 slings total 600 ft. x % in. steel rope; 4 guys 50
ft. X 1 in. ; 4 rope ladders.

For Suspension Bridge 100 ft. long (Fig. 5) 4 to 8 cables, 12
cable seizings, 4 lashings, 12 lashings, 30 lashings as above; 2
cables 180 ft. x 3 in. hemp or 2 in. steel; 2 anchor spars 18 ft. x 15
in.; 10 transoms 12 ft. x 4 in.; 4 balks 25 ft. x 6 in.; 10 side rails 20
ft. X 4 in.; materials for piers depending on circumstances.

For Suspension Bridge 130 ft. long (Fig. 6) 4 to 8 cables, 12
cable seizings, 9 lashings, 104 lashings, 280 lashings as above; 4
cables 200 ft. x 2 2-3 in. hemp or 1% in. steel; 2 anchor spars 18 ft. x
18 in.; 44 trestle legs 13 ft. x 3 in. tip; 44 braces 15 ft. x 2 in. tip; 22
transoms 9 ft. x 4 in.; 80 ledgers 12 ft. x 2 in.; 20 cable ledgers 12
ft. X 5 in.; 2 shore sills 10 ft. x 5 in.; 48 balks 14 ft. x 5 in.; 28 side
rails 20 ft. x 5 in.; materials for piers depending on circumstances.

Besides the above materials, there will be required tools for
cutting timber, tackles for raising frames, shovels, pickets, etc.,
and, where not mentioned, the ordinary amounts of balks, chess,
side rails, etc.

-12-

CHAPTER XVI.— Floating Bridges.

288.— The passage of a stream may be effected, in many cases,
as described in the preceding chapter. If the methods there laid
down are not suitable or expedient, and the stream cannot be
forded, then resort must be had to ferrying by boats, rafts, flying
bridges, or to floating bridges.

289.— The selection of a place and means of crossing a river
is determined by a reconnaissance, which should be as detailed
. and extensive as circumstances will permit, and embrace the
following:—

fa) The nature of the banks.

(bj The nature of the bed.

(d) Strength of the current.

(e) Whether tidal or otherwise.

(f) Probability and extent of floods.

290.— Fords. A stream with a moderate current may be
forded by infantry when its depth does not exceed 3 ft., and by
cavalry and carriages when its depth is about 4 ft. The requi-
sites of a good ford are:—

(a) Banks low, but not marshy.

(b) Water attaining its depth gradually.

(d) Stream not subject to freshets.

(e) Bottom even, hard, and tenacious.

291.— In a mountainous country, the bed of a stream is likely
to be covered with large stones, rendering the passage of car-
riages impracticable. In level countries, the bed of the stream
may be composed of mud or quicksand, rendering passage by
fording impossible. In some cases, the bottom is composed of
fine sand, which is hard enough, but which, by the action of the
hoofs of the animals, is stirred up; the current then carries the
sand away and the ford is deepened, perhaps so much as to be-
come unfordable. The best bottom is coarse gravel.

292.— Fords are usually found in the wider and more rapid
parts of a stream. A straight reach gives the most uniform
depth. At bends, the depth will generally be greater at the con-
cave bank and less at the convex. (PI. 41, Figs. 1 and 3.)

PLATE 41.

Floating Bridges. 170

293.— To determine the position of a ford:—

(1) A number of mounted men may be sent across wherever
there is a probability of the river being shallow enough.

(2) Most certain method. Float down the stream in a boat,
keeping in the swiftest part of the current, where the water is
usually deepest. Hang a sounding line of the proper length over
the stern. When this touches bottom, sound across the stream.

When a ford is discovered, it should be marked by stakes; re-
markable objects on the shore should be noted; and a stake
planted at the water's edge and marked, in order that any rise
in the water may be at once evident.

294.— A stream, otherwise unfordable, may be passed:—

(1) By crossing it. in a slanting direction. (Fig. 2.)

(2) When the unfordable portion is not over 8 or 10 yards, this
may be filled in with fascines loaded with stones. (Fig. 4.)

(3) When the bottom is muddy, it may be covered with bun-
dles of coarse grass, rushes, or twigs, sunk by means of stones.

(4) A portion of the water may be diverted from its natural
channel. (Fig. 5.)

295.— In passing a stream by fording, if it is deep and the cur-
rent at all swift, the following precautions should be taken:—

(a) Troops passing in column should do so at a considerable
interval, in order to avoid choking the stream.

(h) If boats are to be had, a few should be stationed below the
ford, to assist men who may be carried down by the current.

(d) In place of provisions "b" and "c," a life line, held up by
casks, may be stretched across the stream.

(e) In order to break the force of the current, cavalry may be
stationed in the stream, above the point of crossing.

296.— After a freshet, a ford should always be reexamined,
lest some alteration may have taken place in the bed of the
stream. The banks of a stream to be forded should, if necessary,
be cut down.

The velocity of a stream may be determined by throwing in a
light rod, so weighted as to stand vertically. Note the distance
passed over in a certain number of seconds; then, 7-10 the mean
number of feet per second gives the velocity in miles per hour.

180 Floating Bridges.

297.— Ice. In high latitudes, during the winter, rivers axe fre-
quently covered with ice of sufficient thicliness to sustain the
heaviest loads. This means of passing a stream should be used
with great circumspection. A change of temperature may not
only suddenly destroy the natural bridge, but render the river
impassable by any method, for a considerable time, in conse-
quence of floating ice.

298.— Ice, in order to allow of passage, should be of the follow-
ing thickness:—
For Infantry, single file, 2 yds. distance, on a line of

planks 2 in.

For Cavalry or light guns, with intervals 4 in.

Heavy field-pieces ., , 5 to 7 in.

Heaviest loads 10 in.

299.— When there is any doubt as to the strength of the ice,
two tracks of plank may be laid for the carriage wheels to ran
on, or the wagon may be transformed into a kind of sled by fas-
tening two planks under the wheels. (Fig. 6.)

The thickness of ice may be increased, when the temperature
is low, by throwing water on it. When a stream is frozen on each
side but open in the middle, in consequence of the. velocity of the
current, a boom stretched across the open space will often check
the velocity sufficiently to allow the water to freeze.

300.— If a stream cannot be forded, it may be crossed by fer-
rying or by constructing a bridge. Ferrying may be by boat,
raft, or flying bridge; rowed, sheered, or hauled across.

301.— Ferrying by Boat. All boats available should be
collected and taken to the chosen point of passage. The banks of
the stream, if steep, should be cut down to facilitate embarkation.
The landing* should be farther down the stream than the point
of starting. The boats should be arranged along the shore and
numbered. Entrance to the boats should be by file, the soldiers
taking positions on opposite sides alternately. Where the water
is shallow near the shore, the boat should not approach the bank
so closely as to ground as the men file in. The unloading should
be made in the same manner as the embarkation—^, e., by file
alternately from each side of the boat. During the transit, the
men should remain in position and not rise up suddenly when the
boat lurches.

Floating Bridges. 181

In passing artillery, the piece sliould be dismounted. Horses
should, ordinarily, be made to swim. However, if the boats are
large enough, the bottoms may be covered with plank, and the
horses placed crosswise, facing alternately up and down stream.

302.— Ferrying by Baft. Rafts may be made of logs, lum-
ber, casks, and other material suitable for the purpose. Their
construction is the same as explained for piers of bridges, hence
only two expedients will be mentioned here.

303.— The Canvas Baft. No other material being available,
small rafts can be constructed by the use of canvas about 8 x
12 ft., and brushwood. Wet the canvas to make it water-proof,
and lay it out on the ground. Across the width place sticks in
layers, the longest near the middle. The sides should be strength-
ened by heavy sticks placed lengthwise. The pile of sticks
should be about 4 ft. wide in the center and sloping off slightly
towards the ends, 3 ft. high and 8 ft. long. Over this pile a sec-
ond piece of canvas, after being wet, should be placed. The
sides of the canvas on the ground are now drawn over toward
each other and lashed securely with a lariat. The ends are folded
neatly, brought up towards each other, and lashed. If care is
taken to wet the canvas thoroughly and make it water-tight, this
raft will carry three troopers with their arms and accouterments.
By lashing several together, a larger number of men, with their
arms and accouterments, can be carried.

304.— Bafts of Skins. Bags, made of the skins of animals,
inflated with air or stuffed with hay or straw, can be utilized for
crossing streams, and have been used from ancient times.

305.~Rafts are more suitable for the embarkation and landing
of troops of all arms than boats.. They will carry a larger nura-
•ber each trip, are not so easily injured by the fire of the enemy,
and draw little water. On the other hand, they cannot be navi-
gated with the same facility as boats, move much more slowly,
and hence keep the troops much longer under fire; cannot be
directed with certainty on a fixed point when the stream is rapid,
and, if the passage is to be effected secretly, the time required for
their construction is too long to admit of their use.

306.— The Floating Bridge. This may be formed of two
boats covered with a platform, constructed as follows:— (PI. 42,
Pig. 1.— The lashings and side rails are omitted.) From 5 to 7

182 Floating Bridges.

beams of the same thickness are laid across tlie two boats, the
intervals between the beams being equal, and such that the cover-
ing planks extend 1 ft. beyond the extreme beams. The interval
between the boats is such as to allow the beams to extend 2 ft.
beyond tlie gunwales. The beams are lashed to the boats, the
covering planks are kept in place by 2 side rails, laid directly over
the outer beams, and lashed down to them; the extreme planks
should be nailed down.

The floating bridge can be navigated by oars with nearly the
same facility as a boat.

307.— The Bope Ferry. The rope ferry, which is used in slug-
gish streams, consists of a floating support, either a raft, float-
ing bridge, or a large boat. It is drawn by hand along a rope
stretched from shore to shore.

308.— The Trail Bridge. This is employed in streams not
more than 150 yds. in width, and whose current is not less than 3
ft. per second, or 2 1-10 miles per hour. The rope must be main-
tained above the surface of the water, and, consequently, must be
drawn very tightly by means of a windlass, blocks, and falls, or
similar expedients; it must, also, at each bank, be raised some dis-
tance above the water. (PI. 42, Fig. 3.)

The raft, or boat, is attached to a pulley, which runs on a sheer
line, and by means of a rudder is given such a position that its
side makes an angle of about 55° with the direction of the cur-
rent. The angle of 55° with the current divides its force against
the side of the boat into two components: one, perpendicular to
the sheer line, which is counteracted T)y the resistance of this
line; the other, parallel to it, which moves the boat. A boat for
this kind of ferry should be narrow and deep, with nearly ver-
tical sides.

If a raft is used, it should be lozenge-shaped, the acute angle
being about 55°. When two sides are parallel to the current, the
up-stream side will then be in the most favorable position for
passage. (PI. 43, Fig. 8.)

309.— The Flying Bridge. The character of the float for
this ferry is the same as in the preceding case. (PI. 41, Fig. 7;
PI. 42, Fig. 2.) This bridge is resorted to when the stream Is
wider than 150 yds. The strain on the sheer line being very
great. It is replaced by a cable anchored In mid-stream, in which

PLATE 42.

Pig.l.

Fig.2.

PLATE 43.

Fig.l.

Fig. 2.

Fig.3.

Fig. 4.

Fig. 5

Fig.6.

Fig.8.

Fig.7.

Floating Bridges. 187

case the float would swing between two landing piers; or by two
cables, one anchored on either bank, the float swinging between
four piers. The latter requires less skill in manipulation. The
angle which the float makes with the current is the same as that
of the "trail" bridge. A sharp bend may be utilized for anchor-
ing the cable, as shown in PL 42, Fig. 4.

The length of a swinging cable should be ll^ to 2 times the
width of the stream. The cable should be supported on inter-
mediate buoys or floats, to prevent it dragging in the water.

310.— Floating Bridges are composed of a roadway and its
supports. The roadway is explained in the preceding chapter.
The supports are floating, as pontons, boats of commerce, rafts
of barrels, logs, lumber, inflated skins of animals, or other mate-
rial. The supports are called floating piers. It is from the char-
acter of the support that the bridge derives its name.

311.— In constructing a floating bridge, the site should be flrst
selected and the width of the stream measured.

In selecting a site, the following points should be noted:—

(a) Proximity to a road. As the approaches to floating
bridges, having frequently to be constructed across meadows, give
much trouble, they should be as short as possible. For a similar
reason, marshy banks are undesirable.

(h) The bed of the stream, if anchors are required, should
afford good holding ground.

(d) Use can frequently be made of islands to economize
material.

312.— In measuring the toidth of the stream, if it cannot be
done directly, some one of the methods explained in Chap. III.
can be used.

313.— It should be remembered that a wide roadway gives
greater steadiness than a narrow one. In making calculations
for buoyancy, the weight of a 9 ft. roadway may be taken at 80
lbs. per running foot.

314.— Piers. Of whatever material the floating pier is made,
the following points should be observed:—

(1) The available buoyancy of each pier should be sufficient to

188 Floating Bridgets.

support the heaviest load that can be brought on one bay of the
bridge.

(2) Piers should be connected with each other, at their extremi-
ties, by tie ballis or lashings.

(3) To insure steadiness, the length of a pier should be at least
twice the width of the roadway.

(4) The water way between piers should, if possible, be more
than the width of the piers, never less.

315.— Piers of open boats. In forming a pier of open boats,
the following precautions should be taken:—

(1) The boat should not be immersed deeper than within 1 ft.
of the gunwale.

^2) If the water is rough, or the current extremely swift, a
boat should not be immersed deeper than within 1 ft. 4 in. of the
gunwale.

(3) Boats should be placed in bridge with bows up stream or
toward the current.

(4) If the stream is tidal, the bows of the boats should be alter-
nately up and down stream.

(5) Unless the boat is very heavy and strong, the balks should
not rest on the gunwales; a central transom should be impro-
vised by resting a timber on the thwarts, or seats, blocking up
from underneath and bringing the weight directly on the keel-
son. (PI. 43, Figs. 6 and 7.)

(0) linrge boats should be placed where the current is swiftest,
also as the first and last boats in bridge.

316.— The buoyancy of a boat may be found by one of the
following rules:—

(1) To find the available buoyancy load the boat with unarmed
men to a safe depth. Multiply the number of men thus loaded by
160. The result will be the available buoyancy in pounds.

(2) If the boat is afloat and empty, the available buoyancy may
be found by calculating the volume between the then water line
and the "safe load" line, and multiplying by 02^^.

(3) To find the total buoyancy. If the boat is of nearly uni-
form section, the area of the section multiplied by the length of
the boat will give the cubic contents. A cubic foot of water
weighs 62% pounds.

Hence, if the dimensions of a boat are taken in feet, the con-

Floating Bridges.

189

tents will be cubic feet, and this, multiplied by 62^, will give the
displacement' of the boat; from this subtract the weight of the
boat; this will give the total buoyancy.

317.— To find the length of a bay. First find the avail-
able buoyancy of the boat. Then find the weight per running
foot of the load the bridge is to bear, and to this add the weight
per running foot of the roadway. Divide the available buoyancy
by this sum. The quotient will be the distance from center to
center that boats should be placed apart. Thus:— Suppose the
weight per running foot is 480 lbs., that the roadway is 80 lbs.
per running foot. .*. 480f80=560. The available buoyancy is
found by one of the preceding rules to be 5,600 lbs. .*. 5,600 h-
560=10.

318.— The open boats may be:— (1) Those of commerce usually
found on streams. (2) Regularly constructed pontons. (3) Im-
provised boats.

The first class requires no description. The second class com-
prises the canvas ponton used in the Advance Guard Train, and
the boat or barge used in the Reserve Train, of the U. S.

319.— The table below gives the dimensions of the ponton in
the U. S. Advance Guard Train, shown in PI. 47.

Canvas Ponton 21' x 5' 4" x 2' 4". Weight, 510 lbs.

Balks 22' x 4^^" x 4W.

Side Rails same as Balks.

Chess 11' X 12" X IVa".

WEIGHTS FOR ADVANCR GUARD TRAIN.

Ponton

Chess

Trestle

Tool

Forge

320.— The table below gives the dimensions of the ponton in
the U. S. Reserve Train, shown in PI. 48.

Ponton 31' x 5' 8" x 2' 7". Weight, 1,600 lbs.
Balks 27' x 5" x 5" for a 20' span.
Trestle Balks 21' 8" x 5" x 5".

Wagon.

Load.

Total

lbs.

1,750

1,985

3,735

1,750

1,856

3,606

1,750

2,060

3,810

1,700

1,938

3,638

1,217

1,166

2,381

190

Floating Bridges.

Chess 13' X 12" x ly^".
Side Rails same as Balks.

WEIGHTS FOR RESERVE TRAIN.

Wagon.

l.oad.

Total

Ponton

lbs.
2,200
1,750
2,200
1,700
2,217

lbs.
2,900
2,280
2,635
2,100
1,166

lbs.
5,100

Chess . .•

4,030
4,835

Trestle

Tool

3,800

Forge . ■

3,383

321.— Improvised Boats. To reduce the amount of transpor-
tation required by an army is a very important consideration;
hence the value of the following expedients.

322.— The Crib Ponton. This boat is 18 ft. long, 5 ft. wide,
2^ ft. deep and covered with canvas. Construction. (1) Let
stakes 4 ft. long, 2^ in. in diameter, and 2 ft. apart, be driven into
the ground (PI. 44, Figs. 1, 2 and 3), to the depth of about 1 ft., so
as to enclose a space of the proper size for the top of the boat.
The tops of the stakes should be in the same horizontal plane.
This may be tested by placing a straight-edge on them. Those
that are too high can then be driven down.

(2) Nail boards against the outside of the stakes, extending
4 in. over their tops.

(3) Cross-pieces, of the same diameter as the stakes, are laid
across the tops and pinned down upon them with wooden pins.

(4) Nail the sidie boards to the ends of the cross-pieces, and
cover the bottom of the boat, which in its inverted position is
now on top, with boards, and nail the projecting edges of the
side boards to the bottom securely.

(5) Finish boarding sides and ends to. the proper depth.

(6) The frame is now ready to be covered with canvas. For a
boat of the foregoing dimensions, the canvas should be 23^ ft. x
10^> ft., about 6 in. being allowed for lap. The canvas may be put
together in any number of pieces by daubing the edges of the
seams with a water-proof composition and connecting them with
ordinary carpet tacks.

(7) The canvas having been prepared, it should now be coated
with a water-proof composition. Tallow, put on hot, will do if
nothing better can be found.

PLATE 44.

Fig.l.

Fig.6.

Fig. 2

4 . UJJLi& *M»»M4

-13-

Floating Bridges. 19»'^

(8) Place the canvas on the frame, coated side downward. Tack
the canvas to the frame and cover with water-proof composition.

(9) Spike or pin 2 or 3 stout poles to the bottom longitudinally
(not shown in drawing) to keep the bottom from abrading. If
these poles are allowed to project about 6 in. at each end, they
will assist in launching.

(10) Loosen the stakes from the ground by means of levers.
Turn the boat over and saw off the stakes about 2 in. below the
top edge of the side and end boards.

(11) Pin stout poles to the top of the stakes on the sides and
ends, and nail the side and end boards securely to them.

(12) The side poles should project about 6 in. beyond the ends
corresponding to those on the bottom, and be lashed to the bot-
tom poles by means of a rope loop and rack stick. (Not shown in
drawing.)

(13) Turn the canvas over the top poles and tack it down. The
boat is finished.

328.— The Box Ponton. In localities where planks and boards
can be conveniently procured, pontons may be constructed very
expeditiously by placing two partitions of 2 in plank, each 5 ft.
long and 2^/^ ft. high, in parallel positions, on the top and ends of
which boards are nailed. (PI. 44, Fig. 4.) The box thus formed
to be covered with pitched canvas, as described in the mode of
constructing crib pontons. Where sound lumber is at hand, the
box ponton will be more easily and expeditiously constructed
than the crib ponton, but if plank is not at hand it may be prefer-
able to use poles or split timber ratlier than wait for it.

324.— Wagon Body Ponton. Ordinary wagon bodies, cov-
ered with water-proof canvas or India rubber blankets, may be
used either as boats or pontons. The small capacity of the
wagon body requires such pontons to be placed more closely, to
compensate for it. ,

325.— Piers of Casks. In order to determine the number of
casks necessary to form a pier, the buoyancy of a cask must be
calculated. This may be done by one of the following rules:—

(1) Find the contents of the cask in gallons and multiply this
hr R 1-3: the result will be almost the total buoj^ancy in pounds.

(2) By the formula

5cM — W = x

194 Floating Bridges.

In which c is the circumference of the cask in feet half way be-
tween the bung and the extreme end; 1 is the length in feet, ex-
clusive of projections, measured along a stave, and W Is the
weight of the cask in pounds; x being the total buoyancy.

If the cask is closed, 9-10 of the total buoyancy equals the avaiU
able buoyancy.

326.~To find the distance between two piers of casks: Find
the available buoyancy of each cask. Multiply this by the num-
ber of casks in the pier. This gives the available buoyancy of the
pier. To the weight per running foot that the bridge is to bear
add the weight per running foot of the superstructure. Divide
the available buoyancy of the pier by this sum; the quotient will
be the required distance.

327.— In regard to piers of oaskSf the following should be
noted:

(1) That piers of casks, when in bridge, should always be rig-
idly connected to each other at their ends by tie balks.

(2) That the tie balks should be lashed to both gunnels of each
pier.

(3) That while the roadway balks may not be lashed to the
gunnels and to each other, it should be done if there is much
sway on the bridge.

328.— Piers of Open Casks. This is the simplest and most
convenient method of using casks for piers, as it requires only
a few nails and poles, dispensing with ropes, which are sometimes «
hard to procure.

To make a raft of this kind, as shown in PI. 44, Figs. 5 and 6.
stand 10 or 12 barrels side by side, touching each other; nail 4
poles across the outside of the barrels, two at top, two at bottom,
the nails being driven from the inside into the poles, which, as
the heads are out, can easily be done. Place another row of bar-
rels beside the row thus fastened together and nail them to the
two poles of this row. Nail two poles to the outside of the second
row of barrels, one at top and one at bottom; push the barrels
thus connected into the water.

If too many rows are connected on land they will become too
heavy to handle. Any number of rows, however, can be attached
in the manner described above. When the raft Is completed, the
projecting ends of the poles outside are lashed together, and, at

Floating BridgeB. 196

the points of contact of the barrels, a stout wh*e nail should be
driven through and clinched.

329.— The total buoyancy of a cask may be calculated by the
formula given above. If this should be 400 lbs., the safe load for
smooth water would be at least 300 lbs.; that is, the available
buoyancy is about % the total buoyancy. A square raft of 10
such barrels to a side would carry safely 30,000 lbs.

330.— Piers of Closed Casks. The usual method of forming
large casks into a pier is shown in PI. 43, Figs. 1 and 2. The fol-
lowing are the successive steps in its construction:—

Btores required for a pier of 7 casks: 7 casks; 2 gunnels; 2
slings; 12 braces.

To build a pier of the foregoing stores, 1 N. C. O. and 16 men
will be required. The detachment is marched to the site on
which the material is placed and forms the casks into piers by the
following commands and means, 4 men being detailed as gunnel-
men and 12 as bracemen.

(1) Align casks. At this command, the casks are brought to
the designated place by the bracemen and aligned, touching each
other, bung uppermost.

(2) Place gunnels. At this command, the gunnels are placed
on the outer ends of the casks by the gunnelmen.

(3) Adjust slings. At this command, gunnelmen bring up
the slings and stand at the ends of the gunnels, the bracemen be-
ing opposite the intervals between the casks. The gunnelmen at
one end place the eyes of the slings over the ends of the gunnels,
and those at the other end secure the slings to the ends of the
gunnels by a round turn and two half-hitches. The bracemen
keep the slings under the ends of the casks with their feet. A
sling is made of 1 In. rope and of sufficient length for an eye splice
1 ft. long, at one end.

(4) Fasten braces. At this command, the bracemen, haying
provided themselves with braces, pass the eye of the brace under
the sling in the center of their interval the end passed through
the eye and the brace hauled taut, the sling being steadied by
either foot. The brace is then brought up outside the gunnel,
directly over the eye, and a turn round the gunnel taken to the
left of the standing part.

(5) Haul taut. At this command, each braceman removes

196 Floating Bridges.

his foot from the sling and hauls up the standing part of his
brace with his right hand, holding on to the turn with his left;
as soon as the brace is taut, the turn is held with the left hand
and the remainder of the brace in a coil is placed on the cask to
the left.

(0) Cross braces. At this command, each braceman takes the
brace of the man opposite him from the cask on his right, pass-
ing it between the standing part of his brace and the cask on
his left, then back between his brace and the cask on his right,
keeping the turn below the figure of eight knot on his own brace.
The end is then placed on the cask on his right. Each man then
takes back his own brace from the cask on his left, passes it under
the gunnel to the left of the standing part, places one foot against
the gunnel and hauls taut.

(7) Rock and haul taut. The bracemen, assisted by the gun-
nelmen, at this command, rock the pier backwards and forwards,
the bracemen taking in the slack of their braces.

(8) Steady. At this command, the bracemen cease hauling
taut and take a turn round the gunnel to the left of the previous
turns.

(9) Secure braces. At this command, the braces are made fast
by two half-hitches round the two parts of their own braces, close
to the gunnels, drawing the two parts close together and placing
the spare ends of the braces between the casks.

(10) Turn the pier to the right and adjust sling. At this
command, the bracemen on the left side, assisted by the gunnel-
men, turn the pier on its right side. The bracemen on the left
side adjust the left slin^.

(11) Lower the pier, turn to the left, and adjust sling.
At this command, the bracemen on the left, assisted by the
gunnelmen, lower the pier. The bracemen on the right, assist-
ed by the gunnelmen, then turn the pier to the left. The
bracemen on the right then adjust the right sling. The pier is
complete.

331.— Should the casks be very small, they may be put together
as above described, forming small piers. These can then be
united in one large pier by cross gunnels.

332.- -Another method of forming casks into a pier is as fol-
lows:— (Figs. 3 and 4.)

Floating Bridges. 197

Fasten the braces to a balk, two braces for each cask. Stretch
out the braces perpendicular to the balk and lay the casks bung
uppermost, end to end, on each side of the balk, each cask over
its own braces. Upon the cask lay two gunnels, fastened together
at the ends and one or two intermediate points by lashings, the
distance between the gunnels being less than a bung diameter of
a cask. Secure the braces to the gunnels by two round turns and
two half-hitches. The lashings connecting the gunnels are then
racked up. The two end gunnel lashings are lashed to the balk
beneath the casks and these lashings are racked up taut. The
pier is then complete.

338.— The barrels may be held in a frame, as shown in PI. 44,
Figs. 7 and 8.

384.— Piers of Logs. In order to determine the number
of logs necessary to form a pier, the buoyancy of a log must be
calculated.

To find the total buoyancy of a log. Multiply the solid con-
tents of a log by the difference between the weight of a cubic foot
of the log and a cubic foot of water.

335.— To find the solid contents of a log.

(1) Take a mean of the girths or circumference at the ends in
feet and decimals. Square this mean and multiply it by the dec-
imal .07956. Multiply this product by the length of the log in
feet.

(2) Multiply the square of 1-5 of the mean girth by twice the
length of the trunk.

336.— The weight per cubic foot of the timbers usually met
with will be found in Chap. XV.

337.— Required the total buoyancy of a pine log whose mean
girth is 6 ft. and whose length is 35 ft.

Applying rule 2, we have

^XfX35X2 = 1001 cu. ft.

loot ^ (62% — 40) = 100 f X 22% = 100.8 X 22.5 = 2,268 lbs.
. As lumber absorbs water, the available buoyancy is taken as 5-6
the total buoyancy.

338.— To form a pier of logs. (PI. 43, Fig. 5.) The larg-
est and longest logs should be selected. Branches and knots
should be trimmed off. The ends of the logs should be painted if
the raft is to be used any length of time. The raft should be

198 Floating BridgeB.

built in the water. Select a place where there is little cUrreiit
and where the bank slopes gently to the stream. Throw the tim-
ber into the water and moor it, close to the shore. Note the nat-
ural position of each log in the water before putting it in the raft
The up-stream end of each log (Should be drawn on shore and bev-
eled to a whistle shape, so as to present less obstruction to the
action of the current.

Arrange the timber in the position it is to have in the raft, the
butts alternately up and down stream, the up-stream ends forming
a right angle, salient up stream. The first log is brought along-
side the shore and the end of a plank or a small trunk of a tree
fastened with trenails or spikes to it about 3 ft. from each end.
The log is then pushed off a little, a second log brought up under
the transoms and in close contact with the first. The second log
is then spiked like the first, and so on for each remaining log.
Care must be taken to place the whistle ends up stream with the
bevel underneath, and to spike the transoms perpendicular to the
logs, If the stream is very gentle, the up-stream ends of the logs
may be parallel to the transoms.

Another method is to lash the logs together and fasten on the
transoms with spikes or trenails. Or, lash the logs together and
lash the transoms to the logs, tightening the lashings with rack
sticks.

339.— Two. additional transoms should be placed on the raft
by whatever method employed in putting on the first. They
should be the distance of the roadway or platform apart, at equal
distances from the center of gravity of the raft, and bear upon all
the logs. In order to obtain sufficient buoyancy, and allow suf-
ficient water way, several courses of timber may have to be em-
ployed. For use in a bridge, a raft should have an available
buoyancy of 15,000 lbs.

340.— If the raft is to be used as a flying hridge^ it should have
the shape of a lozenge. (PI. 43, Fig. 8.)

341.— Anchors. Anchors for the U. S. Advance Guard Bridge
Train weigh 75 lbs., and for the Reserve Train 150 lbs. These-
will be sufficient for moderate streams. An anchor with the
names of the various parts Is shown in PI. 45, Fig. 1.

342.— The distance of the anchor from the bridge should be
at least 10 times the depth of the stream; otherwise the bow of

PLATE 45.

pLm4t

nilllA • n

Flg.2;.

Pig.3.

Tiit.

PLATE 47.

PLATE 48

Floating Bridges. 207

the boat or ponton will sink too deep in the water. The direction
of the cable must be the same as the current. The anchor cable
should be of 1 in. rope and attached to the anchor ring by a fish-
erman's bend. A buoy might be attached to the anchor by means
of a ^-in. breast line, in order to mark its position and serve as
a means of raising it. The breast line is attached to the buoy
ring by a fisherman's bend and round the shank of the anchor,
close to the crown, by a- clove hitch.

343.— The number of anchors will depend on the strength of
the current. It is generally sufficient to cast an anchor up-stream
for every alternate boat or ponton, and half that number down-
stream. If the stream is rapid, every boat should be anchored
up-stream.

If very rapidj the bridge must be secured to a hawser, as shown
in PI. 46, Fig. 1, If the bridge is short, ropes can be stretched
from the piers to the banks. (Fig. 2.) If anchors are scarce, one
may be attached to two piers. (Fig. 3.)

Before being cast, the anchor should be well stocked. Rafts
of casks or timbers bring a greater strain on anchors than boats
or pontons.

344.— Substitutes for Anchors. One or two spare wheels
with tires and felloes removed. (PI. 45, Figs. 3 and 4.) Two or
more pick-axes, laid together or fixed on one handle. (PI. 46, Fig.
4.) A harrow with lengthened teeth, loaded with stones. Ga-
bions filled with stones. Large stones or railway irons. Nets
filled with stones. Frame filled with stones. (PI. 45, Fig. 2.)

Care must be taken to allow the anchor to fall in good holding
ground. P^'or this purpose, a direction oblique to the current may
sometimes be allowed.

345.— Forming Floating Bridges. Floating bridges may
be formed in the following ways:—

(1) By successive pontons or boats.

(2) By parts.

(3) By rafts.

(4) By conversion.

346.— By Successive Pontons. (PI. 49.) This may be done
in two ways:—

(1) By adding to the head of the bridge, the tail being station-
ary. This method requires the roadway material to be carried an
-14-

208 Floating Bridges.

increasing distance. The men, however, do not have to work in
the water.

(2) By adding to the tail of the bridge, the head, already con-
structed, being constantly pushed into the stream. The materials
do not have to be carried so far as in the first case, but it requires
a number of men to worli in the water and is not advantageous
where the bank is steep.

In the first method, tliose boats or pontons which cast up-
stream anchors should be moored above the approach to tlie
bridge, the others below.

347.— By Parts. (PI. 49.) In this method, the boats or pon-
tons are brouglit close to the shore above the bridge. For con-
venience in putting the parts together several chess are laid from
the bank to tlie interior gunwale of one boat or ponton. The
boats or pontons forming the part are then brought in place and
balks placed on them. The chess forming the roadway are then
placed on the balks, excepting a sufficient number at each end of
the part to allow for the insertion of a bay between the parts.
The parts, all constructed as directed, are then placed in position,
each part carrying enough material to construct the connecting
bay. The parts are joined with each other and with the abut-
ment bay, which has been previously constructed.

348.— By Bafts. Each raft formed of 2 or more piers is con-
structed complete and the rafts come into the bridge in succes-
sion. PZach of the methods, bridge by raft and bridge by parts,
has the advantage of simultaneouslj^ employing a large number
of men. (PI. 49.)

349.— By Conversion. (PI. 49.) In this method, the bridge
is put together entire along the shore above the selected site. A
tributary stream may be advantageous for this purpose. The
bridge is then floated toward the site, care being taken to prevent
the pivot end from touching the shore and the wheeling end from
turning too fast.

350.— The various methods above described may be combined
in the construction of one bridge.

The connection of the bridge with the shore may be made by
allowing the balks to rest on an abutment sill let about 1 ft. into
the ground, or by a trestle.

PLATE ~49.

Floating Bridges. 211

351.— If the stream is to remain oi)en to traffic, it is well to
have two or more rafts in mid-stream, arranged to swing so as to
allow boats to pass, or the halves of the bridge may be swung for
this purpose. Usually the passage is made by allowing the rafts
or halves to swing with the current; they are then brought back
against the current.

352.— Floating Objects. Some arrangement should be made
to protect the bridge from floating objects. This may be done:—

(1) By a guard of observation, stationed above the bridge, pro-
vided with boats containing anchors, grapnels, hammers, t;hains,
etc. The object may be turned ashore, or, if this is not possible,
an anchor may be attached to it to break its momentum.

(2) By a floating stockade, constructed of trees united by
chains and forming a continuous barrier to floating objects. Its
direction should be about 20** with the current.

(3) By constructing the bridge by rafts and withdrawing the
menaced part, thus allowing the object to float past.

CHAPTEB XVII.--Boads.

353.— The frequent necessity, in the tield, for the construction
of a'short i>iece.of road, or the repairing of existing roads, makes
it important tliat all who may at any time have tliis work in
charge should l>e familiar with the principal reciuirements of it.

354.- Two desirable conditions in a road are that it be straight
and level; where both cannot be obtained, straightness is sajcri-
ficed ta levelness. Other things being equal, the length of a road
may often be advantageously increased 20 ft. for every foot of
vertical height avoided.

355.— Limiting Gradient. As levelness cannot always be ob-
tained, various considerations fix limits for the steepness, called
limiting gradients, which are to be used only when unavoidable:
thus, lor a very short distance, as an ai)proach to a bridge, the lim-
iting gradient may be 1-10; a grade of 1-12 should not exceed 100
ft.; one of 1-15 should not exceed 2(X) ft.; 1-20 should ordinarily be
the limiting gradient for easy travel, while 1-30 to 1-35 is still
better.

356.— Compared to what he can draw on a level, a horse can
draw only al)out 00 per cent on a grade of I-lOO, 80 per cent on
1-50, r>0 per cent on 1-24, and 25 per cent on 1-10. but for a short
distance lie can exert times his ordinary force.

357.— A road should, if i)ossible, always rise continuously to
Ks higliost ]K)int ami nowliere descend partially again.

358. -Width. For military purposes roads should be wide
eiiougli to allow wagons going in oi)]>osite directions to pass each
otlier easily; this is usually taken at 10 ft. For wagons going in
one direction only or with turnouts at intervals, and for infant-
!•>' in (!olumn of fours, or cavalry in column of twos, 9 ft. will suf-
tic<», and for padv animals ft. At turns in a zig-zag road up a
liill the road should be level and the width increased from ^ to %.

359.- Form. Tlie best for the upper surface is that of two
I)lanes inclined at an angle of about 1-24 and joined by a slight
curve 5 ft. long. (PI. 50. Figs. 1, 2 and 13.)

Between tlie road and ditches should be flat mounds raised
in. or more above tlie surface, with sloping sides covered with
sods or stone next to road, forming with roadway the gutters;

PLATE 50.

-^S-'^FIQ2 "^*'°'*«»

Roads. 215

they serve also to hold up the road material arid as warnings at
night of the proximity of the ditch.

On the hillside the surface should be a single plane inclined
towards the hill. (Figs. S, 4, 5, 7 and 8.)

360.— Boad-bed. The surface of the road-bed should be dug
out or built up and solidly compacted, either by rolling or ram-
ming, and when ready to receive the road material should be of
the same shape as the surface of the finished road, with shoulders
at the sides to retain the material in place. (Fig. 13.)

On hillsides of gentle slope, the road-l)ed is usually made of
half cutting and half filling, the lower side of the slope being
stepped to retain the earth excavated (Fig. 3); on steep slopes it
Is often necessary to both step the slope and build a retaining
wall of stone (Fig. 4), or of logs (Fig. 5), or of other materials; on
very steep slopes it may be necessary to build retaining walls on
both sides (Fig. 7); while in rocky formations the excavated hill-
side may be left nearly vertical. (Fig. 8.)

361.— Drainage. Nothing is of greater importance in road-
building than proper drainage. It is the life of a road. In a
level country it is necessary to raise the road-bed to keep it
always free from water. None must be allowed to remain on the
surface and all must be drained from beneath. To accomplish
this ditches must be dug on. both sides of a road on level ground
and in cuttings, from 2 to 3 ft. below the road-bed and of a width
depending on the amount of water to be discharged. (Figs. 1
and 2.) In wet places, low-lying lands, clayey and springy soils,
the ditches must be deeper and sub-drains 3 to 5 ft. below the
road, emptying at Intervals into the side ditches, must be made to
keep it dry. (Fig. 1.)

Rain falling on the surface of the road is collected in the gut-
ters on the sides and run into the side ditches by drains at fre-
quent intervals.

On a hillside, between the road and the hill is the ditch, from
which the water is discharged through culverts or covered drains
under the road into the natural watercourses. Catch drains
along the top of the cutting are made to prevent the slopes being
washed down and the water from above finding its way to the
road.

216 Roads.

Wh^re open ditciies are liable to become liUed, some kind of
covered drain must be used. (1 igs. 5, lU, 11 and 12.)

Tlieoretically, a road snouia be pertectly level, but for pur-
poses of drainage, in tlie direction of its length, it should have at
least a slope of 1-125.

On a steep road, shallow paved water tables extending oblique-
ly across the road are sometimes necessary to catch the water
running down the road and carry it to the gutters, or small
mounds crossing the road obliquely are substituted. (Fig. 9.)

362.— The surface of a road ought to be as smooth and as hard
as possible, for which purpose various liinds of covering material
are put on the bed.

As the road-bed must be Itept thoroughly dry at all times by
the ditches intercepting all ground water, so the stone or other
covering must be so thoroughly rolled and compacted that no
water falling upon the surface can possibly find its way down to
the foundation and through it to the bed.

363.— When roads are made of broken stone the material in
the Telford class is composed of two parts: the foundation and
the covering. (Fig. 1, right half.) The foundation consists of
a uniform thickness of not less than 5 in. of any durable broken
stone with bases about 5 in. x 10 in. laid close together by hand,
larger faces down, firmly wedged with smaller stones in the in-
terstices, and the whole sledged and rolled to a uniform sur-
face. Then a thin layer of binding material, as clay or loam, is
sprinkled over it and rolled. On this is put the covering, consist-
ing of a layer of about 3 in. of broken stone of uniform, well-
shape<l cul)ical pieces whicli will pass through a ring from 2 to
2M» in. in diameter, and rolled to a uniform, compact, surface.
Then another layer of binding material is added and w^ell rolled.
Another layer of stones, 3 in. thick, of sizes from 1 to 2 in. in diam-
eter, is next spread and rolled as before. On this may be spread
anotlier binding coat, well rolled, then a thin layer of fine screen-
ings or fine gravel free from dirt. Often, where trafl[ic is light
and expense large, a single layer of broken stone 4 in. tliick is put
on the foundation.

364.— In the Macadam class (Fig. 1, left half) the hand-laid
foundation is not used, but generally three layers, each from 3 to

Roads. 217

4 in. thick, of broken stone and binding coats, as described above,
are spread and rolled until smooth and compact.

For light traffic a single layer of 4 in. is sometimes used.

365.— The best stone is a compact, tine-grained syenite, basalt
or trap rock. Hornblend, actinolyte, dioryte, and some other
rocks make go<5d material. Quartz and tiint, though very hard,
are brittle, difficult to work, and not so good. Granite, on ac-
count of mica in it, breaks up and grinds away too easily. Gneiss
is poorer than granite. Slatey rocks generally break up too eas-
ily.. Limestone, generally too soft, grinds away easily, making a
very disagreeable dust. Softer stones may be used for the foun-
dations and lower layers, but only the hardest and toughest
should be used for the coverings.

366.— Earth roads requii-^e even greater care in draining, grad-
ing, and forming the surface than those described, and a trans-
verse slope, not less than 1-20, to hasten the flow of surface water
to the gutters. No sods or vegetable refuse should be allowed in
grading or filling ruts, but gravelly earth, if obtainable.

Roads are frequently made with a metal portion in the center
and earth roads, called wingSy on the sides. (Fig. 2.)

367.— It Is almost impossible to construct a road of clay which
will be good in wet weather, but a very sandy road may be im-
proved by working a little clay in it.

368.— For gravel roads the bed is first formed as described.
The gravel is screened to remove stones larger than 2^2 in. in
diameter and such as are less than % in.; and all earthy matter.
A layer of the screened gravel, 4 or 5 in. tliick, is then spread and
rolled, then another layer of 3 or 4 in., which should also be well
rolled.

369.— Repairs. Ruts appearing should be immediately filled
in, and traffic directed over all parts of road. Before spreading
stones, all mud should be cleaned off and the surface picked up a
little to allow the new stone to bind into the old, wet weather be-
ing preferred, or the stones should be sprinkled. Ditches and
culverts must be cleaned as needed.

370. —In crossing marshy ground that cannot be well drained,
logs of suitable lengths laid side by side across the road, over
which is spread a covering of earth or gravel, are sometimes used.

371.— Brushwood, made into fascines and hurdles, may be

218 Roads.

used the same way as a foundation. With fascines, the top row
should extend across the road and be of a length equal to the
width of road. (Fig. 6.)

372.— Where lumber is the cheapest material, plank roads ihay
be built by first laying parallel rows of sleepers or sills flush
with the ground, about 4 ft. apart, in the direction of the road, on
which boards, 3 in. thick by 9 to 12 in. wide and 8 ft. long, are
placed crosswise.

373.— The construction of communications to all parts of a
position to facilitate the movement of troops, etc., from one part
to another, is almost always a certain necessity. These would
rarely be more than temporary, but, if made on the lines indi-
cated, as far as time and requirements permitted, so much the
better.

374.— Roads and paths may have to be cleared through woods;
wet places made passable by corduroying or filling up with brush,
fascines, etc.; and approaches made to ascend steep places.

Wherever roads cross or separate, signs should be put up tell-
ing exactly where each leads.

PLATE 51

FIG.l. .

FIG.2.

PcA-rm

a a a o a a

^ Ir

FIGS. //art/ind Besaed^eeirOa.

X5^ -.

eig:5:

Crossing

FIG.12.

^tM.

CHAPTEB XVIII.— Bailroads.

375.— In military operations, tiie principal duties of troops in
connection with railroads will be either the repairing of lines that
have been partially destroyed, or the destruction of lines to pre-
vent their use i)y the enemy.

376.— A railroad, as existing in its completed form, will be
briefly described to indicate the state to which it should be
brought by repairs after destruction, and to so familiarize one
with it as to suggest methods of most effectually destroying it.

377.— A railway line consists of a series of straight lines of
different lengths, called tangents, which are joined by curves.
The road-bed is first pi^pared with a smooth hard surface (slop-
ing slightly from the middle to each side for drainage) from 10 to
12 ft. wide for a single track, and from 21 to 25 ft. for a double
track. On this is placed the ballast, from 12 to 24 in. thick, of
broken stone, gravel or cinders, etc., for the purpose of distribut-
ing the load over a larger surface, holding the ties in place, carry-
ing off the rainwater, affording a means of keeping the ties up to
grade line and giving elasticity to the road-bed.

378.— The ties are generally of wood, hewn flat on top and
bottom, from 7.5 to 9 ft. long, G to 10 in. wide, and about 7 in.
deep. It is customar.y to sink them about half their depth into
the ballast. Their object is to hold the rails in place and furnish
an elastic medium 'between the rails and ground. The distance
apart is usually 2.5 ft. from center to center, but depends upon
weight of engines and strength of rails. They should be uni-
formly spaced to distribute the weight equally.

Tie plates (PI. 51, Figs. 3 and 7) are often used to prevent the
rails from crushing into the ties.

379.— Tests of metal ties in the interests of economy and eflft
ciency have been made with satisfactory results. On some level
portions of the N. Y. Central R. R. are used the Hartford pressed
steel tie (Pigs. 1 and 2), to which the rails are fastened by clamps
bolted to the tie.

380.— The form of rail used in the TT^nited States is shown in
Fig. 3, being the "T'* rail, which varies in weight from 12 to 100
lbs. per yard. The mean dimensions of 80 lb. rails are given on

222 Railroads.

left-hand side of figure and of 100 lb. rails on right-hand side.
They are placed 3 ft. apart for narrow gauge, 4 ft. 8.5 in. for
standard gauge, while 6 ft. is the broadest gauge in the United
States, measured from inside to inside of head. The tops of rails
must be slightly inclined to fit the cones of the wheels.

381.— The weak part of a track is at the joints. The old
method of using chairs under the ends of rails has about ceased,
the practice now being to fish the Joints by plates (Fig. 1), and
angle irons. (Fig. 3.) There are also used what are known as
the Reinforced rail joints (Fig. 4), Bridge rail joints (Fig. 8), Dou-
ble Girder rail joints. (Fig. 9.)

382.— Rails are fastened to the ties by spikes, the best being
made with sharp, chisel-edge points, clean, sharp edges, and
smooth surfaces, so as to cut and press aside the fibers of the
wood, instead of tearing them. Attempts to increase the hold-
ing power by jagged or twisted spikes have been unsuccessful.
On bridges, interlocking bolts (Fig. 6) are much used instead of
spikes. To keep the track in the right line, allowance must be
made for the contraction and expansion of the rails, by not plac-
ing them in contact at the joints, and the holes for the bolts must
be elongated.

383.— The centrifugal force of a train passing around a curve
tends to throw the wheels against the outer rails, which Is par-
tially counteracted by raising them to throw the center of gravity
inward and cause the car to slide inward. Each rail in a curve
ought to be bent to fit the curve before being laid.

384.— On single tracks, there are laid at occasional intervals
short pieces of track, called sidings, to enable trains to pass one
another. The arrangement for passing from one track to another
is the switch, which consists of a single length of rails, movable at
one end by a lever, so as to connect with either pair of rails. The
simplest form is the stub switch (Fig. 10), which leaves one line
always open while the other is continuous. The one in common
use is the split or point switch. (Fig. 11.) Various devices are
used for locking and interlocking switches, to avoid accidents.
At the points where the inner rails cross is placed a frog (PI. 52,
Fig. 1), which enables the wheels to pass over the inner rail of
the other track.

PLATE 52. .

-16-

Railroads. 225

385.— Crossings occur where two tracks intersect, and consist
of four frogs and corresponding guard rails. (PL 51, Fig. 12.)

386.— Where one main line passes to another is called a junc-
tion and the ordinary switch is used. In crossing from one track
to a parallel track the rails are arranged as in PI. 52, Fig. 2.

387.— A wye, from a similarity to the letter **Y," is an arrange-
ment of tracks for turning around engines and cars and connect-
ing cross-roads. (Fig. 3.)

388.— Turntables are platforms, turning on rollers upon an
underground circular track, used to transfer engines and cars
from one track to another and to turn them around.

389.— The locomotive engine is the power on railroads. They
weigh from. 58,000 lbs. to 190,000 lbs. without tender, and from
218,000 lbs. for passenger to 310,000 lbs. for freight, with tender,
all loaded, and draw 2,400 or more tons on a level. The amount
of coal consumed being from 40 lbs. to TO lbs. per mile run.

390.— The rolling stock consists of passenger cars for about 60
persons, 48 to 52 ft. long, 9.5 ft. wide, weighing from 40,000 lbs.
to 60,(XX) lbs.; sleeping cars for 64 passengers, 60 to 70 ft. long,
9.8 ft. wide, Weighing 60,000 lbs. to 90.000 lbs.; mail, express and
baggage cars, 45 ft. long, 9.3 ft. wide, weighing about 27,000 lbs. ;
freight cars consist of Box, Refrigerator, Hay, Furniture, Oil,
Stock, etc., and are about 34 ft. long, 8.5 ft. wide, weighing about
20,000 lbs., capacity 20 tons; flat cars, 34 ft. long, weigh 16,000 lbs.
to 19,0(X) lbs. Height of top of box cars above rails about 15 ft.
Freight cars are being rapidly provided with the M. C. B. auto-
matic couplers. (Fig. 4.)

391<— The buildings consist of passenger and freight depots,
engine houses, fuel sheds, water tanks, repair shops, and section
houses. At convenient points are generally located yards where
stock can be loaded and unloaded. It may sometimes be neces-
sary, however, to load and unload animals and supplies in the
field along a railroad where there are no platforms or other con-
veniences, which must then be built.

392.— A simple form of ramp, in the absence of anything
better, could be made by taking 3 or 4 planks 3 in. thick, 10 to 12
in. wide, and 10 to 14 ft. long, fastening them together side bv
side, preferably by footholds nailed across on top and several
cleats on the bottom; otherwise, by lashing, wiring or by stakes

226 Railroads.

at the bottom when in position, and weflges in the car door. The
ends on the ground should be slightly sunken and rested against
a cross beam. Ropes should be hung along the sides and blankets
or canvas hung on them. Props of some kind, as sacks of grain,
bales of hay, etc., can be placed under the middle to strengthen
it if necessary.

393. — Another fomL of portable ramp, which could be carried
on all railroad trains where they might be needed, consists of 6
long timbers 4 in. x 4 in. x 14 ft., 6 short timbers 4 in. x 4 in. x 6
ft., 24 boards 1.5 in. x 12 in. x 6 ft. with footholds nailed length-
wise on one side.

To load or unload horses, rest the ends of three of the long tim-
bers, equally spaced, on the car floor, the other ends resting
against a short timber, sunk in the ground and staked down. On
these place the boards forming the floor; on each side of the ranap,
on the boards, lay a long timl>er and fasten the ends to the timbers
underneath. The boards should have cleats on under side to
prevent slipping sideways. If necessary, some of the remaining
boards can be set edgewise between posts of the short timbers
as an intermediate support.

394. — To unload a number of ears, enough men can be placed un-
der the ramp, near the car, to raise it high enough to allow the car
to be removed and another run in place, thus avoiding taking
the ramp apart for each car.

S95.— Semi-permanent platforms and ramps may be made as in
Figs. 6 and 7, if rails and boards are available.

396.— To load or unload icagons and guns from a flat car, place
the ramp against one end (Fig. 8), using four long timbers for
stringers on which the boards are placed, the other two long tim-
bers being used for side rails. Support underneath with boards
set on edge, held between some short timbers, or with bales of
hay, sacks of grain or otherwise, as necessary. A couple of
boards can be used to run the wheels from the car on to the rnmn
and others at the foot of ramp to carry the wheels across the rails.
The lower ends of the stringers should abut against a tie, if pos-
sible: if rot, they should be staked down,

397.— PI. 53 Is a design of a portable ramp devised by Major
F. O. Fechet, ^th F. S. Cavalry. The ramp consists of 7 boards
1 .5 in. X 7 in. X 12 ft., joined together in three sections (2 for the

PUTE 53.

Railroads. 229

outside, "A," *'A"; and 3 for the middle one, *'B"); by wooden
strips "C' 1 in. tliicli, and 2 in. wide, bolted to the upper surfaces,
1 ft. between centers; these strips also serve as footholds. Along
the middle of the outside boards extends a side rail, *'D," 3 in. x
3 in., held firmly by the iron straps, *'E," i^ in. x 2 in. On the out-
side of each side rail are 3 sockets "F," for standards "G" 3 ft.
high, along the tops of which are to be stretched ropes or chains
from which canvas or blankets are hung. On the under side of
each section 3 ft. apart are bolted iron cleats, *'H," 0.5 in. x 2 in.,
beginning at 18 in. from the ends. On the ends of each section are
bolted iron claws, "K," for catching the car floor or door slide, to
prevent slipping when in position for use. The three sections are
held together for use by 4 iron tie bars, "L," 0.5 in. x 2 in., which
are placed under the cleats "H," and the whole firmly keyed as
shown. This form of ramp may be made longer or shorter, nar-
rower or broader, as desired. By taking out the standards it may
be hung on the side of a car between a door and end. It is easily
taken apart and transported in a wagon, and as easily put to-
gether when needed. It is designed to combine both strength
and lightness. It weighs about 400 lbs. complete.

398.— Disabling and destroying railroads. Under the heac}
of di8al)ling will be mentioned means, the effects of which will
only temporarily interrupt traffic, can be easily repaired, but will
cause delays.

399.— Under deMroying, such as are more serious in their
effects; either causing extensive repairs or a change of route to
avoid them.

400.— The disabling of railroads will usually be done by raid-
ing parties of cavalry, while the destroying of them may be done
by such parties or specially detailed troops trained for such
service.

401.— It must be understood that no railroad is to be destroyed
except upon the orders of the officer commanding in the field.
If otherwise, and it should be taken from the enemy, the dam-
age done might seriously embarass future operations. Before
ordering any destruction the questions will arise — *'Is destruction
absolutely necessary?" "Will it be of no further use and is every
hope of regaining it gone?" "Are the advantages to be gained
sulflcient to compensate for the damage that will be done?" All

230 Itaitroads.

the attending circumstances should be carefully considered, es-
pecially if in one's own country. The choice of points for de-
struction and the most effective means are subjects for study. It
is useless to destroy anything that will not seriously embarass
traffic.

408.— A railroad may be disabled by removing rails at vari-
ous intervals, then destroying or hiding them; or, if a large num-
ber of men are at hand, select a high embanlsment, line the men
along on one side of the track, disconnect the rails at each end of
the line of men, then, at a signal, they raise the track on edge and
let rails and ties together go over the embankment. Thus treated,
rails and ties must be separated before being replaced. An im-
provised wrench for removing nuts on fish-plates is a bolt with
two nuts on it, just far enough apart to grasp the nut to be re-
moved. (PI. 52, Fig. 5.) If time is an object, remove outside
rails on a curve, or disconnect a joint on each side and throw them
as a switch to derail the train either on an embankment or in a
cut, or use explosives as described in Chap. XX.

By laying rails across a pile of burning ties until red hot in the
middle they may be easily bent around a tree or telegraph pole;
they may be twisted by heating, as above, then using bars or pick-
axes placed in the holes in each end and working in opposite
directions.

They may be torn from the ties and twisted cold by using Gen.
Haupt's "U"-shaped rail-twister, shown on PI. 40, Fig. 8. Ten
men with two twisters, two axes, two stout pieces of rope 35 ft.
long, can tear up and twist a rail in 5 minutes. The junctions of
lines are important points to attaclc to disable a track.

Water tanks may be rendered useless for a time by breaking
holes in them, removing pistons from pumps, etc. Fuel, ties, and
small bridges may be burned. Engines may be disabled by burn-
ing: out the flues, removing or breaking different parts of the ma-
chinery, filling suction pipes of pumps with waste, etc. Cars may
be disabled by removing couplers, axle boxes, breaking or remov-
ing trucks, etc. The use of mines under the tracks, so arranged
as to be exploded by the passing of trains, is an effective method
of interrupting traffic and shaking the morale of troops being
transported.

403.— To destroy a railroad, if time is sufficient, remove roll-

Uattroddi. 231

Ing stock, rails, etc., to the rear. Otherwise, destroy large bridges,
if of wood, by burning, using oil If it can be obtained, or by ex-
plosives, as in Chapter XX.; if of iron, steel, or masonry, by ex-
plosives, as in Chapter XX. If there are tunnels on the line,
select longest ones and blow them in at as many points as possi-
ble, or cause two wild trains to collide in the middle, afterwards
blowing in the ends. Those with sandy soil are the best. Deep
cuttings with retaining walls may be filled in by use of explo-
sives. If trees, poles, wires, etc., can be mixed in— so much the
better. Blow up tanks and engines, burn all fuel, cars, repair
supplies, etc. Fire a cannon ball through engines.

404,— The repair of railroads will best be accomplished by
a construction corps having some of the elements of permanency
in its organization; or, at least, by small squads of experienced
men, to which others could be added by temporary detail, when-
ever active operations require such increase. They should be
established as near to where their services may be needed as
possible.

405.— Bridges should, in the beginning, be classified and num-
bered, so that a single reference to the class and number will give
complete information as to its character, dimensions, etc. At
designated points will be kept on hand, already prepared for put-
ting in bridge, suitable materials for the repair of each class.
This was done by the Union Army from 1801 to 18G5, so that,
when word was received that a certain bridge had been destroyed,
by a reference to the class and number the reconstruction corps
started out carrying with it just what was needed to repair the
bridge. Even complete trusses for the larger class of bridges
were prepared and kept ready for use.

406.— Tunnels and cuts which have been filled up can gener-
ally be cleared only from the two ends.

407.— Rails, fish-plates, spikes, ties, etc., will be kept in store
at secure places, for repairing any portions of destroyed track.
Rails which have been simply bent can be straightened by various
means. Oen. Haupt's method was as follows: Two ties were
placed on the ground, across these two more ties and on top a
single tie, which was cut across one-half the depth of the rail
to receive It and prevent it turning. Weight was ai^plied at the
two ends of the rail by men bearing down on poles placed there-

232 Railroads,

on. The rail being moved back and forth until straightened, re-
quiring from 4 to 5 minutes. Kails which had been heated and
bent to a very sharp angle required more time, necessitating re-
heating and hammering until straightened. For this purpose, at
special points, were prepared furnaces consisting of two parallel
walls of brick, stone or clay, with a kind of grate. The straight-
ening table consisted of a large, square timber as long as a rail,
on which were securely fastened three rails, as in PI. 52, Fig. 9,
on which the heated rail was laid and hammered until straight-
ened. Twisted rails require rerolling before they can be again
used.

mmu

CiSAPTEB XIX. —Telegraph and Telephone Lines.

408.— In order that telegraphic messages may be sent from
one point to another, it is necessary that there be a continuous
metallic conductor from the first to the second point, and that
tills conductor be insulated from contact with the ground or with
anything leading to the ground. The conductor used in construct-
ing permanent lines is of galvanized iron wire, generally of size
IS^o. 9. In military lines it is generally somewhat smaller on ac-
count of the weight. The wire is carried on poles and tied to glass
insulators which are attached to the poles.

409.— Poles should be not less than 22 feet in length nor less
than 7 and 5 inches in diameter at the larger and smaller ends
respectively, and should be stripped of bark and pointed at the
npper endi The holes for poles should be not less than 1-6 the
length of the pole in depth. The poles should be raised as shown
in PI. 54, Fig. 1, and held vertically while the excavated earth is
thoroughly tamped in from bottom to top; after the hole is com-
pletely filled, the earth should be made into a small mound so as
to shed water.

410.— When the brackets are attached to the pole directly, a
seat should be cut in the pole with a hatchet and the bracket
should be nailed on, using 1 twenty-penny and 1 forty-penny
nail. Where the poles are intended to carry several wires, cross-
arms are bolted to the poles, fitting into seats cut for them. The
arms carry brackets not less than 15 in. apart. The arms should
not be less than 20 in. from one another. Not less than 25 poles
to the mile should be used, and in special cases the number may
be increased to 30.

411.— Every 5th pole should be protected from lightning dis-
charges by having a piece of line wire run from about B in. above
the top of the pole to the ground. This wire must be so arranged
that it cannot come in contact with the line wire should that
become unfastened. Poles should be vertical evcept when nec-
essary to incline them to resist strains, when they will be set
at a slight inclination. In such manner that the component of
the strain Jn the direction of the length of pole will tend to
press it into the ground. Where exposed to great strains, or

236 Telegraph and Telephone Ldnes.

to continuously high winds, it may be necessary to guy the
poles: this is done with stays consisting of two or more line
wires twisted together and fastened near the top of the pole, the
ground end being attached to a section of a pole or timber suita-
bly anchored in the ground, as shown in Fig. 2. Where possi-
ble, the line of poles should be run on one side of the road and
far enough from it to be safe from accidental damage by pass-
ing wagons. Where roads have to be crossed, the wire should
be carried over on high poles so as to clear any possible wagon-
load.

412.— The insulators in common use in this country are of
glass and of the form shown in Fig. 3. The one shown in Fig. 4
is preferable, as it is not so liable to cause leaks on account of
moisture accumulating and forming a connecting film to the
bracket and from that to the pole.

413.— The wire is attached to the insulators by pieces of wire
called ties. These are generally of the same wire as the line.
They are annealed and formed on an insulator and cut long
enough to embrace the insulator and project 3 or 4 inches beyond .
the line wire.

414.— To hang the wire. The wire is carried up to the top
of the pole and the lineman places a tie on the insulator, the line
wire against the insulator above the tie wire, and bends the
ends of the tie wire upw^ard so as to sustain the line wire. The
line wire is then strained by the lineman, either by means of
hand power or by use of the wagon carrying the reel. When
the line wire is stretched so that it sags but about 1% ft. in 70
yds., the tie wire is wrapped aroimd it about one and a half
times, finishing with the ends of the tie wire pointing towards
the insulator; this secures the line and completes the work.
(Fig. 5.)

415.— In open country the line wire is strung on the insulator
on the side towards the pole, so that, if it becomes accidentally
undone, the wire will not drop. If in timbered country, then
hang it on the side from the pole, so that when trees, etc., fall
against the wire it will simply tear it away from the insulator,
but will not break the line wire. When necessary to hang the
wire on trees, a regular tree insulator should be used, and in
default of this, the tie shown jn Fig. 6 may be ys^, the ends

Telegraph and Telephone Lines. 287

being wound loosely so as to allow of an easy lateral motion to
accommodate the swing of the tree. The poles should be num-
bered at each mile so as to aid linemen to report location of breaks
and repairs.

Streams are crossed by hanging the wires on strong, high sup-
ports, taking care not to strain the wire so much as to cause it
to break.

416.— The description of instruments and batteries, their con-
nections and care, will be found in the Manual published by the
Signal Service of the Army.

417.— Joints. Where wires have to be joined to preserve the
continuity of the metallic circuit, the best joint is the American
twist joint. To make this clean the wires for a length of 5 or 6
Inches, make a right-angle bend in each wire about 4 Inches from
the end, now join the wires so that the ends project on different
sides and clamp both wires with a hand vise, then with a splicing
iron turn the ends around the line wire, making the turns as close
as possible; after the entire end is turned around the line wire,
cut off the projecting end and dip the joint into meljted solder;
this protects the joint against rusting. The details of this
joint-making are shown in Figs. 7 and 8.

418.— Military lines are generally of the kind designated as
flying lines— i. e., they are intended to accompany the army in
the field, are constructed quickly for temporary use, and are as
quickly dismantled and taken up. The poles used are small poles
called lances, each about 2^^ in. in diameter and 17 ft. in length,
placed 2 ft. in the ground, and run about 4Q. to the mile. The
batteries, line lances, and instruments are carried in wagons
which accompany the army. A detailed description of the tele-
graph, with directions how to erect and dismantle, is found in the
Manual of Signals for the IT. S. Array. The ordinary telephone
receiver (with magneto call bell) is used on the military lines; but
for the use of outposts, reconnoiterers and scouts a special form
of telephone cart and wire has been adopted, the following de-
scription of which Is taken from the Report of the Chief Signal
Officer of the Army, 1892:

"The frame of this cart is constructed of bicycle tubing, and
30 in. bicycle wheels with heavy cushion rubber tires are used.
The cart is fitted with an autQwatic spooling device for reeling

238 Telegraph and Telephone Lines.

up the outpost cable. This device was made by F. S. Cahlll &
Co., and Is a success. The cart carries 5 reels of cable and 1 reel
knapsack for use in places where the cart cannot penetrate
owing to underbrush, etc. As the extreme width of the cart,
measured at the wheels, is only 26 in., it can follow any ordinary
path through underbrush. The weight of the cart complete
with spooling device, but without the reels, is only 53 pounds;
when loaded with reels and reel knapsack, the total weight
is 157 pounds. The cart is well balanced upon its axle by a
device which permits the point of support to be changed to bal-
ance the cart as the distribution of the weight is changed by
the cable being run out. In connection with the reel cart a tele-
phone kit is used, and by attaching the double connector of the
kit to one on the frame of the cart the telephone is kept in cir-
cuit and conversation can be kept up with the home station.
The cart with its load can be easily drawn by one man, and by
its use it will be possible to connect outposts with the main
guard, or brigade with regimental headquarters, or brigade
with division headquarters, in a few minutes of time. The ex-
perience of the English in Egypt has proved the value of the
field cable line in action, as by means of these lines the Com-
manding General was kept in communication with different
divisions of troop*? and with those actually engaged in the firing
line. It is proposed to fit shafts to the cart so that a horse can
be harnessed to it. thus securing srreat rapidity in running out
the cable. The cart carries 1 2-.S miles of cable, which can be paid
out as fast as a man moves with the cart, and bv means of the
reeling apparatus and spooling device can be recovered at the
rate of 4 miles per hour, or as rapidly as a man can walk with
the cart."

419. — Faults are geT^ei^allv of three kinds — breaks or discon-
nections, leaks or pssoapps. and crosses or contacts.

"Rrepks ncmjr when the m^t^lbV circuit ^a hroV'^n or c"t p»o that
either the disconnection is complete, as when entirely severed: or
incomplete, when partiallv cut or whprp « loint Is rusted so much
as to increase the conductive* rcp^'^'+nripo. Tp these cases the In- ■
strnments will work weakly or fail entirplv.

Xienlcs or escp-nes. "W"here the insula tion i« f?pstrovo<i or 1«?
defective, o? where a wire comes in contact with a conductor to

Telegraph and Telephone Lines. 239

the earth or with the earth itself, a portion of the current leaks or
escapes. When the wire is swinging, the leak will be intermit-
tent; when constant leakage is going on, the instruments will
work weakly; failing altogether when the leak becomes complete,
then it is called a ground.

A cross occurs when two wires, each carrying currents, are
brought into contact; thus the instruments on one line will in-
terfere with the workings of those on the other. Generally
occurs from parallel wires being swung over one another by
the wind, or having a good conductor fall so as to touch both
wires.

420.— Telegraph lines should never be damaged or destroyed,
except in obedience to direct orders. Faults may be made by
connecting the wires together with small wire (this makes a bad
cross), or they may be connected with the lightning rods on the
poles, thus running them to the ground.

When an office is taken, the instruments should all be discon-
nected and destroyed or taken away; the ends of the wires should
be tied together. The batteries, if any, should be disconnected.
To destroy the line, cut down the poles and burn them and cut
the wire into small lengths. Subaqueous lines should be brought
up with a grapnel and a piece cut out and cut into small
pieces and thrown back into the water. Subterranean lines are
generally laid in conduits, and at regular intervals man-holes
are built to allow of repairs; the line may be detected by these
man-holes, the conduit destroyed, and the cables disconnected.

-16-

CHAPTER XX.— Demolitions.

421.— In military operations demolitions must be made with
the least possible expenditure of time and explosive. Neverthe-
less, a charge which in itself seems large for the object intended
may prove economical, in that it errs on the right side and a repe-
tition of the work is not made necessary.

Military engineers, or troops acting as such, may have to de-
stroy bridges, houses, walls, railroads, tunnels, stockades, pal-
isades, gates, cannon, etc., break up roads, fell trees and place
mines. On account of their portability, great destructive efifect
and facility of handling, high explosives should generally be
used in all these oi>erations. However, where ordinary gun-
powder is available, it may be used to advantage, if time permits
its proper placing and tamping. Gun-cotton is the standard
explosive for military work, and all formulas are calculated for
its use.

422.— Gun-cotton, as made at the IT. S. Naval Torpedo Sta-
tion, is in blocks about 3 in. square and 2 in, thick; each block
is perforated to allow the insertion of a detonator, and, when dry,
weighs about 10 oz. When necessarj' to use a smaller amount
than 10 oz., a block may be cut, when wet, by using a saw or
shaiT) knife, care being taken to place it between two boards, so
that it will not flake or crack during the operation.

Gun-cotton, as furnished by the U. S. Ordnance Department,
is in small rectangular blocks weighing about 1-8 oz. The blocks
contain al>out 15 per cent of water, are coated with varnish,
and can be shipped or handled with safety. For use, a paper
or cardboard cylinder is made and the blocks placed in it. The
detonator is inserted in a prepared primer, which is placed be-
tween the blocks.

Gun-cotton will absorb about 30 per cent of its weight of
water, and, when in this condition, is comparatively safe, as it
can only be ignited by fire and is difficult of detonation, "^hen
packed for transportation the blocks are placed, while wet, in
a tin can; the can is hermetically sealed or is left so that the water
can be replaced when it has evaporated.

When both are well tamped, gun-cotton has an explosive force

PLATE 55.

Figure 1.

(0mmiyi/\ / /_z::^

Figure 2.

^ "■ ••'• MT'liiil f

Demolitions. 243

two times as great as gunpowder; when no tamping is used, it
has a force four times as great.

423.— Primers. Wet gun-cotton detonates witli much greater
force than dry, but it is necessai-y that this action be set up by
the detonation of a dry primer of gun-cotton placed in intimate
contact with the wet charge. When wet gun-cotton is carried, a
sufficient quantity for a primer may be taken from the wet case,
placed in the sun and allowed to dry; it is better, however, in
operations in the field, to carrj- a small amount of dry gun-cotton,
so as not to waste time in drying the primer.

When used in holes, gun-cotton should be dry, as wet gun-
cotton is difficult to detonate under such circumstances.

424.— Dynamite. Dynamite comes in cartridges or sticks
weighing 8 oz. each, and may be used instead of gun-cotton. It
should not be used, however, if exposed to wet or if frozen.
Frozen dynamite can be thawed by placing it in an apparatus
like a glue pot, the dynamite being in the inner vessel and the
hot water in the outer. It must not be thawed at a fire.

Gunpowder may sometimes be used in demolitions, and when
so employed it should be placed in stout bags, preferably two, the
outer one well tarred. This is to protect from accidental explo^
sion occasioned by sparks from the fuse.

425.— Explosives should be placed in as close contact as pos-
sible with the object to be destroyed, and the packages compos-
ing the charge should be in intimate contact with each other.

426.— Common Detonator. The common detonator is a cop-
per tube, about ^ in. in diameter, closed at one end and partially
filled with fulminate of mercury, which is ignited by a fuse.
The ordinary blasting cap (PI. 55, Fig. 1), or detonator, is in-
tended for use with a fuse, and is designated as single, double,
or triple force, according to the amount of fulminate of mercury
used. In military operations it is better to use the triple-
force caps, as their action is sure, even on comparatively low
explosives.*

427.— The fuse generally used in this country to ignite these
detonators or caps is that made by Ensign, Bickford & Co.,

Simsljury, Conn., the grade known as "double-taped" being the

■ ■

♦Singrle-force caps contain 3 grs., double-force caps 6 grs., and triple-force caps
9 p rs . of fulminate of mercury.

24^ Demolitions.

best for general work when the fuse is not exposed to pro-
longed immersion in water or damp ground. When it is nec-
essary to use fuse for submarine explosives, the water-proof
fuse should be used. The rate of burning of the fuse should
he found by experiment before using. This is done by taking
several pieces, 1 ft. long, and finding the average rate of burn-
ing and taking this as the standard. The rate at which this fuse
is intended to burn is 3 ft. per minute, but it varies somewhat,
so that when great nicety is required it should be tested as
above.

428.— To prepare a fuse and detonator for use, cut the fuse ixi the
length required, leaving a square end; insert this end in the det-
onator until it rests against the fulminate, taking care not to
scratch the fulminate. Then crimp the copper against the fuse so
as to hold it firmly: this is done by means of pincers made for the
purpose; or, in case these are not available, any pincers or the
edge of a dull knife may be used, being careful not to crimp on
the portion of the cap containing the fulminate.

To fire gun-cotton, insert the detonator in the hole in the prim-
ing-block, secure it by tying with wire or twine, and when ready,
light the fuse.

To fire dynamite, a hole is made for the detonator in the end
of the cartridge with a sharp stick or lead pencil and the deto-
nator, with fuse or wire attached, is inserted; the envelope is then
tied around the fuse, so that the detonator cannot become de-
tached from the cartridge, care being taken to place the deto-
nator in the cartridge only about % its length, so that the charge
may not be ignited by sparks from the fuse before the detonator
is exploded.

To fire gunpowder (PI. 57, Fig. 5), the fuse alone is used, being
placed so that the end is well centered in the mass of the powder
and so secure that it cannot pull out.

429.— The simple electric fuse is so constructed that, upon
the passage of a current of electricity through a platinum wire of
sufficient strength to heat the wire to redness, some fleecy gun-
cotton or pthier inflammable material, which is wrapped around
the wire, is Ignited. This fuse may be used to fire a detonator or
to ignite gunpowder.

In PL 55, Fig. 2, is shown a fuse with a cap, which cannot be

PLATE 56.

DemQlitions. 247

removed, contaiaing a detohating coiBpound; hence it can be used
with best effect only in compounds that can be detonated. It is
called the cornmn^cial fuse and detonator.

In PI. 57, Fig. 10, is shown a fuse with a cap containing a det-
onator. The cap can be removed and the fuse used to ignite
gunpowder. It is called the sertnce fuse and detonator.

Gun-cotton and gunpowder are fired as explained in Par. 428.

To fire dynamiite, push the detonator in its full length and take
two half-hitches, with wire, about the cartridges, so as to hold
everything in place. (PI. 5(>„ Fig. 1.)

430.— The Laflin and Band Exploder, No. 3. The current
of electricity is generated by means of a battery consisting of
several cells, or by an electrical machine. The means now gen-
erally used, and the one that gives surest results, is the magneto
machine. On account of its compactness, portability, and sim-
plicity, the Laflin & Rand Exploder, No. 3, is probably the best
for all work where electricity is to be the igniting agent. (PI. 55,
Fig. 3.) The machine is cased in wood, and its dimensions are
13x8x5^ in. It weighs 18 lbs. The machine will fire, under
favorable circumstances, 12 fuses. In order that there may be
no chance of failure, a greater number than 5 should not be fired
in military operations by this machine.

The insulated wire used to make connection between the
machine and fuse is carried on a reel, Fig. 3. The connecting
wires between machine and reel are attached by binding posts,
as shown in the figure.

To use the machine, reel off a suflftcient amount of wire, usually
about 250 ft., and connect with the wires of the detonator; con-
nect the machine with the reel, being careful not to make this
connection until every one is at a safe distance from the place of
explosion. The handle on top of the box is now lifted, with-
drawing the ratchet bar to its full length, and, when the time
arrives to fire the charge, the bar is pushed vertically down-
ward, moving slowly for the first inch or two, then by a rapid
but even pressure, till the lower end is stopped at the bottom of
the box.

When more than one charge is to be fired, the wires leading
to the several charges should be connected, as shown in PI. 57,
Fig. 6.

248 Demolitions.

431.— In all connection of wires, at least 2 in. of eacli wire
must be cleaned bright and well wrapped around one another,
as shown in PI. 55, Fig. 4; under no circumstances simply hook
wires together. After wires are joined, the joint should be in-
sulated by winding rubber tape, or wide rubber bands, around
so as to overlap the next previous turn. When water has to he
encountered, wrap with rag or a strip of linen and cover witli
tar; or, use rubber tube as shown: the tube in this case is placed
on one of the wires, and, when the joint is made, Is pulled over it
and tied tightly to the wires on either side of the joint. (PL 57,
Fig. 9.)

432.— To fell trees, bore a hole at the height desired, insert
the charge, and fire, care being taken that the center of the
charge is about the center of the tree. If the charge be of a
length equal to or less than the diameter of the tree, the hole
may be bored directly through; but if greater, then two or three
holes, intersecting at the center, must be bored, thus putting the
packages of gun-cotton in intimate contact, and requiring but
one detonator. The charge may be calculated from the formula
C=}i T* , in which C is the charge in pounds and T the diameter
in feet.

When time is not available to bore a hole, a necklace may
be used. The charge may be calculated from the formula C=3T »,
in which C is the charge in pounds and T the diameter in feet.

Should the charge be placed or hung against the tree, the
amount as given by the formula for a necktace must be increased
one-fourth.

To make the tree fall in a given direction a rope may be tied
to it, hauled taut, and secured to another tree or strong stake.

The above method of felling trees is more expensive than with
the ax, and is not to be resorted to except in cases of emergency
where time is not available for slower methods. (PI. 55, Figs. 5,
0, 7 and 8.)

433.— To destroy bridge timbers, if rectangular, the charge
is placed across the whole width of the timber. (PL 5(5, Fig. 2.)
The charge may be calculated from the formula C=3WT», in
which C is the charge in pounds, W the width and T the thickness
in feet. If the timbers are circular or square, the formula re-

Demolitions.

duces to C=3T«, and being tlie same as that for trees whe^ a
necklace is used, the charge should be so placed. /

When high explosives are not on hand, the bridge torpedo 1^^^
in the War of the Rebellion may be substituted. It cousins of
a bolt 8 or 9 in. in length, surrounded by a tin cylinder 2/n. in
diameter, which is filled with powder. The ends of the (finder
are closed by iron washers, and a fuse placed in one ^d. To
use this torpedo, a hole 2% in. in diameter is bored in th/ timber
and the torpedo inserted, having its center at the cent;^ of the
timber; it is then exploded by means of a fuse. If ^cessary,
two may be placed in holes bored at right angles to ^ch other.
(PL 56, Fig. 4.) /

434.— To destroy a wooden truss bridge, if time/s available,
the bridge may be burned; to do this, collect brusb^etc, and, if
possible, place it under one end so as to bum it off And cause the
span to drop, but if not possible, build the fire in t)te center of the
span; it will burn through and cause rupture in th/center. If time
is not available, blow away the main brace of l^e panel nearest
to an abutment or pier; it is really necessary to ^ow only one side
down, but it is better to be sure and destroy i^th sides. If the
bridge has an arch of wood besides the trusfe, then destroy the
arch on each side. It is better to attack the ^an over the deepest
water.

435.— Palisades may be cut down withA,xes or saws, the cuts
being made near the bottom; ropes are attached to the tops of
the timbers to assist in bringing them d#wn; or the earth at the
bottom may be dug out and the palisade pulled over.

Palisades, up to 10 in. in thickness, may he blown down, when
the timbers are close together, with 4 lbs. of gun-cotton per run-
ning foot.

436.— Stockades may be cut down with axes or saws, as ex-
plained for palisades.

They may be blown down with 4 lbs. of gun-cotton per run-
ning foot.

If the timbers are squared, the blocks of cotton may be fas-
tened to a thin board and placed against the foot of the stockade;
but if of rough logs, tie the blocks together so that they may
adapt themselves to the form of the timbers.

When stockades are double, and separated by a distance of

»50 Demoliti4)ti8.

Oe yard— 25 lbs. of gun-cotton per running foot or one charge of
SOlbs. may be placed.

lailway-irou stockades are breached by 7 lbs. per running
fooi

I^ all cases, distribute the charge so as to cover the length
desirid to be breached.

43'._QateB may be blown in with 50 lbs. of gun-cotton ex-
ploded in one cliarge. The charge is hung against the center of
gate by means of a sharpened pick or on a nail. This charge is
large, bvt gates will generally be strengthened in some manner
on the in^de. (PI. 57, Fig. 4.)

438.— louseB may be blown down or shattered by placing
charges in 'ihe center of the floor and closing all outlets, -such as
doors, windows, etc. Charge according to the size, 20 lbs. being
sufficient for small houses.

439.— Wal*. The charge should be placed against the bot-
tom, close to fie wall, and, if possible, should be tamped. If
time permits, a channel may be cut in the wall at the seat of the
charge. The chi^ge untamped may be computed from the for-
mula C=%WT«, i* which C is the charge in pounds, W the width
of wall to be breacf^ed, and T the thickness; W and T are in feet.
When tamped with earth equal to the thickness of the wall, half
the above charge majr be used. (PI. 57, Fig. 2.)

440.— Masonry bridge piers may be destroyed by a charge
calculated from the fo?mula C3<= %WT«, C, W, and T being the
same as in par. 439. In order to avoid using so much gun-cotton,
it is better to place small charges in chambers excavated as deep
as possible in the masonry, and explode all simultaneously; cal-
culate charges as for walls.

441.— A masonry bridge arch may be destroyed by attacking
the haunches or the crown. The haunches are the best points of
attack, two trenches being dug across the width of the roadway
down to the back of the arch. If this is not possible, attack
the crown. A single trench across the width of the roadway
may be used, but it is better to use two, each placed from the
crown a distance equal to one-half the width to be breached. The
charge untamped may be calculated from the formula C=%WT«.
In which C, W, and T are the same as in par. 439. When the
charge is tamped with a depth of earth equal to the thickness of

Demolitions. ' 251

the arch, one-half tlie amount given by the formula is used. (PI.
57. Fig. 3.)

442.— Tunnels may be destroyed by placing charges baciL of
the masonry at the spring of the arch. If possible, the charge
should be placed in a chamber excavated behind the arch and
well tamped. Tunnels should be blown in at several places, so
as to render it impossible to repair them in a short time. Charges
as for bridge arches. (PI. 57, Fig. 8.)

443.— Ta cut steel rails, use one block of gun-cotton, weight
8 ozs., tie the block against the web of the rail with wire or twine,
and, if possible, tamp well with earth, and explode. (PI. 50,
Fig. 3.)

To blow a piece of some length out of a rail, arrange two
charges of 8 ozs. as shown in Fig. 5, placing one on each side of
the rail at a distance apart of 5 or 6 ft.; these should be exploded
by use of a magneto machine, so that the action may be simul-
taneous in both charges; the section will be blown out and turned
on its center, making a large opening.

444.— Switch points may be destroyed by lodging 8 ozs. of gun-
cotton between the outer rail and the pivot end of the switch
point being careful to tamp as completely as possible. ("A," PL
51, Fig. 11.) In the case of frogs, 8 ozs. placed in the angle of the
frog will destroy the point and render it useless. ("A," PI. 52,
Fig. 1.)

A great length of railway may be disabled at a very rapid
rate by making use of hand-cars loaded with gun-cotton, pre-
pared lengths of fuse Inserted* into detonators, torches, and
copper wire for binding the gun-cotton to the rail. One non-
commissioned officer and seven men will be necessary; two run
the hand-car; two sit on the hand-car and fix the detonators to
the gun-cotton, prepare binding wire and hand out the charges;
two men receive the charges and bind them to the rails; two
follow at about 150 yards in rear and fire the charges as they
pass.

445.— To cut wrought-iron plates, the charge is found from
the formula C=1.5Wt *. in which C is the charge in pounds, W the
width in feet, and t the thickness in inches. The charge should
be placed entirely across the plate to be cut.

446.— To cut an iron bridge beam or girder (PI. 56, Figs. 6

252 Demolitions.

and 7), calculate the charge for each separate cross-section to
be cut, using the formula in par. 445, and add the results; the
sum will be the charge required. The charge is most conven-
iently placed on the side of the beam, reaching entirely across
and bound on with wire, tlie primer being in the center of the
charge. If possible, a board should be tied over the charge and
earth tamped around it. When time is not available for placing
the charge as above described, it may be laid on top of the t>eam
or on the flange.

447.— Girder bridges not longer than 20 ft. may be overturned
by levers and thrown off the abutments. When this cannot be
done, the gun-cotton charge may be calculated and placed as de-
scribed for iron girders.

448.— In iron truss bridges the most favorable place for the
charge is at the center of the span on the lower chord. When
the bridge is of the variety known as a deck bridge, the charge
should be placed on the top member. When the lower or ten-
sion member is composed of eye-bars, the charge should be placed
between alternate pairs of eye-bars as near to the coupling-
pin as possible. The charge may be calculated as in par. 446.
(PI. 57, Fig. 1.)

449.— When bridges are supported by iron or wood piers, it is
sometimes possible to destroy the piers, and thus bring down the
entire structure. In attacking a pier, it is best to blow out the
supports on both sides, as this will bring down all of the bridge
resting on the pier. The charges may be calculated, if of stone,
by par. 440; if of iron, by par. 445.

450.— In destroying suspension bridges, blow down the tow-
ers below the saddles, excavate and blow out one of the an-
chorages, or cut the cable with gun-cotton. The charge for
bridge cables is calculated as for cutting iron plates; the charge
must be carefully placed, so as to be in close contact with the
cable. If the cables are made of plates, the plates may be cut
with gun-cotton, as in the case of eye-bars cited above.

451.— Field and siege guns may be disabled by detonating
iy2 pounds of gun-cotton on the outside near the muzzle. For
heavier fortress guns, detonate 4 pounds in the bottom of the
bore, tamping with sand. Tlie carriages may be destroyed by
using gun-cotton.

PLATE 57.

iFIG.l.

PIG. 2.

FIG.3.

FIG8.

riGW. "• Service /L«.

' tfmtrcuru.
, ■ lo r« t4 onartt. '

*. pluf efbaaehwooa

PIG. 9.

Demolitions. 255

452.— Approximate Relative Strength of Some of the High
Explosives.

ISxplosive gelatine 128.3

Nitro-glycerine 120.3

Gun-cotton 100.

Dynamite, No 1, 75 per cent Nitro-glycerine 97.8

Rack-a-rocli 74.2

Dynamite, 50 per cent 72.7

458.— Destruction - of Obstacles. Wire entanglements may
be destroyed by cutting witli wire nii>pers, or, if they are not at
hand, then the ordinary hand-ax will do, taliing care to cut against
tlie picliet.

Abatis is very difficult to destroy and cannot be removed
while fire can be brought to bear on the spot. Pry up the picli-
ets with levers and attach ropes to the butts of trees and haul
away.

Small pickets are cut through with the ax, or, if possible,
pulled up.

Small pits are filled with earth, brush, or covered by planks,
fascines, or bales of hay.

Automatic torpedoes are easily destroyed by driving animals
up and down the line suspected of containing them.

454.— The following table gives in a concise form all informa-
tion necessary for the use of gun-cotton and gunpowder. The
table shows approximately the value of the different high explo-
sives as compared with gun-cotton.

NOTE.— Charges are in lbs.; W and T are in feet; t is in Inches.

W is width of breach to be made; T or t is thickness of object
to be demolished.

Gunpowder is assumed to be roughly tamped with sand-bags.
Gun-cotton is untamped. If the gun-cotton is tamped, the charges
may be reduced by about one-half.

Charge of gun-cotton must be equal in length to the breach
which is to be made.

-17--

256

Hasty Demolitions.

Object Attacked.

Brick arch ^

Brick wall, 2 ft. or
less

Brick wall over 2 ft.
thick

Rrick piers

Hardwood (e ^.,oak,
elm), in any form
whether stock-
ade, palisade, sin-
gle timbers, trees,
etc.

iWT» -

I
40 to 100
lbs. for
stockade

Soft wood .

Breastwork of hori-
zontal balks, or
earth between
sleepers up to 3 ft.
6 in. thick

Heavy rail stockade.

Fortress gate
Iron plate ....

Field or siege guns . .

Heavier guns .

First-class iron rail . .
First-class steel rail . .

Gunpowder

Half the
for hard

60 to 80
lbs. per
5 ft.

200 lbs.

Gun-cotton

2 lbs. per
foot run

tWT»
3WT2

|T2

charges
wood.
4 lbs. per
foot.

7 lbs. per
foot.
50 lbs.
JWt^

Ih lbs.

4 lbs.

10 ozs.
8 ozs.

Remarks.

The length of

bleach, W, should

^not be less than the

height of the wall

to be brought down.

In a concentrated
charge, or for trees
not over 12 in. diame
ter, in a necklace.

In auger-hole, when
the timber is not per-
fectly round, T = the
smaller axis.

In this case only, t
is in inches.

On chase near muz-
zle.

In bottom of bore,
tamped with water or
sand.

Touching web of
rail and near a chair.

Four rails placed
round the charge will
be cut simultaneously
by it.

CHAFTEB XXI.— Camping Expedients.

455.— There are a few general principles which should be ob-
served in selecting a camp, whether the troops are to be estab-
lished in bivouac, in tents or in huts. These principles relate to
the health and comfort of the troops, the facilities for communi-
cation, the convenience of wood and water, and the resources of
the locality in provisions and forage.

456.— For an intrenched camp the gix)und must be selected
with particular reference to its adaptability for defense and the
camp arranged with that object in view, at the same time observ-
ing as many of the other requirements as possible.

457.— Dry and healthy sites, dependent on soil: Qramte,
nietatnorphic and trap rocks, usually; day slates, but drinlving wa-
ter is scarce; Umestmie generally, but the water is hard, clear
and sparkling, though sometimes contaminated; deep permeable
sandstones, if the air and soil are dry; deep gravels, unless lower
than surrounding country; pure sand, deep and free from organic
matter; well-cultivated soils generally; gravelly hillocks, the very
best.

458.— Unhealthy sites, dependent on soil: Magnesium lime-
stone; shallow sandstone underlaid with clay; clay and alluvial
soils generally; rice fields; made soils usually; newly plowed
ground,

459.— Healthy sites, independent of soil: The hest is on a
divide or saddle, unless too much exposed or without water. The
next best is near the top of a slope, and the southern side is prefera-
ble to the northern; banks of running rivers are good, if not
marshy.

460.— Unhealthy sites, independent of soil: Enclosed valleys,
ravines, or th^ mouths of long ravines, ill-drained ground, the neigh-
borhood of marshes, especially if the wind blows from them. If
forced to camp near a marsh, the windward side should be select-
ed, and, if possible, have a hill or a screen of woods or brush be-
tween the camp and marsh. Moss generally indicates marshy
ground.

4Ql._Sites affected by surrounding vegetation: Herbage,
or closely lying grass, is always healthy, but should be kept

258

Camping Expedients.

cut and all weeds destroyed; heavy brush about a marsh should
not be removed. Trees, In cold countries, break the winds;
in hot countries they cooj the ground and may protect against
malarial currents; so should only be removed with judgment.

462.— In selecting camps, wood, water, and grass should be
secured, if possible, together with good drainage, but marshy
ground should not be occupied even for a night.

Old camp-grounds should never be occupied, If avoidable;
instead, go as far as possible to the windward side of them.

The site having been selected, the details of castrametation.
or the laying out of camps for the different arms, will be found in
the authorized Drill Regulations of each.

463.— Water is more immediately necessary to life than
food.

Each man requires, on the march, for drinking and cooking 3
to 4 quarts per day, and an equal amount for washing. In sta-
tionary camps, 5 gallons per day for all purposes.

Hospitals require several times as much per man per day.

Horses, mules, and cattle require from to 10 gallons each
l>er day for drinking. It should be soft and clean, if possible.
Sheep and hogs reiiuire from 2 to 4 quarts each per day.

464.— /f is imperdtivCj on goinij into camp, that the supply he imme-
diate y looked after and a gn4ird placed over it. If the supply be
small, special precautions must be taken and an officer put in
charge.

465.— Good drinking water should be bright, colorless, odor-
lees, free from sediment, of pleasant and sparkling taste.

Rain water, collected from a clean surface, after the atmos-
phere has been well washed, is the purest in nature. Springs
whose oriarins are remote from habitations, streams flowing
through uninhabited regions, and large lakes, furnish the next
best sources of supply.

^66.— Tf the supply he frmn a lake, pond, or stream, separate
places for obtaining water for men and animals must be marked
out, and care taken that the margin is not trampled into mud and
the water made turbid. Where this is likely to occur when ani-
mals are watered direct from the source of supply, a hard bottom
should be formed for them to stand on, and a barrier formed to
prevent them going out too far.

Cumping Expedients, 25&

It is better, when convenient, to arrange rows of sunken half-
barrels, or board troughs raised above the ground, into which the
water can be drawn. If the supply be limited, it may be neces-
sary to connect the troughs to prevent waste; if not limited, each
should be supplied direct from the source and the overflow
drained off. Even when drinking from a running stream, the
animals below get foul water. To prevent the ground around the
troughs becoming muddy, it should be paved and drained along
the whole length and for a distance of 10 or 12 ft. back. Where
troughs cannot be constructed, trenches lined with puddled clay
may be made to answer.

Arrangements should be made so animals may be brought up
from one direction and leave in another without confusion or
crowding.

467.— Jf the supply he from a stream^ the water for drinking
and cooking for the troops is drawn highest up; for the animals
to drink, next below; and for washing, bathing, etc., lowest down;
while all drainage should enter below where any water is
taken.

If the stream be small, it may be necessary to construct a
series of small reservoirs by building small dams across. Ani-
mals drink better and more rapidly where water is 5 or 6 in.
deep.

468.— If unavoidable, water from small ponds and shallow
wells should only be used after being boiled half an hour, then
aerated and filtered.

469.— /f the supply he from springs, each should be enlarged
and surrounded by a low puddled wall, to keep out surface drain-
age. They may be lined with casks or barrels charred inside, or
gabions, afterwards working in puddled clay between the earth
and linings. The overflow may be received into a succession of
casks let into the ground close together.

Surface springs should be sought for in hollows, at the foot
of hills, where the earth is moist, the grass unusually green, or
the thickest mists arise mornings and evenings.

470.— If water is not immediately available, it may be neces-
sary to dig wells. The most expeditious means of doing so is to
use Well Augers, (PI. 58, Figs. 1, 2, and 3.)

471.— To dig a well, an auger is attached to a rod suspended

260 Camping Expedients.

from a rope passing over a pulley at the top of a derrick or tripod
and thence to a windlass. To the auger rod is secured an arm or
arms, by which the auger is turned by hand and so screwed down
into the earth. About eight turns fill the auger, which is then
lifted, emptied and replaced.

472,— The auger for horitvg in quicksand (Fig. 3) is shaped simi-
larly to the ordinary wood-boring auger, but with a hollow shank,
so that, when lifted, no suction is produced. When the thread be-
comes loaded, the auger is drawn up into an enclosing cylinder,
removed from well and emptied.

473.— Driven wells. The driven tube-well consists of a tube
about 3 ft. long, perforated with holes, and furnished with a steel
point of bulbous form (Fig. 4) and as many other plain iron tubes
as may be necessary.

The form of the point serves to clear a passage for the sockets
by which the tubes are screwed together.

474.— To drive a well, a tube is screwed to the point (Fig. 5)
and on this a clamp is fastened by two bolts at about 3 ft. from
the lower extremity of the point. Next, an iron driving weight,
or monkey, is slipped on the tube above the clamp. The tube thus
furnished is I'aised and held vertically in the center of a guide,
in which it is retained by a latch. The whole being now arranged
in position, ropes are made fast to the monkey and passed over
pulleys on the guide, and driving commenced by two men pull-
ing the ropes and allowing the monkey to fall on the clamp. As
soon as the clamp reaches the ground, the monkey is raised and
held up, the clamp loosened and raised 1.5 or 2 ft., tightened,
and the driving continued as before until the top of the tube
comes below the hole in the top of the guide head, when the
lengthening bar (Fig. 7) is dropped into the top of the well-tube.
The lengthening bar consists of a length of the well-tubing with
a smaller pipe brazed into one end and projecting about 1 ft.,
which fits into the well-tube. This bar keeps the tube steady
and serves as a guide for the monkey to slide on until the top
of the well-tube reaches to within a foot of the ground. The
lengthening bar is then removed, another tube is screwed on,
and the driving continued until water is reached. A hollow
iron plumb is frequently lowered into the tube to ascertain when

PLATE 58.

Fig 2.

Fig.l3

Clamping tlxpedimis, 26S

water has been reached or whether earth of any kind has got
into it.

Accumulations in the tube, of a loose sandy nature, can be
pumped up, by screwing a funnel (Fig. 8) on top of the tube, then
lowering into it through the funnel a small tube with a pump
attached. Water poured into the funnel runs down outside the
smaller tube and is pumped up through it, bringing the mud and
sand. When water is struck, and stands several feet in the tube,
the pump is screwed on to the well-tube.

The well can also be driven without the use of the tripod sup-
ports (Fig. 6), care being taken to keep the tube vertical by means
of guy-ropes. Such a well can be driven from 10 to 20 ft. per hour.
Tlie tubes can be withdrawn without damage by reversing the
operations of driving. (Fig. 9.)

475.— The tube-well is not intended for piercing rock, or
solid stone formations, but is quite capable of penetrating very
hard and compact soils. When striking rock, stone, or deep beds
of clay, it is best to pull up the tube and try in another spot, for
by going a little distance off water will in many cases be found.
476.— Clarification of water. Water usually contains min-
eral and organic substances m solution and in suspension. Sub-
stances in solution completely disappear and cannot be entirely
liltered out. Substances in suspension do not entirely disappear
and may be filtered out.

477.— Z7ard water contains one or moi'e substances^ as lime, mag-
nesia, iron and others, in solution, which are liable to produce
intestinal troubles to persons unaccustomed to them. Cooking
vegetables in it is very difficult. Washing with it requires a
great deal of soap.

The hardness of water may be partially removed by boiling
for half an hour or so, or by adding a small quantity of wash-
ing soda, or by adding a couple of ounces of quicklime to 1(X)
gallons.

4:78,— Substances in suspension may be largely removed by pre-
cipitation and filtration.

479.— Precipitation is allowing such matter as will to settle
through its greater specific gravity, or by inducing it to do so
through some harmless chemical or mechanical action. For
which purpose may be used about grains of crystallized alum

264 Camping Expedients.

to the gallon, or tannin in small quantities, and letting stand sev-
eral hours before using; bruised cactus leaves, also tea leaves
that have been used, act similarly; citric acid, 1 oz. to 16 gal., or
borax and alum, 1-3 oz. each, or 1 to 2 tablespoonfuls of ground
mustard to a barrel, improves water.

480.— Filtration is mechanically arresting and attracting sus-
pended matter, and removing dissolved matter in the water. Fil-
tering materials act only for a short period and should be fre-
quently cleaned.

^%l,—M(ht€riaU which map he used are sponge, wool, and like
articles for straining, but must be constantly removed and
cleaned. Clean sand, gravel, and porous stone remove sus-
pended matter, but have little or no eflfect on dissolved organic
matter. Iron sponge, a compound of sawdust and iron oxide
heated in a furnace, and Carferal, a composition of charcoal, iron,
and clay, are efficient for removing mineral matter. Bone-black
or animal charcoal, and wood charcoal, when freshly burned, ab-
sorb mineral matter for a couple of weeks, but their chief action
is on organic matter.

482*— .Charcoal may be made by digging in the ground a cir-
cular pit, some 6 in. deep by 4 or 5 ft. across, then placing a large
pole or bundle of brushwood vertically in the center. Around
this the wood to be burned is piled, forming a kind of cone. The
pile is then covered with brush, and on this a layer of 4 or 5 in. of
earth. (Fig. 10.) The center pole is then removed and a fire
lighted in its place, receiving air from vents left at the bottom for
that purpose. The fire proceeds from the center outwards, and.
if burning properly, the smoke is thick and white. If it does
not spread to every part, new vents must be made. If the smoke
becomes thin and a blue flame appears, it is burning too fast, and
vents must be stopped up or more earth thrown on. When the
smoke ceases to escape, the vents and chimney are closed and the
pile allowed to stand for a couple of days until it cools.

From 20 to 25 per cent of charcoal is thus obtained.

483.— A convenient portable filter (Fig. 11) is made by
taking a small cylinder of compressed carbon and inserting it
in a rubber tube in such a manner that the carbon end may
be immersed In the water, then applying the mouth to a mouth-
piece at the other end of the tube, and drawing the water through.

Camping Expedients, 265

484.— The Success Filter {Fig. 12) consists of a cylindrical
porous stone 4 in. long by 4 in. in diameter with a hole bored in
one end. In this is fitted a rubber gasket, through which passes
an iron tube that is fastened into the bottom of a barrel, jar, or
bucket. The water filters througli the stone into the hole inside
and passes out through the tube into a receiving vessel below.
(Fig. 13.)

By fastening the iron tube into the bottom of a large empty
tomato or peach can, in which the stone is placed on the tube and
wedged fast, then fastening a rubber tube 2 or 3 ft. long on the
iron tube outside of the can, a syphon filter is obtained. The
action Is set up by exhausting the air from the stone, after the
can and stone are immersed in water, by sucking on the end of the
rubber tube until the water is started.

485.— A simple water filter may be made by stuffing a
piece of sponge in a hole in the bottom of a cask, flower pot, or
other vessel (Fig. 14), then placing above this a layer of coarse
sand, then a layer of pounded charcoal 3 or 4 in. thick, then
another layer of coarse sand and on this a layer of coarse gravel.
The layers should be thick as possible, and tightly compressed,
and washed thoroughly clean before being used. The differ-
ent layers may be prevented from mixing by perforated boards,
or otherwise. Another form may be made as shown In Fig. 15.

486.— Casks, or barrels, charred on the inside (and occasionally
cleaned, brushed, and recharred), improve water.

487.— Latrines. Arriving on the site of a camp, one of the
first duties is to designate the places to attend to the calls of Na-
ture, and there dig latrines. Urinals should be placed nearer the
camp and of easy access.

The only exception to digging latrines is when the command
is very small, is certain to march the next day, and no other
troops are to follow.

488.— Latrines and urinals should be so placed as not to be in
the course of the prevailing winds to the camp, and must be so
situated that they cannot pollute the water, either directly or by
soakage.

489.— A small, shallow trench will suffice for a single night,
and should invariably be filled in the morning before marching.

For longer periods, a trench 2 or 3 ft. wide at top, from ^ to 10

266 Camping Expedients*

ft. (le€p, and 12 to 15 ft. long for every 100 men, should be dug,
throwing the earth to the rear, from which a layer of a few inches
should be thrown into the trench every day, or oftener if neces-
sary. Lime or charcoal may also be used to deodorize the
soil.

It is better to increase the number of trenches than to make
any one trench too long.

Shallow latrines should be discarded when filled within a foot
of the surface, and completely filled in with earth; deep ones when
within 3 or 4 ft. of the surface.

All latrines should be filled in and marked before marching.

490.— In temporary camps, latrines may be provided with seats
of a pole and a back, and be screened by bushes, canvas, or other
means. (Fig. 16.)

491.— Kitchens. On going into camp, kitchens should be
promptly established, and in the same relative positions as if the
camp were going to last a month or more. A pit should be dug
near by for strictly liquid refuse, while solid matter should be
placed in a box or barrel for the police party to remove.

492,— When fuel is plentiful, a trench of suflScient length and
about 1 ft. deep may be dug to contain the fire, over which the
kettles are hung from supports. (Pi. 59, Fig. 1.)

If fuel is scarce f then dig a trench as above in the direction of
the wind, but a little narrower than the diameter of the kettles to
be used. Place the kettles over the trench and fill in between
with stones, clay, etc., forming a kind of flue. The draft may be
increased by building a chimney of sods, stones, etc., on the lee-
ward end and enlarging the windward end. (Fig. 2.)

If the camp is to be for a long time and the direction of the
wind liable to vary, a number of such trenches may be dug
radiating from a common point, over which point a chimney is
constructed. Then, whatever the direction of the wind, the
trench opening in that direction can be used, the others being
closed.

The trenches should have a slight fall from the chimney back
for drainage, and a moans for the water to escape. If the ket-
tles are small or of various sizes, rests of stones, scraps of iron,
etc., may be placed across the trench.

A square hole may be dug for the fire with trenches for draught

PLATE 59.

FIG.1

FIG. 2. /?«/,.

Gfiilafm

Cktmping Expedients. 269

at the corners, the kettles being placed on rests over the fire.
(Fig. 3.)

403.— A grillage or kiiid of grate about 1 ft. high, made of gas-
pipe or bar-iron, is sometimes. used to set over the fire, and on this
are placed the kettles. (F'ig. 4.) These are sometimes made with
movable joints, so as to be closed for transportation.

494.— If a covered kitchen is desired, either a trench similar
to Fig. 2 can be dug, or one above ground can be built with stones
and sods and a tent placed over it, or a cover constructed.

495.— To bake bread, when none of the portable ovens of the
Commissary Department are carried, improvised ovens must be
constructed. The simplest method is to take a barrel with one
head out (one with iron hoops best), lay it on its side in a hollow
in the ground and then plaster over with wet clay 6 to 8 in. thick,
then with a layer of dry earth equally thick, leaving an opening
of 3 or 4 in. at the top of the closed end for a flue. The staves are
then burned out by a hot fire, which also bakes the clay covering,
forming an arched oven. To bake, after heating, the front and
flues are closed. Or a pit may be dug from 6 to 12 in. deep and 4
by 5 ft. for the hearth, over this form an arch with a hurdle or any
other material available (Fig. 7), with a chimney at one end and
a door at the other. Then plaster and cover the arch as in the
barrel oven and bake the clay covering.

496.— An oven may be excavated in a clay bank (Fig. 6) and
used at once.

497.— The Buzzacott Army Field Oven (Fig. 8), which is an ar-
ticle of issue by the Quartermaster's Department, is a complete
camp cooking outfit, consisting of oven, baking and frying pans,
etc. All are securely packed together and can be conveniently car-
ried in the feed box of an army wagon or on a pack animal. To
use it, a bed of live coals is first obtained, then the oven after being
heated is placed on rests over a bed of the coals, and a layer of
sand sprinkled evenly over the bottom of the oven to prevent
burning out. In this is placed the pans of prepared food on suit-
able rests and the whole covered with a hood. On the hood is
scattered a layer of live coals and burning brands. Broiling, fry-
ing, coffee-making, etc.. may be done on top of the oven by using
the remaining pans, rests, etc.. at the same time that the interior
Is used for baking.

270 Camping Expedients.

498.— Drainage. The camp being located, a system of sur-
face drainage should be carefully traced and constructed. As
soon as a tent is pitched it should be surrounded by a shallow
ditch outside, emptying into a company ditch. The proper meth-
od of doing this is to have the inner edge of the ditch came just
inside of the skirt wall of the tent to catch the water running
down the side of the tent and to drain the interior.

The picket should be inside of the ditch. (Fig. 9.) To bank
earth up against the tent soon rots the bottom of the wall.

499.— Beds. The ground being generally too damp to lie upon
directly, all should sleep upon some dry material, as straw, leaves,
or preferably a low platform constructed of small branches and
poles, if available. (Fig. 10.)

If required to sleep upon the ground, one will sleep more com-
fortably if he scrapes out a small hollow for his hips. Straw,
hay, etc., for sleeping upon may be made into mats with the Malay
Hitch as in Fig. 11.

500.— Windbreaks. When troops bivouac, some protection
from wind may be obtained by building up to the windward a
pile of earth, sods, etc. Where trees are available, by resting: a
pole on two forked sticks, 4 or 5 ft. high, against which branches,
thick end up, are T>ilpd at an angle of 45" on the windward side.
(Fig. 12.) Hurdles similarly placed, supported and covered (Fi^.
l.S), canvas or blankets secured as in Fig. 14, straw or hay clamped
between poles as in Fig. 15, may be used.

By throwing up either a half or whole circle of earth 18 ft. in
diameter, from a ditch on the outside, some protection may be
obtained. On the bank so formed additional windbreaks may be
placed or a covering extended over it all may be made. (PI. 60.
Figs. 1 and 2.)

501.— In cases of prolonged occupation, if tents are not avail-
able, the troops should build shelter of some kind.

Huts may be built of timber, logs, brushwood, adobe, etc., in
connection with straw, bark, sods and similar materials.

All huts should, if possible, have their floors raised above the
ground to allow free circulation of nlr UTiderneath. ^Fig. 3.) Only
in very dry soil and when not to be occupied lone: is It allowable
to sink them, if avoidable. Space between huts in the same row

PLATE 60.

-18-

Camping Expedients. 273

should equal the height of walls, and passage in rear equal the
height of ridge. Hut sites should be well pounded.

Huts are ordinarily constructed to contain a small number of
men, but the sizes and details of construction will depend greatly
upon the site and materials available.

A very fair minimum allowance per man of bed space is abotit
2.5 ft. X 7 ft. with a passage at foot from 2 to 4 ft.

Thus, the plan for 8 men may be taken at 10 ft. x 18 ft., ar-
ranged as in Fig. 4. For 12 men, 15 ft. x 18 ft. For 16 men, 20
ft. X 18 ft. For 20 men, 25 tt. x 18 ft.

For calculating the accommodation at the above rates, allow
1 man per pace of length for a single row of beds and 2 men per
pace of length for a double row of beds.

502.— Major Smart, Medical Department, recommends as best
a modification of the Army of the Potomac hut, of rectangular
plan (Fig. 5), 7 ft. x 13 ft., height to eaves 6 ft., to ridge 10 ft.; door
in middle of one long side, chimney opposite door on outside of
wall; on each side of doorway a double bunli. This hut to accom-
modate 4 men.

If logs are used, the ends arc trimmed with an axe where they
lap at the corners, so they will lie one upon the other throughout
their length.

503.— If made of small timber, some style, as in Fig. 6, with
thatched roof, might be used.

If, for any reason, it is not desirable to build huts as above,
forms may be used as shown in Fig. 7, or hurdles, as in Fig. 8.

504.- Sentry boxes may be made as in Fig. 9, the side cover-
ing consisting of watling described in Chap. IX. and the roof
thatched.

INDEX.

Par.
ABATIS, consists of, how

marte 50

In shallow ditch, of small
branch ea, in front of

glacis 51

how destroyed 46 »

ADVANCED POST, rear of... 204
ANCHORS, number of, scarc-

Uyof 343

snbstltntes tor 3>14

use of 342

weights of, names of parts

of 341

AN6L.i£, equal to a giv»)n
angle, method of laying

out 22

right, method of laying

out 18

re-entrant, salient, shoul-
der 82

APPROACHES, in siege oper-
ations . constructed by

infantry 154

AREA, of rectangle, of trapn-
zold,of triangle, method

of finding 25

ABTILLiCRY',^in defense of

village, ^here placed... 215

in woods 179

projectiles 9

to oe placed outside of

works 87, 151

AXE, use of 44

BALKS, bay, etc., defined... . 284

BALLAST, for R.R., object of 3.7
BANK, GUN, definition of,
relative advantages of,

and embrasures 70

dimensions of , where

placed 102

space required for 100

BARRICADE, use and con-
struction of 61

for doors of buildings 195

BATTERIES, telegraph, how

carried 418

BAY. length of, how found. . 317

BEDS, camp 499

Pat,

BERM, definition of , etc 65, 99

advantages and disadvan-

tagfsof 78

FINDING, fascines 117

BISECTING an angle, method

of 20

BLOCKS, description of, etc.,

running. 228

BLOCKHOUSE, use and con-
struction of 144

in isolated places 145

BOAT, buoyancy of, how

found 316

BOX or barrel to sling 223

ponton, construct ion of... 323

BRACKETS, telegraph 410

B t&E AK ING loads of ropes . . . 218
BREAKS in telegraph lines . 419
BRIDGE, anchored to haw-
ser 343

beams, of iron, how de-
stroyed 446

connection of with shore,

how made 360

computing strength of.. . 255

double lock '275

expedients 278

floating, descript on of 306

flying, description of 3u9

forming, by successive

pontons 346

forming, by pnrts 347

fonning, by rafts 348

forming, by conversion . . 349
masonry, how destroyed. .

440-441

maximum load f<»r 247

name of, how derived . . .248, 310

Paine's 260

pile 2«:9

protection of, from float-
ing objects 3.52

railroad, i-epair of 405

requirements of 244

short, how anchored 343

single lock 274

single sling 276

spar railroad 245

suspension 280-6

suspension, how destroyed 41

276

hidex.

Par,

BRIDGE— C^NTINUBD.

swing 351

trail 308

treble sling 27?

tweiity-flve feet or lp«*^. . . .258-9
twenty-flve feet or over .

261,271,276

BROADSIDE VILLAGE, how

defended 21^

BRUSH iiuts 608

sentry boxes 604

BRUSHWOOD, bundles of. va-
rieties and sizes 115

late and metbod of cle>tr*

Insr 46

roads 371

BUILDING, defense of . how
regarded, first line, how

far distant 191

doors of, how barricaded, 195

flank defense of 199

how used for defense 189

loophoiingof 194

materials used in defense

of 200

precautions In defense of. 19-

removal of 4!j, 438

requisite of, for defense . . 190
steps in preparing for de-
fense 193

windows of, how barri-
caded 197

BUOYANCY of caaks, how de-
termined 325

BUZZACOTT oven, descrip-
tion of 497

GABLE, charge of explosive

to cut 450

swinging, length of 309

OAMPBEDS 499

CAMPS, drainage 498

dry and healthy sites

for 457,459

selection of 465, 45*^, 4 2

unhenlthy sites for 458, 460

windbreaksfor 500

CANISTER, description of.. . 11

CANVAS PONTON,iJ. S

CANVAS RAFT, description

of 3'>3

CAPITAL of fleld works .... 82
CAPONIERS, objectionsto, 86, 14*5

stockade work used for 188

usert in flanking build-
ings 199

CAPSTAN, description of 242

improvised field 243a

CxVSEMENT, use and general

form of 138

how cons tructed , floor

space in 139

C.VSK, buoyancy of how de-
termined 325

CASKS, closed, piers of, con-
struction of 330

319

par
CASKS— Continued.

open, piers of, construe-

tionof .«8

open, safe load of 329

CENTRIFUGAL FORCE of

train 383

CHARCOAL, uses of 481

how made 482

CHARGES, several exploded

at same time 430

CHESS described 24g

CHEVAUX-DE-FRISE 66

CHOKER FASCINE, descrip-
tion and use of 117

OiRCULAR VILLAGE, how

defended 214

CLARIFICATION of water .. 476

CLAY R'lADS 367

COMMAND OF WORKS, deh-

nition of 71

COMMON TRENCH work,how

made, UHesof 156

COMMUNICATIONS, c o n -

struction of 373, 374

In woods 177

CONCENTRATED LOAD on

bridge 253

CONDUCTOR, metallic, for

telegraph , 408

CONNECTING WIRES, how

done 431

CORDUROY ROADS 370

COUNTER-SCARP. deflnHion,

etc 65, 79

gallei*ie» 85

COVER for guns 40 1

in woods, how obtained .. . 176

CRAB 240

CREST, exterior 87

interior 66

military 15:{

CRIB piers, construction of. . 2(i8

ponton, construction of... 322

CROSS, in telegr 'ph wires 419

CROSS ARMS, telegraph 410

CROSSING of rivers, selec-
tion of, how determined, 289

CROSSINGS, railroad 385

CROW'S FEET 6<5

CUTTING, how defended. . .171, 172

DEAD LOAD on bridges 253

DEBRIS, removal of 48

DEFENDERS of woods, num-
ber of 179

DEFENSE, of fences 168

passive, with respect to

lines of works 149

DEFILADE, definition of.... 88

in plan 89

in section 90, 9 1

with two planes 92

DEPTH of fords 290

DERRICK, description of . . . . 237

in using 24«

Index,

Par.
DESTROYING railroads, by

whom done 399 400

bv whom ordered 401

of telegraph lines 420

DETONATOU 4i9

wllhfuse 428

electrical 429

DIGGING wellH 470. 471, 472

DIMENSIONS of loopholes... IM

DISABLING railroads 398

DISTANCE between two In-
accessible polnt8.method

offindinflT 24

DISTRIBUTED load 2.W

DITCH 65,81,361

depth of * 96

method of dlgfflng V*\

DOORS, how barricaded. 1%

DOUBLE lock bridge 275

DBAI N8, catch and covered . . ?6l

DRAINAGE of camps 49B

of roads 361

DRINKING water 465-9

DRIVEN wells 47:^-4

DRIVING piles 270

DYNAMITE, use of with de-

tonator 428

EARTH, excess of at salients. 97
in embankments, space

occupied by 96

roads 366

EARTHWORKS, calculation

ofdlmensionjiof 95

FLECTRlOALfase 429

EMBANKMENT, how defend

ed 170

EMBARKATION, in ferrying 301

EMBRASURE 69

used when, details and

construction of 103

space required for JO**

ENGINE, locomotive 380

ENGINEERING, Military,

Field, definition of 1

EPAITLEMENT, gun 4()a 7o

relative advantage of, and

embrasures 70

EQUILATERAL TRIANGLE,

method of laying out 21

ESCAPE In telegraph lines.. 419

ESCARP 65. 79

EXPEDIENTS, bridare 278

EXPLODER, electrical 430

EXPLOSIVES, kind general-

1 V used 421

table of comparative

strength of 453

EXTENDING along zlg-ZRg.. 155

workinsT party 1()9, 110 155

EXTKNSION on flying sap,

method of 158

EYE-BARS, how cut 448

EYE-SPLICE, to make 222

211

Par.

FACES of works

FARMS, principles of defense

applied to 203

FASCINES. siz(^. weight, and

making of 117

FASTENINGS, rwil 882

FAULTS ill telegraph lines. 419-20

FENCES, defense of. 168

removal of when 48

FERRY , the rope 307

F1i:rryiN6 by boat, embark-

ation. ana unloading 301

by raft -. :J02

FIELD GUNot, destruction of 451

range of 13

FIELD LEVEL. decrlptiOD of 26

FILTERS, portable 483-4

simple 485

FILTERING water. 480-1

FIRE, as regards direction,

trajectory 8

double tier of, for walls ... 167

sector of, discusnion of 86

working parties exposed

to Ill

FLANK defens«> of buildings 1^9

FLANKS of works 8*2

FLOOR space in casemates. . . 139
FLOATING piers, essentials

of 314

FLYING BRIDGES, raft for. . MO

telegraph lines 418

sap, dCHCriptlon of 157

sap. method of extension

along 158

FORDS, how made impassa-
ble .58

with sandy bottom 291

depth of, i<equislte of 290

in mouniainous country. . 291

level country 291

how marked, position of,

how determined 293

precautions in selecting. . 296

re-examinations of 296

where found 292

FO REM ROUND, extent of

clearing 43

FORM, strap iron gabion 120

wicker gabion 118

of I'oads 359

FORMING BRIDGE by con-
version 349

by parts 347

by rafts 348

by successive pontons ... 346

FORTS, how difltlnguJshPd... 84
FORT WAGNER, parallels

and approaches to 160

FORTIFICATION, classes of. 2
compared to other milita-
ry expedients 7

obfect of

subdivision of field 3

FOUGASSE.construction.nse

and charge for 59

278

Index,

Par.
F RAISES, construction nnd

use of 55

FROGS ^•. 384

rftilroad, how debtroyed. . 444

FUSE 427

how used • • 428

GABI< »NS, fioopor si rap iron,

weight and maklMg of,.. 120

method of carrying 157

sheet iron, ma king of 121

wicker, size, weight, and

luakingof 118

making of wittiout a gabi-
on form 119

GATES, destruction of 437

GIN, description of 2:«

using 240

lashing, making of 227

GLACIS 65.80

GORGE of works 82

GRADI E NT, limiting of I o.ds 3%

GRAIN, removal of standing. 47

GRASS, removal of si Ending. 47

GRWEL ROADS 368

GRILLAGE 493

G<\UGE of railroads :«0

GUARDING water supply. ... 464

GUN-Ct»TTON 422

how detonH ted 4i8

GUN EPAULEMENTS » nd

pits 40 I

GUNPOWDER, how ignited. 4^

used H 8 an explosive 424

GUTTERS aei

HARD WATER 477
HASTY DEMOLITION, la-
hies showing charges

for 452

HEAD LOGS, use of 40

HEALTHY CAMPS 4/>7, 4*

HEDGES, advani geisof. how

derived, principles of . . . 169

removed, when 48

HEIGH rS over which Are

may be delivered is

HITCH ES, knots, etc 219

HOLDITASTs, description of. . 243
HOOPS, making of, for strap

iron gabions 120

WORSE, power of on gr tides. . 356

HOUSE!=^, demoliiion of 438

HURDLES, continuous, con-
struction of 123

size, weight and making of 122

HUTS, brush 503

how made, etc 501

Army of Potomac (Ms^jor

Smart's) 502

allowance of space in 601

of, how in-

ICE

thickness

c eased.

thickness of for variouu

loads

INFANTRY APPROACHES

in siege operaiiuns

INTERVALS between trencn-

method of taking bv, work-
ing parties

usual for working par-
ties... Ill

INSULATORS, telegraph

INSULATED WIRE J<ilN18
INTRENCHMENTS, HASTY,
advantages and disad-
vantages of

concealment of

conditions to be falfiUed

consist of

for men standing

for skirmishers lying

for two ranks kneeling...
for supports and reserves.

intervals in line of

I'^olated-

location of depends upon .

on slopes

IRON PLATES, how cut

ISOLATED PITS

297

299

298

154

100

, 112
41i
4:1

;s8

2S
28
31
28
30
33
36
32
35
34
44'i
.2

JOINTS for telegrsiph wire... 417

American twit*t 4i7

insulation of 431

rail 881

JUNCTIONS, railroad 386

KING POST TRUSS 272

KITCHENS 491-2

covered 494

KNOTS, hitcl-es, etc 219

LANCES, militnry, telegraph. 418

LASHI NG8. gin ..... 227

rack 224

shear 226

t.ran»*om 22 »

LATRINES 487,490

LEAKS in telegraph line 419

LEVEL, Held, description of. 26

uses of 27

LINES, cuitingof ditch and

trench lOl

LINK, first, falling back past

bouses 192

parallel to given line,

method of constructing. 23
LINES, second and third in

woods 168

Par.
LOAD, distributed, dead, and

moving 253

LOADING HORSES In lail-

i"oad cars 393, 394

LOADING WAGONS on rail-
road cars 396

LOG, cubic contents olf 254, 335

buoyancy of 334

LOGS, pi rs of, construction

of ....' 338

LONG SPLICE, to mske 221

LOOPHOLES, dimensions of 164
height of, how Influenced. 166

how made 40

In buildings 194

LOOPHOLING WALLS 163

method of 164,166

MACADAM ROADS 364

MACHICOULIS gallery, con-
st rnctlon of; use of 199

MAGAZINE, general plan

of 141,142

large, small In parapet — 140
of gabions and fascines. . . 143
rifle, range, speed, and

flreof 14

MAGNETO EXPLODEit 430

MARKING FORDS 293

MATERIALS for bridges. .. . 287

for road coverings 365

revetting 114

used in defense of build-
ings

MAXIMUM LOAD for bridge
MERLON, definition of, rule

as to minimum length of iu4

METAL TIES 379

MILITARY ENGINEERS.du-

ties of 421

MILI I'ARY TELEGRAPH

lines 418

MINES, land.

MOVING or LIVE LOADS. . .

OBJECTS, floating, pi-otec-

tion of bridge from

OBSTACLES, conditions gov-

erninguseof

OFFICE TELEGRAPH,tieat.

ment of when captured .

OVENS 495-6

Buzza/'Ott... 497

ORGANIZATIONS, or parts

Of, used as working par-

■ ties 42

OVERHAUL TACKLE 231

PAINE'S BRIDGE 260

PALISADES, consist of 54

PALISADING, destruction of 435

PAIRING 118

Index, -^79

Par,

PANCOUPE 102

PARADOS, definition of 68

method of determining

height of 93

PARALLEL to a given line,

metho'l of construciing. 23
PARALLELS and approaches.

Fort Wagner 160

PARAPET 63.67,81

PERPENDICULAR to a line

method of erecting 19

PICKETS, forked 119

gabion Ho

PIERS, bridge, how de-

stroyed.. 440,449

floating, essentials of 314

of casks, piecautions in

using ;... 327

of open boats, precautions

inuslng 316

of open CMSk<«, construe-

tion of 328

of closed casks, construe

tion of 330,333

of logs, con SI met ion of .338, 339

PILEBRIDGES 269

driving 270

PLANK ROADS 872

PLANKS, when used for re-

vetments

PLOWS, use of

PONTON CAN VA-,U. S

crib, construction of

PONT«»N, box, construction

reserve train, U. S

wagon body, construction

P^jLES, telegraph, how num-
bered 415

telegraph, how guyed,
number to mlle,prepaia-
tlon of, protection from
lightning, raising of,

size of, where run 409, 411

PORTABLERAMP 393

fllters 483,484

truss 279

POSITION, defensive, defini-
tion of, chief requisite

of 4

choice of 42

strength of 153

conditions to be fulfilled.. 4

of ford, how determined . . 293

POWER of horse on slopes.. . 356

exerted by man 236

of tackle 233-5

PRECAUTIONS, additional.

in defending buildings.. 198

in fording 295

rR< »F I LES, angle, how deter-
mined 94

d«*finition and nomencla-
ture of. 65

normal, of field works 99

200
247

60
253

352
49

420

124

319

323
320

324

280

Index.

Par.

PROFI LIMG, method of 94

PULLEY, description of 228

QUKKN-POST TRUSS 273

RAOK, fasoine, deseription

and use of 117

lashinfctotnake 224

RAFT, CMUvas, description of, 308

for trail bridge 308

of skins 304

RAFTS, advantages and dis-

advantagf^s of 305

for flying oridge 340

swinging, for iraffio 351

RAIL FASTEN I NQS 382

form of 380

joints :«l

how cnt 4«>

straightening 407

RAILROAD, bridge 245

crossings 385

junction 386

wye 387

turntable 388

RAILROADS, duties of troops

in connection with 375

description of 377

destroying and disabling,

by whom done 398-400

how disabled and des-
troyed 402, 408

repair of 404

rolling stock, buildings,

etc 390, 391

RAMP, portable 393

Major Fechet's 397

senii-permunc'nt 395

simple form of 392

RAND1N(4 122

RKDOUBTS 84

KELIKFS, l8t, 2nd and 3rd of
working party, cutting

11 nes for tasks of 101

of field work, dnfluitlnn of 72

RESERVE TRAIN, ponton,

U. S 320

REVETMENT, definition of 113
making and qualities of

adobe 137

of biniRhwood 128

of faHcines 129

ofgabion 130

of nurdle and continuous

hurdle 131

ofpisa 136

of plank 124, 132

of posts 135

of sand bag... 133

of sod 126. 133

of timber 125, 132

RIBBANDS 55

ROAD-BED 360

defense of 173

materials 366

Par.

ROADS, brushwood 371

clay 367

corduroy 37o

desirable conditions In 3'4

drainage of 361

earth 366

form of 359

gravel 368

knowledge of 353

limiting gradients of 355

plank 372

repair of 369

surface of 362

width of 358

ROADWAY, weight of, steadi-
ness of 313

width Of on bridges. . .248. 280-6

ROPE, breaking loads of,

weight of 218

compoHition. size of, etc . . 216

ROPE, parts of 219,230

rule tor strength of 217

ROUND TIMBER, strengthof, 255

RUNNING BLOCKS 228

SAG in telegraph wire 414

SALIENT village, how de-
fended 212

SAND-BAGS, materials, size,

capacity, and filling 127

SAP, flying, description of.. 157

SAW, leeth of 44

use of 44

SECTOR OF FIRE, deflnition
of and application to dif-
ferent traces 86

SELECTING CAMPS 456-6, 462

SENTRY BOXES 504

SEWING, method of, for gabi-
ons and hurdles 1*8

SHEAR LASHINGS 226

SHEARS, description of 238

method of using 240

SHifiLL 9

charges, tiow exploded 12

shrapnel 10

SHORT SPLICE, to make 220

SUOVI£LERS, extra, provid-
ed when 101

SIDINGS, railroad 384

SING LE LOG K BRI DG E. 274

SINGLE SLING BRIDGE 276

SITE for floating bridge, selec-
tion of 311

plane of. definition 73

SIZE OF TELEGRAPH

WIRE 408

SLEWING 122

SLOPE, banquette 65

description of 17

exterior 65, 77

interior 65, 75

superior 65, 76

SMALL PITS, how made 57

how destroyed. 453

Iftdex.

281

Par.

SNATOHBLOOK 228

SODS for reTeim^nU. enttlag

and layini: 126

S PAN, superstructu re, string-
el's or balks, side rails,

etc 248

SPANS. 25-ft. or less 258, 259

25-lt. or over 261, 271, 276

SPA BS. ari-anif erne q t of 257

8PLI0E, long 221

eve. 222
SPLINTER PROOF for tren-
ches 35

STOCKADE, advantages of,

definition of 180

how destroyed 436

kind of timber preferable

for 186

loopholes in 1^4

loopholes, when cut in 185

of vertical timbers 182

of same, square and round

timbers. 183

of horizontal timber 187

STOCKADE, of k.r. iron, de-
stroyed how 436

when employed 181

work used for tambours

and caponiers 188

STRAIGHTENING KAILS. .. 407
STREAMS, unfordable. how

passed 294

velocity of, how deter-
mined 296

width of, how determineci, 312

STRENGTH OF Materials 249

of rope 217, 218

SOB-DRAINS :^1

SUSPENSION BRIDGES '280-6

S WITCH, split and stub 384

TABLE of breaking loads ... 218

of constant "O" 253

of weight 8 of materials 256

showing amonntsof revet-
ting materials for 100

linear feetof revetment, 137

T Af^'K L E , d escrl ption of '229

formula for power of 235

power of 23:^4

to prevent twisting 232

toi'ound in, tooverbaul... 231

TAMBOUR 147

stockade work used for. . . 188

used in flanking buildin-«n. 199

TASKS (PI. 14, 16) 111, 112

laying out of 101

in constructing parallels

and approaches PI . 22

responsibility for comple-
tion of 106

TELEGRAPH MESSAGES.. . . 408

lines, how destroyed 4'20

TELEPHONE, outpost cart

for 418

Par.

TELFOKD ROAI>S 363

TKRREPLEIN 74

THICKNESS of materials

proof against small arms, 15

TIES, metal 379

wood 378

TIMBER BRIDGE, how de

stroyed 433

felled, removal of 45

kinds preferable for stock-
ade 186

round for reveiroenta 125

standing, removal of 43, 44

TOOLS, carrying of by work-
ing parties 108

cutting, intrenching used

in the field 41

taking of, by working par-

.tles 107

used in felling tember. ... 44

TORPEDO, U. 8. bridge 433

TORPEDOES, automatic 454

TRACE, definition of 64

selection of 89

TRANSOM, strength of 280

TRAVEKSE. deflniilonof 68

method of dftermlning

height of 93

TREAD BANQUETTE 65

TREBLE SLING BRIDGE... 277

TREE INSULATOR and tie. 415

TRKE!^, cutting of 44,45

how to fell with explosives, 432

TRKNCH 65

common. uses of, how made, 156

dralnageof 98

method of digging 101

TRENCHES, advantages and

disadvantages of 39

conditions to be fulfilled

by 28

disguising location of 38

intervals In line of ;%

kneeling or sitting 30

location of :i5

lying '29

standing 31

TROOPS, weight of on bridge, 252

TRESTLES, capped 264

tie block 263

two-legged 265

three-legged 266

four-legged « . 267

six-legged 262

TRUSS, king- post 272

queen-post 273

portable 279

TUNNELS, how destroyed. . . . 442

repair of 406

TURNTABLES, railroad 388

UNLOADING in ferrying.... 301
horses from R. R. cars. .393, 394
wagons from cars 396

URINALS 488, 489

282

Index,

Par.
VELOCITY of Rtreams, how

detf ruiined 296

VILLAGE, advantages and
disadvantages of for de-
fense 206

artilleryt whei*e placed in

defence of. 215

broadside, how defended.. 21.3
clrculnr, how d»fended.... 214
cover for supports and re-
serves in 215

in defense of, precautions

necessary 205

defense of depends on . . . 208
arrangements for defense

of 205

garrison of, how deter-
mined 211

objf cts in holding 207

salient, how defended 212

value of. for defense 2(>5

arrangement for defense
of, how made 210

WAGON BODY PONTON, con-
struction of 324

WAGuNS, prepared for cross-
ing ou ice 299

WALL8, for double tiers of

fire 167

discussion of as niilitaiy

expedients 161

loopboling 163-5

preparation of for defense 1(52

removal of 48

how destroyed 439

WATER, clarification of 476

drinking 465-9

filtering 480-1

guarding 464

necessity of and amount

required 463-4

WATKR TABLES on roads... 361

WATLING IIH

WKEDS. removal of 47

WEIGHT of materials. 256

of rope 218

of troops on bridge 252

WELLS, digging of 470-2

driven 47:^4

WIDTH OF SOADS . :«8

WINCH 240

WINDLASS, description of.. 241
WINDBREAKS, for oamps.... 5(iO
WINDOWS of buildings, how

barricaded 197

Par

WIRK, connection of 431

entanglements, high, low,

how made 52, 53

entnnglements, how de-
stroyed 454

bow 8tret<hed, hanging

of, secured to 414

how strung across roads.. . 411
how strung across streams 415

telegraph 4<»8

tie 413

WITHES, making and use of 117

WO« IDS, artillery in. 179

communications in 177

cover in 176

lying beyond position 175

numberof defenders of... 179

preparation of ed^e of 174

2d Hnd 3d lines in 178

WORKS, constructed by

troops to o<*cupy 5

double line of 150

fixed types of necessary. . . 6
groups of, intermediate,

wh^n used 149

line of 148

advantages and principles

of 149

WORKS, field, conditions to

befulfiiled 62

calculation of cross sec-

i Ion of 95

claHslficatlon as lotrace.. 83

defilade of 88. 89. 90, 91, 92

details of construction of

99. HO, 101

length of crest foi as-
sumed gsrrlson 100

open, closed, and half
closed, definitions, ad-
vantages, and disadvan-
tages 83

continuous line of, crem-
aillere, blunted redan,
redan with curtains. t<\-
naille. tenaille and re-
dan, trace of 152

WORKING parlies, extension

of 109. 110

organization of 105

when under fire Ill

WYE, R.R 387

ZIG-ZAG, direction of, length

of 159

extending along 155

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Military Publications.

0B0ANIZ4T10X AND TACTIC*. By Lieut-Colonel Arthur L.

Wat<iier, Assistant AdJiiCatit-General, U. S. Army; late

lii'^traotor In tbe Art of War at theCJ.S. Infantry and

Oavalry School.

ThiH book has been offlctally adopted as a text- book In the
U. S. Knffineer School, at WlUet's Point, the U. S. Artillery
School, at Fort Monro*;. theU. S. Infantry and Cavalry School,
at Fort Leavenworth, and the U. 8. Cavalry and L»j?iit Artil-
lery School, at Fort Blley. It has also been ot^cLally recom-
mended by the War Department /or the use of officers in preparing
for examination for promotion.

One volunve, 8vo, 514 pages, handsomely bound in blue
cloth. (Bound in sheep 75c extra.) Sent postpaid on re-
ceipt of $3.00.

THE SEfiYICE OF SECURITY ANI> INF0BM4TI0N. Revised, En.
larged, and with New Illustrations. By Lieut-Oolonel
Arthur L. Wagner, Assistant Adjutant-General, U. 8.
Army ; late instructor in Art of War at the U. S. Infantry
and Cavalry School, Fort Leavenworth, Kansas.
This book has been officially ado. .ted by the War Depart-
ment as a standard in the examinailon of officers oi the
Hegular Army for promotion. It has also been officially
a<lopted as a text-bo "^k in th«^ U. S Artillery Schoof, Fort
Monroe; the U. S. Infantry and avalry School, Fort Leav-
enworth ; the U. S. Oavalry and Light Artillery School, Fort
Riley.

8vo, 265 pages. Sent postpaid on receipt of $1.50.

A CATECHISM OF OUTIOST DUTY. Including Advance Guard,
Bear (^uard, and Reconnaissance. By Lieut .-Colonel Ar-
thur L. Wagner, Assistant Adjutant-General, • . s. Army,
late Instructor in Art of War at the U.S. Infantry and
Cavalry School, Fort Leavenworth, Kansas.
This book Is a careful abridgment, in the form of ques-
tions and answers, of Lieut. Colonel Wagner's "Service of
Security and Information,'' which has been officially sanc-
tioned by the W'lr Department as a standard in the examination
of officers of the Regular Army for promotion.

One volume 16mo, cloth, ten illustrative diagrams. Sent
postpaid on receipt of 50 cts.

MILITARY MAP.RKADING, FIELD, OUTPOnT AND ROAD SKETCH-
IN^, by Captain w. D. Beach, Instructor in Military To-
pography at the U. S. Infantry and Cavalry School. 124
pages, full cloth, 76c.

Hudson-Kimberly Publishing Co.

1014-1016 Wyandotte St., Kansas City, Mo-

Military Publications

EXQLISH-KPANISH POCKET HANITAIi. This Manual is prepared
Lieat. U. G Hill. 20th Infantry, " - ' - ■ ^^
, 80 pages, blue cloth, price, 75c.

bv Lieat. U. G Hill. 20th Infantry, U. 8. A. Vest-p jcket
size, r * ■ ' "

JOXININ LIFE OF NiPOLEON has heretofore been presented
in English only in very costly e^litions; but the edition
announced herewith will be sold at the reasonable p ice
of 912.00. This edition is not storeotypci. but is printed
from new, clear type, and the edition is limited.

HAIiUAL FOB CYCLI8TS, by Captain Howard A Giddings,
Brigade Signal Officer, • onnecticut National Guard.
Author of "Instructions in Military Signaling/* New
Cyclist Drill Begultttions, combined with practical In-
structions for milit»»i*y cyclists, based on extended ex-
peri>i>ents in this country and abro id. A comoendium of
valuable information for soldiers using the bicycle. Full
blue cloth, illustrated. 96 pages, price, 75c.

HOBSES, SADDLES AND BBIDLES, by McJ>r William H. Carter
Ass. Adjt.-Gen.. U. R A. Ihis book has been officially
adopted by the War Department as a standard in the ex-
amination of officers of the Begular Army for promotion.
In the future this publication will be on sale through the
Hudson- Kim berly Publishing Co., Kansas City, Mo. Full
cloth, 368 pages, illustrated, price, J2.75.

PBIYATES' HANDBOOK OF MILITARY COUBTEST AND ACABD
DUTY, being paiatrraphs fi-om authorized manualb with
changes in manual of arms, salutine, etc., according to re>
cent modifications, and their adaptations to the Springfield,
arm, embodied, and notes. By Lieut. Melvln w. Kowell,
United States Army. Sometime Instructor in Guard Duty
and Military Courtesy, Division, National Guard of New
Jersey. Price, tag- board cover, 25c ; blue cloth, 50c.

CATECHISHAL EDITION OF THE INFANTBY DBILL REGULA-
TIONS UNITED STATES ABHY. Extended Order. General
I'rinciples; Leading the Squad; The Squad; ThePl%toon;
The Company; The Battalion; The liegiment; The Brigade
in Battle. Prepared by Major Wm. F. Spurgln, 28d In-
fantry. Price, tag-board co ver, 25c ; blue cloth, 50c.

Hudson-Kimberly Publishing Co.

1014-1016 Wyandotte St., Kansas City, Mo.

Military Publications.

DICKllA!f*R FIELD HOLDER, with blanics for Road and Posi-
tion Sketching on Fi*actice Marches, Advance and Rear
Gnard Duty, Outposts, Beiay Lines, and with Instrnc-
tioiis for the Men in the Duties of Orderlies and Mesaea-
gers. Price, 75c; additional Books or Flilers, 26c

THE CONDUCT OF WAR. By Lient.-General von der Goltz,
Prusdlan Army. Full blue cloth, $2.00.

MANUAL OF MILITARY FIELD ENQINEERLNG, for the use of Offi-
cers and Troopa of the Line. Prepared at the U. S. infan-
try and OavaliT School by the Department of Engineer-
ing. Captain Win. D. Beach, Third Oavalry, Instructor.
Price, $1.76.

MILITARY TOPOGRAPHY AND SKETCHING, a Revised Edition,
prepared for the Use of the Department of Engineer-
ing, United States Infantry and Oaralry School of Fort
Leavenworth, by Lieut. Ifidwin A Root. 280 pages, full
cloth, $2.50.

THE WAR GAME SIMPLIFIED, after the method of General
Verdy du Vernois. Designed for the use of beginners as
well an advanced study of the Military Art. Published
with full-stzed Msps and complete apparatus for conduct-
ing an exercise of the Three Arms Combined. The trans-
lation and arrangement are the work of Captain £ben
Swift, Fifth Cavalry, formerly in charge of the conduct
of the War Game at the United States Infantry and
Cavalry School. Price, $5.00.

A FIELD MESSAGE-BOOK, for the use of Signalists and Army
Officers in the tleld. Designed by Major Howard A. Gid-
dings. Brigade Signal Officer Connecticut National
Guard. Cipher disk, pencil, blanks, ti ansfer sheets, and
filing pxikrtts, all in a compact water.proof cover. Com-
plete, 75 blanks in pad, compressed-lead pencil. Sent post-
paid to any address upon receipt of price, f 1 00. ffxtra
p ids, 25 ceiits.

INFANTRY FIRE; ITS USE IN BATTLE, by Jos. B. Batchelor. Jr..
First Lieutenant Twenty fourth United States Infantry.
Handsomely bound in leather and complete with tables
and 11 lustrations. Sent post-paid upon receipt of price,

$2.00.

Hudson-Kimberly Publishing Co

1014-1016 Wyandotte St., Kansas City, Mo

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