ent and slight relief,
partaking much of the nature of field-works.[45]

[Footnote 45: The general principles of permanent fortification may be
best learned from the writings of Cormontaigne, St. Paul de Noizet, and
Laurillard-Fallot. A list of valuable books of reference on the several
branches of military engineering will be given at the close of the next
chapter.]

CHAPTER XIV.

FIELD-ENGINEERING.

_Field-Engineering_ includes the making of military reconnaissances,
temporary fortifications, and military roads; the planning and
construction of military bridges; the attack and defence of military
works;--in fine, all the various duties of engineer troops, either in
the operations of a campaign, or in the dispositions on the
battle-field.

_Military reconnaissance._--By this term is meant an examination of a
portion of the theatre of war, to ascertain its military character and
resources. If the examination be made of a large district of country,
and for an entire campaign, the reconnaissance is _general_; if made for
collecting detailed information respecting a proposed line of march, the
passage of a river, the position of an enemy, &c., it is termed
_special_.

In making a general reconnaissance, great care should be taken to
collect accurate information respecting the general topography of the
country; the character of the mountains, forests, and water-courses; the
nature of the roads, canals, and railways; the quality of the soil, and
the amount of provisions and forage it produces; the population and
character of the cities, towns, and villages, the commercial and
manufacturing resources of every part of the country, and the means of
transportation to be found in each district. The plan of military
operations will be based on the information thus obtained, and any
serious error in the reconnaissance may involve the results of the
campaign, and even the fate of the war.

In a special reconnaissance, not only accurate but minute information
will be required: the character of the roads must be given in detail;
the nature of the water-courses, their depth and velocity; the position
and character of bridges, and fords;--in fine, a full description of all
obstacles to be encountered, and the means that can be made available
for overcoming these obstacles.

A reconnoitring officer may usually derive much valuable information
from the published maps and descriptions of the country to be examined;
addi