THE GREAT ERUPTION OF SAKURA-JIMA IN 1914. 161 



Naka-daké Tlio eastern sleeve of the Minami-daké lava-field is 

 sheeted with a flow from the central eruption of Naka-daké, which 

 covers the eastern slope and marks also the coastal strip of 

 Nagasaki-hana or headland. The already -mentioned excentric 

 Nabé-yama and the minor Ebino-tsuka ringwall of 1471 sit upon 

 this base, as may be seen on Geologic Map. 



It should be remarked, that at the xA'esent state of the 

 writer's knowledge it is doubtful, whether it is practicable to dif- 

 ferentiate the Minami-daké and Naka-daké lavas or not. {See 

 Text-fig. 9, M.) The top-region is so thickly coated with blocks, 

 lapilli and ashes of historic and prehistoric eruptions that ex- 

 posures of underlying rocks cannot be seen, except at the deep 

 inaccessible radial gulches, which are few in number in this still 

 undissected volcano. 



On Geologic Map the hypothetic area of the Naka-daké lava 

 is brought to cartographic expression in order to suggest a problem 

 to be worked out in future researches. In passing, it is to be 

 remarked that there may be another point of efiusion of magma 

 near Nabé-yama, adjacent to its northwest skirt at a knob of 

 340 m. It is Gongén-yama, and it may be a part of the Kita-daké 

 or a volcanello belonging to it. 



b) Pétrographie Characters.— i. The specimens (PI. XVII. Fig. 3) 

 collected on the southeast slope between 300 and SOO m. are black, 

 dopatic and compact pyroxene- andésite. Phenocrysts (1.0-1.5 mm.) 

 of andesine plagioclase are abundant, but pyroxenes are as usual 

 scarce, of which prismatic hypersthene predominates a little over 

 anhedral augite. Phenocrystic pyroxenes are by no means easy to 

 distinguish and show abnormal features. Hypersthene is mostly 

 highly-birefringent, and augite is mostly pleochroic. Both have 

 exactly the same brownish green color. Prismatic section with 



