When the great extent and depth of the Qattara depression were established by Mr. Walpole’s explorations of last year, hopes were immediately entertained that the depression might be made to serve some useful economic purpose. Any idea of its being of use as a Nile reservoir was of course at once cut out, not only by reason of its position and distance from the Nile, but also by its immense size; for even if we could turn the whole Nile flood into it, some twenty years or more would be occupied in filling it to a sufficiently high level,[16] and the loss by evaporation from so large an area would be enormous. As a receptacle for drainage water from the Delta it appeared equally impossible of consideration, because of the great length and depth of the channels which would have to be cut to reach it. A more reasonable prospect seemed to be that of admitting sea-water from the Mediterranean into it by means of a navigable canal from the Arabs Gulf; this would only have to be about 56 kilometres in length to reach the nearest point of the depression; and once the canal was made and the depression filled, ships might sail almost to Siwa. Other advantages which might accrue from the formation of this inland sea were an increased humidity of the climate along the Mediterranean Littoral of Egypt, leading to increased rain-crops in that region, the establishment of a valuable fishery, and a possible increase in the water-supply of the oases by the causing of a slight rise in the static water-level there. Another idea, which rapidly followed the first one, was to utilize the depression as a source of electrical power for driving pumps by which the drainage of the northern parts of the Nile Delta might be improved. At first sight this latter prospect looked a very attractive one. The salt-marsh which covers much of the floor of the depression appeared suggestive of a former sea-connection, and if we could trace out this old connection, the cutting of a canal along it might not, it was thought, be a very expensive matter. Moreover, it was apparent that evaporation from an inland sea or lake of so large an area would keep pace with quite a large influx from the Mediterranean, so that if the influx were restricted to such a quantity as would permit of the lake-surface being maintained at a level considerably below that of the Mediterranean, power could be generated continuously. Suppose, for instance, that we maintained a permanent water-level in the lake of 50 metres below the sea; the estimated area of the lake at this level being 9000 square kilometres and the mean evaporation assumed to be 4 millimetres a day, an influx of no less than 36 million cubic metres of water per day could be passed into the lake without altering its level, and this with a fall of 50 metres would suffice theoretically for the continuous generation of over 270,000 horse-power. Of course the lake would gradually get more