40 Notices of Memoirs — Granites, 8fc., Lalce Temiscaming, Canada. 



Paradis Point, and varj'ing in breadth from half a mile to one mile. 

 The whole area thus underlain by the granite is approximately about 

 six square miles. 



Macroscopically the fresh rock is a rather coarse, though very 

 uniformly even-grained aggregate of felspar, quartz, and a dark- 

 coloured mica, probably biotite. Felspar is by far the most abundant 

 constituent, and the abundance of red oxide of iron disseminated 

 through all the cracks and fissures of this mineral gives to the 

 rock its beautiful deep flesh-red colour. The quartz is, as usual, 

 allotriomorphic, but a decided tendency is noticed to segregate in 

 more or less rounded areas or individuals which, especially on 

 surfaces worn and polished as a result of glacial action, gives to the 

 rock a porphyritic or pseudo-conglomeratic appearance ; a fact first 

 made note of by Sir William Logan in 1844 on his manuscript map 

 of this portion of the Ottawa river. 



The microscope shows the rock to be composed essentially of 

 orthoclase, microcline, plagioclase (oligoclase?), quartz, and biotite 

 almost completely altered to chlorite. The microcline has evidently 

 been derived from orthoclase as a result of pressure, and all the 

 gradations of this change may be noted, from the " moire structure " 

 characteristic of the imperfectly or only partially developed mineral, 

 to the fine and typical "cross-hatched structure" peculiar to this 

 mineral. The felspar shows only incipient alteration to sericite, and 

 scales and flakes of this mineral are developed especially abundantly 

 in the central portion of the individuals, leaving a comparatively 

 fresh periphery almost altogether free from such decouiposition 

 products. 



The arkose with which this granite is associated and surrounded is 

 a beautiful pale or sea-green quartzite or grit, passing occasionally 

 into a conglomerate, the pebbles of which are chiefly grey and red 

 quartz with occasional intermixed fragments of a halleflinta-like rock. 



Under the microscope the finer-grained matrix appears to be 

 almost wholly composed of pale 3'ellowish-green sericite in the form 

 of minute scales and flakes, although occasional individuals are 

 macroscopically apparent. Most of this sericite has originated from 

 the decomposition in situ of felspar originally present, and irregular 

 portions or areas of the unaltered felspar may be occasionally 

 detected. 



The line of junction between this granite and arkose shows 

 a gradual and distinct passage outward or upward from the granite 

 mass. The series of thin sections examined, as well as the hand- 

 specimens themselves, show every stage in the process, which has 

 been carefully studied. 



In the first place, as a result of dynamic action, the orthoclase is 

 converted into microcline with the incipient development of sericite, 

 which gradually increases in those specimens where the greatest 

 perfection of the " cross-hatched " microcline structure is reached. In 

 these the individuals of quartz and felspar have undergone rather 

 extensive fracturing, but with little or no movement apart of the 

 fragments. This breaking uj) of the original larger individuals is. 



