Total Water Discharge of Oasis — Water-Pressures — Static Head — Importance of Systematic Observations and Records of Bores — Sensitiveness of Wells — Experiments showing Mutual Interference of Wells — Bores Nos. 5 and 6 — Bores Nos. 4 and 42 — The Wells at El Dêr el Ghennîma — Decline in Discharge of New Wells — Effect of Closing Bores — Rate of Flow of Water in Sandstones — Danger of Over-Exploitation — Holding Capacity and Porosity — Experiments on Porosity of Nubian Sandstone — Large Quantities of Water held in Storage Beds — Economically only partially available at Surface. At the present day there are about 230 native-owned wells in the oasis, yielding a total discharge of some 295 qirats. We have seen that the qirat has not a fixed value, but represents a discharge varying from 22 to 38 or more gallons a minute. Applying these values as far as possible to the old wells, and adding the known discharge of the new, we shall not be very far from the truth if we estimate the total discharge of the oasis wells at 8,000 gallons a minute, or 11,500,000 gallons (53,000 cubic metres) a day. The largest well in Kharga Oasis is Ain Estakherab at Gennâh, with a discharge of between 700 and 800 gallons per minute. The average yield of those which might be described as the best wells probably does not exceed 150 to 200 gallons, while there are a great many which only discharge 20 or 30 gallons per minute. In some parts of the world the discharges of artesian wells are measured by thousands, not hundreds, of gallons. In Queensland and other parts of Australia, for instance, there are numerous bores throwing over 1,000 gallons a minute; in these regions the depth of individual bores in many cases amounts to thousands of feet, the pressure frequently rising as high as 100 pounds to the square inch. It must, moreover, be borne in mind that the artesian basins of Australia have only been exploited during a comparatively short period, and that from the nature of the country the wells are, as a rule, at considerable distances apart.