564 POPULAR SCIENCE MONTHLY 



Bishop of Ostia, as Leo Ostiensis, one of the most sober and important 

 of Italian historians; the ' Annales Cavenses' (569-1318), 9 produced 

 by another famous monastery near Salerno ; and finally the ' Chroni- 

 con ' ( 1102-1140) 10 of Falco of Benevento, notary, judge and papal 

 chancellor, to whom posterity is indebted for precious information. 

 These contemporary sources contain all that is known of the ninth and 

 tenth Vesuvian eruptions. Details are wanting, but it is said of the 

 former that it happened in January, 1037, and lava flows reached the 

 sea; the duration of the latter (1139) is stated in one account to have 

 been eight, in another, forty days. Critical estimates of the documents 

 above referred to will be found in various works dealing with the 

 sources of medieval history, amongst which it will be sufficient to men- 

 tion an article by Hirsch on ' Desiderius of Monte Cassino.' 11 Our 

 review of the chronology of eruptions in the early middle ages is now 

 completed. 



There remains to be considered a question that has often been 

 asked, and variously answered : was the form of Somma- Vesuvius essen- 

 tially the same in antiquity as we know it to-day, or were the ancients 

 acquainted with only a single crateriform summit whose broken wall 

 now partially encircles the newer cone? The only reason for raising 

 the inquiry at all is that neither by direct statement nor by implication 

 do any of the ancient authors allude to Vesuvius as a double-peaked 

 mountain, and the older topographic descriptions can with difficulty be 

 reconciled with the present form of the volcano. It appears indeed 

 passing strange that Strabo, Pliny, Cassius Dio and Procopius should 

 all have remained silent respecting the most salient feature of Vesuvius 

 as viewed from the west, in case its twin peaks presented to their eyes, 

 as they do to ours, almost identical outlines. Yet, accepting their 

 accounts at face value, the only conclusion possible is that the younger 

 cone has been entirely built up during the middle ages, a far shorter 

 interval than is demanded by geologic evidence. A time allowance of 

 barely a thousand years (or at the most fifteen hundred, if we leave 

 Procopius out of the reckoning and admit the correctness of Leone di 

 Ambrogio's figure of a double summit in 1514) for the formation of the 

 central cone is absurdly inadequate, the number of eruptions con- 

 tributing towards it too few, and their intensity too slight, to have 

 performed the work. This we know from the present slow rate of 

 accumulation, and from the relatively unimportant changes wrought 

 by even paroxysmal eruptions. And it may well be doubted whether 

 the convulsion of 79 A. D. was of more violent character than those of 

 1631 and 1906, these three exceeding all others in intensity. 



"Ibid., Vol. III., p. 189. 



10 Muratcri, R. I. 8., Vol. V., p. 128. 



11 Forsch. deutsch. Gesch., Vol. VII., 18G7, pp. 1-112. 



