DETAILED ACCOUNT OF SOME RECENT EXPERIMENTS. 2Q 



are characters common to all alluvial deposits. But endless variation 

 is introduced by differences in horizontal extent, vertical depth and 

 gradient. Thus the conditions which cause artesian flow at Quetta 

 exist to a certain degree in all alluvial plains. Nevertheless the 

 capacity of the reservoirs thus formed must vary greatly according 

 to local conditions. It is natural that the immense extent of land 

 occupied by the Indo-Gangetic alluvium should have attracted a great 

 deal of attention from the point of view of artesian supply, but its 

 capabilities have scarcely been tested : experiments have been so 

 few and so incomplete that its structure is still to a great extent a 

 matter of conjecture. Just as the upper part of the talus skirting the 

 Baluchistan mountains consists of accumulations of boulders continu- 

 ous with gradually finer gravels that dip under the fine clay deposits 

 of the plains, so does the upper part of the alluvial talus all along 

 the foot of the Himalayas consist of coarse gravels forming the slope 

 called '"bhabar," the lower part of which dips under the soil of the 

 " tarii." Mr. Medlicott argued that the gravel beds of varying 

 degrees of coarseness that are interbedded at various depths with 

 the clay deposits of the alluvium, must be in communication with the 

 "bhabar" zone of gravel : here then, just as in the case of the 

 Quetta plain deposits, leaving aside the difference in proportions, we 

 have the requisite conditions for a very perfect artesian reservoir- 

 Percolation acts freely in the. coarse deposits of the gravel zone 

 which absorb a considerable proportion of the rainfall, and the over- 

 flow at the upper part of the underground reservoir makes itself evi- 

 dent from the copious springs which issue in the zone along which the 

 gravels dip under the clay deposits of the tarai. This line of springs 

 indicates therefore the altitude of the fountain head of the artesian 

 reservoir, and, by tapping that reservoir in the alluvial plain, at lower 

 altitudes, water may be expected to overflow at the surface. In 

 order to make the conditions of success as favourable as possible, the 

 proposed wells should not be sunk too far south from the Himalayas, 

 because, with such a low gradient as that which prevails at a 



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