republic--such as the prolonged operations of Caesar in Gaul, and the civil contests--made a standing army a necessity. During the civil wars between Caesar and Pompey the legions were forty in number; under Augustus, but twenty-five. Alexander Severus increased them to thirty-two. This was the standing force of the empire,--from one hundred and fifty thousand to two hundred and forty thousand men, stationed in the various provinces. The main dependence of the legion was on the infantry, which wore heavy armor consisting of helmet, breastplate, greaves on the right leg, and on the left arm a buckler, four feet in length and two and a half in width. The helmet was originally made of leather or untanned skin, strengthened and adorned by bronze or gold, and surmounted by a crest which was often of horse-hair, and so made as to give an imposing look. The crests served not only for ornament, but to distinguish the different centurions. The breastplate, or cuirass, was generally made of metal, and sometimes was highly ornamented. Chain-mail was also used. The greaves were of bronze or brass, with a lining of leather or felt, and reached above the knees. The shield worn by the heavy-armed infantry was not round, like that of the early Greeks, but oval or oblong, adapted to the shape of the body, such as was adopted by Philip and Alexander, and was made of wood or wicker-work. The weapons were a light spear, a pilum, or javelin, over six feet long, terminated by a steel point, and a short cut-and-thrust sword with a double edge. Besides the armor and weapons of the legionary, he usually carried on the marches provisions for two weeks, three or four stakes used in forming the palisade of the camp, besides various tools,--altogether a burden of sixty or eighty pounds per man. The legion was drawn up eight deep, and three feet intervened between rank and file, which disposition gave great activity, and made it superior to the Macedonian phalanx, the strength of which depended on sixteen ranks of long pikes wedged together. The general period of service for the infantry was twenty years, after which the soldier received a discharge, together with a bounty in money or land. The cavalry attached to each legion consisted of three hundred men, who originally were selected from the leading men in the State. They were mounted at the expense of the State, and formed a distinct order. The cavalry was divided into ten squadrons. To each legion was attached also a train of ten military engines of the largest size, and fifty-five of the smaller,--all of which discharged stones and darts with great effect. This train corresponded with our artillery.