24 Vol. XLIII., Art. 6. — S. Tsnboi : 



lake, but was afterwards connected with the opon sea owing to 

 the collapse of its southern wall under a seismic tidal wave that 

 attended the earthquake on November 2ord, 1703 (the r2th year 

 of the Genroku era). 



Hikubo (3e) lies about 1 km. to tlie west of Habu. This 

 is a spot hemmed in by a horse- shoe shaped wall open to 

 the southeast. Tliis wall, consisting of éjecta and having a 

 height of about 50 rn., may also be due to a plueatic explosion. 

 As to the age of its formation, it must be very young, for its 

 original form is preserved without any modification in spite of its 

 easily destructible and loose structure. 



If phreatic explosion is due to the heating of surface water 

 by intrusive magma, as is generally believed, the presence of these 

 craters, Habu and Hikubo, indicates that the magmatic intrusion 

 came near the surface in t.liis part of the island. 



The Sea Cliflf Opposite to Fadeshima.'^— For about 1,000 m. 

 along the coast opposite to Fudeshima (3d) in the south part of 

 the east shore, there is a sea cliff about 170 m. high. This is the 

 only cliff that was formed at the foot of that part of the fault 

 escarpment along the east coast (p. 16), which remained uncovered 

 by later volcanic materials. On the southern half of the cliff a thick 

 accumulation of blocks of lava is exposed, with pétrographie 

 characters similar to those of the first type of the somma lava (p. 

 13) but free from olivine ; while on its northern half a thick accu- 

 mulation of red and brown scoriae belonging to the same pétrographie 

 type is visible. Numerous dykes of olivineless basaltic bandaite 

 (sempatic with phenociysts of basic plagioclase scattered through 

 the compact gray grouudmass of comparatively high crystallinity 



1) ^^ 



