20
THE
ERUPTION
OF
PELÉE
it be told if any structural relation in fact existed, although I strongly suspect t h a t it did. B u t t h a t the more newly appearing structures were in themselves of no mean significance is proved b y the observation t h a t on November 25 one of the needles lost 30 metres of its height as the result of the eruption of t h a t day.* At t h a t time the greater p a r t of the dome was incandescent. I n comparing the Pelée dome (not the obelisks, spires, or processes) with resembling structures elsewhere, the geologist naturally turns to the two or three anomalous types of cone or summit t h a t have become known for their departure from the form of the normal volcano. These are the domed cone of Giorgios, already referred to, which appeared on the island of Santorin in l866; some of the Puys, as the P u y Chopine, of the Auvergne region of France; and (perhaps most remotely) the pyramidated tops of volcanoes which Stübel has described from among the equatorial Andes. The last-named structures, how ever, so far as I am able to comprehend Stübel's work, are seemingly only physio graphic monuments associated with the original making of the volcanoes, and have nothing in common with a later crateral d i s c h a r g e . †They belong to the type of Stübel's monogenetic and not polygenetic volcano. A closer approxima tion to the Pelée dome is probably to be found in the dome-structure, first noticed in 1895, and more fully developed in the spring of 1898, which Matteucci has described in connection with late outbreaks of Vesuvius (preceding the great eruption of 1906). Matteucci's studies are recorded in a number of very care fully prepared p a p e r s , ‡which leave little room to doubt the substantial accu racy of the observations presented. We learn from these reports t h a t the dome (or cupola lavica) gained in one m o n t h (February 14 to March 15, 1898) 15 metres in altitude, the floor of the crater swelling u p (intumescing) at the same time to 50 metres. The total height of the dome was represented to be 163 metres. Matteucci sees in this upheaval the combined action of a deeply planted mechanical force and of a superficial intumescence, and he does not fail to recognize the conditions which are thought to be associated with the making of laccolites.§ There would probably be no impropriety in desig nating the Vesuvian structure " laccolitic," even if it represents no true laccolite. T h a t the Giorgios dome, the t y p e of the cumulo-volcano, is essentially representative of the structure seen in the later stage of the Pelée dome, as * L'Opinion. †This seems also t o be t h e view held b y H a n s Meyer: " I n den H o c h - A n d e n von E c u a d o r , " 1907, p p . 286-287. T h e p y r a m i d of Quillinada, in E c u a d o r , is t h o u g h t b y Meyer t o give evi dence of solidification a n d e x t r u s i o n suggestive of t h e crateral p a r t s of Pelée (pp. 276, 286). ‡" Sur les P a r t i c u l a r i t é s de l ' É r u p t i o n d u V é s u v e , " Comptes Rendus, 1899, vol. 129, p p . 65, 66; " Sul Sollevamento endogeno di u n a Cupola lavica al V e s u v i o , " Rendicont. Accad. Scienze Fisiche e Matemat. Napoli, 1898, xxxvii., p p . 285 et seq.; " Se al Sollevamento endo geno di u n a Cupola lavica al Vesuvio possa aver c o n t r i b u t o la sol indicazione del M a g m a , " Bollet. Soc. Geol. Roma, 1902, xxi., p p . 413 et seq. § " S i t r a t t a di u n o Sforzo mecanico profundo e di u n a I n t u m e s c e n z a superficiale," Rendi cont., Nap., p. 299.