344 VOLCANIC ERUPTIONS ON MARTINIQUE AND ST. VINCENT. 



and the process of valley tilling- continues. Water linding- its Avay into 

 these beds of hot debris, as already mentioned, causes steam explo- 

 sions, sometimes of such energy as to resemble a primar\" ei'uption 

 from one of the main or true craters. These eruptions at times hurl 

 larg-e quantities of debris into the stream channels which have been 

 partially cleared, thus producing dams and causing small lakes to form. 

 These water bodies rise until they overflow the accunudation of loose 

 material restraining them, when they are rapidly drained, and floods 

 of water heavily charged with debris occur below where the tempo- 

 rary dams were formed. The mud flows originating in these and 

 other similar ways have been frequent on both Martinique and St. 

 Vincent, and have in several instances been referred to as lava flows. 



Ero.von. — Much that is highly instructive centers about the manner 

 in which the surface waters are removing the freshly added material 

 from the surfaces of Martinique and St. Vincent. Instead of l»eing a 

 protection to the surface on which it rests, the fresh debris is in many 

 instances of assistance in its more rapid erosion. On steep slopes, and 

 even when the surface is nearly level, the rills formed during the 

 numerous tro})l('al showers quickly cut through the loose surface mate- 

 rial and, aided by the angular particles in suspension, corrade tlu^ soil 

 or rocks beneath. The rains, as it seems, are heavier than usual, 

 owing to two causes: First, the g-reat amount of water contril)utetl to 

 the atmosi)her(> as steam, and, second, the vast amount of dust l)lown 

 into the air, each })article of which serves as a center for condensation. 

 The process, of fashioning the topography throughout the extensive 

 areas from which all vegetation has been removed is greatly acceler- 

 ated. This more rapid erosion will, no doul>t, continue until the sur- 

 face is again plant-clothed. 



The volcanic eruptions have claimed so nuich iimnediate considera- 

 tion from the several geologists and geographers who have visited the 

 stricken islands that the indirect geographical changes resulting from 

 them have not received the attention they deserve. Not only the pul- 

 sating streams of steaming water and their occasional great discharges 

 of hot mud demand detailed study, but the way in which tlie undei'- 

 mining of l)aidvs of loose debris leads to landslides, the development of 

 consequent and subse([uent streams, the manner in which streams 

 develop and rapidly pass from youth to old age. etc., deserve to l)e 

 carefully recorded. The streams are not only eroding, but depositing. 

 Deltas are })eing formed and additions made to the land. The final 

 resting places of the fresh debris which fell on the islands will ))e in 

 the adjacent sea, where great <iuantities of fragmental volcanic mate- 

 rial is being spread out to form stratified tufl's. 



Tlyr/V'.v '/;/ tJie i<ea. — Reports have appeared in the newspapers, from 

 time to time since earl}^ in Ma}', of so-called tidal waves. As is well 

 known, the waves referred to have no connection wdth the tides, 



