THE ARCH^AX FORMATIOX OF TITE AEUKUMA PLATEAU. OQJ 



apparently of the n.shes nud mud of* volr-niic ejeetameiitn, snh^ie- 

 qneiitly changed to the pi-e.^ent forni tlironuh varied dviiiuiii«' inctainor- 

 phisni. It is practically impossible to draw a hard and fast line 

 between the varieties they present; bnt altogether they form a litli(^logi- 

 cal continnity and a liarmonions wliole, -altliongh, when their extremes 

 are C()m])ared side by side, they a])pe.'!r at first siglit to ha\T. notiiing 

 in common with e;ich other. As I liave elsewhere ])oin1ed 

 ont, it is very interesting to n(^te that at the higher horizon 

 are fonnd the light- coloured and rather hard, moi'e comp;ict and 

 chl(.)ritic varieties, resembling an altered trap ; wlide tlie less liard, 

 perfectly fissile scliists crop ont at the basal portion, 'five graihial 

 changes which are observed between mnltifarions varieties a.[)pe!n' to 

 be due to the opera tioii of some canse, of the natnre of which notlung 

 certain can be at present made ont. 



I am not bold enongh to assert freely that snch l^asal, crystalline 

 members are the dynanio-metainorpliic prodncts of massive, syein'tic or 

 dioritic rocks, crushed and remodelled to the present form, as lias been 

 done by many great anthorities, who claim excessive and pro- 

 found effects for pressure-metamorphism. For them there are 

 properly no gneisses and mica- schists, but those derived by pressure 

 from massive rocks. Taught by the modern school of dislocation - 

 metamorphism, I was at first misled, while travelling through 

 the Abnkuma platean, last snmmer, to consider the amphi])ole scliists, 

 and even the gneisses and mica-schists to be crushed i)rodu(:-ts ; the 

 first derived from dioritic and syenitic rocks, the second and third 

 from granites. But gradually I became convinced that at least a part 

 of tJie Jionibleude scJùsts of tlie Gozaislio series is of prinian/ oriijin 

 (tliougli its exact mode of formation remains unknown), a)i(l iml a 

 product of the crusJiiiig e.jfect of a viass-movemi'nt of thr, eartlis crust. 



