GENERAL CONSIDERATIONS. 115 



for glacial action in any of the strata east of the Dehra dun. The 

 presence of well-rounded pebbles in a clay matrix does not seem 

 to me, of itself, to be proof either of glacial or extraordinary diluvial 

 conditions. It seems to me merely to point to that particular form 

 of deposition which must always obtain in a country subject to period- 

 ical rainy and dry seasons, namely, that during the rains each belt 

 of deposited material stretches a long distance out from the mouths 

 of the streams, but, when the amount of water in the stream bed 

 diminishes, the carrying power diminishes with it, and mud is 

 therefore deposited among the interstices of the torrent boulders 

 discharged during the rains. Sub-angular and scratched stones, in 

 anything approaching to a till or boulder clay, are unknown ; as also 

 is that peculiar form of ice-refuse of the nature of the contorted drift 

 of Norfolk. 



In turning from the broader questions involved in a study of the 

 General consider- Petrology of the country to those connected 



ations depending on w ith the horizontal extension of the rocks, and 

 distribution, and me- 

 thod of disturbance of the nature and meaning of the folds and dis- 

 the strata. . . 



turbance zones into which they are thrown, 

 there is a great temptation to wander aside into the fields of specu- 

 lation : the mind is eager to leave the Tertiary records behind and 

 to run riot among those scarcely decipherable monuments of the 

 higher Himalaya. It would be a very pleasant excursion for the 

 writer, and one might plead innumerable excuses for doing so : is not 

 the Himalayan chain one, and can we divorce the Tertiary zones 

 from the rest of the Himalaya? Has not every throe, as new form- 

 ations were cast up from their deposition ground, vibrated through 

 the great central mass of those glistening schists, and rugged 

 granites, which rear their pine-clad summits far and still further 

 beyond until they seem to melt among the clouds? But though 

 such a prospect is seductive enough, the still small voice of 

 scientific caution whispers to one that, if such license be prematurely 

 given to the mind, to play with the bubbles of speculation, there 

 may be a day of reckoning in the future when the minuter history 



H 2 ( 173 ) 



