LOFTUS — TURKO-PERSIAN FRONTIER. 283 



Tangs are so numerous that it would be useless to enumerate 

 them. The following may, however, be mentioned as fine ex- 

 amples : — the Gorge of the Ah i Zal at Kirki, — of the Kashghan 

 River, at Piil i Jaidar, — of the Kerkah at Pul i Tang, through Kiih 

 1 Vayzaneah into the plain of Seimarrah, — of Tang i Zimsa *, through 

 Kiih i Charmin, — and of the Shirwan, through the Derbend Khaui. 



Longitudinal Fractures. — But these chains have also been rup- 

 tured along the line of their central axis, as at Kiih-i-Bizenan. This 

 kind of fracture is not, however, of nearly such frequent occurrence as 

 the former ; but, when it does occur, valuable sections are afforded us. 



Tangs have probably been produced instantaneously by the cooling 

 of the mass, but fracture along the line of axis appears to be due to 

 another cause, viz. to the resistance offered by the overlapping of the 

 numerous beds during their elevation from an horizontal position. 

 This kind of fracture is frequently observed on the summit of a lime- 

 stone-saddle ; where the upper layers are broken, while the central 

 mass remains entire. A very striking example of this occurs in the 

 rock of Kirrindf, where the uppermost beds, acted upon by the 

 intensity of the subterranean force, are bent down almost vertically, 

 and broken off near the summit of the rock, presenting a strange 

 pinnacled and drawn-out appearance of the broken edge, as if torn 

 asunder while in a plastic state. Time and weather have of course 

 had their effect in channeling and fashioning these pinnacles in some 

 measure to their present forms, but their origin must be attributed 

 to the cause assigned. 



Besides these clefts traversing along the axis of the saddles, there 

 are numerous other parallel crevices upon the surface of all chains, 

 which must be due to similar causes. They are of various lengths 

 and depths, but usually not exceeding a few feet across. 



Vertical crevices are well marked on the north-western extremity 

 of the Chenari range, upon the right bank of the Ab-i-Zal. 



III. Secondary Rocks. 



As we proceed downwards in geological sequence, it becomes a 

 matter of impossibility to define the precise limits of the Secondary 

 Rocks. 



Organic remains are much more rare than in the Tertiary forma- 

 tions, and they are in such a crushed state as almost to defy the 

 practised eye of the palaeontologist. Sections are also more difficult 

 to be met with, and the beds are frequently so altered by their con- 



* Mr. Loftus's Memoir is accompanied by several water-colour sketches of 

 localities interesting in a geological point of view, by himself and Mr. H. A. 

 Churchill, the Secretary of the English Commission. Amongst these the outline 

 sketch No. III. represents the Tang i Zimsa, through Kuh i Charmin, as seen 

 from near the range above Kaylan ; it presents the peculiar features of tangs in 

 general. 



Mr. Churchill's sketch, No. IV., exhibits the gorge of the Kashghan at Piil i 

 Jaidar, in vphich the stx'ata are seen curving to the S.W. — Ed. 



t Mr. Churchill's drawings No. V. and VI. accompanying the MS. Memoir 

 illustrate this locality. — Ed. 



