45 6 The National Geographic Magazine 



ently is fiesh. All the particles are 

 coated with dust, which seems to be as 

 fine as any that fell during the Ma3' 

 eruptions. Since the cloud from the 

 September 3-4 eruption of La Soufriere 

 is reported to have produced darkness 

 for about six hours at Fort de France, 

 Martinique, on September 4, it is prob- 

 able that the fine dust of this eruption 

 was thrown higher into the air than was 

 that of the May eruptions, and was car- 

 ried northward, away from St Vincent, 

 before it settled. 



Such great accumulations of hot lapilli 

 and dust as those in the valleys of the 

 Wallibu and Rabaka Dry rivers retain 

 their heat for a long time, and they 

 have given rise to secondary or super- 

 ficial eruption phenomena of striking 

 character and considerable interest. The 

 river water and the water from the trop- 

 ical showers percolating through the 

 beds have come into contact with the 

 still highly heated interior, causing 

 violent outbursts of dust-laden steam. 

 We saw one of these outbursts from 

 the Wallibu Valley send up a column 

 of such vapor fully a mile in height. 

 The action lasted for nearly an hour, 

 and followed directly after a heavy 

 shower. 



In the morning of May 30, which was 

 clear and dry, we witnessed the throw- 

 ing of a dam across the stream and the 

 formation of a temporary lake by a 

 heavy secondary outburst of dust-laden 

 steam from the lapilli bed in the Wal- 

 libu Valley. This eruption must have 

 been caused by percolating river water, 

 since there had been no rain for at least 

 eighteen hours when it occurred. After 

 the eruption ceased the little lake soon 

 rose to the top of the dam and quickly 

 cut its way down to the old level, send- 

 ing a "mud-flow" down the gorge to 

 the sea. Such a lake in the valley of 

 the Rabaka Dry River cut its new outlet 

 through a narrow ridge of the old ag- 

 glomerate constituting the wall of the 

 canyon, forming as it did so a beautiful 



series of channel bowls, pot-holes, and 

 scratched corkscrew channels. 



When we first reached St Vincent the 

 dust, especially that covering the Rich- 

 mond estate, showed in marked manner 

 the wind-drift surface so familiar in the 

 case of freshly fallen snow, and in many 

 places these drifts were from three to 

 four feet deep. There were several 

 heavy rains between May 24 and 29, so 

 that the appearance of the surface was 

 very different on May 30 from what it 

 was when I first saw it. Its drifted 

 character was not nearly as evident, 

 and the beautiful dendritic drainage, 

 which was already in evidence on May 

 24, had been greatly extended and in- 

 tensified. Geological operations, which 

 under ordinary conditions are so slowh T 

 performed as to be imperceptible, were 

 being carried forward rapidly under 

 our very eyes. One item of interest 

 was the action of the Wallibu River 

 itself as it cut into and undermined 

 the beds of dust and lapilli along 

 its banks. Its waters became so over- 

 loaded with sediment that they could 

 only flow in pulsations, showing that 

 intervals of time were needed by the 

 stream to gather strength to force its 

 way along with its burden. On May 24 

 these waves or pulsations were from 

 fifteen to forty seconds apart.* Such 

 mud streams carry large boulders down 

 their beds and have great erosive power. 



When the great cloud of ejecta rose 

 from La Soufriere at 2 p. m., May 7, 

 the portion which was traveling east- 

 ward seemed suddenly to split, accord- 

 ing to the accounts of eyewitnesses, 

 when it was some distance beyond the 

 island, and to send a part back to the 

 land. This is in accord with the fact 

 that unprotected windows in the east- 

 ern side (that farthest from the crater) 

 of houses in the devastated district along 



*This peculiar action of the Wallibu was 

 first described by the author in a letter pub- 

 lished in the New York Times of June 29, 

 1902. 



