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fu-^x-^t-,^ X^' u.-i-W.j 7^Jti^xX^/^o^-/S?{
MAHAN'S
PERMANENT FORTIFICATIONS.
REVISED AND ENLARGED
BY
JAMES MEEOUR,
PBOFESSOB OF CIVIL AND MILITABY ENGINEEBING^
Unitbd States Militabt acadbmt.
8BC0ND EDITION.
SECOND THOUSAND.
NEW YORK:
JOHN WILEY & SONS.
London: CHAPMAN & HALL, Limited.
1898.
Copyright, 1887,
By John Wilbt & Sox&
BOBBBT DBUMXOirD, BLBCfTBOTTPKB AMD PRIIITBB, NEW TOBS.
I
t
PREFACE.
^ In revifidng this work for the use of the cadets at the Mill*
^ tary Academy, it has been my object to retain the arrange-
<v) ment and so far as practicable the identical language of the
original text. I am prompted to this not only by an affec-
tionate respect for my former instructor, but more espec-
ially by a wish to give the cadets an opportunity to profit
by Professor Mahan's clear, concise, and comprehensive
statements, which are the result of the native ability, the
education, started in America, continued in France under
Gen. Noizet, and completed by a life-long study ; and the
rare experience gained in over forty years' service as Assist-
ant-professor and Professor at the Military Academy.
The parts omitted and the new matter introduced have
been selected with a view to rejecting only that which has
become obsolete through the introduction of improved
weapons and methods, and to explaining and illustrating the
new features developed from the same causes.
In making these selections it has seemed better to omit
f the details of the Bastioned system as worked out by Noizet,
^ notwithstanding its value as a problem in fortification-draw-
«^ iDg, and to replace it by fuller treatment of detached works
sea-coast defence, and constructions in iron and steel as used
at the present day.
My thanks are due to lieut 6. J. Fiebeger, Corps of En-
gineers, for translations from the German, and for collecting
the information contained in Appendix II.; and to Lient.
* Geo. W. Goethals, Corps of Engineers, for compiliuj?
5 Appendix I.
ij West Ponrr, N. Y., March. 1887.
* > * ' ' k"
CONTENTS.
CHAPTER I.
Fkeliminasy Cokbidbrations and Component Elements of Pbb-
MANBNT Defences.
▲BT.
I. PRELIMINARY CONaWERATIONS,
1-4. Permanent fortification : its object and means of at-
tainment, ...... . •
P10B
n. GENERAL PROFILE.
5-7 Description and analysis of the general profile,
8. Description of modem profile,
9. Command,
10. Description and discussion of scarps, .
11. " " " counterscarps,
12. '* " " ditches, .
13. " " " face covers, .
14. General remarks on general profile.
5
5
6
9
10
11
Id
ni. OPEN DEFENCES.
15. Classes of open defences,
16. Loop-holed walls, .
17. Exterior corridors,
18. Barbette batteries, .
19. Embrasure batteries,
20. Machicoulis defences.
13
13
15
15
16
16
IV. COVERED DEFENCES.
21. Detached scarp walls,
22. Semi-detached scarp walls,
23. Scarp galleries,
24. Counterscarp galleries, .
25. Bastionnets, .
25a. General remarks on covered defences,
26. Caponni^re defences for the enceinte ditch,
27. Casemates on land fronts.
17
IS
18
20
21
21
22
24
\
Tl CONTENTS.
▲BT. PAOK
28. Mortar casemates, 25
29. Casemates for water fronts, 26
80. Turrets, 27
81. Embrasures of casemates, 27
82. Bomb-proof buildings, 28
S3. Powder magazines, 29
V. COMMUNICATIONS.
84. General remarks on communications, .... 80
85. Particular conditions that communications should sat-
isfy, 30
86. Ramps, 81
37. Stairs, 32
88. Posterns, 82
89. Gateway, 33
40. Portcullis and other defences of gateway, . . .33
VI. ENCEINTES.
41. Classes of enceintes, 35
42. Systems and methods of fortification, .... 35
43. General remarks upon systems of fortification, . . 36
Vn. OUTWORKS.
4Au General remarks on outworks, 86
45. General conditions outworks should satisfy, ... 87
46. Classes of outworks, 88
47. Covered way, 38
48. Places of arms, 88
49. Traverses, 88
50. Tenaille, 39
51. Demi-lune, 39
52. Counterguard, 39
53. Redoubts, 40
54. Tenaillon 40
55. Horn work, 40
66. Crown work, 40
Vni. ADVANCED AND DETACHED WORKS,
SH, 58. Advanced works : definition and discussion, . . 40
59. Detached works : " " " . . 41
IX. INTERIOR RETRENCHMENTS.
<60, 61. Interior retrenchments : description and discussion, . 42
62. Cavaliers: " an .43
CHAPTER II.
Systems of Fortification.
62a. General considerations, . . * . . . 44
CONTENTS. Vll
I. BASTIONED SYSTEM.
ART. PAQB
68. Description and analysis of the bastioned system, . 44
64. Principal objections to the bastioned system, . . 45
II. METHODS OF VAUBAN.
65-75. Description of Vauban's First Method, ... 46
76. Analysis ** *' an ... 49
III. CORMONTAIGNES METHOD.
77-79. Development of method and principles applied, . 51
80-88. Description of Cormontaigne's Method, ... 52
89. Analysis of Cormoutaigne's Method, .... 56
90-94. Use of the counterguard by Vauban, Cormontaigne,
Coehoorn, Carnot, Haxo, and Noizet, ... 57
IV. METHOD OF THE SCHOOLS OF MEZIERES AND METZ.
95-98. Development of the method, 58
V. NOIZETS METHOD.
99-104. Description of Noizet's Method, 59
106. General remarks upon and objections to Noizet's
Method 61
107. Modifications adopted or suggested, .... 61
108. Considerations determining the method to be selected, 62
VI. CHOUMARA'S METHOD.
109. Principles upon which it is based, .... 62
110-119. Description of Choumara's Method, .... 64
120-122. Remarks upon Choumara's Method, .... 68
CHAPTER III.
Tekaillbd System.
128. Description and analysis of the system, ... 70
CHAPTER IV.
Polygonal System.
I. POLYGONAL SYSTEM IN GENERAL.
124. Polygonal system : description and analysis, . . 71
II. MONTALEMBERTS METHOD.
125. Development of and principles involved in Montalem-
bert's Method, 72
126-128. Description of Montalembert's Method, ... 73
129. Modifications introduced by Gen. Brialmont, . . 74
180. Polygonal system exemplified by the defences of Ant-
werp, 74
YUl
CONTBKTa
CHAPTER V.
Existing German Fortifications.
I. RECENT GERMAN FORTIFICATIONS,
ART.
131. System adopted, 77
132. General conditions imposed, 77
133. Independent works, 78
134. Defensive barracks, 78
135. Profiles of unmodified works, 7^
136. Casemates, 7^
137. Posterns, 7^
138. Mines, 7»
139. Powder magazines, guard-rooms, store-rooms, etc., . 7d
140. Revetments, scarps, and counterscarps, ... 79
141. Casemates for cannon and mortars, .... 80
142. Casemated traverses, 82
143. Caponni^res for enceinte ditch, 82-
144. Bastionets for ditch defence, 83-
145. Details of defensive barracks, 83^
146. Remarks upon German fortifications, .... 84
147. Changes required to fit these works to modem re-
quirements, 85
n. FRONTS OF POSEN.
148-151. Outline description of front, 86-
III. FORT ALEXANDER AT COBLENTZ.
152-168. Description of Fort Alexander, 88-
159-162. Remarks upon the polygonal system as applied by
the Germans, with analysis of the relative advan-
tages and defects of the polygonal and bastioned
systems, 90
163. Recent modifications in the bastioned and polygonal
systems, 93-
164. Considerations determining the character of future
fortifications and systems to be adopted, . . 9^
CHAPTER VI.
Detached Forts.
165. Now the main line of defence, 9^,
166. Trace adopted; dimensions; garrison; armament;
profiles and revetments, 94
167. Bomb-proof covers and use of turrets, .... 95
168. Communications, 95
169. Small but important works entirely bomb-proof, . . 96
170. Outworks 99
171. Glacis or wing batteries, 9^
172. Intermediate works, 9&
COIfTENTS.
IX
CHAPTER VII.
Influbncb of Ibrboxjlarities of Site on the Forms and Com-
binations OF THE Elements of Permanent Works.
ART.
173-175. General conditions to be satisfied,
176. Conditions of command, . . . . ,
177, 178. Rule to be observed in adaptation of plan to site,
179. Remarks upon foregoing subjects.
PAGB
97
9»
9a
lOO
t(
n. DEFILEMENT OF PERMANENT WORKS.
180. Remarks upon defilement of permanent works,
181, Data for the
18^185. Limits of defilement, ....
186, Dangerous zones of the site, .
187, Portions of zones that may be disregarded,
188, Defilement of masonry, ....
189, Limits of defilement for small works, .
190, Front and lateral limits,
191, Remarks,
101
10^
loa
104
104
104
104
104
105
III. PROBLEMS OF DEFILEMENT.
192. Cases of defilement, 105
193. Front defilement of a redan, the command being
given, 106
194. Reverse defilement of a redan, 108
195. Position of traverse for reverse defilement, . . . lOd
196. Forms and arrangement of traverses, .... 10&
197. Combinations of several traverses, . . . .10^
198. Precautions to be taken in locating traverses, . . 110
199. Remarks upon defilement by traverses, . . . 110
200. General case of the defilement of a bastion, . . . 110
201. Defilement of retired from advanced works, . . 112
202. Defilement by parados and conclusions drawn from
experiments, 11^
203. General remarks upon defilement— Recapitulation, . 113-
CHAPTER VIII.
Accessory Means of Defence.
I. WATER AS AN ACCESSORY.
204,205. Marshy sites, 115
206. Artificial inundations, 115
207. Water applied as an active means of defence, . . 116
n. OTHER MATERIALS AS ACCESSORIES.
208. Natural and artificial beds of rock as an accessory, . lift
209. Stumps of trees as an obstruction, 117
210. " Obstacles" as an accessory, 117
CONTENTS,
in. MINEa AS ACCESSORIES,
ART. PAGB
211. (General considerations in their use, . • • • 117
CHAPTER IX.
Sea-coast Defence.
I. BATTERIES ON LAND,
212. General conditions of sea-coast defence, . , . 118
213. Use of stone casemates abandoned, . . . .118
214-217. Earthen batteries, 118
218-221. Disappearing gun carriages, 119
222-324. Use of traverses, 120
225. Gun pits, 120
220,227. Mortar batteries, 120
228. Batteries on elevated sites, 121
229,280. The use of armor, 121
II. FLOATING BATTERIES.
231. Conditions requiring their use, 121
in. OBSTACLES, SUBMARINE MINES, AND TORPEDOES.
232. Their use a necessitjr in the defence of harbors, . . 122
238. General considerations to be fulfilled by passive ob-
stacles, 122
284. Different kinds of passive obstacles, .... 122
285. First use of submarine mines and torpedoes, . . 128
230. General conditions to be fulfilled by submarine
mines, 128
237-289. Uses of submarine mines and torpedoes, . . . 123
240-244. Classification and general description of submarine
mines, 124
245. Conditions to be fulfilled by the electrical system, . 125
246, 247. Construction of mine cases, 125
248. Explosives used, 125
249. Movable torpedoes, general description, . . . 125
250. Destructive range oi submarine explosions, . . . 125
251-255. Organization of fortifications, mines, and torpedoes
for the defence of harbors, 126
256. Remarks, 127
CHAPTER X.
The Defensive Organization of Frontiers with Permanent
Fortifications.
257. Opinions held by prominent military authorities on the
necessity of fortified frontiers, .... 128
258. Remarks on the organization of the frontier defences
of the United States, 129
C0NTEKT8. xi
ART. PAOB
259. Important points to be fortified, 180
260. Rivers and mountain ranges as natural defensive
lines 180
261. Advantages offered both in defensive and offensive
operations by fortified points on rivers, . . . 131
262. Points to be fortified in mountain ranges, . . 181
268. Defensive means adopted for the coasts of the United
States, 181
264. Character of the works necessary for sea-coast de-
fence, 182
265. Defences for important commercial marts and naval
depots, 182
266. Defence of important extensive roadsteads, . . . 184
267. Opinions entertained by foreign military authorities
on the fortification m a permanent manner of im-
portant inland centres of population, . . . 184
268. Fortifications of Paris and Lyons in France, . . 185
269. Objections to the adoption of European practice for
the defences of the large cities of the United
States, .185
CHAPTER XI.
SUMMABT OF THB PROGRESS AND ChANQBS OF FORTIFICATION.
L PROGRESS OF THE DEFENCE.
270. Fortification as seen in its earliest stages, . . . 187
271. Enclosures of simple stone walls and towers, . . 187
272. Insufilciency of these against improved means of of-
fence, 188
278. Introduction of ditches and wide ramparts as defen-
sive features, 188
274. Examples of the great strength and extent of some
ancient fortifications, 189
275. Methods of attack used by the Ancients, . . . 189
276. Defensive methods employed by the Ancients, . . 140
277. Rise and fall of the art under the Romans, . . . 140
278. Progress of the art under the Western Empire, . . 141
279. Conditions of the art under the Feudal System, . . 141
280. Castellated fortifications of the Feudal Period, . . 142
281. Fortifications of cities during the same period, . . 142
282. Changes in the art occasioned by the invention of
gunpowder, 148
288. First appearance of the bastioned system and the
changes consequent upon it, 148
284. Italian school of engineers, 144
285. Spanish school, 145
286. Dutch school, 145
287. German school, 146
288. Swedish school, 146
289. French school, 147
XU CONTENTS.
n. PROGRESS OF THE ATTACK SINCE THE mVENTION OF
FIREARMS,
ART. PAOR
290. Methods and progress of the attack from the inven-
tion of gunpowder to the time of Vauban, . . 148
291. Changes and improvements made in the methods of
attack by Vauban, 149
292. Present condition of the art in the United States, . . 150
298. Probable changes in the immediate future, . . , 151
CHAPTER XIL
Modern Constructions in Iron and Steel.
294. Introduction of armor, 152
295. Its development, 153
296-299. Its behavior under impact and relative cost, . . .153
300. Application of armor to land defences comparatively
free from difficulties, 154
301. English armored forts, . 154
802. English turrets, 155
808, 304. Dover turret, 153
305,306. French turret (Mougin), 155
807, 308. German turret (Schumann), 156
809. Competitive trials of French and German turrets* . 157
310. Revolving turret caponier, 158
811. Fixed turret caponier, 158
312. Disappearing turret, .159
818. Cost of small turrets, • ' . 159
814. Application of small turrets, 159
815. GrUson casemates, 160
APPENDIX I.
Penetration of Projectiles and Thickness of Parapets.
Formulas for penetration in iron, 161
Calculated penetration into clay, sand, and granite, • . .162
Actual penetrations into earth, granite, concrete, etc., • . 163
Prescribed thicknesses of German parapets, • . • • • 164
APPENDIX II.
Frontier and interior fortifications of France, Germany, Italy,
Austria-Hungary, and Russia in Europe, . . • • 165
APPENDIX III.
Books of reference, 170
CONTENTS. XIU
LIST OP PLATES.
Plate No. 1. Typical modem profiles.
" 2. Mortar battery.
•' 3. Profiles of older forts.
*' 4. Scarps, cjunterscarps, and galleries. '
" 5. Sea-coast fronts, caponni^re and bastionet.
" 6. Sea-coast and land-front casemates.
*' 7. Barbette battery and disappearing gun-carriages.
** 8. Machicoulis, posterns, Totten embrasures, and outline
plans of different systems of fortification.
** 9. Outworks.
** 10. Vauban and Cormontaigne's fronts.
** 11. Brialmont's method.
** lla.Noizet's front.
*' 12. Choumara's method.
** 13. Montalembert and Camot's methods.
** 14. Fort Alexander and front of Posen.
" 15. TSte de pont opposite GermersheinL
** 16. Detached work (German).
♦* 17. Problems of defilade.
*• 18. English, French, and German turrets.
19. Disappearing turrets, fixed and revolving iron capo-
niers.
44
FsoirnsFiECB — GrQson chilled iron casemated battery near Antwerp.
ELEMENTS
OF
PERMANENT FORTIFICATION
CHAPTER I.
FREUMINART CONSIDERATIONS AND COMPONENT
ELEMENTS OF PERMANENT DEFENCES.
I.
PRELIMINARY CX)N8IDERATION8.
1. The tQYva permanent fortifiGati(yii is applied to those
defences which, constructed of materials of a durable nature
and designed for permanent occupancy by troops, receive
such a degree of strength that an enemy will be forced to
the operations either of a siege or a blockade to gain pos-
session of them.
2. These defences differ from temporary fortification but
in degree ; the general principles of defensive works being
alike applicable to both.
3. The object of such defences is to secure the permanent
military possession of those points, either on the frontiers
or in the interior of a state, which must at all times have a
well-defined bearing on the operations of a defensive or an
offensive war.
4. For the attainment of this object the following gen-
eral conditions should be fulfilled in the arrangement of
such defences :
1st. They should he of sufficient strength to resist with
success all the ordinary means resorted to by an assailant
in an open assault.
2d. Se ^provided with suitable shelters to protect the
troops^ the armament^ and the m/igazines of provisions and
munitions of war required for their defence against tlie
destructive measures of the assailant.
1
2 ELEMENTS OF PEBMANE19T FORTIilGATION.
3d. Be 80 planned that every point exterior to the de-
fefncea within cannon range shall he thoroughly swept by
their fire.
4th. Have secure and easy means of communication for
the movement of the troops^ both vMhin the defefnces and to
the exterior.
6th. And, fincJly, he provided with oH such accessory
dtfensive means as the natural features of the position it-
sdf may afford^ to enable the garrison to dispute with energy
the occupancy by the assailant of every point both within and
exterior to the aefences.
The defensive branch of the military engineer's art con-
sists in the knowledge of the means which are employed to
fulfil the above conditions, and of their suitable adaptation
to the natural features of the positions he may be called
upon to fortify.
II.
OOMPONBNT BLSMSNT8 OF PHEIMANBNT WORKS.
GSNKSAL FBOFILE.
6- The first condition laid down for permanent defences,
security from open assault, supposes a strength of profile
greatly superior to that which is given to temporary works.
6. The usual and most simple form of profile for perma-
nent works consists of a rampart^ a parapet^ and a ditch^
exterior to which a glacis is usually thrown up.
The Rampart, a. Plates 1 and 3, is an earthen mound,
raised above the natural level of the ground, and upon
which the parapet b is placed.
The rampart thus serves to give the troops and arma-
ment, which are placed on top of it and behind the parapet,
a commanding view over the ground to be guarded by the
fire of the defences; whilst at the same time it increases
the obstacle to an open assault by the additional height it
gives to the scarp.
The top surface of the rampart, b c, in rear of the parapet.,
termed the terre-plein., affords the troops and armament a
convenient position for circulation from point to point,
where they are sheltered from the direct view of t^e aoeail-
ant.
The rampart is usually terminated on the interior, a b, by
ELEMENTS OF PERMANENT FOBTIFICATION. 3
allowing the earth to assume either its natural slope, or one
somewhat less steep, termed the ramvart-slope.
Id eases where tnis slope would take up too much of the
ground within the defences it is replaced by a wall, termed
iki^ parade-wall^ which rises from the level cf the interior
ground, termed iki^ parade^ to the interior line of the terre"
plein.
Inclined planes of earth, termed rampa^ lead from the
parade to the terre-plein, and serve as communications be-
tween them.
7. The Parapet, b, PI. 3, Fig. 4, serving the same pur-
poses in permanent as in field works, receive the same gen-
'Cral form as in the latter.
The essential properties of the parapet, as in field-works,
are to afford cover from the enemy's missiles, and every
facility for sweeping his positions by the fire of its artillery
and small-arms.
To afford perfect cover against direct fire, at short range, a
thickness of parapet equal to once and a half the penetration
of the gun brought against it is usually used. (For penetra-
tions, see Appendix I.) It is not always practicable to give
this full thickness, nor is it in the general case necessary,
since the penetration of elongated projectiles into parapets
of the usual form is less than into experimental butts. The
projectile will generally be deflected from its direct course,
turn upward, and pass out from the superior slope before
passing through the parapet. These considerations have led
the German engineers to give to the parapets of their new
inland forts, Plate 1, Figs. 1 and 3, a thickness varying from
17 to 23 feet, and to sea-coast works 40 feet.
The French consider 20 to 26 feet necessary for land
fronts, and our own engineers have recommended in special
•cases 70 feet thickness in sea-coast batteries. The most of
the parapets of existing works have received only from 18
to 20 feet, and these will doubtless be found to give efficient
<;over against any ordinary attack.
In small works of less importance and not liable to be
breached the thickness may be reduced to 12 or 15 feet.
In some cases the exterior slope, PI. 3, Fig. 12, is replaced
by a wall, which, resting on the top of the scarp wall, rises
to the level of the supenor slope.
The exterior slope of the parapet usually rises from the
top of the scarp wall, leaving a narrow berm between it and
the scarp, or face of the wall.
In some cases, however, it is thrown so far to the rear of
4: ELEMENTS OF PERMANENT FORTIFICATION.
the scarp, PI. 1, Figs. 2 and 5, as to leave suiEcient room
for a communication c, in front of the parapet, in which the
troops can circulate under cover from fire, being masked
either by an earthen parapet, or by a wall, d. This covered
communication, c, is termed an exterior corridor or chemin--
de-Tonde.
For the superior slope, the rule, so long in use, of making
it six base to one perpendicular, or ^, is still generally fol-
lowed.
This rule has not been adopted because cannon cannot be
fired under a greater depression than ^, although, from the
inconveniences attending greater depressions than this, artil-
lerists are unwilling to resort to them ; but from a greater
depression necessitating the employment of very deep em-
brasures, or else that of platforms raised so liigh to the rear
that the men serving the guns will be very much exposed
to fire.
Still, where a greater or less plunge is necessary to bring
the exterior ground better under fire it should be adopted,,
as it is to be observed that the strength of the parapet at
the angle of the interior crest should be increased where the
assailant can have a plunging fire on it ; whereas when ex-
posed to a fire from a level much below this crest the angle
at it will he less exposed, and the plunge of the parapet can
be increased without injury.
Until within a recent period, the interior slope, the ban-
quette, and banquette slope received the same forms and
dimensions as in field works ; the top of the rampart falling,
from the foot of the banquette slope to the crest of the ram*
part slope, one foot, to drain off tne surface-water.
In the later profile the interior slope is \^ and has a ban-
quette tread of only 2 feet, with a banquette slope of only \.
Where guns are mounted either in barbette or embrasure
the interior slope is increased to f, and the banquette and its
slope removed ; the earth taken off by these modifications
serving to form the merlons between the shallow embrasures
cut into the parapets.
When the foot of the exterior slope rests on the top of
the scarp wall, a berm of two feet in breadth is left between
it and the edge of the coping. This breadth of berm is
objectionable, as giving a good landing-place for a scaling-
party in an open assault ; and it is proposed, when the work
is in danger of an attack, to reduce the berm to 18 inches or
one foot, by increashig the thickness of the parapet 6 inches
or one foot.
ELEMENTS OF PERMANENT FORTIFICATION. 5
The exterior slope, for the reasons given in discussing the
parapets of field-works, should not be greater on land fronts
than the natural slope of the earth of which the parapet is
formed.
8. The profiles now used are shown in Plate 1, Figs. 1, 2,
3, 4, and 5. The part of the terre-plein used as a general
barbette for heavy guns has a width and height suitable for
the carriages used ; that used as a road in rear is given a
breadth suflicient for communication (20 to 25 feet), and is
placed low enough to be screened from a trajectory falling
at an angle of i, if this is consistent with a sufficient cover
over the arches of the bomb-proofs.
In the older works the terre-plein received a breadth of 40
to 50 feet, estimated between the interior crest and the top
of the rampart slope. From motives of economy, and some-
times to enlarge the parade, this breadth was reduced to 20
or 24 feet, and a parade wall substituted for the rampart
slope. The great length of modern guns and the necessity
for increased room for bomb-proofs under the terre-plein
have caused a return to a greater width. The minimum is
now about 40 feet.
The great command and low scarps of modern works
make the exterior slope much longer than it formerly was.
It is sometimes broken up by introducing two or more bernis
between its crest and foot.
9. The command, or height of the parapet above the site,
has a very important bearing in the close defence of perma-
nent worts.
In the first place, the greater the command, the greater
will be the plunge of the guns on the exterior ground, and
the more difficulty will the assailant meet with in obtaining
cover in his trenches from this plunge ; being obliged to
make them deeper than usual, and to increase the height of
their parapets.
In the second place, having to fire under greater angles
of elevation, as the command is greater, he will only be able
to reach the terre-pleins by the use of diminished charges
and a corresponding decrease in accuracy of fire. For
defence against the distant attack by long-range guns these
considerations have less weight, the advantage of command
in this case arising principally from its giving a better view
of the enemy's works.
Motives of economy, however, require the command to
be restricted within quite narrow limits. When the work
consists of a simple enceinte enveloped by a covered-way
6 ELEMENTS OF PERMANENT FOBTIFICATION.
the command may be reduced to 16 feet, which allows a
suflScient command above the glacis crest. The height of
the latter is so fixed that a projectile falling at an angle of
i and just grazing- it shall not strike the scarp wall at a
distance less than sixteen feet above its bottom.
10. ScABP. — Scarp walls sltb/uU, detached, or semi-d^
tacJied, A full scarp wall is a retaining- wall extending
from the bottom of the ditch to the foot of the exterior
slope, which rests upon its top (Plate 3, Figs. 2 and 4).
A detached scarp wall (Plate 1, Figs. 1, 2, and 3) risea
from the bottom of the ditch, leaving between its back and
the foot of the rampart behind it a breadth of several feet,,
either on the same level as the bottom of the ditch, or raised
a few feet above this level. In some cases the wall is built
with several tiers of arched recesses on its back, the por-
tions of the wall in front of which are pierced with loop-
holes, each recess being of sufficient size to give shelter ta
several men serving the loop holes, and firing into the ditch
and on the top of the counterscarp.
A semi-detached scarp wall (Plate 1, Fig. 5) has its lower
portion made as retaining- wall, generally built with reliev-
ing arches, either closed or open m rear ; the upper portion
for a height from 8 to 12 feet being detached from the ram-
part and prepared for defence like the preceding example.
Detached and semi-detached scarp walls have evident
advantages over the full scarp. They are better covered
by the glacis from the plunging fire of the assailant ; they
otter the same obstacle to an escalade as the latter, and
when the assailant has gained the top of the wall they
present the farther difficulty of his getting down on the
other side ; they give a good fire upon the ditch, and are
thus favorable to the safety of sortie parties in retreat ;.
and when a wide space is left between them and the para-
pet, room is afforded for the formation of a column on each
side of any breach made in the wall, to charge in flank an
assaulting column entering the breach.
On the other hand, these walls favor an assaulting column
rushing through a l)reach in them, as the assailants can
spread along the corridor on the right and left, and assault
the work on a wider front. Should the assailant not choose
this course, he has the alternative of establishing himself
securely upon the exterior slope in trenches ; and if it suits
his purposes better, to drive a mine gallery from the breach
into the rampart, to blow it up and open a breach into the
work.
ELEMENTS OF PERMANENT FORTIFICATION* 7
But a very marked defect in all of these detached scarps
is the exposed condition in which the men behind them are
from the splinters from the walls when the corridor can be
enfiladed, and from the splinters of exploding shells, which
either lodge and explode in the rampart, or roll down it and
explode in the corridor.
* To break in some measure the eflfects of this enfilade, and
also to prevent an assaulting column from spreading to the
right and left along the corridor, traverse walls, having
doors in them for communication and loop-holed to fire
along the corridor, are placed from point to point, running
from the scarp wall back to the exterior slope across the
corridor. But these cross-walls would soon be destroyed
by an ordinary enfilade, and the splinters from them would
render the corridor untenable.
Notwithstanding this defect, on account of their many
advantages, detached and semi-detached walls are now very
generally adopted by engineers. Since their obj'ect is to
prevent escalade and stop assaulting columns and lines, they
would ordinarily only be manned by the defenders when
the assailants were so close to them as to preclude the use
of their artillery against the defence.
In order to protect dry ditches against escalade a scarp
wall 30 feet high was until recently considered necessary.
This height had been established from long experience in
sieges preceding the introduction of the breech-loading small
arms and metallic ammunition. With the increased rapid-
ity of fire resulting from these improvements, and machine
guns, engineers are all of the opinion that a less height will
now afford ample security.
The French engineers consider the maximum height nec-
essary for full scarps for main works to be from 23 to 26
feet, and for outworks from 16 to 20. With detached
scarps they reduce these heights to 20 feet for the main
work and 16 or even 13 for the outworks. The German
and Belgian engineers adopt about the same heights.
Some engineers have shown a tendency to do away with
either the revetted scarp or counterscarp, and in some in-
stances with both ; trusting to entanglements and other
obstacles combined with the fire of the work to repel
assault.
While these means may be sufficient in works fully gar-
risoned and protected against surprise by constant watch*
gulness, a restriction to their use would be fraught with
ireat danger tj works having small garrisons if suddenly
3 el:ements of permanent fortification.
attacked, and would add greatly to the fatigue of the de-
fence by the additional guard duty and the constant state
of readiness to repel assault required of the garrison. As
the object of all fortifications is to compensate for numen
cal weakness on the part of the defence, the safer practice
would seem to be to do this by placing such an obstacle in
the way of an open assault that but a few men promptly
availing themselves of it might hold back the assailant
until a sufficient force could be gathered at the point as-
sailed to render the attack abortive.
Besides securing the place from an escalade, full and
semi-detached scarp walls act as retaining-walls, to hold up
the excavated side of the ditch towards the rampart, the
rampart itself, and the parapet. This requires that they
should receive a thickness and form of profile adapted to
this end.
The top stone of the wall, k, PI. 3, Fig. 4, termed the
coi'don or coping^ projects beyond its face, and serving as
a larrnier or drip^ protects it from the eflfects of the rain-
water, which runs from the parapet upon the coping.
The line in which the face of the scarp wall if prolonged
would intersect the coping is termed the magistral. This
is a very important line in drawing the plans of permanent
works, serving as the directing line to fix, both npon the
drawing and upon the ground in setting out the work, the
dimensions and relative positions of all the bounding lines
of the parapet and other parts.
Although no ordinary scarp walls can resist breaching,
and have to be covered by earthen masks to screen them
from the distant fire of the assailed, they should be so con-
structed as to render breaching a difficult operation ; limit-
ing the breach made to the part of the wall actually de-
stroyed by the assailant's projectiles.
In the scarp walls of Yauban and Cormontaigne, and in
many of the more modern fortifications of Europe, the scarp
walls are built solid, with counterforts on their back, of the
forms and dimensions adopted by Yauban. This engineer
gave his scarps a thickness of about \ their height and a
batir of \. Cormontaigne, finding that the faces of these
walls were soon injured by the weather, adopted a batir of
-f-. This for the same reason was increased by some to ^,
by others to ^ ; and in our climate, where the action of
the weather on masonry is very injurious, our engineers
have varied their batir from \* to 4j9.
ELEMENTS OF PERMANENT FORTIFICATION. 9
To give greater eflScacy to the resistance offered to
breacluDg, and to prevent the breach from taking a gentle
.slope when formed, it has been proposed by some to back
the wali and counterforts by a kind of pise work, or with
beton with but little lime in it, of several feet in thickness.
Others have proposed, for the same purpose, to connect
the end of the counterforts by vertical arches, and to till the
^ells thus formed either with pise, or with this poor beton.
Others prefer long thin counterforts sustaining several
tiers of relieving arches; the cells thus formed being left
open for defence, for bomb-proof shelters, and for maga-
.zines for provisions, etc.
All these expedients have been tried, though not fully
tested by experiment ; the last under all points of view hav-
ing the most advantages in its favor.
11. Counterscarp Wall. A revetted counterscarp is
regarded as adding to the difficulty of descending into the
ditch, and as oflFering greater security against an open
assault. For this purpose the wall should not be less than
12 or 15 feet in height to offer a serious impediment ; in any
«case, where motives of economy do not imperiously forbid
it, the counterscarp wall of the enceinte should be from 18
to 24 feet in height. This height will not only give great
security to the ditch, but, as will be seen in the description
of the siege works of the assailant, it will delay considerably
his progress, as the gallery by which he must generally
reach the bottom of the ditch from the level of the covered-
way terre-plein is one of the slowest and most laborious of
his operations.
Besides giving greater security against a surprise, a
revetted counterscarp enables the assailed to circulate
through the ditches even when the assailant has established
his trenches along the glacis crest, as the top of the counter-
scarp wall will screen the troops passing along the bottom
of the ditch.
It also affords facilities for forming a counterscarp gallery
hehind it loop-holed for the defence of the ditch against an
open assault, which for small works without thorough
fidiiking arrangements wiU hefowid very serviceable.
Besides, this gallery will be found of great utility where a
isystem of defensive mines is to form a part of the defences.
But as counterscarp galleries, if seized upon by the
assailant, may be turned against the defences, it is impor-
tant that they should be placed in positions where they will
be of little value to the assailant if seized upon.
10 ELEMENTS OF PERMANENT FORTIFICATION.
The necessity for revetting with a wall of masonry the-
scarp and counterscarp of a wet ditch in which the water
can be retained at a level of six feet in depth, is not so-
obvious, as when the ditch is wide the obstacle of the water
alone would seem to be sufficient to secure the place from a
surprise. Many works under this condition have been built
with simple earthen scarps and counterscarps; in some
instances a chemin-de-ronde being formed by leaving a wide
berra between the foot of the exterior slope and the crest
of the scarp, and planting a loop-holed stockade near the
crest.
But in rigorous climates, where the water freezes hard, a
wet ditch is no longer a security in winter ; and a dry ditch
with the usual revetted scarp and counterscarp is a better
security against a surprise than the expedients proposed, of
keeping an open channel along the middle of the ditch of
12 feet in width, piling up on each side of it the ice taken
from the channel and tnrowing water over the exterior
slopes to freeze and form a slippery surface to an assaulting,
column.
12. Ditch. The width and depth of the enceinte ditch
depend mainly upon the amount of embankment required
for the enceinte and the glacis, and therefore will result
from the calculation for equalizing the excavation and em-
bankment which these demand.
A deep and narrow ditch offers the advantage of present-
ing more difficulty to the assailant in reaching the bottom
of it, either in an open assault, or by a gallery in the attack
by regular approaches, thus prolonging the defence.
It masks better the sally-ports from the enemy's fire by
allowing them to be placed so low that the projectiles com-
ing over the glacis cannot reach them.
In like manner by drawing in the crest of the glacis
nearer to the scarp the latter will be better masked by it
from the plunge of the distant lire of the assailant's bat-
teries, and cannot be breached so low down from his bat-
teries placed along the glacis crest.
On the other hand, when the ditch is too narrow it maj
be partly filled by breaching the scarp, and then blowing in
the counterscarp so as by the united debris to form an easy
roadway for an assaulting column to enter the work.
A wide ditch, on the other hand, requires more labor ta
construct the trench across it by which the assailant can
reach the foot of the breach under cover. This is a con-
sideration of some importance in wet ditches, where the
ELEMENTS OF PEEMAKENT FOETIFICATION. 11
assailant is obliged to construct a dike upon which the para*
pet of his cover is placed.
In the most recently constracted forts the main ditch is
limited to a depth of about 30 feet and a width of from
13 to 16 yards. "Wet ditches have a widtli of from 20 to 80
yards and a despth of water from 6 to 10 feet. The dimen-
sions are reduced to a minimum where the embankments are
not great and circumstances are unfavorable to an attempt
at escalade.
The bottom of the ditch, when dry, usually receives a
slight slope from the foot of the scarp and counterscarp to
its centre, where a small drain, termed a cunette^ is dug to
receive the surface-water and keep the ditch dry. In some
cases, from motives of economy, the difference of level be-
tween the cunette and the foot of the counterscarp wall is
increased, thus giving a less height of wall. This practice,
however, can only be foHowed where the foundations of the
wall will be secure, from the soil of the bottom of the ditch
being of such a nature as not to yield from the effects of the
weather upon it.
13. Facd Covers. Engineers since the times of Cor-
raontaigne have until recently adopted his method of placing
the top of the scarp wall on a level with the crest of the
glacis, or a little below this crest, to give the wall cover from
the assailant's distant batteries. But this is evidently only a
partial remedy, since the plunge of projectiles fired from a
distance is very great in the descending branch of the tra-
jectory, and with the rifled guns now used, these projectiles
fired from a distance may pass over the glacis crest and strike
the wall quite low down, thus effecting serious damage, par-
ticularly m the case of wide and shallow ditches.
Various expedients have been proposed by engineers ta
remedy this defect. Choumara, an engineer of celebrity,
has proposed to form what he terms an interior glacis within
the ditch, the crest of which shall rise so high above the
bottom of the ditch, that it shall mask the scarp wall from
the plunge of the distant batteries, and shall force the
assailant to establish his breaching batteries on this interior
glacis to enable him to fire low enough to effect a practi-
cable breach in the wall.
Brialmont, a more recent writer, proposes a like plan for
the same purposes; and in one of our own works, Fort
Warren, Boston Harbor, a heavy earthen face-cover naasks
a portion of the scarp wall, from a position from which a
12 ELEMENTS OF PERMANENT FORTIFICATION.
breacLinff fire might have been brought against the part
thus masked.
The latest practice, when face-covers are not used, is to
give the crest of the glacis the depth and width of the
ditch, and the height of the scarp wall such relations that at
least 16 feet of the scarp wall is covered by the glacis from
a plunging fire of ^, See Plate 1, Figs. 1, 2, 3, 4, and 5.
14. General Remarks. The command of the parapet
over the exterior ground and any outworks of the defences,
its reliefs or height above the bottom of the ditch, and its
height above the top of the scarp wall, are all points which
call for a careful consideration on the part of the engineer
in any combination of these that he may be called upon to
make.
First, it is important that the parapet should thoroughly
sweep all the ground within range of its guns, at least up
to the glacis crest ; and the more so as the closer the
assailant's trenches approach the work, the greater will be
the plunge obtained upon them, and the more difficult it
will be for the assailant to cover himself by his trenches.
That the parapet should command all outworks within
range of its nre is obvious, otherwise when seized upon by
the assailant these outworks would have a plunging fire
upon the main work.
The rule is laid down by some authorities, that the pro-
jectiles of the parapet should clear the crest of the glacis
by at least 2 feet. But this is by no means necessary, for if
the glacis has a covered-way for troops in its rear, it will be
impracticable to keep these troops in the covered-way
with missiles passing in such close proximity to them, par-
ticularly as they are subjected to danger from the blast, gas
checks, and unburned powder-grains, as well as from the
bursting of shells in their rear.
The relief of the parapet of the flanking parts of the work
should evidently be such that every point along the foot of
the scarp wall shall be swept by its fire. This supposes also
a certain correlation between the relief and the length of
the lines flanked, so that this condition shall be satisfied ; a
relation that can always be easily found, either by calcula-
tion, or a very simple geometrical construction from given
data.
In like manner the height of the interior crest of the
parapet above the top oi the scarp wall can be easily
ascertained by the same methods, with assumed data. It
should evidently be at least such that a gun, on any kind of
ELEMENTS OF PEEMANEKT FORTIFICATION. 13
carriage, firing through an enibrasure of assumed depth and
under a given depression, should clear the coping of the wall
about one foot.
A mere geometrical diagram will show that as the height
of the interior crest above the top of the wall, supposing the
position of the latter fixed, is increased, the whole parapet
will be thrown further back from the wall, and the interior
space of the work will be in the same degree lessened.
All of these considerations therefore suggest that nothing
like absolute rules can be laid down so as to give a routine
character to the practice of this branch of the military art.
The rules here given with respect to the form and dimen-
sions of the general profile of the enceinte are founded upon
reasons growing out of the nature of the question, and as
such have served as guides to engineers in the practice of
their profession. As they have stood besides the test of
long experience, it is safe to follow them, whilst at the same
time the engineer should not hesitate to vary from them
when satisfied, after careful examination, that the case
before him requires it. Fortification, it must be remem-
bered, is like all other arts : it has its canons, which are
founded upon the nature of the question, and its rules of
f)ractice based upon these and upon experience. As the
atter presents to the engineer new facts, his practice must
be made to conform to them ; but the general principles of
his art must ever remain the same, and be his invariable
guide.
m.
OPBN DEFENCES.
16. By this term are understood the dispositions made
for the action of the troops and armament which afEord
cover only from the direct fire of the assailant.
To this class belong the arrangement of the parapet
which has already been described ; simple loop-holed waUs
for musketry used as inclosures of gorges, detached scarps,
etc. ; exterior corridors which are covered either by a wall
or an earthen parapet ; and barbettes and embrasures for
artillery.
16. Loop-Holed Walls. Walls of this class, when
used as the inclosares of the gorges of lunettes or other
isolated works, placed in advance of the enceinte, but within
li ELEMENTS OP PKRMANEIfT FOBTIFICATIOIS^.
the reach of its artillery fire, should be hidi enough to
secure the work from aa open assault, and sufficiently thick
to resist the occasional shot which may reach them over the
parapet by which they are covered. For these purposes
the neigh t, Plate 4, Fig. 24, should be from 12 to 15 feet,
and the tbicl:nes8 from 4 to 5 feet. The loopholes are not
placed nearer to each other than from 3 to 4 feet, estimated
between their axes. They should be at least 6 feet above
the exterior foot of the wall, and 4J feet above the ground
or banquette within. The loop-holes are usually placed at
regular intervals along the line of the wall, or only opposite
that portion of the exterior ground upon which a fire is to
be brought to bear.
The form and dimensions of the loop-hole will depend
upon the thickness of the wall and the field of view, both
vertically and horizontally, which is to be covered by its fire.
The plan is either trapezoidal, Plate 4, Figs. 17, 20, widen-
ing from the front of the wall inwards, or else it widens
from the centre each way to the front and back ; or, as is
the more usual form in our works, the interior portion from
the centre widens inwards, whilst the exterior part is rectan-
gular in plan, and of the same width as the width on the
interior or back of the wall. The first form is best adapted
to walls not more than 2J feet thick, the others to heavier
walls ; the object being to lessen, as far as practicable, the
weakness which loop-holes necessarily cause to the wall ; this
defect increasing as the exterior or interior opening is greater.
For thin walls, where the plan of the loop-hole is trape-
zoidal, the width of the exterior opening may be from 2 to
4 inches, and that of the interior from 15 to 18 inches.
These dimensions, however, may vary according to the field
of fire to be brought within the range of the loop-hole, the
more or less cover to be given to the troops, and the
strength of the masonry of which the wall is formed. The
vertical dimensions of the loop-hole, both on the interior and
the exterior, will depend upon the field of fire to be em-
braced in this last direction, and they will be regulated
accordingly ; the top and sole of the loop-hole receiving a
suitable slope or direction for this purpose.
The foregoing details can only be well determined upon
from the special object to which the loop-holed defences are
to be applied. Care only is to be taken that in attempting
to give cover to the troops their field of view be not too
restricted by too narrow an opening for the use of the fire-
arms.
ELEMENTS OP PERMANENT PORTIPICATION. 15
Where the throat or narrowest part of the loop*hole is
within the wall, the exterior opening leaves a wider mark
for the missiles of the assailed, and when the sides of the
loop-hole gradually widen outwards, a shot striking one of
them may glance inward and do injury.
To prevent this accident, the sides, and sometimes the
flole, are made in offsets. A more convenient form for con-
struction, and one better adapted for arresting the enemy's
balls, is to make the exterior portion rectan£;ular in plan
for half the width of the wall as alreadv described.
The best form is a modification of this made by placing
at the throat a plate of iron or steel pierced by an opening
generally 2 by 6 inches.
17. Exterior Corridors. In open exterior corridors
the troops are covered in front either by an earthen parapet,
which is usually only musket-proof, the scarp wall being run
up to the superior slope ; or else the scarp wall serves as the
«over, in wnich case it is pierced either throughout its
length or at suitable points with loop-holes. The floor of
the corridor, o, Plate 4, Fig. 2Y, serves as a banquette tread
for the loop-holes, and is therefore placed with reference to
the direction < f the fire from the loop holes. The height to
which the scarp wall rises above the floor of the corridor
^ill depend upon the level of the floor, and that of the bot-
tom of the ditch ; this height, however, should not be less
than 6^ feet to afford a sufficient cover to the troops.
The preceding Fig. 27 is given as an example of a semi-
■detached scarp, a, an earthen counterscarp and covered-way,
D ; being a section of an outwork of one of our sea-coast
forts.
18. Barbette Batteries. For guns mounted on the
ordinary field and siege carriages, the barbettes are con-
structed in the same manner and with the same dimensions
^8 in field-works ; the arrangement of the ramps and the
slopes being determined by the position in which the bar-
bette is placed, and its relative position with respect to. the
terre-plein and parapet.
For the heavy guns used, both for land and sea fronts, a
solid foundation of concrete and stone, with the necessary
iron work, is laid to receive the gun with its carriage, and
to allow it to be worked efficiently. To protect the guns
against flank fire, large traverses (generally containing bomb-
proof constructions) are used. These traverses are extended
upon the parapet so as to form honnets^ affording the greatest
cover consistent with a wide field of fire.
16 ELEMENTS OF PERMANENT FORTIFICATION.
Carriages have been designed which allow the gun to be
lowered behind the parapet for loading, and raised above it
for firing (see Plate 7).
The modifications of parapet, already referred to, to suit
special carriages and guns, are very marked when this clas&
of carriage is used, also when arrangements are made for
loading the guns under cover. This cover is obtained by
making bomb-proof communications and chambers, opening
toward the gun, under the parapet and traverses, in which
the machinery for loading the guns is placed, and which
allow the ammunition to be safely carried from the maga-
zines to the guns.
These, or similar protections, have become absolutely
necessary to prevent barbette guns being silenced, if they
are exposed to the close fire of small-arms and machine
guns.
Where ample space exists for placing batteries of heavy
guns, with considerable command, and a favorable soil, par-
ticularly for coast defence, the modification of parapet may
extend even to sinking a pit for each gun and constructing
bomb-proof underground communications, magazines, quar-
ters, store-rooms, etc., for their service.
19. ISmbrasure Batteries. The embrasures cut in
the parapets for guns on field and siege carriages differ in
no essential point from those for field-works. It is well,
however, to observe, as the parapet is weakened by receiving
embrasures, the splay given to them should, in all cases, be
carefully regulated by the field of fire it is desirable to com-
mand, so as to leave as large a mass of merlon between theia
as practicable, to resist the assailant's fire.
20. Machicoulis. For the purpose of attaining, by
musketry, the foot of a scarp wall without flank defences,
resort must be had to a machicoulated arrangement at the
top of the scarp.
The usual mode adopted for this purpose, PI. 8, Figs. 67,
68, is to form a parapet wall which rests upon a solid hori-
zontal band of stone, near the top of the scarp, which is.
supported on corbels or projecting blocks, firmly built into
the wall. The back of the parapet wall is placed a few
inches in advance of the scarp, leaving room for the slanting
loop-holes pierced in the horizontal band through which tlie
fire is to he delivered on the foot of the scarp. The top of
the parapet wall is also arranged to admit of firing on more
distant points.
In the example given, which is from an Austrian author-
ELEMBKT8 OF PEEMANBNT FOBTiriCATIOIT. 17
ity, Fiff . 67 is a front elevation, and Fig. 68 a section through
a loopiole.
Figs. 65, 66 are a front elevation and section through a
loop-hole, from the same authority. This is a semi-detached
scarp wall, the top portion of which is arranged on the back
with loop-hole recesses ; the lower portion having very in-
clined arched recesses in front, with slanting loopholes to-
fire on the foot of the scarp from the upper recesses.
' Where from the irregularity of the site the ordinary
machicoulis cannot be made efficient, resort may be had to
small polygonal chambers of stone, open at top, and having
the sides and bottom pierced with loop-holes and machicoulis.
These constructions may be made just of sufficient size to
hold a single sentinel. They are placed at the angles of
the works where they will not be exposed to artillery, and
are supported on a corbel work projecting from the top of
the scarp wall.
These devices will be rarely if ever used in works con-
structed in the future, since they are absolutely useless if
exposed to artillery fire, and can generally be replaced by
cheaper and simpler constructions, which are equally efficient
upon fronts not so exposed.
OOVEBED DEFENCES.
21. Detached Scarp Walls. When the scarp wall?
are entirely detached, leaving an open corridor between
them and the rampart, they are pierced with one or two-
tiers of loop-holes, from which a fire can be brought upon
the ditch and in some cases upon the terre-plem of the
covered- way, or any work in front of the enceinte.
To give cover to the men at the loopholes arched re-
cesses, PL 4, Figs. 25, 26, are made in the thickness of wall,,
or else short counterforts are built back from the wall,
which serve as the piers of covering arches. The width of
the recesses should admit of three or four loop-holes at the
usual distance apart, their height and depth being sufficient
to give the men shelter from vertical fire and jHIow them
to handle their arms with convenience.
The two Figs, above are sections of this description of
scarp wall taken through the crowns of the arches, as shown
in an Austrian work, a is a section of the wall ; b and d.
18 ELEMENTS OF PERMANENT FORTIFICATION.
elevations of the sides of the recesses; c, an elevation and
section of the recess arch.
22. Semi-detached Walls, Fig. 28, are also in some
cases built with recesses. Besides these, traverse walls, h, are
built back from the scarp wall into the parapet, at intervals,
to afford cover to troops, circulating in the corridor, from
enfilading fire, and to admit of a defence of the corridor if
the assailant should enter it between any two of these tra-
verses. For this purpose they are pierced with loop-holes,
and have door-ways for circulation throughout the corridor.
23. Scarp Galleries. In the permanent works of more
recent construction in our own country and in Europe
revetment walls with relieving arches, rl. 4, Fig. 15, have
in most cases been introduced mstead of the ordinary thick
nvalls with counterforts, which had been hitherto the usual
mode of retaining the earth of the rampart and parapet.
The piers of the relieving arches, which also serve as
counterforts to the revetment-wall, are rectangular in plan,
and usually run back from 12 to 16 feet. They are from 4
to 6 feet thick, and placed from 12 to 18 feet apart be-
tween their centre lines. The arches are usually full centre
and 2 feet thick, with a rough shaped capping which adds
an additional thickness from 9 to 12 inches over the crown
of the arch.
The preceding Fig. is a section of a revetment wall of
this kind, of one of our forts, through the curtain in front
of which is a mask of which d is the section, b is an eleva-
tion of the face of the pier ; o, the relieving arch ; and a,
the scarp wall.
This mode of construction offers the advantages of a more
stable structure and rendering it more difficult for the as-
sailant to make a practicable breach in the wall, whilst by a
suitable arrangement of the relieving arches and their piere
with the earth of the rampart, a sufficient space can be
secured behind the scarp wall to form a gallery for defensive
purposes.
The arches and piers form the top and sides of the gal-
lery, the scarp wall forming the front, and the back or rear
being either partly or wholly closed by a wall which retains
the earth behind it. The gallery is thus divided up into
chambers, the communication between which is effected by
doorways made through the piers.
The width and height of the gallery should in all cases
be sufficient to allow the men ample room for handling
ELEMENTS OF PERMANENT FORTIFICATION. 19
their fire-arms, and to admit of a cireolatioD through the
gallery when the troops for the defence are posted in it.
From three to four loop-holes are made in the portion of
the scarp wall that forms the front of each chamber. The
dimensions and forms of the loop-holes are the same as
already described, and they are otherwise arranged for de-
fence as in detached scarp walls.
In PI. 4, Fig. 16, a section of a scarp gallery constructed
in one of our older forts is shown, a is the scarp wall ; b
the pier of the relieving arch o ; d the rear wall which closes
the gallery and sustains the earth behind it. The section
also shows the parts of the rampart and parapet and the
breast-high wall e.
In Figs. 17, 18, 19, the plan, section, and rear elevation
of a galkry are shown as given in French authorities. The
peculiarity of this example, Fig. 19, consists in the arrange-
ment of the ^^ar of the gallery, which, instead of being
entirely closed by a wall, is only partly so ; a small wall, a,
which rests upon an arch, b, built between the two piers, is
placed parallel to the back of the scarp wall and at a distance
from it equal to the width of the gallery, the top of the wall
being raised to the level of the surface of the earthen slope
which falls in behind from the top of the arch. The sec-
tion, Fig. 18, through r s, and elevation, Fig. 19, show the
position of the loop-holes, and the vent for the escape of the
flmoke is pierced in the scarp wall just below the crown of
the arch, b, are the piers ; a the arches with their capping ;
D the doorways through the piers.
Figs. 20, 21, represent the plan and section of a scarp
gallery in two tiers, as given m an Austrian work. The
rear of the gallery is closed by a simple wall. Besides the
vent holes for the escape of smoke, drains are made in the
«carp wall at the level of the gallery floor to convey ofE any
water that may collect in it.
Figs. 22, 23, are a plan and section, from the same author-
ity, of a gallery behind the lower portion of the scarp wall,
the upper portion being connected with relieving arches
so arrangea that, being open to the rear, the foot of the
slope of earth will just touch the back of the wall at its foot
within. In this example the pressure of the earth being
supposed to be great, the ^llery is closed in the rear by
arched walls ; the arches being built into the vertical piers
B, of the relieving arches o. This example also shows the
manner of barricading the doorways through the piers by
20 ELEMENTS OF PERMANENT FORTIFICATION.
vertical grooves, made in the opposite faces of the piers, to
receive me scantling forming the barricade.
In Fig. 28 is shown the section of a gallery behind the
lower portion of the scarp, with the npper portion arranged
with recesses for loop-holes.
These same methods of construction are now adopted^
with changes in dimensions resulting from the different
height of scarp walls and the need of an additional depth of
protection against vertical fire.
The galleries are now made, almost exclusively, one tier
in height, the arches receive a thickness of 3 feet of brick
or concrete and a capping of 12 to 18 inches covered with
from 5 to 15 feet of earth, according to their exposure.
24. Counterscarp Oalleries. PI. 4, Fig. 35. The
most simple method of arranging a gallery behind a coun-
terscarp wall for the defence of a ditch is to build another
wall parallel to that of the counterscarp, and to throw an
arch over between the two to cover the top of the gallery^
The counterscarp wall is pierced with loop-holes arranged in
the same way as in scarp galleries.
The example selected is from one of our works, and
shows a section of the gallery through a loop-hole, a, coun-
terscarp wall ; D, parallel wall ; c, arch and capping ; e, gla-
cis mask covering the scarp wall.
In Figs. 29, 30, 31, are shown a plan, section on r «, and
a section and interior elevation on o p^oi a counterscarp
gallery taken from a French authority. In this case coun-
terforts, square in plan, are built along the back of the
counterscarp wall, leaving 8 feet between them. Parallel
to the counterscarp wall and 4 feet in rear of the coun-
terforts another wall is built, which, with the counterforts,,
serves as the support of a series of arches perpendicular to
the counterscarp wall sprung between the counterforts, and
another parallel to it and restmg on the counterforts and par-
allel wall. The arches between the counterforts form with
them recesses, a, for the men serving the loop-holes pierced
in the counterscarp wall ; whilst the covered space, b, in rear
serves for circulation without disturbing the men engaged
in firing.
Counterscarp galleries may also be arranged for a ditch
defence with artillery ; howitzers, rapid-firing and machine
guns are used for this purpose. A plan, Fig. 32, a vertical
section and side elevation on d o, Fig. 33 ; and a section and
back elevation on a b, Fig. 34, taken from one of our works,
show a disposition of this kind in the reentering angle of
tlie counterscarp.
ELEMENTS OF PEEMANENT FORTIFICATION. 21
26. Bastionnets. In small works, where a flanking
disposition cannot be obtained from the enceinte, as in la-
nettes and redoubts, the ditches may be swept by covered
-chambers, PI. 5, Fig. 39, attached to the scarp wall either
^t the centre of the sides of the work, or at the angles.
These chambers, PI. 5, Fig. 39, are usually of a pentago-
nal form, the sides which join the scarp wall serving to
flank it, and the two exterior sides, forming a salient angle,
delivering their fire on the opposite counterscarp and its
crest. From their form and purposes they have received
the name of bastionnets.
The dimensions of these constructions will depend upon
the amount and kind of fire to be delivered. Their scarps
should be as high as that of the main work. The entrance
to them is either directly from a parade by a postern, or
from a scarp gallery which flanks them.
Fig. 39 shows a plan of bastionnet, d, at an angle com-
municating with a scarp gallery, e. In rear of the scarp
gallery and opposite to the bastionnet, is placed a small
powder-magazine for its service. The example is from an
Austrian authority, and is arranged for one small gun on
«ach flank, besides the loop-holes for small-arms.
As a general rule, it may be laid down that the salient
angles of the redoubt are the most suitable positions for
tiie bastionnets, as they will thus form small bastioned
fronts, in which both the faces of the main work and those
of the bastionnets will be swept by the flanks of the latter.
The only danger in this arrangement is that the loop-holes
in one flank may be fired into from the opposite one. This,
however, may be guarded against by a suitable position
given to the loop-holes.
As the main object of covered defences is protection
against shells, it is essential that the arches of the galleries
and bastionnets should be bomb-proof. The thickness pre-
viously given is generally thought necessary, but where the
span of the arch is very small the thickness of the brick
m^be reduced to 2 feet.
With regard to the front walls of these constructions, as
they are too weak to withstand the direct action of artillery,
they must either be covered by earthen masks, as a glacis
raised beyond the counterscarp for example, or be used only
in positions where they are not exposed to this fire.
General Remarks. It should be observed that what-
ever advantages covered defences afEord as shelter from tlie
.assailant's fire, they present the inconveniences of a com-
22 ELEMENTS OF PERMANENT FORTIFICATION.
parativel V narrow and obstructed field of view to the as-
sailed, which is further obscured by the smoke which may
father within the gallery, and in front of the loop-holes,
'rom these causes the assailed having to aim at a venture^
his fire is likely to be less effective than in open defences^
where the smoke disperses rapidly and leaves a clear field
of view. The same may be said of loop-holed walls cover-
ing exterior corridors where the space to the rear is confined^
Owing to these considerations, loop-hooled and covered
defences of the kind in question should be restricted to
special defensive purposes, where an object within the field
of fire can be attained with some certainty whether seen or
not by the assailed ; as, for example, the protection of a
ditch, or a scarp wall which cannot be flanked from within
the work ; for sweeping a covered-way, or the interior of
any outwork which cannot be brought well under the fire
of the parapet of the main work.
26. Gaponniere Defences for the Enceinte Ditch.
These works are classed under the head of what are termed
defensive cdsemates^ which are bomb-proof arched structures
for receiving cannon, firing through embrasures pierced in
the front or mask wall of the casemates. Defences of thia
class, when used to flank the ditch, are usually termed cdse^
mated caponnieres.
These defences are usually placed in the ditch at the
middle point of the side or front to be flanked. The out-
line of their plan is mostly that of a lunette, PL 5, Fig. 36,
the flanks being perpendicular to the line of the scarp, and
the two faces making a salient angle of 60°. The capon-
niere is either built in juxtaposition with the enceinte, or
else detached from it. In the latter case an inclosure ift
formed between the two by a loop-holed wall which con-
nects the flanks with the scarp wall. Each flank consists of
one or two tiers of arched chambers, the piers of the archea
being perpendicular to the back of the walls of the flank.
Each cnamber is of sufficient dimensions for the service of
a single gun with a contracted field of fire. (PI. 5, Figs»
36, 37.) In some cases loop-holes are pierced for small-
arms on each side of the embrasure ; in otners the casemates
of one story are pierced for cannon, and the other for small-
arms.
The casemates are closed in rear by a thin wall, which is
provided with windows for light and ventilation ; and the
piers are pierced with doorways to form a communication
between tne chambers and to assist the ventilation. Fluea
ELEMENTS OF PERMANE:N^T FORTIFICATION. 2S
or vents, Fig. 37, are made in the front wall, just nnderthe
arches, for a like purpose. Where it may be necessary, the
lower floor is drained by a conduit through the front wall.
An open court is left between the flanks, and each flank
is covered at top with from 6 to 12 feet of earth. The
flanks are separated from the faces by a closed corridor
which serves as a communication.
In front of the corridor and on each side of the axis of
the caponniere on second floor, a casemated chamber, which .
is open in front, is arranged for one mortar. Figs. 36, 38.
The arches of these chambers rise towards the front the
better to subserve the object in view.
On one side of the chambers on first floor the powder
magazine is placed, with a store-room. On the other side
a stairway between the stories is built.
The space within the salient angle, inclosed by the walls
of the faces and the front of the mortar casemates, is open
at top. It has an open corridor on the second story for
communication, and tne front walls are arranged with loop
holed recesses for small-arms, Figs. 36, 38.
The enceinte, in the rear of the flanks of the caponniere,
is arranged with a scarp gallery, to flank the caponniere
flanks and the court between them. A break is in some
cases made in the line of the scarp wall, perpendicular to
the caponniere faces, and casements for cannon and small-
arms arranged behind the scarp wall, to flank these faces.
In some cases these flanking dispositions are placed in front
of the scarp wall, the casements being open to the rear, look-
ing on a narrow court between them and the scarp which
is closed on the sides by a loop-holed wall.
The example here given of a casemated caponniere is
from an Austrian authority. Fig. 36 is the plan ; Fig. 37,
a section and elevation on ab of one flank, and the end wall
of the corridor looking towards the court between the
flanks ; Fig. 38, a section and elevation along o' d' of the
corridor, mortar casemate, and triangular court. Figs. 37,
38, are on an enlarged scale.
This construction, if subject to artillery fire, as it will be
in the close attack, is readily destroyed. It is valuable only
to resist escalade or assault in the early stages of the attack.
To preserve it in condition to be effective for the last
stages of the defence has been the study of the advocates of
the polygonal system.
Tne latest forms differ from that described in having but
one tier of casemates, covered with earth which may be
^4 ELEMENTS OF PEBMANENT FOBTIFICATION.
arranged as a parapet, or simply as a protection to the
arches. The face wall of the casemates is protected from
fire by being set back so far from the heads of the arches,
that a shot coming from the crest of the glacis and pass-
ing just under the crown of the arch will strike the ground
below the embrasure. (Plate 1, Fig. 7.)
This requires, when tne exterior side is great, an arch of
considerable length, which by retaining the smoke of dis-
charge obstructs the view, and interferes with the ventila-
lation of the caponniere.
This difficulty is alleviated by leaving an opening between
the face wall and the tunnel-shaped arches for the escape of
smoke, and shielding the face wall by giving additional
height to the earth cover of the tunnel arches. (Plate 1,
Fig. 8.)
When these arches are subject to accurate battering fire the
debris from their heads will obstruct the fire of the capon-
niere guns, and when the heads are battered away the face
wall will be easily breached and rendered useless. The
advantage of the new over the old form consists in adding
to the time necessary for the reduction of the work.
For important works which justify the expense, armored
caponnieres, either stationary or revolving turrets, are pro-
posed. Their faces may be of sufficient strength to with-
stand the besieger's guns, or they may be raised to work
their guns and lowered in a pit to shield them from fire.
Their tops can only be struck obliquely in either case.
They will be more fully described hereafter.
27. Casemates on Iiand Fronts. Various modes
have, from time to time, been proposed for arranging de-
fensive casemates for the exterior defence of land fronts.
The difficulty in covering the masonry from the batteries of
the assailant has been the chief objection to these structures,
and is the more prominent as the fire of artillery becomes
more accurate, as such casemates would soon be ruined or
Tendered untenable by embrasure shots.
The Haxo casemate, named from its designer. Gen. Haxo,
has been extensively used. These casemates consist (Plate
6, Figs. 45, 46, 47, 48, and 49) of a series of arched bomb-
proof chambers closed in front by a thin mask wall which,
except around the embrasures through it, is covered from
the assailant's artillery by the parapet. To present but a
small surface of masonry to nre, the arches, which are
horizontal and perpendicular to the mask wall for the
greater portion of their length, descend towards the front,
ELEMENTS OF PERMANENT FORTIFICATION. 25
leaving where they join the mask wall just snfficient height
within for the service of the gun. To effect this the ante-
rior portion of the arch must be eonoidal in shape.
The piers of the arches are pierced with wide arched
openings which serve the double purpose of a communica-
tion between the casemates and to give the gun a wider
traverse for firing.
Embrasures are pierced in the parapet in prolongation of
those of the mask wall, and it is proposed to cover the small
portion of the masonry necessarily exposed by this arrange-
ment by placing several thicknesses of heavy timber in front
of it to receive the shot, or to case it with wrought-iron.
When the casemates serve simply for the cover of the
<»annon, the arches are covered with from 4 to 6 feet thick-
ness of earth, and are left open to the rear for the more
prompt escape of the smoke, and a ditch is sometimes made
just in rear of the casemates to catch bombs and limit the
eflEects of their explosion. When the arches are made
longer than for the service of the guns alone, the earthen
covering is sometimes arranged with a parapet to cover
<3annon in barbette, or for small-arms.
The example shown by the Figs, is from a French author-
ity. Fig. 45 is a plan on m n. Fig. 47 ; Fig. 46 a section
and interior* elevation towards the mask wall on o p, Fig.
47; and Fig. 47 a section and side elevation on r s. Figs. 45,
46.
In Figs. 48, 49 is shown an arrangement of two case-
mates of the Haxo kind from an Austrian authority. In
this case the masonry is covered on the flanks from enfi-
lading fire by earth. Fig. 48 is an interior elevation of the
arches, and the back wall that retains the earth on the sides.
Fig. 49 is a longitudinal section, and shows the manner of
covering the masonry in fiont and securing the earthen
embrasure by a timber facing.
The attempt to remedy the defects of the Haxo casemate
by strengthening the face, wall with iron and removing the
objectionable embrasure in the earthen parapet has led to
the development of the iron and steel constructions which
are applied to searcoast works, but which have been used
more sparingly on land fronts owing to their great expense
and the difficulty of finding a metal which wiu resist long-
continued direct battering. The latter difficulty may be
overcome by the use of inclined armor.
28. Mortar Casemates. In Fig. 50, PI. 6, is shown
a longitudinal section of a mortar casemate placed in rear
26 ELEMENTS OF PERMANENT FORTIFICATION.
of a parapet, by which it ifl covered from direct fire. The-
arch 18 covered, as in the preceding case, by earth, to break
the shock of shells. It rises towards the front to give
ample room for the shell in its flight. The casemates are
covered on their flanks from enfilading fire by an embank-
ment, and are partly closed bv a wall in the rear. A small
ditch is made in front of the chamber, and a slight wall
built within it, to give cover from the splinters of shells
falling between the parapet and the casemate. Arched
chambers are in some cases made beneath the mortar cham-
bers which serve as store-rooms and temporary magazines.
When these casemates are placed in rear of a portion of
the parapet but little exposed to direct fire, the thickness of
the parapet in front of them may be reduced, and the in-
terior slope be replaced by a breast-high wall along the
front of the casemates, in oixier to give better cover in flank
and from slant fire, by throwing forward the casemates more
under cover of the parapet
The example given is from the same authority as in the
preceding example of casemated caponnieres.
On faces exposed to plunging fire this casemate must be
lowered so that its arcn is protected by the parapet from
projectiles passing over it.
29. Oasemates for Water Fronts. In the casemated
batteries for sea-coast and harbor defences, the scarp or mask
walls of the chambers for the guns, being exposed to the
fire of ships alone, are not subject to the accurate breaching
fire which land fronts may be called upon to sustain.
Masonry walls could be built strong enough to resist single
shots from the ships' guns in use prior to about 1865-70»
Under these conditions were built our existing casemated
masonry forts, whose details are shown in Plates 5 and 6,
Figs. 40 to 44, inclusive.
With the increase in the power of ships' guns these walls
are easily penetrated, and they are no longer effective as a
defence. No modifications of these works have been made
in this country ; but in some English and Continental forts
the masonry fronts of the gun chambers only have been
replaced by iron shields, leaving the rest of the scarp wall of
masonry (a construction of doubtful value), and in others
the entire scarp wall has been built of iron, the original
masonry of the interior of the work only being retained.
In the newer casemated works, which are made with one
tier of artillery fire, the parts exposed to fire are of iron or
steel, the thickness of which is determined by the intensity
ELEMENTS OF PERMANENT FORTIFICATION. 27
and greater or less obliquity of the blow to which they are
liable to be subjected.
30- Turrets. The field of fire from casemates being
limited, and the exposure to hostile fire of the embrasures
and muzzles of the guns while loading objectionable, re-
volving turrets have been adapted to fortifications to remedy
these defects.
Turrets are particularly valuable for sites exposed to fire
from all sides, as by their construction they occupy little
space, give protection against plunging and reverse as well
as front fire. They command a wide field of fire, are in-
commoded by smoke no more than open defences, and lend
themselves to the use of the best possible appliances for
loading and working their guns. For fortifications, their
weight (which is objectionable on ships) is an advantage
when they are struck by heavy projectiles. The principal ob-
jection to them is the great cost not only of the turret itself^
but of the machinery for working it and of the substructure.
They have been made in the form of a vertical cylinder
or a truncated cone with a flat top, an oblate spheroid, with
the embrasures just above the equatorial circumference and
a spherical segment witli the embrasures pierced horizon-
tally through me dome-shaped top.
"the first forms have the advantage of an easy mechanical
construction with either rolled or forged plates, and the dis-
advantage that they may be struck in a direction nearly or
quite normal to the surface.
The spheroid can only be made of cast metal.
The dome can be made of wrought-iron, steel, or com*
pound plates.
The last two forms can only be struck obliquely by direct
fire. More detailed descriptions of some oi these will be
given farther on.
31. Embrasures. The form, dimensions, and construc-
tion of embrasures in mask walls present a problem which
has offered to engineers no little difficulty in finding a satis-
factory solution by which the best cover could be given to
the guns and men by exposing the least surface to embrasure
shots, whilst the guns snould receive a suitable traverse to
command a wide field of fire.
The most perfect type of masonry embrasure was that
used in the latest casemates constructed in this country ; it
was designed by General Totten, of the U. S. Ei^neers,
and is known by his name. It is shown in Plate 8, Figs. 61^
62, 63, and 64.
28 ELEMENTS OF PEBMANENT FORTIFICATION,
In iron construction, the problem is more simple, and has
been solved in several ways, all having in view the greatest
field of fire with the smallest opening. This object is best
accomplished by pivoting the gun, for both horizontal and
vertical movement, as nearly as possible at the centre of
the embrasure.
When the gun is allowed to recoil, the carriage must be so
constructed as to allow it to move back without jamming in
the embrasure. Some of the most recently devised carriages
hold the gun in position and prevent recoil by suitable
strong recoil bars and arcs, and secure the muzzle in the
embrasure either with a ring and trunnions (Griison's
method), or by a spherical enlargement on the gun and
corresponding socket in the embrasure (Krupp).
In others the recoil is prevented by the direct resistance
of the pintle or platform. The muzzle of the gun should
project in all cases not less than one foot beyond the em-
brasure ; frequently it projects much more.
In revolving turrets the gun needs no horizontal traverse,
and can be worked in an embrasure of the Griison pattern,
whose height is about once and a half the diameter of the
gun at the embrasure, and whose breadth is about two inches
greater than this diameter.
The guns are aimed by sights on the chase, by sighting
through the bore, by peep holes over the embrasure, or by
sights placed on top of the turret or casemate. All the
guns 01 a battery are sometimes pointed by using fixed
horizontal and vertical arcs properly graduated, and pointers
attached to the gun ; the sighting being done by the use
of a sight-bar or telescope mounted on a suitable lookout,
and provided with an arc and pointer, whose readings,
properly corrected for parallax and tabulated, give for each
gun its correct pointing.
32. Bomb-proof Buildings. Oasemated bomb-proof
-quarters are indispensable to the safety and comfort of the
garrison during siege, or any prolonged attack for the an-
noyance or reduction of the work by a bombardment. In
«ome cases advantage is taken of a scarp wall, on a land
front, which is well covered by a glacis or other face cover
to form in its rear quarters of this character. In others
they are made under the terre-plein and traverses where
their entrances and face-walls are not exposed to fire ; and
when suflScient room cannot be obtained in these places
constructions similar to traverses may be built to. cover ad-
ditional space. The arches to resist splinters only may be 3
ELEMENTS OF PERMAMrENT FORTIFICATION, 29
feet thick, covered with 6 feet of earth. If subject to a fire
of "torpedo shells," Brialmont recommends a thickness
of arch of from 6 to 10 feet. Whenever the plan of the
work admits of it, quarters of this kind should be arranged
for defence, by being pierced with loop-holes and even with
embrasures for cannon. Defensive casemated quarters and
keeps have formed a prominent feature in the German
school of permanent fortifications, but where retained, they
will be modified so as to expose no masonry to artillery fire,
and will serve only as quarters, and as a last defence and
refuge for the garrison when the work is stormed. Some
modern forts have been built without keeps. A fulfilment
of the conditions requisite to a strong defence, however, re-
quires that the interior of the work be swept by the fire from
galleries and casemates into which the garrison may retire
when the parapet of the work is carried either by surprise
or assault. This last defence may drive out the assailants
and preserve the work. It will in any case afford the garri-
son an opportunity to surrender without the great losses
which follow a successful assault upon an open work. Be-
sides, it will add largely to the morale of the garrison, and
lead them to hold the parapet longer than they would with*
out it.
33. Foi^der Magazine. Powder magazines, when
practicable, should be placed below the surface of the
ground, and should never be exposed to the direct fire of
flie enemy. The structures for this purpose are built with
strong, full centre bomb-proof brick arches, supported on
heavy stone piers which form the outward walls, and to
which interior buttresses are sometimes added. The cap-
ping of the arches is covered with from 10 to 16 feet of sol-
idly packed earth. The interior of the magazine, the fioors,
and the doors and windows are built with a view to security
from fire; and to preserve the powder from dampness^
by a good system of drainage around the foundations, and
01 ventilation by means of air-holes made through the piers^
and panels of copper pierced with small holes placed in the
doors. No iron or steel fastening or sheeting is allowed in
any part of the structure; and m arranging the air-holes
through the piers they receive a broken direction, and have
a copper mesh-work placed across them, to prevent any
combustible material, or rats or mice, penetrating to the in-
terior of the magazine.
In large works the magazines are isolated as far as practi-
cable from the enceinte, so as not to endanger it should an
80 ELEMENTS OF PERMAKBKT F0HTIFICATI02Sr.
accidental explosion take place. The magazine is enclosed
by a strong high wall for security, and is provided with
lightning-rods. In small works they are placed in the posi-
tion least exposed to the assailanc's nre,and given the great-
est amount of cover which can be obtained.
V.
COMMUNICATIONS.
34. General Remarks. The communications form a
very important element in the defence of permanent works.
The size and disposition of the communications should vary
with the character of the work in which they are placed.
In small works, which from the size of their garrisons are
calculated to make only a strictly passive defence, commu-
nications of just sufficient dimensions for the passage of the
troops from point to point will serve every purpose, and can
be more easily barricaded and otherwise deiended.
But for large works having full garrisons, the communi-
cations should be such that sorties of all arms and in large
bodies can be quickly made. With communications of this
character a besieging force would be constrained to adopt
extraordinary measures of safety, keeping large guards in
the trenches to secure them from such sorties, to wiich they
would be continually exposed.
36. All communications, to serve properly their ends,
should fulfil the following conditions :
1. They should never, from their position, compromise
the safety of the enceinte.
Frequent instances could be cited of works which have
been surprised by an enemy obtaining possession of the
gates. Therefore too many precautions cannot be taken to
secure the principal outlet from the body of the place from
similar attempts.
2. They should admit of a convenient circulation of the
hesieged.
To subserve this purpose, the dimensions, slopes, etc., of
the posterns, ramps, and other similar works, should be con-
venient for the service to which they are applied, and they
should be placed in such positions as leaa directly to the
point to be arrived at.
3. The position chosen for amy communicaUon should he
ELEMENTS OF PEBMAKEKT FORTIFICATION. 31
^Sfmh that when am, enemy gets possession of it^ he may ob-
tain no advantage hy it.
To be useless to an enemy, the comraunication, when in
his possession, should not offer a shelter for his works ; nor
•enable him to carry them on with more ease. This end will
be obtained by placing the communications in a position to
be enfiladed by the fire of the works in their rear, and so
arranging them as to preserve the counterscarp wall un-
broken.
4. TTie communications shovM he covered from every
j>oint where an enemy might establish himself during the
whole period that they can be of service to the besieged;
and they should be swept by the jure of the enceinte.
Without these precautions, an enemy might cut off all
•communication from the enceinte with the outworks ; and
in case of retreat, the troops could not derive any assistance
irom the enceinte, if he attempted to press upon them.
5. They should be so placed as not to compromise the re-
treat of the troops.
This is effected by placing the communication in the re-
•enterings, which are the most secure points ; as an enemy
to arrive at them will have to brave a powerful column of
fiank fire. Barriers, gates, and movable bridges of timber
should be placed at suitable points, to cut off one communi-
-cation from another ; and thus arrest the progress of a pur-
suing enemy.
6. Finally J each work shovM be independent of emery
<iommunication^ except that one destinedjor its pa/rticrda/r
use.
If this condition be not fulfilled, a work may sometimes
be captured by an enemy obtaining possession of a com-
munication passing through it, but designed for the service
of some other work.
36. Ramps. The principal communications consist of
ramps^ stairs^ posterns^ gateways^ bridges^ and, for wet
•ditches, dikes. The width of ramps at top for the service
•of the artillery and other vehicles may be from 10 to 15
feet, and their inclination from ^ to 4z^ or less, depending
on the difference of level to be overcome. They are usu-
ally placed in positions where they will occupy the least
room on the parade, as along the rampart slope of the
•enceinte. As a general rule, tneir side slopes are of earth ;
but where it is desirable to economize room on the parade,
the side slopes are replaced on one or both sides by a wall
which sustains the earth of the ramp. When ramps serve
32 ELEMENTS OF PEBMANENT FORTIFICATIOK.
for infantry alone their width may be rednced to 6 feet, and
in some cases to 4 feet.
37. Stairs. Except for temporary purposes, stairs ar&
constructed of stone ; each step being a solid block which
is 6 feet long in the clear ; its breadth at top or the tread
12 inches, and its height or rise 8 inches. Stairs are usually
placed along the counterscarp) and gorge walls of the out-
works, forming a communication, for infentry only, between
the ditch and the terre-plein of the work to which they lead..
They are also used within the enceinte in positions where
there is not sufficient room for ramps, where bomb-proof
cover is required, or where, for greater security from sur-
prise, it is desirable to present a narrower and more difficult
defile to the assailant. In cases where room is wanting, and
the communication not in habitual use, the width of the
stair may be reduced to 4 feet.
38. Fostems. Posterns are arched bomb-proof passage-
ways constructed under the terre-pleins and ramparts, form-
ing subterranean communications between the parade and
the enceinte ditch, or between the ditches and the interior of
the outworks. The width and height of the interior of
posterns depend upon the use to which the communication
IS to be applied. For artillery the width is usually taken at
10 feet, and the height under the crown or key of the arch
at least 8 feet. Posterns for infantry may be only from &
to 4 feet wide, and from 6 feet 6 inches to 8 feet high
under the crown of the arch. The thickness of the piers of
the arches is generally taken at about half the width of th&
postern. The arches are from 2 to 3 feet thick. As any
m jury to the arch from the bursting of a shell over it might
obstruct the communication, the arch should be covered
with a thickness of earth sufficient to thoroughly protect it^
A strong wooden door is placed at each outlet of the postern
to secure it against surprise. The doorway in posterns for
the service oi artillery should be of just sufficient height for
the convenient passage of a gun; about 7 feet for each
dimension is usually allowed for this purpose.
The most important postern is the one leading from the
parade to the enceinte ditch. This generally receives a
width of 12 feet and the same height under the crown. For
greater security from surprise, its outlet at the enceinte
ditch is at least 6 feet above the bottom of the ditch, this,
difference of level being overcome by means of a temporary
wooden ramp which receives an inclination of at least i»
With a like object, besides two strong doors at the two ends.
ELEMENTS OF PEBMAITENT FORTIFICATIOiq'. 33
of the postern, there is a partition of masonry about mid-
way between the two ends, which is pierced with a doorway
of the same size as the doorways of the ends, and closed by
a strong door which, as well as the partition wall, is loop-
holed for musketry.
In cases where the postern forms the main entrance to the
work, an arched chamber is placed on one side of it, at the
outlet, which serves as a guard-room for a few men, to
secure the outlet from surprise. The wall between this
chamber and the postern is loop-holed, so that a fire can be
brought to bear on the doorway of the postern ; and as a
further precaution against surprise a machicoulis defence is
sometimes arranged at the top of the scarp wall just above
the doorway of the postern.
39. Gate"way. In works with large garrisons, where
the means of frequent communication with the exterior are
requisite, posterns of ordinary dimensions are found not to
afford a sufficient convenience for the daily wants. In such
cases a passage-way of sufficient width to admit of at least
a single carnage-road with narrow foot-paths on each side
has to be opened through the rampart, which, whenever it
is practicable to do so, should be arched and covered with
earth to render it bomb-proof. The passage-way should
for security have the bottom of its outlet at least twelve
feet above the bottom of the enceinte ditch ; and when
this difference of level cannot be obtained the main ditch
should be deepened sufficiently for the purpose below the
outlet. A gateway of sufficient height and width for the
passage of the ordinary vehicles for the service of the gar-
rison is made through the scarp-wall. This gateway is
arched at top, where a machicoulis defence may also be
arranged to guard the outlet on the exterior.
The communication across the enceinte ditch leading from
the gateway is usuallj^ an ordinary wooden bridge built on
piles. The bay of this bridge at the gateway is spanned by
a drawbridge of timber, which when drawn up closes and
secnres the gateway. This drawbridge is manoeuvred by
some of the usual mechanisms employed for this purpose.
40. Port-Oullis. When the gateway is not preceded
by a ditch, and is therefore without a drawbridge, a barrier,
termed 2l port-GuUis^ which can be lowered or raised verti-
cally by machinery, is sometimes added to secure the pas-
sage-way from surprise. The ancient port-cuUis was a
framework of heavy beams, placed vertically, leaving a few
inches only between each pair of beams. These vertical
3
84 IXAMBKTS 09 PEBHAVBHT FOBTXVtCATIOir.
beams were either solidlj conflned between horizontal
beams, or clamping-pieces in pairs; or else they were so
arranged that they conld slide npwards between the clamp-
ing.pieces. Each of the vertical beams was shod at the
bottom with a strong-pointed iron shoe. The horizontal
pieces were framed securely with two heavy vertical beams
that formed the sides of the frame, and were fitted into
vertical grooves made in the side walls of the passage-way
in which the frame could slide when raised or lowered. By
arranging the vertical beams to slide upwards between the
clamping pieces, it enabled the passage-way to be closed in
cases where an obstruction might be designedly placed be-
low the port-cuUis to prevent this being done ; as the beams
which meet the obstruction would be pushed upwards,
whilst the others would fall to their ordinary level and close
the passage-way on each side of the obstruction.
In the works recently constructed with us the port-cullis,
and even the doors preceding them have, been constructed
of a strong open lattice-work of wrought-iron bars bolted
strongly to the wrought-iron uprights and cross pieces,
formmg the framework of the lattice. This is a great im-
provement for these purposes, both as to durability and de-
fence.
Passage-ways of this description should be secured by all
the means at an engineer's disposal. A large guard-room,
with loop-holes bearing on the passage, shouH be erected on
one side, near the gateway ; and if the enceinte is a simple
one, without outworks beyond its ditch, a small lunette, or
redan, should be constructed beyond the counterscarp, form-
ing a tete-de-pont, for the security of the bridge from sur-
prise, and which in connection with the glacis protects it
from artillery and infantry fire.
The drawbridge, which for convenience of manoeuvring
should not be longer than 12 feet, is constructed in the
usual mode.
"When passages through the ramparts are provided for
railroads, the necessary openings are made, the ditch is
crossed by a bridge, usually arched or of iron, with a draw
span, and all possible precautions are taken to prevent these
openings from becoming weak points in the defence.
BIiBKBinS 09 PEBKAVSNI lOBTIFIOAIZOK. 85
VI.
ENCEINTES.
41. The most simple mode of fortifying a position in a
^permanent manner consists in inclosing it witn a rampart
surmounted by a parapet, with a ditch the scarp of which
when dry is revetted with masonry, and so covered by an
earthen mask that it cannot be breached except by batteries
placed on the border of the counterscarp.
This line of fortification enclosing the position is termed
the enceinte^ the body of the place or the mcmi inclqaure.
The ffcneral outline of the enceinte may be curvUinea/r^
or 2l poVygoTial figure of any character.
42. System of Fortification. Although an infinite
^iiversity of figures may thus be presented in the outline or
plan of the enceinte, they may all be classed under four
neads, to each of which engineers generally have applied
the term system of fortification.
These four classes are, 1, the drcuLa/r or curvilinear
system f 2, the polygonal or caponniere system^' 3, the
tena4Ued system; 4, the bastionea system.
The term method of fortification is now usually applied
to the manner of fortifying which is generally prevalent
in any country ; or to the mode adopted by any individual,
as the Germain method ; VoAiban^s m^thod^ etc.
OirciQax System. The circular system consists of an
enceinte, the pTian of which is circular or curvilinear.
Polygonal System. In the polygonal system the plan
\r either a polygon with salient angles alone, PI. 8, Fig.
T2, each side of which, a a, is flanked by a casemated capon-
niere, c, placed in the ditch, d, and midway between the
two salients, a ; or else each side of the polygon is broken
inwards at the centre, so as to form a slight reentering, PI.
8, Figs. 73, 74, 75, 76, 77, to procure a casemated flanking
arrangement, f f, for the caponnieres, c, which occupy
these reenterings, and also, in some cases, to flank works in
advance of the enceinte.
Tenailled System. The tenailled system, PI. 8, Fig.
78, consists of a tenailled line, the reentering angles of
which are between 90° and 100°, and the salient angles not
less than 60°.
36 ELEMENTS OF PERMANENT FORTIFICATION.
Bastioned System. In the bastioned system, Fig. 79^
the bastion usually consists of two faces and two flanks, the
scarps of each of which are plane surfaces.
In many of the older fortifications, and in a few of the
more recent works in Europe, the flank is broken ; the por-
tion of it at the shoulder angle forming a projecting mass
which is termed an oriUon^ whiUt the portion between the
orillon and the enceinte curtain is retired, or brought in
towards the interior of the bastion, and is thus partially
covered by the orillon from fire, except in the prolongation
of the enceinte ditch. In some cases the plan of the orillon
as well as that of the retired flank is curvilinear; in others
they are both rectilinear.
43. General Remarks. Whatever system may be
adopted for the enceinte, there are certain conditions, in
addition to those already laid down for all permanent works,,
which it must satisfy to render it effective :
1. It should ha/ve a steep revetted scarp; unhroken on
all sides except for the necessary openings for communica-
tions ; thoroughly flanked throughout by cannon and
small-arms ; a/nd of sufficient height to prevent all ordinary
attempts at escalade.
2. Th^ scarp should he so covered by earthen or other
masks that it cannot be reached by the projectiles of a/n as-
sailant from any position exterior* to these masks.
3. The parapet and interior covered shelters should be
proof against solid and hollow loaded projectiles.
4. The parapet should command all the site amd out-
works exterior to the enceinte am,d within range of its guns^
and sweep iliem with fronts Jlank^ and cross-fires when pos-
sible.
5. As far as praxiticahle^ the principal lines ofthepa/ra-
pet should recevoe such directions^ that the assailant ca/n-
not take up positions to enfilade them.
Every enceinte, whatever be the system adopted, will be
more or less effective as these conditions are more or lesft
complied with in its arrangement.
VII.
OUTWORKS.
44. A work consisting of an enceinte alone is more or
less exposed to surprise, as it must have outlets of some
ELEMENTS OF PERMANENT FORTIFICATION. 37
^description to keep up a communication with the exterior,
and a bridge, or other means for crossing the ditch.
But this is not the only defect of a Fortification of this
simple character ; for having no covers beyond the ditch
for its garrison, their action must be restricted to what may
be termed a passive resistance alone; in any attempt to
operate on the exterior, they are exposed to fire as soon as
tney emerge from the ditch, and m a retreat towards the
work, if closely pursued by the assailant, they will not only
run the risk of being cut off, but a retreat under such cir-
<;umstances may lead to the capture of the work itself, by
the assailant being enabled to enter it with the retreating
force.
To provide against dangers of so grave a character, engi-
neers have devised other defences oeyond the ditch, and
which they have placed in immediate defensive relations
with the enceinte, being under its fire, and in positions
where, if assaulted, they can be readily succored by the gar-
rison. To this class of exterior defences the term outworks
has been applied.
From their position, exterior ro the enceinte, and from
their angular form, so as to be flanked by it, the outworks,
with the enceinte, form salient and reentering parts, which
are very favorable to the security of sortie parties, in re-
tiring ; and as, if properly arranged, the assailant must take
them in succession, they will greatly prolong the defence, by
forcing him to a great development of his trenches ; through
which, in some oi the positions he will be obliged to occupy,
he will be the enveloped party. Besides this, he will be
obliged to establish breacn batteries against each work in
succession — always a diflScult and perilous task.
46. The outworks should satisfy the following conditions
to render them effective and secure :
1. They should have revetted scarps of sufficient height
to secv^e them from any ordinary open assault.
2. As far as practicable their scarps should he fxmked
hy the encei/ntey and be masked from the positions of the
assailants batteries.
3. Their parapets and covered shelters should be shot-
proof
4. Those which a/re most retired should command those
in ad/oance ; and whenever this ca/nnot be done^ the re-
tired work should be defiled from, the one in advance by
which it is commanded.
5. In any combination of outworks the dispositions
38 ELEMENTS OF PERMANENT FORTIFICATION.
should be such that the more advanced ones shall faU intct
the hands of the assailant hefore he will be ahle to gainpos-^
session of the more retired.
6. The commwnications should he am/ple^ a/ad satisfy ths
general conditions for these elements.
46. The works which come under this head are the
covered-way^ the tenaUle^ the demi-lune^ the countergua/rdj
the redovht or reduity the tenaillon^ the hom-workj and the
crown-work.
47. Covered-Way. The covered-way, as its name im-
ports, is an open corridor or passage, masked from the as-
sailant's view by an embankment, which borders the ditch
of the enceinte alone when there are no other outworks ;
but, in the contrary case, also envelops the ditches of these,
forming thus a continuous covered line of communication
around the fortification.
The covering embankment itself is arranged towards the
covered-way like an ordinary parapet, and it receives on the
exterior a gentle slope or glacis.
By this arrangement the garrison have a covered position
beyond the ditch where they can assemble with safety either
for the purpose of making a sortie, or to guard the ditches
and the communications across them; and which affords
them also a secure point of retreat if repulsed in a sortie, as^
a reserve left in the covered-way will be at hand to check
the pursuit by their fire, and enable the retreating party to
gain the enceinte.
48. Flaces-of-Arms. The covered-way from the direc-
tion given to the counterscarps of the enceinte and out-
works, forms a line of communication with salient and re-
entering parts. Pis. 8, 9, Figs. 80 to 85.
The salient portions, s, are termed salient places-ofa/rms ^
and the reentering parts the reentervng pkbcesof-arms.
The salient places-of-arms, it will be seen, result from the
general plan of the covered-way ; but the reentering places-
of-arms are formed by changing the directions of the two
branches where they form the reenterings, b, so as to
make a salient within the reenterings ; thus enlarging the
covered-way at these points and producing a flanking ar-
rangement, by which the glacis can be swept, and a cross-fire
be brought to bear on the ground in advance of the salients.
49. Traverses. The covered-way, from its position,
and the usually slight command given to the crest of it&t
glacis, is very much exposed to the effects of an enfiladin^^
fire.
ELEMfLNTS OF PEBMAIfBNT FOBTIFICATIOK. 3&
With a view to remedy this defect, and also to enable
the garrison to dispute foot bj foot the possession of this
outwork by the assailant, earthen masks, formed like an
ordinary parapet and termed traverses^ are thrown up across
it. The traverses usually extend to the counterscarp, the
wall of which is built up to sustain them.
At the end, towards the glacis, a passage, or defile, is left
between them and the covering embankment, to admit of a
free communication throughout the covered-way.
60. Tenaille. The tenaille is a low work placed in the
reentering formed in the enceinte ditch by the curtain and
flanks of the bastioned system, being isolated by a ditch
between it and these parts of the enceinte. Its chief pur-
pose is to serve as a mask, covering the scarp walls of this
reentering from fire, as well as the outletfi( to the enceinte
ditch, which are usually placed in the centre of the curtains.
The tenaille has received various forms from engineers.
In some cases it has been made with two faces or wings,
making a reentering angle opposite the centre of the en-
ceinte curtain. In others the two wings, instead of being
prolonged until they meet, are connected by a short curtain
parallel to that of the enceinte. In some examples it has
the form of a small bastioned front. In others it consists
of two flanks connected by a curtain. These flanks in some
cases have been casemated for guns and mortars. The
tenaille is usually revetted with masonry both in front and
rear. In some cases the ends alone, towards the flanks of
the enceinte, are revetted, the intermediate portions con-
sisting of an ordinary earthen parapet without either scarp
or gorge wall.
61. Demi-lune. The demi-lune, PI. 9, Figs. 81, 82, 83,
84, Is a work in the form of a redan, d, placed in front of
the enceinte curtain, which it masks from fire, as well as a
portion of each face of the enceinte, at the shoulder angles
of the bastions. It is isolated from the enceinte by the
main ditch. From its importance the scarp and gorge of
the demi-lune are generally revetted, though in some cases
the revetment has been omitted.
This work is also called the ravelin.
62. Oounterguaxd. The counterguard is an isolated
work, c. Fig. 80, in the form of a redan, which envelops the
faces of a bajstion or other salient. In some cases it con-
sists simply of an earthen mask having the profile of an
ordinary parapet ; but it is usually revetted both in front
and rear.
40 ELEMENTS OF PERMANENT FORTIFICATION.
63. Redoubts. The term redoubt, or reduit^ is ap-
plied to outworks placed within other outworks ; their object
being to strengthen the defence of the principal work.
A work of this class is usually placed within the demi-
lune, and is termed the demUv/ne redovht. Small works
of this kind are also placed in the salient and reentering
places-of-arms of the covered-wa^, and are termed the re-
doubt of the salient^ or reentering pldceof-a/rms. These
redoubts are in some cases simple earthen works ; in others
they are revetted; and in others casemated both for the
service of artillery and small-arms.
64. Tenaillon. The term tenaiHon, PI. 9, Fig. 81, is
applied to a kind of face cover, or counterguard, t, of the
demi-lune. It is only to be met with in some of the old for-
tified places of Europe, and was added to give more strength
to fronts where the demi-lune was too small.
66. Horn-Work. The horn- work, PI. 9, Fig. 82, usually
consists of a bastioned front, h, with the ordinary outworks,
having two long branches, f f, or wings, which rest upon
two adjacent bastions, or two adjacent demi-lunes, dd, of
the enceinte; its covered- way forming with that of the
enceinte a continuous line of communication. The object
of this outwork is to strengthen a salient or other weak por-
tion of the enceinte.
66. Crown- Work. The crown- work, PI. 9, Fig. 83,
consists of two or more bastioned fronts, o, with their out-
works, placed in front of some portion of the enceinte, to
give it additional strength. It is terminated like the horn-
work by two wings, ff, which rest either upon the enceinte,
or upon two demilunes, dd. Its covered-way, like that of
the horn-work, forms a continuous communication with that
of the enceinte.
VIII.
ADVANCED AND DETACHED WORKS.
57. The term advanced works is applied to such works
as, placed beyond the outworks, are still in defensive rela-
tions with them and the enceinte, by being so brought
under the fire of either the enceinte or the outworks that
the ground in advance of them will be swept by this fire ;
their ditches flanked by it ; and their interior so exposed to
it that, if the work were seized by an open assault, the
assailant could be driven from, it by this fire.
ELEMENTS OF PERMANENT FORTIFICATION. 41
They are usually in the form of redans or lunettes, and
in some cases horn and crown works, depending on the ex-
tent of ground that it may be thought necessary to occupy
ivith them.
68. Advanced works are placed in positions which the
assailant rumt necessarily make himself master of before he
can approach nearer to the main work ; or on points which
overlook ground that cannot be swept by the fire of the
-enceinte; and sometimes on points which, inaccessible to
the assailant, give good position from which a flank fire can
be brought to bear upon ground over which the assailant
will be obliged to make his approaches.
Restricted to these purposes, an advanced work may be of
great value in prolonging the defence ; and every precau-
tion should be taken to secure the work from a surprise,
and to give its garrison a safe means of communication with
the outworks upon which they can retire when forced to
abandon their work.
In works of great extent, with full and strong garrisons,
advanced works, by judicious combination with the works
in their rear, may greatly enlarge the field of action of the
farrison ; keeping the assailant at a distance, and annoying
im by frequent sorties in large bodies, made under the
protection of the outworks.
In Plate 9, Fig. 84, is an advanced work, l, fianked by
the demi-lunes, d, of the enceinte. The plan of this work is
a lunette with its covered-way and places-of-arms, b and s.
69. Detached works are those wnich, although having an
important bearing on the defence of the main work, are so
far from it as to have to depend solely on their own strength
in case of assault.
Depending solely on their own strength, they should have
a revetted scarp and counterscarp of sumcient height to pre-
sent great difficulties to an open assault, and liave their
ditches flanked either from the parapet of the work itself or
by caponnieres or by counterscarp galleries.
Detached works may be either of a polygonal or bastioned
form, depending upon the extent of ground to be occupied ;
the former being more suitable to small works to which the
bastioned form does not lend itself.
They belong to the class of works termed forts^ as dis-
tinguished from fortresses.
They are used to occupy ground like commanding heights,
which, although not within good sweep of the fire oi the
main work, is still within range of the heaviest calibres of
42 ELEMENTS OF PEBMANENT FORTIFICATION.
the assailant^ and which if occupied by him would prove a
source of serious annoyance to the work.
The more favorite mode now among engineers for the de-
fensive works of cities is to enclose them with a continuous^
enceinte of sufficient strength to repel an open assault, or
to retain this enceinte if it already exists and to occupy
positions in advance of the main work, beyond extreme
cannon-range, by a line of forts so strong that they can only
be reduced by regular siege, and so placed that one or more
must be taken before the assailant can approach the main
work. In some cases a second line is established outside
the first, and the whole area within the exterior cordon
partakes of the nature of an intrenched camp.
IX.
INTERIOR RETRENCHMENTS.
60. Besides the works exterior to the enceinte, the object
of which is to retard the assailant in his attempts to enter
it by breaching, engineers have placed within it other works
which, in some cases, are designed simply to enable the
garrison to make an eflEectual defence of the breach, when
the assault upon it is made, and give them a secure point of
retreat and safety when driven from it ; and in others these
interior works are chiefly designed to bring plunging fire to
bear on the assailant's siege works exterior to the enceinte.
The former class, intended for the defence of the breach
alone, are termed interior retrenchments; and the latter
cavaliers.
61. Interior retrenchments in the bastioned system are
either placed within the bastions, which are the parts of the
enceinte usually breached, or in rear of their gorges. Those
which aj*e placed within the bastions extend across them
either between the faces or between the flanks. When placed
at the gorge they connect the two adjacent curtains.
The plan of these works varies with their position, the
size of the bastions, or the more or less openness of their
salient angles.
In small bastions with acute salients, when the retrench-
ment rests upon the faces, it usually receives the form of a
tenaille or inverted redan, the angle of the tenaille being
about 100°. When the bastions are large and the salient
angle quite open or obtuse, the retrenchment may receive
IBLBK£KTS 07 PEBIULHTBKT POBTmCAXIOir. 4$
the form of a small bastion front, PL 9, Fig. 85, resting
npon the faces.
Either of these forms may in like manner be used, when
the retrenchment rests upon the flanks of the bastion. But
as this position enables a retrenchment of the form of an
ordinary redan to have its ditches swept by the fire of the
flanks of the adjacent bastions, this form is in some cases
used in preference.
When placed between two curtains at the gorge of a
bastion the plan of the retrenchment is always a bastioned
front.
In the polygonal system, nntil within a few years, the in-
terior retrenchments were high caseinated defensive bar-
racks or keeps arranged to fire over the parapet from their
upper tiers, and to sweep the terre-pleins and parade from
their lower ones. They are now made of less height and
their masonry is covered from fire, forming bomb-proof de-
fensive barracks as previously described.
62. Cavaliers are placed either upon the curtains or within
the bastions. The latter is the more usual position selected
for them. Their plan in this position is usually that of a
lunette, the faces and flanks of which are parallel to those
of the enveloping bastion. Cavaliers receive a considerable
command over tne parapet of the enceinte, and, in some
cases, they are arranged with a tier of casemated fire, above
which is an open battery.
In polygonal works the cavaliers are generally placed at
the salients and in the middle of the faces, when they are
long, protecting the faces from enfilade and affording cover
for magazines and quarters, as well as giving a plunging
fire on the ground in front. In some large and important
works it is proposed to provide them with iron or steel
turrets.
Interior retrenchments and cavaliers are usually construct-
ed with a revetted scarp and counterscarp to secure them
from an open assault ; and, in some cases, a covered-way^
with a small reentering place-of-arms, b, PI. 9, Fig. 85,.
closed by traverses, is arranged in advance of the ditch, to
insure the safe retreat of the garrison when driven from the
breach.
44 ELEMENTS OF PERMATjEyT FOBTIPICATIOiEr.
CHAPTEE 11.
SYSTEMS OF FORTIFIOATION.
In the discussion of the relative merits of different systems
of fortification, their capacity to resist the close attack of the
besiegers formerly had the greatest weight.
Modem methods have given to the distant attack a value
and eflSciency much greater than it formerly had ; so ffreat
that in some cases it alone determines the result ox the
.siege.
The conduct of recent sieges, notably that of Strasburg
in 1870, in which the close attack was pushed up to occupy*
ing the advanced works, crowning the covered-way, and
breaching the main enceinte, have snown, however, that the
<jlose attack may not be entirely a thing of the past, and
that proper dispositions to meet it must still be made. The
relative advantages of the different systems must then be
<ietermined, not only by the character of the site and size ot
the work, but also by the probable nature of the attack and
xlefence, and the other considerations which arise in each
particular case.
I.
BASTIONED SYSTEM.
63. A bastioned enceinte consists of a series of bastions
ivhich occupy the salient angles of the polygon within which
the enceinte is inclosed ; the flanks of the bastions being
visually connected by straight curtains.
The sides of the polygon which connect the salient angles
of the bastions are termed the exterior sideSy in contradis-
tinction to the sides of an interior polygon which, being
parallel to the first and occupying the positions of the cur-
tains, are termed the interior sides.
The bastioned enceinte, when its relief and plan are
-suitably arranged, possesses the advantage of having its
ELEMENTS OP PERMANENT POBTIPICATIOIS'. 4&
ditches thoroughly swept from within the enceinte itself,
thus securing the flanting arrangement of the scarp; of
bringing a cross and flank fire to bear upon the approaches
on the salients of the enceinte, and furnishing a strong-
direct and cross fire upon the site in advance of the curtains
and the faces of the bastions.
64. The principal objections urged against the bastioned
system are :
1. That its chief characteristic, a perfect flanking disposi-
tion for the entire line of the scarp, is attainable only under
certain relations between the requisite relief for a permanent
work and the lengths of the exterior side and curtain, which
therefore restricts it in its application to fortifications in
which these relations exist.
2. That, in order to secure a sufficient length of flank for
an effective flanking disposition, the angle between the faca
of the bastion and tne exterior side, termed the diminished
angle of the polygon, has to be made so great as to decrease
considerably the space inclosed within the polygon, whilst
the development of the line of the enceinte is greatly in-
creased by it.
3. That the direction necessarily given to the faces fronif
this cause throws their prolon^tions in positions very favor-
able to the erection of enfilading batteries against them.
4. That the flanks, upon which the whole system is based,
lie in positions in which, like the faces, they can be not only
easily enfiladed, but are further exposed to a reverse fire
from shot which may pass over the parapet of the faces a»
well as the opposite flank, or even to being breached by fira
intended only to enfilade the face in their front.
5. And that these objections are the stronger as the sali-
ent angles of the polygon are smaller or as the number of
sides is decreased.
6. That by reason of objections 3 and 4, the artillery of
the faces, fianks and demi-lune is not able to withstand the
distant enfilade fire of the besieger, and in consequence it
has little or no value in retarding his approach until the
third parallel is reached, when this distant fire ceases in order
to avoid injuring his own men.
That this fact reduces the value of the artillery defence to
a minimum, and restricts the size of the fronts to those whidi
can be defended by infantry fire.
Besides these objections, which to a certain extent are well
founded, where the defensive arrangements are chiefiy open.
40 BLEMBITTB OF PIQBMANSHT FOBTIFIGATEOIT.
«e is the case in most land fronts, others have been niMd
jiffainst this system, which, being rather of a comparative
character, as showing the advantages of other systems over
this, will best be examined elsewhere.
n.
vauban's fibst method.
66. Vauban, born 1632, died 1707, has left examples of
three different methods in the places planned by him. The
fortress of New Brisac is fortified after his third method ;
those of Landau and Belf ort after his second ; but the greater
part of the places fortified by him are planned according to
his first or earliest method.
66. Profile of Enceinte. In the profile of this method,
Pig. 1, PL 10, the scarp wall is 36 feet high, its slope being
five perpendicular to one of base ; surmounting this is an*
other wall from 4 to 6 feet high^ the object oi which is to
sustain the exterior of the parapet. The parapet is 18 feet
thick, the superior slope being ^; the interior crest is 8
feet above the terre-plein, which is 42 feet in width. The
mean command of tne interior crest above the site is about
^6 feet. The bottom of the ditch is about 17i feet below
the site.
67. Flan of Enceinte. Yauban adopted no arbitrary
or invariable combination of parts in his methods. His
great excellence as an engineer is shown in the skill with
which he adapted the fortifications he planned to the de-
fensive requirements of the sites ; selecting long, medium,
or short exterior sides, and varying the length and directions
of the faces and fianks so as to procure the best command
over the exterior ground, and to withdraw these parts from
the enfilading fire of the assailant.
In his works, however, he has generally taken 360 yards
as the greatest limit of the exterior side ; the perpendicular
of the front 4 when the polygon is a square ; ^ for the
pentagon ; and ^ for all higher polygons.
With these starting-points he procured diminished angles
which gave more than 60° to the salient angles of the bas-
tions in all cases, and fianks of suitable length both to fiank
the main ditch and to encounter with advantage the counter
batteries which could be erected against them.
The following constructions both for the enceinte and
ELXlCEirrS OF PBRMAKBKT FOBTIFIGATION. 47
OTitworkB are taken from the best French authoriticiB as
adopted by him for polygons higher than the pentagon.
68. In the plan of trace (Fig. 2, PI. 10), the magistral is
taken as the directing line ; the exterior side is 360 yards ;
on the perpendicular of the front a distance of ^ the exterior
side is set off; lines drawn through this point and the ex-
tremities of the exterior side, determine the directions of
the faces, and the lines of defence ; from the salients a dis-
tance equal to f of the exterior side is set off, which gives
the lengths of the faces and the positions of the shoulder
angles ; the flank is drawn by taking the opposite shoulder
angle as a centre, and with a radius equal to the distance
between the shoulder angles describing an arc to inter-
isect the line of defence ; the chord of this arc is the flank ;
the curtain is drawn by joining the extremities of the flanks.
By this construction the flanks will be about 54 yards ; the
•curtain, 146 ; and the lines of defence, 267 ; the length of
these being determined so that the salients of the bastions
<5an be defended with the ra/mma/rt gun^ or waU-piece.
69. Tenaille. In many of the places constructed before
Yauban's time there was a fausseiraie, enveloping the
enceinte and connected with it. This work was suppressed
by Vauban, who was the first to use the tenaille in its place.
The tenaille is separated from the curtain by a ditch 10
jards wide, and from the flanks by ditches of 6 yards.
The form of the tenaille as used by Vauban was variable.
In some cases he made it with a curtain and two small
:flanks parallel to those of the enceinte ; in others it con-
sisted simply of two wings placed on the prolongations of
the faces ; and flnally, he gave it the form in Fig. 2, with a
rsmall curtain and two wings, which is the one at present
most generally adopted. The relief of the tenaille is so
arranged as not to mask the fire of the flanks on the ditch
of the enceinte along the faces ; for this purpose Vauban
places its interior crest on a level with the site, or a little
below it.
The tenaille has many valuable properties; it covers the
postern under the curtain ; masks the masonry of the cur-
tain and flanks, so that a breach cannot be made in them,
and in this way prevents retrenchments, resting against
those parts^ from being turned ; ^ place-of-arms is formed
between it and the curtain^ where troops can be assembled
for sorties in the ditches ; finally, its fire sweeps the ditch
and counterscarp, and helps to cover the retreat of troops
from the other outworks.
48 ELEMENTS OF PERMAN^INT FORTIFICATION.
70. Main Ditch. Yauban followed no invariable rule
in regulating the dimensions of the enceinte ditch ; its most
usual width at the salients of the bastions, where the coun-
terscarp is an arc of a circle, is about 36 yards ; the rest of
the counterscarp is tangent to this arc, and directed upon
the opposite shoulder angles.
71. Demi-lnne and Reduit. Yauban increased the
dimensions of the demi-lune, which had been used previous
to his time.
The object of this work is to secure the gates of the place
from a surprise ; to mask from the enemy's batteries the
flanks and curtain of the enceinte ; to give cross-fires on the
salients of the bastions, and to favor sorties.
The plan and dimensions of the demi-lune vary also in
Yauban^s works. Its magistral is generally laid out by
taking a point on the bastion face at 10 yards from the
shoulder angle, and drawing a line from this point to the
perpendicular of the front, so as to make the face of the
demi-lune equal to f of the exterior side. The parapet of
the demi-lune is the same as that of the enceinte ; its com-
mand is 3 feet less than that of the enceinte.
All the outworks in this system are commanded by the
enceinte ; the outworks most advanced being ako com-
manded by those in rear.
The ditch of the demi-lune is generally about 24 yards,
wide and of the same depth as that of the enceinte ; its
counterscarp and that of the enceinte forming a continuous
wall.
72. To strengthen the demi-lune, and secure for the
troops entrusted with its defence a safe retreat when it is
carried, Yauban placed in it a small redoubt. This work, in
some instances, was only a simple loop-holed wall with a
ditch in front ; sometimes it was made of earth, and after
the commencement of the siege.
73. Covered-way. The covered-way envelopes the en-
tire counterscarp. The general width of the covered-waj
is 12 yards.
To set out the reentering place-of-arms, two points are
taken, at 20 yards from the reentering angle, made by the
interior crests of the covered-ways of the demi-lune and
bastion, and upon these crests, and from these points as-
centres, with radii of 24 yards, arcs are described ; the point
of their intersection being joined with the centres gives the
crests of the reentering place-of-arms.
The parapet of the covered-way is terminated in a glacis,.
ELEMENTS OF PERMANENT FORTIFICATION. 49
the foot of which is from 40 to 50 yards from the interior
crests.
74. Traverses. To close the places-of-arms, and enable
the troops to defend the covered-way foot by foot, traverses
of earth formed into parapets are placed at the places-of-
arms. Defiles or passages of 4 feet are left between the
traverses and the crest of the covered-way, for the circula-
tion of the troops. The covered-way is palisaded to prevent
surprise.
V auban placed a high value on this work, which, to use
his own words, " costs less to the defence and more to the
assault than any other work." The covered-way prevents
all access to the ditch, by a strong fire of musketry, which
sweeps all the exterior ground ; it is a secure position where
troops can be assembled in safety for sorties; it covers the
retreat of troops from the exterior into the other works.
76. Communications. In Yauban^s front, ramps are
made to ascend from the plane of site to the terre-plein.
A postern is made under the curtain to communicate from
the interior with the ditch ; another postern is made under
the tenaille to lead to the demi-lune. A double caponniere^
which is a passage covered on each side by a parapet termi-
nated in a glacis towards the ditch, covers the communica-
tion through the ditch to the gorge of the demi-lune.
Single caponnieres are placed in the ditch of the demi-lune,
and cover the troops from the enemy's fire through its
ditch.
Stairs are placed at the gorges of the tenaille and demi.
lune, and along the counterscarp at the places-of-arms, to
ascend from the ditch to the terre-pleins of those works.
To communicate with the exterior, narrow openings are
made in the faces of the reentering place-of-arms, to lead
from the terre-plein to the glacis ; they are termed sortie-
passages or sally-ports ; and are closed by barriers.
76. Analysis. In the trace adopted by Yauban for the
enceinte, it may be observed that the length and positions
of the lines of the front, resulting from it, are in good de-
fensive relations both for the cannon and small-arms of its
day.
1. The foot of the scarp, throughout the length of the
curtain and the bastions, is thoroughly swept by me fire of
the flanks.
2. The length of the flank is suflScient to contain as
many cannon at least as the assailant can place to counter-
batter the flank from the glacis crest opposite the flank ; and
66- BLEMElsfTS OF PERMANENT PORtlFt'C AllOiT^
the flank can also bring an efficient fire of small-arms to
bear on this battery of the assailant.
3. The bastions are capacious, and would admit of effi-
cient interior retrenchments being thrown up in them^
although Vauban does not indicate this auxiliary in his first
method.
4. The tenaille was devised mainly to mask the scarp wall
of the curtain and flanks, whilst its relief was so regulated
as not to intercept the fire of the fianks on the enceinte
ditch before the bastioned faces.
The plan of the earlier tenailles consisted of two flanks
connected by a curtain, which were parallel to the same lines
of the enceinte. This form was subsequently abandoned,
as the flanks were found to be exposed to both an enfllading
and reverse fire, from the assailant's positions in front oi
the enceinte ; and the one now in most general use, consist-
ing of either two wings simply, or of two wings connected
by a short curtain, adopted in its place.
The tenaille, however, only partially subserves its object,
BS it does not cover the entire height of the scarp of the en^
ceinte curtain and flanks ; and, what is a more serious de-
fect, it leaves the entire height of scarp of that portion of
the curtain, opposite to the ditch between the tenaille and
the bastion flanJk, entirely exposed, from the same position,
and liable to be breached.
5. From the small size of the demi-lune, it gives but
little cover to any portion of the enceinte scarp except the
curtain. It is not sufficiently thrown to the front to give a
food volume of cross-flre on the glacis in advance of the
astion salients ; and the reentering formed at this point, by
the two adjacent demi-lunes, is, from the same cause,
shallow and of but little strength. Owing to this last de-
fect the assailant can easily breach and storm the enceinte
at the same time as the demi-lune.
Besides these defects the demi-lune is not provided with
a permanent r6duit, a work necessary to enaole the demi-
lune to make a vigorous defence, by the support it affords
the assailed.
6. From the width given to the demi-lune ditch, the
covered- ways are exposed to a slant reveree fire, from which
they are but badly screened by the traverses. Their com-
mand over the site is rather too little. Their main defect,
however, is the small size given to the reentering place-of-
arms, and the failure to secure this important position for
assembling troops for sorties by a permanent r^duit, bv
which any open attack of the covered-way could be checkedL
ELBBCEBfTS OF PERMANENT FORTIFICATION, 61
7. The dimensions given both to the enceinte and demi-
lune ditches present a formidable obstacle to an open as-
fiault, and render the assailant's passage of the ditch by the
sap also more difficult. The demi-lune ditch, however, oflEers
a wide opening through which the scarp of the bastiot-face
can be seen down to its foot from the assailant's batteries
on the glacis crest in the prolongation of the demi-lune ditch.
8. The communications within the enceinte, and from it
to the main ditch, are sufficient and convenient for the char-
acter of the defence designed. Those of the outworks are
for the most part narrow, inconvenient, and but badly
4Bcreened from the assailant's fire, and therefore do not furnish
a good provision for an active defence beyond the enceinte.
9. The great command over the site, and the high relief
fiven to the enceinte, are very much in favor of the defence
oth as to the eflEect of the fire on the assailant's approaches
and for security against an escalade. But in attaining these
objects Yauban has left exposed to the assailant's distant
fire a considerable portion of the scarp wall, which, being
destroyed, would lay the enceinte open to a surprise.
in.
cobmontaigne's method.
77- Cormontaigne, bom 1696, died 1752, the immediate
successor of Vauban, holds a place only second to this mas-
ter of the art in the estimation of tne engineers of the
French school. Cormontaigne, who, to superior abilities^
united a wide range of experience both in the construction
and in the attack of permanent works, studied with great
care the results of Yauban's immense labors. In planning
the front which has received his name, Cormontaigne seems
to have applied himself rather to remedy the defects notice-
able in the methods of Yauban, than to produce any radical
change in the combinations which had thus far received the
sanction of engineers generally. He was thus led to reject
the 2d and 3d methods of Vauban, and to take the first
method as the basis of his own changes.
78. 'Cormontaigne was the first to develop clearly the
influence of large demi-lunes on the progress of the attack,
by their forming deep reenterings between them in front of
the bastion salients ; and also the increased strength gained
by fortifying on a right line, or on polygons with a great
number of sides, as in both of these cases the fronts assailed
52 ELEMEN^TS OF PERMANENT FOETIFICATION.
cannot be enveloped by the assailant's works, and the denai-
lunes from their salient position intercept the prolongations
of the bastion-faces, and thus mask them from the positions
from which alone an enfilading fire could be brought upon
them.
79. He likewise lays down as a principle that no masonry
should he exposed to the distant batteries of the assailant^
and to obtain this point he has so arranged the height of his
principal scarps, and the command given to the glacis crest
in front of them, that the top of the scarp shall not lie above
the level of the crest, thus masking from view the entire
scarp, by the earth forming the glacis, from all positions in
advance of the fflacis crest.
His modifications of the plan and profile of Yauban's 1st
method chiefly result from the above as a basis.
80. Enceinte, The modifications of Yauban's trac6
(Fig. 4, PI. 10) are different in the various works of Cormon-
taigne; but the following he indicates in his memoirs as
the one preferred by him.
The exterior side is 360 yards ; the perpendicular \ ; the
faces of the bastions J of the exterior side ; the flanks are 40
yards, and are so placed that the curtain shall be 120 yards.
This combination makes the lines of defence somewhat less,,
and the bastions larger than in Yauban's method.
The dimensions of the enceinte ditch are so regulated by
Oormontaigne as to furnish earth sufficient for the embank
ments. It is 28 yards wide at the salient and from 2 to 4
yards wider opposite the tenaille ; this admits the entire fire
of the flanks to sweep the ditch.
81. Tenaille. The tenaille is made with a curtain and
wings ; a ditch 10 yards wide being left between it, the cur-
tain, and the flanks.
82. Denii-lune. Oormontaigne placed little value on
small demi-lunes, as they form but slight and therefore weak
reenteritigs before the bastions, and consequently retard but
little the enemy's attack upon them ; besides this, a small
demilune covers but very imperfectly the shoulder angles
of the bastions.
To remedy these defects, his demi-lune is so laid out that
the prolongations of the magistrals of its faces will intersect
the bastion-faces at 30 yards from the shoulder angles; the
lengths of its faces being 120 yards.
The ditch of the demilune is 20 yards wide; its depth is
the same as that of the enceinte. By thus enlarging the
demilune, sufficient space is gained to place a strong reduit
ELEMENTS OF PERMANENT FORTIFICATION. 53
in its interior. The defence of the demi-lune may be made
"with more obstinacy from the support it receives from the
rednit ; and the enemy will be obliged to carry it before he
can assault the breach he may have made in the bastion
face, as this breach is seen in reverse by the fire of the flanks
of this work.
83. Demi-lune Reduit. To circumscribe as much as
practicable the space in the demi-lune which the enemy,
after he gains it, requires for his works, the extremity of
the demi-mne terre-plein, which is also the top of the counter-
scarp of the reduit, is drawn at 20 yards from the magistral
of the face ; the ditch of the reduit is 10 yards wide, and
the magistral of its face is parallel with the counterscarp.
Bv this arrangement the ditch is well flanked by the face
01 the bastion near the shoulder angle.
To lay out its flanks, the counterscarps of the enceinte are
prolonged to intersect the perpendicular of the front ; from
this point of intersection a distance of 20 yards is set oflE
-along each counterscarp ; the two points thus obtained are
joined by a right line, which is the gorge of the work:
from the extremities of the gorge two lines are drawn paral-
lel to the capital of the demi-lune, these lines limit the terre-
plein of the flanks ; the magistrals of the flanks are drawn
parallel to and at 16 yards from the last lines.
84. Covered-way. etc. The general width of the
covered- way is 10 yaros. Oormontaigne enlarged consider-
ably the reentering place-of-arms, to which he added a
reduit with a revetted scarp and counterscarp. The addi-
tion of this work is a great improvement upon the covered-
way of Vauban, who indicates in his works small reduits of
-earth, or tambours of wood, for the same purpose.
Cormontaigne's reduit increases the strength of the
<30vered way ; the troops assembled in the covered-way for
forties are secure under its fire ; it sees in reverse, and pro-
tects any breach made in the face of the demi-lune ; finally,
it serves, in connection with the extremity of the demilune,
to cover the opening left between the flanks of the bastion
and the wings of the tenaille, through which, if a breach
was made in the curtain, the interior retrenchments, resting
upon either the flank, or faces of the bastion, could be
turned.
To lay out the interior crests of the reentering place-of-
^rms, two points are taken on the counterscarps of the bas-
tion and demi-lune at 54 yards from their point of intersec-
iion ; from these points as centres, with radii of 60 yards,
64 ELEMENTS OP PERMANBN^T FORTIFICATION.
arcs are described, whose intersection joined with the cen«
tres gives the direction of the faces.
The magistral of its r^duit is found bv a similar construc-
tion ; distances of 40 yards being set oft along the counter-
scarps, and the faces being drawn from these points so as
to be 36 yards long. The ditch of the r^duit is 5 yards^
wide and 2^ yards deep.
Traverses are placed along the covered- way, to close the^
places-of-arms, defend the covered-way, and intercept pro-
jectiles tired in ricochet.
The crest of the glacis is broken into acremaillSre line ta
allow room for the defiles of the traverses. The short
branches of the cremaillere throw a fire on the salients of
the covered-way ; the positions of the long branches are so
taken that the defiles may be seen and swept by the fire of
the works in their rear.
86. Profiles. Cormontaigne, after a series of trials,
whose object was to give the ditches such dimensions that
they should furnish the earth required for the embank-
ments, regulated the command of the diflEerent works as-
follows :
The lowest work, which is the demi-lune covered-way, ha
lays down as a rule, shall command the exterior ground by
not less than 7i feet ; and the works most advanced shall
be commanded by those in the rear.
It was found that, for the purpose of equalizing the ex«
cavations and embankments of the front, the crest of the^^
demi-lune covered- way should have a command of lOJ feet
above the natural ground.
The crest of the bastion covered-way and of the reenter-
ing place-of-arms commands the crest of the demi-lune
covered-way by 2 feet.
The magistral of the enceinte is horizontal, its elevation
being the same as the mean elevation of the crest of the
bastion covered- way.
The scarp wall is 30 feet high. This dimension has until
recently been generally adopted by engineers, a wall of this
height opposing a sufficient obstacle to an attempt at esca-
lade.
The salient of the bastion commands its covered-way
by 8 feet. The absolute relief of the fianks is 384 fe©*-
With this relief a piece, firinjg under a depression of 4
through an embrasure in the flank, and in the direction of
the curtain, will strike the bottom of the ditch at the
ELEMENTS OF PERMANENT FOBTIFICAXIOK. 65
middle point of the curtain; so that were the relief inp
creased, the length of curtain remaining the same, the ditch
would no longer be thoroughly flanked.
The relief of the tenaille is determined as in Vauban's
method, so as not to mask the fire of the flanks upon the
ditch opposite the extremity of the demi-lune ; as it is here
that a breach may be made in the bastion face, through the
ditch of the demi-lune.
The demi-lune is commanded by the enceinte 3 feet, and
by its own reduit 1^ feet. The demilune, therefore, com-
mands its covered-way 7 feet, which is more than is indis-
pensably requisite ; for an enemy standing on the crest of
the covered-way cannot have a plunging fire into a work
in the rear of it, if the latter commands its crest by 5
feet.
The reduit of the reentering place-of-arms commands the
crest of the glacis only 4^ feet ; its interior crest is so placed
as not to mask the fire of the bastion faces on the glacis in
advance of it.
The interior crests of all the works are Yj feet above their
terre-pleins, except that of the tenaille, which is 6J feet ;
and of the reduit of the reentering-place-of-arms, which is 9
feet.
The interior crests of the faces of all the works exposed
to enfilading fires are one foot higher at the salients than at
the extremities.
The profile of the parapet of the principal outworks is the
same as that of the enceinte.
86. C o m m unications, The communications are gen-
erally of the same nature, and placed about in the same posi-
tions as in Yauban's method.
87. Glacis. The planes of the glacis are so determined
that they may be swept by the fire of the works in the rear ;
their inclination is usually about twenty-four base to one
altitude.
Interior Retrenchments. Cormontaigne indicates the
gorge and shoulders of the bastion as the position for an in-
terior retrenchment, when this addition to the front is made
solely with a view of disputing the breach in the bastion
and its interior with the assailant. In this case he gives the
retrenchment the form of a tenaille, or a bastioned front,
resting it either upon the shoulder angles of the bastion, or
upon the two adjacent curtains on the points beyond the
prolongation of the ditch between the tenailles and the
56 ELEMENTS OF PERMANENT FORTIFICATION.
flanks, and in this position he gives it the form of a has-
tioned front.
In the former case, the portion of the interior of the bas-
tions between the flanks is preserved for the defence, but
the retrenchment is liable to be turned, by a breach made
in the flank, or in the portion of the curtain where it ioins
the flank: In the latter case a breach in the bastioji places
the whole of the interior within view of the assailant, but
the retrenchment itself is secure, from its position, from
being turned, as a breach in the curtain cannot be made in
rear of it.
88. Cavalier, When a greater command of the site
than that S-fforded by the enceinte is requisite on any front,
Cormontaigne places a cavalier within the bastion. To this
work he gives the same form as that of the bastion ; placing
the faces and flanks of the two parallel to each other. The
faces of the cavalier are alone revetted, as well as the counter-
scarp of their ditch, which is cut within the bastion. This
ditch is broken off at the shoulder angles of the cavalier, and
directed upon the faces ; these portions also having a revetted
scarp and counterscarp. A parapet is thrown up behind
the scarp and between the nank of the cavalier and the
bastion faces ; thus isolating the anterior portion of the bas-
tion, and furnishing an interior retrenchment which, when
the shoulders and flanks of the bastions are masked from the
assailant's view, can only be carried by a breach made either
in the cavalier face, or in the portions resting on the cavalier
and bastion faces.
89. Analysis. From the preceding description, it ap-
pears that the most important modifications made by Cor-
montaigne in Yauban's first method, consist :
1. In the means taken to cover the masonry from distant
batteries.
2. In more capacious bastions susceptible of receiving
eflicient permanent interior retrenchments.
3. In an enlarged demi-lune, which places the bastions in
strong reenterings, covers the shoulder angles, and admits
of a reduit in its interior, which work strengthens the demi-
lune, and sees in reverse the breach made in the bastion
face.
4. In an enlarged reentering place-of-arms, containing a
r6duit which strengthens the entire covered- way, and covers
the movement of the troops in sorties.
These modifications, although of great value, and con-
ptituting an important step in the art, still leave much to be
ELEMBKTS OP PERMANENT FORTIFICATION. 57
-desired ; and eBgiueers since Cormontaigne's time have
sought to remedy the defects of his method, of which the
following are the principal :
1. The enceinte has rather too slight a command, and is
withont any bomb-proof shelters.
2. The inclination of the superior slope of its parapet^
which is ^, is too small to have the ditches well flanJked.
3. A breach can be made in the bastion face through the
ditch of the demi-lune.
4. There are dead spaces in the ditch of the demi-lune,
near the extremities of its faces.
5. The reduit of the reentering place-of-arms is not tena-
Ue after the demilune is taken.
6. The traverses of the covered-way do not afford the re-
quisite protection to that work.
7. Finallv, the communications are mostly inconvenient,
iind not well covered from the assailant's fires.
90. Counterguaxd. Vauban, in his third method,form8
his enceinte with a high scarp wall, of the same dimensions
And form as in his first method ; and he procures his flank-
ing arrangements for the enceinte bv small bastioned towers
of masonry, which are casemated in the lower story, and
have an open battery in the upper, covered by a masonry
parapet.
This enceinte he covers with spacious counterguards of
^e form of lunettes ; the faces, flanks, and gorges of which
Are revetted, and which cover the bastioned towers of the en-
ceinte ; and between the flanks of these counterguards, and
•covering the curtain of the enceinte between the bastioned
towers, he places a tenaille.
A demi-lune, in the form of a lunette, is placed in front
of the counterguards and tenaille; within which he has
placed a reduit with a revetted scarp and counterscarp. The
whole of this combination of outworks he incloses with a
oovered-way arranged in the usual manner.
91. Oormontaigne uses the counterguard only as an ex-
<5eptional outwork ; and has applied it, m some of the works
constructed by him, to strengthen a point that would other-
wise have been too weak; but not like Yauban, as a con-
stituent part of his method.
92. Two of the most eminent modern engineers, Coe-
hoorn, bom 1641, died 1704, and Carnot, born 1753, died
1823, in their methods, use earthen counterguards to cover
their enceintes, giving them only suflScient thickness at the
top for a parapet and a banquette for infantry ; so that, be-
58 ELEMENTS OP PERMANElffT FORTIFICATION.
ing taken by the assailant, he will not find sufficient room
to place a breaching battery npon their terre pleins against
the enceinte. In this way they serve chiefly as masks or
face covers to the enceinte faces.
93. Haxo, born 1774, died 1838, forms of the counter-
gaard a constituent element of his method, giving it, like
Vauban, the form of a lunette.
94. Noizet, born 1792, died 1885, although adopting the
features of Cormontaigne's method as the basis of his, speaka
of the counterguard as a valuable, and sometimes a neces-
sary, element of a front ; preferring it in some cases to the
demi-lune.
Like all other outworks, when used, it should be flanked
by the enceinte flanks ; be swept on the interior by the fire
of its faces; and not intercept their fire on the ground
in advance of it.
IV.
METHODS OF THE SCHOOLS OF MEZIEBE8 AND METZ.
95. The schools of application for engineer and artillery
officers, first established at Mezieres and subsequently at
Metz,now at Fontainebleau, has given to France, from about
the period of the French Kevolution down to the present
day, the far greater portion of the many able officers who-
have gained such universal and deserved celebrity for these
two corps.
In these schools the precepts of Vauban and Cormon-
taigne have been jealously regarded as the highest authority^
and their manuscripts and published works have formed the
basis of the instruction given in them.
96. Some slight modifications were proposed in the front
of Cormontaigne by two engineers, vhatiUon and Dvm-
gneau^ and taught by them in the course of permanent for-
tification given in the school. These changes chiefiy con-
sisted in enlarging the demi-lune and making it more
salient; and in placing in the fianks of its r^duit casemates
for cannon with reverse views on the breaches that might
be made in the bastion faces.
97. The teaching of the school of Metz received its prin*
cipal impress from General Noizet, himself a pupil of Gen-
eral Haxo, regarded as the first among the successors of
Vauban and Cormontaigne, who for several years, while a
ELEMENTS OF PEBMAKBKT FORTIFICATION. 5^
captain of engineers, performed the functions of professor
of fortification, and who subsequently gave to the public
the results of his lectures delivered in the school.
98. The front which, until a few years back, has been
taught in this school, goes by the appellation of Noizets
Method. In it there is no sensible departure from the
views and methods of Yauban and Corinontaigne ; the ob-
ject being to introduce such modifications into the front of
the latter as would remedy some of its acknowledged de-
fects.
In doing this, another object was kept in view which was-
to present, in the combinations of this front, a problem, in
the solution of which the pupil would be called upon to ap-
ply both the elementary principles of fortifications and the
geometrical methods that the engineer has to use as hi&
principal tool in such problems, to a special case, that of a
iront adapted to a horizontal site. It was in this point of
view that the analysis and construction of this front were
for many years adopted as the basis for the elementary in-
struction given in permanent fortification in this Institution^
V.
nomset's method.
99. Oeneral Requirements. Noizet in his front take»
as the basis of the construction of the enceinte the length of
the exterior side, and the command, assuming these within
the limits laid down by Yauban and Cormontaigne, and in
the combinations of outworks with the enceinte, following^
the latter engineer ; introducing only such modifications as.
seem to best fulfil the general conditions of the problem.
100. General data of the Enceinte. In the follow-
ing description of the front of Noizet, (Plate 11a, Fig. 1,)
the plane of comparison is assumed at 60 feet below the
horizontal plane of site, the reference of which will be, there-
fore, (60.0). The yard is taken as the unit for the horizon-
tal dimensions of the plan ; and the foot as the unit for the
references and vertical dimensions.
Converting the French measures into their equivalent
English units, the exterior side of the front is 380 yards ;
the height of the scarp wall 33 feet ; the command of the
interior crest of the curtain over the plane of site 21 feet j
and its height above the magistral 13 feet.
60 ELEMENTS OF PERMANENT FOBTIFICATION.
The dimeDsions of the exterior side and of the relief , as
here given, are so taken as to secure an efficient flanking
arrangement of the cnrtain ; and of the outworks by the
bastion faces.
101. Profile of Enceinte. The profile of the en-
<5einte here given is similar to that of Cormontaigne, and
was adopted by subsequent engineers until the more re-
-cently modified one already described.
Its slopes and dimensions are as follows : — The scarp and
<50unter8carp slopes VjOr one base to twenty altitude. Ex-
terior slopes ^, or 45 . Superior slope ^. Interior slope f .
Banquette slope J. Rampart slope f . Terre-pleins 8 feet
below the interior crests. Berm 2 feet. Distance between
the magistral and foot of the exterior slope 1.5 feet. Thick-
ness of parapet 20 feet. Height of interior crest above the
banquette tread 4.5 feet. Greneral width of terre-plein esti-
mated from the vertical through the interior crest 48 feet.
102. Magistral of the Curtain. The length of this
is a minimum consistent vdth the artillery fire of the flanks
passing IJ feet above the bottom of the ditch at the centre;
this fixes it between 139 and 140 yards.
103. Magistral of the Enceinte. The perpendicular
to the front is ^ the exterior side, the lines of defence are
drawn as usual, the flanks make an angle of ^ with the per-
pendicular to the front; the faces are determined by the
curtain and flanks.
A limited amount of protection from enfilade is given to
the long lines by giving greater command to the bastion
and demilune salients, but the scarp walls are not corre-
spondingly raised.
104. The Outworks. These satisfy the general con-
ditions of defence, and are carefully designed to fulfil the
requirements of a problem in fortification-drawing, in which
the details are thoroughly worked out, and the determina-
tion of whose relations involve most of the geometrical
problems met with in such work.
105. Remarks. The principal points of difference
from Cormontaigue's method consist in a change in the
directions and lengths of the faces of the redoubt of the
reentering place-or-arms, without, however, destroving its
usefulness in connection with the ravelin as a mask to the
curtain ; in making a cut or coupure in the ravelin face in
front of the redoubt of the reentering place of -arms, to pre-
vent the redoubt being turned when the besiegers get pos-
session of the ravelin ; in prolonging the bastion counter-
ELEMENTS OF PERMANENT FORTIFICATION. 61
scarp across the ditch of the demi-lune and its redoubt, and
constructing in the first a face-cover for the bastion, and a
covered communication and single caponier for sweeping
the ditch ; and in the second, a mask to cover the shoulder
angle from fire coming through the redoubt ditch; and in
placing four traverses in the demilune covered-way, which
is made wider toward the reentering place-of-arms to give
better cover to the defiles of the traverses.
A complicated system of glacis planes was designed, add-
ing to the value oi the front as a problem in construction.
106. General Remarks. In the combination and ar-
rangement of the outworks, Noizet has followed closely the
metnods of Cormontaigne, and of the school of Mezieres.
The principal objections to these combinations are :
1. That from the command given to these works, a con-
siderable portion of the fire of the enceinte, on the site ex-
terior to these works, is obstructed by them. And that
some of these works, like the reduit of the demi-lune, and
the parapet behind the cut in the demi-lune face, mask the
interior of the demi-lune from a portion of this fire.
2. That from the revetted gorges of these works, and the
kind of communication between them and the enceinte
ditch, sorties on the assailants' works in them, can only be
made in small and feeble parties.
3. That the traverses of the covered-ways obstruct the
free movement of troops along them, and also obstruct the
fire of the enceinte on their terre-pleins.
4. The plunging fire of modern artillery searches out the
masonry scarps over the glacis and through the ditches of
the outworks, making it practicable to breach the enceinte
by the distant fire.
107. For these defects various changes have been sug-
gested, and some of them have been adopted in some of the
more recent European fortifications.
These consist —
1. In giving a greater command to the enceinte than that
usually found in the methods described.
2. In suppressing the reduit of the demi-lune, as usually
constructed, in decreasing its command, and replacing it by
a casemated reduit placed at the gorge of the demi-lune.
3. In suppressing the traverses of the covered-ways ex-
cept those enclosing the reentering place-of-arms ; depend-
ing on the short branches of the cremailleres into which the
interior crest of the covered-way is broken to limit the
effects of enfilade fire, and in reducing its width, to bring it&
62 ELEMENTS OF PERMANENT FOBTIFICATION.
crest nearer the scarp wall ; nsiDg it as a chemm de ronde
only.
4. To replace the narrow stairs nsed by Vauban for com-
municating with the terre-pleins of the outworks, by wide
ramps to fticilitate sorties in large bodies.
5. To flank both the covered-way and the demi-lune
ditch by a casemated r6duit placed within the reentering
place-oi-arms.
6. To make the communications more ample and direct.
7. To simplify the outworks, suppressing some, and mak-
ing the others more subservient to the artillery fire of the
enceinte.
Most of these modifications have been introduced into the
front now taught at the school of Fontainebleau.
Plate 1, Figs. 4 and 6, show the latest and simplest form
of the bastioned system without outworks.
108. In every combination the engineer must be guided
by the exigencies of the sites that he is called upon to for-
tify, the character of the defence that it is proposed that the
work shall make, and the relative pecuniary cost of differ-
ent combinations. In taking this last consideration, how-
ever, into account, he should not forget that the pecuniary
outlay for a work that will protract tne defence only a few
days longer may often bear no comparison to the benefits
arising from it.
NoTB. — A full description of Noizet's method, with the analysis of
the different parts, will be found in the unrevised edition of this work.
VI.
ohoumaba's method.
109. Ohoumara, born 1787, died 1870, a French officer of
engineers, of distinguished abilities, is the author of several
remarkable memoirs on the defects of the bastioned system,
and the means by which they may be removed and much ad-
ditional strength be thereby given to the defences. His
I)ropositions for this purpose may be briefly stated as fol-
ows:
1. That part of a permanent work which can undergo no
modification during the progress of a siege is the masonry,
and it may therefore be regarded as the really permanent
feature ; all the parts of earth, as the parapets, etc., being
susceptible of such modifications as circumstances may de-
mand.
ELEMEirrS OF PERMANENT FORTIFICATION. 63
This Choumara terms the independence of the jxtrapets
418 respects the scayps.
The latter, upon which the security of the work against
^n open assault or a surprise depends, must necessarily re-
<5eive a direction, such that it can be swept by the flanfcing
arrangements, a necessity that does not exist for the para-
pets, which may receive any direction compatible with the
interior space.
The parapets may therefore be thrown back from the
salients, as in the bastion, (PI. 12, Fig. 1,) and receive a
<}urvilinear form to throw a greater volume of fire in the
direction of the capital.
Or they can be retired from the faces, as in the bastion
(Fig. a), ior the purpose of giving them such directions
that their prolongations shall cut the adjacent demi-lunes,
and thus be masked from enfilading views.
Or they may be prolonged so as to afiFord a greater col-
umn of flank fire, as in the flanks 1, (Fig. 1,) or they may
be broken into any direction for the same purpose, or to
give a more effective direction to their fire.
Or, finally, they may be thrown back from the scarp
walls instead of resting immediately upon them, and thus
render a breach less practicable, since the whole, or a por-
tion, of the parapet will still retain its place after the breach
has been made in the scarp, depending on the distance at
which the parapet has been moved back.
In all of these cases of the application of the independ-
ence of the parapets, Choumara proposes to convert the
space left between the foot of the parapet and the scarp
wall into a chemin de ronde^ or corridor, which is covered
in front by a slight parapet, and from enfilading fire by
giving an increased height to the portion of the parapet
adjacent to the salients, forming a bonnet^ as in Figs. 1, a,
R, etc. This corridor is occupied by sharpshooters to annoy
the besieger's trenches. Furthermore, Choumara regards
the corrioor as an additional security against surprise and
escalade.
2. Choumara proposes to place high traverses in the bas-
tion salients, to cover the faces from enfilade and the flanks
from reverse views, and similar traverses at the shoulder
angles with the same object. These he also proposes to
<5asemate, or else construct with blindages for artillery to
obtain a fire in the directions of the capitals, and reverse
views on the demi-lune glacis and the breach in the bastion
face. As these traverses, from their height, might give the
4)esieger8 in possession of them a plunging fire on the bastion
64 ELEMENTS OF PERMANENT FORTIFICATION.
retrenchments, he proposes so to arrange them that thev can
be readily destroyed at any moment by mines, or, if oi tim-
ber, be burned.
3. To mask the masonry of the enceinte and demi-lune
from breaching batteries, erected in their usual positions
along the crests of the glacis, Choumara proposes to form
what he terms an interior glacis^ or covering mass of earth,
in the ditches, the crests of which shall mask the masonry
of the scarps from the positions in question ; and the upper
surface of which, forming a glacis, shall be swept by the
fire of the works in its rear. In this manner he expects to
force the besiegers to the diflBcult operation of making
lodgments in this glacis to obtain suitable positions for their
breaching batteries.
4. By selecting for some of his outworks those points on
the exterior which are most favorable to the action of the
assailant's sharpshooters, he proposes in this way to cripple
this important means of attack.
5. By giving greater extent to the exterior side, and a
more retired position to tlie curtain, which is also to be
made as short as possible, Choumara obtains bastions of
ample size, not only to admit of the modifications he pro-
poses for the parapets, traverses, and chemins de ronde^ but
lor strong interior retrenchments, so organized with bomb-
proof shelters, and arranged defensivdy towards the in-
terior, that each bastion will admit of a aefence to the rear
at its gorge, after the besiegers may have effected a breach
at other points and penetrated within the enceinte.
110. Flan. In adapting these propositions for a bas-
tioned front, Choumara proposes, in order to obtain the re-
quisite room in the interior of the bastions and a large in-
crease of flank fire, to take the exterior side from 400 to 600
metres, French. In the front (Fig. 1, PI. 12), for example,
the exterior side is 440 metres; the lines of defence are
drawn through a point on the perpendicular of the front at
Y4 metres, or one-sixth of 440 metres within the exterior
side ; the faces are 150 metres, and the flanks, drawn per-
pendicular to the lines of defence, are 85 metres, a length
which prolongs them 35 metres within their intersections
with the lines of defence.
By this construction th^ curtain, which will be 115 metres
long, will be well swept, and the gun at the curtain angle
can be brought to bear on the one of the besieger's counter-,
battery against the flanks which is furthest out, thus giving
a very great preponderance in tire to the flank over the
counter-battery.
ELBMENTS OF PERMANENT FORTIFICATION. 65
' The deep reentering thus formed between the flanks and
curtains gives ample room for a tenaille with flanks for fonr
guns ; these guns are covered in flank by a traverse. The
tenaille is not revetted in front of its curtain and flanks, or
at its gorge. It masks sufficiently the scarp of the flanks,
and curtain of the enceinte, to prevent any danger to the
latter from the destruction of the portion of the scarp wall
that can be seen over the tenaille.
111. The salient of the demi-lune is the vertex of an
equilateral triangle, the base of which is drawn between
two points on the bastion faces, at 18 metres from the
shoulder angles. The faces of the demi-lune, d, are 144
metres, and revetted. The parapet of the demi-lune is
thrown back from the revetment, leaving a corridor cov-
ered by a parapet at the foot of its exterior slope. The
parapet is broken near the gorge, so as to give two short
flanks of 13 metres perpendicular to the exterior side. The
salient is occupied by a casemated traverse with flanks for
three guns. This traverse masks the interior of the demi-
lune and the corridor from enfllading views. A disposition
is shown for cuts across the demilune faces, the parapets of
which are to be thrown up after the siege commences. The
demilune ditch is 17 metres wide. The portion of this
ditch towards the gorge slopes upward as a glacis, and is
swept by the fire of the enceinte.
1 12. The interior glacis of the demi-lune commences at the
counterscarp of this work and haa a glacis slope outwards,
its width being 45 metres. Here commences the revetted
forge of the covered-way. The width of the covered-way is
metres. Its interior crest is an indented Une. There are
no traverses in this work unless required for its defilement.
113. A spacious and strong reduit is placed in the demi-*
lane salient place-of-arms. Its faces are 132 metres long,
and revetted. Its parapet is thrown backi leaving a corridor
in front of it, and is curved at the salient for five guns,
sweeping along the capital. A bonnet is placed in its salient
to cover the corridor from enfilade, and two traverses for the
same object on its terre-plein. This reduit forms a mask
for the portion of the demilune occupied by the traverse.
114. Choumara places strong reduits, m, with revetted
scarps and gorges in the reentering place-of-arms. The parar-
pets of these works are curved at the salients for batteries to
sweep the approaches on the bastion capitals and the demi-
lune glacis, and they are thrown back from the scarp walls
to give a corridor for sharpshooters. As these r^uits are
66 ELEMEKTS OF PERMANENT FOBTIFIGATIOK.
necessarily contracted, Choumara prefers to them a strong
r^duit of larger dimensions, placed in the bastion salient
place-of-arms and organized like the preceding.
115. One of the most striking features of Chonmara's
modifications is the mode in which he proposes to organize
the large bastions, with defences which shall serve as an in-
terior retrenchment, in case the bastion is one of the points
of attack; or convert the bastion into an isolated fort or
citadel for the garrison, in case the besieger gains possession
of the interior of the enceinte through an assault at some
other point. This he proposes to accomplish by increasing
the lengths of the exterior side, and also of the bastion flanks.
116. With this object Choumara places a row of case-
mates within the bastions, on a line perpendicular to their
capitals. Each casemate is from 60 to 80 feet long, from
12 to 20 feet wide, and 12 feet high. This row of case-
mates serves as a curtain both for the retrenchment of the
bastion and for the defence of the gorge against an interior
$tttack. For the defence of the salient portion of the bas-
tion a cut is made across each face and extended to the
capital. The scarp of this cut is made into the form of a
bastion front with orillons at the shoulder angles ; the case-
mates forming the curtain of this front. The counterscarp
of the cut may be either revetted, or have a simple slope of
earth. In the latter case the bottom of the ditch of the
front at the foot of the scarp wall is at a suitable level to
admit of an eflBicient height of scarp wall to secure it from
escalade. A broad ramp leads from the centre casemate,
along the capital, towards the bastion salient, to the counter-
scarp of the cut, and there branches into two other ramps
leading up to the bastion terre-plein on the right and left.
Until the besiegers are about to breach the bastion- faces
their parapets are left intact ; and the portions of the cut
along which the parapets run are filled up, as in the bastion
on the right, thus leaving a free communication throughout
the interior of the bastion. So soon as it is thought neces-
sary to cut off this communication and to get the retrenched
portion in a state of defence, that part of the parapet across
the cuts is demolished ; the cut excavated and suitably
arranged ; and the parapet of the retrenchment formed in
part of tiie earth arising from these changes. The para-
pet of the front of the retrenchment is thrown back, leaving
a corridor for sharpshooters covered by a slight parapet ;
that portion of this corridor along the retired flauK being
covered by the earthen mask of the orillon. Choumam
ELEMENTS OF PERMANENT FORTIFICATION. • 67
■fnrther proposes, where there is a probability of the scarp
of the oastion-face, which closes the cat on the exterior,
being opened, so that a breach might be made by firing
through it on the flank of the retrenchment, to ran the
«carp wall of the retrenchment at right angles across the
cut, as shown on the right face of the left bastion, and to
arrange the bastionnet, which this modification would give
at the shoulder angle, for sharpshooters.
117- To expose the interior of the retrenchment to the
"fire of the flants of the adjacent bastions, and to the parapet
of a second retired interior retrenchment resting on the two
<;urtains adjacent to the bastion of attack, a portion of the
parapet of the bastion flanks, near the curtain, is demol-
ished, and a slope is given to the portion of the terre-plein
on which it rested. The retired interior retrenchment
Choamara proposes to make of earth in the form of a bas-
tioned front, breaking the faces in the most suitable manner
to sweep the rear of tne retrenchment in its front.
118. The dispositions for converting the bastion into a
<iitadel are similar to the preceding, consisting of a small
front, the faces of which are nearly m the prolongations of
the adjacent curtains, with oriUons to cover the corridor of
the retired flank. This front has a covered- way and glacis
in advance of it, the crest of which masks the scarp.
119. Choumara has made an ample provision for easy
<;ommanications between all points of the enceinte and the
outworks, so placing them as to be well covered from the
besieger's flre and well swept by that of the garrison ; pre-
ierring wide ramps for this purpose. The communication
from tne enceinte with the main ditch is through gateways
in the scarp wall of the curtain, at its extremities. Tne
rampart at these points is removed to the level of the main
ditcn ; the portion of it between them, along the centre of
the curtain, being sustained at the ends by revetment walls
xun back perpendicularly to the scarp wall of the curtain;
Bamps lead from the gorges of the bastions down to these
outlets into the main aitch. From these outlets the com-
munications to the oat works are around the flanks of the
tenaille, and throagh the enceinte ditch, to ramps placed
along the enceinte counterscarp leading into the demi lune,
the demi-lune ditch, the enceinte covered- way, and its re-
doubts in the places-of-arms ; and from the demi lune ditch
to the redoubt of the demi-lune salient place of-arms.
Posterns on* the faces and flanks of the bastions, near the
fihoalder angles, lead to the corridors of the enceinte. Pas-
sages are leit at the ends of the faces of the outworks lead-
68 * ELEMENTS OF PERMANENT FOUTIFICATiOX.
ing from their corridors to the interior of the works. To
keep open the communication between the bastions, a gal-
lery between their gorges is made along the curtain wall.
For the security of the casemates, barricades can be made
in their doors and windows, by means of timber let in
grooves made in the walls ; the space between the exterior
and interior timber facing being nlled with sand-bags.
120. Remarks. The memoirs in which Choumara
brought his propositions before the public naturally attracted
attention, as much, perhaps, from their polemical character
and piquancy of style as their professional interest They
contain but few things the germs of which are not to be^
found in writers who preceded him.
His modifications respecting the parapets, throwing them
back from the scarps and breaking them into directions-
best suited for defence, are to be met with in Chassdoup^a
propositions.
His proposals for lengthening the bastion flanks and
occupying the salient places-of-arms by redoubts with con-
siderable command, are to be found in the method oi dela
CJiiche.
To Yirgm he seems to be indebted for his organization
of interior retrenchments, which are to convert each bastion
into an independent work, equally provided for defence
against approaches both from the interior and exterior of
the encemte.
like disputants, usually, of an ardent temperament, he
over-estimates the value of many of his propositions and
loses si^ht of their counteryailing defects. By laying down
as a principle what may be exceptionally good in practice,,
he has rather weakened his own positions. This is the case^
particularly, with his rule of independence of the parapets-
on the scarps, which, if adopted in all cases, might demand
a greatly increased and hurtful command, and cut up to-
great disadvantage the interior spaces of the bastions.
His introduction of the chemins de ronde on the faces of
the bastion and the demi-lune adds really very little, if at
all, to the exterior defence ; whilst they contract the interior
space of these works, break in upon the unity of the de-
fence, and place the troops in them in a very exposed po^i
tion to the means of annoyance possessed by the besieger.
His expectations with respect to the effect of his lire in
the direction of the capitals, in delaying the besieger^s ap-
proach to the 3d parallel, were hardly warranted by tne
experience gained m artillery and small aruis, even at the
time the last edition of his memoirs appeared. It is hardly
lEIiEJHtKTfi 0» PERMANENT FOftTIFrCATIOK. 69
to be questioned, now that these weapons have been so
greatly improved, both in range and accuracy of fire, that,
Kjonsidering the increased development of the besieger's
parallels, which gives him a choice of positions for his bat-
teries on so extended a line, the concentrated fire he could
bring to bear on the batteries in question would not only
«oon ruin their casemates, but would greatly dama^ the
adjacent faces and also the flanks of the bastions, almough
<30vered from enfilading views, either by the direction of
the parapets^ of the faces, or the high traverses raised with
the same object.
These advantages in the position of the besieger, it is
thought, would prevent any delay in pushing forward his
approaches up to the 3d parallel. After this the approaches
would probably be retarded beyond the usual time in the
attack on Cormontaigne's front, owing chiefly to the reduits
in the bastion and demi lune salient places ot arms, and the
arrangement of the face-cover in the enceinte ditch.
121. Supposing an enceinte organized according to his
method, and containing interior retrenchments to oppose
the besieger's approaches both from without and within the
•enceinte, Choumara estimates at least six separate epochs of
breaching batteries, as follows :
1st, against the r^uit of the demi-lune salient place of-
arms.
2d, against the demi-lune and the reduit of the bastion
«alient places-of-arms.
3d, against the bastions.
4:th, against the bastion retrenchment ; 6th, against the
retired retrenchment.
6th, and finally, against the bastions converted into cita-
dels by the fronts with which their gorges are closed.
According to the estimate of the time made by Choumara^
the time between opening the trenches and the final assauK
would be nearly three times as ffreat as it would be in Cor.
montaigne's method.
122. The complications of this method unfitted it for
practical application, even at the time of its design, and
render it useless as a fortification to oppose modern arms.
It combines, however, many of the features introduced into
permanent works by the best engineers who had lived
previous to the date of its design, and a large number
which, with changes in dimensions only, are to be found in
the most recently constructed outworks and detached forts.
While as a system it is obsolete, its details are well worth
«tudy.
70 ZLBHBlirCS OF PBBMAKENT FOBTIFIOAnOK.
CHAPTER m.
TBNAILLBD STSTBBC
123. Several engineers of professional eminence have*
proposed tenailled enceintes, as offering defensive properties
superior to bastioned enceintes. This system has found but
few advocates, and, except in particular localities, where the
natural features of the site demanded it, and for small works,
it has met with no practical applications.
Requiring that the salient angles shall not be less than 60°,
and the reentering angles between 90° and 100°, the tenail-
led system is only adapted to regular polygons of a suflScient
number of sides to admit of these conditions being satisfied.
If the exterior sides are kept within the limits usually
admitted by engineers for bastioned enceintes, the faces of
the tenailles become very long, and the reenterings very deep ;
thus presenting two serious defects — ^long lines which are^
very much exposed to enfilade, and a great diminution of
the interior space, as compared with the bastioned enceinte.
The ditches when dry can only be swept by casemated
defences in the reentering angles; and even then but.
partially, unless the casemated embrasures are placed very
near the level of the bottom of the ditch, in which case the-
enceinte would be exposed to a surprise through the em-
brasures ; and, in the contrary case, liable to a like attempt
from the dead space at the reenterings below the embrasures.
In wet ditches this exposure to surprise would be much less-
if the ditches could not be forded. In either case the de-
fect arising from embrasure casemates placed in a reenter-
ing angle would be a serious objection to using the guns of
each side simultaneously.
When the salient angles of the tenailles are acute, the
effect of the enfilading fire would not be felt alone on the
face enfiladed, but on the adjacent face or front, and shot
passing over would damage the adjacent tenailles.
The foregoing are the chief objections to this system. It
presents no advantage but the very illusory one, considering
the consequences arising from it, of long faces presenting &.
mutual flunking and cross fire of considerable extent.
XLEHBNTS OF PEBKAHTENT FOBTIPIOATIOlfr. 71
CHAPTER IV.
POLTGONAIi SYSTBBC
L
POLYGONAL SYSTEM.
124. The polygonal system bad previously been pro-
posed by several engineers of distinction, but its most ardent
advocate was the celebrated Montalembert, born 1714,
died 1800, whose views have been more or less carried out
in many of the constructions of Germany since his time.
Consisting of either a simple polygonal enceinte without
reenterings, the sides of which are flanked by casemated
eaponnieres, placed at the middle point of the fronts, or of
fronts either slig^'tly tenailled or of a bastion form, with
short casemated flanks to flank the faces of the central
eaponnieres, this feystem aflFords more interior space, and
from the mode adopted of flanking the enceinte, will admit
of much larger fronts than either the bastioned or the
tenailled systems. The salient angles moreover will be
more open in this than in the other two systems.
From these peculiarities of this system the positions suit-
able for the erection of batteries to enfilade the faces of the
enceinte are less advantageous, from their being thrown in
nearer to the adjacent fronts than in either of the other
systems ; whilst a greater development of trenches will also
he requisite to envelop the fronts of attack.
These obvious advantages for the distant defence, how-
ever, are counterbalanced to some extent for the close de-
fence by the want of the concentrated cross-fires which are
afforded by the enceinte itself, in both the bastioned and
tenailled systems, in advance of the salients, and upon the
ground generally in advance of the fronts.
Each front of the polvgonal system when its angles are
acute offers moreover a long line to enfilading and slant fire
which takes the adjacent front in reverse.
72 EtlESHESfTS OF PEBHAmEKT V0B9SFZOATI0N.
But the chief objection to this system lies in the mode
adopted for flanking the enceinte. The casemated capon-
nieres for this purpose being exterior to the enceinte, it will
be exposed to escalade as soon as the fire of the caponnieres
is silenced, which, considering the structure formerly
adopted for them and the exposure of their embrasures to
the enfilading batteries, would, in all probability, take place
at an early period after this fire is opened.
These detects in masonry caponnieres have been removed
in some degree as previously described, and those of iron
and steel, constructed and proposed, will probably resist the
most vigorous attack of the assailant. The advantages of this
system in its modem methods have led to its almost uni-
versal adoption. The new forts around Paris are polygonal
in their tntc^.
n.
HOirrALEMBEBT^S POLYGONAL METHOD.
125. Among the writers on permanent fortification
whose works have had an important bearing on the prog-
ress of the art, Montalembert holds a conspicuous place,
although not educated as an engineer. Struck by the
evident defects of the methods of his predecessors, partic-
ularly the want of casemates, both for defensive dispositions
for artillery and musketry, and the shelter of the garrison
and munitions, Montalembert devoted his time, talents, and
fortune to bringing about a change in the direction in which
it seemed to him called for. His efforts, however, led to no
modifications of consequence during his life, which was
principally spent in angry controversies with his opponents,
except the extension of casemated defences for searcoast
works ; but after the termination of Napoleon's wars a new
school of ensrineers grew up in Germany, based mainly upon
the views nut forth by Montalembert, which views met
favor in other parts, although still opposed by many able
engineers in all countries who contested their soundness.
The principal propositions of Montalembert consist :
1. In the entire rejection of the bastioned system, as, ac-
cording to his views, unsuitable to a good defensive disposi-
tion; and in its stead he proposed to use either the te^
nailled m/stem^ or else the poVygonaH eyatem.
SLEMEKTS OF PERMANENT FORTIFICATION. 73
2. In basing the strength of these last systems upon an
overwhelming force of artillery fire in defensive casemates.
3. In organizing strong permanent works within, and in-
dependent of the body of the place, wliich are to serve as a
secure retreat for the garrison when forced to give np its
defence.
Most of the objections urged against thebastioned system
and its outworks having already been adverted to in the
analysis of the front, it will be unnecessary to recapitulate
them here ; and as the tenailled system, composed of faces
of equal lengths with reentering angles of 90°, and salient
angles of 60 , and termed by Montalembert perpendicular
fortijicationy from the position of the faces at the reenter-
mgs, has many obvious and more serious defects than either
of the other two, it is proposed to give here a description of
the polygonal system alone, and that in its most simple
form — the one in which Montalembert presented it for the
fortifications at Cherbourg, one of the most important naval
stations in France.
126. Montalembert first gave the name polygonal system
to a trac6 of the enceinte m which all of tne angles are
-either salient, or where the reentering are very slight.
Flan. In the trac6 proposed for this place, x, y, (Fig. 1,
PI. 13,) is the exterior side, or magistral of the scarp. The
bod\ of the place consists of the scarp wall, d. Fig. 1 and
section on p q, arranged with casemates for artillery and
musketry ; of a corridor, o, between these casemates and the
earthen rampart and parapet, b. In rear of the rampart is a
Jiigh'wall, A, arranged with loop-holes, within which the gar-
rison retires when driven from the defence of the rampart.
Casemated caponnieres, m, which are secured from a coup-
de-^mairiy are placed along the rampart, and so arranged that
a fire can be thrown from them over the parapet and
also along the terre-plein. The corridor, c, is also swept by
a casemated caponniere, o, for musketry; and the front of
the wall, A, by a like arrangement.
The principal caponniere for flanking the main ditch is in
the form of a lunette, and placed at the middle of the exte-
rior side, its flanks joining the casemated gallery, d, of the
enceinte. The flanks, h, and the faces, k, of this work, are
arranged with two tiers of artillery and musketry fire ; each
flank carrying ten guns and each face twelve guns. A wet
ditch, I, separates the faces and flanks ; a loop-holed wall
•■•encloses the portion between the flanks, from which the
^opposite portion between the faces is swept by musketry.
74 ELEMENTS OF PBRMAKBNT FORTIFICATION.
The capoDniere is covered in front by a face cover, n, of
earth, in the shape of a redan. The scarp of the enceinte is^
covered in like manner by the continuous face-cover, o, of
earth, in the reeuterinff angles of which casemated batteries
of two stories, for artillery and musketry, are placed to flank
the ditches and sweep the positions for counter-batteries,
around the salients of the covered-way. These batteries are
masked in front by the earthen works, s and q. The whole
is covered by the glacis of the covered-way, arranged in the
usual manner.
The better to flank the main caponniere, the portion of
the casemated gallery joining it is arranged with two tiers
of artillery fire, the remaining portion having but one tier
of guns.
127. Profiles. The sections along p q, b s, and t it,
show the relative command of the different works and the
width of the ditches and earthen ramparts.
The communications between the aifferent works are by
bridges across the wet ditches.
128. It is now generally admitted that although Monta-
lembert has rendered important services to the progress of
fortification, particularly as regards the more extensive em-
ployment of casemated defences, still many of his projects
were visionary.
Many of the details of his system in the state of develop-
ment in which he left it may be said to have become obso-
lete without being subjected to trial by the guns which it
was designed to resist.
The improvement in artillery having rendered the com-
plete masking of masonry obligatory, compelled the advo-
cates of the polygonal system to introduce many modifica^
tions to accomplish this object.
129. Among these advocates. General Brialmont of the
Belgian engineers, born 1821, has in his writings and long
experience in the construction of fortifications, particularly
those of Antwerp, continued the development and improve-
ment of the system up to the present time. He proposes
in his latest works the extensive use of iron and steel case-
mates and turrets at important points, and in his earlier con-
structions displayed great skill in masking masonry from
the besiegers' nre.
130. The defences of Antwerp planned and carried on
under his direction since 1859 exemplify, better than any
other large work, the latest applications of the polygonal
system with its outworks. Plate 11, Figs. 2, 3, 4, 5, 6 and
ELEMENTS OF PEBMAKENT FOBTIFIGATIOlir. 75
7> show a half of one of these fronts of which the exterior
side is 1000 metres. The references and dimensions are in
metres.
The ditches, which are wet, are from 50 to 80 metres
wide and from 2 to 3 deep. They are flanked by a central
caponniere which is itseli defended by the first and second
flanks of the enceinte. These are protected from front fire
by being broken back and covered by orillons.
At the middle of the curtain is a defensible barrack^
which serves as a cavalier and retrenchment, and whose
front is masked by the caponniere and its wings.
The caponniere is covered by the connterguard, in front of
whose ditch, which is dry, and 15 metres wide, is a ravelin
with a ditch and covered- way.
The ravelin ditch is fianked by casemated low batteries^
serving as keeps for the reentering place-of-arms.
The salient of the caponniere, the salient angle being
about 60°, is 95 metres irom the exterior side. The cur-
tain is 65 metres within the exterior side and is 330 metres
in length.
The first and second flanks have a length of 31^ and 11
metres respectively. They are designed to flank the faces
and gorge of the caponniere, its flanks being swept by the
fire of its wings.
The curtain is made up of two half curtains and a de-
fensible barrack separated from each other by roadways
leading by bridges to the low terre-plein in rear of tne
caponniere.
The fianks of the caponniere, which have two tiers of
casemates, are separated by a court 70 metres long, 10
metres wide at its outer extremity, and 16 metres at the ex-
terior side.
Its wings are broken back and provided with a traverse
as shown.
The defensible barrack is of the form shown in the fig-
ure. The length of its head is such that it is masked by
the wing of the caponniere and the orillon. Its flanfe
make an angle of about 100° with the head, and are 75
metres long. The gorge is closed by masonry, forming a
keep for the front.
The salient of the connterguard is 165 metres from the
exterior side, and that of the ravelin 270 metres. The dis-
tance, E D, is 175 metres, and e b, 225.
The magistral of the low battery flanking the ravelin
V6 EZiXKKsrrs of pbbmaxbnt fobtificatiok.
4iteli hBA a length of 50 metree^ and makes an angle of 120^
with that of the ravelin.
The covered-way of the main work is 20 metres wide,
that of the ravelin from 8 to 14 metres, and arranged as
shown.
The parapet of the ravelin is broken as shown, to prevent
enfilade and is provided with a traverse and a '' reverse bat-
terv" near the salient, sweeping the ground in front of the
salient of the main work, whidi salient usually contains a
-cavalier.
The communications, which are shown in the plan, are
<iirect, broad, and well protected.
The sections give the profiles of the enceinte and its out-
works. Fig. 5, section on e f^ shows a modification of the
defensible barrack proposed by Brialmont, to give better
protection to the masonry.
The parapets are generally 8 metres thick. The case-
mated quarters will accommodate 2000 men.
This enceinte is strengthened bv a belt of polygonal de-
tached forts placed in defensive relations with each other at
a distance ox about 1^ miles apart, and f^om 2 to 3 miles
from the enceinte.
KoTB. — ^Full descriptions of the details of this front, with an analysis
of its different parts and some proposed modifications, wiU be found in
Brialmont, '*Trait4 de Fortification Polygonale/' Paris, 1869.
ELKHKNIS 01 PBBICAKBNT 70BII7IOA.TIOK. IT
CHAPTEB V.
BZISTINO OBBMAM FOBTZFIOATIONa
L
BBOENT GEBSfAN FOBTIFIOATIONS^
131. In the large additions made to the fortifications of
the German States, between the general peace in Europe in
1815, and the close of the Franoo-Pnissian war in 1871, the
German engineers for the most part of these strncturea
embraced the ideas put forth in the works of Montalembert
and Camot, adopting for the plan of their enceintes th©
polygonal system with flanking caponnieres^ combining^
with these numerous casemates for defence, for bomb-proof
shelters, for quartering the troops and preserving the muni-
tions and other stores.
132. From what has been published on this subject by
^he German engineers themselves and other European writ-
ers, the following appear to be the leading features upon
which these works are based :
1. To occupy the principal assailable points of the posi-
tion to be fortified by works which shall: contain within
themselves all the resources for a vigorous defence by their
garrisons ; these works being placed in reciprocal defensive^
relations with each other, out so arrangea that the fall-
ing of one of them into the besieger's hands will neither
compel the loss of the others nor the surrender of the
position.
2. To cover the space to the rear of these independent
works either by a continuous enceinte, usually of the poly-
gonal system, with a revetted scarp of sufficient height to
secure it from escalade ; the parts of this enceinte being so-
combined with the independent works in advance that all
the approaches of the besiegers- upon each, both dufing^
the near and distant defence, shall be swept in the most
78 ELEMENTS OF PERMA17EKT FOBTIFIGATION.
effective manner by their fire; or else to connect these
works by long curtains ; or, finally, to employ them, as in- a
system of detached works, either to occupy important points
in advance of the main work, or for formmg capacious
intrenched camps with a view to the eventualities of a
war.
3. To provide the most ample means for an active defence
by covered- ways strongly organized with casemated redoubts,
and with spacious communications between them and the
interior for sorties in large bodies.
4. So to organize the artillery for the near defence that
it shall be superior to that of the besiegers at the same
epoch, and be placed in positions where it will be sheltered
from the besieger's guns up to the time that it is to be
brought into play.
133. The plan of the independent works may be of any
polygonal figure which is best adapted to the part assigned
them in the defence of the position ; but they are generally
in the form of lunettes, (PI. 15, Fig. 2,) having a revetted
scarp and counterscarp to secure them from escalade.
In the gorge of the work a casemated defensive barrack
is placed, which serves as a reduit or keep ; a simple loop-
holed wall which is flanked by the barrack closing the space
between it and the flanks of the work, and securing the
latter from an assault in the rear. The ditches of the work
are either flanked from the enceinte in the rear ; or, when
the work is a detached one^ by caponnieres, or counterscarp
galleries. The work is usually organized with a covered-
way having one or more casemated redoubts, and a system
of mines both for the exterior and interior defence.
134. The defensive barrack is usually arranged for two
or three tiers of covered fire, and an upper one with an
ordinary parapet and terre-plein on which the guns are
uncovered and destined for the distant defence. The two
upper tiers of covered fire are for artillery, to sweep the
interior of the work, and to reach by curvated fires the
approaches on the exterior. The lower tier is loop-holed
for musketry to sweep the interior. The barrack is sur-
rounded by a narrow ditch on the interior, and this, when
necessary, is flanked by small caponnieres placed in it, which
are entered from the lowest story. The barrack communi-
cates with the interior by a door at some suitable point ; and
the communication between the interior of the work and the
exterior is through doors in the^wall enclosing the gorge.
ELEMENTS OF PEBMANElirT FOBTIFICATIOK. 79
135. Considerable diversity is shown in the profiles of
these works. They usually consist of a parapet and rampart
of ordinary dimensions for the uncovered defence ; of scarps
either partly detached and loop-holed, with a corridor
between them and the parapet ; or of scarps with relieving
arches arranged with loop-holes for musketry ; or of a com-
bination of these two. The height of the barrack, and the
command of the parapet of the exterior work, are so deter-
mined that the masonry of the former shall be perfectly
covered from the direct fire of artillery, and the exterior be
perfectly swept by the artillery of the work. The portions
of the counterscarps at the salients are also arranged with
defensive galleries to sweep the ditches ; usually with mus-
ketry, but in some cases with artillery.
136. Casemates are arranged for mortars in the salient
angles of the work, to fire in the direction of the capitals ;
and one or more casemated traverses are placed on the terre-
plein, to obtain a fire on the exterior and to cover the terre-
plein from ricochet. The masonry of these traverses is
masked bv the parapet.
137. f^osterns lead from the interior of the work to the
scarp galleries, the corridors, the ditch caponnieres, and the
casemated mortar battery in the salient.
138. The system of mines for the exterior defence consists
simply of listening galleries leading outwards from the coun-
terscarp galleries. That for interior defence is similarly
arranged ; the communications with it being either from
the barrack caponnieres, or from the counterscarp of its
ditch.
139. The work is provided with powder magazines which
are placed at the points of the intenor least exposed to the
enemy's fire; and covered guard-rooms, store-rooms for
mining tools, etc., are made in connection with the posterns.
140. In the profiles of their works, the German engineers
follow nearly the same rules for the forms and dimensions
of their parapets as those in general use in other services.
They employ three kinds of scarp revetments.
1. The ordinary full revetment, or sustaining wall, with
counterforts.
2. Revetments with relieving arches, either with or with-
out defensive dispositions, as circumstances may demand.
3. Scarp walls either partly or wholly detached from the
Tampart and parapet.
In all these cases, they give to their scarp walls a height
80 ELEMENTS OF PERMANENT FOBTIFICATION
from 27 to 30 feet for important worka ; and about 15 feet
for those less so. The batter of these walls is usually one
base to twelve perpendicular. For the full revetment with
counterforts, they regulate the dimensions of both so as to-
afford the same stability as in the revetments of Vauban.
In their revetments with simple relieving arches, they
nse either one or two tiers of arches ; placing the single tier
either near the top, or towards the middle of the wall,
according to the nature of the soil and the pressure to be
sustained.
Revetments with relieving arches for defence, or scarp
galleries, are arranged for one or two tiers of fire. The
back of the gallery is sometimes left open, the earth falling
in the natural slope in the rear ; or it is enclosed either witn
a plane or a cylindrical wall, according to the pressure to be
sustained.
When the upper part of the wall is detached, to form a
corridor between it and the parapet in its rear, the top por-
tion alone is, in some cases, arranged with loop-holes and
arcades, or with recesses to their rear, to cover the men
from shells ; in others, a scarp gallery is made below the
floor of the corridor to give two tiers oi fire. The corridora
are from 8 to 20 feet in width ; and when deemed requisite,
they are divided, from distance to distancCj by transverse
loop-holed traverse walls for defence.
When the scarp walls are entirely deteched, thev are,
arranged for either one or two tiers of fire, with arcades to
cover the men ; the banquette tread of the upper tier of loop»
holes resting on the arches of the lower tier of arcades.
The counterscarps are revetted either with the ordinary
wall, or arranged with a defensive gallery with a full centi^&
arch, parallel to the face of the counterscarp wall.
141. The German engineers make a liberal use of bomb-
proof casemates for mortar and eun batteries. The former
are either placed in the rear of the parapet, or of the ram-
part and along the faces; or else in a salient angle.
In the former case, they are covered in front by the para*
pet; in the latter, either by the scarp wall alone, or by a
casemated defensive mask, placed in front of the battery.
When placed along the face (PL 6, Fig. 50), they are
arranged for one or several mortars, and treqoently with
two tiera of arches, the upper one for the service of the
mortar, and the lower one for a bomb-pfoof shelter for
troops^ or munitions. The chamber occupied by each noor*
tar is a rectangle 12 feet wide and about 20 feet in depth ;
ELEMElirrS OF PEBMAKEKT FOKTIFICATIOK. 81
this is covered by a full centre rampant arch, the height of
the piers at the back of the chamber bein^ 4 feet and in
front from 6 to 9 feet above the level of the mortar-plat-
form. This enables the shell to clear the top of the para-
pet in front, which is about 12 feet above the level of the
platform, and 21 feet in front of the battery.
The chamber is, in some cases, left open both in front
and rear, to allow the smoke to escape readily, and to
diminish the effect of the concussion of the discharge on
the masonry ; in other cases it is closed by a wall m the
rear ; an opening being left in this wall immediately under
the arch for the same purpose.
A small ditch is placed in front of the battery ; and the
wall in front is extended about three feet above the plat-
form, to shelter the men from the explosion of shells that
may fall into the ditch.
The abutments of the arches are 7 feet thick and the piers
4 feet. The arches are two feet 6 inches thick ; they are
covered on top by from 4 to 6 feet in thickness of earth ;
and. in like manner, the arch and abutment are secured on
the side exposed to an enfilading fire.
An ordinary traverse is placed on the same side, to cover
the masonry and communication between the front of the
battery and the parapet ; the chambers of the mortars are
entered from the front, or from the sheltered side, by a
door in the abutment.
When placed in an obtuse salient, behind a scarp with a
corridor, a space of 10 or 12 feet is left between the back of
the scarp wall and the front of the battery. The platforms
of the mortars are about the same distance below the top
of the scarp. The arches are covered bv the earth of the
parapet to the depth of 5 or 6 feet. The dimensions and
arrangement of tne chambers and arches are the same in
this as in the preceding case.
The communication from the interior of the work to the
battery is by a postern 6 feet in width. A casemated
guard-room le ma^e in connection with the postern ; and
when the scarp is arranged with relieving arches, either for
defence or for other purposes, an arched stairway is in some
cases made as a communication from the postern to the
casemates. A transversal wall with a doorway serves to cut
oflE the court in front of the battery from the corridor to
the rear of the wall.
In the less obtase salients, the front of the battery is
8^ EUSUEKT8 OF PEBM ANBNT FOBTIFIOATIOIf.
made drcnlar ; the chambers being bo placed that the fire
of the mortars can be thrown in the direction of the capital.
A casemated defensive traverse, placed in the salient, masks
the batterv in front ; and it is covered on the flanks by the
earth on the top of the arches. The details otherwise are
the same as in the preceding case.
142. In the arrangement of casemated traverses for
guns (PI. 6, Figs. 48, 49), the chamber for each gnn is a
rectangle 24 feet in depth, estimated from the interior crest
of the parapet, and 12 feet wide. The chamber is covered
by a full centre arch, the height from the level of the plat-
form to the crown of the arch being 8^ feet. The arcn is
2 feet thick, the piers between the arches 3 feet, and the
abutments 3^ feet. The mask wall in front of the cham-
bers is 3 feet thick. This wall is covered in front by the
parapet, and by several layers of fascines, or of heavy tim-
oer laid across the embrasure in the parapet and above the
one through the mask wall. The cheeks of the embrasure
in the parapet are likewise revetted with heavy timber at
some distance in front of the mask wall. The masonry is
covered on top and on the sides with 5 or 6 feet thickness
of earth, to secure it from shells and enfilading shot. The
casemates are left open to the rear.
In some cases, a blinded battery for a single mu (PI. 6,
Fig. 49), is arranged by enclosing the sides and £ont of the
chamber with walls, and covering it with a layer of heavy
timber, supporting two thicknesses of large fascines, cov-
ered with a thickness of 5 or 6 feet of earth ; the dimensions
of the chamber are the same as in the preceding case.
148. The caponnieres (PI. 5, Figs. 37, 38), for flanking
the main ditch, usually consist of two faces and two case-
mated flank batteries of two stories each ; the lower story
being loop-holed for musketry, and the upper pierced for
artilfery. Each battery consists of severnl rectangular cham-
bers ; each chamber for a single gun being 12 feet wide and
24 feet deep ; or of smaller dimensions, according to the
calibre of the gun and the kind of carriage on which it is
mounted. The upper chambers are covered with bomb-
J)roof arches, the lower one by arches of sufficient strength
or the weight thrown upon them. The front mask wallof
the casemates is 6 feet thick ; the wall in the rear is 3 feet
thick and is pierced with windows for light and ventilation.
Openings for the escape of the smoke are also made in the
front mask wall immeaiately below the crowns of the arches.
ELEMENTS OF PEKMAKEIH? POBTIFIOATIO)^^, 83
Jkn interior eourt 80 feet in width is left between the two
^nk batteriefi, and when the batteries are detached from
the scarp wall the space between is enclosed bv a loop-holed
wall built on each side in the prolongation of tne front mask
wall.
The faces of the caponniere form a salient of 60°. They
are separated from the flanks by two stories of arched corn-
dors, m front of which are two arched chambers of two
«tories; the upper chamber being arranged for mortars.
An open triangular court is left between the front walls of
these chambers and the faces of the caponniere. The upper
part of the walls of the faces along tnis court are arranged
with arcades and loop-holed for musketry, and have an open
•corridor in their rear on the same level as the chambers of
the second story.
The caponniere is provided with a powder magazine and
other necessary conveniencies for the defence.
The flanks of the caponniere and its interior are swept by
the musketry of the scarp galleries in its rear. The faces
in like manner are swept by artillery and musketry in case-
mates behind the scarp.
The arched chambers of the upper story are covered by a
thickness of 5 or 6 feet of earth.
144. Caponnieres of smaller dimensions, termed hastion^
nets (PI. 5, Fig. 39), placed at the angles of redoubts to flank
the ditches, are usually arranged for musketry, but some-
times receive artillery. Those for flanking the ditches of
the independent worKs in advance of the enceinte, are some-
times placed in the ditches of these works ; sometimes be-
hind the scarp wall of the enceinte ; and sometimes in case-
mates in the main ditch, detached from the scarp wall.
The communications from the interior with the capon-
nieres are by posterns.
146. The defensive barracks, forms one of the most dis-
tinctive features in the organization of the German fortifi-
cations. The plan of these works may be of any figure to
suit the object to be subserved by them. When placed in
the gorge of an independent worK and serving as a keep to
it, their plan is usually semicircular. (PL 15, Fig. 2.)
The barrack consists of one or two stories of arched
chambers for covered fire, and an open battery on top with
an earthen parapet and terre-plein.
The arched chambers are formed by connecting the front
and rear walls of the barrack by transversal walls which
84 ELEMENTS OF PERMANENT FORTIFICATION.
serve as piers for the arches of the ceiling, the soffits of
which are either cylindrical or conoidal, according as the
piers are parallel or otherwise. The chambers are about 18
to 20 feet wide, and 60 feet in depth ; their height, under
the crown of the arch, from 9 to 11 feet. The arch of the
highest chamber is 2J feet thick, and being covered with a
capping and the earth of the open battery on top, is bomb-
proof. The arches of the lower stories are 1^ feet thick.
The front wall of the barrack is usually 6 feet, and is pierced
in each chamber with one embrasure and two loop-holes.
The rear wall is 3 feet thick, and has a window in each
chamber for light and ventilation. Openings for ventilation
are also made in the front wall just beneath the crowns of
the arches. Doorways are made through the transversal
walls to form a communication between all the chambers.
These are sometimes placed along the centre of the piers, at
others near their extremities, so that the chambers beings
divided by slight partitions into two compartments for the
quartering of the troops, there will be a continuous hall
either along the centre, or near the rear wall, upon which
all the apartments open. The barracks are, otherwise^
arranged with all the requisites for lodging the troops com-
fortably and healthfully. The lower story of the barrack iff
surrounded by a narrow ditch. A drawbridge across thisk
ditch secures the entrance to the barrack at the gorge.
In some cases where the front wall of the barrack is much
exposed to the besieger's fire, the piers are made thicker
nearer the front wall; and they each have two vertical
grooves to receive timber, laid horizontally, between which
sand-bags can be packed in to afford shelter when the front
wall has become much damaged by the besieger's artillery..
146. Remarks. The foregoing summary description,,
with the plates, will give a good general idea of the princi-
pal defensive arrangements constructed of masonry which
enter so largely into the existing German fortifications, and
upon the details of which the German engineers have be-
stowed great attention.
The adoption of the polygonal system, with caponni^re
defences for the main ditch, has enabled the German engi-
neers to give, in their fortilications, a greater exterior side
than in tlie bastioned system generallj^, and still admit of
lines of defence, in which grape, canister and small arms,,
particularly the later improved musket, will tell with effi-
cacy upon the besieger's works on the glacis around the
ELEMENTS OF FEBMANENT FORTIFICATION. 85
«alieDt8 of the enceinte. With a few exceptions, nothing of
a very reliable character has been published as to the plan
of these works, further than the general defensive disposi-
tions. From these it appears that, keeping in view the
<jardinal point in all fortification, the adaptation of the vari-
ous fronts to the site of the work, so that all the approaches
upon them shall be commanded and swept by tneir fires,
whilst the principal lines of the enceinte receive the best
direction to place them as little as possible within the range
of enfilading positions, the exterior side is usually kept
-somewhere between 500 and 600 French metres, or between
550 and 700 vards.
147. This system of fortifications being in existence
before the recent improvements in arms and the works
being located in accordance with correct principles, the
<;hanges required in them are of detail and dimensions
rather than of principle. The principal changes of a gen-
eral character are : 1st, in reducing the number of strong
places, retaining those guarding the frontier, and those
-covering strategic points, large depots of supplies and cen-
tres of production. These include generally centres of com-
munication and some of the large cities. 2d, in enlarging
the detached forts, placing them further from the centre of
defence (from 4 to 8 miles) and making them much stronger,
placing in the intervals between them, when necessary,
smaller redoubts or batteries, thus making an exterior line
of defence of great development and within which large
armies can be assembled ana manoeuvred.
The existing enceintes enclosing cities thus fortified will
in general be retained, or, as at Cologne, replaced by a con-
tinuous enclosure, without outworks, generally polygonal,
ivith flanking bastionettes, provided with revetted scarps and
<50unterscarps ; the parapet being arranged for infantry, and
fleld or garrison guns of moderate calibre, the whole being
•designed for security against attack or escalade by any force
breaking through the outer lines, but owing to its prox-
imity to the city not intended to withstand regular ap-
proaches.
The detached works already built may be used as a second
line, or in many cases destroyed.
The fortifications of those cities which are not strength-
ened, and the small forts not included in the classes named,
may be either retained unaltered or torn down.
The principal changes required in the details of the works
described in order to fit them for defence are as follows, viz. :
86 ELBMElirTS OF PERMAKENT FORTIFICATION.
The covered-ways should be reduced in width, to draw
their crests nearer the scarp wall. The defensive barracks,
keeps, bastionettes, and caponnieres, should be cut down to
one tier of fire, their face-walls masked and their arches
covered with a sufficient thickness of earth to render them
bomb-proof. All casemates exposed to direct fire must be
thoroughly masked or shielded with armor.
The scarp walls may be reduced to a height of from 1^
to 23 feet, according to the importance of the work, and
covered against a plunging fire by the glacis. Wing bat-
teries for fianking and ditch defence may be built outside
the work in the continuation of the gorge, and other changes,
made to bring them so far as practicable into conformity
with the most recent constructions.
IL
FRONTS OF POSEN.
148. The following is an outline of the plan and de-
fensive dispositions of a front of the fortifications of Posen^
one of the most noted of these structures.
The exterior side, ab, (PL 14, Fig. 2), is 600 yards ; a
distance, od = -j^ ab, is set off on the perpendicular to the
front and without it ; and on the line joining the salients^ a,
B with D, distances, ah, bh, equal ^ ab, being set off, give
the faces of the front.
The salient, e, of the independent work is on the per-
pendicular of the front, and at a distance from o equal to j^
AB. Describing from e an arc with a radius of 20 yards,
and drawing tangents to it from the points h and m, gives
the counterscarps of the independent work ; the faces, ef,
ef', are parallel to the counterscarp and equal i ab.
The ditches of this work are flanked by casemated capon-
nieres, hi, mn, which are 35 yards in length, or sufficient
for four guns ; the directions of these fianking casemates
being nearly perpendicular to the direction of the faces ef'.
The flanks, ro, f'g', receive the most suitable directions for
sweeping the approaches in advance of the salients of the
front.
The main ditch is about 30 vards wide, its counterscarp
being parallel to the faces of the enceinte ; and the gorge
of the independent work is on the prolongation oi this^
counterscarp.
The curtains of the enceinte are directed from the points.
ELEMENTS OF PEBMANEKT FORTIFICATION. 87
I, N on the point c, and are thus nearly parallel to the ex-
toior side.
The main ditch is flanked by a large, casemated, defensive
barrack, having three stories of covered fire, the lower for
mxisketry and the upper for artillerv, and an open battery
on top. The plan of this work is that of the letter u ; the
circular part projects within the independent work, and
series as its keep ; the sides are nearly perpendicular to the
faces of the enceinte, and are prolonged within the enceinte, *
serving as a defensive caponniere to flank the main ditch,
to sweep the terre-pleins of the enceinte curtains, and also
the interior within the range of the guns of two round
towers with which the sides are terminated. The sides of
the barrack are separated from the rampart of the curtain by
lateral ditches 10 yards wide, which give access to the main
ditch from the interior for troops in large bodies for sorties.
The parapet of the enceinte (Fig. 4) is thrown back from
the scarp, leaving a corridor between the foot of its ex-
terior slope and the scarp wall, the floor of which is 12 feet
above the bottom of the main ditch.
The scarp wall rises 16 feet above the level of the floor,
thus giving it a total height of 28 feet above the bottom of
the main ditch. This wall is loop-holed for small arms.
The counterscarp wall of the main ditch is 24 feet in
height.
The faces and flanks of the enceinte have a relief of 44
feet ; the relief of the curtain being only 40 feet.
The corridors of the curtain terminate at the court or
open space behind the flanking casemates, hi, mn.
Posterns lead from the interior to the corridors of the
faces and flanks, and from the lateral ditches to the cor-
ridors of the curtain.
The interior open space between the sides of the de-
fensive barrack is closed by a loop-holed wall between the
end towers. A ditch surrounds the towers and the gorge
between them, across which a bridge, terminated at the wall
by a draw, gives access to the interior open space and the
barracks.
149. The scarp, rampart and parapet (Fi^. 5), of the
independent work are arranged witn a proflle similar to that
of the enceinte. The circular portion of the defensive bar-
rack which serves as the keep is surrounded by a ditch,
which is swept by small caponnieres attached to the keep.
A circular mortar battery, covered in front by a casemated
traverse, is placed in the angle of the independent work
Q8 ELEMENTS OF PERMANENT FOETIFICATION.
and behind this a casemated battery for howitzers is placed
on its terre-plein, in the direction of its capital, to give reverse
fire on the glacis of the collateral independent works. The
gorge of this work is closed by a loop-holed wall which ex-
tends between the keep and the scarp wall of the flanks.
The communication between the main ditch and the in-
terior is through a gateway in this wall. Posterns lead
from the interior to the corridors of the faces and flanks,
and to the mortar battery in the salient.
160. The counterscarp of the independent work is ar-
ranged with a defensive gallery, with which a system of
mines for the exterior defence is connected. An interior
system of mines is connected with the small caponnieres in
iiie ditch of the keep.
151. The covered-way is without the usual traverses, its
interior crest being broken into a cremailliere line. Its
salient and reentering places-of-arms are occupied by case-
mated redoubts. The communications from the main ditch
to the covered-way are by wide ramps which are at the
gorges of the reentering places-of-arms and under the fire
of their redoubts.
m.
FOBT ALEXANDER.
Among the most reliable of the published plans of Grer-
man fortification is that of the main front of Fort Alexander,
a detached quadrilateral work of the fortifications of Oob-
lentz, given oy Colonel Humphrey of the British Army.
152. Flan. The exterior sides of the enceinte of this
fort (PI. 14, Fig. 6) form a parallelogram, the acute angles
of which are 85°. The main and rear fronts are each 500
yards, and the other two 420 yards each. The main front
IS of the polygonal system, with a strong defensive capon-
niere to fiank the main ditch.
The caponniere is covered by a demi-lune, and the salients
of the enceinte by counterguards ; the ditches of these
works being flanked by casemated batteries at the reenter-
ing formed between them.
There is no covered-way in front of these outworks, their
counterscarps being of earth with a gentle slope. A small
earthen work, containing a casemated redoubt, is thrown up
at the salients of the counterguard counterscarp.
To construct the trag^, take ab = 500 yards for the ex-
terior side of the enceinte, which divide into three equal
ELEMENTS OF PERMANENT FOETIFICATION. 89
parts, ad = de = eb. Bisect ab by a perpendicular on which
fiet off hn = hd = he = ^ ab. Through h drawing a paral-
lel to ab and setting off along it the distances ha = hb =
520 yards, the points a and b will be the salients of the
counterguards.
From H, as a centre, with the radii nd = ne, describe two
arcs, on wliich set off from d and e the chords di = ek = 33
yards, these will be the lengths of the casemated flanks ; ik
being joined gives the enceinte curtain.
The salient angle of the main caponniere is constructed
by drawing from a point, m, on the capital, at a distance of
50 yards from the lines nd, ne, lines to the extremities i and
k of the casemated flanks. The flanks of the caponniere,
tn = vo, extend back to the exterior side, and are 33 yards
in length and 33 yards apart; or each 16^ yards on each
aide of the capital.
The faces of the counterguards are directed on the point
■0 = -j^ AB = 53i yards on tne capital from h.
The salient f, of the demi-lune is 4 ab = 106 yards from
the point o; its faces fd, fe, are parallel to the lines Hd,He,
which last, joined by an arc of a circle described from m as
a centre, with a radius of 20 yards, and terminated at the
counterscarp of the enceinte aitch, which is 28 yards from
ab, will give the demi-lune gorge.
A casemated battery for 3 guns, behind the demi-lune
«carp wall, flanks the counterguard ditch; and one for 3
^ns flanks the demi-lune ditch, and closes the opening be-
tween the demilune and counterguard at this point. A
narrow ditch 10 feet wide is left between the flank of this
l)attei'y and the extremity of the counterguard, as a commu-
nication between the main ditch and the ditches of the out-
works. This opening is masked by an overlap of the coun-
terguard.
Casemated, or blinded, batteries are made in the salients
of the enceinte and of the demi-lune.
153. The main caponniere (Fig. 8) has two tiers of
covered artillery fire on the flanks, of 5 guns each ; the
lower to sweep the main ditch, the upper the terre-pleins of
the counterguards ; its faces have two tiers of loop-holes. It
has no uncovered fire, but a simple covering of earth as a
bomb-proof.
154. Casemates for five mortars each, are placed in the
salients of the enceinte at the foot of the rampart slope.
155. A narrow corridor (Fig. 7), the floor of whicn is 4i
feet above the bottom of the main ditch, is left behind the
90 ELEMENTS OV PEBKAKBNT FORTIFICATION'.
flcarp wall of the enceinte ; the faces and curtains of thi^
wall are loop-holed and arranged with arcades to shelter the
men, like the detached scarp walls of Oamot. These scarps^
are 21 feet high. The height of the enceinte above the
parade is 26 feet.
166. The scarp walls of the demi-luneand countergnard*
(Fig. 7,) are arranged like those of the enceinte. The com-
mand of these works is 16 feet. Their counterscarps are
arranged at the salients with loop-holed galleries, from,
which communications lead to a system of mines for ex-
terior and interior defence.
167. The rear side of this fort, not being exposed to
artillery, is simply closed by a loop-holed wall and ditch. A
large, circular, defensive barrack occupies the centre of thifr
rear front, serving as a keep to the fort, and to sweep by its.
fire the ground on the rear and flanks of the front.
168. Up to 1883 no changes had been made in this or
the other works about Coblentz, but additional detached
works had been built further from the city.
169. Remarks. It will be seen that in the arrangement
of the plan of this work, the polygonal system, with capon-
niere aefences, of Montalembert, has been adopted as the
basis, with such modifications as the features of the site
afforded to withdraw the principal lines from the range of
enfilading views.
The German engineers apply the preceding dispositions
to ever^ class of detached works, whether within reach of
the artillery of the main work or beyond it.
In the former case the work is either in the form of a
lunette or a redan, according to the requirements of the
site ; the gorge of the work being secured by a slight loop-
holed wall that can be readily destroyed by the artillery of
the place ; and thus open its interior to view when occupied
by tne besieger.
In the latter, the plan is that of polygonal redoubt en-
closed on all sides by a parapet.
The ditches in all such cases are flanked by small capon-
nieres, placed at the angles of the work, and arranged both
for musketry and artillery ; besides having a counterscarp
ffallery which serves as the point of departure for the gat
feries of the exterior system of mines.
The apparently wide divergence between the German
fortification of the present day and the bastioned system,
which last had been adopted as the normal one throughout
the world until these innovations were practically mtro-
ELEMBirrS OF PEBMAlTElJrr FOBTIFICATIOK. 91
dttced, has ^ven rise to active diecnssions among engineers
in Europe, m which, as in all cases, very nltra ground has
been taken bj both parties to the dispute.
160. In each system the points admitted as essential in
all fortification of a permanent character are sought for^
viz.:
1. An enceinte secure from escalade and thoroughly
flanked by artillery and small-arms.
2. Such an adaptation of the plan of the enceinte to the
site as shall secure, as far as practicable, the principal linea
from enfilading views.
3. Outworks and detached works oi sufficient strength ia
themselves, and of such defensive relations to the enceinte,
as to force the besieger to carry them by regular approaches!
before being able to assault the enceinte.
4. Interior defensive works, or keeps within the assail-
able points of the enceinte ; and also in the outworks first
sublect to an attack, to give confidence to their garrisons in
holding out to the last extremity.
5. Tlje means necessary for an active defence.
6. The use of mines as an auxiliary.
7. The protection of all masonry by earthen masks from
the distant batteries of the besieger.
The onl^ question then is b^ which of these two systems-
the object in view is best attamed.
161. The polygonal trace which obtains in most of the
recent German works has certain prominent advantages and
defects which may be seen by a slight comparison with the-
bastioned system.
As the exterior sides are longer and the reentering of the
enceinte less deep than in the bastioned systems, it follows r
1. That the interior space enclosed by the enceinte i»
greater in the polygonal trace.
2. That the faces of the enceinte are less exposed te
ricochet from the greater obtuseness of the salient angles.
3. That the fire of the faces has thus a better bearing on
the distant defence.
4. That, requiring fewer fronts on a given extent of line
to be fortified, there will be fewer flanks and more artillery
therefore disposable for the faces and curtains.
5. That, in the usual mode of attack, the besiegers will be
forced into a greater development of trenches for the same
number of fronts.
162. Its defects are :
1. That the enceinte, having no other flanking defence
j92 ELEHEirrs of permanekt fortification.
than the main caponniere, will be exposed to an escalade so
soon as the fire of this defence is silenced.
2. That the progress of the besiegers during the last and
most important period of the siege is but little delayed,
owing to the slighter reenterings formed by the independent
works in front of the enceinte salients.
163. The defects in the bastioned trac6 and the modes
J)roposed by different engineers to remedy them, particu-
arly those of Choumara, nave been sufficiently dwelt upon
to snow that, with the advantages inherent in this trace of
{)re8ervinff the means of flanking the enceinte ditch to the
ast ; of throwing the bastion saGents into deep reenterings ;
tmd giving a better direction to the enceinte faces for sweep-
ing the ground in advance of the demi-lune salients ; it is
susceptible of receiving all the means of caseraated de-
fences ; of a great development of flank fire ; of defensive
arrangements of mines; of ample communications for an
active defence ; and an extension of the exterior side forti-
^ed commensurate with the improvements of late years in
artillery and small-arms.
This last, together with a shorter perpendicular to the
front, giving relatively shorter flanks, the breaking back of
ihe parapet in the polygonal front for flanking the capon-
nieres, the introduction of armored casemates and turrets
ior flanking the ditches, the extensive use of covered de-
fences, the simplification of the outworks and reduction in
their command in both systems, have materially diminished
the marked points of dinerence, and have brought the two
systems more nearly into equality for both the close and
distant defence.
164. In the discussions which have taken place upon the
merits of these two traces, between engineers of the two
rival schools, each has seemed disposed to exaggerate the
defects, and to depreciate the advantages of the system
analyzed, and has conducted his mode of attack accordmgly.
The true point, however, as to the inherent merits of the
•question, does not lie in a comparison of the means of resist-
ance of a bastioned trace with defective communications and
without casemated defences and mines with that of the
Oerman system, but between the former with these addi-
tions, now regarded by engineers of every school as indis-
pensable to a vigorous defence against the greatly improved
means of attack of the present day, and the latter.
In these discussions many considerations arising from the
ELEMENTS OF PERMAlirENT FORTIFICATION. 93*
immediate vicinity of the protected city to the fronts of
attack have been introduced.
The great range of modern guns has made it impossible
to defend a city from its immeSate suburbs, and has led to
arranging for both close and distant defence the forts of th&
belt or belts encircling the place, leaving for the enceinte
only the duty of protecting the city from the attack of an
army (perhaps large) which may break through the outer
line.
The enceinte to satisfy the conditions requisite for this
defence must be proof against assault or escalade, but will
not require elaborate outworks or interior retrenchments.
The cheapest and simplest system, either polygonal or
circular, or a combination of them, will be in general
adopted.
The outworks will be restricted to those necessary to pro-
tect the gates ; the interior retrenchments to those required
to keep the disorderly element of the inhabitants in sub-
jection.
For the detached works, subject to regular approaches,,
the relative values of the rival systems must be oetermined
by the circumstances of the particular case to which they
are to be applied.
M EXJOCElirEa 01 FEBMASJWl I0BTI7I0ATI0N.
CHAPTER VI.
DETAOHED F0BT8.
165. For reasons previously stated, the main line of de-
fence of fortified places is now at the belt of detached forts
instead of at the enceinte. These forts have acquired all
the additional value due to this fact, and the latest develop-
ments in the art of fortification, for land fronts, are to he
found in the newest detached works of the German, French,
and Belgian engineers.
166. These forts are as a rule polygonal, the traces gen-
erally adopted are a long straight front with two flanks and
A gorge, which may be rectilinear, tenailled or bastioned ; a
lunette with a very obtuse salient ; or a modification of the
lunette which has three or sometimes four faces and two
flanks. The character of the gorge is determined, in all
cases, by tjie nature of the site or the individual views of
the designing engineer.
The faces and flanks of these forts which give a direct fire
to the front have together a length of from 300 to 700 yards.
The depth of the forts from front to gorge is a minimum con-
fiistent with suflScient interior space for the accommodation
of their garrisons which vary from 500 to 1000 men. The
armament of the largest is about 30 guns. Plate 16, taken
from a German authority, shows the details of one of these
works.
Their parapets have a command of from 25 to 40 feet at
the salients and fall oflE towards the fianks and gorge for
defilade.
The faces and flanks receive a thickness of from 20 to 25
feet and the gorges about 15 to 18 feet. The ditches have
a minimum depth of 20 and width of 30 feet.
The scarp walls are generally detached or semi-detached
and loopholed for defence.
They have such height, usually not less than 16 feet, as
to be well protected by the glacis.
BLBMBNT8 OF PBBHAKENT FOBTIFIOATIOK. 95
The counterscarpB are generally revetted with masonry
walls with relieving arches, which lend themselves to the
€onstraction of counterscarp galleries for sweeping the
ditches and for starting points for countermines. The faces
^u^ flanked by artillerv, machine guns or infantry fire from
•caponnieres, and the flanks by caponnieres or scarp galleries,
a sheltered emplacement for which is obtained by breaking
back the scarp wall at the shoulder angles and forming a
kind of orillon, in the rear face of which the casemates are
placed.
167. The interiors of the forts are provided with abund-
ant bomb-proof cover for the garrison and supplies, and
with chambers in which the guns may be placed when
temporarily silenced by the concentrated fire of the attack.
Tnese bomb-proofs contain the wells, kitchens, bakeries,
latrines, hospitals, telegraph stations, etc. The main maga-
zines are placed in the capital traverse or under the flanks ;
service magazines near the guns, and niches for ammunition
are sometimes made in the interior slope of the parapet.
The masonry arches are covered with earth of a thick-
ness varying from 3 to 16 feet, depending upon the fire to
which they are exposed.
For important points which must be held at all hazards
and where a great command and wide field of fire is wanted,
revolving turrets are proposed and are strongly advocated
by many engineers, foremost among whom is General
Erialmont.
When the gorges of the forts are exposed to the fire of
the works in their rear, they are in general casemated
masonry structures, which serve as barracks for the ^r-
risen, their outer walls being arranged for defence against
assault ; but when to hold a very important point to the last
extremity the works are thrown so far to the front as to
render it possible that they may be surrounded, the gorges
are made similar to the faces, but may have less cover for
their scarp walls against plunging fire.
Whenever practicable the oomb-proof s are arranged for
defence by infantry and machine gun fire, and serve as a
fiubstitute for the older form of keeps, which have been
generally abandoned.
168. The communication with the exterior is through
the gorge only, by a postern provided with two or more
barrier doors and a drawbridge, the ditch being crossed by
a permanent bridge or causeway, which is protected by a
<;asemated guard-house.
96 ELEMENTS OF PERMANENT FOBTIFIOATIOK.
The main communication in the interior is nsnally a
bomlvproof gallery from the gorge to the salient, nnder the
capitaJ traverse, which also covers a row of chambers on
each side of this corridor. This central communication is
sometimes replaced by an open passage similar to a chemin
de ronde at tne level of the parade and close to the parade
wall or rampart slope, giving direct access to the chambers
under the terre-pleins and traverses.
The necessary ramps, stairs, posterns, and lifts, are pro-
vided in either case.
169. When the work is small, and its importance justi-
fies the expense, the whole area inside the interior crest,
except the gun emplacements and the banquettes, may be
covered by chambers and passages in arched masonry and
earth.
170- These forts are surrounded by a glacis covering a
sentiners path extending around the fort. The outworks
are restricted to flanking caponnieres and redans or ravelins
covering the caponnieres and bridge at the gorge. When
wet ditches are used the masonry scarp and counterscarp
walls are replaced with earthen slopes.
171. If there is difficulty in providing places for the
artillery within the fort, permanent or provisional batteries
for 4 to 6 guns are constructed on one or both sides of the
fort, resting their flank upon the gorge or shoulder angle,
and having their interior crest at the height of the glacis.
They are suppKed with ammunition from the main work.
liV'hen they are intended to be worked independently, they
are provided with the necessary masks, shelters, magazines,
etc.
The forts are placed as before stated, from 4 to 8 miles
from the enceinte and 2 to 3 miles apart.
172. The intermediate works are calculated for a small
infantry garrison of from 60 to 100 men and 3 or 4 pieces
of artillery, usually field fi^uns.
They are generally haR redoubts or lunettes with short
flanks and straight or reentering gorges. They have a com-
mand of 16 to 20 feet, their parapets are from 16 to 23 feet
thick on the faces and about 13 on the gorge. Their scarp
walls are high enough to resist assault (13 feet minimum).
The arrangement of their gorges and communications is
similar to that of the larger forts. See Plate 16, Fig. 8.
laaawpok ov PEsiuirsirr TOftTifxcAXiG^* ff
CHAPTER Tit
INFIitnSNOE OF ZBRBGtTLARrnfiS OF 8ITB ON THB
FORMS AND COMBINATIONS OF THB BLBMBNTB OF
PBRMANBNT WORSa
173^ Although the same general principles are applica-
ble, and the same conditions mast be satisned in planning
a work, so that it shall have all the efficiency of which it is
capable, whether the site is unbroken and sensibly hori-
zontal, or presents a great variety of feature, within the
range of cannon of the proposed work ; still irregular sites,
where the surface is of a diversified character, give greater
scope than level ones for the science and skill of the en-
gineer, and call for all the resources of his art in adapting
his plans to the natural features of the site.
Tne principal conditions to be satisfied, and which are
the same in all cases, are :
1. That every point exterior to the defences, over which
the enemy must approach them, or from which he can
annoy them by his fire, shall be brought under the fire of
the defences.
2. That no point of the defences shall be left unguarded
by their own nre, or present any position where the enemy,
obtaining temporary shelter from fire, may gain time to re-
new an onset.
3. That the troops and materiel within the defences shall
be sheltered from the enemy's fire in any position he may
take exterior to them.
174. The problem presented for solution to the engineer
in irregular sites is frequently one of no ordinary complexity ;
demanding a minute and laborious study of the natural
features of the position in their relations to the defence ;
eonnected with a tentative process of which the object is so
to modify the plan, relief and details ordinarily adopted,
as to adapt them in the best manner to the given position.
.98 eijEMents of permanent FORTIFICATIOIT-.
Ko rules but of a very general character can be laid down
for the guidance of the engineer in such cases; among
which the following are the most essential, and, when, prac-
ticable, should be adhered to.
176. It has already been observed that, from the means
used in the attack by regular approaches, the more plung-
ing the fire of the work, the mure efficacious will it prove
in retarding the enemy's progress. The efficiency of this
fire will depend upon two causes :
1. The command of the work over the point to be at-
tained.
2. The direction of the ground with respect to the lines
by which it is swept.
176. As to the command of the work over the exterior
ground, it has already been shown that motives of economy
restrict it, in most cases, within very narrow limits, where,
to obtain it, artificial embankments have to be employed.
To augment, therefore, in the greatest degree this element
of the defence, advantage should be taken of the natural
features of the locality, by placing the principal lines, from
which the exterior ground can be seen, on the most com-
manding points of the site.
If, with this position given to the principal lines, the
ground swept falls or slopes towards them, the most favor-
able combination for an efficacious plunging fire will be
obtained ; for, with this direction of the ground, the enemy
will meet with far greater difficulty, in putting himself under
shelter by his works, than where the ground falls or slopes
from the line by which it is swept ; as the surface, in the
latter case, descending in the rear of the cover thrown up
by the enemy, will be screened to a greater extent than in
the former, where it rises in the rear of the cover.
When this, however, cannot be efiEected, the next best
thing to be done is, so to place the principal lines with
respect to the surface to be swept that it shall be seen by
a part of these lines, thus bringing to bear upon it a flank
fire from these parts.
177. The general rule, therefore, which the engineer is
to take as a guide, in order to satisfy the condition of bring-
ing the exterior ground under an efficacious fire from the
work, is :
1. To ptace the jprinclpal lines of his work on the most
•commanding points of the site^ and in such directions as
to hnng the exterior ground to he swept in a position slop-
ing towards these lines in such a manner that they cat.
ELEMENTS OF PERMANENT FORTIFICATION. 99
hring their entire fire to hear upon it, or else bring a por-
tion of it to sweep it in front.
This will generally be best effected by placing the salient
points of the work on the most commanding and salient
points of the site ; as, in this position of the salients, the
faces, which are usually the principal lines bearing on the
exterior ground, will occupy the salient and commanding
portions of the site, whilst the reenterings, being thrown on
the reentering and lower portions of the site, will be in the
best position for sweeping the ground immediately in ad-
vance of the faces bv a flank fire : and at the same time
these reenterings will be masked by the faces from the
enemy's view, and thus preserved from serious injury up to
the moment when their action may be rendered most effect-
ive; that is when the enemy, despite the fire from the
faces, has succeeded in planting himself upon points on
which this fire cannot longer be brought to bear.
To carry these precepts, which are equally applicable to
single works or to lines of detached works, into practice, a
wide margin is left to the engineer's judgment, in which he
will find it necessary in some cases to extend the lines of
his works beyond what a strict regard to economy might
prescribe, so as to include within his defences ground from
which he can best sweep what is exterior to it, or which
being occupied by the assailant, might make his own posi-
tion less tenable, in this way forcing him to extend out his
lines so as to embrace crests withiij them that overlook val-
leys beyond them ; and in some cases to throw his own lines
further back in order to avoid enfilading or plunging views
from points which are too distant to be brought within his
<lefences.
2. The condition of leaving no point of the defences
unguarded lyy the fire, will depend in a great degree for it^
fulfilment on the same rule as the preceding. TBut where
the irregularity of the site is sucn that all the exterior
ground cannot be swept by the fire of the works, additional
batteries, advanced works, or detached forts placed in
defensive relations with the main works must be employed.
These works should satisfy the usual condition, that the
more advanced must be taken before those in rear can be
successfully attacked.
3. The condition that the troops and materiel within the
defences shall be sheltered from the enemy^s fire from all
corrumanding points without, will depend upon the relative
positions of the principal lines and the exterior commanding
:« *
100 ELEMENTS OF PEHMANEITr FORTIFICATION.
points ; and as far, tberiefore, as it can be done, witfaout
sacrificing either of the precedmg and more important con-
ditions, the plan of the work should be so arranged that th&
principal lines shall present themselves in the most favor-
able direction to the exterior gronnd to avoid plunging, en-
filading or reverse views upon their terre-pleins from anj
point of it.
178. To effect these objects, when the work is in the
vicinity of commanding heights within cannon range, and the
crests of these heights, as seen from the work, present a
nearly horizontal outline, the principal lines of the work,,
fronting the heights, should receive a direction as nearly
parallel as practicable to that of tlie commanding crests.
When tne outline of the crests presents a nearly con-
tinuous line, but one which declines or slopes towards the
site of the work, the principal lines towards the height
should receive a direction converging towards the point
where the line of the crests, as seen, if prolonged, would
join the site, if this point or points beyond it and within
cannon range cannot oe occupied by the enemy.
The reasons for the positions assigned to the principal
lines in these cases respectively, may not, at a first glance,
be obvious; but by examining the relative positions of the
crests of the heights and of the principal lines, as here laid
down, it will wiuiout difficultv be seen that they can be
brought in the same plane, and the latter be so placed as to
give a nearly uniform command to the parapets of the
principal lines over the site; and that by keeping the terre-
pleins of these lines in planes parallel to. the one in which
the crests of the heights and those of the parapets are held,
and at suitable levels below it, the parapets will be made ta
cover the terre-pleins from the fi^e of the heights in the
feimplest manner.
179. Remarks. The foregoing general methods for
determining the direction of the principal lines fronting
commanding heights, so as to cover from direct fire, in the
easiest manner, by their parapets, the space to the rear oc-
cupied by the troops and materiel^ present, at the same time,
the simplest cases of the adaptation of the plan of a work
to the features of the locality, to subserve the object in
view. In most cases, all that can be done is to avoid giving
such directions to any of the principal lines as shall be fa-
vorable to enfilading or reverse views of the enemy ; whicli
may be effected by so placing them that their prolongations
|h01 fall on points where the enemy cannot estabhsh hi»
ELEMENTS OF PERMANENT FORTIFICATION. 101
works ; or on those which, if occupied by him, will aflEord
disadvantageous positions for his batteries either for enfilad-
ing or reverse tires.
As the attack derives its great advantage from its envel-
oping position, bj which enfilading views and a conce^-
trated nre can be brought to bear on the assailed point, so,
in the general disposition of his defences, the engineer
should endeavor to reduce these salient and assailable points
to the fewest number, and to accumulate upon them such
surplus strength that in spite of their natural weakness they
will cost the assailant a great deal of time and a large sacri-
£ce of means to get possession.
This consideration has led engineers to propose for the
general outline of their defensive polygon a triangle in
which the principal development of their work being a num-
ber of fronts on a right line, they can neither be enveloped
nor their principal lines be enfiladed by the assailant's
trenches, thus leaving only the three angular points as assail-
able, and which they propose to strengthen by an accumu*
lation of works upon them.
Were the engineer untrammelled in all cases by other
considerations, this method mi^ht do very well. But this
is far from being the case. All that he can, therefore, do in
planning his work is to keep this consideration in view,
throwing as many fronts as he can on the same right line ;
making the angles of his general polygon as open as possi-
ble, so as to force the assailant to a great development of hie
works, to gain a concentrated and enfilading fire on them ;
|)lacing these angles on points of difficult access to the as-
milant ; and by taking advanta^ of such natural obstacles
as water and rock, to give additional strength to these points.
The skill and judgment of the engineer are here his main
reliance in adapting his details to these general principles.
n.
DEFILEMENT OF PERMANENT W0KK8.
180. Remarks. The greater importance of so adapting
the plan and conmiand of permanent works to the features
of irregular sites as to satisfy the conditions of sweeping
thoroughly by their fire all approaches exterior to the de-
fences, and completely flanking the latter, seldom places it
in the power of the engineer to fulfil the condition of with-
102 ELEMKNTS OF PKRMANENT FORTIFICATION.
drawing the interior of the defences from either enfilading-
or reverse views by a modification of either the plan or the
command.
To mask, therefore, the terre-plein which would be ex-
posed to these fires, as well as iroiii such as would be at-
tained by a plunging fire in front, resort must be had to the
usual expedients of defilement; that is, giving to the terre-
pleins such position with respect to their parapets that the-
troops and materiel upon them will be screened from a
plunging fire in front by the parapets ; and, when the terre-
pleins are exposed to either enfilading or reverse views, by
so placing earthen traverses or other masks as to intercept
these views, and cover the troops, etc., from the enemy's
projectiles.
'The defilement of permanent works, like that of field
works, proposes the same end, and employs nearly the same
means/ xLy differ mainly in their practical details; the
latter being reduced to a simple practical operation on the
field, while the former, from the usually greater complex-
ity of the arrangements of permanent defences, requires the
aid of mathematical methods, and demands the best attain-
able results.
Owing to the regularity of the trajectory of modern rifles
and the resulting accuracy of fire even with an angle of fall
up to J or greater, it is generally impracticable to secure
cover from cannon fire for any considerable area by the de-
filement of open defences, fiowever, as the assailant must
in general see the eflEect of his fire, both to correct his aim,
and to learn whether his results justify the expenditure of
ammunition, the necessity for defilement from the view of
the attacking force, when it can be had at not too great cost^^
still exists. /
The protection of the larger areas from plunging, reverse
and enfilade fire must be secured by bomb-proofs; for
% limited areas it may be obtained by the free use of the
traverse and parados.
181. For the solution of all problems of the defilement
of permanent works, the engineer requires —
1. The limit exterior to tiie defences beyond which the
effect of the enemy's fire may be regarded as so uncertain
as to be neglected, and that beyond which he will be una-
ble to see the point struck and the effect produced by hi&
projectiles.
2. The presumed positions within this limit that the en-
».
-ft
ELEMENTS OF PERMANENT FORTIFICATION. 103
emy may take up to bring his artillery to bear upon the
works, or for observatories.
3. An accurate topographical map of all the ground within
the above limits, as given by its horizontal curves referred
to a plane of comparison.
4. The magistrals and interior crests of the works, as
'jither definitdy or proximately arranged, referred to the
same plane.
182. The 15c. m. {6'^) rifle, the largest considered available
for siege purposes, is effective for accurate breaching fire for
masonry up to 2000 yards, angle of fall about 3° ; for flank
fire against gun emplacements up to 3500 yards (angle of fall
6i°). Its extreme range is about 10,500 yards, or 6 miles.
The distance at which the point of striking and effect of
the shot can be determined by the use of field glasses and
portable telescopes is from 1 to 2 miles.
183. These limits, and the importance of protecting any
particular points within the work, will detiermine the charac-
ter of defilade to be adopted.
The surface of the site embraced within the exterior lim-
its and the line of defences may be divided into three zones,
one lying between the limits and position of the first paral-
lel 01 the attack ; the second between the positions of the
first and second parallels ; the third between the positions
of the second and third parallels.
184. At no stage of the attack will the assailant at-
tempt to raise his batteries above the natural surface of the
ground, in order to obtain command for his guns; the labor
and additional exposure of his guns to the fire of the de-
fence far more than counterbalancing the advantage gained
by any attainable increase in command. This will restrict
the vertical limit within which his fire may be delivered to
about 5 feet above the surface of the ground.
185. Observatories or lookouts will be placed at the
highest points which can be occupied with moderate secur-
tty ; but no great height can be given them above the gen-
eral line of the works without an amount of work incom-
mensurate with the small advantage gained in the first
cone or exposing them to the destructive fire of the defence
m the second and third.
These considerations will, in general, limit the height of
the observatories to 10 feet above the ground in the first
4nd second zones. In the third zone, the defilade will be
igainst close fire and a nearly straight trajectory. In this
cone the fire of infantry mounted on the parapets of the
104 BLBMENTS OF PERMAXEUTT FOBTIFIOATIOJT.
trenches may sometimes be used, and the work should be
defiled against it. The maximum height of this plane of
fire may also be taken at ten feet above the level of the site.
186. Taking, then, the extreme cannon range or the
adopted limit of distinct sight, the dangerous ground exte-
rior to line of the defences may be marked out on the top>
<^raphieal map of the site by drawing lines parallel to
those connecting the most advanced salients and at ikis
distance from them and then considering the reference© of
the horizontal carves of the ground within the zones thus
marked oflE to be increased 10 feet.
187. In the defilement of each part separately of the line
of defences, those portions alone of these zones should be
regarded as dangerous which are embraced within arcs, or
other lines drawn at the forgoing distances from the sal-
ients, or the faces of the part to be defiled.
It may also happen that, within the limits of dangerous
ground for one portion of the line of defences, there mav
be other portions which, from their positions, may mask
the portion to be defiled from all the dangerous points be-
yond them ; in which case the points thus shut off need not
be regarded, in effecting the operations of defilement.
If, for example (PI. 17, Fig 1), the limits of dangerous
ground for the demi-lune A being marked off, it is found
that the derai-lune b, masks the demi-lune a from all fire
that might come from the ground beyond b ; then this
portion of the zones of danger need not be regarded in de-
filing A.
To ascertain this it will only be necessary to pass a plane
through the interior crest of A tangent to the surface beyond
B, raised 10 feet, and see whether it lies below b at all
points. If so then will b serve as a mask for a.
188. All masonry should be covered by earthen masks
from the plunging fire of the heaviest guns within the
range at which this fire would prove destructive against it.
189. In the defilement of works of limited intenor capac-
ity, as, for example, the r^duit of the reentering pkce-of-
arms, the double caponniere and the like, which are^ more-
over, not habitually occupied by troopsy the eidtr^me limits
may be reduced.
190. Within the limits of the zoneo of danger, positions
may be found for front, for reverse, and for enfilading fire.
: Li the two faces, for example, of a work be prolonged to
intersect the extreme limit ot dangerous grpisQa, the sector
which they embrace may be termed the UmU qf direct pi
£!L£¥£NTS OF PSBM AVSITT PQETIFIOATIOSr. 105
frmt^fite / aiDce, from arary posJtiQo that can be taiken up
within this sector, a direct fire alone can be brought to bear
npiMi the two fiK^.
The two sectors which lie adjacent to this may be termed
iht limits of lateral J or revereejire, since they afford posi-
tions from which a reverse fire can be obtained against one
of the faees, and a front fire upon the other. It is also only
within these last limits that positions for enfilading the
terre-pleing of the faces can be obtained.
191. Remarks. The problems of defilement which pre-
sent themselves for solution may embriK;e one or more of
these caaes in any example ; depending upon the relative
positions of the interior crest of the work to be defiled, and
of the dangerous ground embraced within the foregoing
limits.
The terre-pleins may be screened from direct view by
their parapets, from reverse or enfilade view on one faee
alone, in some cases by the parapet of the other, in others
by traverses and parados.
A portion of the terre-pleins may be screened from plung-
ifig ^re by the parapet, parados or traverses, but for pro-
tecting considerable areas, bomb-proof casemates or shelters
arq required, as previously stated.
in.
FBOBLEIdB OF Di^FXL^MJSNT.
192. It does not come within the scope of this sum-
mary to examine the many cases of dofilement which may
trifle from irr^ularities m the site. Those alone will he
discussed which are of most ordinary occurrence, and wbiph
feqaii^ for their solution the usual geometrical constructions
involved in planes and other surfaces tangent and secant to
^ surface defined by the projection of its horizontal curves.
The cases which will here find their a.pplication may be
arranged under two heads:
1. The plan aad command of a. work being definitely de-
cided npon, to ascertain the exact portions of the zones of
daijger, from which anv description of fire can be biwight
to bear upon its terre-pleins, and to defile them from it.
8. The plan of a work beinff definitely fixed, but its com-
rnm^d only approximately within eertain limits, to aeeertain
^Im easiest niethod of defiling the terre-pteins of the work*
106 BLBMBNTS OP PBRMANBNT FOBTIFICATION.
by varying the commaTid, or position of the interior crest^
within the assigned limits.
193. (Prob. 1, PI. 17, Fig. 2.) The commcmd or posi-
tion of the interior crest of the faces of a work being ^acedy
to ascertain the danaerous points on the exterior^ and ta
defile its terre-pUin from these points.
Let a b, a e, be the projections of the given crest ; and
the curves (26.0), (29.0), etc., those of the natnral surface.
Prolong outwards to c and d, the faces ; construct the scales
of declivity of the two lines, a e, a d ; and, from them, the
scale of declivitv, e f, of their plane.
From the salient, a, supposing an arc to be described
with a radius of 3500 yaras, the dangerous ground will be
included between it andl the two faces of the work.
Now, if the plane of the interior crests, of which e f is
the scale of declivity, be indefinitely extended, and its inter-
section with the surface parallel to the natural surface and
10 feet above it be found, it is evident that the portion of
this raised surface which lies below the plane may be dis-
regarded, as the interior of the work is covered from it by
the parapet. But from every point of the surface above
the plane the interior is more or less exposed to view, de-
pending upon the height of the point above the plane, its
distance from the work, and the height of the interior crest
above the terre-plein and parade.
Having drawn the horizontals of the plane, e f, and found
their intersections with the corresponding horizontals of the
raised surface (which last will be given by adding 10 feet to
the references of the curves of the ground), of which x y z
is the projection, that portion of the surface which lies
above tnis curve will alone see the interior of the work, and
will be the only portion for which defilement will be neces-
sarv.
ffow, as this intersection falls entirely within the angle
d a e, of the faces prolonged, or within the limits of front
fire, it is evident that the terre-pleins will require to be de-
filed only from direct fire.
To e^ect this, let a plane be passed through the face»
b a d, of the work, and tangent to the raised surface above
X y z. This plane will pass above all the dangerous ground,,
except at its point of contact with it ; and, being extended
back from the face within the work, it is clear, if the terre-
plein of this face be so taken with respect to this plane that
no point of it shall be less than 8 feet below the plane, that
then every point of the .terre-plein will be screened fron^
ELEMENTS OF PERMANENT FORTIFICATION. 107
View by the parapet of the face a b. Now, if the same
series of operations be gone through with for the face,
c a e, then will its terre-plein be defiled in like manner ; and
thus the defilement of the whole work be completed for
this case.
The tangent planes which satisfy the above conditions are
termed Poanes of Direct DejUementf and they may be de-
fined as the planes which^ passed through the interior crest
of a para/pet^ leave at least 10 feet heZow them^ all the
dangerous ground of front f/re^ amd pass at least 8 ftet
above every point of the terre-plein hehind the parapet
The terre-pleins are usually parallel to their respective
planes of direct defilement and 8 feet below them. But
when the declivity of the plane of defilement exceeds -^y.
then the terre-plein, if it is to receive cannon mounted ou
travelling carriages, must be kept within this limit.
In Fig. 2, the references are given in feet. The tangent
plane through b a d is determined in the usual manner, by
finding the horizontal (in this case 45.0), among all those
drawn to the curves of the raised surface, which makes the
minimum angle with b d. The line h i, perpendicular to this
horizontal, is the scale of declivity of this plane ; and the
point, p, that of contact. The line k 1, is, in like manner,
the scale of declivity of the other plane, and o its point of
contact.
It might happen, from the steepness of the terre-pleins,
that the reentering or gutter formed at their intersection
would be inconvenient, and it would therefore be desirable
to have this position raised, when it can be done without
exposure to a plunging fire.
This, in most cases, may be effected in this way : It will
be seen, from an inspection of Fig. 2, that the points o and
p' are the only ones from which the enemy's fire passes ex-
actly at 8 feet above all the points of the respective terre-
pleins determined by the tangent planes ; and that if, from
these points, lines of fire, oar and p a s, be drawn, every
other line of fire through a, from the ground in the angle,
p a o, will pass more than 8 feet above the portion of the
terre-pleins embraced in the angle, s a r, since the ground
"^ within the exterior angle lies below the tangent planes.
If, then, a be taken as the vertex of a cone, the elements
of which are tangent to the raised surface within the angle,
p a o, and if these elements be prolonged within the work,
their prolongation will form a cone of lines of fire, which
will pass more than 8 feet above the terre-pleins. If these
108 ELEMENTS OF PERMAKENT FOBTIFICATION.
last, therefore, be connected by a sarfaee parallel to thie
cone, and 8 feet below it, this surface may be taken as the
portion of the terr^-plein which, connecting the two plane
portions, will renaedy the inconvenience pointed ont.
194. (Prob. 2, Fig. 3.) Tlie data hemg the aame as m
the preceding caae^ and the work being eospoaed to both
direct and reverse views^ to cover its interior from these
views.
Suppose the plane of the interior crest of the faces ex-
tended within the limits, and its intersection with the
dangerous ground determined as in the preceding case ; and
let X y z, m n o, and p q r, be the curves of this intersection.
The face a b will be exposed to direct fire alone from the
ground above the two curves x y z and m n o ; and to re-
verse fire from that above the curve p q r. In like manner,
the face a c will be exposed to direct fire from x y z and
par, and to reverse fire from m n o.
The defilement of each face from the direct fire will be
effected preqiselj in the same way as in the preceding Prob.
The lines h i and k 1 are the scales of declivity of the
planes of direct defilement of the faces respectively.
For the reverse defilement, a plane is passed through a b,
tangent to the surface above p q r ; and one through a c,
tan^nt to the surface above m n o, and their line of inter-
section a 2l found. The line u v is the scale of declivity of
one of these planes, termed a Plane ofHeverse DeJUement,
and s t that of the other.
Now, if a traverse is so placed that its crest shall occupy
the position of the line a a', it will cover all between it and
the two faces, as high as the interior crests, from the reverse
fire on each side, lout as it is desirable to have the troops,
when on the banquettes, screened from this fire, the crest of
the traverse should be raised from 18 inches to 2 feet above
the line a a' to effect this.
The traverse should extend so far towards the gorgis of
the work that the entire line of each face shall be covered
by it. To determine its length with this condition, lines
are drawn from the extreme points b and c of the faces,
tangent to the curves ni n o and p q r, and their points o|
intersection with a a' maxked ; the one that falls fartbe^
from tlie salient will evidently give the required length.
If the line a a' should fall so near either of the faces tiiait
the traverse, if placed along it, would incommode the ser-
vice of that part of the work, it will be the best to plaoe its
erest in the vertieal plane a a"^ of the capital of the worip
ELEMENTS OF PERMAKBITr tOMlBlCATIOir. 1Q9
ll^Ben 80 placed, the intersection of this vertical phne with
each of the plaiies of reverse defilement mnst be tonnd, and
the crest of the traverse be taken 18 inches above the one
that lies highest.
l^fr. The position of the crest of the traverse, as deter-
mined by eitner of the preceding methods, will be in a
vertical plane passing through the salient, a, of the work.
From the thickness and slopes which traverses nsnally
t-eceive, they would ordinarily, if placed in this position^
take up all the interior space within the salient, and leave
ho room there for dispositions either for artillery or mus-
ketry. To prevent this, a break is made in the direction
of the crest, at some point on the vertical plane through
the salient, from which it is directed on a point of either of
the faces, so far from the salient that sufficient room will
be left for the object in view. In (Fig. 4), which illustrates
this arrangement, the traverse is withdrawn far enough
from the salient to leave room for a barbette battery for
several guns.
The face upon which the traverse is directed, will be de-
termined by tne condition of covering both faces in the most
effective manner, by the position taken for the traverse.
196. The cross section of traverses for permanent works
is similar to those used in field works. The top of the trav-
erse receives a slight slope each way from the crest to the
sides. The thickness at top is sufficient to render it shot-
proof. The sides take the natural slope from the top, either
to the lowest level at which they may be struck or to the
terre-plein. If to gain interior space these slopes are
terminated at the higher level, then the portions of tne trav-
erse below these planes are made more steep, and the earth
supported by retaining walls. The top of the traverse,
wnere it joins the parapet, being higher than the superior
slope, is run out above this slope, upon which the side
slopes fall ; its extremity terminates in the plane of the ex-
tenor slope, extended above the exterior crest.
197. when, from any circumstance, a single traverse
cannot be used for reverse defilement, resort must be had
to several, which should be so combined that no line of fire
can penetrate between their extremities to attain any point
which they should cover.
Examples of this constrnction are found in several plates,
and will suggest the manner of making others. The fol-
lowing case will serve as a farther illustration :
Where a demi-Iune is arranged with a r^duit, a traveree
110 ELEMENTS OP PERMANENT FORTIFICATION.
placed in its salient cannot be extended further back than
the counterscarp of the reduit ; and an open space, there-
fore, will be left at the ditch, through which a reverse fire
would attain that portion of either face which is not covered
either by the traverse in the salient, or by the parapet of
the reduit.
To cover the part thus exposed, it will be necessary to
place one or more traverses, which, in combination with
the one in the salient, and the parapet of the redoubt, shall
subserve this end.
To simplify the case, let the face a c, PI. 17, Fig. 5, be
the one exposed, and let the point x be one the tire of
which is most dangerous. Having, in the first place ar-
ranged the traverse, t, as in the last example, and drawn
the two lines of fire x b and x d from th6 point x, through
the extremity of the traverse, and the top of the parapet of
the redoubt at the salient, the length, b d, of the lace inter-
cepted between these I'nes will be the part to be covered.
If a second traverse, t', be placed across the terre-plein of
the other face of the demi-lune, and in a position such that
one of its ends shall rest on x b, and the other on x d, it
will evidently cover the portion b d.
198. In selecting the positions of several combined trav-
erses, attention must be given to avoid those where, if one
be placed, the assailant would find shelter behind it from
the fire from the rear. In the example just taken, the slope
of t, towards the salient, should be swept by the fire from
the rear, through the reduit ditch ; the like slope of t'
should be swept by a portion of the reduit face near its
salient ; and neither so fall as to have the space behind it
masked from fire by the one to its rear.
199. Remarks. Traverses usually present not only the
easiest solution of all problems of reverse and enfilading
defilement, but, affording the means of rendering the com-
mand independent of fire from without, they enable the
engineer to regulate this element solely with a view to the
effect which he desires to attain by his own fire.
From the space required for their erection, traverses may,
as in the cases of narrow terre-pleins, like those of the
covered ways, and of the demi-lune with a redoubt, be in-
convenient, both from embarrassing the communications,
and from taking up ground that may be wanted for bat-
teries.
200. (Prob. 3.) Thejplcm of a hastion deing dejmitivdy
Jixed^ cmd one point of its com/mand ajpjproximately^ to de-
ELEMENTS OF PERMANENT FORTIFICATION. Ill
jile the work in the most advcmtageous mcmner^ hy shifting
the position of its interior crest within certain limits.
Let Fi^. 6 be the plan of the work, and a the salient, the
command of which can be varied within certain limits with-
out impairing any of the other conditions ; and let the dan-
gerous ground be embraced within the arc m n, at 3500
yards from a, and the lines a u and a v supposed drawn
from a, through covering masses on the right and left of the
work.
The front limits of defilement in this case are embraced
within the sector man; and the lateral limits within the
other two man and n a v. Now, the most favorable case
of defilement here will be that where a plane, containing a,
taken within its extreme positions, shall pass above all the
exterior ground, and give such a command to the interior
crest throughout, when held in it, as shall satisfy the other
conditions of defence. To ascertain the existence of such a
plane, let a be taken as the vertex of a cone which envelops
all the dangerous ground ; any plane tangent to this cone
will satisfy the condition of defilement, and it will, there-
tore, only be necessary to find whether any one of these
planes of defilement will satisfy the other, of giving the
points b c d, and e, a suitable command. If no such plane
can be obtained, the next most favorable case will be to find
•one that shall satisfy all the requisite conditions of com-
mand, and intersect the ground only within the front limits.
In this case it is clear, from the position of this plane, if the
interior crests are held in it, that the interior of the work
will be exposed only to the direct tire from that portion of
the ground which lies above the plane.
Let X y z be the curve of intersection of the plane with
the ground, found in the usual way. Through the faces a b
and a d, let planes of direct defilement be passed ; the terre-
plein of the faces being held parallel to them will be covered
by their respective parapets from all plunging fire. But,
in order that the planes of defilement of the faces shall also
defile the flanks, it is necessary that each flank be placed in
the plane of defilement of the adjacent face, and its terre-
plein in that of the terre-plein of the face. Now, in giving
the interior crests of the flanks these new positions, they
will lie below the plane that contains the curve, x y z, . >d
in which the interior crests of the faces lie. This being 1" s
case, it may happen that the parapet of one of the flanks
will not cover the opposite face from reverse fire, coming
from the lateral limits opposite the flank. In this con-
112 SLEMfiHTS OF PERMANBKT FORTIPICATIOX.
»
ImgBntsj, it will be BeeesBorj, in order to corer the faee, ta
place the flank in tlie plane of the cnrve, x y z, as this jplane
defiles from the lateral limits ; bnt, in doing this, the nank^
' d e, f(»* example, will be exposed, in its tarn, to the ground
above x y z ; and to cover it, the onl^ remedy is to erect a
travenie, at some snitabte point, which shall intercept all
this dangerons fire. The least inconvenient no^tion for the
traverse will nsnally be at the shoulder angle. From this
point it must extend so far back as to intercept all fire from
above x y z, both on the terre-nleins of the fiank and cur-
tain, where they unite, and be nigh enough to screen the
troops on the banquette.
It the defilement cannot be effected by either of these
processes^ there remains no othi^ means than, having finit
definitely fixed the command, to divide the bastion by a
traverse, either along its capital, or some other convenient
direction, and, having given it a suitable height, to cover
each portion from direct fire by the usual method.
201- The for^i;oing problems embrace in their solution
all of the more ordinary cases of defilement, and suggest the
route to be followed in treating others.
In all cases of the defilement of combined works, like the
enceinte and its outworks, etc., it must be borne in mind
that the advanced works, which from their position, must
first fall into the assailant's power, become thus a portion of
the dangerous ground for the works more retired, and
which must also be held after the fall of the others. The
retired works, under such circumstances, must be defiled
from the advanced ; their planes of defilement being made
to pass from 3 feet to 4.6 feet above the portion of the ad-
^Bced work on which it is presumed the assailant may
make a lodgment, and, which, from its position, may be re-
tarded as the most dangerous to the retired work, it being
assumed that in the close attack the artillery fire will be de-
livered at a height above the ground not greater than this.
202. Where a work has considerable command, and is
open at the fforge like the cavalier retrenchments, for ex-
ample, and toe works in its rear do not mask its interior
from reverse fire, it may be necessary to place a traverse,
termed 9^pwrados^ across its terre-plein a^ the gorge, giving
it su£Scient height to subserve the end in view.
A parados or traverse immediately in rear of a parapet
exposed to front fire is open to objection, since shells
yasang over the parapet penetrate the traverse and by Idbeir
ELEHEKTS OF PEBHAKEITF FOBTIFIGATIOlSr. 113
explosion throw out splinters and portions of the traverse
toward the parapet.
On the otner hand, they intercept splinters coming f rom
shells exploding in their rear, and when properly construc-
ted, of soft earth, retain a very large portion of the splinters
of shells exploding after striking them.
The following conclusions were drawn from the results
of an exhaustive series of experiments recently carried on
in Italy (" Fortifications of To-day," Washington, Govern*
ment Printing Office, 1883) :
" 1. In temporary batteries, and also in permanent ones
which can only be attacked by field or siege artillery, para-
dos, even at short distances, are not only free from danger,
but also in most cases advantageous.
" 2. When in works subjected to fire of greater calibres,
parados have to be used, well sifted earth should be chosen
m preference to sand in their construction. Their distance
from the battery, measured from the foot of the interior
slope of the parados to the end of the gun platform should
be not less than twenty metres (66 ft.) if the work is ex-
posed to the fire of siege artillery of calibres not greater
than 15 cm. (6^), nor less than thirty metres (99 ft.) if the
work is exposed to more powerful artillery. These limits
may be somewhat reduced for batteries high above the posi-
tion of the attacking artillery.
" 3. As the inconveniences resulting from parados placed
at distances less than those indicated may in many cases be
less than that proceeding from the fire of musketry or of
artillery placed in commanding positions in rear of the bat-
tery, so in especial cases in wmch fortifications have to be
constructed, the importance of the two dangers will have to
be compared in oroer to judge whether it is better to place
the parsidos at less distance or to expose the battery to re-
verse fire."
203. Qeneral Remarks. The methods of defilement
here laid down are those now followed by en^neers. They
unite mathematical accuracv in results with great simpli-
city of detail ; and render the defilement altogether secon-
dary to the other conditions of defence, upon which the
plan and command are made essentially to depend.
Before they were adopted, the results of the method then
followed were, in most respects, like those obtained in the
practical operations for defiling field works. A line was
taken, the position of which was determined by a series of
trials, having for their object to obtain the most satisfactory
8
114 ILBVBKTB 09 Pfi&lfAKENT IfOmtSlCATtO^.
lesQlts both as to the economy of the requisite embankments
and the best disposition of command of the varions parts at,
or in the rear oi, the fforee of the Work to be defiled ; this
position coinciding witn tne natural snrface, or being above
or beneath it as the case reanired. Throagh this line a
plane was passed tangent to the dangerous ground. This
plane^ termed, as in field defilement, a Ra/mpant Plane^
was taken as the artificial site of the work, in reference to
which the relative command of all the parts was arranged
as upon a horizontal site. Or, in other words, the result
was nearly the same as if the works had been arranged on a
horizontal site, and then the whole combination turned
around some fixed line of this site, until it was brought into
the position of the required rampant plane. The defects of
this method are evident at a glance. It preserves the re-
lations of defence of the various works the same as in a
horizontal site ; but it, to a great extent, leaves out of con-
sideration the bearing of the command on the exterior
ground, and, in many cases, may lead to excessive excava-
tions and embankments which the methods now followed
enable the engineer, for the most part, to avoid.
In the preceding discussion fixed horizontal limits of de-
filade have been avoided, as they must be determined by
considerations of relative cost and value to the defence.
The vertical limit is considered the maximum which is
practicable or generally desirable. It is fixed with a view
to preventing tne commander of a battery seeing the effect
of his own shot and correcting his aim by it. It is, of
course, impracticable to prevent the effect being seen from
other points ; but when many guns are engaged this is of
little value to the attack, since it is almost impossible to
know to which gun any single shot belongs.
To recapitulate: against a plunging fire the protection
given by the parapet depends only upon its height and
flie angle of fall of the projectile.
Defilade against this nre can be determined by passing a
plane with the proper inclination through the interior crest
without considering in any way the point from which the
shot comes.
Against close direct fire or for concealment from view,
the principles and problems given above illustrate the meth-
ods which may be employed.
To what extent these methods shall be used, if at all, will
be determined by the circumstances surrounding each par-
ticnlar case.
amnirm of vtRUAscam toBxmcMTtos. 115
CHAPTEE Vin.
A00ESS0R7 MESANS OF DBFBNOB.
I.
204. "Water may be made a very important accessory
means of defence in many localities — as in a flat, marshy
country where the level of the natural surface lies but at
a, slight elevation above the water-level ; or, as in the case
of an undulating surface, where small streams, running
through valleys, can be dammed back, so as to produce an
inundation oi some extent.
206. In the former case, the defensive works can be
'easily girdled by a zone of marshy ground, upon which it
will give an assailant great trouble to construct his trenches
and other siege-works, while the work itself can be secured
from attempts at surprise, by keeping its ditches filled with
water to the depth ot six feet at least. In such a locality —
moreover, if in a climate where the winters are mild — revetted
ficarps and counterscarps, the chief use of which is to t^re-
vent an attempt at open assault, may be replaced by eartnen
ones, a strong stockade being formed along a wide berm,
answering as a corridor, to give greater security on the more
exposed fronts of the work.
206. In the latter case, portions of the ground, in the
immediate vicinitv of the works, may be covered by a sheet
of water, of suflScient depth to prevent their being used by
the assailant in his approaches; and within the inundation
thus artificially produced detached works may be erected,
which, having flank and reverse views over other lines of
approach of the assailant, may force him to make his ap-
proach upon other points which have been strongly fortified
to meet this condition of things.
To form these artificial inundations the locality must lend
itself to the construction of dams, in such a position that
they cannot be reached by the assailant's missiles, and will
be secure from any other means he may take to destroy
116 91iEXB;NT8 of PWMAKSNT F097IFICATIQX.
them. This euppoees, then, that the stream should either
run through the works, so that the dam could be erected
within them, or so near to them that, in combination with
some advanced work, the dam may be made secure.
In a locality having these features, the inundation would,
as a general rule, have to be formed on the up-stream side of
the work, since, if made below it, the dam would have to be
placed further from the work, and the inundation itself
might spread up too far within. Besides these objections
to this position, an assailant would evidently have greater
facilities for tapping the inundation and running the water
ofi than when it occupies the up-stream position.
The position and extent of the dams, and the other neces-
sary constructions connected with them, as sluices, waste
weirs, etc., will depend entirely upon the local features of
the site, and will form a particular study in each case for the
engineer.
207. Besides these uses of water as a passive obstruction^
arrangements may be made, when the locality is favorable
to it, for producing a powerful current to sweep away the
assailant's works in the ditches by letting loose a large body
of water, which has been dammed back for the purpose,
with a rush into the ditches. This, in like manner, will re-
quire the same constructions as in the preceding case, and
flash gates which can be suddenly turned about a norizontaL
or a vertical axis, so as to give an outlet to the water in con*
siderable volume and with great velocity. These gates have
to be placed in some very secure point of the ditches, in-
accessible to the assailant and covered from his missiles, and,
if effectively used, may prove a source of great annoyance
to him by frequently frustrating his attempts to make a
passage of the ditch.
n.
208. Solid hard rock, or even thin layers of soft rock
alternating with lavers of soil, as was the case at Sebastopol,
are great obstructions to an assailant's siege works, as the
rock has, in many cases, to be blasted out to gain partial
cover, and a large amount of earth with trench materials,
has to be brought forward at great risk of life to form the
parapets.
In constructing a work, nothing should be omitted
which, if placed on the line of the assailant's approaches,,
will delay his operations and force him to greater enortsand
ELEMEiarXS OF PEBMAKENT FOBTIFIGATIOK. 117
exposure. To this end, where fragments of rock can be
readily had in sufficient quantities, it should be used in form-
ing the embankments oi the glacis, and also be thrown in
upon other points, over which important lines of trenches
must necessarily be run.
Besides these accessory means of delaying the progress of
the besieger's works, a site of solid rock offers the further
advantage of giving natural scarps and counterscarps, where
the ditches are excavated out of the rock, of far greater re-
4Bistance to the assailant's means of destruction than any
masonry, however solidly and carefully constructed, can
offer; besides forcing the assailant to construct galleries
through the rock to atlSin the level of the bottom of the ditch
where hispassage of it is to be constructed.
209. With a similar purpose, the stumps of large trees
may be left in like positions, and trees may be planted when
the work is constructed with the object of cutting them
down, using their timber, and leaving their stumps when the
work is threatened with a siege.
210. Obstacles as described in field fortifications may
also be used in the defence of a breach or as an aid to a weak
ficarp wall, for which they are even recommended by some
engineers as a substitute.
m.
211. Mines, when properly arranged and well played,
are so important a defensive means fliat they should con-
stitute a part of the permanent dispositions of defence of
«very wort where the character of tne soil will admit of it,
at least on those points which are otherwise weakest, and
therefore most liable to be assailed.
As the general arrangement of a combination of galleries
and mine chambers, as well as the details for their construc-
tion, is given in Military Mining, nothing further is called
ior here than to state that the principal galleries of the
•combination should be constructed with the work, and of
durable materials, leaving the other parts to be done when
the exigency calling for them may happen.
118 mJOlE^nS of PSBKAKEImT F0BIi;iCATI02ir.
CHAPTEE IX.
8EA.OOA8T DEFBNOS.
BATTERIES ON LAND.
212. The different character of the attacks to which sea-
eoast and interior fortifications are subject, leads to material
differences in their construction.
The guns attacking sea-coast works being mounted on
ships which by their constant movements prevent deliberate
ana accurate aim, it is impossible to break down the de-
fensive works by placing shot after shot upon a limited
area, as is done by ^reaching batteries on lana.
On the other hand the ships, being able to carry the
heaviest guns, can, by uniting m large fleets and concentrat-
ing their fire upon one or two works, generally have the
advantage in number and weight of guns ; while their tops,
presenting poor targets to the defence, are particularly
favorable for the use of machine guns against the shore lot-
teries.
213. Stone casemates, which as previously stated, would,
when built, stand single shots from the heaviest guns then
in use, are now easily penetrated and the fragments of
masonry add to the destruction produced by the projectile.
Their use is given up by all nations.
Sea-coast guns are now protected either by earth, iron, or
steel.
214. Earthen Batteries. The thickness of a sand
Earapet equal to once and a half the penetration of the
eaviest shot is about 70 feet (see Table of Penetrations,
Appendix I). This thickness is excessive, and would uot be
often used. An equal resistance with a thinner parapet
may be obtained by using concrete or large blocks of
granite set in cement, the resistance of the first being
approximately twice and of the second three times that or
sand.
Eli^lKENTS OF PEBHAITENT FOUTlVlCAJLOJf. 119
216. As before remarked, the penetration of elongated
projectiles in parapets is less than in experimental butts^
and the result of the bombardment of Alexandria, in 1882,
in which 80-ton guDs were used, led to the conclusion that
^' Ko English gun afloat could send a projectile through or
seriously damage a good earthen parapet 30 feet in thick-
ness, at ordinary practicable ranges." *
216. The practice in Germany is to make earthen para-
pets of sea^coast works from 33 to 40 feet thick.
The tendency of American engineers is to use thicker
parapets.
217. No matter what the thickness of parapet, a plung-
ing shot striking near the interior crest generally passes
through and cuts a furrow, throwing out the earth and
diminishing the height of the parapet.
This, combined with the plunging fire of machine guns
from the ship's tops, makes it necessary to give the greatest
available height above the terre-plein to the interior crest in
open batteries.
This height of interior crest is of little value if the gun,
at all times, and its detachment, while loading, are exposed
to the fire of the ship's cannon and machine guns, since even
the smaller cannon can by a well directed shot dismount or
disable the heaviest gun, or the machine guns sweep away
its detachment.
218. Several forms of disappearing sun carriages have
been devised which allow the gun to be lowered benind the
parapet to load and to be raised above it to fire. Figs. 2, 3,
and 4, Plate 7, illustrate three of these. The drawings
show their general features.
219. The Moncrieff works well for the smaller guns but
is not applicable to the larger calibres.
220. The Hydraulic or H^dro-pneumatic requires the
use of steam power for its rapid working, but it may be ap-
plied to the heaviest guns if its parts are properly propor-
tioned.
221. King's carriage has stood the test of exhaustive ex-
periments with the 25-ton gun, may be worked by hand-
power with a 50-ton, and if properly constructed would
work with the 100-ton gun. Major King proposes with
very heavy guns the use of hydraulic pressure instead of
hand-power for manoeuvring the carriage.
*NoTB. — Report of British Naval and Military Operations in Egypt,
1882, by Lieutenant-Commander G. F. Goodricli, U. S. Navy.
120 ELEMENTS OF PEBMANENT PORTIFIOATION".
222. Open batteries exposed to slant and enfilade fire
mnst be protected by high traverses with bonnets. One, or
at most two, guns may be mounted between consecntive
traverses.
The thickness and height of traverses are determined by
the direction of the fire to which they may be exposed.
High traverses are open to the objection that they show
the position of the guns to the enemy at great distances.
223. When the battery is only subject to front fire, the
interior crest and the tops of the splinter-proof traverses
should be held in the same plane.
The guns should be painted of the same color as the para
pet or background and provided with shields to protect the
gunners from small projectiles.
224. Powder magazines and shell rooms are made under
the traverses communicating by a lift with the loading
passage in the traverse at the level of the terre-plein ana
generally close to the interior slope, the gun being traversed
so that it is presented at this passage for loading. Plate 7,
Fig. 1.
A bomb-proof room for the relief detachment is also built
in the traverse.
When hydraulic power is used, bomb-proof shelters for
the steam boilers ana pumps are built in a place secure from
hostile fire.
225. When placed upon a commanding plateau, of ample
area, the battery may consist of a series of gun-pits sunk in
the earth and fitted up as previously described.
226. This construction is particularly well suited for
mortar batteries, which may be set back from the crest of
the height, the pits being made to contain from one to four
mortars each; the traverses between the pits serving for
magazines, shell-rooms, cover for the men, and firing points
for the groups of mortars, which may be placed very close
together and fired from the shelter provided.
Plate 2 is a batterv for 12 mortars designed by Gen. H.
1. Abbot, Corps of Engineers, described in No. XI. Printed
Papers Essayons Club, March 3, 1869.
227- The increased accuracy of fire and weight of pro-
jectile of the rifled mortars has given them much greater
value for use against ships, and will cause them to oe ex-
tensively used in the detence of channels and anchorages.
Their fire attacks a ship upon its flat deck, which, is its most
Vulnerable part above water. They can be silenced neither
by the ship s cannons, machine guns, nor mortars on float-
ELEMENTS OF PERMANENT FOBTIFICATION. 121
ing stmctures. Mortar batteries are not expensive either
in construction or armament.
228. If the site of a battery be very high, 100 feet or
more above the water, it is generally considered that guns
mounted on simple barbette or embrasure carriages in open
batteries will be able to hold their own against ships, owing
to the diflSculty which the latter experience in working their
heavy guns at high elevations, and the loss of plunge m the
:fire of the machine guns. In this case, however, as in the
low batteries, the guns should be provided with shields
against small projectiles and the cannoniers should be
-covered with a sufficient height o f p arapet.
229. The Use of Armor. Where the sites are con-
tracted, earthen batteries cannot be built, and when without
xjonsiderable command open batteries are rendered unten-
:able by the small arms and machine guns of the ships. For
these sites covered defences of iron or steel are alone avail-
4ible.
These are either casemates or turrets ; they are made of
i?erought-iron, compound-plates, steel or chilled cast-iron.
When a limited field of fire only is desired, casemates
have the advantage of cheapness, but usually require a some-
what larger embrasure, which as well as the muzzle of the
^n is constantly exposed to hostile fire.
Turrets give an all-round fire with the sipallest possible
embrasure and almost complete protection so long as the
^rmor is not pierced, and allow the muzzles of the guns to
be turned to the rear while loading.
They are more expensive than casemates in themselves,
in their substructure and in the machinery for their working.
230. The great expense of iron and steel constructions
will always limit their application to the protection of guns
of the highest power, which cover important points. The
smaller guns will generally be placed in open batteries.
These smaller guns being much cheaper in themselves, their
mounting and emplacements, as well as much more rapid in
their fire, which is nearly as effective as that of the large
guns against unarmored ships and the unprotected parts of
iron-clads, they should be provided in as large numbers as
practicable.
n.
231. Floating Batteries. In some harbors of large
tffea or with marshy banks, emplacements for guns com-
inanding the channels cannot be obtained on shore.
122 BLPMENTS OF PEBMANBJJT FOftTIFIOATIOIT,
For these cases the defence will sometimes require float*
ing armored batteries of small speed, light draught, and
great thickness of armor, which may be placed in differ-
ent points of the harbor passing over shoals to avoid being
rammed, or to pass from one channel to another when de-
sired. They will carry the heaviest guns with the best pos-
sible protection, and not being designed to go to sea, can be
made stronger in guns and armor than the attacking ships*
Their first cost and the constant expense of keeping them,
in serviceable condition prohibits their use except in harbors^
which can be defended in no other way.
m.
232. Obstacles, Submarine Mines and Torpedoes*
The defence of harbors is not possible without the use of a
sufficient number of guns and mortars ; but where the in-
ducement is great enough to justify it, or the inner harbor
is not well protected, vessels can, and, under favoring circum-
stances will, run by the outer batteries, however well con-
structed and armed, unless obstacles, passive or active, are^
placed in the channels which will hold them under the fire
of the guns until they are disabled by this fire or by the
action of the obstacles themselves.
A perfect defence requires, beside guns and mortars^
passive obstacles and submarine mines or torpedoes.
233. Obstacles. The following^ general conditions^
should be fulfilled by a system of passive obstacles, viz. :
1st. They should be in readiness for use at short notice,
and of such simple construction as to be readily placed in
position by river and harbor tug-boats.
2d. They should be capable of withstanding the effects of
currents and storms, and the action of marine insects md
growths for a considerable time.
3d. They should either be so strong and rigid as to break
through the bottoms of vessels striking them, or, if of n
yielding character, their resistance should gradually increase
until it stops a vessel coming against them.
4th. They should be so plaoSi as to be thoroughly swept
by the fire of both the large and small guns of the defencej,
and of a construction which will not be seriously injured by
this or the hostile fire.
834. The passive obstacles generally used, and which
satisfy the above conditions to a greater or less degree, de-
pending upon their construction, the character of the bot-
ELEMENTS OF PEBHAKEKX FORTIFICAXIOK. 121^
torn, the currents, the temperature of the water and their
expense, are sunken vesseb and cribs, piles driven anct
ri^dly braced in a vertical or inclinea position; pile^^
driven nearly to the bottom with floating and pointed logs
attached to them by chains, making artificial "sawyers;'^
booms and rafts stretched across the channel ; floating neta
of chains, wire or other rope supported by buoys and geur
erally carrying ropes with loose ends to become entangled in
the wheels of attacking vessels ; and in shallow water ehe^
vaux defrise or any other extemporized devices.
Of these the fixed obstructions can be used only in chan-
nels intended to be closed somewhat permanently ; the float-
ing ones being used in those which it may be necessary ta
open for the passage of friendly vessels.
236. Submaxine Mines and Torpedoes. Subma>
rine mines and torpedoes were first tried in the war of the
Eevolution, but hardly passed the experimental stage. They
were again used in the Crimean war to a very limited ex-
tent.
Their first successful application on a comparatively large
scale was in the war of Secession, 1861-5.
236. A system of submarine mines to be efficient should
satisfy the following conditions, viz. :
Ist. The positions which they are to occupy should be
selected, all parts of the permanent structures designed for
their use prepared, and all the mines and their attachments
provided, properly marked and stored during peace.
2d. The mines should be as strong, cheap, and simple, as*
is consistent with efficiency.
3d. They should, when used, be planted in multiple lines
or groups so dispoised as to close the channels ; and their
electrical connections should be so made that a limited num-
ber of cables being cut by enemy will not disable the mines
in such a way as to open a channel through the lines.
4th. The lines and groups must be thoroughly swept bj
the fire of the large and small guns of the deduce.
5th. Trained omcers and men in sufficient number to
place and work the mines must be always available.
237. Fixed torpedoes, known as submarine mines, serve
to close the channel to hostile vessels while leaving it open
to those of the defence.
Movable torpedoes, known as " torpedoes^'* may be used
to harass the enemy either at anchor or in motion.
Torpedo boats of small size and great speed, using spar
torpedoes or more frequently launching ^^autom(Mles^Gt
124 ELBMBKTS OP PERMANENT PORTIPICATION.
the Whitehead type, may move out from the harbors and
attack the fleet at distances entirely beyond cannon-range
and even in the open sea.
238. These torpedo boats and floating batteries are con-
necting links between the defence by land and sea forces.
239. Submarine mines are either self -igniting or con-
trolled from the shore. The self-acting, once placed, close
the channels equally to friend and foe. Those controlled
from the shore by electricity may at will be made active
against hostile, or harmless toward friendly vessels.
The latter class only can be employed in harbors which
are to be used for naval or commercial purposes.
240. Submarine mines of both kinds are either " buoy-
ant" or " ground."
The latter rest on the bottom, and may be used in water
not exceeding 40 feet in depth ; the former in deeper
^ater, being held in place by an anchor and a cable which
hold them at the proper depth below the surface.
241. The buoyant self-acting mines are exploded by the
•contact of a vessel with the mine itself ; the ground mines
by contact with the buoy, the explosion being caused by
the action of a very sensitive fuse.
242. In mines controlled from the shore, the buoyant
mine itself and the buoy attached to the ground-mine carry
a " circuit-closer" (or breaker) which, acting under the shock
-caused by the vessel striking them, either announces the
-contact to the operator in the electrical room, or fires the
mine as may be desired. Ir some cases they are fired only
by the action of the operatoi, the position of the vessel witn
reference to them being determined by observers on shore.
243. The details of the circuit-closers, annunciators and
arrangements for firing the mines differ materially in dif-
ferent nations, and are taught in their special schools. An
attempt is generally made to keep them concealed from
<)ther nations.
They necessarily are more or less complicated and deli-
-cate in their construction and adiustment, and require for
their effective use operators skilled in electricity, familiar
with delicate mechanisms, and of careful and non-excitable
<lisposition, assisted by trained and reliable men.
244. That system is best which is designed to fulfil only
the necessary requirements with the least possible complica-
tion of parts, ana in which the parts are as simple, strong,
^sily accessible, and easily understood by simple inspection,
as possible.
ELEMENTS OF PERMANENT FORTIFICATION. 125
In addition to this, the electrical connections of the dif-
ferent parts shonld, so far as practicable, be permanently^
made by the manufacturer, leaving to the operator only the^
necessity of attaching the torpedo wires and batteries for
testing and firing.
245. The requisites for the satisfactory workinff of the
electrical system are that each mine and cable may be tested
as to its condition, that contact with a mine must be sig-
nalled ; and that any mine may be fired by the operator,,
whether it has or has not been struck by a passing vessel.
The electric connection between the mines and the oper-
ating-room is by insulated cables of the kind used for sub-
marine telegraphs.
246. The cases of ground-mines may be of cast-iron of a
hemispherical or similar shape, as are the anchors of the
buoyant mines.
247. The cases of the buoyant mines in our service are:
made of mild steel of spherical shape. They have a volume
which gives them suflScient buoyancy to sustain their own
weight, that of the charge and mooring cable, and enough
excess to prevent them from being too much depressed ia
depth by the action of the currents of the place where they
are to be used.
248. They are charged with the most powerful explosive
attainable which is sate to handle, and not liable to be in-
jured by age or moisture. Gun cotton, dynamite and ex-
plosive gelatine, are the principal explosives now used.
249. Movable Torpedoes include, Ist. The ^^auto-
mobile" or self-propelling, of which the Whitehead and
Howell are examples. They contain their own motive
power, generally compressed air, and once launched, no
lurther control can be exercised over them. 2d. The " fish
torpedoes" of which the Lay and Simms are examples.
They are driven by liquid carbonic acid and an electric:
motor respectively, and are directed by electricity through
cables which they reel out as they run. Their effective
range is about two miles. 3d. Drifting torpedoes, which float
with the current and are intended to explode upon striking a
vessel. 4th. Submarine boats designed to pass under a
vessel, fix a mine to it, and retire before the explosion
occurs. A description of these different torpedoes does not
properly belong to the subject of fortifications.
250. The destructive range of submarine explosions
being very limited, every effort is made to cause them to
take place as near the vessel attacked as possible.
ISd ELEMEKTS OF PERMANRITT PORTTPTCATIO!r.
The law of diminntioii of prearar^ and kinetic energy, in
tbe transmission of the shock from sabaqaeous explosions
of the principal explosive compounds has been well deter^
mined by General Abbot and published in " Professional
Papers, Corps of Engineers, U. S, A., No. 23, 1881."
The resistance of modem vessels to these shocks is not so
well known, and can only be determined by many costly
experiments, comparatively few of which have yet been
made.
251. Organization of Fortifications, Mines, and
Torpedoes for the Defence of Harbors. The tor-
Sedo boats working out beyond cannon-range form the
rst line of defence. When driven in, they retreat until
-covered by the forts, and come into action again if oppor-
tunity offers.
262. The fish torpedoes come into play about two miles
from shore. They have not yet had the test of actual use
in war.
253. The forts and submarine mines arranged in defen-
• sive relations form the main line of defence upon which the
Bafety of the harbor will usually depend.
254. Submarine mines derive a moral effect from the
destruction which is worked by a single one successfully
exploded, which prohibits the passage of the hostile fleet
until the mines are destroyed or rendered inert. To render
them harmless the enemy must capture the fortifications
<;overing the operating rooms, cut all the cables, destroy
the mines by blowing them up with counter mines, or
disable them by grappling and dragging.
That these operations could be carried on by ships or
l>oats in narrow channels under the close, well-directed fire
^f powerful guns, and the action of movable torpedoes, and
of the mines themselves, is, if not absolutely impossible, of
evident improbability. It may be said that a harbor pro-
vided with an efficient torpedo defence, thoroughly supported
ty both large and small guns, is practically impregnable by
naval attack.
If, however, the supporting guns are not covered by forti-
fications strong enougn to enable them to hold their own
against the heaviest ship's guns, they may be silenced and
captured, and with their fall the torpedo defence falls also,
as it is manifest that the torpedo defence can have no
value whatever when the control of its firing arrangements
falls into hostile hands.
266. The possibility that the enemy may break through
a single or even double line of mines by sacrificing one or
two snips, by well-worked counter-mines, by cutting, one or
two groups of cables by a fortunate shot, or by the occur-
rence of one of the many accidents which may disable some-
what delicate electrical apparatus, makes it necessary that
the third condition above given, should be fulfilled.
266. Remarks. The more modem and better-developed
«vstems of submarine mines as harbor defences have not as
yet stood the test of actual attack. In all the wars which
have occurred, since their development, their moral effect
has deterred naval commanders from assailing harbors de-
fended by forts and supposed to be supplied with a system
of submarine mines.
)28 ELEMENTS OF PERMA^EJifT FOBIIFIOAIIOlSr.
CHAPTER X.
THE DEFENSIVB OROANIZATION OF FRONTIERS WTTK:
PERMANENT FORTIFICATIONS.
267. No State, in the present condition of civilization^
can be regarded as secure from foreign military aggression^
the accessible points of whose frontiers are not occupied by
permanent fortifications of such strength as shall prevent
an enemy from obtaining possession of them by a sudden
assault, and thus procuring the means of penetrating into-
the interior. Guided by the experience of centuries of
wars, and the daily increasing facilities which the improve-
ment in the matSriel of armies and their transportation
afford for rapid and powerful offensive operations, the
ruling states of Continental Europe have, within the last
half-century, not only made every effort to place their fron-
tiers in an unassailable condition, but also their ^reat centres,
of population and wealth in the interior, beyond the chancer
of a sudden attack from an enemy who might force hia
way through the frontier defences and march rapidly^ upon
them, thus making these positions the rallying points where
a defeated army can find a safe resting-place until it can be
reorganized and sufficiently strengthened to resume the
offensive.
Such seems to be the result at which the generals and
statesmen of Europe have arrived, after the most mature
and careful consideration of the important problem of na-
tional defence ; at a time when the utility of permanervt
fortifications was seriously called in question,, by some
who pointed, in support of their views, to the very ineflS-
cient part the great number of fortified places had played
in the wars waged by Napoleon, when, by means of over-
whelming numbers in the neld, he was enabled to disregard
such places, the garrisons of which were too feeble to make
any efficient offensive movements, until the defeat of his
adversary, in one or more great pitched battles, necessarily
also threw them into his possession.
ELEMENTS OF PEBMTANEKi FOllTII'iCATlON. 12S^
In view of the argumentB based on these events, the
opinions of Napoleon himself should earrv great weight.
In speaking of tlie bearing of permanent fortffications in a
defensive war, he says : " If fortresses can neither secure a
victory, nor arrest the progress of a conquering enemy, they
can at least retard it, and thus give to the defence the
means of gaining time — a most important advantage in all
warfare." In like manner the Archduke Charles of Austria^,
who showed himself one of the ablest adversaries with
whom Napoleon was called upon to cope, took the ground
" that a aefensive warfare cannot be systematically and
successfully carried on in a country which is not provided
with fortresses that have been planned and distributed
according to strategical requirements." Like views were
held by the Duke of Welhngton ; and it is probable that
no great general, from the earliest period of militarv opera-
tions down to the present moment, has ever entertamea the
contrary.
Without going further back than the Franco-Prussian war
of 1870-71, we find that while the entrance of the German
army upon French territory was easily accomplished, owing
to its superiority in numbers, organization, and rapia
mobilization at the first stage of the war, it was necessary
to detach from the advancing army the large forces invest-
ing Metz, Strasburg, Belfort, and other fortified places.
These forces, with their artillery, were occupied from 3^
to 100 days in reducing these strong places, which were uponr
their lines of communication and could not be neglected.
The fortifications of Paris, although their scarp walls were-
exposed and their casemates not strong enough to resist the
German artillery, held the German army in check from the
middle of September until the end of January, affording^
four and one half months for the organization of an army of
relief in the other parts of France. ^ ^
The fact that this opportunity was not made use of has no*
bearing upon the value of the fortifications, which more-
than fulfilled their original design.
That this value was appreciated by both sides, is shown^
in the immense sums spent by them since that time in build-
ing new forts and remodelling the old. The only question,
then, on this subject that remains for solution by a State isy
in what way such a means of security from aggression can
be best adapted to its own geographical, political, and mili-
tary status.
268. In a country like our own, with so vast an extent*
9
180 BLKMBim OF PSmfANBHT FOBTinCATZOK.
of 8ea-coa8t and inland f rantier, and with political and social
institationB which are so antagonistic to eveiy approach to
a large standing army as a measare of national safety, this
question is one of peculiar importance, both from the open
character of this extensive frontier, and from the almo^
incredible facility with which considerable armies, with all
their materid^ can be concentrated on distant points by the
aid of steam. The weakness of onr immediate neighbors on
the one side, and the daily increasing mutual commercial
interests between us and the greatest naval power in the
world, by which we might be seriously threatened both
along our seaboard and our esrtensive line of inland frontier,
it is true, would seem to favor the hope that the day is still
i^mote, and from present appearances, may never arrive, in
which our country will have to apprehend anything in the
ishape of invasion except along the sea-coast ; and we may,
therefore, dismiss from our consideration any other pro-
vision against this eventuality (which, should it happen,
looking to our resources in men and means, will hardly ex-
tend inland beyond a few marches), except what we nave
already attempted, viz., the securing of our principal har-
bors, naval stations, and commercial marts from a naval
attack, or from one combined with the operations of a land
force, which, from the causes above alluaed to, could be but
of short duration.
269. In the organization of the inland frontier fortifica-
tions of a state, the points to be principally regarded are the
principal avenues oi access to it, and their topographical
feature^ as they lend themselves more or less to strengthen
the artificial defences. In conducting an invasion across an
inland frontier, the march of the enemv must necessarily be
along the roads that intersect it, as these afford the only
means for transporting the Tnateriel^ etc., of the army. The
points, therefore, or places in their neighborhood where the
principal roads or other avenues of communication cross the
frontier, particularly those which lead to the great centres
of population and wealth, are the ones which would neces-
sarily call for permanent defences. No absolute rule can be
laid down for the distribution and strength of such works
along a frontier. Everything must depend upon the greater
or less of facility presented to an enemy for penetrating at
one point rather than another, and upon the ulterior advan-
tages the one may present to him over another.
260. Bivers and mountain ranges are the natural fortifi-
i^ations of states ; and where they form the frontiers they
greMly facilitate the ftp^plicfttian of arrtifioial defensive
ineans, as they present bat few, and those in general im-
portant, points of access.
When these points on a river are fortified, an invading
force, however powerful, cannot, without great risk, cross
the river without' first gaining possession of them; for, even
should a sufficient detachment be left to observe and block-
ade the fortresses, the main army, in case of retreat or any
disaster, might be placed in an extremely critical position,
in its movements to recross the river, with the garrisons of
the fortresses threatening its flanks and rear.
261. In offensive operations, fortresses upon a river fron-
tier form one of the strongest bases of operations. If a
river intersects the frontier, the point where it crosses it, or
43ome one in its vicinity, should be occupied by a permanent
work ; amon^ such points those are more peculiarly neces-
sary to be held where a river forming the frontier is inter-
isected by another navigable one which lies wholly within
the frontier.
The importance of thoronghly occupying such points is
obvious, as they afford an army on the defensive the means
of passing readily and safely n*om one side to the other of
the river, either to evade a force too powerful for it to cope
with in the open field, or, when an opportunity offers, from
any imprudent movement of an invading force on one side,
to throw itself suddenly from the other on its flank or rear,
and thus force it to a retrograde movement.
262. With respect to mountain passes, the main roads
alone will require permanent works. If the passes are in-
dependent of each other, a work will be necessary for each
one separately ; but where several unite at the same pointy
upon or within the frontier, a single work placed upon this
point will suffice. Local circumstances will determine the
point in each pass which, occupied, will offer the greatest
advantage for obstructing the march of an invading force
and retarding the bringing forward its materiel. The only
rule that can be given is that, while the position selected
shall satisfy these conditions, there shall be every facility of
communication between the fortress and the interior for re-
ceiving suppUes and reinforcements. This rule would lead
gener^ly to the selection of some point of the outlet within
the frontier as the prjper one.
263. The number of fine natural harbors and roadsteads
on our seaboard, where the largest fieets can find a secure
anchorage at all seasons; the proximity to the ocean of
132 ELEMEKTS OF PERMANENT FOBTIFIOATIOK.
many of our most important cities, towns, and popnlons-
villages, bv which they are not only exposed to the usual
dan^rs of naval attacks, but to incursions from an enemy's-
iana forces ; together with the large rivers which, having
their outlets on this seaboard frontier, are navigable for long-
distances within it by vessels of the greatest burden — have
given to the subject of sea-coast defences a particular prom-
mence among ourselves.
The means of defence disposable for the security of such
points consists in permanent works arranged to meet an
attack both by sea and laud, and of such strength as the
presumed nature of the attack will demand ; of such tem-
porary fortifications as the exigency of the moment may
point out ; of movable land forces ; and of floating defencea
to act in aid of the others.
264. The character of the permanent defences will de-
pend upon the object in view. Where this is simply to
exclude an enemy's fleet from the use of a harbor or road-
stead, which offers to him no other inducement for its occu-
pation but that afforded by a secure anchorage, one or more
small works of sufficient strength to prevent the success of
an open assault upon them, armed with heavy mortars and
guns with long ranges, that can reach by their fire every
point where an enemy's ship could safely anchor, will be
sufficient.
The points to be occupied by these works, as well as their
plan, will depend upon the natural features of the harbor
or roadstead itself.
They will usually consist either of open works with ffuns
in barbette and mortars sweeping all points of approach to
and within the harbor ; or of a combination of covered and
barbette batteries; with ditches or other obstacles, and
bomb-proof barracks of sufficient capacity to hold the gar-
rison necessary to beat off an open assault on the battery by
land, and to be secure from a coup-de-mwm.
Like defences will also be sufficient for the security of the
smaller classes of towns and villages, which would probably
offer a temptation only to a small naval force.
266. In the case of important commercial cities and lr>
naval depots lying within harbors more or less accede
both to sea and land attacks, the character of the defei
called for must necessarily be commensurate with the ma^
tude of the interests to be guarded, and the consequj .i',
temptation to an enemy to put forth great efforts for th^.i;
occupation and destruction.
ELEMENTS OF PERMANENT FORTIFICATION. 133
The aventieB of approach to these objects by sea, which
<5an be brought within range of cannon and mortars in forti
:fications on the shore, or in armored forts erected on natural
or artificial islands, should be occupied to a distance that
will prevent a fleet from approaching near enough to open
a bombardment, and if pi-acticable also force the enemy, if
he venturea a land attack, to disembark his forces either at
«o great a distance from the object to be reached that he will
not be able, by a sudden movement of this nature, to effect
a surprise ; or to limit his landing to such points on the
-coast as, from their exposed position, may render the
cooperation of the naval and land forces very uncertain,
And, in case of a storm, place the latter in a very perilous
condition if attacked.
These works will form the exterior chain of the defences.
IV^ithin these, batteries, either open or casemated, as the
localitv may seem to demand, should occupy all the most
suitable positions for sweeping the path that a fleet must
follow by powerful cross, direct, and enfilading fires, and
for reaching every point of anchorage within the harbor.
The batteries commanding the inner harbor within easy
Tange of the city have especial value in attacking and de-
stroying, by their cross-fire, any ships which might run past
the outer forts. The presence of such batteries will prob-
ably deter the ships from attempting this kind of attack.
On the land approaches, points should be occupied by
forts of a permanent character, which will prevent a suflJ-
ciently near approach to bombard the city or depot, and,
in combination with temporary works, will afford an in-
trenched field of battle tor the troops on the defensive.
These will form the exterior line of the land defences, the
interior line being either a continuous enceinte strong
enough to resist assault, or else a suitable combination of
either continuous or detached field works of such strength
and armament that the enemy, in any attempt to carry them
by an open assault, will be made to suffer heavily, even if
he is not repulsed.
The security of objects of this character will be greatly
increased when they lie at some distance within the sea-
•coast frontier, and can only be approached by water through
such comparatively narrow defiles as even our largest rivers
present, and by land after one or more marches. These
•defiles will, for the most part, not only present admirable
positions on their banks from which an assailant's fleet can
be enfiladed within the range of the heaviest guns, but
134 ELEMENTS OF PEBMAKEKT FOBTIFIGATIOlf.
frequentljr others, at points where the river narrows, or
changes its course, where works occupying the opposite
banks will give the means of rendering the river impass-
able by torpedoes, booms, rafts, or other floating and sunken
obstructions, which cannot be removed except by getting
possession by a land attack of the defences which guard
them.
266. Wherever harbors or bays are of such extent that
their entrance cannot be interdicted to an enemy's fleet, nor
secure anchorage within them be prevented, of which we
have examples on our own coast, the case falls teyond the
province of fortiflcation, and must be left to floating de-
fences for a solution. Here even some fortified harbors on
the shores of such extensive estuaries may give secure places
of refuge for ships-of-war, from which they may at any
moment sally when they can take the enemy at a disadvan-
tage, or into which they can retreat if attacked by a supe-
rior force.
267. In the great military states of Oontinental Europe,,
the question as to what extent the sreat centres of popula-
tion and wealth in the interior should be covered by fortifica-
tions, has been submitted to the investigation of the ablest
engineers and statesmen, from the time of Yauban down to
the present day; but more particularly since the fall of
!N'apoleon, a catastrophe which might not have taken place
had Paris been secured by fortifications which would nave
prevented a cotup-de-^mairiy when the armies of the Allies-
gained possession of it as the result of a pitched battle.
Whatever differences of opinion h^ve been called forth aa
to the mode of accomplishing this object, as shown in the.
published views on the proposition to fortify Paris, there
seems to have been none among those best qualified to de-
cide upon it as to the great importance of so fortifying this-
capital and other lar^e places in the interior, as Lyons, etc.,
which from their position must be of the highest strategical
value in the case of a successful invasion by a large army, as
not only to prevent their wealth and resources from falling
into the possession of the invading force, but to make them
safe rallying-points for beaten and dispeirsed forces, and
depots for organizing new armies.
The plan that has been adopted for this end, both in
France and in most of the other cities of Europe which have
been either newly fortified or had their old work strength-
ened within this period, is to surround the city by a con-
tinuous enceinte of greater or less streni^b; but one secure
BLSMEKTS OF PEBHAKEITT POBTIVICAXIOIT* 131^
from a coup-de^mam, and to ocenpy vn^ forts of a pw«
manent character the most suitable points in advance of the
enceinte, to prevent an enemy from bombarding the city, or
penetrating between them without first gaining possessioa
of them, liy this plan, it is proposed to gain all the advan*
tages offered by the passive resistance of fortifications and
the activity of 9, disposable movable force occupying the zone
between the enceinte and the forts as an intrenched camp,
upon which the forts and temporary works thrown up be- '
tween them would render an open assault too perilous to
be attempted.
268. The fortifications of Paris, of 1840, consist of a
continuous bastioned enceinte, without outworks^ with a
revetted scarp of the usual height, to secure it from esca**
lade, and a ditch with a counterscarp of earth. The ad*r
vanced forts are either quadrangular or pentagonal bas-
tioned works, inclosing all the means of security for their
garrisons, as bomb-proofs, etc., their plan being skilfully
adapted to the site, and their mutual bearing on the defence.
After the siege of 1870-71, these fortifications were in-
creased by the addition of an exterior line of forts occupy-
ing the outer crest of the basin of Paris approximately upon
the circumference of a circle of 24 miles diameter, that of
the inner belt beinfic about 12 miles and the enceinte about
6 miles. *
The new detached forts are polygonal without outworks.
The fortifications of Lyons present more diversity, both,
in the plan and details of the enceinte and forts ; although
the general system is the same as that of Paris. There is
here seen a more extensive application of casemated and gal-
lery defences, both for exterior flanking and for the' defence
of the interior forts, growing out of the more broken feat-
ures of the site generally, and frequently the more confined
space occupied by them.
In Grermany the same general system of a continuous
enceinte, with strong advanced isolated works, has been
followed ; the whole being so planned and combined as to
meet the distinctive features of what is known as the Ger-
man system of fortification. The principal changes in those
have already been described.
269. In our own country, where the important centres of
population and wealth lie almost immediately upon the sea*
Doard, it would seem impracticable, in view of the rapid
spread of population around them, and the consequent
cnanges in local features, to resort to any defences of a per^
136 ELEHE17TS OF PEBMAKENT FOBTIFIOATIOK.
maDent character to secure them from a land attacli, even
'were the nation willing to assnme the burden of the great
outlay for such an object ; as, in a few years, the works of
to-day might be rendered useless by the changes referred
to. Even in Europe, the strongest despotic governments
have been obliged to cede what seemed military exigencies
to the demands of the social condition ; and either to raze
the fortifications of cities, to give room to a crowded popu-
lation, or else to suflEer such encroachments on the ground
necessary for their action as to render them nearly useless.
The only defensive resource that seems left to ourselves, in
Jike cases, is in the use of field-works — one which our mili-
tary experience shows may be relied upon with confidence,
ifio long as the military aptitude of our population remains
xmchanged from what it nas thus far proved itself to be.
W—
ELEME17TS OF PEBMAXE^I FOiiTIFIGAIIOJbi. 137
CHAPTEE XL
emSNULRY OF THB PROORESS AND OHANaBS OF
FORTIFIOATION.
L
270. The records of history and the vestiges of remote
civilization show that the art of fortification, in some guise
or another, has been in practice throughout all nations, even
in the lowest stages of social progress ; and that, wherever it
has been cultivated, its character has been more or less in-
fluenced, not only by the natural features of the country,
but by the political and social conditions of its inhabitants.
In its earliest applications, we find men resorting to one
or more simple enclosures of earthen walls; or of these
surmounted by stakes placed in juxtaposition ; or of stakes
alone firmly planted in the ground, with a strong wattling
between them ; or of timber in its natural state, having its
branches and the undergrowth strongly interlaced to form
an impervious obstruction, with tortuous paths through it
onlv known to the defenders.
A resort to such feeble means shows not only a very low
state of this branch of the military art, but also of that of
the attack ; as defence of this kind would present but a
slight obstacle, except against an enemy whose nabitual mode
of fighting was as cavalry, or against one not yet conver-
sant with the ordinary plans for scaling. This class of for-
tifications for the defence of entire frontiers has been mostly
met with in the east of Europe, and was doubtless, at the
time, found to be a sufficient protection against those
nomadic tribes that for ages have roamed over its vast
plains, and who are only formidable as a mounted force.
271. To secure greater permanence and strength, the
next step was to form walls either of rough blocks of stone
alone, or of these intermixed with the trunks of heavy
trees. Obstructions of this kind could only be used to a
limited extent, and were confined to the defences of places
Ids ELEMEKTS OF PEEMASTfiVT FOBTIFIOATIOiC.
forming the early centres of population. As human in-
vention was developed, these, in their turn, were found to
present no serious obstacle to an assault by escalade; giving
to the assailed only the temporary advantage of a more
commanding position; and they gave place to walls of
dressed stone, or brick, whose height and perpendicular face
alike bade defiance to individual attempts to climb them, or
the combined effort of an escalade. From the tops of these
inaccessible heights, sheltered in front by a parapet of stone,
and, in some cases, by a covered corridor behind them, tb^
assailed could readily keep at bay any enemy, so long as he
was exposed to their missiles ; but having reached the
foot of the wall, he here found shelter from- these, and, by
procuring any cover that would protect him from object*
thrown from above, could securely work at effecting a breach
by mining. It was probably to remedy this defect of simple
walls that towers, which at first were nothing more than
square or semicircular projections built, from distance to difr-
tance, in the wall itself, were first devised ; and which sub*
sequently were not only enclosed throughout, but divided
into stories, each of which was provided with loop-holes, to-
flank the adjacent towers and the straight portions of the
wall between them. Each tower could l)e isolated fromth<»
straight portion of the walls adjacent to it, by an inter^
ruption at the top of the wall, over which a comraunicatioa
between the tower and wall could be established by a teiOfi^
porary bridge.
272. These formidable defences were, in their turn, found
to be insufficient against the ingenuity and skill of the as.^
sailant, who, by means of covered galleries of timber, some-
times above ground and sometimes beneath, graduallv woa
his way to the foot of the wall, where, by breaking his way
through it, or by undermining and supporting it on timber
props to be subsequently destroyed by fire, he removed the
sole obstruction to a bodilv collision with the assailed.
These methods of assault were in some cases supported bj
means of high mounds of earth which were raised in an in-
clined plane towards the walls, and sometimes carried forward
to them, from the top of which the assailant, by the erection
of wooden towers, covered with raw hides to secure them
from being burnt, could command the interior, and, driving
the assailed from the walls, gain a foothold on them hj
lowering a drawbridge from the wooden tower.
273. These changes in the attack led to new modificik
tions in the defence^ which consisted in surrounding the
:BL£M£KTS of PBBMANBNT FOBTXi'ICATIOK. U9
place by wide and deep ditches, of which the walls formed
the scarp, the counterscarp bein^ either of earth or revetted.
This placed a formidable obstacle to the mode of attack bjr
mining, and also to the use of earthen mounds, as these last
had to be constructed across the ditch before they could gain
sufficient proximity to the wall either to form a communi
cation witn its top, or to breach it by means of the battering-
ram ; the ditches also were filled with water whenever thiA
obstruction could be procured, and when dry they formed a
defile through which the assailed often sallied upon the aisk
sailant with success when found at a disadvantage in it.
274. The gigantic profile often given to tne fortifica-
sions of antiquity seems almost incredible, as well as their
extent. In many cases a double wall of stone or brick was
filled in between with earth, forming a wide rampart upon
which several vehicles could go abreast. Not only was the
space enclosed by some of these fortifications that requisite
for the habitations, but ground enough was taken in to add
considerably to the food of the inhabitants and cattle, for
the long periods to which blockades were in many cases*
extended, when all other means of reducing the place had
failed.
The wall built by the Romans, between Carlisle and New-
castle, to restrain the incursions of the Picts into the souths*
ern portions of the island, was seventy-three miles in extent^
about twelve feet in height, and nine feet in thickness. The
extent and dimensions of this work sink almost into insig-
nificance when compared with those of the celebrated wall of
China, built to restrain tlie incursions of the Tartars. This,
structure is about 1500 English miles in length ; has a
height of 27 feet ; its thickness at top is 14 feet. The lower
portion of it is built of dressed stone, the upper of well-
burned brick. It is fianked at distances of about 80 yards
apart by towers in which iron cannon are found.
In the great extent it embraces, it necessarily crosses hills,
and valleys, and in many places important defiles. An
examination of its parts has shown that in its plan there was
an evident design to adapt it to those features of its site, as
it is well thrown back to the rear of difficult passes ; and at
J joints where there is most danger to be apprehended
rom attempts of invasion, there are several walls in suc-
oession.
276. The mode of attack of fortified places resorted to
by the an4^ients was reduced to settled rules, and brought to
140 ELEMBlirrS OF PERMANENT FORTIFICATION.
the highest state of perfection by the Greeks, about the
«poch of Alexander the Great and the immediate successors
to his vast conquests. An essential feature in it, whether
in the sieges of inland fortresses or those on the seaboard,
was to cut off all communication between the place and the
exterior, by hemming it in by sea and land, with stationary
forces, covered themselves by lines of intrench ments strength-
ened by towers, and, in the case of sea-coast places, also by
:fleets, from all assaults both from without and from the
place invested.
Having selected the portions of the place on which the
attack was to be directed, a second line was formed parallel
to the first, which was covered, and constructed of timber
and wicker-work, and secured with raw hides to prevent its
being set on fire. From this sheltered position, which
served also the purposes of a lodging for the besiegers, the
besieged were annoyed with missiles thrown from all the
^irtillery known in tnat day, consisting of the ordinary bow,
the cross-bow, and the various machines for projecting
ieavy stones and other projectiles.
Under the diversion thus made, the besiegers pushed for-
ward from this line several covered approaches of a like
^construction directly upon the place, for the purpose of
fining the counterscarp of the place, and from that posi-
tion filling up the ditch with stones, earth, heavy logs, etc.,
to prepare the way for placing the battering-ram in position
to breach the wall. The tower in which this machine was
E laced usually consisted of several stories, and was occupied
y troops who cleared the top of the wall assailed of the
besieged. This operation was frequently aided by other
high towers, which were advanced either along the natural
level of the ground, or upon artificial mounds forming in-
clined planes, towards the place, by means of which the
towers could be given any desirable command over the in-
terior.
276. The defence was mostly of a passive character ; the
besieged trusting mainly to the strength of their defences,
under cover of which they resorted to all the means used by
the besiegers for assailing the latter when they came within
reach of their missiles ; using cranes and other devices to
fieize upon the implements planted at the foot of the wall,
and carrying out galleries of countermines to overwhelm
the artificial mounds and their towers.
277. The Bomans evinced their decided military apti-
tude, not only in the employment of the ordinary systematic.
ELEMENTS OF PERMANENT FORTIFICATION. 141
methods of the attack and defence of fortified places, but m
their application of the cardinal principle of mutual defen-
sive relations between the parts of a fortified position, ob-
tained by advanced and retired portions of the enceinte '^
and also in the adaptation of intrenchments to the natural
features of the sitej as shown in the fortifications of some of
the permanent frontier camps of their military colonies.
These principles have also been noticed in some of the for-
tified positions of India, which consist of a mural enceinte
with tne earthen ramparts flanked by round towers, and of
round towers in advance of the enceinte connected with it
by caponnieres.
"With the decadence of the Boman Empire, the art of
fortification, like the other branches of the military art, waa
brought to so low a stage that strongholds which, skilfully
defended with energy, would have baflBied the efforts of a
well-trained assailant in the art of attack, fell, almost with-
out resistance, into the possession of the fierce northern
hordes, by which the whole of civilized Europe was over-
run.
278. The remains of the structures raised for defensive
purposes, during the prosperous days of the Empire, were
probably the sok means of protection afforded to the inhab-
itants 01 the towns that still maintained a nucleus of popu-
lation, until the rise of the Western Empire, under Cnarle-
magne ; and it was the necessity felt bv this conqueror, not
only of securing his con(jne8ts, but oi checking the irrup-
tions of the barbarous tnbes along his extended frontier^
which led him to erect tetes-de-pont on the frontier rivers,
and a line of strong towers, for ^rrisons of a few men, upon
the most inaccessible and prominent points of this frontier ;.
the latter bein^r a means which was subsequently resorted to
for a like purpose in the Spanish peninsufa. ^
Henry I., of Germany, introduced a more important and
more systematic addition to these permanent trontier de-
fences, by surrounding the frontier towns and villages, occa-
pied by militarv colonists, with walls and ditches, to secure
them from sucn attacks as they might be exposed to, and
subsequently adding a second line of strongholds within the
frontier, by which an irruption through the frontier line
might still be checked.
279. During the general disorganization of States under
the feudal system, the free cities which depended for their
defence on the burghers composing the different crafts,
every individual who could maintain a few retainers in his
14* IXEMBXTS 0? PEHXANEirr FOUTIFIOATIOiT.
IMtjy And the clergy, even^ resorted-^-eacb according to their
separate views — to such means of defence as would best
secure them from the attacks of others in a like condition,
and woald enable them to carry oat that system of pillage
which had become general amongst the nobles and other
military chieftains.
280. From this state of society sprang np those castles,
placed in the most inaccessible positions on the lines of
•communication which the little inland commerce that was
still carried on was obliged to traverse. These were pro-
vided vdth every possible device for an obstinate passive
defence, being surrounded by a wide and deep ditch, or
moat, over which a drawbridge was the only communica-
tion to the main entrance, which was flanked by towers on
the exterior, and closed with massive doors; the tortuous
passage which led from them to the interior of the castle
Doing further secured by a grated portcullis, which could
be let drop at a moment's notice, to arrest a sudden
assault.
To these means were often joined, besides the ordinary
measures of loop-holes and machicoulis in the walls and
towers for annoying the assailant, a high interior tower,
termed a keep, or donjon, which, commanding the exterior
•defences, was also a watch-tower over the adjacent
■country.
The keep, which was the last defensible point, was, in
Bome cases, provided with a secret subterranean passage,
having its outlet in some distant concealed spot, through
which succor could be introduced into the beleaguered
<sastle ; and, in the last extremity, the garrison find safety in
a stealthy fl[ight.
281. The fortifications of towns partook of the same
characteristics as those of castles. From the custom of
assigning to the different burgher crafts, each of which had
an independent military organization, the exclusive guard-
ianship of portions of the enceinte, as well as their erection
and repairs, great diversity, and frequently a whimsicality,
in the defensive arrangements was the natural result ; the
evidence of which still exists in the remains of the walls of
some of the old Continental cities. The art, for the most
part, was practised by ambulatory engineers, who, like the
secret orders by whom the bridges and churches of the
same period were built, offered their services wherever they
were wanted. Many ideas were also introduced from the
East by the Crusaders, as exhibited in the fortifications of
ISLBMBKTg OF PBBlf AK'BHT FOBTIFICATIOK. |^
<»gtle» and dtid» banging to ther Templars and otW re-
ligions military orders.
282. With the invention of gunpowder, and its applies!-
tion to military purposes, a gradual revolution took place
in the general forms and details of fortification. It was
soon seen that naked walls alone did not offer either suit»
■able conveniences for the new military machines, or suffi-
cient protection against the projectiles thrown from them.
This led to the introduction of earthen ramparts and parar-
pets, which were placed against the walls and suitably
arranged to meet the exigencies of the moment. The art
received something like a scientific basis about this time in
Italy, from which the names and forms of n.ost of the
elements of fortification now in use are derived. The Italian
engineers, like their predecessors, went from state to state
to offer their services wherever they were needed, and in
this way disseminated the principles of their school through-
out Europe.
283. It was at this epoch that the bastioned form of for-
tification first appeared, but the precise date and the author
of the invention are both unknown. With its introduction
iJie importance of separating the parts of a line of fortifica-
tion into advanced and retired parts, the latter fianking and
defending the former, seems to have been rec(^nized as an
•essential principle of the art. With these changes in the
lorm of the enceinte, the art was gradually improved by
the addition of outworks to increase the amount of cross
and fiank fire; the introduction of bomb-proof shelters for
the troops and other purposes ; the substitution of earthen
for stone parapets; and the attempt to conceal the scarp
"Walls from the enemy's batteries by decreasing the command
and deepening the ditches of the enceinte.
By these gradual changes stone walls, which in the old
fortifications were the essential defensive feaiures, came at
length to be regarded in their true character, simply as pas-
sive obstacles to an open assault by escalade. The property
of earthen parapets, of resisting without material loss of
strength the long-continued fire of the assailant's heaviest
funs, showed that the same defensive means were applica-
le both to works of a permanent and of a temporary char-
acter ; and were equally available for the purposes of the
assailant 'and the assailed. The measures for the attack and
the defence of positions were thus reduced to the same gen-
eral principles, differing only in the forms and dimensions
of the elementary parts, as circumstances seemed to demand.
i44 ELEMENTS 07 PEBMAKENT FOBTIFIOATION.
284. Italian School. As above stated, the first em-
ployment of bastions as they now exist was made by the
Italian engineers; and, as far as has been ascertained,
towards the close of the fifteenth or the commencement of
the sixteenth century. To whom the credit of their inven-
tion is due is not known. In the earh'er fronts of the Italian
school the bastions are very small, and they are connected
by curtains varying from 250 to 500 yards in length. The
bastion flanks, which were perpendicular to the curtains^
were divided into two portions ; that next to the curtain,
which was one-third of the entire flank, was thrown back
and covered by the portion in advance, which thus formed
what received the name of the orillon. The lower part of
the retired portion was casemated for cannon ; and behind
this, and separated from it by a dry ditch, rose a second
flank, having the same command as the other parts of the
enceinte parapet. In some cases a small and very obtuse
bastion was erected at the middle of long curtains.
The ditches of the enceinte were usually about 100 feet
wide and 24 feet deep ; the counterscarps being parallel to
the bastion-faces.
A scarp gallery, for the purpose of mining, ran through-
out the enceinte scarp, and communicated with galleries
leading to other points.
The parapets, at first of masonry, were afterwards of earth,
and from 18 to 24 feet thick. The earth of the rampart
was sustained on the interior by a wall. Eamps estab-
lished a communication between the interior and the ram-
part.
The defects of these early fronts were soon felt, and a
more complicated but improved method adopted, in which
the bastions were enlarged and the curtains diminished*
The retired flanks were still retained, but the orillon instead
of being angular was rounded. To these improvements,
cavaliers were sometimes added to the bastions, which in
those cases were made without retired flanks ; or placed on
the curtains, when, from the configuration of the site, some
portion of the ground within cannon-range could not be
swept from the enceinte parapet. The covered-way was
introduced and became an integral part of the front ; and a
small demi-lune or ravelin was placed in advance of the
enceinte ditch, forming a tete-de-pont to cover the commu-
nication, at the middle of the curtain across the main ditch,
between the enceinte and the exterior. The covered-way,
ELEMENTS OP PERMANENT FORTIFICATION. 145
which at first was of uniform width and bordered the maia
fid derai-lune ditches, was subsequently provided with,
salient and reentering places-of-arras. These various essen^
tial parts of a fortified front were gradually ameliorated by
the Italian engineers, but not before the Italian school had
left its impress upon the fortification of all the other states
of Europe; as the Italian engineers, from their superior
acquirements, were in demand throughout these states.
286. Spanish School. From the existing fortifications
of Spain, the influence of the Italian school may be traced^
but modified by national characteristics; the works seem
organized more for a purely passive defence ; the covered-
way, that essential outwork to an active defence, being in
many cases omitted ; the means of annoying the besiegers
by fires being greatly multiplied ; and the outworks gen-
erally being arranged with a view to a purely passive de-
fence. Besides this, the dimensions of the profile and
height of scarp were increased as a greater security against
escalade ; interior retrenchments were multiplied, sometimes
enclosing a bomb-proof keep to render the defence more
obstinate.
The Spaniards, although resorting but little to sorties,
show great skill and pertinacity in the defence of breaches,
and in availing themselves of all obstructions for prolonging^
resistance.
From the broken character of many of the sites of their
fortresses, the Spaniards resorted very much also to detach-
ed works to occupy commanding points from which the^
main work could be annoyed.
These they also generally organized for a strictly passive
defence, leaving them more to their own resources tnan to
any cooperation with the main work.
286. Dutch School. This school took its rise in the
political necessities of the times, in which the national spirit
was aroused to throw off an onerous foreign yoke. The
aquatic character of the country, and the want of time and
pecuniary means, led to those expedients of defence which
are never wanting under like circumstances. The deficiency
of earth led to the formation of low parapets for the main
enceinte and wide ditches filled with water. The mair
enceinte was usually preceded by a second one with ver
low parapet to sweep the surface of the wet d* u ; aiid
this second enceinte was separated from the first oy a dry
ditch, which favored sorties, and which was provided with
all the means, as palisades, tambours, and block-houses, for
146 SLBHEKTS OF PEBMAKBKT FOBTIFIOATIOK.
offensive returns and surprises. The second enceinte was
generally covered from an exterior command by a glads in
advance of the main ditch. The covered-way between the
glacis and the ditches was, to a great extent, deprived of
its essential offensive feature by an exterior wet ditch
made at the foot of the glacis ana enclosing it, over which
communication with the exterior was kept open by tem-
porary bridges.
The works were usually very much multiplied and their
combination complicated ; features the less objectionable
where their defence chiefly rested upon the inhabitants who
had become familiar with aU their turning and as offering
obscurity of design to an assailant who might force his wav
into them. The whole of the defensive measures of this
school seem to have had solely for their object a strictly
passive resistance. With this view long lines of Intrench-
ments, supported from distance to distance by f ort8,connected
their frontier towns and villages, affording a sufficient ob-
stacle to marauding expeditions, and requiring the efforts
of a strong force to break through them. At a later pe-
riod, taught by the experience of their earlier efforts against
the most military state of that epoch, covers that would
afford security against incendiary modes of attack were
provided ; and revetments of masonry substituted for the
earthen slopes of the ramparts, particularly where the.
ditches were dry. These successive changes, partly influ-
enced by the Italian and Spanish schools, with which the
Dutch engineers were brought into contact through their
connection with Spain, were the natural precursors of the
system of Coehoorn, the most distinguished engineer of the
iJutch school, whose works are characterized by many of
its essential features.
287. Oermaji School. The Germans reckon a number
of original writers on fortification, among the most noted
of whom are the celebrated painter, Albert Durer, Daniel
Speckles, and Kimpler. In the propositions of these writers
are to be found the influence which the Italian school natu-
rally exercised throughout civilized Europe, and the germs
of many of the views held by the Gterman school of the
present day ; which last seem, however, to have been taken
more immediately from the propositions of Montalembert
and Camot.
288. Swedish SchooL The part played by Sweden
upon the theatre of Europe, under ner two celebrated mon-
ariehsy Gustavus Adolphus and Charles XII., served to de^
ELEMENTS OF PEUMANEKT FORTIFICATION. 147
Telop in this nation every^ branch of the military art, and
produced a nnmber of distinguished generals and engineers,
who combined with the practice of their profession a study
of its theory. Among the engineers of tnis school, Virgin
holds the first place.
The climate and the nautical habits of the country seem
to have led to land defences analogous to those of ships, as
shown in the uses of casemated batteries in several tiers,
both for sea-coast and inland fortifications. In this school
the bastioned system seems to have been generally adopted
for the enceinte, great attention being paid to covering the
faces of the works from enfilading fire ; in providing case-
mates having reverse views on the besiegers' works ; and
particularly m so arranging the interior dispositions that
«ach part should not only contribute to the defence of the
others, but be capable of an independent resistance. These
dispositions necessarily led to great complication and mul-
tiplicity of works, as shown in the writings of Virgin.
289. French School. What may be termed the charac-
teristics of this school are to be seen rather in the method
of Cormontaigne, and the teachings of the two celebrated
schools of Mezieres and Metz for tne education of engineers,
than in the practice of Vauban, although his authority has
oxercised a preponderating influence throughout Europe,
and is still appealed to, in all great problems of the art, oy
oach side in polemical disputes.
The Frendi have evinced in this, as in all the other arts,
that spirit of systematic combination which forms one of
their most striking national traits. Without excluding an
active defence, the most noted authors of this school have
based their methods upon a combination of elements by
which the besieger's progress can be checked stepby step by
the fire of the works rather than by sorties. Within the
last twenty years all schools have been rapidly tending tow-
ards a common system, which is the logical outcome of the
weapons now available, and the means of resisting their
action.
The freedom of intercourse between nations, no less than
the general and free discussion of all projects by all en-
gineers, leads to the development and adoption of the sim-
plest, cheapest, and most effective methods of defence.
That a universal system is yet adopted can hardly be said,
hut the disposition to depend mainlv upon a defence by de-
tached works, as previously described, is too manifest to
leave room for a reasonable doubt that for many years it will
be the only one employed.
•.48 ELBUEjS'IS op THS.itA.SSST FOBXIflCAIIOir.
n.
FB0GBES8 OF THB ATTAOK SINGE THE INVENTION OF FIBE-
ASMS.
290. The introdaction of cannon, although it led to ira-
portant changes in the measures both of the attack and de-
fence, still did not, for a considerable period, bring about
any very decisive results in the length of sieges. The
means which it afforded the defence of reaching the besieg-
ers at a distance, and of destroying all the methods of ap-
proaching and annoying the place which had been hitherto
used, led to the substitution of the ordinary trendies of the
present day for the wooden galleries and other similar ex-
Eedients for approaching under cover, and to the erection of
atteries at distant points to open breaches in the walls.
Lines of circumvallation and countervallation, which,
formed so prominent a feature previously to this epoch, was
the only one which still kept its place, as it has done to a
greater or less extent to the present day. For the purpose
of effecting an entrance into the place, breaching batteries
were erected opposite the points deemed most favorable*
They were placed either on natural elevations of the ground,
or upon artificial mounds, with the object of striking the
wall to be opened near its foot, and forming a breach of easy
ascent. These batteries were enclosed in works of suflScient
size and strength to hold garrisons to secure them from
sorties. The approaches were made as at present, by zig-
zags along the capitals of the salients to the counterscarp,
where a covered descent was made into the ditch opposite
the breach preparatory to its assault. When the wall was
not exposed to a distant fire, the besiegers were obliged to
carry the covered-way by assault, and establish their breach-
ing batteries on the crest of the glacis.
In carrying forward these works the besiegers were sub-
jected to great losses and delays, owing to the magnitude
and multiplicity of the works they were obliged to com-
plete, to the imperfect character of their artillery and the
faulty position of their batteries, by which they were unable
to keep under the fire of the place ; the want of connection
between the separate approaches, and the consequent ex-
posure of the workmen in the trenches to sorties, the troops
for their support being too distant in the enclosed works in
the rear to give them timely succor ; besides which, as these
ELEMENTS OF PERMANENT FORTIFICATION. 149
enclosed works naturally became the chief objects for the
fire of the besieged, this agglomeration of troops in them
added materially to the losses of the besiegers.
Owing to these imperfections in the measures of attack,
the besieged were able to make a vigorous and prolonged
defence ; and sieges became the most important military
operations of this period, in which captains of the greatest
<5elebrity sought for opportunities of distinction.
291. But little deviation was made in the methods just
described until Vauban appeared upon the scene. Pre-
vious to him, Montluc, a distinguished French general and
■engineer, had introduced short branches of trenches, which
were run out from the angles of the zigzags, to post a few
troops for the immediate protection of the workmen ; but
these were found to be very insufficient in repelling sorties
of any strength.
The event which seems to have had the greatest influence
on the subsequent progress of both the attack and defence
was the memorable siege of Candia, in which volunteers
from all parts of Europe engaged, who, after its close,
disseminated throughout their respective countries the re-
sults of the experience they had there acquired.
Whether the idea of tne parallels, now in use in the
attack, originated there, or witn Vauban, this eminent man
was the first to establish them in a systematic manner, and
to demonstrate by experience their controlling importance
in repressing sorties. The introduction of this important
-element in the attack ; the concentration of the fire of bat-
teries, by giving them enfilading positions ; the invention
of the ricochet, as the most powerful destructive means
against the defences ; the avoidance of open assaults, which,
even when successful, are made at a great sacrifice of life,
preferring to them the less brilliant but slower method of
fikill and industry, by which the blood of the soldier is
spared, and the end more surely attained, — such are the im-
portant services which the attack owes to Vauban, which
gave it its marked superiority over the means of defence.
From the preceding brief summary, it will be seen that
the art of fortification, in its progress, has kept pace with
the measures of the attack ; its successive changes liaving
been brought about by changes either in the arms used by
the assailant, or by the introduction of some new mode of
assault. The same causes must continue to produce the
«ame effects. At no past period has mechanical invention,
in its bearing on the military art, been more active than at
150 ELEXBNTS 07 PEBHANENT VORTIFICATIOK.
the present day. The improvement that has been made in
the range and accaracy of aim of both small-arms and can-
non, the adoption of wrought iron and steel for floating^
batteries and seacoast defences, form the commencement
of another epoch in the engineer's art. The great im^
provementg in cannon give to the assailant a still wider
range in the selection oi positions for his batteries, and thus,
increase the difficulties of the engineer in adapting his.
works to the site, and ingiving adequate shelter to the gar-
rison and armament. Wnilst the defence is to this extent
weakened, the approaches of the besieger are rendered more
perilous and more difficult from the greater range and.
accuracy of small-arms.
The great destruction of life in open assanlts by columns,
exposed within so long a range, gives an additional value to
intrenched fields of battle ; ana we will again see field-
works play the part they did in the defence of Sebastopol
and Plevna, and positions so chosen and fortified that not
only will the assailant be forced to intrench himself to assail
them, but will find the varving phases of his attack met by
corresponding changes in the defensive dispositions.
292. In our own country, from the circumstances of our
position, permanent fortification has met with its most fre-
quent applications in works planned for sea-coast defence,
in which our engineers, without servilely copying any of
the systems in vogue in Europe, have followed the bas^
tioned system, wherever the works were of such an extent
as to admit of its application.
In the larger works erected by them for sea-coast defence^
the water fronts consist of one or more tiers of casemated
batteries, surmounted by one in barbette, whilst the land
fronts consist of the usual rampart and parapet arranged for
open defences.
In the smaller works, which, from the limited extent of
their fronts, did not admit of the adoption of the bastioned
system, flanking dispositions have been made, either by
casemated caponnieres or counterscarp galleries.
Wherever the site was very limited, and a large amount
of fire in a given direction was desirable, as in the cases of
islands (either natural or artificial) to be occupied on the line
of a channel to a roadstead or harbor, the castellated form,
consisting of several tiers of casemates, surmounted by a
barbette battery, has been adopted. These works are gen-
erally so surrounded by water as to be secure from an open
assault, and therefore not requiring fianking dispositions,.
ELEMEIifTS OF PEBMANEKI F0RZIFI0ATI02r» 15L
Where, however, it has been thought necessary to place
these, small bastioned towers have been added at the salient
angles of the work.
Whilst thus adhering to well-settled principles, and fol-
lowing the practice of the best European authorities, our
engineers have contributed their share to the improvement
of the details of the art. The works erected by them are
remarkable for the excellence of the materials employed, the
great skill shown in their construction, and the care with
which every detail was worked out to subserve the object in
view. In these respects, in the inventive genius often dis-
played, and in the adaptation of the plan to the site, it is
not claiming too mucn to say that the works erected by
them are not surpassed, and in some points not equalled, by
any similar works in Europe.
Our engineers have for many years reported that these
works are now entirely inadequate for the defence of our
harbors, and have urgently advocated that they be replaced
at once by those which can resist modem guns as well as
afford emplacements for them.
A popular interest in this subject seems at last to have
been awakened, and it is to be hoped that measures will soon
be taken to provide our harbors and exposed cities with a
suitable defence, by supplying them with fortifications and
guns.
293. The further changes that will be required in fortifi.
cations both for attack and defence, so far as indicated by
the progressive improvements in arms, the increased use of
mortars and the proposed employment of dynamite and
other high explosives in shells, will consist principally in
giving greater strength to parapets and armor, extending
still farther the use of armored constructions and bomb-
proof covers, giving them greater thickness, and in so con-
structing splinter nroof s that they will give protection from
splinters wnose velocity, arising from a high explosive, will
not only give them greater penetration, but, by exceeding
that of the shell from which they come, will take the para-
pets and shelters in reverse.
None of these involve changes in principle nor gr^t
changes in detail, and it is probable that fortifications built
in accordance with methods now adopted and approved will
for many years fulfil all the requirements of an efficient de*
fence.
lld;^ ELEMEJ!(TS OF PEBMAIfElirr FOBXIf ICATIOX.
' CHAPTER Xn.
MODERN OONSTRUOTIONS IN IRON AND STEEL.
294. Iron armor, although advocated by Gen. Paixhan,
and Robert Stevens, of Hoboken, N. J., so early as 1841-42,
received its first test in actual conflict in the attack of the
French and English iron-clad batteries on the Kinburn
forts in the Crimean war in 1855.
The results of this attack led to its further application, in
both France and England, for naval purposes ; but a new
and marked impulse was given by the startling results ob-
tained by its use in the civil war of 1861-65.
295. In the development of armor, wrought-iron natu-
rally took the lead, although experimental constructions in
8teel were made so early as 1857, and in compound plates in
1859.
In its earlier application, both singly and in combination
with iron, steel was found brittle and easily broken up by
the projectiles.
It was not, however, abandoned, but continued experi-
ments were made by English and French manufacturers,
who produced the first successful compound plate in 1867,
and steel plate in 1876.
Meanwhile the manufacturers had improved the quality
and increased the thickness of iron plates, producing them
of guaranteed quality 12 inches thick, and of good quality
up to 22 inches thick which were tested in competition with
fiteel plates of 22 inches in the last-named year.
Competitive trials of compound plates and those made of
steel, each 18.9 inches thick, were also carried on in 1882,
the results of both trials being rather in favor of the steel
plates.
Although some of these proved quite brittle, constant
improvement was made in the manufacture of both com-
pound ana steel plates; the introduction of a small per
cent of nicKel in the latter by Schneider et Cie of Creusot
marking a vejy material advance.
ELEMENTS OF PERMANENT FORTIFICATION. 153
In the United Staces, the recent development of nickel-
steel armor with thf face hardened by the Harvey^ Drocess
has resulted (1892) in the production of jjlates whicn com-
bine toughness and hardness to an extent hitherto unknown,
:and which have a resisting power far greater than any
others made.
Chilled cast-iron was first introduced by Griison, in Ger-
many, in 1868, and has been gaining ground for land de-
fence since that time, its great weight precluding its use on
vessels.
296. Under the impact of proiectiles, wrou^ht-iron, by
means of its ductility and relative lack of tenacityj is pene-
trated by the projectile in a manner similar to that of a
plate of lead by a punch. The injury is, with the best
plates, almost entirely local, and if tfie plate be not pierced
it has nearly as much resisting power as before, in points a
little removed from that struck.
In the immediate vicinity of a previous blow the resist-
ance is diminished, because the metal flows laterally into the
hole produced by the preceding shot.
When the blows are of great energy, and the plate is not
large, or is of poor quality, it is generally destroyed by crack-
ing and breaking.
The best steel projectiles are not materially deformed
even by the thickest iron plates, their energy beinff ex-
pended upon the plate and not upon themselves. Their
penetration can be quite closely calculated.
297. Compound armor behaves quite differently. Its
hard steel face is either very slightly penetrated, and shows
but little injury from the shot, or radial and concentric
cracks of greater or less depth are produced about the point
of impact, and the projectile gets through the armor more
by a process of breaking up and displacing, than by pene-
trating it.
The best steel projectiles are frequently broken up by the
plates.
298. Steel plates with a less per cent of carbon than
the face of the compound plates, behave in a manner inter-
mediate between wrought-iron and compound plates. They
are penetrated more deeply than the compound but less than
the iron plates, while they crack more readily than the iron,
and perhaps less so than the compound, xhe cracks are
almost exclusively radial.
The projectiles may pierce, but more frequently destroy
154 BLBMENT8 OP PERMANENT FORTIFICATION.
the plate by breaking it up. Steel projectiles are usually
broken up, but occasionally rebound after striking, or pass
through unbroken.
299- Chilled iron has an extremely hard surface. No
projectile has yet been made which produces a deep pene-
tration or which has not been broken into pieces when fired
against it. It can hardly be called penetrable. Under re-
peated blows it is split into blocks, along the planes of weak-
ness arising from crystallization, which, by their wedge shape,
frequently resist a number of blows without displacement.
Its protective value is destrojred by the displacement of
the broken parts or by the bodily movement of the shield
under the blows of the projectiles.
Being a cast metal, the shields are easily made of any
thickness required, with surfaces of double curvature of
any desired convexity.
300. In designing armor for land defences, engineers are
not hampered by many considerations which attach to iron-
clad ships. On land the weight of armor, as previously
stated, is sometimes an advants^e. This allows the use of
chilled iron or wrought iron of any desired thickness. The
necessity for covermg a definite height with armor is
obviated by the use of impenetrable substructures of masonry
and earth.
This permits the application of spheroidal and dome-shaped
structures which only admit of oblique impacts and present
the smallest and most indistinct targets to the enemy.
The domes recently introduced by the Gtermans (Schu-
mann's design, Griison's make,) wiU probably be largely
used. They are made in the shape, of spherical segments of
such slight convexity that they aamit of the use of wrought
iron, steel, or compound metal.
301. In the armored forts constructed by England since
1860, as previously stated, iron shields are in some cases
used to cover the gun chambers in granite structures, of
several tiers of fire. These shields are of wrought iron,
usually consisting of three plates each about 5 inches thick
separated by concrete, the embrasures being fitted for the
old type of carriages.
In the large forts on Horse Shoal and No Man's Land at
Portsmouth, circular in form and to mount 49 guns in two
tiers,^ the exterior superstructure is entirely of iron, the
front being of a construction about the same as the shields
above described.
ELEMENTS OF PEBMANENT FOETIFICATIOK, IB^
302. The English engineers have also used wrought iroib
, turrets in their sea-coast works ; the cylindrical type being^^
selected, probably because, at the time they were built, their
armor-maKers had such large experience and skill in build-
ing turrets of this shape, and from the simplicity of their
construction. They are still preferred by some engineers.
303. Plate 18, Fig. 7, is a vertical section of the turret
at the outer end of the pier at Dover. Its interior diameter
is 32 feet, height of armor, 9 feet; thickness of armor^
25 inches, in three plates of 7 inches and two of 2 inches^
The roof, 2 inches thick, is only splinter proof, is partly
grating, and the parts directly over tne guns are removable^
to allow the guns to be taken out or replaced. The weight
of the turret, without guns, is 460 tons. The total weight of
turret, mounting, guns, and carriages, is about 895 tons.
304. The turret itself is carriea on a framed support of
steel turning on a central pivot and carried by 32 rollers
running on a track placed on a masonry substructure.
The central pivot is built up of wrought iron, and is very
strong. It is enclosed in a cylinder of Bessemer steel, and
outside this is a heavy casting nrmly fastened to the masonry^
The turret is turned by a pinion and toothed wheel driven
by steam-power.
The engines and maffazines are about 30 feet below the level
of the guns, and the shell-rooms in the intermediate story.
The turret is armed with two 80-ton muzzle-loading guns,
which are capable of 7° elevation and 2^ depression. They
are drawn back into the turret, and depressed so as to be«
loaded from under the glacis. The glacis is of stone ma-
sonry covered with concrete, finished on the inside vnth a.
ring of plates 5 inches and 3 inches thick, resting on a circle:
of 2-inch plates.
306. Plate 18, Fig. 2, is a section and interior elevation
of an experimental turret for land defences of French con-
struction (Mougin, designer; St. Chamond manufacture.)
Its exterior diameter isl5f feet; height of armor, 4 feet j
thickness, 17.7 inches single plate ; three plates make up the
cylinder.
The top is of flat plates, in two parts, 7 inches thick,
rabbeted and screwed into the vertical plates. The turret
itself rests upon a structure of plates supported in the centre
by a pivot, which serves as the plunger of a hydrauHe
press, oy which the turret and its armament may be raised
for turning, and lowered before firing. Around the exterior
are 10 rollers whose axes are horizontal, running on a cirou-
156 ELBMSKTS OF PEBHAKE^T FOKTIFIOATION.
lar track, and 6 with yertical axes which press against a
vertical rin^. ^ ^
These rollers do not carry the weight of the turret, but
Berve only to balance and direct it, and to relieve the pivot
from shocks. The pivot is 16^ inches thick.
The hydraulic pressure is obtained by a pump worked by
hand. It enables the turret to be raised through considerable
distance to free it if jammed by splinters, and allows it to be
turned with very little friction. The turning is done by a
winch, worked by four men, which turns a pinion engaging
with a toothed wheel attached to the turret platform.
The substructure is of two stories, the lower being used
as a magazine, and for the rotating and hydraulic machinery ;
the second, for working the guns and serving the ammu-
nition. The guns, with their attachments, occupy the turret
itself.
The turret is armed with two 15.5 cm. (6"^ De Bange
guns, with minimum embrasure carriages, admitting of an
elevation of 20° and a depression of 5°. They allow a very
small recoil. The gun and carriage are balanced by a
•counterweight.
306. In pointing, the guns are given the proper elevation
by an arc attached to the slides in the usual manner. For
horizontal direction, a graduated arc is placed under the
turret, provided with a movable index for each gun ; these
are clamped on the arc at points corresponding to the
azimuth of the object aimed at, the sighting being done
through the bore of the gun.
Electric contact points are attached to the turret so as to
touch these indices when the guns have the correct direc-
tion, and firing takes place automatically when the turret is
turned in the right direction up to these contacts.
The glacis armor is made up of four pieces of chilled
<;ast-iron, and is covered with concrete and sand in front.
The weight of the armor is about 73 tons, and that of the
glacis about 68 tons ; total, 141 tons.
The weight of each gun is about 6400 pounds and each
<3arriage about 7500 pounds. Twenty-nine officers and men
are considered necessary to work the turret and guns.
307. Plate 18, Fig. 1, shows a vertical section and in-
terior elevation of an experimental turret of German manu-
facture (Schumann's design, Griison's make).
The top is a spherical segment of 19^ feet greatest diam-
eter, 17 feet radius, and 3 feet rise.
The armor, 8 inches thick, consists of six arched sectors
ELEMENTS OP PERMANENT FORTIFICATION. 167
and a six-sided central plate. The plates are dowelled to-
gether and screwed to a skin of two plates each, about f indi
thick, riveted together.
The embrasure plate, the two next it, and the top plate
are of wrought iron ; the other three of compound armor.
The turret is supported on a construction of plate iron^
carried by a central pivot, and is provided with four rollers
with elastic bearings, under the periphery at 90° apart.
These rollers run on a circular tract attached to the
glacis.
The pivot is about 7 inches in diameter, and rests at the
bottom on a screw which is supported by a wooden block
for elasticity. By the screw the turret may be raised or
lowered to relieve the rollers from a part of the weight.
The substructure and the cupola are arranged in a single
story. Eecesses in the side walls serve for storing ammu-
nition.
The glacis armor consists of eight chilled-iron plates*
Their thickness at top is 14 inches, at bottom 8^ inches.
They are covered on the outside with concrete.
The turret is turned with a winch worked by 4 to 6 men»
It is armed with two 25 cal. 15 cm. (6") Krupp guns
mounted on non-recoil carriages. The chase of the gun in
the embrasure is supported by a trunnion ring, the trun-
nions resting in beds in the armor plates about which the
gun turns for elevation and depression, which are 25° and 6**
respectively. Horizontal direction is given in the usual way
by revolving the turret.
308. The pointing is done by thrusting the head through
a hole in the roof, the sights being fitted to the top ; or by
sighting through a hole m the back of the turret, and then
revolving it 180° ; a graduated circle and pointer pro-
viding for this, as weD as for pointing in a fixed direction
without sighting after the direction is once established.
The elevation is given in the usual way by an arc and
pointer.
The embrasures are made horizontal. The guns and car-
riages are counterpoised by a heavy weight. The recoil is
taken up by arcs attached to the turret.
The weight of the armor plates is about 46 tons, that of
the glacis about 66 tons ; total. 111 tons.
It is stated that the guns and turret may be worked by
14 officers and men. Griison's price for a turret of this type
is about $45,000.
309. This and the French turret previously described.
158 BLEHBKTS OF PEBHANEKT FOBTIFICATION.
^ete Bubjected to competitive trial at Bucharest, in De-
cember, 1885, and January, 1886. Figs. 8, 4, 5 and 6, taken
from photographs, show their appearance after the trial,
during which neither turret was penetrated or disabled.
Fig. 4 shows the back of the French turret after 95 shots
And 66 hits with the 16 cm. gun at 1100 yards range.
Striking energy 1146 foot tons. Fig. 6 shows its embrasure
after 4 shots at 55 yards range with same striking energy.
Fig. 3 shows the back of the G^erman turret after 135
fihots and 71 hits ; and Fig. 5, the front, after 7 hits with the
43ame ranges and guns.
Thev illustrate the behavior of wrought iron under direct
and oblique impact and that of compound plates under
oblique only.
. 310. Plate 19, Fig. 1, is a plan vertical section and in-
terior elevation of a revolving turret caponniere for machine
guns for use at salient and shoulder angles.
It consists of a vaulted roof of wrought iron and a front
ring of chilled iron, pierced for two revolving machine guns,
with a chilled-iron glacis covered with masonry. The thick-
ness of the armor is determined by the character of fire to
ivhich it may be exposed : the root being made bomb-proof,
and both roof and front proof against the oblique blows to
which only they are subject. The dimensions will vary
with the position and armament. A thickness of roof of 4
inches steel or 5J inches wroueht-iron is considered suflS-
cient for very small turrets. This turret is 7 feet interior
diameter without central pivot. It is supported on a system
of rollers and is turned either by a pinion and toothed wheel
or by a lever. Entrance to it is obtained through a postern
under the parapet, as shown. The size here represented,
weighs about 18 tons, and costs at the manufactory about
$6500.
The details and dimensions may be determined from the
:figure.
311. Fig. 2 is a half plan, half horizontal, and a vertical
tsection with interior elevation of a fixed turret caponniere
for use at salient angles. It is somewhat larger than the
revolving turret. It is pierced for two machine guns on
each side, with intermediate loopholes for musketry.
The chilled-iron armor in the vicinity of the machine
guns which look down the ditches is made thicker than on
the side toward the salient, being exposed to more direct
:fire. Entrance to the caponniere is by a postern, as in the
other case. The machine guns have sumcient horizontal
ELBHBirrS 09 PBBMAKEKT POKHFICATIOK. 159
-traverse to sweep the whole width of the ditch, and an
elevation and depression of aboiit 15° and 6° respectively.
312. Fi^. 3 and 4, are sections and interior elevations of
^ disappearing turret for a 87 ram. (1^45) machine gun.
In this construction the roof is made bomb-proof, varying
as previously stated (art. 310) from 4 inches in steel to 5^^
inches in iron. The vertical wall through which the gun
fires is of steel and varies in thickness from i inch to 3
inches in different constructions, depending upon the fire to
^hich it is exposed.
The turret gun and carriage are supported on a framed
«tructure carried by a central pivot which terminates in a
rounded end.
The end of the pivot rests upon and turns in a bearing
which is carried by a stirrup sliding vertically in a slot in a
hollow cylinder, outside of which is a counterweight. The
eounterweight and stirrup are connected by chains passing
over pulleys.
Attached to the bottom of the stirrup and passing down
through the axis of the hollow cylinder is a cnain which is
led to a windlass in the postern.
The windlass is supplied with a crank and brake. When
the brake is loosened, the counterweight falls and raises the
turret to its firing position 16 inches above its lowest posi-
tion. It is lowered by the windlass and chain which draw
down the stirrup and raise the counterweight. When
down, the bomb-proof top rests on the glacis plates.
Three conical rollers attached to the vertical cylinder
serve to centre the turret in its firing position by bearing
against the inner edge of the glacis plates.
The gun and carnage are supported on two levers joined
to the floor of the chamber and the gun-carriage by pin
bearings, so as to allow the gun to be drawn back within
the turret as shown in the dotted lines, or to be thrust out
for firing, in which position it is held by a catch attached
to the armor. Three men are suflScient to work the gun
and turret.
Accurate aim is taken by the motion of the carriage, an
approximate pointing by turning the turret.
313. This turret costs at the factory about $4500, and
the gun about $1250. A similar one for a 53 mm. (2^^
gun costs about $7000, and the gun about $3500.
314. These small disappearing turrets are applicable to
ditch defence, but were also designed for use in the parapet
of the forts for sweeping the ground in front ; the small
160 ELEMENTS OP PERMANENT PORTTFICATION.
calibres for repelliDg assaults and general fire against troops ;
and the larger for retarding the besieger's approaches in
in addition.
Figs. 1, 2, 3, and 4, are from designs of Major Schamann^
Prussian Engineers, and are made by Griison.
The construction of disappearing turrets for 6-inch guns
is now seriously considered in France.
316. The frontispiece, taken from a photograph, of
Battery St. Marie, at Antwerp, shows the use of chilled-iron
armor in casemates. The mortised channel in the edge of
the plates is filled with zinc solder to fasten the plate to its
neignbor. The chill does not extend quite to this channel*
The details of construction are shown by the figure.
APPENDIX I.
PENETRATION OF PEOJECTILES AND THICK-
NESS OF PARAPETS.
FORMULAS.
All formulas have been reduced to the form E = f(t.\ in which E represents the
enercry, in foot-tons per inch of shot's circumference, required to perforate an un-
backed wrought-irou plate whose thickness in inches & t, and f(t.) the particular
function of t.
AUTHOR.
ORIGINAL.
RBDUCBD.
REMARKS.
£:=1.384<a.
(r = G inches.)
Maj. W. H. Noble,
Royal Artillery.
-i/^-
V = velocity on im-
pact in ft. per sec.
W = wt. of shot, lbs.
Sr = accelerating
Maj. W. R. King:,
IT. S. Engineers.
E -a.txlog(6.<-fl).
o = .S9. b = 0.1.
jB = 39 t
Xlog(O.U-f 1).
force of gravity,
r = radius of shot.in.
M. H6lie.
E = 4.40ti
JS: = 4.40<l.
pends on kind of
iron and nature
and form of head
of shot.
Maj W. H. Noble.
Royal Artilleiy.
' \ 2.68*
£:-2.58<»«.
Andrew Noble.
y 8.18*
^=3.18<»».
e
JS:=14 19W.
(r = 6 inches.)
e = total energy on
impact in ft. -tons.
Col. Maitland.
' - 4.r33irr«.
English.
For thick plates.
9 036. ^
" y 0.86-
^=0.86f«o".
Italian.
~ V 4.154*
^=4.154f»«.
Oen. Froloff.
~4irrgr2a40*
d = diam. shot, in.
CaptOrde Browne,
Royal Artillery.
■■♦/!■
-e: = c<».
*c depends for its
value on the ratio
of the thickness of
the plate to diam.
of shot.
Col. M. de Brettes.
Zf= .lOSa 4-1105.
Jg:=^(.013Ge«-f5.87<).
Zf = energy in me-
tre kilogrammes
per pquare cm. of
shot's cross - sec-
tion.
S = thickness of
Adts.
Z/ = 1.431.'ifiS«
-f 85.13645.
2\+4.5412<.>f
Knipp.
Zf = .10S|/J.
^-2V .0135r-
plates in centime-
tres.
D = diam. of shot in
centimetres.
• ^- 0.5 .« .7 .8 .9 1.0 1.1 1.2 1.8 1.4 1.6 1.6 1.7 1.8 1.9 2.0
= 1.900 1.250 1.178 1.125 1.063 1.060 1.022 1.000 0.981 O.QM 0.960 0.938 0.926 0.917 0.908 0.900
Capt. Orde Browne gives the following approximate rule for penetration: "The
penetration of projectiles into wronght-iron is one calibre for every thousand feet
of velocity.'* Very accurate residts are obtained by its use.
11
"^.va^
■'•JSJ!S„
!:• 2 ■• ° ;"■■";; :;;
pS I » ^ S i ^ s ; a n=
|SS S S^ S i : S u i i ; ::
|!" 5 :: : 5 ; 2 5 ■ ; 5 S5
|5S a H 2 a S 5 3 S = 5 SS
|ii ii ss s I s 4 ; I ^ £ s;
,t5 5 :s : ■ 5 5 5 s : ; :;
|» 3 SS S S S S S i ^ S :s
mmii^m^^ii
ipH
:"5"5!5s:;:5
l^i ^ Si i i II i i ^ ^ u:
l^i S S^ I s ; - I ^ I ^ i-
III- 1 11 1 1 i S 1 1 ! fi. II
311 i II II g i 6 6 I E i
|8S « SI S 8 8 S I 3 * s 51
^-: : r-
;::::: T
i!
liiii
iUUi i
APPENDIX.
163
»
H
O
O
o
g
Eh
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g
f
s
a
o
V
G
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^
o
O *• i-
00 •.
*-i o
S 2 I 2 r i ^ ^ S 55 S S a. a>
c csa
« S
3i ^ GO xj«
«o ta G« 99 <o ot
Ti l-" »0 O 00 Ti
rj« 00 ■v rji i?5 »0
s
^1
i3
a
s
04
||S8
S S 8
C* O CD <D
•S »H
O CO
o to to o
8© • • fc;
Q • • O* •••••••••
l- « 'CO
g t^ r. gS S
8
1^
!»' n i^
0^ 0^ 0^ P<
hj J "J ►:;
^ n S s'
BO to to M
•a ^' ^ ^^
.^^ V^ ^irf v^
tf3 to lO to
a> Ok ot ^
• eo • o
00 (^
to «-
*j OS
S3*
• ^
«o«^
a
00
o
a
09
" = 3
•S oS O
SJ*-
o
r/} O
j4
o
I
b
a
o
a
QQ
SQ 3? OQ 95 QQ S?
CO 00 QO 00 oO 00
be
P
n
00
a;
a
5
I
« « « • w 3
3
a
.23
♦ ^
164
APPENDIX.
fThe following thicknesaes of parapets were prescribed for German
fortifications in 1884 :
Thickness.
Kinds or Gun&
Barth.
Masonry.
Wr'ffht-iron
ana Besse-
mer steel.
Snow well
packed.
Bmall-arms and shrapnell. .
Field guna
Feet.
2to 8
10 to 12
17 to 28
88 to 40
Feet.
8
4.6 to 6
Inches.
0.26 to 0.60
4.6 to 6.0
Feet.
6
26
Siege and fortress gruns
Ship'sguns
From experiments made by the Germans it was found that chilled
projectiles penetrate rolled iron from f to } diameters; that small-armft
will penetrate 9" of oak and 10" of fir.
APPENDIX* 165
APPENDIX IL
PEONTIEK AND INTEEIOE FORTIFICATIONS
OF FRANCE, GERMANY, ITALY, AUSTRIA-
HUNGARY, AND RUSSIA IN EUROPE.
FRANCS.
SiNOE the war of 1870-71, the defensive frontier of France
has been remodelled. Many of the old works have been
abandoned, others ameliorated, and new works constructed
in positions of modern strategical importance.
The Belgian Frontier. — This frontier presenting no
natural obstacle, a line of strong works has been constructed,
along it by the amelioration of the old fortifications. De-
tached forts have been placed around the most important
centres, converting them into intrenched camps. Tne first
line of defence consists of four groups of works : Dur^r
Jcerque^ Lille^ Valenciennes^ and Mavheuge. The first
group comprises Dv/nkerque^ Bergues^ and Gravelinea^ and
is being strengthened by the construction of detached forts.
The second, Lille^ which is to have a cordon of forts, Aire
tmd Douai, The third, Valendennes^ which is to have a
cordon of forts (some already constrncted),(7<9/i6Z^, BoucTiain^
and Quesnoy, The fourth, Mauheuge^ which has a cordon
of forts, Landrecies^ Hirson^ and Rocroy, In the second
line, on the river Somme, are the citadel at Amiens^ and
the fortresses of Peronne and Ham / farther south, the
strategic triangle of La Fere^ Laon^ Soissons. This tri-
angle, when the fortifications about these places are com-
pleted, will form an immense intrenched camp ; the base of
armies operating in the north of France. R/ieimB^ further
southj is also an intrenched camp with detached forts.
The German Frontier. — The defensive works along this
frontier are constructed along the river Mouse from Givet to
Toul^ and thence along the Moselle to Belfort, Crvoet is a
^.
166 APPENDIX.
small fortress of minor importance. Mesierea is a fortress
which bars the valley of the Meuse, and occupies an important
railroad junction. Verd/un is an intrenched camp on the
railroad from Metz to Paris. Toul is an intrenched camp
on the railroad from Strasburg to Paris. Verdun and
Toul are connected by a line of forts. Epvaal is an in-
trenched camp on the npper Moselle. Bdforti^ a lar^e in-
trenched camp near the frontier of Switzerland. Epinal
and Belfort are connected by a line of forts. Moiiimedy
and Lcngwy are small fortresses along the railroad from
Luxemburg and Thionville to Mezieres. In the rear of this
frontier line are the intrenched camps of Langres^ Dijon^
and Besangon. The intrenched position, Belfort^ Epmal^
Langres^ Dijon and Besangon^ will form the base of an
army operating from the south alonff this frontier.
T^ iTALii^ AND Swiss rE0NniE8.-The line of the
Alps is defended by numerous small forts in the passes^
supported in the rear by the intrenched camps of Besangon^
Lyons^ and Grenoble.
Spanish Fbontieb. — The line of the Pyrenees is defended
by numerous old works which have been only slightly
enanged since the time of Vauban. The principal ones
are those at Perpianarhy on the Mediterranean side, and
Bayonne on the Atlantic.
Sea-coast Fortifioations. — The principal sea-coast works-
are, on the English Channel : Cherbourg^ St. Ifalo^ and
Havre: on the Atlantic: Bochefortj LorienU Brest^ La
Roclielle^ Oleron^ and Belle Isle; on the Mediterranean:
Toulon and Antihes.
The capital, Paris^ the centre of the defensive system^
has been converted into an immense intrenched camp, hav-
ing a cordon of forts at a distance of about nine miles from
the city.
OSRMAin'.
Nearly all of the existing fortifications of Germany have
either been built or ameliorated since 1870. The intrenched
camps have usually an enceinte surrounded by a line of de-
tached forts at a distance of four to five miles from the
enceinte, and from two to two and a half miles from each
other; between these forts are constructed intermediate
works and batteries.
The Western Frontier. — The main line of defence
against an army coming from the west is along the river
Ittiine ; but beyond this are the intrenched camp of MetZy
and the fortress of Thionville on t/ie MbseUe^ tne tete-^le^
APPENDIX. 167
pant at Saar Louis^ and the old fortress of Bitche* On the
Khine are the fortress and tete-de^ont of Neu Brisach;
the intrenched camp of Strashurg^ the tete-de-pont of
Germeraheim^ the intrenched camp of Mainz^ witn Castd
on the opposite side of the river ; forts Alexander^ Fran-
gois^ and Elireribreitateiny at Cohlenz / the intrenched camp
at Cologne^ with Deutz on the opposite bank, a tete-de-pont
at Dusseldorf^ and two forts protecting the river^rossing at
Wesel. These works control all the principal bridges across
the Ehine from Bale to Wesel. On the east bank of the
Rhine is the intrenched camp of Sastadt.
SouTHEBN Fkontier. — On the Danube are the intrenched
camps of Ulm and Ingolstadt; on the Elbe, the fort of
Konigstem: and in JPrussia, the old fortified places of
Olatz and Ifeisse.
Eastern Feontibr. — This frontier is now protected by
three intrenched camps of the first order. Konigsberg in
eastern Prussia, Thorn on the Vistula, and Posen on the
Warthe. In addition to these are tetes-de-pont at Marien-
hurg^ on the Nogat ; Derschau and Graudenz on the Vis-
tula, and the fortress of Glogau on the Oder.
The capital, Berlin^ is not fortified, but its approaches
are defenaed by the intrenched camp at Magdeburg ; the
old fortress at Torgau^ on the Elbe, and the intienched
camp of Ciisl/rin^ on the Oder. An intrenched camp is
also being constructed at Spandau, in the immediate vicin-
ity of Berlin.
Sea-ooast Foetifioations. — The principal naval port on
the North Sea is that of Wilhelmsfiaven^ and on the Baltic
that of Kiel^ protected by the works of Friedriclisort. In
addition to these, on the North Sea, are the works Cuxhaven
at the mouth of the Elbe, and Geestemunde at the mouth
of the Weser; on the Baltic, Sonderhurg-Dicppdj Stral-
sund; Travemunde^ at the entrance of the port of Lvbeck^
Swinemunde^ at the mouth of the Oder/ KoUberg^ Bamigy
PUlaUy and Memd.
ITALY.
Italy possesses a large number of old fortresses and forti-
fied towns ; the only ones, however, of modern strategical
importance are Alexandria^ Casale^ Bologna^ Capv/iy
LegnanOy Mantua^ Pescliiera^ Placenciay Pizzeghettoney
Verona^ and Borne. Borne has been converted into an in-
trenched camp by the construction of a cordon of forts, and
the fortifications of Capua are being ameliorated, but none
.168 APPEJSDIX.
of the other places can be considered as strong places ac-
cording to the modern idea.
In the last few years much attention has been paid to the
construction of works in the passes of the Alps, to bar the
advance of armies coming from France and Austria. The
Srincipal works of this class are those of Fort Bard^ ExiUe^
^enestrelle^ Venadio, Monte Argetitera, Ventimigliaj on
the Freneh frontier J and liivoli on the Austrian.
Sea-coast Fobtifioations. — Particular attention has been
paid to the reconstruction of the sea-coast fortifications.
Spezia on the Mediterranean, is the principal naval port,
and is being thoroughly fortified ; work is also going on at
Oenoa^ Gaeta^ Porto-Ferraio on the island of Elba ; the
Island of Maddalena^ and Messina^ on the Atlantic;
Aneona Venice^ and Tarento^ on the Adriatic Oivita
Vecchia is also a fortified port.
AUSTRIA-HUNGART.
Austria-Hungary has numerous old fortifications, some of
which have been ameliorated. The great extent of assail-
able frontier making a thorough defence impossible, the
Austrian engineers have limited themselves generally to
the construction of small works, simply intended to im-
pede invasion by obstructing the principal lines of com-
munication leading into the country.
Bavarian Frontier. — There is a fortress at Kufstem on
the Inn ; a fort at Pass Lueg^ south of Salzburg, and an
old intrenched camp at Lim
Saxon and Prussian Fbontiee. — On the Elbe is the
intrenched camp at Theresienstadt^ the old fortifications
of Josephstadt and Koniggratz on the Elbe, and on the
March an intrenched canip at OlmiUz.
KussiAN Frontier. — ^The fortifications consist of in-
trenched camps at OraooWy on the Vistula, and at Prsemyslj
on the San, a tributary of the same. In the second line
is the fortress EperieSy on the Tarcza, a tributary of the
Theiss. The intrenched camp at Przemysly for which
5,500,000 florins have been appropriated, will, when com
pleted, be the strongest fortification of Austria.
Roumanian Frontier. — There are numerous old fortified
places in Transylvania, the principal ones of which are Kron^
stadt and Orsova; in Hungary, on the Danube, is the in-
trenched camp at Komorn^ and fortifications at Peter-
wardein; on the Maros, Ka/rlsbv/pg and Arad; on the
APPEJ^DIX; 169
Brave, jEszek : in Oroatia and Dalmatia, on the Save, Brod^
(jhadieka, and KarUtadt.
The Italian Fbontieb is protected by namerous forts
xionstructed at the passes through the Alps.
Sea-ooast Foetifications. — The principal naval port is
Pola^ on the Adriatic ; fortifications also exist at TriesUj
Fiumey Zara^ SehenicOj Spalatro^ Raguaay lately aban-
doned, and the island of Lisaa.
The capital, Vienna^ is not fortified.
RUSSIA IN SUROPB.
Pbttssian and Austrian Frontiee. — The Polish posses-
sions of Russia are protected by three strongly fortified places :
Novo^Oeorgievak (Modliu), at the junction of the Bug and
Vistula ; Waraaw^ the capital of Poland, and an important
railroad centre on the Vistula ; and Ivcmaorody on the same
river. In rear of this line on the Bug is the strongly fortified
place of Breat-Litovak. In the rear of these frontier for-
tresses are Bjeloatok^ a small fortress at the junction of the
railways from Warsaw to St. Petersburg, and Konigsberg
to Brest-Litovsk ; the intrenched camp of Kovno^ on the
Niemen, the citadel of WUna ; the intrenched camp of
Dwnaherg^ on the Buna / the old fortifications of Smolenaky
on the Dnieper ; the old fortress of Zusk, and the fortifica-
tions in process of construction at BoubnOj on the railways
leading from Poland and Galicia towards Kiev ; and the in-
trenched camp of ICiev on the Dnieper.
Roumanian Frontier. — In the vicinity of this frontier
are the old fortresses of Kamenes-JPodotaky Chotin^ Bend-
£Ty^ and Tiraspol.
Sea-ooast Fortifications. — The principal naval ports on
the Baltic are Ilelaingfora^ protected by the fortifications on
the Sveaborg Islands, and the harbor of Kronstadt ; in
addition to these are the forts Hango^ Ruotainaalm%
Fredrikahamn^ Vihorgy and Baltiachport^ on the Gulf of
Finland; and Riga^ on the Gulf of Eiga, is protected by the
fortifications of Duriamimde.
The principal naval port on the Black Sea is Nikolaifak^
protected by the works of Otachakow and Kinburn; in
addition there are the works of Akkerman, Sebaatopol, and
the fortifications on the Kertch Si/rait.
The Caucasus.— There are numerous old fortifications
between the Black and Caspian Seas. The most important of
these are Kara and Alexcmd/ropol.
170 JkFFESDVL
APPENDIX in.
BOOKS OF EEFEEENOE.
The following list comprises a few of the many valuable
works upon permanent fortifications, and its allied branches-
of Military Engineering.
In the books mentioned will be found references to many
others treating fully upon the different branches of the sab-
ject.
It is not considered necessary to repeat the names of all
the works referred to in the text; nor to enumerate the
writings of Vauban, Cormontaigne,Coehoorn,Montalembert,
Chasseloup, La Chiche, Virgin, Choumara, Dufour, Noizet,.
and other standard authors.
Adams, Oapt. H. M. : Report on Trial of Chilled-iron Armor at
Spezia. Washington, 1886.
Barnard, Gen. J. G.: Dangers and Defences of New York. Few
York, 1859.
Notes on Sea-coast Defence. New York, 1861.
• Wright & Michie: Fabrication of Iron for Defensive Purposes^
with Supplement. Washington, 1871.
Barnes : Submarine Warfare. New York, 1869.
Bixby, Capt. W. H. : Report on Fortification and Ordnance, pub-
lished in ." Engineering News." 1885.
Brialmont: £:tudes sur la Defence des Etats et de la Fortificatloik
Paris, 1863.
Traits de Fortification Polygonal. Paris, 1869.
La Fortification k Fosses sees. Paris, 1872.
Etudes sur la Fortification des Gapitales et PinvestiBsement des-
Camps Retranch^s. Paris, 1873.
La Fortification du Temp Present. Brussels, 1885.
Oraighill: Guns Afloat and Guns Ashore. Essay ons Club Paper,^
No. 6. 1868.
Delafield: Report on Art of War in Europe in 1854-56. Washing-
ton, 1860.
Douglas: Observations on Modem System of Fortification. London^
1859.
fortifications of To-day: Translated from Italian. Washington^
1883.
APPEISTDIX. 171
Fraaer: The Attack of Fortresses of the Future. London, 1877.
Girard: Traits d'application Tactiques de la Fortification. Paris,
1874.
Gillmore: Siege of Fort Pulaski. Washington, 1864.
Goodrich: Beport of British Military and Naval Operations in
Egypt. Washington, 1885.
Giese: Constructions of Iron as applied to Fortification. Washing-
ton, 1867.
Griflfin: Our Sea-coast Defences. New York, 1885.
Humfrey, J. H.: Essay on Modem Systems, etc. London, 1838.
King, Major W. K : Armor Plating for Land Defences. Washing-
ton, 1870.
Torpedoes. Washington, 1866.
Economy in Sea-coast Defences; Essayons Club Paper, No. 19.
1871.
King, J. W. : European Ships of War. Washington, 1877.
Kunka: Die Panzerthurme. Vienna. 1876.
Lendy: A Treatise on Fortification. London, 1862.
Mangin: Memoire sur la Fortification Polygonal; construite in
Allemagne depuis 1815. Paris, 1851.
Die Polygongd Befestigung. Leipzig. 1855.
Maguire: Attack and Defence of Coast Fortifications. New York,
1884.
Prevost, F. : £tudes Historiques sur la Fortification. Paris, 1869.
Prevost de Vemois: De la Fortification depuis Vauban. Paris, 1861»
Katheau: Traits de Fortification. Paris, 1866.
Attaque et Defence des Places Fortes. Paris, 1877.
Beport of Board on Fortification or other Defences. Washington^
1886.
Of Select Committee on Ordnance and War Ships. Washing-
ton, 1886.
With Reference to Progress in Construction of Fortifications for
Dockyards, etc. London, 1867.
Of Committee on Gibraltar Shield. London, 1868.
Upon Practice in Europe with Heavy Guns. Prof. Paper,.
Corps of Engineers, No. 25. Washington, 1883.
Record of Experimental Firing at Fort Monroe. Washington, 1870*
Schueler Leitfaden flir den Unterricht in der Befestigung, etc.
Berlin, 1884.
Schtitz, J. von: Experiences de Bucharest. Brussels, 1886.
Sellon, Maurice de: Various Writings. Paris, 1845 et seq,
Sleeman: Torpedoes and Torpedo Warfare. Portsmouth, England^
1880.
Stotherd: Notes on Torpedoes Offensive and Defensive (Reprint)*
Washington, 1873.
Totten: Casemate Embrasures. Washington, 1857.
Tripier: La Fortification de son Histoire. Paris, 1886.
T^not: Paris et ses Fortifications. Paris, 1880,
Very: The Navies of the World. Washington, 1880.
The Development of Armor for Naval Use. Annapolis, 1888.
VioUet-le-duo : Annals of a Fortress. Boston, 1876.
Von Schelliha: Treatise on Coast Defence, etc. London, 1868.
Woolwich: Text Book on Fortification. London, 1877.
Zastrow: Histoire de la Fortification Permanente. Paris, 1866.
Plate 18.
B^2.
* '• •
' • »
• c
Plate 19.
•- r
SHORT-TITLE CATALOGUE
OF THB
PUBLICATIONS
ov
JOHN WILEY & SONS,
New York.
Lokdok: chapman & HALL, Limitbd.
ARRANGED UNDER SUBJECTS.
Descriptive circulars sent on application. Books marked with an asterisk (*) are sold
at net prices only. All books are bound in cloth unless otherwise stated.
AGRICULTURE— HORTICULTURE— FORESTRY.
Armsby's Manual of Cattle-feeding i2mo, Sx 75
Principles of Animal Nutrition 8vo> 4 00
Budd and Hansen's American Horticultural Manual:
Part I. Propaffation, Culture, and Improvement 12 mo, i 50
Part IL Systematic Pomology i2mo, i 50
Elliott's Engineering for Land Drainage i2mo, i 50
Practical Farm Drainage z^mo, i 00
Craves's Forest Mensuration 8vo, 4 00
Green's Principles of American Forestry i2mo, i 50
Grotenfeh's Principles of Modern Dairy Practice. (WolL) x2mo, a 00
* Herrick's Denatured or Industrial Alcohol 8vo, 4 00
*Kemp and Waugh's Landscape Gardening. (New Edition, Rewritten. In
Preparation).
* McKay and Larsen's Principles and Practice of Butter-making 8vo, x 50
Maynard's Landscape Gardening as Applied to Home Decoration i2mo, x 50
<}uaintance and Scott's Insects and Diseases of Fruits. (In Preparation).
Sanderson's Insects Injurious to Staple Crops lamo, i 50
♦Schwarz'sLongleaf Pine in Virgin Forests xamo, i 25
Stockbridge's Rocks and Soils. 8vo, a 50
Winton's Microscopy of Vegetable Foods 8vo, 7 so
Woll's Handbook for Farmers and Dairymen i6mo, z 50
ARCHITECTURE.
Baldwin's Steam Heating for Buildings x2mo, a 5 >
Berg's Buildings and Structures of American Railroads 4to, 5 00
Birkmire's Architecttiral Iron and SteeL 8vo, 3 50
Compound Riveted Girders as Applied in Buildings 8vo, 2 00
Planning and Construction of American Theatres ^ 8vo, 3 00
Planning and Construction of High Office Buildings 8vo, 3 50
Skeleton Construction in Buildings 8vo, 3 00
Briggs's Modem American School Buildings 8vo, 4 00
Byrne's Inspection of Material and Wormanship Employed in Construction.
i6mo, 3 00
Carilenter's Heating and Ventilating of Buildings 8vo, 4 00
1
* Corthell't Allowable Pressure on Deep Foundations.;. lamo, z 25
Freitac's Architectural Encineerinc 8vo 3 50
Fireproofinc of Steel Buildings. 8vo, 2 50
French and Ives's Sto-eotomy 8vo, 2 50
Gerhard's Guide to Sanitary House-Inspection. zCimo, z 00
* Modern Baths and Bath Houses 8vo, 3 00
Sanitation of Public Buildings i2mo^ z 50
Theatre Fires and Panics z2mo, z 50
HoUey and Ladd's Analysis of Mixed Paints, Color Pigments, and Varnishes
Large z2mo, 2 50
Johnson's Statics by Algebraic and Graphic Methods 8vo, 2 00
Ktilaway'8 Bow to Lay Oat Suburban Home Gnmnda Svo. 2 00
Kidder's Architects' and Builders' Pocket-book z6mo, mor., 5 00
Maire's Modem Pigments and their Vehicles Z2mo, a 00
Merrill's Non-metallic Minerals: Their Occurrence and Uses 8vo, 4 00
Stones for Building and Decoration 8vo, 5 00
Monckton's Stair-building 4to, 4 00
Patton's Practical Treatise on Foundations 8vo, 5 00
Peabody's Ifaval Architecture 8vo, 7 50
Rice's Concrete-block Manufacture Svo. 2 00
Richey's Handbook for Superintendents of Construction z6mo, mor., 4 00
* Building Mechanics' Ready Reference Book:
* Building Foreman's Pocket Book and Ready Reference. (In
Preparation).
* Carpenters' and Woodworkers' Edition z6mo, mor. z 50
* Cement Workers and Plasterer's Edition z6mo, mor. z 50
* Plumbers', Steam-Fitters', and Tinners' Edition z6mo, mor. z 50
* Stone- and Brick-masons' Edition z6mo, mor. z 50
Sabin's Industrial and Artistic Technology of Paints and Varnish 8vo, 3 00
Siebert and Biggin's Modem Stone-cutting and Masonry 8vo, z 50
Snow's Principal Species of Wood 8vo, 3 50
Towne's Locks and Builders' Hardware z8mo, mor. 3 00
Waifs Engineering and Architectural Jurisprudence 8vo, 6 00
Sheep, 6 50
Law of Contracts 8vo, 3 00
Law of Operations Preliminary to Construction in Engineering and Archi-
tecture 8vo, 5 00
Sheep, 5 50
Wilson's Air Conditioning z2mo, z 50
Worcester and Atkinson's Small Hospitals, Establishment and Maintenance,
Suggestions for Hospital Architecture, with Plans for a Small Hospital.
Z2mo> z 35
ARMY AND NAVY.
Bemadou's Smokeless Powder, Ifltro-cellulose, and the Theory of the Cellulose
Molecule : Z2mo, 2 50
Chase's Art of Pattern Making Z2mo, 2 50
Screw Propellers and Marine Propulsion 8vo, 3 00
Cloke's Gunner's Examiner 8vo, z 50
Craig's Azimuth 4to, 3 50
Crehore and Squier's Polarizing Photo-chronograph 8vo, 3 00
* Davis's Elements of Law .8vo, 2 50
* Treatise on the Military Law of United States 8vo, 7 00
Sheep, 7 50
De Brack's Cavalry Outpost Duties. (Carr.) :24mo, mor. 2 00
* Dudley's Military Law and the Procedure of Court8-ml^:tial. . . Large z2mo, a 50
Durand's Resistance and Propulsion of Ships. Svo, 5 00
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* Dyer's Handbook of Light Artillery i3mo»
Eissler's Modem High Explosives 8vo,
* Fiebeger's Text-book on Field Fortification Large i2mo,
Hamilton and Bond's The Gunner's Catechism *. x8mo,
* Hoff's Elementary Naval Tactics 8vo,
Ingalls's Handbook of Problems in Direct Fire 8vo,
* Lissak's Ordnance and Gunnery 8vo,
* Ludlow's Logarithmic and Trigonometric Tables 8vo,
* Lyons's Treatise on Electromagnetic Phenomena. Vols. L and II. .8vo, each,
* Mahan's Permanent Fortifications. (Mercur.) 8vo, half mor.
Manual for Courts-martial x6mo, mor.
* Mercur's Attack of Fortified Places x2mo,
* Elements of the Art of War 8vo,
Metcalf's Cost of Manufactures — And the Administration of Workshops. .8vo,
* Ordnance and Gunnery. 2 vols Text x3mo, Plates atlas form
Nixon's Adjutants' ManuaL 34mo»
Peabody's Naval Architecture 8vo,
* Phelps's Practical Marine Surveying ^ 8vo,
Powell's Army Ofilcer's Examiner i2mo,
Sharpe's Art of Subsisting Armies in War i8mo, mor.
* Tupes and Poole's Manual of Bayonet Exercises and Musketry Fencing.
34mo, leather,
* Weaver's Military Explosives 8vo,
WoodhuU's Notes on Military Hygiene x6mo,
ASSAYING,
Betts's Lead Refining by Electrolysis 8vo, 4 00
Fletcher's Practical Instructions in Quantitative Assaying with the Blowpipe.
i6mo, mor. i 50
Furman's Manual of Practical Assaying 8vo, 3 00
Lodge's Notes on Assaying and Metallurgical Laboratory Experiments. . . .8vo, 3 00
Low's Technical Methods of Ore Analysis 8vo, 3 00
Miller's Cyanide Process i2mo, i 00
Manual of Assaying X2mo, i 00
Minet's Production of Aluminum and its Industrial Use. (Waldo.) x2mo, 2 50
O'Driscoll's Notes on the Treatment of Gold Ores 8vo, 2 00
Ricketts and Miller's Notes on Assaying 8vo, 3 00
Robine and Lenglen's Cyanide Industry. (Le Clerc.) 8vo, 4 00
Ulke's Modern Electrolytic Copper Refining 8vo, 3 00
Wilson's Chlorination Process i2mo, i 50
Cyanide Processes ismo, z 50
ASTRONOMY.
Comstock's Field Astronomy for Engineers 8vo, 3 50
Craig's Azimuth 4to, 3 50
Crandall's Text-book on Geodesy and Least Squares 8vo, 3 00
Doolittle's Treatise on Practical Astronomy 8vo, 4 00
Gore's Elements of Geodesy 8vo, 2 50
Hayford's Text-book of Geodetic Astronomy 8vo, 3 00
Merriman's Elements of Precise Surveying and Geodesy 8vd, 3 50
* Michie and Harlow's Practical Astronomy 8vo, 3 00
Rust's Ex-meridian Altitude, Azimuth and Star-Finding Tables. (In Press.)
* White's Elements of Theoretical and Descriptive Astronomy i3mo, 3 00
8
CHEMISTRY.
•
Abderhalden's Physiological Chemistry in Thirty Lectures. ( Hall and Defren).
(In Press.)
* Aben's Theory of Electrolytic Dissociation, (von Ende.) lamo,
Adriance's Laboratory Calculations and Specific Gravity Tables. iamo»
Alezeyeff's General Principles of Organic Syntheses. (Matthews.) 8vo,
Allen's Tables for Iron Analysis 8vo,
Arnold's Compendium of Chemistry. (Mandel.) Large x2mo.
Association of State and Rational Food and Dairy Departments, Hartford
Meeting, 1906 8vo,
Jamestown Meeting. 1907 Bvo,
Austen's Rotes for Chemical Students lamo,
Baskerville's Chemical Elements. (In Preparation).
Bemadou's Smokeless Powder. — Ritro-cellulose, and Theory of the Cellulose
Molecule xamo,
* Blanchard's Synthetic Inorganic Chemistry. zamo»
* Browning's Introduction to the Rarer Elements Svo,
Brush and Penfield's Manual of Determinative Mineralogy 8vo,
* Claassen's Beet-sugar Manufacture. (Hall and Rolfe.) 8vo,
Classen's Quantitative Chemical Analysis by Electrolysis. (Boltwood.). .8vo,
Cohn's Indicators and Test-papers. lamo.
Tests and Reagents 8vo,
* Danneel's Electrochemistry. (Merriam.) lamo,
Duhem's Thermodynamics and Chemistry. (Burgess.) 8vo,
Eakle's Mineral Tables for the Determination of Minerals by their Physical
Properties 8vo,
Eissler's Modem High Explosives 8vo,
Effront's Enz3rmes and their Applications. (Prescott.) 8vo,
Erdmann's Introduction to Chemical Preparations. (Dunlap.) lamo,
* Fischer's Physiology of Alimentation Large l2mo,
Fletcher's Practical Instructions in Quantitative Atoaying with the Blowpipe.
lamo, mor.
Fowler's Sewage Works Analyses lamo,
Fresenius's Manual of Qualitative Chemical Analysis. (Wells.) 8vo,
Manual of Qualitative Chemical Analysis. Part I. Descriptive. (Wells.) 8vo,
Quantitative Chemical Analysis. (Cohn.) 2 vols Svo,
When Sold Separately, VoL I, $6. VoL H, $8.
Fuertes's Water and Public Health xamo,
Furman's Blanual of Practical Assaying 8vo,
* Getman's Exercises in Physical Chemistry xamo.
Gill's Gas and Fuel Analysis for Engineers lamo,
* Gooch and Browning'g Outlines of Qualitative Chemical Analysis.
Large xamo,
Grotenfelt's Principles of Modem Dairy Practice. (WolL) xamo,
Groth's Introduction to Chemical Crystallography (Marshall) xamo,
Hammarsten's Text-book of Physiological Chemistry. (MandeL) 8vo,
Hanausek's Microscopy of Technical Products. (Wlnton.) 8vo,
* Haskins and Madeod's Organic Chemistry xamo.
Helm's Principles of Mathematical Chemistry. (Morgan.) xamo,
Hering's Ready Reference Tables (Conversion Factors) x6mo, mor.
* Herrick's Denatured or Industrial Alcohol 8vo,
Hinds's Inorganic Chemistry 8vo,
* Laboratory Manual for Students xamo,
* HoUeman's Laboratory Manual of Organic Chemistry for Beginners.
(Walker.) xamo.
Text-book of Inorganic Chemistry. (Cooper.) 8vo,
Text-book of Organic Chemistry. (Walker and Mott.) 8vo,
VtiOey and Ladd's Analysis of Mixed Paints, Color Pigments, and Varnishes.
Large xamo a $0
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Hopkins's Oil-chemists' Handbook Svo, 3 00
Iddings's Rock Minefals 8vo, 5 00
Jackson's Directions for Laboratory Work in Physiological Chemistry. .8vo, i 35
johannsen's Detennination of Rock-forming Minerals in Thin Sections.. .8vo, 4 00
j!Ceep*s Cast Iron 8vo, 2 50
■ Ladd's Manual of Quantitative Chemical Analysis lamo, i 00
i«andauer's Spectrum Analsrsis. (Tingle.) .8vo, 3 00
* ifAngwurtliy and Austen's Occurrence of Aluminium in Vegetable Pxod-
ucts, Animal Products, and Natural Waters 8vo, 2 00
Lassar-Cohn's Application of Some General Reactions to Investigations in
Organic Chemistry. (Tingle.) lamo, i 00
Leach's Inspection and Analysis of Food with Special Reference to State
Control 8vo, 7 50
Lob's Electrochemistry of Organic Compounds. (Lorenz.) 8vo, 3 00
Lodge's Notes on Assaying and Metallurgical Laboratory Experiments. .. .8vo, 3 00
Low's Technical Method of Ore Analysis 8vo, 3 00
Lunge's Techno-chemical Analysis. (Cohn.). i2mo z 00
* McKay and Larsen's Principles and Practice of Butter-making 8vo, i 50
Blaire's Modem Pigments and their Vehicles i2mo, 2 00
Mandel's Handbook for Bio-chemical Laboratory i2mo, i 50
* Martin's Laboratory Guide to' Qualitative Analysis with the Blowpipe . . i2mo, 60
Mason's Examination of Water. (Chemical and Bacteriological.). . ..i2mo, i 25
Water-supply. (Considered Principally from a Sanitary Standpoint.)
8vo, 4 00
Matthews's The Textile Fibres. 2d Edition, Rewritten Svo, 4 00
Meyer's Determination of Radicles in Carbon Compounds. (Tingle.). . i2mo, i 00
Miller's Cyanide Process i2mo, i 00
Manual of Assaying i2mo, i 00
Minet's Production of Aluminum and its Industrial Use. (Waldo.) . . . . x2mo, 2 50
Mixter's Elementary Text-book of Chemistry i2mo, i 50
Morgan's Elements of Phjrsical Chemistry i2mo, 3 co
Outline of the Theory of Solutions and its Results. i2mo, i 00
* Physical Chemistry for Electrical Engineers i2mo» i 50
Morse's Calculations used in Cane-sugar Factories z6mo, mor. i 50
* Muir's History of Chemical Theories and Laws 8vo, 4 00
Mulliken's General Method for the Identification of Pure Organic Compounds.
VoL I Large Svo, 5 00
O'Driscoll's Notes on the Treatment of Gold Ores Svo, 2 00
Ostwald's Conversations on Chemistry. Part One. (Ramsey.) i2mo, i 50
" " " " ' Part Two. (TumbulL) i2mo, 200
* Palmer's Practical Test Book of Chemistry i2mo, i 00
* Pauli's Physical Chemistry in the Service of Medicine. (Fischer.) . . . . i2mo, i 25
* Penfield's Notes on Determinative Mineralogy and Record of Mineral Tests.
, dvo, paper, 50
Tables of Minerals, Including the Use of Minerals and Statistics of
Domestic Production Svo, i 00
Pictet's Alkaloids and their Chemical Constitution. (Biddle.) 870, 5 00
Poole's Calorific Power of Fuels Svo, 3 00
Prescott and Winslow's Elements of Water Bacteriology, with Special Refer-
ence to Sanitary Water Analysis. z2mo, i 50
* Reisig's Guide to Piece-dyeing Svo, 25 00
Richards and Woodman's Air, Water, and Food from a Sanitary Standpoint. .8 vo , 2 00
Ricketts and Miller's Notes on Assaying , 8vo, 3 00
Rideal's Disinfection and the Preservation of Food.. Svo, 4 00
Sewage and the Bacterial Purification of Sewage Svo, 4 00
Riggs's Elementary Manual for the Chemical Laboratory Svo, i 25
Robine and Lenglen's Cyanide Industry. (Le Clerc.) Svo, 4 00
Ruddiman's Incompatibilities in. Prescriptions -. Svo, 2 00
Whys in Pharmacy j2mo, 1 00
5
Ruer's Elements of Metallography. (Mathewson). CIn Preparation.)
Sabin's Industrial and Artistic Technology of Paints and Varnish 8vo,
Salkowski's Physiological and Pathological Chemistry. (OrndorfiF.) 8vo,
Schimpf's Essentials of Volumetric Analysis xamo,
* Qualitative Chemical Analysis 8vo,
Text-book of Volumetric Analysis i2mo,
Smith's Lecture Notes on Chemistry for Dental Students 8vo,
Spencer's Handbook for Cane Sugar Manufacturers i6mo, mor.
Handbook for Chemists of Beet-sugar Houses x6mo, mor.
Stockbridge's Rocks and Soils 8vo,
* Tillman's Descriptive General Chemistry 8vo,
** Elementary Lessons in Heat 8vo,
Treadwell's Qualitative Analysis. (HalL) 8vo,
Quantitative Analysis. (Hall.) 8vo,
Tumeaure and Russell's Public Water-supplies 8vo,
Van Deventer's Physical Chemistry for Beginners. (Boltwood.) x2mo,
Venable's Methods and Devices for Bacterial Treatment of Sewage 8vo,
Ward and Whipple's Freshwater Biology. (In Press.)
Ware's Beet-sugar Manufacture and Refining. Vol. I Small 8vo,
Vol.11 SmallSvo.
Washington's Manual of the Chemical Analysis of Rocks 8vo,
* Weaver's Military Explosives 8vo,
Wells's Laboratory Guide in Qualitative Chemical Analysis 8vo,
Short Course in Inorganic Qualitative Chemical Analysis for Engineering
Students i2mo.
Text-book of Chemical Arithmetic i2mo,
Whipple's Microscopy of Drinking-water 8vo,
Wilson's Chlorination Process . i2mo
Cyanide Processes i2mo
Winton's Microscopy of Vegetable Foods 8vo
CIVIL ENGINEERING.
BRIDGES AND ROOFS. HYDRAULICS. MATERIALS OF ENGINEER-
ING. RAILWAY ENGINEERING.
Baker's Engineers' Surveying Instruments i2mo, 3 00
Bixby's Graphical Computing Table Paper 19^ X 24i inches. 25
Breed and Hosmer's Principles and Practice of Surveying 8vo, 3 00
* Burr's Ancient and Modern Engineering and the Isthmian Canal 8vo, 3 50
Comstock's Field Astronomy for Engineers 8vo, 2 50
* CoTtbell's AUowable Pressures on Deep Foundations i2mo, i 25
Crandall's Text-book on Geodesy and Least Squares 8vo, 3 00
-Davis's Elevation and Stadia Tables 8vo» i 00
JBlliott's Engineering for Land Drainage i2mo, i 50
Practical Farm Drainage i2mo, i 00
*Fiebeger's Treatise on Civil Engineering 8vo, 5 00
Flemer's Phototopographic Methods and Instruments 8vo, 5 00
Folwell's Sewerage. (Designing and Maintenance.) 8vo, 3 00
Freitag's Architectural Engineering 8vo, 3 50
French and Ives's Stereotomy 8vo, 2 50
Goodhue's Municipal Improvements i2mo, 1 50
Gore's Elements of Geodesy 8vo, 2 50
* Hanch and Rice's Tables of Quantities for Prdiminaiy Estimates l2mo. i 25
Hayford's Text-book of Geodetic Astronomy 8vo, 3 00
Bering's Ready Reference Tables (Conversion Factors) i6mo, mor. 2 50
Howe's Retaining Walls for Earth i2mo, i 35
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* Ives's Adjustments of the Engineer's Transit and Level i6mo, Bds. . 25
Ives and Hilts's Problems in Surveying i6mo, mor. z 50
Johnson's (J. B.) Theory and Practice of Surveying Small 8vo, 4 00
Johnson's (L. J.) Statics by Algebraic and Graphic Methods 8vo, 2 oa
Kinnicutt, Winslow and Pratt's Purification of Sewage. (In Preparation).
Laplace's Philosophical Essay on Probabilities. (Truscott and Emory.)
i2mo, 2 00
Mahan's Descriptive Geometry 8vo, i 50
Treatise on Civil Engineering. (1873.) (Wood.) 8vo, 5 00
Merriman's Elements of Precise Surveying and Geodesy 8vo» 2 50
Merriman and Brooks's Handbook for Surveyors x6mo, mor. 2 00
Morrison's Elements of Highway Engineering. (In Press.)
Nugent's Plane Surveying 8vo, 3 so
Ogden's Sewer Design i2mo, 2 00
Parsons's Disposal of Municipal Refuse 8vo, 2 00
Patton's Treatise on Civil Engineering 8vo, half leather, 7 50
Reed's Topographical Drawing and Sketching 4to, 5 oa
Rideal's Sewage and the Bacterial Purification of Sewage 8vo, 4 oo
Riemer's Shaft-sinking under Difficult Conditions. (Coming and Peele.) . .8vo, 3 06
Siebert and Biggin's Modern Stone-cutting and Masonry 8vo, i 50
Smith's Manual of Topographical Drawing. (McMillan.). 8vo, 2 50
Soper's Air and Ventilation of Subways. (In Press.)
Tracy's Plane surveying. ' l6mo. mor. 3 00
* Trautwine's CivM Engineer's Pocket-book i6mo, mor. 5 00
Venable's Garbage Crematories in America 8vo, 2 00
Methods and Devices for Bacterial Treatment of Sewage 8vo, 3 00
Wait's Engineering and Architectural Jurisprudence 8vo, 6 oo>
Sheep, 6 50
Law of Contracts 8vo, 3 oa
Law of Operations Preliminary to Construction in Engineering and Archi-
tecture 8vo, 5 00
Sheep, 5 50
Warren's Stereotomy — Problems in Stone-cutting 8vo, 2 5a
* Waterbury's Vest-Pocket Hand-book of Mathematics for Engineers.
2iX5i inches, mor. i 00
Webb's Problems in the Use and Adjustment of Engineering Instruments.
i6mo, mor. x 25
Wilson's Topographic Surveying 8vo, 3 so
BRIDGES AND ROOFS.
Boiler's Practical Treatise on the Construction of Iron Highway Bridges . . 8vo, a 00
Burr and Falk's Design and Construction of Metallic Bridges 8vo^ 5 00
Influence Lines for Bridge and Roof Computations 8vo, 3 oa
Dtt Bois's Mechanics of Engineering. Vol H Small 4to, 10 oa
Foster's Treatise on Wooden Trestle Bridges 4to, 5 oa
Fowler's Ordinary Foundations 8vo, 3 5a
French and Ives's Stereotomy 8vo, 2 50
Greene's Arches in Wood, Iron, and Stone 8vo, 2 5a
Bridge Trusses 8vo, 2 5a
Roof Trusses 8vo, i 25
Grimm's Secondary Stresses in Bridge Trussee 8vo, 2 50
Heller's Stresses in Structures and the Accompany in ^ Deformations. 8vo,
Howe's Design of Simple Roof-trusses in Wood and SteeL 8vo, 2 oa
Symmetrical Masonry Arches 8vo, 2 5a
Treatise on Arches 8vo, 4 oa
Johnson, Bryan, and Turneaure's Theory and Practice in the Designing of
Modem Framed Structures Small 4to, zo 00
7
Merriman and Jacobjr's Text-book on Roofs and Bridges :
Part I. . Stresses in Simple Trusses 8vo, 2 50
Part n. Graphic Statics 8vo, a 50
Part in. Bridge Design 8vo, 3 50
Part IV. Higher Structures 8vo, 2 50
Morison's Memphis Bridge Oblong 4to, 10 00
Sondericker's Graphic Statics, with Applications to Trusses, Beams, and Arches.
8vo, 2 00
Waddell's De Pontibus, Pocket-book for Bridge Engineers i6mo, mor, 2 00
* Specifications for Steel Bridges i2mo, 50
Waddell and Harrington's Bridge Engineering. (In Preparation.)
Wright's Designing of Draw-spans. Two parts in one volume 8to, 3 50
HYDRAULICS.
Barnes's Ice Formation 8vo, 3 00
Bazin's Experiments upon the Contraction of the Liquid Vein Issuing from
an Orifice. (Trautwine.) 8vo, 2 00
Bovey's Treatise on Hydraulics 8vo, 5 00
Church's Diagrams of Mean Velocity of Water in Open Channels.
Oblong 4to, paper, i 50
Hydraulic Motors 8vo, 3 00
Mechanics of Engineering .8vo, 6 00
Coffin's Graphical Solution of Hydraulic Problems i6mo, morocco, 2 50
Flather's Dynamometers, and the Meastirement of Power i2mo, 3 00
Folwell's Water-supply Engineering 8vo, 4 00
Frizell's Water-power 8vo, 5 00
Fuertes's Water and Public Health lamo, i 50
Water-filtration Works i2mo, 2 50
Ganguillet and Kutter's General Formula for the Uniform Flow of Water in
Rivers and Other Channels. (Hering and Trautwine.) 8vo, 4 00
Hazen's Clean Water and How to Get It Large i2mo, x So
Filtration of Public Water-supplies 8vo, 3 00
Hazlehurst's Towers and Tanks for Water-works 8vo, 2 50
Herschel's 1x5 Experiments on the Carrying Capacity of Large, Riveted, Metal
Conduits 8vo, 2 00
Hoyt and Grover's River Discharge 8vo, 2 00
Hubbard and KierBted's Water-works Management and Maintenance 8vo, 4 00
* Lyndon's Development and Electrical Distribution of Water Power 8vo, 3 00
Mason'^ Water-supply. (Considered Principally from a Sanitary Standpoint)
8vo, 4 00
Merriman's Treatise on Hydraulics 8vo, 5 00
* Michie's Elements of Analytical Mechanics 8vo, 4 00
Molitor's Hydraulics of Rivers, Weirs and Sluices. (In Press.)
Schuyler's Reservoirs for Irrigation, Water-power, and Domestic Water-
supply Large 8vo, 5 00
* Thomas and Watt's Improvement of Rivers 4to, 6 00
Tumeaure and Russell's Public Water-supplies 8vo, 5 00
Wegmann's Design and Construction of Dams. 5th Ed., enlarged 4to, 6 00
Water-supply of the City of New York from 1658 to 1895 4to, 10 00
Whipple's Value of Pure Water Large i2mo, x 00
Williams and Hazen's Hydraulic Tables 8vo, i 50
Wilson's Irrigation Engineering Small 8vo, 4 00
Wolff's Windmill as a Prime Mover 8vo, 3 00
Wood's Elements of Analytical Mechanics. 8vo, 3 00
Tuxhines 8vo, 2 50
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MATERIALS OF ENGINEERING.
Baker's Roads and Pavements 8yo,
Treatise on llasonry Construction 8vo»
Birkmire'ri Architectural Iron and Steel 8vo»
Compound Riveted Girders as Applied in Buildings 8vo,
Black's United States Public Works Oblong 4to,
Bleininger's Manufacture of Hydraulic Cement. (In Preparation.)
'*' Bovey's Strength of Materials and Theory of Structures 8vo»
Burr's Elasticity and Resistance of the Materials of Engineering 8vo,
Birme's Highway Construction 8vo,
Inspection of the Materials and Workmanship Employed in Construction.
z6mo,
Church's Mechanics of Engineering 8vo,
Dtt Bois's Mechanics of Engineering.
Vol. I. Kinematics, Statics, Kinetics Small 4to, 7 50
VoL n. The Stresses in Framed Structures, Strength of Materials and
Theory of Flexures. Small 4to, 10 00
^Eckel's Cements, Limes, and Plasters 8vo, 6 00
Stone and Clay Products used in Engineering. (In Preparation.)
Fowler's Ordinary Foundations. 8vo, 3 50
Graves's Forest Mensuration 8vo, 4 00
Green's Principles of American Forestry i2mo, i ^to
* Greene's Structural Mechanics 8vo, 3 50
HoUy and Land's Analysis of Mixed Paints, Color Pigments and Varnishes
Large T2mo, 3 50
Johnson's Materiab of Construction. Large 8vo, 6 00
Keep's Cast Iron 8vo, 2 50
Kidder's Architects and Builders' Pocket-book x6mo, 5 00
Lanza's Applied Mechanics 8vo, 7 50
Maire's Modern Pigments and their Vehicles Z2mo, 2 00
Martens's Handbook on Testing Materials. (Henning.) 2 vob 8vo, 7 50
Maurer's Technical Mechanics. 8vo, 4 00
Merrill's Stones for Building and Decoration. 8vo, 5 00
Merriman's Mechanics of Materials 8vo, 5 00
* Strength of Materials i2mo, x 00
Metcalf's Steel. A Manual for Steel-users i2mo, 2 00
Patton's Practical Treatise on Foundations 8vo, 5 00
Rice's Concrete Block Manufacture 8vo, 2 00
Richardson's Modem Asphalt Pavements 8vo, 3 00
Richey's Handbook for Superintendents of Co "tr cion i6mo, mor., 400
* Ries's Clays: Their Occurrence, Properties, ana Jses 8vo, 5 00
Sabin's Industrial and Artistic Technology of Paints arl Varnish 8vo, 3 00
♦Schwarz'sLongleafPinein Virgin Forest ., lamo, i 25
Snow's Principal Species of Wood 8vo, 3 5o
Spalding's Hydraulic Cement i2mo, 2 00
Text-book on Roads and Pavements z2mo, 2 00
Taylor and Thompson's Treatise on Concrete, Plain and Reinforced.. 8vo, 5 00
Thurston's Materials of Engineering. In Three Parts 8vo, 8 00
Part I. Non-metallic Materials of Engineering and Metallurgy 8vo, 2 00
Part n. Iron and Steel 8vo, 3 5©
Part in. A Treatise on Brasses, Bronzes, and Other Alloys and their
Constituents 8vo, 2 50
Tillson's Street Pavements and Paving Materials 8vo, 4 00
Tuiseaure and Maurer's Principles of Reinforced Concrete Construction.. -Svo, 3 00
Wood's (De V.) Treatise on the Resistance of Materials, and an Appendix on
the Preservation of Timber Svo, 2 00
Wood's (M. P.) Rustless Coatings: Corrosion and Electrolysis of Iron and
Steel 8vo, 4 00
RAILWAY EWGINEERING.
Andrews's Handbook for Street Railway Engineers 3x5 inches, mor. z 35
Berg*s Buildings and Structures of American Railroads 4to» 5 00
Brooks's Handbook of Street Railroad Location x6mo, mor. z 50
Butt's Civil Engineer's Field-book x6mo, mor. 2 50
Crandall's Railway and Other Earthwork Tables . 8vo. i 50
Transition Curve i6mo, mor. i 50
* Crockett's Methods for Earthwork Computations 8vo, i 50
Dawson's "Engineering" and Electric Traction Pocket-book i6mo, mor. 5 00
Dredge's History of the Pennsylvania Railroad: (1879) Paper, 5 00
• Fisher's Table of Cubic Yards Cardboard, 25
Godwin's Railroad Engineers' Field-book and Explorers' Guide. . . i6mo, mor. 2 50
Hudson's Tables for Calculating the Cubic Contents of Excavations and Em-
bankmenlfi 8vo, i 00
Ives and Hilts's Problems in Survesring, Raihroad Surveying and Geodesy
x6mo, mor. i 50
Molitor and Beard's Manual for Resident Engineers i6mo, i 00
Nagle's Field Manual for Railroad Engineers i6mo; mor. 3 00
Philbrick's Field Manual for Engineers i6mo, mor. 3 00
Raymond's Railroad Engineering. 3 volumes.
Vol. I. Railroad Field Geometry. (In Preparation.)
Vol. II. Elements of Railrdad Engineering 8vo, 3 50
Vol. III. Railroad Engineer's Field Book. (In Preparation.)
Searles's Field Engineering z6mo, mor. 3 00
Railroad SpiraL i6mo, mor. i 50
Taylor's Prismoidal Formulae and Earthwork 8vo, i 50
* Trautwine's Field Practice of Laying Out Circular Curves for Railroads.
i2mo. mor, 2 50
* Method of Calculating the Cubic Contents of Excavations and Embank-
ments by the Aid of Diagrams 8vo, 2 00
Webb's Economics of Railroad Construction Large i2mo, 2 50
Railroad Construction x6mo, mor. 5 00
Wellington's Economic Theory of the Location of Railways Small 8vo, 5 00
DRAWING.
Barr's Kinematics of Machinery 8vo,
* Bartlett's Mechanical Drawing 8vo,
* " " " Abridged Ed 8vo,
Coolidge's Manual of Drawing 8vo, paper,
Coolidge and Freeman's Elements of General Drafting for Mechanical Engi-
neers Oblong 4to,
Durley's Kinematics of Machines 8vo,
Emch's Introduction to Projective Geometry and its Applications Svo,
Hill's Text-book on Shades and Shadows, and Perspective Svo,
Jamison's Advanced Mechanical Drawing Svo,
Elements of Mechanical Drawing Svo,
Jones's Machine Design:
Part I. Klinematics of Machinery Svo,
Part n. Form, Strength, and Proportions of Parts Svo,
MacCord's Elements of Descriptive Geometry Syo,
Kinematics; or. Practical Mechanism Svo,
Mechanical Drawing 4to,
Velocity Diagrams Svo,
McLeod's Descriptive Geometry Large i2mo,
* Mahan's Descriptive Geometry and Stone-cutting. Svo,
Industrial Drawing. (Thompson.) Svo,
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Meyer's Descriptive Geometry 8vo,
Reed's Topographical Drawing and Sketching 4to,
Reid's Course in Mechanical Drawing 8vo,
Text-book of Mechanical Drawing and Elementary Machine Design . 8vo,
Robinson's Principles of Mechanism Svo,
Schwamb and Merrill's Elements of Mechanism. 8vo,
Smith's (R. S.) Manual of Topographical Drawing. (McMillan.) 8vo,
Smith (A. W.) and Marx's Machine Design. . 8vo,
* Titsworth's Elements of Mechanical Drawing Oblong 8vo,
Warren's Drafting Instruments and Operations i2mo,
Elements of Descriptive Geometry, Shadows, and Perspective 8vo,
Elements of Machine Construction and Drawing 8vo,
Elements of Plane and Solid Free-hand Geometrical Drawing. . . . i . 2mo,
General Problems of Shades and Shadows 8vo,
Manual of Elementary Problems in the Linear Perspective of Form and
Shadow '. lamo,
Manual of Elementary Projection Drawing z2mo,
Plane Problems in Elementary Geometry i2mo.
Problems, Theorems, and Examples in Descriptive Geometry 8vo,
Weisbach's Kinematics and Power of Transmission. (Hermann and
Klein.) 8vo,
Wilson's (H. M.) Topographic Surveying 8vo,
Wilson's (V. T.) Free-hand Lettering 8vo,
Free-hand Perspective 8vo,
Woolf's Elementary Course in Descriptive Geometry Large 8vo,
ELECTRICITY AND PHYSICS.
* Abegg's Theory of Electrolytic Dissociation, (von Ende.) i2mo,
Andrews's Hand-Book for Street Railway Engineering 3X5 inches, mor.,
Anthony and Brackett's Text-book of Physics. (Magie.) Large i2mo,
Anthony's Lecture-notes on the Theory of Electrical Measurements. . . . i2mo,
Benjamin's History of Electricity 8vo,
Voltaic CelL 8vo,
Betts'8 Lead Refining and Electrolysis v 8vo,
Classen's Quantitative Chemical Analysis by Electrolysis. (Boltwood.).8vo,
* Collins's Manual of Wireless Telegraphy i2mo,
Mor.
Crehore and Squier's Polarizing Photo-chronograph Svo^
* Danneel's Electrochemistry. (Merriam.) i2mo,
Dawson's "Engineering" and Electric Traction Pocket-book z6mo, mor
Dolezalek's Theory of the Lead Accumulator (Storage Battery), (von Ende.)
lamo,
Duhem's Thermodynamics and Chemistry. (Burgess.) 8vo,
Flather's Dynamometers, and the Measurement of Power i2mo,
Gilbert's De Magnete. (Mottelay.) 8vo,
* Hanchett's Alternating Currents i2mo,
Bering's Ready Reference Tables (Conversion Factors) i6mo, mor.
Hobart and Ellis's High-speed Dynamo Electric Machinery. (In Press.)
Holman's Precision of Measurements 8vo,
Telescopic Mirror-scale Method, Adjustments, and Tests. . . .Large 8vo,
* Kaiapetoff's Experimental Electrical Engineering 8vo,
Kinzbrunner's Testing of Continuous-current Machines 8vo,
Landauer's Spectrum Analysis. (Tingle.) 8vo,
Le Chatelier's High-temperature Measurements. (Boudouard — Burgess.) i2mo,
Lob's Electrochemistry of Organic Compounds. (Lorenz.) 8vo,
* Lyndon's Development and Electrical Distribntion of Water Power 8vo,
* Lyons's Treatise on Electromagnetic Phenomena. Vols. I. and II. 8vo, each,
* Michie's Elements of Wave Motion Relating to Sound and Light 8vo.
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Morgan's Cutline of the Theory of Solution and its Results iamo» z oo
* Physical Chemistry for Electrical Engineers lanao, i 50
Niaudet's Elementary Treatise on Electric Batteries. (Fishback) iimo. a 50
* Nonis's Introduction to the Study of Blectrleal Engineering 8vo, 2 so
* Parshall and Hobart's Electric Machine Design 4to, half morocco » 12 50
Reagan's Locomotives: Simple* Compound, and Electric. New Edition.
Large i2mo, 3 50
* Rosenberg's Electrical Engineering. (Haldane Gee — Kinzbrunner.). . .8vo, 200
Ryan» Norris, and Hozie's Electrical Machinery. Vol. 1 8vo, 2 50
Sjhapper's Laboratory Guide for Students in Physical Chemistry i2mo, i 00
Thurston's Stationary Steam-engines 8vo, 2 50
* Tillman's Elementary Lessons in Heat 8vo» i 50
Tory and Pitcher's Manual of Laboratory Physica. Large x2mo, 2 00
Ulke's Modem Electrolytic Copper Refining. Svo, 3 00
LAW.
* Davis's Elements of Law Svo, 2 50
* Treatise on the Military Law of United States. Svo, 7 00
* Sheep, 7 50
* Dudley's Military Law and the Procedure of Courts-martial . . . .Large i2mo, 2 50
Manual for Courts-martial i6mo, mor. z 50
Wait's Engineering and Architectural Jurisprudence Svo, 6 00
Sheep, 6 50
Law of Contracts Svo, 3 00
Law of Operations Preliminary to Construction in Engineering and Archi-
tecture Svo 5 00
Sheep, 5 50
MATHEMATICS.
Baker's Elliptic Functions Svo,' z 50
Briggs's Elements of Plane Analytic Geometry. (Bdcher) X2mo, z 00
♦Buchanan's Plane and Spherical Trigonometzy Svo, z 00
Byerley's Harmonic Functions ^ . Svo, z 00
Chandler's Elements of the Infinitesimal Calculus x2mo, 2 00
Compton's Manual of Logarithmic Computations Z2mo, x 50
Davis's Introduction to the Logic of Algebra Svo, z 50
* Dickson's College Algebra Large z2mo, z 50
* Introduction to the Theory of Algebraic Equations Large z2mo, z 25
Emch's Introduction to Projective Geometry and its Applications Svo, 2 50
Fiske's Functions of a Complex Variable Svo, z 00
Halsted's Elementary Synthetic Geometry Svo, z 50
Elements of Geometry Svo, z 75
* Rational Geometry z2mo, z 50
Hyde's Grassmann's Space Analysis Svo, z 00
*• Jonnson's (./ B.) Three-place Logarithmic Tables: Vest-pocket size, paper, xs
zoo copies, 5 00
* Mounted on heavy cardboard, S X 10 inches, 25
xo copies, 2 00
Johnson's (W. W.) Abridged Editions of Differential and Inteiral Calculus
Large x2mo, z vol. 2 50
Curve Tracing in Cartesian Co-ordinates z2mo, z 00
Differential Equations Svo, z 00
Elementary Treatise ^n Differential Calculus. (In Press.)
Jblementary Treatise on the Integral Calculus Large z2mo% z 50
* Theoretical Mechanics i2mo, 3 00
Theory of Errors and the Method of Least Squares Z2mo, z 50
Treatise on Differential Calculus Large Z2mo, 3 00
Treatise on the Integral Calculus. Large z2mo, 3 00
Treatise on Ordinary and Partial Differential Equations. . Large Z2mo, 3 50
12
X4ipUce'8 Philosophical Essay on Probabilities. (Truscott and Emory. )>x2mo, a oo
* Ludlow and Bass's Elements of Trigonometry and Logarithmic and Other
Tables 8vo, 3 00
Trigonometry and Tables published separately Each, 3 00
* Ludlow's Logarithmic and Trigonometric Tables 8vo, i 00
Macfarlane's Vector Analysis and Quaternions Bvo, 1 00
HcMahon*s Hyperbolic Functions 8vo, i 00
Manning's IrrationalNumbers and their Representation bySequences and Series
i2mo, I 25
Mathematical Monographs. Edited by Mansfield Merriman and Robert
S. Woodward Octavo, each i 00
No. z. History of Modern Mathematics, by David Eugene Smith.
No. 3. Synthetic Projective Geometry, by George Bruce Halsted.
No. 3. Determinants, by Laenas Gifford Weld. No. 4. Hyper-
bolic Functions, by James McMahon. No. 5. Harmonic Func-
tions, by William E. Byerly. No. 6. Grassmann's Space Analirsis,
by Edward W. Hyde. No. 7. Probability and Theory of Errors,
by Robert S. Wo6dward. ]^o. 8. Vector Analysis and Quaternions,
by Alexander Macfarlane. No. 9. Di£Ferential Equations, by
William Woolsey Johnson. No. 10. The Solution of Equations,
by Mansfield Merriman. No. 11. Functions of a Complex Variable,
by Thomas S. Fiske.
Maurer's Technical Mechanics 8vo,
Met! Iman's Method of Least Squares 8vo,
Solution of Equations 8vo,
Rice and Johnson's Differential and Integral Calculus. 2 vols, in one.
Large x2mo.
Elementary Treatise on the Differential Calculus. Large lamo.
Smith's History of Modern Mathematics 8vo,
* Veblen and Lennes's Introduction to the Real Infinitesimal Analysis of One
Variable 8vo,
* Waterbury's Vest Pocket Hand-Book of Mathematics for Engineers.
2^X51 inches, mor..
Weld's Determinations , 8vo,
Wood's Elements of Co-ordinate Geometry 8vo,
Woodward's Probability and Theory of Errors. 8vo,
MECHANICAL ENGINEERING.
MATERIALS OF ENGINEERING, STEAM-ENGINES AND BOILERS.
Bacon's Forge Practice ^. . x3mo, i 50
Baldwin's Steam Heating for Buildings i2mo, 2 50
Bair's Kinematics of Machinery. 8vo, 2 50
* Bartlett's Mechanical Drawing .8vo, 3 00
* " " " Abridged Ed 8vo, 1 50
Benjamin's Wrinkles and Recipes z2mo, 2 00
* Burr's Ancient and Modern Engineering and the Isthmian Canal 8vo, 3 50
Carpenter's Experimental Engineering 8vo, 6 00
Heating and Ventilating Buildings 8vo, 4 00
Clerk's Gas and Oil Engine Large i2mo, 4 00
Compton's First Lessons in Metal Working z2mo, i 50
Compton and De Groodt's Speed Lathe l3mo, i 50
Coolidge's' Manual of Drawing. . . 8vo, paper, z 00
CooUdge and Freeman's Elements of General Drafting for Mechanical En-
gineers Oblong 4to, 2 50
Cromwell's Treatise on Belts and Pulleirs i2mo, i 50
Treatise on Toothed Gearing x2mo, i 50
Dorley's Kinematics of Machines 8vo, 4 00
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Flather's Dynamometers and the Measurement of Power lamo, 3 00
Rope Drivini: i2mo, 2 o^
Gill's Gas and Fuel Analysis for Engineers zamo, x 25
Goss' 1 Locomotive Sparks 8vo, 2 00
Hall's Car Lubrication i2mo, x 00
Bering's Ready Reference Tables (Conversion Factors) i6mo, mor., 2 50
Hobart and Eliis's High Speed Dynamo Electric Machinery. (In Press.)
Button's Gas Engine 8vo, 5 00
Jamison's Advanced Mechanical Drawing 8vo, a 00
Elements of Mechanical Drawing 8vo, 2 50
Jones's Machine Design:
Part I. Kinematics of Machinery. 8vo, x 50
Part U. Form» Strength » and Proportioxis of Parts 8vo, 3 00
Kent's Mechanical Engineers' Pocket-book i6mo, mor , 5 00
Kerr's Power and Power Transmission 8vo, 2 00
Leonard's Machine Shop Tools and Methods] 8vo, 4 00
* Lorenz's Modem Refrigerating Machinery. (Pope» Baven» and Dean.) . . 8vo» 4 00
MacCord's Kinematics; or, Practical Mechanism 8vo» 5 00
Mechanical Drawing 4to, 4 00
Velocity Diagrams 8vo» i 50
MacFarland's Standard Reduction Factors for Gases 8vo» i 50
Mahan's Industrial Drawing. •(Thompson.) 8vo» 3 50
* Parshail and«Bobart's Electric Machine Design Small 4to, half leather, 12 50
Peele's Compressed Air Plant for Mines. (In Press.)
Poole's Calorific Power of Fuels 8vo, 3 00
* Porter's Engineering Reminiscences, 1855 to 1882 8vo, 3 00
Reid's Course in Mechanical Drawing. 8vo, 2 00
Text-book of Mechanical Drawing and Elementary Machine Design. 8vo, 3 00
Richard's Compressed Air x2mo, i 50
Robinson's Principles of Mechanism 8vo, 3 00
Schwamb and Merrill's Elements of Mechanism 8vo, 3 00
Smith's (0.) Press-working of Metals 8vo, 3 00
Smith (A. W.) and Marx's Machine Design 8vo, 3 00
Thurston's Animal as a Machine and Prime Motor, and the Laws of Energetics.
i2mo, z 00
Treatise on Friction and Lost Work in Machinery and Mill Work... 8vo, 3 00
Tillson's Complete Automobile Instructor i6mo, i 50
mor., a 00
* Titsworth's Elements of Mechanical Drawing Oblong 8vo, i 25
Warren's Elements of Machine Construction and Drawing 8vo, 7 50
* Waterbury's Vest Pocket Band Book of Mathematics for Engineers.
2iX5l ii^ches, mor., i 00
Weisbach's Kinematics and the Power of Transmission. (Herrmann —
Klein.) 8vo, 5 00
Machinery of Transmission and Governors. (Berrmann — Klein.). .8vc, 5 00
Wolff's Windmill as a Prime Mover 8vo, 3 00
Wood's Turbines 8vo, 2 50
MATERIALS OF ENGINEERING.
* Bovey's Strength of Materials and Theory of Structures 8vo, 7 50
Burr's Elasticity and Resistance of the Materials of Engineering 8vo, 7 50
Church's Mechanics of Engineering. ., 8vo, 6 00
* Greene's Structural Mechanics 8vo, 2 50
Bolley and Ladd's Analysis of Mixed Paints, Color Pigments, and Varnishes.
Large Z2mo, 2 50
Johnson's Materiab of Construction 8vo, 6 00
Keep's Cast Iron 8vo, 2 50
Lanza's Applied Mechanics 8vo, 7 50
14
Maire's Modern Pisments and their Vehicles xamo, 2 00
Martens's Handbook on Testing Materials. (Henning.) 8vo, 7 50
Maurer's Technical Mechanics 8vo, 4 00
Merriman's Mechanics of Materials 8vo, 5 00
'*' Strength of Materials i2mo, i 00
Metcalf 's SteeL A Manual for Steel-users i2mo» 2 00
Sabin's Industrial and Artistic Technology of Paints and Varnish Svo, 3 00
Smith's Materials of Machines z2mo, i 00
Thurston's Materials of Engineering 3 vo]s.» 8vo, 8 00
Part I. Non-metallic Materials of Engineering, see Civil Engineering,
page 9.
Part II. Iron and Steel 8vo, 3 50
Part ni. A Treatise on Brasses, Bronzes, and Other Alloys and their
Constituents 8vo» 2 50
Wood's (De V.) Elements of Analytical Mechanics 8vo, 3 00
Treatise on the Resistance of Materials and an Appendix on the
Preservation of Timber 8vo, a 00
Wood's (M. P.) Rustless Coatings: Corrosion and Electrolysis of Iron and
Steel .' 8vo, 4 00
STEAM-ENGINES AND BOILERS.
Berry's Temperature-entropy Diagram i2mo, z 25
Carnot's Reflections on the Motive Power of Heat. (Thurston.) i2mo, z 50
Chase'^ Art of Pattern Making Z2mo, 2 50
Creighton's Steam-engine and other Heat-motors 8vo, 500
Dawson's "Engineering" and Electric Traction Pocket-book x6mo, mor., 5 00
Ford's Boiler Making for Boiler Makers x8mo, z 00
Goss's Locomotive Performance 8vo, 5 00
Hemenway's Indicator Practice and Steam-engine Economy x2mo, 2 00
Button's Heat and Heat-engines 8vo, 5 00
Mechanical Engineering of Power Plants 8vo, 5 00
Kent's Steam boiler Economy 8vo, 4 00
Kneass's Practice and Theory of the Injector 8vo, x 50
MacCord's Slide-valves 8vo, 2 00
Meyer's Modern Locomotive Construction 4to, zo 00
Moyer's Steam Turbines. (Tn Press.)
Peabody's Manual of the Steam-engine Indicator x2mo» z 50
Tables of the Properties of Saturated Steam and Other Vapors 8vo, z 00
Thermodynamics of the Steam-engine and Other Heat-engines. . . . . .8vo, 5 00
Valve-gears for Steam-engines. ... * 8vo, 2 50
Peabody and Miller's Steam-boilers 8vo» 4 00
Pray's Twenty Years with the Indicator Large 8vo, 2 50
Pupin's Thermodynamics of Reversible Cycles in Gases and Saturated Vapors.
(Osterberg.) z2mo, 1 aj
Reagan's Locomotives: Simple, Compound, and Electric. New Edition.
Large z2mo, 3 50
Sinclair's Locomotive Engine Running and Management i2mo, a 00
Smart's Handbook of Engineering Laboratory Practice. lamo, 2 50
Snow's Steam-boiler Practice 8vo, 3 00
Spangler's Notes on Thermodynamics Z2mo, z 00
Valve-gears 8vo, 2 50
Spangler, Greene, and Marshall's Elements of Steam-engineering 8vo, 3 00
Thomas's Steam-turbines 8vo, 4 00
Thurston's Handbook of Engine and Boiler Trials, and the Use of the Indi-
cator and the Prony Brake Svo, 5 00
Handy Tables Svo, z 50
Manual of Steam-boilers» their Designs, Construction, and Operation..8vo, 5 00
15
Thunton's Manual of the Steam-engine a vols., 8vo, lo oo
Part L History, Structure, and Theory 8vo, 6 oo
Part n. Design, Construction, and Operation 8vo, 6 oo
Stationary Steam-engines. 8vo, 2 50
Steam-boiler Explosions in Theory and in Practice 12mo, z 50
Wehrenfenning'sAnalysisandSoftenlngof Boiler Feed-water (Patterson) 8vo, 400
Weisbach's Heat, Steam, and Steam-engines. (Du Bois.) .' . . . .8vo, 5 00
Whitham's Steam-engine Design 8vo, 5 00
Wood's Thermodynamics, Heat Motors, and Refrigerating Machines. . .8vo, 4 00
MECHANICS PURE AND APPLIED.
Church's Mechanics of Engineering 8vo, 6 00
Notes and Examples in Mechanics 8vo, 2 00
Dana's Text-boofc of Elementary Mechanics for Colleges and Schools. . lamo, i 50
Dtt Bois's Elementary Principles of Mechanics:
VoL I. Kinematics 8vo, 3 50
VoL n. Statics 8vo, 4 00
Mechanics of Engineering. VoL I Small 4to, 7 50
VoL n Small 4to, 10 00
* Greene's Structural Mechanics 8vo, 2 50
James's Kinematics of a Point and the Rational Mechanics of a Particle.
Large 12mo, 2 00
* Johnson's ( W. W.) Theoretical Mechanics. l2mo, 3 00
Lanza's Applied Mechanics 8vo, 7 50
* Martin's Text Book on mechanics, VoL I, Statics 12mo, i 25
* Vol. 2, Kinematics and Kinetics . .i2mo. 1 so
Maurer's Technical Mechanics 8vo, 4 00
* Merriman's Elements of Mechanics 12mo, i 00
Mechanics of Materials 8vo, 5 00
* Michie's Elements of Analjrtical Mechanics. 8vo, 4 00
Robinson's Principles of Mechanism 8vo, 3 00
Sanborn's Mechanics Problems Large l2mo, i 50
Schwamb and Merrill's Elements of Mechanism 8vo, 3 00
Wood's Elements of Analytical Mechanics. 8yo, 3 00
Principles of Elementary Mechanics 12mo, i 25
MEDICAL.
Abderhalden's Physiological Chemistry in Thirty Lectures. (Hall and Def ren).
(In Press).
von Behrlng's Suppression of Tuberculosis. (Bolduan.) i2mo,
* Bolduan's Immune Sera x2mo,
Davenport's Statistical Methods with Special Reference to Biological Varia-
tions i6mo, mor.,
Ehrlich's Collected Studies on Immunity. (Bolduan.) 8vo»
* Fischer's Phy8i(dogy of Alimentation Large z2mo, doth,
de Fursac's Manual of Psychiatry. (Rosanoff and Collins.) Large x2mo,
Hammarsten's Text-book on Ph]rsiological Chemistry. (MandeL) 8vo,
Jackson's Directions for Laboratory Work in Phirsiological Chemistry. ..8vo,
Lassar-Cohn's Practical Urinary Analysis. (Lorenz.) i2mo,
Mandel's Hand Book for the Bio-Chemical Laboratory i2mo,
* Pauli's Physical Chemistry in the Service of Medicine. (Fischer.) .... i2mo,
* Pozzi-Escot's Toxins and Venoms and their Antibodies. (Cohn. ) i2mo,
Rostoski's Serum Diagnosis. (Bolduan.) i2mo,
Ruddiman's Incompatibilities in Prescriptions 8vo.
Whys in Pharmacy Z2mo,
Salkowski's Physiological and Pathological Chemistry. (Orndorff.) 8vo,
* Satterlee's Outlines of Human Embryology i2mo.
Smith's Lecture Notes on Chemistry for Dental Students ($vo,
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Steel's Treatise on the Diseases of the Dog Svo, 3 50
* Whipple's Typhoid Fever Large i2mo, 3 00
Woodhull's Notes on Military Hygiene x6mo, i 50
* Personal Hygiene i2mo, i 00
Worcester and Atkinson's Small Hospitals Establishment and Maintenance,
and S.ggestions for Hospital Architecture, with Plans for a Small
Hospital i2mo, z 25
METALLURGY.
Betts's Lead Refining by Electrolysis gvo. 4 00
Bolland's Encyclopedia of Foimding and Dictionary of Foundry Tenns Used
in the Practice of Moulding 12mo,
Iron Founder i2mo.
• * * • Supplement i2mo,
Douglas's Untechnical Addresses on Technical Subjects i2mo,
Goesel's Minerals and Metals: A Reference Book z6mo» mor.
* Des's Lead-smelting 12mo,
Keep's Cast Iron. 8vo,
Le Chatelier's High-temperature Measurements. (Boudouard — Burgess.) 12mo,
Metcalf's SteeL A Manual for Steel-users 12mo,
Miller's Cyanide Process 12mo
Minet's Production of Aluminum and its Industrial Use. (Waldo.). . . . 12mo,
Robine and Lenglen's Cyanide Industry. (Le Clerc.) 8vo,
Ruer '8 Elements of MetaUography. (Mathewson). (In Press.)
Smith's Materials of Machines 12mo,
Thtu^ton's Materials of Engineering. In Three Parts. 8vo,
part I. Non-metallic Materials of Engineering, see Civil Engineering,
page 9.
Part II. Iron and Steel 8vo, 3 so
Part HI. A Treatise on Brasses, Bronzes, and Other Alloys and their
Constituents 8vo, 2 50
Ulke's Modem Electrolytic Copper Refining 8vo, 3 00
West's American Foundry Practice l2mo, 2 50
Moulders Text Book 12mo, 2 50
Wilson's Chlorination Process ^ l2mo, i 50
Cyanide Processes v i2mo, i so
MINERALOGY.
Barringer's Description of Minerals of Commercial Value. Oblong, morocco, 2 50
Boyd's Resotu'ces of Southwest Virginia 8vo 3 00
Boyd's Map of Southwest Virginia Pocket-book form. 2 00
* Browning's Introduction to the Rarer Elements 8vo, i 50
Brush's Manual of Determinative Mineralogy. (Penfield.) 8vo, 4 00
Butler's Pocket Hand-Book of Minerals 16mo, mor. 3 00
Chester's Catalogue of Minerals 8vo, paper, i 00
Cloth, z 25
Crane's Gold and Silver. (In Press.)
Dana's First Appendix to Dana's New " System of Mineralogy. .". .Large 8vo, i 00
Manual of Mineralogy and Petrography z2mo 2 00
Minerals and How to Study Them z2mo, i so
Sirstem of Mineralogy Large 8yo, half leather, 12 50
Text-book of Mineralogy 8vo, 4 00
Douglas's Untechnical Addresses on Technical Subjects Z2mo, z 00
Eakle's Mineral Tables 8vo, z 25
Stone and C]ay Products Used in Engineering. (In Preparation).
Egleston's Catalogue of Minerals and Simonyms 8vo, 2 50
Goesel's Minerals and Metals : A Reference Book i6mo, mor. 3 00
Groth's Introduction to Chemical Crystallography (Marshall) z2mo, z 25
17
*Idding8'8 Rock Minerals 8vo, 5 00
Johannfleii*8 Detennmatlon of Rock-fonning Minerals in Thin Sections 8vo, 4 00
'* Martin's Laboratory Guide to Qualitative Analysis with the Blowpipe. 12010, 60
Merrill's Non-metallic Minerals: Their Occurrence and Uses 8vo» 4 00
Stones for Buildlnj; and Decoration . . 8vo, 5 00
* Penfield's Notes on Determinative Mineralogy and Record of Mineral Tests.
8vo, paper, 50
Tables of Mineials, Including the Use of Minerals and Statistics of
Domestic Production 8vo, i 00
Pirsson's Rocks and Rock Blinerals. (In Press.)
* Richards's Synopsis of Mineral Characters z2mo, mor.
* Ries*s Clays: Their Occurrence, Properties, and Uses 8vo,
* Tillman's Text-book of Important Minerals and Rocks 8vo,
MINING.
* Beoxd's Mine Gases and Explosions Large lamo,
Boyd's Map of Southwest Virginia Pocket-book form.
Resources of Southwest Virginia 8vo,
Crane's Gold and Silver. (In Press.)
Douglas's Untechnical Addresses on Technical Subjects z2mo,
Eissler's Modem High Explosives 8vo.
Goesel's Miners and Metals : A Reference Book i6mo, mor.
I! Iseng's Manual of Mining 8vo,
* Iles's Lead-smelting zamo,
Miller's Cyanide Process z2mo,
O'DriscoU's Notes on the Treatment of Gold Ores 8vo,
Peele's Compressed Air Plant for Mines. (In Press. )
Riemer 's Shaft Sinking Under Diiacult Conditions . (Coming and Peele) . . . 8vo,
Robine and Lenglen's Cyanide Industry. (Le Clerc.) 8vo,
* Weaver's Military Explosives 8vo,
Wilson's Chlorination Process i2mo.
Cyanide Processes Z2mo,
Hydraulic and Placer Mining. 2d edition, rewritten Z2mo,
Treatise on Practical and Theoretical Mine Ventilation 12 mo,
SANITARY SCIENCE.
Association of State and National Food and Dairy Departments, Hartford Meeting,
1906 8vo,
Jamestown Meeting, 1907 8vo,
* Bashore's Outlines of Practical Sanitation 12mo,
Sanitation of a Country House 12mo,
Sanitation of Recreation Camps and Parks 12mo,
Folwell's Sewerage. (Designing, Construction, and Maintenance.) 8vo,
Water-supply Engineering 8vo,
Fowler's Sewage Works Analyses 12mo,
Fuertes's Water-filtration Works 12mo,
Water and Public Health 12mo,
Gerhard's Guide to Sanitary House-inspection 16mo,
* Modem Baths and Bath Houses 8vo,
Sanitation of Public Buildings ; 12mo,
Hazen's Clean Water and How to' Get It Large i2mo.
Filtration of Public Water-supplies 8vo,
Kinnicut, Winslow and Pratt's Purification of Sewage. (In Press. )
Leach's Inspection and Anal3rsis of Food with Special Reference to State
Control .* 8vo,
Mason's Examination of Water. (Chemical and Bacteriological) 12mo,
Water-supply. (Considered principally from a Sanitary Standpoint) . . 8vo»
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* Merriman's Elements of Sanitary Engineering i . . . .Bvo,
Ogden's Sewer Design 12mo,
Parsons's Disposal of Municipal Refuse Svo,
Prescott and Winslow's Elements of Water Bacteriology, with Special Refer-
ence to Sanitanr Water Analysis. 12mo,
* Price's Handbook on Sanitation. 12mo,
Richards's Cost. of Food. A Study in Dietaries 12mo,
Cost of Living as Modified by Sanitary Science l2mo,
.Cost of Shelter 12mo,
* Richards and Williams's Dietary Computer Svo,
Richards and Woodman's Air, Water, and Food from a Sanitary Stand-
point Svo,
Rideal's Disinfection and the Preservation of Food Svo,
Sewage and Bacterial Purification of Sewage Svo,
Soper'8 Air and Ventilation of Subways. (In Press.)
Turneaure and Russell's Public Water-supplies Svo,
Venable's Garbage Crematories in America Svo,
Method and Devices for Bacterial Treatment of Sewage Svo,
Ward and Whipple's Freshwater Biology. (In Press. )
Whipple's Microscopy of Drinking-water. . . . . « Svo,
* T3^hod Fever. Large l2mo.
Value of Pure Water Large i2mo.
Winton's Microscopy of Vegetable Foods Svo,
MISCELLAl^OUS.
Emmons's Geological Guide-book of the Rocky Mountain Excursion of the
International^ Congress of Geologists Large Svo,
Ferrel's Popularl'reatise on the Winds Svo,
Fitzgerald^s Boston Machinist zSmo,
Gannett's Statistical Abstract of the World 24mo,
Haines's American Railway Management 12mo,
* Hanusek's The Microscopy of Technical Products. (Winton) Svo,
Ricketts's History of Rensselaer Polytechnic Institute 1834-1894.
Large z3mo,
Rotherham's Emphasized New Testament Large Svo,
standage's Decoration of Wood, Glads, Metal, etc l2mo,
Thome's Structural and Physiological Botany. (Bennett) l6mo,
Westermaier's Compendium of (General Botany. (Schneider) Svo,
Winslow's Elements of Applied Microscopy 12mo,
HEBREW AND CHALDEE TEXT-BOOKS.
Green's Elementary Hebrew Grammalr z3mo, z 3S
Gesenius's Hebrew and Chaldee Lexicon to the Old Testament Scriptures.
(Tregelles.) Small 4to, half morocco, 5 00
19
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m 1 1917
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