214 



GEORGE CARROLL CURTIS 



to Martinique on June 14, and for the elongated hill of hot bowl- 

 ders between the 600 and 700 foot level in the Seche valley/ by 

 secondary eruption. 



Co7npariso7i of ash-geyser cones with other secondary volcanic cones. 

 — These cones, occurring as they do within the valleys and upon 



Fig. 12. — Secondary ash cone topography. Rabaka river. Vents slightly 

 " steaming " with mere trickle of water in stream bed. 



the "mud lavas," may be compared with those irregular heaps 

 of volcanic scoriae which abound on the tops of some true lava 

 streams, being piled up around each vent or "bocca" which the 

 steam-jets escaping from the lava currents, form at their surfaces. 

 The Vesuvian lavas of 1855 and of 1872 developed such cones 

 on their surfaces.^ 



Ash-cone topography . — I was at first unable to account for the 

 peculiar irregular topography in the channels of the streams 

 soon after the great eruptions. It had the irregular rounded 

 hillock appearance which resembled sand-dune forms. The sug- 



' HovEY, Bull. American Museum, Vol. XVI, p. 360. 

 ^JUDD, Volcanoes, p. loi, drawing by Schmidt. 



