Caldera fort.The fort is about seventy feet square, and is built of large blocks of red coral, which evidently have not been taken from the vicinity of the place, as was stated by the officers of the fort; for although our parties wandered along the alluvial beach for two or three miles in each direction, no signs of coral were observed. Many fragments of red, gray, and purple basalt and porphyry were met with along the beach; talcose rock and slate, syenite, hornblend, quartz, both compact and slaty, with chalcedony, were found in pieces and large pebbles. Those who were engaged in dredging reported the bottom as being of coral, in from four to six or eight fathoms; but this was of a different kind from that of which the fort was constructed.

The fort was built in the year 1784, principally for protection against the Sulu pirates, who were in the habit of visiting the settlements, and carrying off the inhabitants as slaves, to obtain ransom for them. This, and others of the same description, were therefore constructed as places of refuge for the inhabitants, as well as to afford protection to vessels.

Depredations are still committed, which render it necessary to keep up a small force. One or two huts which were seen in the neighborhood of the bay, are built on posts twenty feet from the ground, and into them they ascend by ladders, which are hauled up after the occupants have entered.

These, it is said, are the sleeping-huts, and are so built for the purpose of preventing surprise at night. Before our arrival we had heard that the villages were all so constructed, but a visit to one soon showed that this was untrue. The natives seen at the village were thought to be of a decidedly lighter color and a somewhat different expression from the Malays. They were found to be very civil, and more polished in manners than our gentlemen expected. On asking for a drink of water, it was brought in a glass tumbler on a china plate. An old woman, to whom they had presented some trifles, took the trouble to meet them in another path on their return, and insisted on their accepting a basket of potatoes. Some of the houses contained several families, and many of them had no other means of entrance than a notched post stuck up to the door.

The forests of Mindanao contain a great variety of trees, some of which are of large size, rising to the height of one hundred and one hundred and fifty feet. Some of their trunks are shaped like buttresses, similar to those before spoken of at Manila, from which they obtain broad slabs for the tops of tables. The trunks were observed to shoot up remarkably straight. Our botanical gentlemen, though pleased with the excursion, were disappointed at not being able to procure specimens from the lofty trees; and the day was less productive in this respect than they had anticipated. Large woody vines were common, which enveloped the trunks of trees in their folds, and ascending to their tops, prevented the collection of the most desirable specimens.

The paths leading to the interior were narrow and much obstructed; one fine stream was crossed. Many buffaloes were observed wallowing in the mire, and the woods swarmed with monkeys and numbers of birds, among them the horn-bills; these kept up a continued chatter, and made a variety of loud noises. The forests here are entirely different from any we had seen elsewhere; and the stories of their being the abode of large boas and poisonous snakes, make the effect still greater on those who visit them for the first time. Our parties, however, saw nothing of these reptiles, nor anything to warrant a belief that such exist. Yet the officer at the fort related to me many snake stories that seemed to have some foundation; and by inquiries made elsewhere, I learned that they were at least warranted by some facts, though probably not to the extent that he represented.

Traces of deer and wild hogs were seen, and many birds were obtained, as well as land and sea shells. Among the latter was the Malleus vulgaris, which is used as food by the natives. The soil on this part of the island is a stiff clay, and the plants it produces are mostly woody; those of an herbaceous character were scarce, and only a few orchideous epiphytes and ferns were seen. Around the dwellings in the villages were a variety of vegetables and fruits, consisting of sugar-cane, sweet-potato, gourds, pumpkins, peppers, rice, water and musk melons, all fine and of large size.

The officer at the fort was a lieutenant of infantry; one of that rank is stationed here for a month, after which he, with the garrison, consisting of three soldiers, are relieved, from Zamboanga, where the Spaniards have three companies.

Zamboanga.Zamboanga is a convict settlement, to which the native rogues, principally thieves, are sent. The Spanish criminals, as I have before stated in speaking of Manila, are sent to Spain.

The inhabitants of the island of Mindanao, who are under the subjection of Spain, are about ten thousand in number, of whom five or six thousand are at or in the neighborhood of Zamboanga. The original inhabitants, who dwell in the mountains and on the east coast, are said to be quite black, and are represented to be a very cruel and bad set; they have hitherto bid defiance to all attempts to subjugate them. When the Spaniards make excursions into the interior, which is seldom, they always go in large parties on account of the wild beasts, serpents, and hostile natives; nevertheless, the latter frequently attack and drive them back.