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DECLINE OE THE

CHAP. VII.

arising from the irruption of the barbarous tribeswhich surrounded the empire. The new minesalong the borders of the Danube in Dacia, thoseof Illyria, Dalmatia, and Thrace , were the firstto suffer from this cause, which the emperors,either from the weakness of their forces, or theexhausted state of their treasuries, were unableto prevent. The workmen in the mines eitherfell as captives into the hands of the invaders,and were thus removed from the districts, or 1they were induced by the sufferings they en-dured to enlist with the Barbarians, and to aug-ment their means of annoyance to the empire.

By these events some of the mining provincesbecame gradually depopulated, and in othersthe workings were by degrees abandoned, as theexhaustion of the products of the more preciousminerals had caused the expense of separatingthem far to exceed the value that could beextracted. This exhaustion of the more valua-ble contents of the mines had produced theabandonment of those in the east and in Spain ;where other nations had gathered the first-fruits,and left to the Romans neither the first, thesecond, nor the third harvests. From these well-known circumstances, and from the silence ofall the writers of a later period concerning the

1 See Gibbon’s Decline and Fall, cap. xxvi. p. 393, wherehe describes the miners of Thrace conducting the Barbariansto secret magazines of corn and cattle.