QUATERNARY. 199 
The valley of the Hun was examined as far up as San-kia-tién. It 
consists of an inner canyon of unknown depth, which is nearly filled with 
sand and gravel, and of an outer valley of moderate width. 
In the northwestern part of the Bay of Peking the base of the moun- 
tains was skirted for 8 miles, from Chai-k’ou to Yang-fang. Near the hills, 
connected alluvial cones constitute a continuous zone of coarse gravel, 
which gives place, a mile or more further out, to a belt of sand, on which 
are situated the towns named Ch’ién-sha-kién and Hou-sha-kién, 7. e., 
Front Sand Town and Back Sand Town. 
From Yang-sung to Chang-p’ing-chéu, a course of 7 miles northeast 
across the several streams which form the Sha, or Sandy river, the western 
branch of the Pei, the plain is nearly level and is composed of sandy loam. 
This loam packs hard, cracks in drying, and is separated by the wind into 
two parts: fine dust which rises in clouds in the air and sand which is 
blown along the ground. 
From Chang-p’ing-chéu east to T’ang-shan Hot Springs, 10 miles 
along the mountain base, coarse wash from the hills lies in a belt north 
of a zone of sand and sandy loam, in relations like those noted along the 
western side of the bay. 
From T’ang-shan south to Peking, 18 miles down the central line 
of the bay, the prevailing material is sandy loam like that already described. 
South of each of the streams flowing east is, however, a belt of sand, some- 
times forming dunes 10 feet or more in height. These zones are produced 
by the north winds, which sweep the sand from the wide, slightly hollowed 
channels, in which the water is but a thread during much of the year, 
though a flood for a brief season. 
Summing up these notes, it is apparent that the Bay of Peking is 
surrounded by a zone of coarse gravel next the mountains, within which 
lies a belt of sand also washed from the mountains, and that the great 
central area consists of fine sandy loam of a rather compact nature. This 
loam, on being redistributed by wind, gives rise to local sandy tracts and 
to dust storms. 
From the preceding description it will be seen that the Plain of 
Peking is the upper surface of a body of material which fills a depression 
among the mountains as water fills an embayment along the coast. It 
appears also that the surface as we now see it is composed of wash 
deposited by rivers, together with local formations produced by wind. 
To these facts we may add the conception, concerning which geologists in 
general would agree, that the land formerly stood higher with reference 
to sea-level and has gradually subsided. 
