Yolcano Ôshima, Idzii. 71 



of whom the writer is much indebted. The analysed specimen 

 was nearly holocrystalline, consisting of calcic bytownite, labra- 

 dorite, diopsidic aiigite, and magnetite, with a negligible amount 

 of olivine. This specimen has been selected for analysis because 

 it belongs to the most widely spread type of the somma lavas, 

 while being nearly holocrystalline, as stated, it consequently affords 

 a correlative comparison of its mineralogical and chemical characters. 

 The result of the chemical analysis is as follows : — 



Total 99.87 



Osann's formula. 



6 = 58.12 ^ = 2.52 e=C.80 i^= 23.24 



a = 1.55 c = 4.18 /= 14.27 



n=8.70 k = 1.12 



Norm. 



Quartz 9.6 



Orthoclase 2.8 



