Phenomena of Vesuvhis. 47 



in Italian, of that just mentioned. The new eruption in the 

 month of October last, not only one of the most considerable 

 which have occurred since that so celebrated in 1794, but 

 even of the grandest which have ever been witnessed, having 

 presented to the authors an extensive field for new experi- 

 ments and observations, induced them to resume and enlarge 

 that work by the addition of two sections, a preface, a table of 

 contents, and figures. 



The most remarkable of the principal facts contained in this 

 work, are enumerated by the authors themselves in the pre- 

 face. These are the formation of earthy pisolites among the 

 pulverulent lava ; the particular and oblique ejection of a fine 

 sand, or, as it is vularly named, volcanic ashes, which also 

 produces small and extremely singular currents, having at a 

 distance the appearance of streams of hot water ; that of other 

 currents formed entirely of substances much more bulky, but 

 equally incoherent; the examination made with new and peculiar 

 interest of the discontinuance or intermission, and of the par- 

 tial fits of the eruptions, which are compared by the authors to 

 the paroxysms of violent diseases ; the positive observation of 

 sulphurous acid, and of sulphur itself, in the lava which has 

 ceased flowing; that of carbonic acid in fumeroles of lava, 

 before it is completely cold, and especially of a considerable 

 evolution of this acid, after great eruptions, giving place to 

 large and numerous mnfcttcs which are manifested around the 

 base of the mountain. This fact is so remakable and of such 

 importance, that the celebrated Sir Humphry Davy thought 

 that it might lead to the discovery of the origin of the various 

 calcareous rocks in which volcanic substances are contained, 

 either in cavities or in the substance of the rocks them- 

 selves. 



Among the newly recognised productions of Vesuvius, will 

 be remarked the sulphates and chlorides of manganese, which 

 characterize a number of saline metallic sublimates, and the 

 existence of which in the mineral kingdom has been hitherto 

 unknown. This work likewise offers several considerations con- 

 cerning the diversity of temperature, which the different volcanic 

 vapours require in order to their attaining a solid state. The 

 veracity of Pliny the younger, in the description he gives of 

 the eruption which occasioned his uncle's death, has been fre- 

 quently questioned; but MM. Monticelli and Covelli prove, 

 by comparing several passages of his relation with the effects 

 which they have themselves observed, that he is entitled to 

 complete confidence. They have also observed the formation of 

 the last cone, and seen it gradually disappear in part, in the same 

 manner as that which, according to the description of Strabo, 



existed 



