1845.] 



519 



numerous as to render the road very difficult for the horses, and 

 make it necessary for the inhabitants to form huge piles of stones 

 in preparing a small piece of ground for cultivation ; though the 

 quality of the black soil, then sparingly occurring, is good enough 

 to repay them for their labour. The low ridge which bounds this 

 plain on the west consists of a grey limestone, associated with 

 thin marls, the strata inclining to the south-east ; and on its opposite 

 side, where the road winds among some narrow gullies previous to 

 entering among higher mountains, syenite, diallage rock, and horn- 

 blende porphyry are found in close connection with each other. 



About eighteen miles west-north-west from Kharput, a group 

 of limestone mountains fills up all the space intervening between 

 this point and the Euphrates to the north and west ; and through 

 these a deeply-cut valley runs to the north-west, extending for 

 six or eight miles to the Euphrates, where, for some distance around 

 the point of confluence, are worked the silver mines of Kebban 

 Maden. 



Mining District of Kebban Maden. 



The dotted parts indicate the presence of felspar porphyry, the small crosses 

 metalliferous threads and nodules; two of the hills are capped with limestone, 

 chiefly of the cretaceous period, and the rest of the diagram represents older 

 limestones and talcose slates. 



The mountains around the silver mines exhibit, in general, 

 bare surfaces of grey compact limestone, or of argillaceous and 

 chloritic slates, both of which appear to be without fossils. On 

 both sides of the valley in which the town is situated, rise sharp 

 peaks of a hard felspathic porphyry, containing large crystals of 

 pink common felspar, and sometimes exhibiting a slaty texture, 

 with the crystallised parts so ill defined, that where it occurs in 

 contact with the clay slates, it is difficult to assign to each its 

 proper boundary. This eruptive rock also makes its appearance 

 more frequently in the bottom of the neighbouring valleys ; as, for 

 instance, below the furnaces, and at the lower parts of the slopes 

 which border the Euphrates. A sharp ridge of the same rock 

 rims along the back of the east side of the town, and there forms 

 bold precipices facing the river which flows almost beneath. A 

 little further to the north, the porphyry is interrupted by a band 

 of ochreous matter, which, probably before the formation of the 



VOL. IV. PART in. Q Q 



