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T is certain that Vesuvius, prior to the Plinian eruption of 79 A. D., by far the most tragic, and one of the three most violent in Italian history, was regarded as an entirely extinct volcano. The details of this eruption, the sequence of its phenomena, and its peculiarly destructive effects, are familiar to us from contemporary sources, and from the memorials written in large characters by the mountain itself over the ruined cities at its base. From the date cf this catastrophe onward for over fifteen hundred years, when the period of modern investigation begins, our knowledge of Vesuvian history depends upon more or less casual mention, and upon brief notices of eruptions in monastic chronicles.

Owing to the scantiness of our information, little attention has been paid by students to the long interval separating the two most violent paroxysms known to have shaken the mountain. Yet, inadequate as the records are, their importance is of the first order. They register for us the dates of major disturbances, at least, extending over a period of sixteen centuries, and afford some means for estimating the intensity of volcanic action in the Naples district for a still longer period. Moreover, they furnish data for reconstructing the probable form of the mountain in antiquity, and for detecting the amount of change it has undergone since Plinian times. Nor should it be forgotten that the early topographic descriptions that have come down to us offer interesting points of comparison with the present condition of the stately guardian of the Bay of Naples.

Thus it appears that the original sources of information, which are all that need concern us in the present article, acquaint us not only with the actual history of Vesuvius since the first century of our era, but, taken in connection with other facts, throw a fresh coloring upon the accounts of the 'burnt mountain' that have survived from classic times. Two of the points just enumerated will repay further inquiry: first, the chronology of eruptions during the early middle ages; and secondly, the probable form of Somma-Vesuvius in antiquity. One reason why a review of the chronology seems desirable is because the dates of medieval eruptions are often confused, and the authorities for them incorrectly given, or more frequently omitted. It will be profitable, therefore, to take a brief survey of the original sources, but without