This subterranean river offers a fine opportunity for scientific observation well worthy to be embraced by some Australian naturalist. In the vicinity of the river is to be noticed one of the few signs of decay to be found in the caves--a portion of shell pattern formation shows evidence of mouldering, and appears like a mere skeleton. When the visitor has ascended the ladder and safely negotiated the angle at the top, he feels that he has witnessed the most interesting place to be found in the western wonderland; and when he fishes for a compliment to his agility, and is reminded of the graceful forms that occasionally ascend and descend in much better style, he immediately recalls a Patriarch's dream, and thinks the ladder ought to be named after Jacob. CHAPTER XXI. THE FOSSIL BONE CAVE, THE SPARKLING ROCK, AND THE CRYSTAL ROCK. About 20 yards north from the ladder to the underground river is the entrance to the Fossil Bone Cave. Here is a stratum of coffee-coloured slatey substance in layers like those of the Wianamatta shale. It is so soft that a gentle touch is sufficient to pulverise it. It is slightly honeycombed, and its outer surface is covered with imitations of delicate lichens. In this cave there is not anything in the shape of a stalagmite, except an empty brandy bottle on a little shelving rock, and that would be generally regarded as a bad substitute. For æsthetic as well as for other reasons, it would be better to keep such "stalagmites" out of the caves. On the top of a large rock is a mass of "washdirt," 14 inches deep, with "headings" of about the same dimensions. Some experienced diggers say they never saw more promising stuff. During the yellow fever from which so many suffered a few years ago, companies were floated on the strength of "claims" equally delusive. Proverbially, "auriferous ground" is deceitful, and this "washdirt," which looks rich enough to make a prospector's eyes sparkle with delight, has proved to be as worthless as a lying prospectus. A portion of it was washed, but did not show the colour of gold. It remains, however, an object of interest, and may serve to teach a useful lesson. There are in this cave solid limestone rocks above and below. The roof is about 500 feet beneath the surface of the mountain. In the bed of the cavern are many fossil bones. Some appear to be remains of native dogs. In various rocks are clusters of bat bones. A very noticeable osseous object is the vertebra of a bird with one side-bone. There is no trace of the other. There are also many large bones, the cylindrical cavities of which are filled up with formation. Some of these bones are deposited about eight feet from the bottom of the cave. On one ledge is a heap of bones, large and small. Some of them are very fine specimens. The height of this cave is about 15 feet, and its breadth from 8 to 15 feet.