158 WYNNE : GEOLOGY OF THE SALT RANGE IN THE PUNJAB. 



shales and the purple sandstones appear to have lost much of their 

 thickness in their last exposures towards the plains. 



The Khewra valley is much smaller than either of the last men= 



tioned " beats/' and the main scarp of the plateau^ approaching* nearer 



to the plains, the glen appears deeper (see frontispiece). Having 



passed a narrow defile between outlying hills, 

 Outer^hills. -, , , , ■, . .i t i 



overspread by the purple sandstone or the dark 



shaly Silurian zone, and capped by the dolomitic sandstone or its detritus, 



the valley opens somewhat, but is still hemmed in on all sides by high 



ground ; that to the westward only being entirely composed of the red 



marl. The strata appear from their present disposition to have had 



originally a dome-shaped arrangement, dislocated along the inner side of 



the outer hills, or else a general landslip of the overlying beds in that 



direction may have taken place ; narrow glens along the strike among 



these outer hills show on one side the overlying rocks, and on the other 



red marl and gypsum only. The marl is quite of the same kind as 



already described, having a decided similarity of 



Marl. 



aspect throughout, but its arrangement, so far as 

 it is connected with the rock-salt beds, is better known through the 

 exertions of Dr. Warth, whose report, mining plans and sections show 

 that there is a regular sequence in the upper part of the group, though 

 one which may not be minutely recognisable in other localities. 



The mines have been so often described and with so much detail* that 



it will be unnecessary to do more than state that 

 Mayo Mines. , . 



they are the largest and most important of the 



whole range,_and probably the most extensive salt mines in the world. 



Old chambers occur in them of 80, 120, 240, and 320 feet in width, 



and 40, 60, and up to 130 feet in height, besides natural shafts formed 



by rain water, one of which is 212 feet deep. 



These old workings have long been in a most dangerous condition. 

 That they ever grew so large, was owing to the ignorance of system 



* Authorities cited, ante, 



158 ) 



