102 B. KOTO 



resemblance to that of the so-called ' Grilnscliiefer System ' of 

 Saxony, that when hand-specimens from both countries are placed side 

 by side, it is hardly possible to distinguish them, nor are there any 

 special distinguishing features even under tlie microsco})e. 



Slides show that, under high power«, each spot is nothing but 

 an individual grain of felspar, or composed sometimes of many 

 grains. These felspar-dots are all, without exception, of an irregular 

 outline, and present a characteristic cataclastic structure. They 

 are colourless, showing quite a fresh aspect — only a few stripes; 

 twins referable to the Carlsbad type occasionally found — polysynthetir 

 twins exceedingly rare. 



(1) The writer is of opinion that this rock is a transformed schist 

 from a tup' oï a felspar-pyroxene rock of an eruptive origin ; and (2) it 

 is an accepted dogma that, when minerals are subjected to a certain 

 pressure, they usually exhibit many traces of cleavage (although all 

 minerals have not as yet been experimentally tested); and lastly (3) a 

 mechanical force can put in motion the molecules of minerals so as to 

 make the particles assume a. new position, the result of which is the 

 formation of twdns, gliding faces, etc. — it is, indeed, very striking to 

 find only a few such traces of cleavage in ou.r felspar, although the 

 rock bears signs of having been subjected to pressure in the mass- 

 movement. 



A probable explanation of these facts may be that the felspars 

 have once been in a condition, in which a long-sustained pressure 

 and moderate heat, wdth the simultaneous presence of mineral solutions, 

 have made the molecules in the felspars to move easily bnt <^nly to a 

 certain extent. The same reasoning may well be applied with equal 

 force to the formation of schists, which have an appearance as if they 

 were farmed by the solidification of an originally gelatinous mass in 

 the diagenetic way (vide page 85.) 



