numerous army, was indispensably requisite. Probus therefore judged it more expedient to defer the execution of so great a design; which was indeed rather of specious than solid utility. Had Germany been reduced into the state of a province, the Romans, with immense labor and expense, would have acquired only a more extensive boundary to defend against the fiercer and more active barbarians of Scythia.

Instead of reducing the warlike natives of Germany to the condition of subjects, Probus contented himself with the humble expedient of raising a bulwark against their inroads. The country which now forms the circle of Swabia had been left desert in the age of Augustus by the emigration of its ancient inhabitants. The fertility of the soil soon attracted a new colony from the adjacent provinces of Gaul. Crowds of adventurers, of a roving temper and of desperate fortunes, occupied the doubtful possession, and acknowledged, by the payment of tithes the majesty of the empire. To protect these new subjects, a line of frontier garrisons was gradually extended from the Rhine to the Danube. About the reign of Hadrian, when that mode of defence began to be practised, these garrisons were connected and covered by a strong intrenchment of trees and palisades. In the place of so rude a bulwark, the emperor Probus constructed a stone wall of a considerable height, and strengthened it by towers at convenient distances. From the neighborhood of Newstadt and Ratisbon on the Danube, it stretched across hills, valleys, rivers, and morasses, as far as Wimpfen on the Necker, and at length terminated on the banks of the Rhine, after a winding course of near two hundred miles. This important barrier, uniting the two mighty streams that protected the provinces of Europe, seemed to fill up the vacant space through which the barbarians, and particularly the Alemanni, could penetrate with the greatest facility into the heart of the empire. But the experience of the world, from China to Britain, has exposed the vain attempt of fortifying any extensive tract of country. An active enemy, who can select and vary his points of attack, must, in the end, discover some feeble spot, on some unguarded moment. The strength, as well as the attention, of the defenders is divided; and such are the blind effects of terror on the firmest troops, that a line broken in a single place is almost instantly deserted. The fate of the wall which Probus erected may confirm the general observation. Within a few years after his death, it was overthrown by the Alemanni. Its scattered ruins, universally ascribed to the power of the Dæmon, now serve only to excite the wonder of the Swabian peasant.

Among the useful conditions of peace imposed by Probus on the vanquished nations of Germany, was the obligation of supplying the Roman army with sixteen thousand recruits, the bravest and most robust of their youth. The emperor dispersed them through all the provinces, and distributed this dangerous reenforcement, in small bands of fifty or sixty each, among the national troops; judiciously observing, that the aid which the republic derived from the barbarians should be felt but not seen. Their aid was now become necessary. The feeble elegance of Italy and the internal provinces could no longer support the weight of arms. The hardy frontiers of the Rhine and Danube still produced minds and bodies equal to the labors of the camp; but a perpetual series of wars had gradually diminished their numbers. The infrequency of marriage, and the ruin of agriculture, affected the principles of population, and not only destroyed the strength of the present, but intercepted the hope of future, generations. The wisdom of Probus embraced a great and beneficial plan of replenishing the exhausted frontiers, by new colonies of captive or fugitive barbarians, on whom he bestowed lands, cattle, instruments of husbandry, and every encouragement that might engage them to educate a race of soldiers for the service of the republic. Into Britain, and most probably into Cambridgeshire, he transported a considerable body of Vandals. The impossibility of an escape reconciled them to their situation, and in the subsequent troubles of that island, they approved themselves the most faithful servants of the state. Great numbers of Franks and Gepidæ were settled on the banks of the Danube and the Rhine. A hundred thousand Bastarnæ, expelled from their own country, cheerfully accepted an establishment in Thrace, and soon imbibed the manners and sentiments of Roman subjects. But the expectations of Probus were too often disappointed. The impatience and idleness of the barbarians could ill brook the slow labors of agriculture. Their unconquerable love of freedom, rising against despotism, provoked them into hasty rebellions, alike fatal to themselves and to the provinces; nor could these artificial supplies, however repeated by succeeding emperors, restore the important limit of Gaul and Illyricum to its ancient and native vigor.