THE GREAT EKUmON OF SAKURA-JDLA IN 1914. 213 



ß) Among the gray ancient rocks, there is a light-gray 

 rongh trachyte -looking éjecta. Under the microscope, weakly 

 pleochroic, old-looking hypersthene is enclosed by a peripheral 

 zone of brownish ' hornblende.' Gray apatite and tridymite were 

 also observed. This hornhlende-hypersthene andésite might represent 

 the mesa sheet above the lapilli lied of the Plateau Formation 

 (Younger Tertiary or Early Diluvium) of southern Kyûshû {Ax in 

 Text-fig. 3, p. 14). If the writer's supposition proves to be right, 

 the foundation of the volcano must bo assumed to be the Plateau 

 Formation, especially in taking into account the associated lapilli, 

 which have been described as the 'éjecta of trass.' >S^er^ page 214. 



/') Among the éjecta of the western slope, an angular grayish 

 enclave of secretionary origin was collected, which was caught up 

 in a mass of the Furuhata lava or the North Cone type. This 

 ' homogenous ' inclusion (PL XX. Fig. 5) has microlithic texture, 

 being built up of microlites of feldspar (1 mm. in length), divergently 

 arranged with polygonal spaces left between them, as if residual 

 glass leached out through a net-work of feldspar- skeletons. The 

 microscope reveals that augite crystallized ophitically with feldspar- 

 microlites, and the thin membrane of colorless glass stretches 

 between microlithic webs. This is called the ' structure enchevê- 

 trée ' (halter strap structure) by Laceoix.^^ 



o) There are some round blocks with black coating. They 

 are the disrupted fragments (Kita-daké type) of the mountain 

 body, that fell within the caldron of broiling lava and were again 

 thrown out in the proximity of the ventholes. The effect produced in 



1) ' La Montagne Pelée et ses énijations.' PI. XXX. Fig. 6. From Dr. Sidney Powers, the 

 writer received a specimen of olivine gabbro, taken from the walls of Kilauea, described by R. 

 A. Daly as a wehrlitic intriisive arching np ash bed after the manner of laccolith.- — ' Igneous 

 Rocks and Their Origin,' p. 76. On seeing a slide of it iinder the microscope, it shows the 

 structure enchevêtrée as in our secretionnry patches, although oli\'ine is wanting in the Saknra- 

 jima rock. 



