242 ^- k:otö. 



of the western brim of the Abukuma pLiteaii. CouiineiiciLig from 

 Miharu, and extending northwards, the outskirts of this region may 

 be found on the left side of the Abukuma-gawa near Nihon-niatsu. 



Examining tliis rock more closely with high powers, many in- 

 teresting facts are unfolded by the microsco[)e. The boundîiry between 

 the two granites is sharp and abrupt ; the encl(jsed rock is ^'ioiently 

 broken at its margin and terminates ^vilh keen edges, forming here 

 and there coves and inlets Avithin the confused mass, where the intru- 

 ding or younger granite has puslied its material through any free space. 



The intruding granite. — The younger granitic portitni is cpiartzose 

 at the junction, consequently it rarely happens that its components 

 other than quartz come in direct contact with those of the enclosed 

 rock (Fig. 1,^ PI. XXIII). The cpiartz is here variously fissured and 

 broken, and the lines of fracture thus pr(xluced run approximately 

 parallel with each other, tlieir prevaihng course being directed 

 ao-ainst the extended mari'-in of the enclosed rock. The quartzes at 

 the junction are dotted with swarms of liquid-inclusions which increase 

 in number as they appr(xtch the meeting points. It is usual among 

 contact phenomena to observe the develoi)ment of air and gas in- 

 clusions, which, contrary to our expectation, is not the case in the 

 present rock. The lëlds})ars rarely happen to meet directly with the 

 components of the enclosed granite. Where they do the feldspars 

 are not homogeneous, and intact ; the substance of the crystals is 

 crowded with [>atches of a colourless mineral, and consequently 

 the wliole aspect simulates the appearance of either andalusite or 

 staurolite with rich inter})Ositions of quartz. Some of these interposi- 

 tions of the feldspars may be of a negative character, made hollow 

 by some etching solvent along the plane of chemical weakness ; 



1 The lower half represents the intruding, young (Ijiotite-) granite, the upper half 

 the intruded, older (hornblende-) granite. 



