BY M. AUROUSSEAU. 299 



are slightly deeper, however, and all trace of their secondary 

 pyroxene has been removed, while the granular magnetite is 

 greatlv decomposed. Apatite and primary magnetite are in- 

 cluded; in one case, hornblende appears to have grown in parallel 

 position with pyroxene (represented by a pseudomorph). 



Biotite is in about the same amount as hornblende, and has 

 suffered greatly by resorbtion. 



Pyroxene is represented entirely by pseudomorphs. These are 

 generally of clinochlore, carbonate, and quartz, but in three cases, 

 grains of acid plagioclase, with undulose extinction, enter into 

 their composition. Magnetite and apatite are included. 



Magnetite includes apatite, and is passing into limonite. Zircon 

 is comparatively abundant, but apatite is scarce. 



One minute, rounded grain of quartz was observed. It is 

 undoubtedly primary, being corroded by the groundmass. 



The groundmass is greatly clouded by limonite and chlorite, 

 and is, in patches, entirely replaced by chlorite. Fluidal fabric 

 is feebly developed. As in (108), it is a holocrystalline, fine- 

 grained mosaic of plagioclase more acid than the phenocrysts. 



In all its primary, and most of its secondary characters, this 

 rock is the exact counterpart of (108). The differences are of 

 degree, rather than of kind. 



In a more weathered specimen of the same rock, hornblende 

 is represented by pseudomorphs of allotriomorphic plagioclase 

 which approaches albite in composition, all indices of refraction 

 being lower than Canada balsam. The extinction of the grains 

 is sometimes undulose, and they enclose strings and patches of 

 very finely granular epidote, as well as the apatite-inclusions of 

 the original hornblende. The entire aggregates are surrounded 

 by the reaction-rings of magnetite, which express the character- 

 istic outlines of the hornblende. 



In the same specimen, the larger biotites enclose numerous 

 grains of secondary albite, in poikilitic fashion. 



A slide of this rock was treated with hydrochloric acid in 

 order to remove limonite; the chlorite-pseudomorphs of pyroxene 

 were noticed to have lost colour, contracted, and become almost 

 isotropic, after the treatment. 



