so much of a human soul on record as to raise up for himself in each generation a fresh series of friends and admirers.
With the death of Marcus Aurelius this phase of unity and comparatively good government came to an end, and his son Commodus inaugurated an age of disorder. Practically the empire had been at peace within itself for two hundred years. Now for a hundred years the student of Roman history must master the various criminology of a number of inadequate emperors, while the frontier crumbled and receded under barbarian pressure. One or two names only seem to be the names of able men: such were Septimius Severus, Aurelian, and Probus. Septimius Severus was a Carthaginian, and his sister was never able to master Latin. She conducted her Roman household in the Punic language, which must have made Cato the elder turn in his grave. The rest of the emperors of this period were chiefly adventurers too unimportant to the general scheme of things for us to note. At times there were separate emperors ruling in different parts of the distracted empire. From our present point of view the Emperor Decius, who was defeated and killed during a great raid of the Goths into Thrace in 251 A.D., and the Emperor Valerian, who, together with the great city of Antioch, was captured by the Sassanid Shah of Persia in 260 A.D., are worthy of notice because they mark the insecurity of the whole Roman system, and the character of the outer pressure upon it. So too is Claudius, "the Conqueror of the Goths," because he gained a great victory over these people at Nish in Serbia (270 A.D.), and because he died, like Pericles, of the plague.
Through all these centuries intermittent pestilences were playing a part in weakening races and altering social conditions, a part that has still to be properly worked out by historians. There was, for instance, a great plague throughout the empire between the years 164 and 180 A.D. in the reign of the Emperor Marcus Aurelius. It probably did much to disorganize social life and prepare the way for the troubles that followed the accession of Commodus. This same pestilence devastated China, as we shall note in § 4 of this chapter. Considerable fluctuations of climate had also been going on in the first and second centuries, producing stresses and shiftings of population, whose force historians have
