Trof. Milne — Across Europe and Asia. 69 



smaller scale it may be seen around tlie edges of ponds or even 

 puddles where the water is at all chalybeate — an analogous 

 phenomenon being produced in the chemical laboratory when solu- 

 tions containing iron are being evaporated. 



After passing the village of Kaisa, we were fairly amongst the 

 hills, which were grey and rugged, half their surface being covered 

 with grass, and the other half bare rock. Judging by the stones 

 beneath our feet, and from the rocks which here and there cropped 

 up, these hills apparently consist of a bluish-black hard limestone, 

 which, from its resemblance to that I passed before reaching the 

 Coal-fields lying to the North of Pekin, and from the fact that Coal 

 is likewise found in this neighbourhood, I should be inclined to 

 think was also of Carboniferous or else of Devonian age. The strata, 

 which in many places are distinctly visible, have a slight dip of about 

 1° towards the north. 



In many places amongst these mountains we passed through narrow 

 defiles in the alluvium. These seem to have been cut down through 

 the alluvium which fills the bed of these valleys chiefly by the agency 

 of traffic. They could be seen in all stages from mere rut marks to 

 deep cuttings flanked with perpendicular walls 40 and 60 feet in 

 height. When in these latter, looking up at the loose material above 

 you, charged with stones ranging from small pebbles to huge 

 boulders, you could not but speculate on the risk incurred by passing 

 travellei-s. Some of these defiles were so narrow that we had to wait 

 until the line of wheelbarrows, carts, and people, which are as thick 

 upon these country roads as they are upon a market-day in a country 

 town at home, going in a direction opposite to that in which we 

 were travelling, had passed out before there was room for us to 

 enter. In the mountain wadies of North-western Arabia I have 

 noticed the formation of cliffs of earth which are very similar to 

 these in China. The growth of these truly perpendicular walls 

 in Arabia appears to result from the undermining action of the little 

 water which sometimes trickles down these wadies, together with 

 that produced by a sand-drift which is ever working along their 

 lower portions. "When this has gone on for a certain distance, the 

 superincumbent material, having little or no lateral attachment to the 

 contiguous mass, falls down. There being nothing in the material to 

 produce an unequal disintegration, should it commence at any one 

 point, it is at once carried very rapidly over the surface of the plain 

 in which it commenced, the materials being so loosely placed together 

 that they are mutually dependent. Similar causes no doubt aid in 

 the formation of the Chinese gulleys. Those which run back towards 

 the mountains as tributaries to these main arteries of traffic have 

 no doubt also been hollowed out by the action of water, which, com- 

 mencing at the bottom of the valley, worked its way backwards up 

 towards the hills, much in the same way that a waterfall acts upon 

 the face of rock over which it drops. 



Next morning at 8 a.m. (Saturday 12th) we reached a point where 

 the limestone ended and gave place to granite. With this change, 

 both hills and roads were rougher. About 12 o'clock we crossed 



