32 Y. KIKUCHI 



crystal-ejections near tlie crater of a volcano. A case analogous to 

 that here described is met with in the eruptions of Vesiivins; crystals 

 of Leucite wliicli there play tlie role of Felspar, h.-ing sometimes 

 esjected. Tims Leucite eruptions continued from April 1845 to 

 January 1849, according' to Scacchi,* who considers these well- 

 defined Leucite crystals as beino; derived from the refusion of the 

 crystals already formed in tlie older lava within the volcano. 



From the basic character of the Anorthite it is to be inferred that 

 it had early crystallized out of the magmn, and that the crystals thus 

 formed were ejected while the latter was still in a liquid condition ; 

 the heavier crystals falling near the crater, while the lighter portions 

 of the ejected matter were carried further off. On this account, they 

 have always a thin vesicular coating of lava, the interi(»r however 

 remaininnf uniniured. 



Similar kinds of crystals have also been broujjht from the other 

 islands of the Shichitö Chain, viz. Oshima (Yries Lsland) and 

 Hachijö. 



Most of the specimens of lava, which I have seen are of a black 

 colour, and have a porphyritic structure, mostly porous but some- 

 times very compact. The porphyritic ingredients are Anorthite- 

 crystals of the Microtine type, and Olivine, usually in the form 

 of rounded grains, and very rarely showino- crystal-f)rm, as S. v. 



CD / •' * O « ■ 



Waltershausen t observed on the Olivine in the lava of Etna. A coat- 

 ing of red iron oxide is always f nmd on these Olivine grains, often 

 assuming a brilliant metallic lustre. Microscopically examined, the 

 ground-mass is seen to consist of a microcrystalline airsrreofate of 

 Felspar and Magnetite, with sometimes microcrystals of Apatite. 



* Ueber den Ursprung der vulkanisclien Asche. — Anszu» by Rammelsberg in Zeitschft. d. 

 dentscb. geol. Gesellschft. Bd. 24. 187'2. p. 5J8. 

 t Vulkauische Gesteine in Sicilien ixnd Island, p. 161, 



