VOLCANIC ERUPTIONS ON MAKTINIQUK AND ST. VINCENT. 337 



jsumnut of ))oth Mont Pelee and La Soiifriere have been reported h}" 

 several trustworthy" witnesses. If the a])pearances referred to were 

 in realit}' tlame, and not glowing dust or the reflection of the light 

 from incandescent rocks on vapor, it is evident that inflammable gases 

 were present. No spectroscopic observations seem to have been made, 

 however, and until this is done the evidence as to the presence of 

 inflammal)le gases in notable (quantity must l)e received with caution. 



The reports that Alont Pelee and I^a Soufriere discharged nuid are 

 proba))ly correct so far as would appear from a distance, yet the true 

 meaning would seem to be that sucii eruptions were of the nature of 

 the explosions in the pseudo-crater or in the true craters during inter- 

 vals l)etween the eruptions from a deep source. Hot dust and lapilli 

 accunudating in a crater during quiescent stages wouhl furnisli most 

 favorable c(nKlitions for the producing of superficial explosions where 

 rain occurred or s})i-ings entered a crater from its sides, as has been 

 observed, and would produce eruptions similar to those of the pseudo- 

 crater, and nuid flows might result. It is evidently not to be inferred 

 that either of the ^'olcaIloes in question has erupted mud from a 

 deeply seated source. 



The solid matter discharged from Mont Pelee and La Soufriere is 

 almost entirely in the condition of angular fragments ^■arying in size 

 from those weighing in the neighborhood of 1.000 tons to the rinest 

 of dust particles. The fragmental material is of two classes: First, 

 fragments of the rocks torn from the walls of the conduits through 

 which the upward rush of debris-charged steam occurred; and, second, 

 fragments of hardened la\a which had JK'en forced upward into the 

 conduits in a plastic condition and shattered and blown out by the 

 escaping steam. In addition to the angular fragments of fresh lava, 

 minor quantities of more or less si)herical masses of similar material, 

 which were projected into the air M'hile yet moderat(dy plastic, have 

 also been observed. Wliile the term volcanic bomi) has been a})plied 

 to much of the ejected material, it is evident that only the somewhat 

 'spln'rical masses referred to deserve to Ix^ so called, and even in such 

 instances there is doubt as to tlu^ pi'oi)ricty of using the term. Typ- 

 ical \olcanic bombs ha\'e a round or oval form, with extended and 

 spirally twisted proj(>ctions at the ends of the longer axis, the spher- 

 ical or more connnoidy oval form and the spii'ally twisted extremities 

 being due to the rotation of the mass during its aC-rial flight and while 

 yet plastic. No projectiles answei'ing this description lia\'e as yet 

 been reported as occuiring on Martini<|ue or St. \'incent. The near- 

 est ap})roa('h to a characteristic bond) are certain rud(dy s])herical 

 masses of lava with ci-acked surfaces (fig. 2, PI. IIJ) and without ])i'o- 

 jectionsoi- indicationsof a sjjiral twist. L\'identiy thesis ])oorl\- sha[)ed 

 ))ombsare conq)osedof fresh lava which was sufliciently hot to make it 

 somewhat ])histic at the time it was blown into the air, l)ut was too 



SM 1902 22 



