The Council of the Sydenham Society having deemed Hecker's three treatises on different Epidemics occurring in the Middle Ages worthy of being collected into a volume, and laid before its members in an English dress, I have felt much pleasure in presenting them with the copyright of the Black Death; in negociating for them, the purchase of that of the Dancing Mania, whereof I could resign only my share of a joint interest; and, in preparing for the press these productions, together with a translation, now for the first time made public, of the Sweating Sickness. This last work, from its greater length, and from the immediate relation of its chief subject to our own country, may be considered the most interesting and important of the series.