CHINA, MONGOLIA, AND JAPAN. 21 



where a low ridge of granite runs N. S. and is succeeded on its western side by 

 the vertical coal rocks, also trending N. S., while almost everywhere else in the 

 district the strike of these last is E. W. 



The preceding section is simply intended to show the relation of the strata to the 

 granite.^ The limestone d, is about 600 feet thick, and seems to be a member of 

 the Coal measures proper. The black shale e, with its seams of anthracite /, is 

 about 500 feet thick. 



From the Plain of Pehing to Kalgan. 



As we approach the Nankau pass, through which lies the great high-road from 

 Peking to Central and Western Asia, Ave find the edge of the plain deposit rising 

 with a more rapid slope toward the bordering mountains, while at the same time, 

 the firm, fine loam gives place to rolled fragments and gravel of limestone and 

 granite, from the neighboring hills. The pass is reached by the transverse valley of 

 the Nankau creek. 



Leaving the plain, we pass between lofty cliffs of limestone for about six miles, 

 before reaching the axial granite of the ridge. The trend of the strata, which is 

 N. 60° E., with a dip of 40° to S. E. by S. ^ S. at the edge of the plain, becomes 

 irregular as we approach the granite, the beds being in places almost horizontal, 

 and in others vertical and striking E. W. The latter case occurs at about two and 

 a half miles from the plain, where a side ravine discloses a dyke of a black erup- 

 tive rock, inclosed between the strata to which its plane is parallel. This rock has, 

 in a black compact base, thin transparent crystals of amber colored triclinic feldspar. 

 The dyke is only a few feet thick, and is made up of transverse columns. Near 

 the grand marble arch of the Kiiyungkwan, the limestone is cut through by red 

 porphyry, which is itself traversed by a greenstone dyke. The porphp-y contains 

 a little quartz, green mica, and crystals of orthoclase in a compact pink base. The 

 greenstone is apparently a fine-grained diorite. 



The granite of the Nankaii pass consists chiefly of large crystals of flesh-colored 

 orthoclase, black mica, and comparatively little quartz, with crystals of white triclinic 

 feldspar. Near the middle of the pass there is a different and somewhat remarka- 

 ble variety, almost free from mica, and consisting of pearly white orthoclase and 

 gray quartz in nearly equal proportions. It is slightly cellular, containing prismatic 

 crystals of white and smoky quartz in the small cavities. 



The first of these varieties is traversed near Chatau by dykes of a pink rock, 

 consisting of a fine-grained mixture of orthoclase and quartz with very little green- 

 ish mica — one of those rocks that form the link between quartziferous porphyry 

 and true granite. These dykes are in places crossed by others, probably of diorite, 

 consisting of a fine-grained mass of hornblende and feldspar. 



The ridge we have just crossed extends to the S. W., forming, in Shansi near 

 the Chihli boundary, a series of high peaks which, on the 26th of April, 1864, were 



' Unfortunately most of the specimens and notes from tbis interesting locality were lost. 



