ASSOCIATED METAMOKPHIC ROCKS OF THE LAKE-DISTRICT. 19 



arranged along bands, and the quartz grains are of various degrees 

 of fineness between them. The quartz contains great numbers of 

 liquid-cavities ; one of them in fig. 4 is enlarged three times the 

 rest of the figure ; and the small contained vacuity in this, as in 

 many other cases, keeps up a continual active movement to all parts 

 of the cavity, never going out of focus in any position. 



Pig. 5. represents the structure of the syenitic granite near its 

 border, at Scale Force. The quartz is generally not crystallized, 

 but interstitial and fall of minute liquid-cavities ; the base consists 

 almost wholly of felspar crystals, both plagioclase and orthoclase, 

 having a finely dotted appearance caused by innumerable very 

 minute cavities. Mica and a chloritic mineral occur, the former 

 scantily ; the latter, though very soft, is frequently taken for horn- 

 blende. Indeed, although hornblende does occur in some parts of 

 this rock, its presence generally is more than doubtful, especially in 

 an unaltered form * ; and therefore the term syenite, usually applied 

 to this mass, or even that of syenitic granite, is scarcely an exact 

 one. Although varying much in its character, yet, as it is distinct 

 from true granite on the one hand and from true quartz felsite on 

 the other, some distinctive name is needed. 



The somewhat doubtful green mineral is frequently accompanied 

 by patches of a black sabstance or iron-staining ; and it seems pro- 

 bable that this is in most cases due to a decomposition of the 

 mineral and peroxidation of the contained iron, the mineral thus 

 resembling chloropheeite. At any rate it seems certain that the 

 green mineral occurring so abundantly in the altered slate and 

 almost universally in the syenitic granite, is one and the same, or 

 different phases of development of the same group, that of the 

 chlorites or hydrous micas. Generally speaking, in the crystalline 

 rock, this greenish mineral occurs in larger flakes than in the 

 altered rocks. Thus, in the latter we have quartz and a hydrous 

 mica in some form, and in the former, quartz, both hydrous and 

 anhydrous mica f , and felspar. The bearing of this will be consi- 

 dered hereafter. 



The microscopic structure of the Buttermere and Ennerdale rock 

 necessarily varies somewhat over so wide a spread, though the 

 characters given above and the figure (fig. 5, PI. II.) contained in this 

 paper and that in the Survey Memoir (pi. i. fig. 6) represent the 

 prevailing structure. Sometimes, where the syenitic granite adjoins 

 the beds of the volcanic series, the transition rock is a hornblendic 

 felsite, collections of small hornblende crystals occurring in a fel- 

 sitic base. 



In some parts the quartz is much diminished in quantity, and the 

 soft green mineral is very abundant ; this gives the rock a dark tinge. 



4. Carrock-Fell Rocks. — We have already seen that the field- 

 examination led to the division of the Carrock-Fell rocks into three 



* Prof. Phillips remarks of this rock, "Barely distinct hornblende is obser- 

 vable " (Black's ' Guide to the Lakes'). 



t The ordinary micas, it will be remembered, contain small quantities of 

 water, but far less than the chlorite group. 



