From these figures it will be seen that the shutting down of a flowing or the opening of a closed well may produce a most marked effect on a neighbouring well within the short space of sixty minutes, even when the intervening distance is over 500 metres. In the above instance the rate of increase was most rapid at first, there being a gain of 7 gallons per minute, equivalent to about 12 per cent., in the first two hours. The total increase in the twelve hours amounted to 22½ gallons, or about 37 per cent. On reopening No. 5 it is seen that the discharge of No. 6 at once commenced to fall, the loss being nearly 9 gallons 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 farther apart, No. 4 being 835 metres N.N.W. of No. 42. The difference of level in this case was found to be 1·18 metres, the outlet of No. 4 being 60·74, and that of No. 42, 59·56 metres. Bore No. 4 has an internal diameter of 4¼ inches, is 141 metres deep, and draws from 19 metres of sandstone; Bore No. 42 is 6 inches in diameter, 218 metres deep, and 69 metres into the water-sandstone. Previous to the experiment, No. 4 was flowing 36·75, and No. 42 about 68·5 gallons per minute. 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 No. 42 was closed down at 9 a.m. on March 4, 1908, periodical observations being then made of the discharge of No. 4 during the next thirty-six hours. Briefly stated, the result of this experiment was 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 gain after thirty-six hours being only 3 gallons, or between 8 and 9 per cent. In this case the mutual interference is very much less than that between Nos. 5 and 6, doubtless largely owing to the greater distance apart, and to the lesser difference between the outlet-levels of the wells. In all probability there are many other conditions which combine with the above in determining the amount of interference, such as the positions of the wells with regard to the main lines of underground flow, the relative depths of the bores, and the thicknesses of sandstone from which they draw their supplies.