The swifts and bats—the latter about the size of the ordinary English bat—avail themselves of the shelter afforded by the caves without incommoding one another, for, by a sort of Box and Cox arrangement, the former occupy the caves during the night and the latter by day.
Standing at the Simud Putih entrance about 5 P. M., the visitor will suddenly hear a whirring sound from below, which is caused by the myriads of bats issuing, for their nocturnal banquet, from the Simud Itam caves, through the wide open space that has been described. They come out in a regularly ascending continuous spiral or corkscrew coil, revolving from left to right in a very rapid and regular manner. When the top of the spiral coil reaches a certain height, a colony of bats breaks off, and continuing to revolve in a well kept ring from left to right gradually ascends higher and higher, until all of a sudden the whole detachment dashes off in the direction of the sea, towards the mangrove swamps and the nipas. Sometimes these detached colonies reverse the direction of their revolutions after leaving the main body, and, instead of from left to right, revolve from right to left. Some of them continue for a long time revolving in a circle, and attain a great height before darting off in quest of food, while others make up their minds more expeditiously, after a few revolutions. Amongst the bats, three white ones were, on the occasion of my visit, very conspicuous, and our followers styled them the Raja, his wife and child. Hawks and sea-eagles are quickly attracted to the spot, but only hover on the outskirts of the revolving coil, occasionally snapping up a prize. I also noticed several hornbills, but they appeared to have been only attracted by curiosity. Mr. Bampfylde informed me that, on a previous visit, he had seen a large green snake settled on an overhanging branch near which the bats passed and that occasionally he managed to secure a victim. I timed the bats and found that they took almost exactly fifty minutes to come out of the caves, a thick stream of them issuing all that time and at a great pace, and the reader can endeavour to form for himself some idea of their vast numbers. They had all got out by ten minutes to six in the evening, and at about six o'clock the swifts began to come home to roost. They came in in detached, independent parties, and I found it impossible to time them, as some of them kept very late hours. I slept in the Simud Putih cave on this occasion, and found that next morning the bats returned about 5 A.M., and that the swifts went out an hour afterwards.
As shewing the mode of formation of these caves, I may add that I noticed, imbedded in a boulder of rock in the upper caves, two pieces of coral and several fossil marine shells, bivalves and others.
The noise made by the bats going out for their evening promenade resembled a combination of that of the surf breaking on a distant shore and of steam being gently blown off from a vessel which has just come to anchor.
There are other interesting series of caves, and one—that of Madai, in Darvel Bay on the East coast—was visited by the late Lady Brassey and Miss Brassey in April, 1887, when British North Borneo was honoured by a visit of the celebrated yacht the Sunbeam, with Lord Brassey and his family on board.
I accompanied the party on the trip to Madai, and shall not easily forget the pluck and energy with which Lady Brassey, then in bad health, surmounted the difficulties of the jungle track, and insisted upon seeing all that was to be seen; or the gallant style in which Miss Brassey unwearied after her long tramp through the forest, led the way over the slippery boulders in the dark caves.
The Chinese ascribe great strengthening powers to the soup made of the birds'-nests, which they boil down into a syrup with barley sugar, and sip out of tea cups. The gelatinous looking material of which the substance of the nests is composed is in itself almost flavourless.
It is also with the object of increasing their bodily powers that these epicures consume the uninviting sea-slug or bêche-de-mer, and dried sharks'-fins and cuttle fish.
To conclude my brief sketch of Sandakan Harbour and of the Capital, it should be stated that, in addition to being within easy distance of Hongkong, it lies but little off the usual route of vessels proceeding from China to Australian ports, and can be reached by half a day's deviation of the ordinary track.
Should, unfortunately, war arise with Russia, there is little doubt their East Asiatic squadron would endeavour both to harass the Australian trade and to damage, as much as possible, the coast towns, in which case the advantages of Sandakan, midway between China and Australia, as a base of operations for the British protecting fleet would at once become manifest. It is somewhat unfortunate that a bar has formed just outside the entrance of the harbour, with a depth of water of four fathoms at low water, spring tides, so that ironclads of the largest size would be denied admittance.