and Igneous Rocks of Ensay. 91 



20 c W. These schists also resemble those at 1, but have 

 suffered more alteration in so far that in places the schistose 

 structure is almost obliterated in the finely crystalline- 

 granular mass, with quartz foliations, quartz veins, and veins 

 of felspar and quartz traversing it. 



I found a thin slice, which I prepared from one of the 

 most altered of the foliations in which the schistose structure 

 was not quite lost, to be composed of innumerable grains of 

 quartz fitting into each other and into the other minerals 

 like a puzzle-map. Among the quartz grains some are much 

 longer in the direction of the foliated structure than in the 

 other, and in some of these I observed to be included small 

 rounded grains of quartz. It has suggested itself to me that 

 in these included grains one raay perhaps recognise the 

 remains of the former clastic quartz grains of the sediments, 

 and in the larger ones surrounding them secondary quartz, 

 deposited during the metamorphic processes. This view 

 would require that the original quartz of the sediments 

 should, under such conditions, have been dissolved and 

 re-deposited. I shall later on return to this question, when 

 considering the principal and characteristic features of the 

 Ensay Rocks, which I am now describing in detail. 



The mainly siliceous mass of this rock is rudely parted 

 into foliations by irregular masses and connecting veins of 

 pinite, with a little brownish magnesia-mica, and its resulting 

 alteration to chlorite, which, as in other cases, has eliminated 

 ores of iron, to be re-deposited in the basal section of the 

 chlorite in the form of minute opaque black needles, crossing 

 each other approximately at angles of 60° and 120°. 



There are also felspars,, as angular grains, some of which 

 are orthoclase and others plagioclase. The former are 

 much altered, and in places completely, to pinite. The 

 latter are comparatively fresh, the only change which I 

 observed being the production of flakes of mica along cracks 

 and cleavage planes. These triclinic felspars are very com- 

 pound, according to the Albite law, and their low obscuration 

 angles suggest albite or oligoclase. 



At 28 occurs another outcrop of schists which have some 

 interesting features. Taken as a whole they are not siliceous, 

 but belong in great part to that section of the group which I 

 have spoken of before as pinite schist. 



The schists are very much contorted, and are penetrated 

 by veins of felspar and quartz, and also of crystalline- 

 granular materials. 



