9ß6 B. KOTÖ. 



such a confused manner that within the microscopic field all possible sec- 

 tions of it may be seen, and hence the granular structure of the rock. 

 The hornblende is green at its margins, but light- brown at its centre ; 

 thus giving rise to zonings of colour of which, the peripheral, deep 

 shade is surely due to a slight change in the substance of the amphibole. 

 When the axis of mean elasticity ß coincides with tlie short diagonal 

 of the lower nicol, the differences in shade are inost marked, while in 

 the position at right angles to the former, i.e.^ c, the whole crystal 

 becomes greenish in C(jl<jur, and the zonings tlnis disappear. 



The interstices between the hornblende are occupied hy feldspar 

 crystals which appear quite homogeneous by simple light, while between 

 crossed niçois they are resolved into dot-like, minute grains imbued 

 with the feldspar substance, and the arms of the interference-cross sweep 

 round as the section is rotated, after the manner of a spherulitic 

 mass of chalcedony. It m;iy be fairly inferred from the optic;d deport- 

 ment of the rock that after its granulatioii and crushing, its temperature 

 was raised htj orogcnetic moceiiient so far as to partially melt the feldspar 

 into a more or less plastic mass, or else that a molecular rearrangement 

 took place in it at a comparativehj low temperature. The substance of the 

 feldspar is made dusty by accumulation of microscopic grains of 

 epidote and crystalloids of hornblende. Formless masses of an opaque 

 iron ore are plentiful, surrounded by a dull, white, granular ac- 

 cumulation, probably of leucoxene. 



t ) Tlie <jne occurring to the east of the last-mentioned, and near 

 the last house, the westernmost of Odaira, bx-allv called Sara^'ai, is a 

 medium-granular, massive I'ock of a dark-bluish colour, showing no 

 sig'ns of tissilitv. This 1 considered in the field to be a tine structured 

 variety of a gabbro and under the microscope I find it differs in no 

 essential point from this. The habits of the hornblende, magnetite, 

 and interstitial feldspar are exactly the same. The needles of secondary 



