olS Y. KIKUCHI. 



amount of water is no doubt due to this alteration. Loc. 



Söri in Ködsuke. 

 IL, is the same as I., but with all the visible crystals of Cordierite 



removed. 

 III. is the ordinary unaltered slate. Loc. near Grödo in Ködsuke. 

 From these few analyses nothing quite certain can be asserted. 

 It may be pointed out. however, that the relative amount of silica is 

 less in the altered slate with Cordierite than in the unaltered one 

 without any Cordierite, allowing that there was no very great difference 

 in the original character of the two slates taken for the analysis. On 

 comparing II. and III., we see that the altered slate approaches, on the 

 whole, to the normal slate by the partial removal of the Cordierite 

 crystals. It is probable that by the process of contact alteration, 

 the slate was made basic by the addition of the Cordierite-silicate. 



The Cordierite-bearing slate presents a very characteristic ap- 

 pearance in virtue of the elongated fusiform sections of the crystals 

 irregularly scattered in the gênerai ground-mass. Further, on 

 closer observation, rounded six-sided sections may often be 

 detected. In weathered pebbles which have long been exposed 

 to atmospheric action in river-beds, &c., the erystals are more 

 readily recognizable than in the freshly fractured surface, on account 

 of the fact that natural corrosion has been more active on them than 

 on the surrounding mass, so that they are often found depressed at 

 the exposed surface. They are also stained reddish-yellow by the iron 

 hydroxide, which has probably partly resulted from the oxidation of 

 the Iron-pyrites which they contain (Fig. 7). In those specimens, 

 however, which have undergone more or less metasomatic alteration, a 

 greenish tinge is always observable, resembling the pseudomorph from 

 Tatnba. Sometimes stellate aggregates, which are probably due to 

 tiwn -groups, are observed (Fig. 8). As the form of such aggregates 



