26 GEOLOGICALRESEARCnESIN 



large rivers. To the north lie the endless plains of Tartary rarely crossed by other 

 than low ridges. 



At the point where the road begins to rise to the table-land, we enter npon the 

 volcanic formation of Southern Mongolia. From the base of the plateau-wall to 

 the summit, we may look in vain for other than the rocks of this formation, and as 

 we travel westward we shall see little else while on the plateau. 



Our road now follows a general westerly course, keeping near the edge of the 

 table-land. The surface of the plateau along this route is everywhere cut into 

 by valleys varying in depth from one to several hundred feet. The tops of the hills 

 thus formed are flat, and in the same plane — that of the original plateau surface — 

 excepting where the erosion has isolated small hills, in which case they present 

 knobs lower than the general plane. The sides of these hills form in places cliff's, 

 but more generally they slope off to the valley bottoms. The width of the valleys 

 varies from a few hundred feet to three or four miles, the smaller ones sometimes 

 narrowing to a gorge, and again reopening to their usual size. They frequently form 

 fertile meadows with brooks winding through them, and are then the camping 

 grounds of the Mongols, and the pastures of their large herds of sheep, horses, cows, 

 and camels. The pasture is not confined to the bottoms, the whole country, hill and 

 valley, being clothed with excellent grass. 



Soon after leaving Hanoor we reach a small lake, or rather pond, without outlet, 

 inclosed in the depression between several knobs. It is difficult to understand how 

 these small depressions are formed, unless we suppose them to represent former 

 inequalities in the bottoms of valleys once occupied by running streams. Such 

 small lakes are characteristic of Mongolia, and we shall have occasion to notice 

 several. 



Continuing westward, the road passes the lama-monastery of Boroseiji, and 

 ascends the grassy valley of a small tributary of the Narin Gol.' This stream rises 

 at the very edge of the plateau, ffows N. E. by Urtai, and turning to the south de- 

 scends from the plateau at Teutai, and passing through the gorge at Changkiakau, 

 joins the Yang Ho. 



Leaving the system of this stream, we pass over a ridge, part of the original 

 plateau, near which is a hill rising several hundred feet above us, consisting, to judge 

 from fragments on the surface near by, of chloritic gneiss. This is an isolated peak, 

 rising through the volcanic formation which has buried the rest of the ridge. 



Descending to the west we enter another fine valley, apparently that of a tributary 

 of Angouli Noor.^ Through this valley flows a creek which, near the Mongol village 

 of Hanoortai, widens to a small lake, the abode in summer of thousands of wild 

 ducks. From this valley the road passes over a low ridge and descends by a nar- 

 row, rocky defile to the plain of Taulichuen, in which is the source of one of the 

 tributaries of the Yang Ho. We have here left the plateau, and are among the cul- 

 tivated fields of the Chinese,' but we are still on the volcanic formation. 



* Gol, Mong. for river. Wherever tbis word occurs in this itinerary it refers only to small brooks. 



" Noor, Mong. for lake. 



^ The Chinese are forbidden by law the cultivation of land on the plateau. 



