238 ^- ^OTo. 



light it shows imdulatory extiDCtioris. Moreover, the whole substance 

 is composed of fine grains wliich are only made visible by the difference 

 of the optical orientation of the several fragments*. Between the 

 epidote zone and the biotite the space is still occupied by a feldspar, but 

 besides this, needles of epidote shoot across from the granular zones 

 into the substance of chloritic fibres (Fig. 4, PL XXIII). The forma- 

 tion of the secoudary epidote is due evidently to the reaction of hiotite and 

 feldspar. 



As to the state of aggregation of the individiip.l com] »orients, 

 I have to add only a few remnrks. I have already ypoken nhout the 

 structure of the imperfectly schistose granite, which is mainly due to a 

 slight shifting of the coloured components, and this fact may be readily 

 made out from the deformation of their crystal lographic outlines. In 

 the present case the schistose structure is more perfectly developed than 

 the one just referred to, and is distinctly fibrous-lamellar, resembling 

 somewhat the structure known as the " eye "-gneiss. 



Under the microscope the hornblende and biotite are seen to be 

 not only flattened and compressed, but the entire crystals were material- 

 ly altered into chloritic filtres, leaving here and there only cores of 

 hornblende and scanty remains of lamella? of mica. Sometimes the 

 decomposition has gone so far that a few epidote grains alone indicate 

 the spot which both minerals once occupied, but nothing of their sul>- 

 stance can now l)e seen. More than this, the allotriomorphic quartz, 

 filling up the s])ace left vacant by other components, is for the most 

 part crushed, presenting a mosaic by polarized light. Simultaneous!}^ 

 with this granulation, the quartz fragments have been shifted one over 

 the other, penetrating into wedge-shaped interstices wherever they 

 have been allowed to do so. The feldspar is the most obstinate of all 

 the components, standing solidly in its original position, while other 

 ingredients have partaken of the general decompositions and migra- 



