28 GEOLOGICAL MEMOIRS. 



In this rather extensive valley, the bottom of which is only partially 

 filled with the immense streams of lava, which have issued from the 

 Little Ararat and the beautiful secondary eruption-cone of the Dujirdag 

 on its lower declivities, a number of small lakes occur, in a white 

 clayey formation, which rests immediately on the horizontal surface 

 of the lava currents, which appear partially depressed in a singular 

 manner ; whilst the borders of the streams are formed by a continuous 

 series of wildly torn-up, long-extended swellings, similar in form and 

 freshness of aspect to those I had seen on the large lava streams at 

 the foot of iEtna. 



One of these lakes, remarkable for the red colour of its waters, 

 rendered more intense by contrast with the white ground enclosing it, 

 had attracted my attention in a high degree when on the top of the 

 Little Ararat. It lies on the left side of the valley, which there expands 

 like an amphitheatre close under the steep, terraced precipices of the 

 highest point of the Giisgiindagrotte, which consists of various mem- 

 bers of the old red sandstone, of dolomites and metamorphic slates of 

 the transition formation, enclosing limestone with spirifer and pro- 

 ductus — violently dislocated and heaved up by the red quartziferous 

 porphyry which appears in great extent and in very interesting geo- 

 logical relations in the interior of the valley. In July 1845, I visited 

 this lake, which is from one to two wersts in circuit. In crossing the 

 white clayey soil, covered with a luxuriant vegetation of reeds and 

 reed-like grasses, a strong alkaline odour, like that felt on entering 

 a soap-boiler's workshop, was perceived. A broad zone of this snow- 

 white soil, so soft that the feet sunk in it, formed the margin of the 

 lake, and was covered with an accumulation of irregular lump-like 

 incrustations of a very compact salt, of a white colour inclining to 

 red, and with a foliated fracture. These saline crusts lay all around 

 the white shore of the lake, chiefly floating in the water ; some frag- 

 ments broken off floated about like ice-shoals on the deep red surface 

 of the lake, which had quite the aspect of water almost on the point 

 of congealing. 



On examining the bottom of the flat lake-basin, so far as the 

 difficult access to the shore would allow us to do with long Cossack 

 spears tied together, I found it covered with a similar saline crust, 

 which was quite continuous, and appeared to increase with the di- 

 stance from the shore in such a manner as left no doubt that a layer 

 of salt several inches thick extends over the whole bed of the lake. 



These crusts have a high specific gravity and a very remarkable 

 structure. They consist of a very compact, intimately connected 

 aggregate of diverging (scopiform) bundles of crystals, like some 

 varieties of radiating zeolite, whose dull, rounded extremities form the 

 roughly mammillated surface of the crust. On the cross fracture the 

 thick rind shows distinctly a whole series of such thin crystalline 

 layers, firmly interwoven with each other. The fractured surfaces of 

 this interesting salt show a strong pearly lustre, whilst its colour is 

 exactly that of the carbonate of manganese-protoxide. The curious 

 colouring-matter of the saturated solution which fills the lake, has 

 concentrated itself in a dark-red coating on the horizontal divisions, 



