424 The National Geographic Magazine 



within it are no doubt different, and as 

 yet but little evidence concerning the 

 gases that may have been present during 

 the times of most violent activity has 

 been obtained. The most that can be 

 accepted in this connection is: a plainly 

 perceptible odor of sulphurous acid no- 

 ticeable in the air even at a distance of 

 some 8 miles at sea, when the volcanoes 

 were in a comparatively mild state of 

 activity, and while walking over the 

 debris they showered on their respective 

 islands. A much fainter odor of sul- 

 phureted hydrogen is reported to have 

 been present, as for example, among the 

 ruins of St Pierre, but whether due to 

 gas emitted from the volcano or arising 

 from organic matter buried beneath the 

 still hot debris is not clear. The pres- 

 ence of carbon dioxide, although as- 

 serted or surmised to have been dis- 

 charged during the greater eruptions, 

 has not been proven. The consideration 

 of all the available evidence points 

 strongly to the conclusion that steam 

 was the chief vaporous or gaseous sub- 

 stance emitted, but mingled with it were 

 minor quantities of sulphurous and no 

 doubt other gases. 



In the above connection it should be 

 noted that flames above the summit of 

 both Mont Pelee and La Soufriere have 

 been reported by several trustworthy 

 witnesses. If the appearances referred 

 to were in reality flame, and not glowing 

 dust or the reflection of the light from 

 incandescent rocks on vapor, it is evi- 

 dent that inflammable gases were pres- 

 ent. No spectroscopic observations seem 

 to have been made, however, and until 

 this is done the evidence as to the pres- 

 ence of inflammable gases in notable 

 quantity must seemingly be received 

 with caution. 



The reports that Mont Pelee and La 

 Soufriere discharged mud are probably 

 correct so far as would appear from 

 a distance, yet the true meaning would 

 seem to be that such eruptions were 

 of the nature of the explosions in the 



pseudo-crater or in the true craters 

 during intervals between the eruptions 

 from a deep source. Hot dust and 

 lapilli accumulating in a crater during 

 quiescent stages would furnish most 

 favorable conditions for the producing 

 of superficial explosions where rain oc- 

 curred or springs entered a crater from 

 its sides, as has been observed, and 

 would produce eruptions similar to 

 those of the pseudo-crater, and mud 

 flows might result. It is evidently not 

 to be inferred that either of the vol- 

 canoes 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 varying in size from those 

 weighing in the neighborhood of one 

 thousand tons to the finest of dust 

 particles. The fragmental material is 

 of two classes : First, fragments of the 

 rocks torn from the walls of the con- 

 duits through which the upward rush 

 of debris-charged steam occurred; and, 

 second, fragments of hardened lava 

 which had been forced upward into the 

 conduits in a plastic condition and 

 shattered and blown out by the escap- 

 ing steam. In addition to the angular 

 fragments of fresh lava, minor quanti- 

 ties of more or less spherical masses of 

 similar material, which were projected 

 into the air while yet moderately plastic, 

 have also been observed. While the 

 term volcanic bomb has been applied to 

 much of the ejected material, it is evi- 

 dent that only the somewhat spherical 

 masses referred to deserve to be so 

 called, and even in such instances there 

 is doubt as to the propriety of using the 

 term . Typical volcanic bombs have a 

 round or oval form, with extended and 

 spirally twisted projections at the ends 

 of the longer axis, the spherical or 

 more commonly oval form and the 

 spirally twisted extremities being due 

 to the rotation of the mass during its 

 aerial flight and while 5-et plastic. No 



