Page:The American Cyclopædia (1879) Volume VII.djvu/341

 FORTIFICATION 333 redoubt for the outwork; and as an interior work to sweep the terrepleins of the enceinte. Where the caponniere is not flanked from the main work, by scarp galleries or batteries, other arrangements are devised, as projecting wings, or small caponnieres attached to the main one. Free use of casemated defences is made in this system ; also, systems of mines for interior as well as exterior defence are arranged in connection with the counterscarp galleries. The profile differs but slightly from that used in the bastioned system. The use of detached and semi-detached scarps affords fa- cilities for arranging corridors or open pas- sages around the works, and opportunities for loopholes. To sum up, this system proposes to flank the ditches not from the work itself, but by auxiliary works ; to provide an over- whelming artillery fire protected in defensive casemates ; and to organize strong permanent works within and independent of the en- ceinte, which are to serve as a secure retreat for the garrison when forced to give up its defence. The advantages of this system, com- pared with the bastioned, may be stated as follows: 1, that the interior space enclosed by equal lengths of enceinte is greater than in the bastioned; 2, that the faces of the work, from the greater obtuseness of the sa- lient angles, are less exposed to ricochet fire ; 3, that the fire of the faces has a better bear- ing on the distant defence ; 4, that, requiring fewer points on a given extent of line to be fortified, there will be fewer flanks, and more artillery will be disposable for the faces and curtains ; 5, that the besiegers will be forced to a greater development of trenches for the same number of points. On the other hand, the system is deficient in the strong concen- trated cross fires that exist in the bastioned system in front of the salients. The flanking arrangement of the ditch being an exterior work, as soon as its fire is silenced the main work will be exposed to an escalade. It is further objected to this system that the nu- merous works of masonry can be easily ruined by distant batteries of heavy calibre, especially when weakened by loopholes and casemates, as is the case in the caponnieres and defensive barracks ; that the distribu- tion of troops and material of war through- out the independent works deprives the de- fence of that unity and concert of action so necessary for a successful resistance ; that the works are more costly from the greater amount of masonry used ; and finally, that it is im- prudent to abandon a system that has been tested for one that does not possess this ad- vantage. In the discussions which have taken place upon the merits of the two systems between engineers advocating them, an exag- geration of the defects and the depreciation of the advantages of the system analyzed seem to be the governing principles. The truth is that both possess great merits, and due credit should be given to each system. The fragility of masonry and the ease with which it can be destroyed by heavy projectiles, the increase in calibre of the cannon used and in accuracy of firing, must naturally incline engineers to limit its employment as much as possible ; reserving its use for positions where it will not be exposed, or is so covered that nothing can be feared from the besieger's guns. It is unnecessary to dwell here upon the cir- cular and tenailled systems. They observe the general conditions that we have given as com- mon to all systems of permanent works. The advantages they possess and the objections that are made will be apparent to those who have carefully examined the bastioned and polygo- nal systems. General Remarks. So far in the consideration of fortifications we have confined ourselves to the first three conditions and an allusion to the fourth. No work would be complete without bomb-proof shelters for the troops and magazines, whatever be the system adopted. The details of these works must be looked for in books treating specially of these constructions. The fifth general condition in- volves the use of water when it can be obtain- ed, the character of the soil, the use of mines, and the arrangement of the parts of a w'ork when placed on an irregular site. The last case calls largely upon the skill and the science of the engineer. When the terreplein of a work is arranged so as to shelter the troops and ma- teriel by the parapet or by traverses from the fire of the enemy who occupies ground higher than the site of the work, it is said to be de- filed from that fire. This fire may be direct or in reverse. These problems of direct and re- verse defilement are among the most important in the profession, and demand a minute and la- borious study of the natural features of the po- sition in relation to the defence. No rules but of a very general character can be laid down for the guidance of engineers in such cases. We may conclude that in order to arrange the different parts of a fortification and combine them properly, a knowledge of the means which may be employed to fulfil the general condition before given, and a suitable adaptation of these parts to the natural features of the position, are necessary. The utility of permanent forti- fications has been seriously called in question ; but it is enough to say that Napoleon, the arch- duke Charles of Austria, the duke of Welling- ton, and others have all regarded them as of great utility and of absolute necessity for a country. It is probable that no great general has ever entertained a different opinion from them on this subject. The selection of the points to be fortified will be influenced by the natural features of the country. As a rule, those points known as strategic points are the ones selected ; that is, those points which may be considered as the principal objects to be gained by an enemy, or whose occupation would be of manifest advantage to him. The capital of a country is such a point from its importance. The effect of seizing the capital