CHINA, MONGOLIA, AND JAPAN. 35 



ends and corners of small crystals of the constituent feldspar and quartz are sharply- 

 developed. 



The hills immediately surrounding Siwan, in the Great Wall range, east of Kal- 

 gan, consist of a reddish-gray syenite composed mainly of orthoclase, some gray 

 triclinic feldspar, crystals of hornblende, and a little quartz. Large crystals of 

 orthoclase render it porphyroid. Near the contact of this rock with the crystallme 

 schists west of Siwan, dykes of it are seen in the latter, while fragments of the schists 

 inclosed in the main body of the syenite are additional proof that it is eruptive, and 

 younger than the metamorphic schist formation. Fragments of this syenite are 

 inclosed in the pluto-neptunian rocks of the Kalgan porphyry. 



A syenite of medium grain, composed of slightly pink orthoclase and hornblende, 

 occurs over a large part of the rolling land east of Murkwoching. 



Fragments of a fine red granitite occur in the bed of the Yang Ho near Kiming, 

 and blocks of a red rock composed of fresh, bright-red orthoclase and grains of a 

 soft, talcose or steatitic mineral, thus approaching a protogine, are common in the 

 Flwaingan creek. At this latter locality there are many fragments of a rock, con- 

 sisting entirely of a coarsely crystalline, triclinic, feldspar, apparently labradorite, of 

 a grayish tinge tending to blue and weathering white. It contains scattered crys- 

 tals of a mineral resembling sahlite. 



Crystalline Metamorphic EocJcs. — The tilted and folded strata of these rocks form 

 for the most part all the ridges we have passed over after leaving Chatau. In the 

 hills northeast of Shachung are beds belonging to the chloritic series — white triclinic 

 feldspar, quartz, chlorite, and magnetic iron — a variety of chloritic gneiss. 



In the hills traversed by the road from Kalgan to Siwan, and south to Chauchuen, 

 the predominating rocks are stiU those of the chloritic series. In the hills south of 

 Siwan I observed chloritic gneiss — orthoclase, chlorite, and quartz — and schist of 

 nearly pure chlorite. In the mountains between Kalgan and Siwan, another well- 

 defined variety of chloritic gneiss occurs, in which the feldspar is, in great part, 

 triclinic. Schists of the hornblendic series also play an important part in this region. 

 They are composed of a greenish-white triclinic feldspar and hornblende, sometimes 

 one of these minerals predominating, sometimes the other. The trend of the uplifts 

 in this region, though irregular, seems to lie between N. and W. 



Under the Hwaingan beds near Kiu Hwaingan, the metamorphic schists here 

 represented by gneiss, lie with a remarkable approximation to conformability Avith 

 these younger strata. This gneiss consists of orthoclase and quartz, and is very 

 poor in mica, excepting on the surface of the slabs iiito which it breaks. 



The Barrier range, where we cross it west of Yangkau, is formed mainly of 

 schists of the hornblendic series. Among these are extensive strata of a rock com- 

 posed of black hornblende, with strongly defined prismatic cleavage, abundant gar- 

 nets, and a little white feldspar. Another rock occurs among these strata composed 

 of a greenish-white triclinic feldspar associated with a little black mica, quartz, and 

 hornblende. 



The substructure of the plateau, southeast of the Te Hai, is of granulite and 

 gneiss. The former rock is in places fine grained and schistose with minute gar- 

 nets, but occurs more generally with a coarser structure, in which it is seen to con- 



