38 On the Red Marl Formation of Mysore. 



from this point it appears again often to graduate in colour 

 and composition, becoming more red and ferruginous as it 

 approaches the red marl, and sometimes the graduation 

 between the red marl and kaolin is perfect, not apparently 

 by any mixture of the two, but by a gradual change in com- 

 position, and also by the kaolin becoming more arenaceous. 

 But in general the division between the two is quite distinct, 

 the kaolin running in white, tortuous, gradually decreasing 

 veins into the red marl for several feet ; at the south side 

 of Davenhully this is very beautifully and distinctly shewn 

 in a nullah where the veins of the kaolin are also reticulated, 

 insulating portions of the red marl between them. 



Sometimes the granite may be seen in round insulated 

 boulders of considerable magnitude embedded in the kaolin, 

 but there is never seen the slightest graduation between 

 the granite and the kaolin, the distinction being always 

 perfect, without the slightest alteration in the composition 

 or structure of the granite, except a very slight scaliness 

 on the outside of the masses, which may be sometimes 

 seen. 



Both in the red marl and kaolin, tortuous, vertical, and 

 irregular veins of quartz are seen, sometimes several feet 

 in length, composed of cracked pieces arranged with the 

 angles perfectly coinciding, but always separated from 

 each other about the l-10th of an inch, as if they had 

 shrunk after having been expanded by a state of high 

 ignition. In the large nullah near what is called the Belfry, 

 I observed a large plate of quartz nearly four feet square and 

 only about two inches thick, inclined slightly so as to lie on 

 • its bed, while the whole surface was exposed, by which it 

 was apparent that the whole was cracked into pieces about 

 two inches square, as in the veins. 



I have remarked the almost general absence of schists 

 in this formation, but some situations afford peculiarities, for 

 instance, two or three miles west of Bangalore, where some 



