Reviews — Geological Survey of Yesso, Japan. 465 



Older and stratified formations appear to form the basis or founda- 

 tion for the volcanic formations. , At Ota, on the west coast, granitic 

 and metamorphic rocks, in well-defined outcrops, form a rugged 

 coast. In the interior they form the principal watershed, and give 

 rise to many rivers, in the beds of which gold is found in deposits 

 which can be profitably worked. These metamorphic strata are 

 uplifted, and generally trend northwest and southeast, and show 

 flexure and bending exactly as in other and better known regions. 

 Slates, sandstones, and limestones are found also at Esan, Shuokobi, 

 and near Kakumi, and at the lead mines of Ishinowatari and Urup. 

 The rocks at the two last-named places are not as much uplifted and 

 metamorphosed as the granitic and auriferous rocks, but they are 

 probably parts of the same series of formations. The only recog- 

 nizable fossil found is apparently a fragment of a Calamite, leading 

 me to suspect that the beds are of Carboniferous age ; but this is by 

 no means certain, and although diligent search was made no other 

 evidence of the age of these formations could be found. Near Iwanai 

 there are beds of good coking coal in strata that have no lithological 

 resemblance to the auriferous series, but they are uplifted at a high 

 angle. Fossils apparently of Cretaceous or Jurassic age are found 

 in the eastern part of the island. 



The next stratified formation of interest is marine Tertiary or Post- 

 tertiary, which rests unconformably upon the older stratiiied beds, 

 and is highly charged in some places with well-preserved fossils 

 scarcely distinguishable from the mollusca now existing upon the 

 coasts. In these deposits, and in later terrace-like formations, there 

 is abundant evidence of the comparatively recent uplift of the whole 

 island, and the same evidences are found upon the island of Nipon. 



Dynamically, the formation of greatest interest is without doubt 

 the volcanic conglomerate and the associated beds of finer volcanic 

 materials. They record the most energetic volcanic action at an early 

 period before the recent uplift, for it is almost certain that the mass 

 of the conglomerate was deposited under water. It seems as if there 

 had been a series of violent subaqueous eruptions, perhaps at the 

 time the tiow-existing cones began to be formed. It is most probable 

 that the island has been gradually formed by the rising of these 

 separate cones above the sea, thus giving at first a group of islets, 

 each a volcano, similar perhaps to those which can now be seen off 

 the coast and at the entrance to the Bay of Yeddo. One is repre- 

 sented opposite the western coast on the Japanese maps. 



leiE ^V"IE AAT S. 



Geological Sukvey of Yesso. 



IT may be news to some readers of the Geological Magazine to 

 learn that there is a Geological Survey in progress in Japan ; but 

 the fact is recalled by the appearance of the " Preliminary Eeport on 

 the Pirst Season's Work of the Geological Survey of Yesso," the large 

 northern island of the group, by Mr. Benjamin Smith Lyman, an 

 American Mining Engineer of experience, a few years since specially 



DECADE II. — TOL. I. — NO. X. 30 



