36
THE
ERUPTION
OF
PELÉE
so frequently the lofty pennant was shot in a straight line entirely through the zone of the trade-winds, as m a n y of m y photographs show, and perhaps even through the zone of the anti-trades, naturally proves that, at certain times at least, the propelling power was responsible for the full or nearly full height t h a t the cloud attained. I n the chapter on " T h e Geography of Mont Pelée" of m y work " M o n t Pelée and the Tragedy of Martinique" I have stated t h a t it appeared to me t h a t not only were the eruptions taking place from the summit of the new cone t h a t had been erected over the floor of the basin of the Étang Sec, b u t also from stillexisting parts of this ancient floor, and I ventured the assertion t h a t the destructive blast of August 30 m a y have had its origin here, rather t h a n in the chimneypot. I was led to this conclusion b y the violence of the steam eruptions coming from the great depths of the crater, and their gradual crowding over to the side turned to Morne Rouge—the location whence seems to have issued the explosive tornado of May 8. This view seems also to have been shared b y Professor Lacroix, who observes (Comptes Rendus, October 27, 1902, p. 673): " I t would appear t h a t it is from the interval between the walls of the crater and the base of the cone, as well as from the flanks of the cone itself, t h a t the columns of gas and vapors, a t times of calm, ascend vertically to prodigious heights ( " I l semble que c'est de l'intervalle situé entre les parois du cratère et la base de ce cône, ainsi que des flancs de celui-ci que sortent actuellement les colonnes de gaz et de vapeurs qui, les jours de calme, montent verticalement a une hauteur prodigieuse"). The plate (decimaprima, 28a) illustrating the eruption of Vesuvius in 1767, and contained in the "Gabinetto Vesuviano" of Delia Torre (1797), perhaps represents the same form of double synchronic activity. Quantity of Ash-Sediment Discharged.—No determination of the quantity of ash thrown out b y Pelée during its various eruptions can have more t h a n a speculative, or at best, a roughly approximative value. Much the greater p a r t of it was distributed over the sea, and at times, for days in succession, this quantity was prodigious. The near-by localities during this period may, on the other hand, have received b u t little of the ejected material. The late Professor Israel C. Russell, in a paper on the "Volcanic Eruptions on Martinique and St. Vincent" (National Geographic Magazine, December, 1902), a t t e m p t s to give mathematical expression to this quantity b y assuming t h a t the contents of an energetic Pelée steam-cloud rising to three or four miles was about 4,000,000,000 cubic feet, and t h a t such a cloud was charged a t its minimum with one per cent., or 40,000,000 cubic feet, of solid m a t t e r . I t was further assumed t h a t every such cloud was regularly replaced a t intervals of five minutes b y another cloud (the rate of ascent here considered being about three-quarters of a mile per minute, which is very much less than I found it to be on August 30, 1902). Hence, the discharge of solid m a t t e r from the crater would have been in every five minutes 40,000,000 cubic feet. I n all of these d a t a I believe t h a t Professor Russell has understated, rather t h a n overstated, the conditions as t h e y existed, and perhaps very much so, b u t they serve as an