1859. J HISLOP GEOLOGY AND FOSSILS OF NAGPUR. 159 



the cause of the greater accumulation of lava at the spot where the 

 hill now stands may perhaps have been the delay resulting from the 

 effort requisite to break through the deposit and flow along its base. 

 And as in its onward course the lava would transform some of the 

 deposit, we can understand how the intertrappean stratum of the 

 hill is thinner than the subtrappean stratum of the plain, and can 

 moreover perceive how it is that the igneous at its junction with the 

 aqueous rock is to such an extent composed of the same materials as 

 the latter. Preferring, though I do, this theory of the eruption of 

 our trap, I would at the same time here beg to repeat the remark 

 previously made, viz. that although both the upper and the lower 

 portion of it were poured out together, still the lower would probably 

 continue, after the upper was consolidated, sufficiently liquid to be 

 capable of breaking up both the deposit and its incumbent sheet of 

 trap, as represented in fig. 1. 



The sandstone, which lies conformably under the clay at the Ar- 

 tillery Lines (see figs. 3 & 4), is the same as extends northward 

 through the plain to Godni Bhokara, where it is hard enough to be 

 quarried, and the same as attains to the immense thickness wit- 

 nessed on the lofty mural crags of the Mahadewa Hills. Lying, 

 however, in our district as conformably above the Glossopteris-sand- 

 stone and coal-beds as it does below the clay, I was inclined to class 

 it with the former rather than the latter. I am now convinced that 

 it is to the era of the latter that it belongs. Like most arenaceous 

 deposits, it is comparatively destitute of organic remains. In our 

 Memoir of 1 S54 I noticed stems of trees as imbedded in it. These 

 are very numerous in a ferruginous state at SilewaJa, and in a sili- 

 cified condition near Chanda, as also further south in the basin of 

 the Pranhita. In sinking a well through Sitabaldi Hill they were 

 met with in a third form, viz. like lumps of charcoal. Put along 

 with these stems there was found in the same shaft a little Pahulina, 

 which, on being kindly forwarded to me by Captain Cadell, of the 

 Bengal Engineers, I could not distinguish from one common in the 

 clayey deposit. I was now persuaded that the upper sandstone was 

 not to be classed with the lower, but with the Physa-bed ; and, 

 while perceiving my former mistake on this point, I beheld a con- 

 firmation of a view that I had previously expressed, to the effect 

 that all the deposits now remaining around Nagpur, from the fern- 

 strata upwards, were of freshwater origin. 



This discovery having brought the upper sandstone within the 

 scope of this paper in consequence of its connexion with the Physa- 

 bed, it has tor the same reason rendered it necessary here t<> refer to 

 the metamorphic rucks near Sitrfbaldi Hill, for these are but the 

 upper sandstone transformed. In pawing over the outcrop of gneiss, 

 which extends eastward from the base of that double-topped knoll 

 to the city of Nagpur, a superficial observer, Beeingthe apparent dip 

 at a high angle to the south, mighl suppose that he has before him 



very amient strata ; hut let him find a spot where the sandstone 



ami gneiss come together, and he will discover thai the one gradually 



changes into the other, and the almost horizontal direction of the 



