Geology. 247 



water strata that slope westward from the mountains of Central 

 Asia may be interpreted as fluviatile rather than as lacustrine." 



"The irregular structure of the piedmont slope, as exposed in 

 cuts along the railroad line, is well described by Walther. There 

 is a frequent and irregular alteration of stratified or massive 

 loess-like clay, finely stratified sands, and coarse gravel, with 

 many local unconformities ; all this being the result of the varia- 

 ble action of floods that sweep suddenly, unguided by channels, 

 down the piedmont slope; now eroding, now depositing; here 

 sweeping along coarse blocks, there depositing fine silts. Ten 

 miles south of Askhabad, where the railroad station is 819 feet 

 altitude, we saw, when returning by the Meshed road from an 

 excursion in the Kopet Dagh, more abundant piedmont deposits 

 of mountain-waste dissected to depths of several hundred feet. 

 A great thickness of these deposits has been penetrated by the 

 artesian boring in the suburbs of Askhabad, already mentioned, 

 2000 feet deep, and therefore with more than half its depth 

 below sea level, but without securing a water supply. The 

 whole depth, as shown in the record quoted by Walther, is in 

 variable layers of clay, sand, and gravel, similar to the deposits 

 seen in the barrow-pits near the railroad embankments, or in the 

 natural sections ; and all of this heavy deposit is therefore best 

 explained by conditions and processes like those of to-day during 

 persistent depression of the surface. The failure to secure a 

 water supply from this deep well is in itself very suggestive of 

 the irregular underground structures and of their torrential 

 origin." 



An excursion into the Kopet Dagh and the mountains of 

 Persia revealed abundant evidence of sub-recent terracing in the 

 valleys of a character to suggest a relative uplift of the heart of 

 the chain. The desert plains from Askhabad to Samarkand are 

 characterized by aggrading rivers. " The most notable feature 

 of this district was the absence of valleys. The rivers have 

 channels in which their waters are usually restrained, but there 

 were no valleys in which the river floods were limited. The 

 plains were open to overflow as far as flood supply held out. We 

 were told, however, that some distance upstream (to the south) 

 the Murg-ab has a flood-plain slightly depressed beneath the 

 plain. This we interpreted as meaning that the river had there 

 changed its habit from aggrading to degrading. On crossing 

 the Amu at Charjui we saw a low bluff on the north or right of 

 its course, although on the south the plain is not significantly 

 above the river. 



"The general absence of valleys is a natural, indeed an essen 

 tial, feature of a fluviatile plain in process of aggradation by 

 flood deposits. It is peculiarly appropriate to rivers like the 

 Tejen and Murg-ab, which dwindle away and end on the plain, 

 so that every grain of sand and every particle of silt must be 

 laid down as the water volume lessens and disappears. The 

 absence of valleys would, on the other hand, be surprising in a 



