The site of the well was chosen by the revered Sidi el Mahdi about 1898, and the works began almost at once. The boring, all done with picks and crowbars, was effected in hard reddish sandstone, by gangs of six workmen, relieved every month, and supplied with food and water by an endless succession of camel-convoys. At the end of eighteen or twenty months of uninterrupted work the water was at length found, clear, fresh, and abundant, at a depth of 80 yards, and since then the crossing of the Libyan desert has become relatively easy, the longest stretch without water being reduced to about 180 miles, whereas it was formerly almost 300. From the well of Sarra to Koufra the distance to be covered is only about 160 miles and offers no further difficulties, thanks to the intermediate well of Bechra. What makes the journey from Ounianga to Koufra particularly troublesome is the total absence of pasturage for 500 miles, a state of things that results in the loss of many camels on every journey. The only good pasturage in the whole region is said to be found 80 or 100 miles to the east of the Sarra well, in the Djebel El Aouinat, an unexplored mountain mass of an extent not exceeding 1500 to 2000 square miles, as I am informed, and whose altitude may be roughly put at from 4000 to 5000 feet. It goes without saying that I only give these figures as a mere indication, and as subject to caution in every respect. The break in continuity between the surveys of Rohlfs from the Mediterranean to Koufra and ours from the Wadai to the well of Sarra is consequently reduced to about 180 miles; but this gap does not seem likely to be bridged before Italy proceeds to an effective occupation of the oasis of Koufra, which falls within her sphere of influence.