70 VREDENBURG : RECENT ARTESIAN EXPERIMENTS IN INDIA. 



abundance of overlying impermeable clays that form such a large 

 proportion of the tertiaries, would give rise to conditions eminently 

 suited to artesian action. So far, however, no borings have pene- 

 trated to such a depth. The boring sunk at Gogah by Lieutenant 

 Fulljames in 1836-1839, to a depth of 354 feet 9 inches, mention of 

 which is made in Mr. Medlicott's Report, still remains the most 

 important attempt, and it never reached the base of the tertiaries. 

 Some of the tertiary strata contain strings and crystals of rock- 

 _ , ' . salt within their layers, and it seems to be 



Salt-bearing strata. 



owing to this circumstance that the wells in 

 some parts of Gujarat contain brackish water. The behaviour of 

 the wells varies according to the depth at which these salt-bearing 

 strata lie below the surface. It may happen that the well, when first 

 sunk, contains fresh water from surface layers unaffected by the 

 brackish water lower down ; but if the demand upon the water- 

 supply in the well increases beyond a certain extent, the brackish 

 water may percolate from below. This is particularly liable to occur 

 in seasons of exceptional dryness when the general level of sub- 

 soil water has been lowered, and the communication thus established 

 with the deeper layers of contaminated water may cause the wells 

 to become permanently deteriorated. 



In places thus situated, a supply of perfectly fresh water has 



sometimes been tapped by sinking a pipe from 



Fresh water-supply 



tapped by borings of the bottom of the well, until it penetrated 



moderate depth. 



through some layer of impermeable clay. 

 Separated by this impermeable bed from the upper layer of saline 

 water, the supply Lhus obtained is artesian in the strict sense of 

 the term, although the water may not rise higher than the level of 

 ordinary ground-water. 



Some very successful attempts of this class have been made by 

 Experiments at Mr - G - W - Tata at Naosari, an abundant 



Naosan. supply of fresh water being obtained at a depth 



of about 150 feet. 

 ( 70 ) 



