ORTIFICATIONS. From the remotest ization the art of fortification, in some e or another, has been in practice by 'all ons and its character has been more or influenced not only by the natural features he country, but by the political and social ditions of its inhabitants. In its earliest lications, we find men resorting to one or -e simple enclosures of earthen walls; or these surmounted by stakes placed in juxta mon ; or of stakes alone firmly planted in ground, with a strong wattling between m. A resort of such feel* means shows only a very low state of/ this branch of military art, but also. of that of the ack. This clas' of fortifications for the sense of entire frontiers was mostly em ,yed in--the east of Europe and was at the se found a sufficient protection against use nomadic tribes that for ages roamed over vast plains. The next obvious and necessary ip was to form walls either of rough blocks stone, or of these interlaced with the trunks heavy trees. Obstructions of this kind old be used only to a limited extent, and were nfined to the defenses of places forming the rly centres of population. As human inven 3n was developed, these, in turn, were found present no serious obstacle to an assault by calade; giving to the assailed only temporary ivantage of a more commanding position, and ley gave place to walls of dressed stone or rick, whose height and perpendicular face alike ade defiance to individual attempts to climb iem, or the combined effort of an escalade. 'hese formidable defenses, with• flanking 3wers, were in their time found to be insuffi ient against the ingenuity and skill of the as ailant, who, by means of covered galleries of imber, sometimes above ground and sometimes eneath, gradually won his way to the foot of he wall, where, by breaking his way through t, he removed the sole obstruction to a bodily allusion with the assailed. Changes in the mark led to new modifications in the defense, which consisted in surrounding the place by wide and deep ditches, of which the walls iormed the scarp, the counterscarp being either, of earth or revetted. The gigantic pro
file often given to the fortifications of antiquity seems almost incredible, as well as their ex tent. In inany cases a double wall of stone or brick was filled in between with earth, form ing a wide rampart upon which several vehicles could go abreast. The wall built by the Romans between Carlisle and Newcastle to restrain the incursions of the Picts into the southern por tions of the island was 16 miles in extent, about 12 feet in height; and 9 feet in thick ness. The dimensions and extent of this work sink almost into insignificance when compared with those of the celebrated wall of China, built to restrain the incursions of the Tartars. This structure was about 1,500 English - miles in length, having a height of 27 feet and a thick ness at top of 14 feet The mode of attack of fortified places resorted to by the ancients was reduced to settled Toles, and brought to the highest state of perfection by the,Greebs, about the time of Alexander the Great and the immediate successors to his 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, covering themselves by lines of entrenchments strengthened by towers, and, in the case of seacoast places, also by fleets, from assaults both from with out'ond from the place invested. The Romans evinced their decided military aptitude not only in the\ employment of the ordinary systematic method's of the attack and defense of fortified places, but in their application of the cardinal principle of mutual defensive relations be tween the parts of a fortified position, obtained by advanced ,and retired portions of the n ceinte, and also in the adaptation of entrench ments to the natural -features of the site.