THE ARCH^AX FORMATION OF THE ABUKUMA PLATEAU. 265 



I confess that I am totally unable to distinguish quartz from 

 feldspar when their orains are thrown together in a mosaic aggregate ; 

 but judging from the massive, feldspar-hornblende rock, from which 

 presumably the present one seems to have been derived, I naturally 

 deny the presence of quartz. It is particularly misleading that the 

 huyer crvstals of feldspar, which must have been and still must be sub- 

 ject to peculiar strain l)y pressure in such a metam(jrj)hic rock, display 

 polarization-colours of so high order as to lead one readily to take them 

 for quartz ; but from time to time a few stripes of different (-olours may 

 be noticed, which point to the latent existence of twins in the feldspar. 

 In saying so, my notion is not strictly to preclude the presence of quartz, 

 as this is reasonably supposed t(3 l^e formed in the metasomatic changes, 

 which any rocks, especially of eruptive origin, may suffer during an 

 orogenetic movement of the mass. I simply mean that grains which 

 may beyond doubt be regarded as quartz have not been observed. The 

 bluish hornblende bears evident mark of having been produced in some 

 secondary wjiy in its sherif-like fjrm, frayed at both ends and tufted 

 together in acicular bundles. Minute grains oï epidote (3ccur mixed 

 with accumulation of magnetite. 



e) The rock lying east of, and conse(|uently (jverlying, the meta- 

 morphic schist just described, is a massive, fine-granular, green rock 

 without an}' fissile stru^-ture in a hand-specimen, though a few rock- 

 cleavages might be found in natural exposures. It appears like a 

 rock altered under the influence of cont;ict action of some eruptives. 

 The surface is speckled with white dots, esp>ecially on weathered speci- 

 mens, indicating the presence of much feldspar. 



The granular structure of the rock may be better understood 

 by examining a slide with the microscope, it is seen to be mainly 

 made up of hornblende in ragged, sheaf-like or fibrous masses, frayed 

 out at the ends into radiating tufts. The hornblende is disposed in 



