This renders it doubtful if the force of the current alone, even with the aid of an embankment, would be sufficient to increase the depth, bound as the soil is by the roots of weeds. An embankment, however, if extended to the shore, would throw a much greater body of water on this point, and if a passage was at the same time opened by dredging, the current would I think be sufficient to prevent its again filling up. The expence of this, beyond the purchase of a dredging machine, and the vessel to work it, would not be great, to save expence the embankment should be made of piles, cut near the spot, and filled up with loaded fascines, also procurable from the thorn trees which cover the whole island, many of which are sufficiently long and straight to answer this purpose of piles; the wood is hard, heavy, and lasts better than teak under water. The crooked timbers of large cargo boats are generally of this wood.
This strikes me as the only plan likely to give a moderately deep passage, without a very heavy expence, and is not liable to any uncertainty but what must exist in the execution of all works exposed to the action of the sea. The extent to be thus excavated is only four hundred yards, and the embankment double; but much of the latter is in very shallow water, where long piles would not be required.
Another plan, suggested by Major Sim, of cutting a canal through the eastern part of the reef, I found liable to much greater uncertainty, though it had a flattering appearance at first view; it would require greater labour than the main channel, and, when completed, be of difficult access.
The improvement of this passage I therefore consider as confined to a depth of twelve feet, high tide, which is, however, a very important object, and can be attained at a moderate cost.
I now proceeded to examine the site fixed on as presenting the greatest facility for the excavation of a canal, and, after following the line of coast for a considerable distance, returned to the spot where the sea forced a passage in 1814, and which is in every respect the best adapted for the purpose. Commencing from the southern side of the cut, I found the sea clear of rocks, and deepening rapidly to eighteen feet, which is obtained at four hundred yards from the shore, and continues till it joins the inner passage to the coast of Madura. This point forms an extensive basin, well sheltered from all winds, where vessels could anchor with safety, and immediately in front of the passage, leading into the open sea, with a depth of eighteen and twenty feet, which increases after passing the chain of islands and reefs to five and eight fathoms; bottom, coral rocks, with a few spots affording anchorage on beds of mud and sand.
The party I left on shore had succeeded in clearing away the thorn bushes, so as to afford an open view of the nullah, which is nearly on a
