252 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



The entire absence, with the above exception, of Lacustrine Depo- 

 sits in the region I am describing is somewhat remarkable, when it is 

 considered that such are the most extensive and largely developed of all 

 stratified rocks throughout the adjoining districts of Asia Minor. 



In this place it would be proper to discuss the recent deposits of 

 calcareous tufa (see Part II. of this Memoir) ; but, as these do not 

 appear in the Southern part of the Frontier, and as they constitute a 

 very important feature in the investigation of the rocks at the 

 northern end, I omit the consideration of them at present, and 

 proceed to the subject of the gravels underlying the above-described 

 fluviatile and marine alluvia. 



3. Limestone Gravel. — In many localities (especially in the neigh- 

 bourhood of Dizfdl ; see fig. 4, p. 329) on the outskirts of the great 

 chain, an enormous accumulation of gravel reposes nearly horizontally 

 on the upturned edges of the tertiary strata, or dips at a slight angle 

 towards the plains on the S.W., in which direction it gradually thins 

 out. Seen from the plains at sunset, these gravel-masses present 

 a very peculiar appearance, their surfaces being cut up and deeply 

 furrowed by innumerable channels, caused by the heavy periodical 

 rains. Towards the N.E. and E., at their greatest elevation, they 

 frequently terminate abruptly in a perpendicular escarpment. A 

 very remarkable instance of this occurs about twelve miles N.E. of 

 Dizfdl, where, after attaining the summit of the range, the road is 

 carried to the valley of Gilalahu by a zigzag path down the face of a 

 cliif, which, judging by the eye, must be 200 feet in height, and is 

 entirely composed of this limestone gravel (see also fig. 3, p. 328). 

 The escarpment bears 12° S. of E. for a distance of about twenty 

 miles, being only interrupted by the passage of the River Diz and 

 the Kiinak Stream. Magnificent sections are obtained along the 

 course of these streams, as well as at the debouchure of the River 

 Kerkhah into the plains of Arabistan. Masses of this deposit fre- 

 quently stand isolated from the main range, and, being precipitous 

 on all sides, were formerly the strongholds of the mountain-chiefs. 

 Tangavan, at the N.W. extremity of the escarpment above alluded to, 

 is a conspicuous and fine example of an isolated gravel-fortress. 



The towTi of Dizfiil is situated on the left bank of the River Diz, 

 which here cuts through cliffs of this gravel 60 feet high. The 

 actual thickness of the deposit is certainly not less than 100 feet in 

 this locality (see fig. 4). 



The serdaubs, or cellars, in which the natives pass the day during 

 the scorching heat of summer, are excavated in it, and are reached 

 by long flights of steps. 



Subterraneous canals called Konats, for irrigation derived from 

 the river, have been cut by Persian perseverance for miles through 

 the gravel at a great depth below the surface. Their course is trace- 

 able by the heaps of pebbles thrown out at regular intervals through 

 wells. To one of these Konats, \\ mile E. of Dizful in the direc- 

 tion of the mountains, I descended by 60 steps of 13 inches each; 

 i.e. 65 feet. 



