rough-Stone talus was necessary, and at the present time it is from three to six times as wide as it originally was, and its thickness has been greatly increased by the enormous quantities of stone thrown in to make good the sinkage which has from time to time taken place. In the first twenty years of the anicut's existence over 500,000 tons of stone were used for this purpose, and vast quantities more have been used since. Nowadays very little is required, and that only at certain places.
Another considerable change in the original design was the adoption of the plan of founding the anicut on the sand confined between its face wall and the retaining wall at the toe of the apron, instead of upon a mass of loosely deposited stone. The Ráli branch alone was constructed on the latter method and its foundations were the only ones which gave any trouble. They allowed the water to pass through in great quantities.
Three sets of under-sluices of fifteen vents each were built, one near the head-sluice of each of the main canals of the three sections of the delta. Three locks were also built, one at the head of each of those canals. Three head-sluices were also ultimately necessary.
The sanction of the Court of Directors to the execution of the work was received early in 1847. In April of that year operations were vigorously commenced. A detachment of Sappers and Miners was posted to Dowlaishweram, and a Sub-Collector (Mr. H. Forbes) was appointed to superintend the recruitment and payment of labourers and to procure the necessary supplies. His exertions (it may here be noted) were more than once acknowledged to have contributed largely to the success of the work (Sir Arthur said 'his vigorous and active measures have roused this district to a degree that could not have been expected') and he was specially thanked in the Government order reviewing the completion of the project. Before July had arrived, as many as 10,200 labourers, 500 carpenters and the same number of smiths had been collected to put in hand preliminary preparations. Boats were built, railway waggons constructed, the quarry opened and two double lines of rail ran from it to different points on the river banks, and the embankments on the islands put in hand.
In the working season of 1848 the actual construction of the dam was begun, and the Dowlaishweram and Maddúr sections were both built to the height of nine feet, and good deal of work was also done to the Dowlaishweram and Vijésvaram sluices. In the middle of 1848 Sir Arthur Cotton
