t 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 Daemon, 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 Gepidae were settled on the banks of the Danube and
the Rhine. A hundred thousand Bastarnae, expelled from their own country,
cheerfully accepted an establishment i