TILLA RIDGE. 127 



At a distance of eig-lit miles from Rotas, Mount Tilla commences 



to rise above the lower part of the ridge. Here 

 Mount Tilla. • , i i • 



older rocks are brought agamst the beds just now 



described by a fault or faults, the beds of different age in contact being 



greatly crushed, and some of the red tertiary clays 

 Faults. 



in the neighbourhood have the rather unusual 



character in this part of the country of being gypseous. The hill being 

 high and the southern escarpment bold, instructive sections appear almost 

 everywhere upon it, and the geological structure is clear ; but the series is 

 repeated in great part twice, if not three times, by slips or faults parallel 

 to the main dislocation (see fig. 12, PI. XII) . Along the south-eastern base 

 of the hill, the ground, there tolerably high, shows the grey and brownish 

 or red portion of the tertiary beds, generally nearly vertical, with an incli- 

 nation towards the hill, but sometimes folded. The lowest rocks appear- 

 ing along the fault are the earthy basal portion of the purple sandstone 

 group No. 2, with here and there possibly the top of the red marl of No. 

 1, which shows itself further to the west; but this is so much of the 

 colour of the red tertiary clays, observed to be gypseous near Mogli 

 village, that it is difficult to distinguish between them. 



Thin purple sandstones, the silurian zone, and overlying magnesian 



sandstones, &c., form the cliffs, above which the 

 ai£Es. ' ' ' ^ 



supposed trias group, No. 8, with salt-pseudo- 



morphs, appears, and the summit is formed by an anticlinal roll in the 



hard magnesian group. The red zone No. 8, again 

 Series. 



showing itself on the steep bedding-slope of the 



northern side of the mountain, is followed by a thin and uncertain repre- 

 sentative of the nummulitic limestone, with some shales below it here 

 and there ; above this come the usual grey and greenish lower tertiary 

 sandstones and reddish clays. The red clays here (as elsewhere), becom- 

 ing locally prevalent, range themselves in se zone along the north base of 

 the hill, beneath the soft grey sandstones and brown or orange clays 

 forming the Lower Siwalik group. Remnants of the nummulitic lime- 

 stone also occur near the summit of the hill. 



( 127 ) 



