The highest authority in relation to the construction of an army is Polybius, who was contemporary with Scipio, at a period when Roman discipline was most perfect. A fragment from his sixth book gives considerable information. A chapter of Livy--the eighth--is also very much prized. Salmasius and Lepsius have also written learned treatises. Smith's Dictionary, which is full of details in every thing pertaining to the weapons, the armor, the military engines, the rewards and punishments of the soldiers, refers to Folard's _Commentaire_, to _Memoires Militaires sur les Grecs et les Remains_, by Guischard, and to the _Histoire des Campagnes d'Hannibal en Italie_, by Vaudencourt. Tacitus, Sallust, Livy, Dion Cassius, Pliny, and Caesar reveal incidentally much that we wish to know. Gibbon gives some important facts in his first chapter. The subject of ancient machines is treated by Folard's Commentary attached to his translation of Polybius. Caesar's Commentaries give us, after all, the liveliest idea of the military habits and tactics of the Romans. Josephus describes with great vividness the siege of Jerusalem. The article on _Exercitus_, by Prof. Ramsay, in Smith's Dictionary, is the fullest I have read pertaining to the structure of a Roman army. For the narrative of wars, the reader is referred to ordinary Roman histories--to Livy and Caesar especially; to Niebuhr, Mommsen, Arnold, and Liddell. See also Durny, _Hist. des Romains;_ Michelet, _Hist. de Rom._ Napoleon's History of Caesar should be read, admirable in style, and interesting in matter, although a sophistical defense of usurpation. CHAPTER II. THE MATERIAL GRANDEUR AND GLORY OF THE ROMAN EMPIRE. To the eye of an ancient traveler there must have been something very grand and impressive in the external aspects of wealth and power which the Roman Empire, in the period of its greatest glory, presented in every city and province. It will therefore be my aim in this chapter to present those objects of pride and strength which appealed to the senses of an ordinary observer, and such as would first arrest his attention were he to describe the wonders he beheld to those who were imperfectly acquainted with them. [Sidenote: Culmination of Roman greatness.] It is generally admitted that Roman greatness culminated during the reigns of the Antonines, about the middle of the second century of the Christian era. At that period we perceive the highest triumphs of material civilization and the proudest spirit of panegyric and self- confidence. To the eye of contemporaries it seemed that Rome was destined to be the mistress of the world forever. [Sidenote: Extent of the empire.] [Sidenote: Square miles.] [Sidenote: Seas and rivers.] [Sidenote: Boundaries.] [Sidenote: Scandinavia.] [Sidenote: Sarmatia.] [Sidenote: Mountains.]