﻿Reviercs — Lyman\ Geology of Japan. 525 



single section showing the geological relations of the formations, 

 and this is the more strange because it would appear that ample 

 materials for rough ones at least have been collected. 



In connexion with his rock groups, our author, too, seems to 

 place more importance than necessary upon the directions in which 

 the beds are folded, the folds of different regions, or of the same 

 region with different axial directions, being thought to mark different 

 periods of disturbance, without the collateral testimony of uncon- 

 formity or distinct superposition, or much other conclusive evidence 

 being adduced to prove difference of age, either of the rocks them- 

 selves, or in their systems of disturbance. 



The oldest group of the Island of Yesso is the Kamaihotan (or 

 Home of the Gods) subdivision, a series of metamorphic quartzites, 

 talcose and quartzose schists, blue marble, and blackish serpentine, 

 with greenish impure limestone, granites, and mica schist. So far 

 as we have gathered, these rocks are all distinctly stratified, they 

 contain no fossils, and are sharply contorted with steep angles of 

 dip from 45° to 60° or more. They form the core of the island, and 

 any mineral veins they contain traverse also rocks of the next newer 

 stage, so that it is doubtful if they contain any peculiar to them- 

 selves — even the gold of the superficial deposits not being excepted. 

 These metamorphic rocks are of unknown age. 



Next newer than this is the Horumui group, containing very 

 numerous, but for the most part thin or impure beds of coal, with 

 some good coal, having but a small per-centage of ash, and some 

 ' furnishing ' coke of good appearance. The rocks are chiefly sand- 

 stones of greenish or grey colour and grey shales or clays. The 

 fossils found have been few, and not carefully studied; but the rocks 

 are thought to be of early Tertiary or possibly of late Secondary age. 

 In probably the lowest beds a Ptychoceras and some Ammonites 

 have been obtained. This group is more than double the thickness 

 of any other. 



Conformably succeeding these, apparently, though this is not dis- 

 tinctly stated to be the case, is a group of Old Volcanic rocks, 

 trachyte porphyries, with small crystals of glassy felspar, taken to be 

 of late date, because of their rhyolitic character. Light grey, coarse- 

 grained syenite occurs in them at several places, and diorite less 

 frequently. These rocks, it is supposed, may have partly issued from 

 volcanos that still send out new volcanic rocks. 



Then comes the TosJdbets group, possibly locally conformable and 

 passing into that preceding. In this group Mr. Munroe distinguished 

 two divisions, the upper of clays, sandstones and pumice, or other 

 conglomerates derived wholly from volcanic rocks, and the lower 

 of shales, sandstones and conglomerates. Between the two he thought 

 at one place he detected an unconformity, though there was none 

 elsewhere. 



Derived pebbles of syenite and other crystalline rocks in these 

 beds, supposed to have come from the Old Volcanic group, -would at 

 least suggest more of unconformity than is stated to exist. 



One bed, 500 feet or so from the top of the group, contains fossil 



