336 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



main feeder of the Tigris flows from some peaks on the south-west. 

 Judging from the quantity of snow which still lay there in the month 

 of June, the elevation of these peaks must be considerable. After 

 ascending from this plain, a narrow and low ridge of limestone 

 strata, inclining to the north-east, separates the waters of the 

 Tigris from those of the Euphrates. On its western side is a lake, 

 the direction of which is nearly east and west, its length being 

 ten or twelve miles, and its breadth three or four ; and this lake 

 is said to give off its surplus water to the Euphrates. In the 

 valley, at its eastern end, through which flows a small tributary 

 stream, occur numerous instances of diallage rock, in which the 

 foliated crystals are remarkably large and beautiful. The ascent 

 westwards is again over porphyry and greenstone. The summits 

 of the high ridge we then cross are formed principally of limestone, 

 and the descent to the broad valley which lies on its other side, 

 offers steep slopes, on which are exposed, at intervals only, rocks 

 of actinolitic porphyry and diallage, which appear to be intimately 

 connected with each other. 



This fertile valley, through which a stream takes its course to 

 the Murad Tchai, near the town of Palu, is entirely covered by 

 alluvial soil ; and being carefully irrigated by the inhabitants of 

 its numerous villages, presents a great contrast to the sterility of 

 the mountains. Its height above the sea, from the observations of 

 Ains worth and Brant, is about 2500 feet. The hills which project 

 into it towards the town of Kharput consist mainly of marls and 

 sands, much decomposed and deeply furrowed by rains. 



At Kharput, a fine natural section is presented to the steep face 

 of rocks opposed to the east. This lower portion is composed of 

 a greenstone porphyry, disintegrated and rounded by the action of 

 the weather, whilst the upper part consists of thick massive strata 

 of compact limestone, having an inclination to the north-west, of 

 about 30°, and split by numerous fissures at right angles to the 

 plane of inclination. The contact of the two rocks may easily be 

 observed ; but the limestone appears to have undergone no change, 

 whilst the porphyry has become so friable that it is generally 

 eaten away by the air and rain to a depth of several feet below 

 the bed of limestone. 



To the west of Kharput, the country assumes a very broken 

 aspect, and exhibits confused groups of lower elevations, extending 

 towards the valley of the Murad Tchai, beyond which is now seen 

 a magnificent range of mountains, the Dujik Dagh, running about 

 east by north, and west by south, and in the month of June still 

 capped with* snow. The hills nearest to Kharput consist of lime- 

 stone and shale, but about three miles to the north-west appears 

 a grey syenite, with large and well-formed crystals of black horn- 

 blende, yielding very readily to the action of the atmosphere. The 

 mounds thus composed open out into a plain which is divided into 

 natural terraces, and which in its geological features presents a re- 

 petition of the plateau of Diarbekr on a small scale, the whole sur- 

 face being strewed with blocks of basalt of every size, which are so 



