Eruptions on Martinique and St Vincent 423 



St Pierre. Near view of one of the holes. The material of the tanks is quarter- 

 inch boiler iron (see page 425) 



From a photograph by Dr E. O. Hovey. Republished from the Bulletin of the American 



Museum of Natural History 



■ owing to relief of pressure as it rises, 

 the steam dissolved in the molten 

 magma escapes with tremendous vio- 

 lence. There are thus two sources for 

 the steam which furnish the energy dis- 

 played in the summit portions of ascend- 

 ing lava columns — one from the rain and 

 percolating water, and the other from 

 a deeper but unknown source. But 

 this attempt to follow the volcanic con- 

 duits downward in fancy has brought 

 us to the region of speculation and it 

 is time to stop, at least for the present. 



To the four types of volcanic-steam 

 columns described above, a fifth might 

 be added to include volcanic explosions 

 like that of Krakatoa. 



Products of the Eruptions. — The mate- 

 rial discharged from Mont Pelee and 



Ua Soufriere may be divided into two 

 portions : First, steam and gases, and, 

 second, solid rock debris. Up to the 

 present time no observations indicate 

 that molten rock has been extruded ; 

 that is, no lava streams have flowed 

 over the surface from the crater of 

 either volcanoes or issued from fissures 

 in their sides. 



As to the discharge of vast volumes 

 of steam, there is no difference of opinion 

 to be formed in the various reports al- 

 ready rendered. Observers who have 

 visited the craters from which the recent 

 eruptions came, and have even ventured 

 within them, report only faint traces of 

 gases. The conditions, however, be- 

 tween the time when a crater is quies- 

 cent and when violent explosions occur 



