1865.] 



Notes and Correspondence. 



759 



five feet. A cliff of shelly calcareous 

 sandstone, of considerable hardness 

 and from thirty to forty feet high, 

 containing exclusively the shells of 

 common species still inhabiting the 

 Black Sea, exists on the north side 

 of this lake, and is of some extent, 

 since a road is worn or cut through 

 it by which the lake is approached. 

 The lake is very salt, and its waters 

 are largely evaporated for the manu- 

 facture of" salt for local use. It is 

 evident that the lake has been much 

 reduced in this way, for there is a 

 level tract of nearly a quarter of a 

 mile of mud between the banks and 

 low cliffs that enclose it and the 

 present water. The lake is pear- 

 shaped, about two miles across in 

 most parts, but there is a kind of 

 inlet opposite the sea running an- 

 other two miles into the country, 

 and, perhaps, sometimes receiving a 

 small amount of local drainage. On 

 the south side of this lake (at a in 

 the chart, Fig. 2) one is struck by 



Black se a 



^s->^ 



the conical form of a part of the 

 shore, and the appearance of a large 

 semicircular space like an amphi- 

 theatre 300 yards across, scooped 

 out and open towards the east. This 

 is a hill of marly and shelly lime- 

 stone, with gypsum, soft when wea- 

 thered but very hard in the inside. 

 Towards the east and north these 



rocks form nearly vertical cliffs 60 

 feet high, the rock pitching more 

 than 45° to the north on the north 

 side, and more to the west on the 

 east side. 



Just beyond the foot of these 

 limestone cliffs to the north there 

 is a line of petroleum springs. 

 These are made known by the bub- 

 bling up of gas, accompanied by 

 mineral oil, through the mud and 

 water of the lake. They are also 

 clearly indicated on the banks of 

 the lake by a number of old Tatar 

 wells, which range nearly east and 

 west. Close to some of these old 

 wells, and in various other positions, 

 wells have been sunk and borings 

 made in modern times. These vary 

 in depth from 30 to nearly 500 feet. 

 Some are through small depths of 

 limestone into clay, others through 

 surface accumulations to limestone, 

 others through limestone only. 

 Only some are successful, and the 

 general result is that the petroleum 

 must rise through or very near to 

 a fault of considerable magnitude, 

 which has thrown up the limestone 

 to the north, on which side they 

 have been denuded and their thick- 

 ness much diminished. Where the 

 fault is cut is apparently the place 

 where most petroleum issues, and 

 where after this the limestone is 

 pierced, as in one of the wells, the 

 supply of oil is diminished, and it 

 comes up mixed with a good deal of 

 water. The section in the next page 

 will illustrate the nature of the case, 

 and is proved by a number of sink- 

 ings, of all of which I have the par- 

 ticulars. Borings on either side of 

 the line of fault have failed to reach 

 anything more than the merest 

 indications of naphtha. In this 

 case there cannot be a doubt that 

 the petroleum issues from a fault 

 or line of fracture, but there is no 

 mud volcano in the neighbourhood, 

 and no volcanic indication of other 

 kinds. The rocks around are chiefly 

 limestones, but with some of them 

 gypsum is largely intermixed. The 

 clays reached in the deep bore were 

 apparently of the same nature as 



