586 Y. OINOUYE 



and the breaking of the bubble at the surface. After the cessation 

 of the mud flow the surface dried and sun cracks were formed. 

 The gases near the surface rapidly escaped through these openings, 

 but those imprisoned near the bottom of the mass were unable to 

 do so, the upper part only having dried out. Later, by the coales- 

 cing of the small bubbles, the remaining gases united beneath the 

 surface in reservoirs of greater size. The accumulated pressure 

 finally became great enough to force a passage through the mud to 

 the surface, the sudden escape of the gas forcing the mud upward 



Fig. 3. — The largest "puff" cone. Photo taken by the writer, May 16, 1912 



to form cones. The other mud flows in this district, being thinner, 

 dried out more rapidly, and no cones were formed. 



The writer has been unable to find descriptions of any such 

 phenomenon in the case of other mud flows, although similar 

 elevations occasionally occur on lava flows. He therefore suggests 

 the name "puff cones." 



No new cones were formed after the summer of 191 2, the greater 

 part of the gas having been expelled. Since that time weathering 

 has begun to reduce the slopes, so that, in all probability, no trace 

 of this fantastic phenomenon will remain after a few years. 



