372 The American Geologist. December, 1904. 
and west, which with the Philippines have together been desig- 
nated as the Malayan Archipelago. In taking up for consider- 
ation this remaining portion of the region, the tectonic sketch 
map of Fig. i will serve for orientation. It has been construct- 
ed from several maps. On the main land of Asia the great ser- 
ies of arcs and the dominant lines of faulting have been entered 
from von Richthofen's studies. The tectonic lines sketched in 
for the Korean peninsula and about the gulf of Pechili are from 
dominating ones which appear upon the maps of Koto and von 
V. Cholnoky. The volcanic zones and the arcs in Japan have been 
taken from the new official map of Japan issued by the Japan- 
ese government and from v. Richtofen's sketch map, and the 
last mentioned author has been followed in Formosa and the 
Riukius. In the Philippines and other portions of the Malayan 
Archipelago the data have been furnished by the maps of Suess 
and Koto. The volcanic zone to the eastward from the Malayan 
Archipelago is entered from Berghaus's excellent Atlas der 
Geologic. 
Riukin Arc: The island of Formosa and the island arc 
which connects it with Japan (Riukiu or Loochoo arc) has been 
made the subject of a special paper by v. Richthofen*, a paper 
based largely upon the monographs by Yamasakit and Yash- 
iwari$; both of which papers contain excellent maps, the first 
mentioned of Formosa and the other of the Riukius. It has al- 
ready been pointed out that the double series of arcs upon the 
continent border is paralleled by a third series that is outlined 
by the festoons of islands which inclose shallow seas and are 
surrounded by great ocean deeps. This latter and seaward 
series seems to end southward at Formosa, the structure of 
which appears to be of a different nature, and which is succeed- 
ed to the southv/ard by more contracted series of arcs, ex- 
tendmg, as Suess has shown, as far as the bay of Bengal. 
The Riukiu islands arc while convex toward the sea ap- 
pears to have a different character from the arcs to the north- 
ward. If one joins upon the map the islands of the outermost 
* Von. Richthofen: Geomorphologische Studien aus Ostasien, III, Die mor- 
phologische Stellung von Formosa nnd den Riukiu-inseln. Sitzungsber. d.k.pr. 
Akad. d. Wiss. z. Berlin, vols. 39 and 40, 1902, pp. 944-975, with pi. 3. 
t Dr. N. Yamasaki: Unsre geographischen Kenntnisse von der Insel 
Taiwan (Formosa). Peter. Mitth., vol. 46, 1900, pp. 221-234, with plate 19. 
t S. Yashiwari: Geologic structure of the Riukiu (Loochoo) curve and its 
relation to the northern part of Formosa. Jour. Coll. Sci. Imp. Univ. Tokyo, 
vol. xvi, art. 2, 1901, pp. 3-67, with five plates. 
