Then, also, a water supply had to be established; and this meant some very pleasant work for me in taking levels up the banks of the river under the cool shade of the palms. While doing this, I often took my camp-kit with me, and a luncheon served in the wilds, with occasionally a friend to share it--when a friend was available--was delightful. On one occasion in particular, I went a long way up the river and was accompanied by a young member of my staff. The day had been exceedingly hot and we were both correspondingly tired when our work was finished, so my companion suggested that we should build a raft and float down-stream home. I was rather doubtful, of the feasibility of the scheme, but nevertheless he decided to give it a trial. Setting to work with our axes, we soon had a raft built, lashing the poles together with the fibre which grows in abundance all over the district. When it was finished, we pushed it out of the little backwater where it had been constructed, and the young engineer jumped aboard. All went well until it got out into midstream, when much to my amusement it promptly toppled gracefully over. I helped my friend to scramble quickly up the bank out of reach of possible crocodiles, when, none the worse for his ducking, he laughed as heartily as I at the adventure. Except for an occasional relaxation of this sort, every moment of my time was fully occupied. Superintending the various works and a hundred other duties kept me busy all day long, while my evenings were given up to settling disputes among the coolies, hearing reports and complaints from the various jemadars and workpeople, and in studying the Swahili language. Preparations, too, for the principal piece of work in the district--the building of the railway bridge over the Tsavo river--were going on apace. These involved, much personal work on my part; cross and oblique sections of the river had to be taken, the rate of the current and the volume of water at flood, mean, and low levels had to be found, and all the necessary calculations made. These having at length been completed, I marked out the positions for the abutments and piers, and the work of sinking their foundations was begun. The two centre piers in particular caused a great deal of trouble, as the river broke in several times, and had to be dammed up and pumped dry again before work could be resumed. Then we found we had to sink much deeper than we expected in order to reach a solid foundation indeed, the sinking went on and on, until I began to despair of finding one and was about to resort to pile-driving, when at last, to my relief, we struck solid rock on which the huge foundation-stones could be laid with perfect safety.