DETAILED ACCOUNT OF SOME RECENT EXPERIMENTS, 87 



a manner as to form underground reservoirs. In the Deccan the 

 thickness of accumulated lavas and tuffs is so great that the under- 

 lying rocks are concealed over considerable areas, and no accurate 

 knowledge of the underlying surface could be arrived at except by 

 a large series of experimental borings involving an expenditure out 

 of all proportion with any results that could be reasonably predicted. 

 But in Central India, where the thickness is not so great, the under- 

 lying rock shows itself in many places, and if these inliers of the 

 older formations were mapped and their structure examined, it would 

 be possible to arrive at a very fair idea of the shape of the sur- 

 face upon which the strata of volcanic rocks are resting. I was 

 able to ascertain this circumstance during a rapid inspection, which 

 I made in 1898, of a part of Bhopal occupied by that formation: 

 small mounds of Vindhyan sandstone stand out here and there above 

 the almost level expanse of basalt. These are the tops of hill ranges 

 buried beneath the solidified flows of volcanic lava. Before the 

 lavas were poured over them, the Vindhyans were acted upon by the 

 agencies of denudation just in the same manner as at the present 

 day, and the topographical features thus produced bear a very dis- 

 tinct relation to their stratigraphy : once the lie of the different 

 bands of strata composing them is revealed by the study of those 

 inliers, it becomes easy to make out the shape of the surface with 

 sufficient approximation, and thus decide on a choice of the places 

 where water occurring at the junction of that old land surface 

 and the overlying rock would be most likely to rise at or near the 

 surface through a boring. 



(9) Other rocks. 

 The alluvium, the tertiary, the Gondwanas, the Vindhyans and 

 allied formations, and the Deccan trap are the principal formations 

 within which there can be any likelihood of artesian water being 

 found, although even in these rocks the chances are very uncertain, 

 In addition to these formations, there are enormous areas occupied 



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