ox THE SO-CALLED CRYSTALLINE SCHISTS OF CHICHIBU. 13P> 



licfls. the fe]sj)ai*-o-raiii8 are, as a rule, scanty, since that mineral is 

 easiJy decomposable. Avhen romparcd with others of the sandstone- 

 components. From this fact, our arkose graywacke seems to ditfer 

 somewhat as regards its origin from common rocks of the same 

 name. The writer is rather inclined to consider its components to 

 have been derived from the assorted ejectamenta of volcanic activity 

 which occurred during the Sambagawan epoch in the same manner 

 as at present, or even on a grander scale. A similar deposit is now 

 being formed along our shores, as may be seen from the samples 

 of sand dredged up from near the Marine Biological Station of the 

 Imperial University at Misaki at the entrance of the Bay of Tokyo. 

 The younger eruptives near the Station being mostly non-quartzose 

 pyroxene andésite, the dredged samples consist only of gi'ains of pyr- 

 oxenes, and triclinic felspars, the finer particles of the ejected materials 

 being removed by the sorting action of waves. The normal sericite- 

 schist and epidote-sericite-gneiss already referred to might have been 

 changed from the arkose graywacke-sandstone, the latter having been 

 formed in the manner just described. 



Again, the chlorite-amphibole-schist of the Middle Sambagawan, 

 alternating witli the graphite-sericite-schist, seems to have been 

 changed from the unsorted, nuiddy, volcanic ejectamenta deposited in 

 a shallow sea, rather than to have been the product of a r-rushino- 

 in siUi of zones of the original coarse-grained rock.^) The result of 



1) Association of the gneissic and other schistose rocks with igneons masses and also the 

 siuiilarity of the mineral components in all liave often been taken, not with full justice, as 

 proofs, that they wore orig-inally of the same rock-variety and have even been said to 

 form the same mass of one geologic age; and this is the current view of lithologists in the 

 modernage of the theory of (U'<loc<iliiiii-)iirt(iiiinrjilil^iji in geology. This may be partially 

 true. But it is, however, not !ess reasonable to suppose that the schistose rocks might be 

 tuffs of igneous masses occurring in the vicinity, and they are, of course, respectively most 

 nearly related in mineral composition. Tlie absence or presence of stratification, or folin- 

 tion-xtratifieation can only decide the case; but to ascertain which is really developed in 

 individual cases is a paiustaking tnsk, niid errors are apt to creep in in such an observation, 

 giving rise sometimes to differences of view, not easily reconcilable. 



