148 R. Pumpelly on Geological Observations, etc. 
e abrupt termination of the plateau is owing to a great dis- 
location which marks, approximatively, the coast line of a former 
ocean to the north, in which the more recent deposits of the 
plateau originated, and along whose southern shore there existed 
an extensive region of volcanic activity. 
This high escarpment seems to be the Jnshan, and the fact 
that it is voleanic goes to prove the justness of Humboldt’s be- 
lief, that the Jnshan forms the continuation of the Tienshan. 
While the plateau is terminated on the south by this escarp- 
ment, it is limited on the east by parallel ridges, and descends 
by successive terraces, to the Manchurian lowlands. 
y the elevation of the plateau, north of this line of fracture, 
a great basin was formed between the escarpment and the range 
of mountains nearly marked, on the maps, by the Great Wall. 
This area became the seat of a series of lakes extending several 
hundred miles, from W.S.W. to E.N.E., and which have left a 
deposit of loam often visible in terraces several hundred feet 
thick. These lakes seem to have covered the whole Jand of the 
Orios, within the great northern bend of the Hwang Ho, and the 
valley system of the San Kang and Yang rivers. The fresh- 
water character of the loam is proved by the presence of fresh- 
water shells, 
The circumstances seem to warrant the supposition of a con- 
nected chain of lakes, stretching from the 106th to the 116th 
meridian, which received the waters of the Hwang Ho, before the 
formation of, or during a long continued obstruction of, the deep 
channel in which that river now flows between Shansi and 
Shensi, The main outlet seems to have been the present gorge, 
by which the Yang Ho traverses the mountains west of Peking, 
to join the Pei Ho of the delta plain. | 
‘The lower Pei Ho has, within historical times, more than once 
formed the mouth of the Hwang Ho. — 
Thus the Hwang Ho appears to present a most remarkable in- 
stance of one of the great rivers of the earth, not only shifting 
its lower course over an area of several degrees of latitude on its 
delta-plain, but also reaching the sea at the same point, at differ- 
ent times, after following two widely separated routes through a 
highly mountainous country. ic - 
1X. Among the more practical results obtained, I may met- — 
tion the determination, from personal observation and from native 
sources, of a large number of extensive coal-basins, and of Jocali- 
ties producing other useful minerals, all of which Ihave tabue 
reed g and represented, so far as is practicable, on a map. es 
