24 R. J. L. Beadnell—On Artesian Wells. 



equivalent to about 12 per cent., in the first two hours. The total 

 increase in the twelve hours amounted to 22 V g.p.m., or about 37 per 

 cent. On reopening Bore Iso. 5 it is seen that the discharge of No. 6 

 at once commenced to fall, the loss being nearly 9 g.p.m. in the first 

 two hours ; afterwards the rate of decrease gradually diminished, until 

 at 7 p.m., -when the observations were discontinued, the flow had 

 fallen to within 3 gallons of its normal. 



A second series of observations was made between two bores 

 considerably further apart, No. 4 being 835 metres N.IS'.W. of Xo. 42. 



The difference of level in this case was found to be 1*18 metres, 

 the outlet of Bore 4 being at 60-74, that of Bore 42 at 59-56 metres 

 above sea-level. No. 4 has an internal diameter of 4^ inches, is 

 463 feet deep, and draws from 63 feet of sandstone ; No. 42 is 6 inches 

 in diameter, 715 feet deep, and 225 feet into the water-sandstone. 

 Previous to the experiment the former was flowing 36 -75 and the 

 latter 68*5 gallons per minnte. Precautions were taken against other 

 wells influencing the results,' the nearest bores having been opened 

 twenty-four hours previously and being kept in the same condition 

 throughout the experiment. Bore 42 was closed down at 9 a.m. on 

 March 4, 1908, periodical observations being then made of the 

 discharge of Bore 4 during the next thirty -six hours. Briefl}' 

 stated, the results were as follows : — the discharge of No. 4 had not 

 perceptibly increased at the end of the first half -hour, but had 

 done so after one hour. It continued to increase at a very slow 

 rate, the net increase after thirty-six hours only amounting to 

 3 g.p.m., or between 8 and 9 per cent. In this case the sensi- 

 tiveness is very much less than that between Bores 5 and 6, due 

 doubtless to the wells being a greater distance apart and to the 

 lesser difference between their outlet levels. In all probability there 

 are a number of other conditions which combine with the above in 

 determining the amount of interference, siich as the positions of the 

 wells with regard to the main lines of underground flow, the relative 

 depths of the bores, and the thickness of the beds from which they 

 draw their supplies. 



The most marked example of interference which I have met with 

 was in the case of two ancient wells at Der el Ghennima, near the 

 eastern escarpment of the depression. These bores are sunk on the 

 crest of an anticlinal fold running north and south, and are only 

 88 metres apart. They have recently been cleaned out and their flows 

 restored. The difference of level in the outlets is 2-07 metres, the 

 higher well being 34^ metres, the lower 41 metres in depth. The 

 opening or closing of the lower well produces an almost instantaneous 

 effect on the higher, the difference in flow within thirty seconds 

 amounting to over 10 per cent. A considerable number of 

 observations were made, but those mentioned on the opposite page 

 are sufficient to show the rates of decrease and increase. 



The closing of the lower well is seen to have influenced the dis- 

 charge of the upper bore to the extent of 100 per cent, in the space 

 of thirty minutes, while the flow Avas trebled in twenty-four hours; 

 on reopening the lower well the discharge of the upper fell to within 

 50 per cent, of its normal within forty-five minutes. 



