The method of carrying out measurements of well-discharges in the oases is so inaccurate, and the records of the past output so defective, that it is not possible to gather from them whether the total yield of artesian water is at present diminishing or not. Mr. Beadnell considers it likely, however, that the general average water-pressure in the oases has been very much reduced within the historical period, owing to the long-continued exploitation of the artesian supplies.[26] The general study of the Libyan Desert which I have made in the last few years suggests that a gradual reduction in the static water-pressure in the oases may possibly have been brought about by other agencies than the exploitation of the water in the oases themselves. The first and most important of these other agencies is the withdrawal of artesian water by the Nile in the neighbourhood of Dakka. As mentioned on p. 113, it is practically certain that sandstone beds carrying artesian water are cut through by the Nile along a distance of several kilometres in that locality, and the influx of artesian water into the Nile may far transcend in quantity that removed by the wells and springs of the oases. The Nile has probably deepened its channel in this region by a few metres within historical times, and thus cut through a greater section of the water-bearing beds. An increase in the sectional area of the beds cut through would naturally mean an increase in the quantity of artesian water passing into the Nile, and hence a lowering of the static water-surface extending perhaps to the oases.