[Footnote 43:  The subjects discussed in this chapter are also treated by most authors on Military Organization and Military History, and by the several writers on Military Engineering.  Allent, Vauban, Cormontaigne, Rocquancourt, Pasley, Douglas, Jones, Belmas, Napier, Gay de Vernon, may be referred to with advantage.  Pasley, Douglas, Jones, and Napier, speak in the strongest terms of the importance of engineer troops in the active operations of a war, and of the absolute necessity of organizing this force in time of peace.  A list of books of reference on Military Engineering will be given at the close of the following chapters.

While these pages are passing through the press, Congress has authorized the President to raise one company of engineer troops!  This number is altogether too small to be of any use in time of war.]

CHAPTER XIII.

PERMANENT FORTIFICATIONS.

Fortification is defined,—­the art of disposing the ground in such a manner as to enable a small number of troops to resist a larger army the longest time possible.  If the work be placed in a position of much importance, and its materials be of a durable character, it is called permanent; if otherwise, it receives the appellation of field, or temporary.  Fieldworks are properly confined to operations of a single campaign, and are used to strengthen positions which are to be occupied only for a short period.  Generally these works are of earth, thrown up by the troops in a single day.  They are intimately connected with a system of permanent fortifications, but from the facility of their construction, no provision need be made for them before the actual breaking out of war.  Indeed, they could not well be built before hostilities commenced, as their locality in each case must be determined by the position of the hostile forces.

Having already described the general influence of permanent fortifications as a means of national defence, we shall here speak merely of the principles of their construction.  It is not proposed to enter into any technical discussion of matters that especially belong to the instruction of the engineer, but merely to give the nomenclature and use of the more important parts of a military work; in a word, such general information as should belong to officers of every grade and corps of an army.

The first species of fortification among the ancients was of course very simple, consisting merely of an earthen mound, or palisades.  A wall was afterwards used, and a ditch was then added to the wall.  It was found that a straight wall could be easily breached by the enemy’s battering-rams; to remedy this evil, towers were built at short intervals from each other, forming a broken line of salient and re-entering parts.  These towers or salient points gradually assumed a shape approximating to the modern bastion.