260 



B. KOTO. 



muscovite-aggregate but with some part intact on the periphery. The 

 rest of the rock-mass is built up of quite unchanged, colourless 

 feldspars with some grains of quartz, which on account of the jjarallel 

 position of the dark-br<3wn biotite assume a more or less wavy 

 structure. Only a few grains of the feldspars exhibit twinning 

 lamellation between crossed niçois ; consequently it is difficult to say 

 whether we have to do with plagioclastic or monoclinic varieties, but 

 probably the porphyritic feldspar belongs to the latter family. A 

 black, highly lustrous iron-glance may be observed, but not titanite. 

 The specimen here described comes from Söri ; but this gneiss might, 

 no doubt, be found in many other places by close examination in 

 the field. 



YII. Petrography of the Gozaisho Series. 



A. AmphihoUtes of the Gozaisho Boad. 



We are in the hal)it of allowing so wide a latitude to amphibolite 

 or hornblende-schist, that the name alone gives scarcely any clue as 

 to the real nature of the rock a petrographer denotes by it, for the term 

 amphibolite which includes rocks differing greatly in their external 

 appearance and the nature of their component-minerals, as well as in 

 their genesis, that is, whether they are metamcjrphic schistose diorites 

 or really stratified schists. Therefore, it will be Avell here to give 

 certain prominent features which eminently characterize our rocks, 

 with the view of distinguishing them from the titanite-amphibolites 

 of the Takanuki series, already sufficiently described. 



Besides the "Teat difference which exists between the horizon 



o 



of the rocks I am now describing, and that of the other series, 

 the following points are to be mentioned : 1) Perfectly fissile, evenly 

 plane-parallel structure is to a certain extent common to the rocks 



