Tectonic Geography of Host era .Isia. — Ilobbs. 291 
Tlic ciiast l)riiip:s into most niarkrd expression llic ln'iidinjj of llic 
range so as to l)c concave to the south. As in the manner of its 
bending, so also in the abnndance of cmbayments, it is the opposite 
to that whicli we are accnstomed to see in tlie folded outer ranges 
of monntains of Alpine type. 
Of the Japanese arc, only the land which projects above the sea 
is shown. Whether compressed folded arcs lie in the slopes bordering 
the ocean or in its depth, is not to be determined. When I wrote the 
first parts: of these "studies," I considered it as probable, and con- 
jectured that througli concentration by folding a compensation would 
enter for the dilatation which has come aliout by reason of the tension 
toward the east. The analytical consideration of the structure in 
Japan has robbed me of the conviction. There is no trace of zonally 
folded arcs to be discoviered in the fundamental complex. In vain 
one seeks it in the Mesozoic deposits. Compressed folds may indeed 
be present in tlij eastward slopes toward the Tuscarora deep; but it 
is not probable that they surround Japan in arcs. The assumption 
would be better liased that they accomiiany the Ronin ridge upon its 
east side. 
8. Tltc Baiidai Arc of P'otcaiiocs is a recent expression of the arc- 
forming force. From the fracture field out of which it rises in a 
beautiful line, there have welled up, according to Harada, in Mesozoic 
time rocks of many types. Along with granites, which he had in- 
clined to ascribe in part to a late age, there were especially diorytes, 
quartz porphyries, and porphyr.ytes. A regularity in their arrangement 
cannot be made out. So much the more distinct is such an arrange- 
ment in the volcanoes which have been active since Tertiary time. 
Inclusive of Rischiri. Harada enumerated up to the Asama, 44 vol- 
canoes, of which 8 are still active. The fracture field from which they 
rise may have come into existence in AJesozoic time. The formation 
of the connecting canals with the earth's interior along the extended 
continuous line, and on certain scattered laterallj'-lying positions, was 
connected with later events. There arose thus the first independent 
arc structure within the region of the Japanese islands. It does not 
follow the axis of the island arc; for if the northern portion does 
indeed fall in the median line of North Japan, it nevertheless deserts it 
before i( reachs Asama; and if we follow its extension to the west 
where it is inserted in a most remarkable manner into an entirely dif- 
ferent mountain country', almost all of South Japan lies out.s^ide the 
line. It soon reaches the sea. In its prolongation lies, 3° farther west, 
the twin pair of the circular Goto group of islands, which arc in part 
volcanic ; yet one might venture to assume a connection. 
This arc has as little foundation in the structure of Japan as have 
the coast lines of the north wing. It obviously depends upon the forces 
which formed both, but it is in contra.st with them, independent by 
its very simplicity', and throughout a long cour.se. In it an analogy is 
furnished with the Aleutian islands and with the Kuriles. Since it 
rests upon the ancient arc as something foreign, one may speak of its 
connection with it as epigenetic. 
