The Black Death and its after-effects will occupy a large part of this work, so that what has just been said of it will not stand as a bare assertion. But the plague in the reign of Justinian hardly touches British history, and must be left with a brief reference. Gibbon was not insensible of the part that it played in the great drama of his history. “There was,” he says, “a visible decrease of the human species, which has never been repaired in some of the fairest countries of the globe.” After vainly trying to construe the arithmetic of Procopius, who was a witness of the calamity at Byzantium, he agrees to strike off one or more ciphers, and adopts as an estimate “not wholly inadmissible,” a mortality of one hundred millions. The effects of that depopulation, in part due to war, are not followed in the history. So far as Gibbon’s method could go, the plague came for him into the same group of phenomena as comets and earthquakes; it was part of the stage scenery amidst which the drama of emperors, pontiffs, generals, eunuchs, Theodoras, and adventurers proceeded. Even of the comets and earthquakes, he remarks that they were subject to physical laws; and it was from no want of scientific spirit that he omitted to show how a plague of such magnitude had a place in the physical order, and not less in the moral order. A new science of epidemiology has sprung up since the time of Gibbon, who had to depend on the writings of Mead, a busy and not very profound Court physician. More particularly the Egyptian origin of the plague of the sixth century, and its significance, have been elucidated by the brilliant theory of Pariset, of which some account will be given at the end of the chapter on the Black Death. For the present, we are concerned with it only in so far as it may have a bearing upon the pestilences of Britain. The plague of the sixth century made the greatest impression, naturally, upon the oldest civilized countries of Europe; but it extended also to the outlying provinces of the empire, and to the countries of the barbarians. It was the same disease as the Black Death of the fourteenth century, the bubo-plague; and it spread from country to country, and lasted from generation to generation, as that more familiar infection is known to have done[1].