^ MALLET, VINDHYAN SERIES. 



Its character is very constant whenever met with. This and the twa 

 succeeding- sub-divisions tog-ether form the greater part of the whole 

 series south of the Sone in this region, occurring in a continuous line of 

 hills close to that river, in the eastern part of which the dip is very re- 

 gular, 10°-20° north ; but to the west the strata are much more disturbed. 

 Perhaps 200 to 300 feet may be taken as their thickness. Between 

 Nos. 3 and 5 there is a band of most remarkable rock, the exact charac- 

 ter of which remains yet to be determined. Its mineral constituents in the 

 Khone Khas neighbourhood are hornblende, felspar and a small proportion 

 of quartz, and the rock bears a strong resemblance to trap. Its thickness, 

 where greatest at Hoorkahoorkee, may be 150 feet, but it becomes much 

 thinner towards the west. The beds into which it is divided average 2 feet, 

 and bands of the porcellanic rock of 5 or 10 feet are sometimes interstra- 

 tified. The fact that porcellanic beds, identical in appearance with those 

 of the Sone valley, are associated in the Gwalior series with undoubted 

 contemporaneous traps, tends to support the conclusion that the beds 

 in question are also of igneous origin. In the lower Vindhyan outliers 

 south-east of Rotasgurh, however, the inferior conglomerate, &c., are ab- 

 sent, and we find at the base of the series a rock to all appearance the 

 equivalent of that in question. It is here less trappoid and granitoid in 

 aspect. It rests directly on granitoid gneiss, and its examination strongly 

 leads one to believe in its being a sedimentary rock made up of the 

 debris of the latter. The porcellanic strata which cover the trappoid band 

 and which are generally the first rock met with south of the Sone from 

 Hoorkahoorkee to the Rehund are somewhat difierent in composition 

 and structure from those beneath. They are less purely siHcious, and the 

 term * porcellanic^ is more tndy applicable to them. The beds, which are 

 thin and divided into angular pieces by sharp joints, exhibit alternate 

 white and grey, or black, or sometimes reddish, laminae varying fi'om a 

 mere line to an inch or more in thickness, which give them a very 

 ( 36 ) 



