The little fort is considered as a sufficient protection for the fishermen and small vessels against the pirates, who inhabit the island of Basillan, which is in sight from Mindanao, and forms the southern side of the straits of the same name. It is said that about seven hundred inhabit it. The name of Moor is given by the Spaniards to all those who profess the Mohammedan religion, and by such all the islands to the west of Mindanao, and known under the name of the Sooloo Archipelago, are inhabited. The day we spent at Caldera was employed in surveying the bay, and in obtaining observations for its geographical position, and for magnetism. The flood tide sets to the northward and westward, through the straits, and the ebb to the eastward. In the bay we found it to run two miles an hour by the log, but it must be much more rapid in the straits. At daylight on the 1st of February, we got under way to stand over for the Sangboys, [51] a small island with two sharp hills on it. One and a half miles from the bay we passed over a bank, the least water on which was ten fathoms on a sandy bottom, and on which a vessel might anchor. The wind shortly after failed us, and we drifted with the tide for some hours, in full view of the island of Mindanao, which is bold and picturesque. We had thus a good opportunity of measuring some of its mountain ranges, which we made about three thousand feet high. In the afternoon, a light breeze came from the southwest, and before sunset I found that we were again on soundings. As soon as we had a cast of twenty fathoms, I anchored for the night, judging it much better than to be drifting about without any knowledge of the locality and currents to which we were subjected. On the morning of the 2d, we got under way to proceed to the westward. As the bottom was unequal, I determined to pass through the broadest channel, although it had the appearance of being the shoalest, and sent two boats ahead to sound. In this way we passed through, continuing our surveying operations, and at the same time made an attempt to dredge; but the ground was too uneven for the latter purpose, and little of value was obtained. Shortly after passing the Sangboys, we had the island of Sooloo in sight, for which I now steered direct. At sunset we found ourselves within five or six miles of Soung Harbour; but there was not sufficient light to risk the dangers that might be in our course, nor wind enough to command the ship; and having no bottom where we were, I determined again to run out to sea, and anchor on the first bank I should meet. At half past eight o'clock, we struck soundings in twenty-six fathoms, and anchored.