GENERAL llELATIONS OF KOCK GROUPS. 27 



hardened clay-j is seen in the middle of amygdaloidal trap ; it is about a 

 foot tMckj and extends for about 20 yards, terminating abruptly at one 

 end. Whetber this is part of a sedimentary intertrappean deposit, 

 or a concretionary mass, such as occurs frequently in the infra- 

 trappean sandstones and limestones, it is difEeuIt to say : it may either 

 be part of a sedimentary bed caught up by a ilow of lava or simply the 

 result of segregation, like the irregular nodules of jasper and chert 

 which are found both in the amygdaloidal traps and in the underlyino- 

 beds. The latter appears the more probable view, because bands of 

 jasper frequently occur too thin to have been carried forward by a lava 

 flow without breaking into fragments, yet extending for several feet • 

 but the band near Telingkhedi is an unusually large mass. 



No intertrappean rock was seen around Ambdghari tank, but there 

 is a considerable quantity exposed about 3 or 4 miles west of Telino"- 

 khedi. Time, however, did not suffice for the close examination of the 

 country in this direction. 



General Character op the Sedimentary Eocks near NAGPtjR, and 



THEIR RELATIONS TO THOSE OCCURRING IN OTHER PARTS OP InDIA. 



TdlcMr Qroiip. — It was perhaps rather a lucky guess than any- 

 thing else which led Mr. Theobald, my brother, and myself in the 

 report on the Talchir coal-field in 1856 (Mem. Geol. Surv., Ind., vol. i 

 p. 76), to point out that the clays of Korhadi, near Nagpur, were pro- 

 bably the representatives of the Talchir of Orissa. The view, however 

 was adopted by Mr. Hislop, though in some of his latest papers he 

 appeared more inclined to consider the Korhddi bed as representino- 

 those of Maledi (Q. J. G. S., vol. xx, p. 282). The first view proves 

 to be correct, and the same beds are much more extensively developed 

 near Chanda. 



It is astonishing that, over so large an area, beds of such trifling 

 thickness as the Talchirs should everywhere maintain their mineral 



( 321 ) 



