been a discovery of any one individual, would deserve to be considered as the very greatest ever made; and he adds acutely, in answer to the obvious, but shallow objection to it (viz. its apparent assumption of equal ability for reigning in father and son for ever), that it is like the Copernican system of the heavenly bodies,--contradictory to our sense and first impressions, but true notwithstanding. CHAPTER VI. To return, however, to our sketch of the Cæsars--at the head of the third series we place Decius. He came to the throne at a moment of great public embarrassment. The Goths were now beginning to press southwards upon the empire. Dacia they had ravaged for some time; "and here," says a German writer, "observe the shortsightedness of the Emperor Trajan." Had he left the Dacians in possession of their independence, they would, under their native kings, have made head against the Goths. But, being compelled to assume the character of Roman citizens, they had lost their warlike qualities. From Dacia the Goths had descended upon Moesia; and, passing the Danube, they laid siege to Marcianopolis, a city built by Trajan in honor of his sister. The inhabitants paid a heavy ransom for their town; and the Goths were persuaded for the present to return home. But sooner than was expected, they returned to Moesia, under their king, Kniva; and they were already engaged in the siege of Nicopolis, when Decius came in sight at the head of the Roman army. The Goths retired, but it was to Thrace; and, in the conquest of Philippopolis, they found an ample indemnity for their forced retreat and disappointment. Decius pursued, but the king of the Goths turned suddenly upon him; the emperor was obliged to fly; the Roman camp was plundered; Philippopolis was taken by storm; and its whole population, reputed at more than a hundred thousand souls, destroyed.