48 MIDDLEMISS: PHYSICAL GEOLOGY OF SUB-HIMALAYA. 



such ; for who can say how long an age it takes to crush strata into 

 a highly inclined position ? It depends on causes which are quanti- 

 tively less known than are those of deposition. I, therefore, urge 

 that conformability, where the rocks attain great thickness, is a 

 better proof of great age than unconformability, which merely indi- 

 cates a break in deposition which need not always have been of 

 immense duration. 



The great extension of the fault between the conglomerates and 

 the Nahans, and especially its passage in an easterly direction into 

 a monoclinal fold (Dabka N.), as also its perfect parallelism to the 

 strike of the beds, seem to point out that it belongs rather to the 

 class of fold-faults than to those of normal dislocation. Still, there is 

 no need to invoke a mighty sigmaflexure to do the work here : al- 

 though horizontal pressure of the earth's crust must have had large 

 lateral effect on the strata as a whole, it is probable that the im- 

 mediate results were rather of an elevatory and depressive, than of a 

 tangential, order in this locality. The fault, therefore, partakes of 

 the nature of a vertical fault, slightly inversed ; but it cannot have 

 been due to a mere shrinkage, or to local accidents in the earth's 

 crust, as is the case with an ordinary fault : rather, it must have been 

 due to a larger movement of the mountain mass. Further on, when 

 speaking of the Pcitli dun, I shall have additional reasons to put for- 

 ward in support of this. 



Returning to the Kosi R. section, the Nahan sandstones continue 

 (generally obscured in the actual river-bed by Re- 

 cent gravels) up to Mohan. One and a half miles 

 north of that place the main boundary fault is reached and the Hima- 

 layan rocks set in. Between Moh£n and the main boundary, however, 

 there are several small chaors of nearly horizontal conglomerates 

 which I am inclined to place with the uppermost Siwalik conglomer- 

 ates. It is, however, possible that they belong to a slightly younger 

 stage. This line of flat chaors continues, as will be seen from the 

 map, westwards to join similar beds in the Rimganga R. at the junc- 

 tion of the Pandali Rau (21). From Moh£n the Kosi bends away up 

 stream E. S. E., along the strike of the rocks, keeping very near the 

 main boundary. The latter finally cuts the river obliquely near 

 ( 106 ) 



