320 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



but it must not at the same time be forgotten, that cHmatic alterna- 

 tions in those regions are exceedingly regular and uniform ; and 

 moreover there appears no reason why the Lake of Urumia should 

 not be similarly affected as the Lake of Van, since they are only 

 separated by a range of mountains. Such however is not the case, 

 for the former has been subsiding while the latter has been rising. 

 [See Note B. p. 325.] 



Again, it is difficult to conceive how four small streams alone, 

 supplied by melting snow, should have sufficient influence to elevate 

 twelve feet such a large body of water as the Lake of Van ; though 

 they may have a local effect at their mouths. 



Another solution which presents itself, is the existence of inter- 

 mittent springs in the bottom of the Lake, bursting forth at long 

 intervals. We are not, however, aware of results on so great a scale 

 produced by such a cause. 



We cannot hope to explain satisfactorily the phsenomenon above- 

 described until a series of observations shall have been taken of the 

 rise and fall of the barometer, and the effect of climatic influence on 

 the water of the Lake. 



At many localities along the shores, and particularly about three 

 miles N. of Van, are alkali-pits, called "perek." The salt water of 

 the Lake is admitted into shallow basins at the commencement of 

 summer, when by the rapid evaporation crystallization takes place, 

 and a crust or deposit is formed. This in ten or fifteen days hardens, 

 and is an eighth of an inch in thickness. The water is again allowed 

 to flow into the basin, and the process is repeated several times. In 

 about five months' time the deposit has assumed an aggregate thick- 

 ness of from two to four inches, when it is broken up into blocks 

 about two feet square, and transported to Van on arabahs, to be used 

 in the manufacture of soap. 



The " perek " is sulphate and chloride of soda, with a considerable 

 mixture of carbonate of lime ; it is of a cream-colour, and easily 

 broken by a sharp blow of the hammer. An insignificant tax or 

 percentage on the produce is levied by the government for leave to 

 collect the perek ; but I could not ascertain what quantity is annually 

 obtained, nor the value of the deposit in a raw state. 



Two Sections from Ardish, round the N. W. extremity of the Lake of 

 Van, to Jezireh-ibn-Omar. 



Figs. 22 and 23. 



Proceeding west from Ardish, a marshy piece of ground is crossed 

 to the extreme north point of the recently formed spur of the Lake, 

 between that town and Madghawank. The low range projecting 

 into the Lake to the west of Madghawank is of compact white lime- 

 stone, in which are to be detected a few casts of Corals. Succeeding 

 to this is a small strip of land, where the inroad made by the Lake 

 is evident, since a path which terminates abruptly on the shore is 

 seen commencing again on the opposite side of a little bay. 



Another low limestone range intervenes before reaching the pretty 



