THE CJREAT ERUPTION OF SAKUEA-JIMA IN 1914. 187 



What is stated in the preceding as the distinctive features of 

 lavas on both sides of Sakura-jima is subject to rectification when 

 additional shdes can be examined, especially with regard to the 

 statement on the groundmass. 



0^ 



B. The Loose Ejecta. 



Under this heading are embraced those loose volcanic éjecta - 

 monta which are of pecuUar interest, and some of wliich are new 

 to science, as may be learned from the following enumeration : 



1) Volcanic scum.^^ 



2) Gabbroids as éjecta. 



3) Ceramicites, natural porcelain 



éjecta. 



4) Solid ejected blocks of juvenile 



lavas. 



5) Bread-crust bombs. 



6) Recent lapiUi. 



7) The porpliyritic obsidian. 



8) Pseudobombs of ancient lavas. 



9) Ejecta of trass or ash-stone. 



10) The so-caUed sandstone. 



11) Ejected blocks of biotite- 



granite. 



12) Coal. 

 1) Yolcanic Scum.— By the term, volcanic or ' lava scum ''•* 



1) On account of the presence of a large quantity of cordierite, the whole group of the 

 scum or froth should be better consigned to that of ceramicites, which name the writer ven- 

 tures here to proi30se. 



2) It should not be confounded with the so-called ' spongy thread-lace glass scoria,' descri- 

 bed by Dana in his " Characteristics of Volcanoes," p. 163, and by I. Friedlaender in Zeitschrift 

 fur Vulkmiolorjie, Bd. I. Tafel XXHI. Bilder 20 und 21. The genuine thread-lace scorLa was, 

 however, ejected from Asama in the eruption of October, 1914. The scoria is of large size, snow 

 ■white, and hght like soap-bubbles. Microscopically, it has a peculiar sponge-like structure with 

 .spicxiles regularly arranged forming a framework of the light mass. The same frothy scoria was 

 blown up from the Yimo-hiia vent during the first phase of the recent eruption. It is of 

 large size, measuring up to half a metre in diameter. 



The thread-lace scoria has recently been a subject of much discussion. F. A; Perret saw 

 this Kilauean scoria lying upon the pahoehoe lava in a continuous stratum, indicating formation 

 in situ, and therefore not to be included under the head of ejectamenta (' Some Kilauean Ejecta- 

 menta.' Am. Jour. Sei., Vol. XXXVI. 1913, p. 617). S. Powers is of opinion that this scoria, a 

 variety of basaltic pumice, is a kind of gaseous lava-froth blown out of craters and not formed 

 in situ on the surface of the jjahoehoe flows. Moreover, he defines the scoria as a gaseous 

 pumice where the vesicles are separated only by slender threads instead of walls (' Explosive 

 Ejectamenta of Kilauea.' Am. Jour. Sei., No. 243, 1916, p. 240). The thread-lace scoria seems 

 not to bo exclusively a kind of basaltic pumice ; for, the writer found it, as cited above, among 

 the recent éjecta of Asama and Sakura-jima, which are built up of pyroxene-andesites. 



