KHASI HILLS.- 125 



tontinue, though less markedly, all along the river valley. The beds of 

 clean grits have been so indurated, as to appear quite glassy and like 

 quartz rock; the grains still appearing distinct. The conglomerate beds 

 also are hard, have a talcose and soapy character, and the shaly 

 beds are more slaty. False bedding, of the same character as that' 

 seen so commonly round Cherra Poonjee, is here observable ; and 

 current-marking (a) is well shown on many of the beds. In mineral 

 texture they would appear much more nearly aUied to the old slates 

 and quartz rocks before described. 



Passing up to Mow-phlang, these sandstone beds continue to exhibit 



gradually a less amount of change as they rise upon the hill. These rocks 



Incipient cleavage. here exhibit also a tendency to a cleavage, or divi- 



(oj I have in several places in this report used the term " current marking," which 

 1 have been for many years in tlie habit of employing to express that jicculiar structure 

 ordinarily called " rippk-marking. " This latter term is decidedly erronecius, the structure, 

 as has been often remarked, not being the mark of a ripple, but rather a ripple itself. 

 Current-marking is less objectionable, although the marks left by currents are so numerous, 

 and of such various kinds, that it is scarcely definite enough. " Rippling^' would probably 

 be the simplest and best term, although even this will to many convey the idea of water 

 being the only agent to produce such appearances. That this is not the case, the most 

 cursory examination of a Sandy beach, or of the dry sands of a river-bed, will convince 

 any one. In fact, this peculiar structure is as frequently produced by the action of wind, 

 as by that of water ; and may often be seen as perfectly marked in the dappled clouds of 

 tlie sky, as on the sea-shore. It is simply the result of the continuous passage of a fluid 

 over materials, whose physical texture admits of free motion among their particles ; this 

 passage or current of the fluid heing only of such strength or rapidity as to drive, shove, 

 or impel these particles forward without maintaining them in suspension. Rippling ceases 

 to occur when either the size of the particles moved or the force of the current is so altered 

 as to alter the mode of progression of these particles. Any one, who will attentively 

 examine the motion of the dry sand of the sea-shore, or of a river-bed, will see, that in all 

 cases when this wavy surface is developed, the particles of the sand are regularly forced 

 up the long and wind- ward or current-ward slope of the ripple, and reaching the top, fall 

 by their own gravity down the steep or leeward side ; tlie same process being again re- 

 peated with succeeding particles, so'that the entire upper surface of the sand is in slow 

 and continuous motion. A sudden increase of the force of the wind or current, such as a 

 sudden blast, will obliterate all this wavy appear.ince, precisely as it would obliterate tlie 

 regular and continuous waving or rippling of the surface of water ; and on the wind 

 re-assuming its normal force, this waving will he again re-produccd. 



