One's launch should be provided with very powerful acetylene lights so arranged as to give a general illumination. Stalactites and stalagmites occur in every conceivable form. There are vaulted chambers which are full of them, and there are long straight passages which lack them and have roofs and walls resembling those of a New York subway. In places the cavern is full of edible-nest-building swifts and of bats. The air in the main passage is fresh. During the rainy season water runs from the roof in many places, and one must expect an occasional shower bath, but this is the only discomfort attendant upon the trip. Unfortunately, the mouth of this river is quite fully exposed to the heavy seas stirred up by the southwest monsoon, which heap up sand, forming a bar on which the surf breaks heavily; but during the northeast monsoon the current often opens up a wide and deep channel through this bar. There are several other underground rivers in the Philippines. An adventurous soldier embarked in a banca on one in Samar, and passed completely under a large mountain. Judging from his description of his experiences, this trip would be remarkably well worth taking. In the limestone caves we may some day find remains which will throw light on the history of the early inhabitants of the Philippines, as many of them have been used for burial purposes in bygone times. Pleasurable river navigation is by no means confined to underground streams. In Mindanao there are two rivers which offer strong attractions to tourists. One may ascend the Rio Grande de Cotabato through fertile plains, to a remarkable series of lakes swarming with great tame crocodiles and with a wonderful variety of waterfowl. On this trip one will see the Moros at home. The Agusan River, which rises near Davao Gulf and empties on the north coast of Mindanao, is the largest navigable stream in the islands. During ordinary weather it is strictly confined between well-marked banks. The dense forests which cover them have been cleared in a few places to make room for Manobo villages. Exquisite orchids and beautiful ferns abound. After ascending the river for one hundred twenty miles one comes to a remarkable submerged forest in a region which subsided a few years ago during a great seismic disturbance. Formerly it was very unsafe to enter it without taking an experienced guide, as the original river bed was completely destroyed and the many small streams flowing through the sunken area formed a very complicated maze. Now, however, two clearly defined canals have been opened up, both terminating in the immediate vicinity of the town of Veruela, and a trip through either of them will not soon be forgotten, for here tropical vegetation is seen at its very best.