HISLOP AND HUNTER — NAGPUR. 357 



of trap extending over sandstone without being associated with a 

 second sedimentary formation or volcanic effusion. 



Though the three formations are generally connected with each 

 other, yet it is chiefly the upper one, viz. the overlying trap, that 

 meets the eye over the face of the country. Leaving out of con- 

 sideration the very few examples of denudation which have uncovered 

 the freshwater deposit in the plains, and the equally rare instances 

 of eruption which have there upheaved it on its edge, it is on the 

 escarpments of the table-lands that we may be said to gain our whole 

 knowledge of this department of Nagpur geology. In commencing 

 our ascent of these steep hills, our attention is attracted by a number 

 of blocks near the foot, which are easily distinguished from the 

 masses of basalt among which they have fallen from above. As we 

 make our way up over the hard, dark, vesicular rock, the blocks in- 

 crease in number until we come to a friable greyish or bluish-green 

 zone. We must now move slowly and look narrowly, for a few 

 5^ards of upward progress may conduct us from the soft amygdaloid, 

 where fragments are thickly strewed, to a nodular basalt, where not 

 a trace of them is to be seen. Occasionally the freshwater forma- 

 tion is so thin that a very little earth or herbage may suffice to hide 

 it from our sight. But generally the water from the brow of the 

 hill in the monsoon collects into little rills just at the place where it 

 leaves the nodular trap, and having now gathered enough of strength 

 to make an impression on intervening barriers, it proceeds to plough 

 up the soft deposit, and the still softer subjacent amygdaloid, leaving 

 an interval between each streamlet, like a talus resting on the harder 

 vesicular rock below (see fig. 2). The thickness of the overlying 

 trap on Sitabaldi Hill and the tabulated summits in its immediate 

 vicinity is from 15 to 20 feet, which agrees very exactly with the 



Fig. 2. — Sectional View of one of the Trap Hills near Nagpur. 



a. Surface soil. c. Freshwater deposit. 



b. Nodular trap (15 to 20ft. thick). d. Soft amygdaloid. e. Hard amygdaloid. 



thickness assigned to it by Dr. Voysey at Jillan. On the Western 

 Ghats, however, according to Colonel Sykes, a stratum of earthy 

 jasper, which is just our freshwater deposit, was found near Junar 

 under a thickness of from 300 to 600 feet of basalt*. But it not 

 unfrequently happens, that in leaving the plain and climbing up a 



* Trans. Geol. Soc. 2 ser. vol. iv. p. 419. 



