212 ART. 3. — B. KOTÔ : 



liodral olivine is accessorily found. The dominant groundmass is 

 colorless pure glass, and pniniceous. 



In short, the eastern lapiUi are of comparatively basic nature, 

 corresponding to the massive lava-flows, as has been already empha- 

 sized elsewhere (p. 184). 



7) Porphyritic Obsidian (PL XXIII. Fig. 4). — The single specimen 

 of porphyritic obsidian found was picked up from among the c^jecta 

 on the east side at an altitude of 400 m. It is a compact pitch- 

 black vitreous glass dotted with grayish lustreless specks of plagio- 

 clase. Slides show abundant and seriate plienocrysts of plagioclase 

 and a subordinate amount of pyroxenes (augite>hypersthene), besides 

 magnetite clumps in a brownish damascened glass, — a texture re- 

 sulting from kneaded and compressed air-pores as in the figure. 

 In a certain homogeneous portion of brown glass, brownish axiolites 

 and colorless crystallites are found in fluidal arrangement. A 

 substance similar in texture to obsidian occurs as coating of trass 

 (PL XXIII. Fig. 3, and Text-fig. 4G, p. 215) and other projectiles. 



8) Pseudobombs of Ancient Lavas.— There are éjecta, though 

 quantitatively insignificant, of ancient lavas of various shape and 

 size, more or less rounded through subaërial mutual abrasion, which 

 may appropriately be called pseudohomhs. Their common feature 

 is the ash-gray color ; but the texture varies from compact and 

 tabular to somewhat scoriacoous. 



«) One kind consists of hypci^sthcne- andésites, and their petrogra- 

 pliic character is the same as the Kita-daké type, to which the 

 reader is referred for details (pp. 155-158). Specimens were only 

 picked up on the western slope. During the earlier explosive phase 

 vents were rent through the rock of which the western slope is 

 built, and the ruptured resurgent fi^agments were thrown up among 

 the juvenile lavas. 



