Page:Encyclopædia Britannica, Ninth Edition, v. 9.djvu/454

 FORTIFICATION to manoeuvre on the opposite side; but in proportion to the numbers to be passed over the bridge, and to FIQ. 60. Horn Work defending Bridge. the extent of advance contemplated, it will be necessary either to increase the importance of the works forming the bridge head, or to form more than one bridge in connexion with them. Nothing can be more fatal to a retreating army than to be driven back upon a river without a line of intrench- ment sufficient to enable it to maintain its ground whilst its arrangements for passing the river are in progress. Fig. 60 exhibits one such arrangement, in which the Horn Work front has been much enlarged, and a lunette as a keep introduced within it. The mode in which the troops can move out at the sides, under protection of covering and flanking parapets, is shown, as well as the barbettes for guns, which become necessary in works having so im portant an object. Fig. 61 represents a line of Tenaille FIG. 61. Tenaille Intrencliments pi otecting Bridge. Intrenchments in front of the lunette, and a liue of intrenchment on the near side of the river, from part of which the last terminal branches of the tenailles are flanked. In this figure T, T represent traverses, and F, F either chains or lines of pickets placed across the stream, the object of the first being to secure the bridge from the ricochet fire cf the enemy, and of the second to secure it from destruction by burning or explosive bodies launched by the enemy up the stream, to float down upon the bridge. More extended intrenchments might be formed of lines of lunettes with intervening intrenchments ; but it is unnecessary here to pursue the subject further, as the engineer must necessarily adapt his works to the nature of the ground, and to the strength of the army for which he is required to prepare a defensive position, from which it may either advance or retire, without risk or confusion, as the necessities of war may require. PERMANENT FORTIFICATION. If, as has been stated, simple lines or works of fortifica- cation have been adopted even by the rudest tribes of wandering savages, for their temporary defence or security, the more massive and artistic works of permanent defence would seem to imply a certain amount of civilization. As an art, indeed, Fortification is almost co-existent with society. When men first assembled together for mutual protection, and placed their habitations in one spot, the law of necessity, springing in this case from the prin ciple of self-defence, rendered it indispensable for them to adopt means for securing their families and their property against the sudden inroads of enemies. In the early ages, men were sufficiently protected by a wall, from behind which they could with safety discharge darts, arrows, and other missiles against an assailant. But when, in the progress of improvement, new and more powerful means of attack were discovered, it became necessary to increase, in a cor responding degree, the power of resistance ; and so it came to pass that the feeble defensive structures of primitive times were superseded by solid ramparts, flanked and com manded by elevated towers; and, as the power of attacking fortresses or places of strength became augmented by sue cessive devices and inventions, so the means of resistance became proportionally increased, until the art of Fortifica tion arrived at a state of comparative perfection, in which for many ages it remained nearly stationary. The various improvements which were from time to time made, in strengthening the walls and in adding to the defences of ancient cities, are recorded in history, and need not be detailed in this place. The first walls of which we read were of brick. Amongst the ancient Greeks, brick and rubble stones intermixed were used, as we find from the description of the wall which con nected Mount Hymettus with the city of Athens ; but, surrounding several cities were works of Cyclopean char acter, built of huge stones, without mortar, placed with their longer axis transversely to the line of wall, and arranged with great care and skill. The walls of Babylon and Nineveh indicate a prodigious advancement in the art of Fortification, and are justly accounted amongst the wonders of the ancient world. Those of the former city, ascribed by some to Belus, and by others to Semiramis, were thirty-two feet in thickness, and one hundred feet in height, surmounted at intervals by towers ten feet higher, and cemented by means of bitumen or asphaltum ; they encompassed a vast area, and presented a solid defence, which no means of attack known in ancient times were sufficient to overcome or beat down. The walls of Jerusalem, though of smaller dimensions, appear to have been little inferior in strength and solidity to those of Babylon ; for, in the siege of that capital by Vespasian, all the Roman battering-rams and other engines, though used with the utmost vigour through a whole night, only succeeded in disengaging four stones in the masonry of the tower of Antonia. But after Fortification had arrived at the state in which we find it in the works of these and other cities, it remained stationary for ages, and perhaps even retrograded somewhat, until the discovery of gunpowder, the invention of artillery, and the application of both to military purposes, effected an entire revolution in the prin ciples of attack and defence. Then the towers, which had formed secure flanking defences against assailants armed only with arrows and darts, no longer afforded protec tion against projectiles discharged from cannon ; and even those battlements which had defied the catapult and the bat tering-ram speedily fell before the new force with which they were assailed, burying their defenders in their ruins. The ancient system of Fortification being thus found of little avail against the new method of attack which came into general use towards the close of the fifteenth century, it became indispensably necessary to adopt im proved methods of defence. The plan of fortifying with bastions is believed to have originated with the Italians early in the fifteenth century; though Papaciuo D Antoni, professor of artillery and engineering of Turin, states, in