Their happy reception at the Cataract. Why their observations of the moon led them astray. Distinguishing fixed stars. How Angel fought the savages. Individuality. The chief an enigma. How he used the grindstone. His interest in machinery. The yardstick of the heavens to measure degrees. The Constellation Orion. The new calf. Milk and butter. The mysterious visit of the chief to the clay banks. Eating clay. Observations by Ralph and Tom. The clay eaters of the world. The cave and the treasure. The Professor refuses to take a share of it. Determination of the boys. Harry and George go to the cave. Go back for Ralph and Tom.

An island of abundance. Nuts and vegetables. Oils for illumination. Unripe fruit. How nature protects her products. Eggs. How good and bad are determined. Gases formed within the shell. Building an addition to their home. Putting up the new building. The accident to John. A terrible wound in the head. Chief's solicitude for John. Watching the results of the injury. The human traits in the chief. Danger point of the fever. The wonderful difference in his eye. Recovers memory. A deep sleep. His first words. Aphasia. The brain center. His initials J. L. V. on the match safe. Recognizing the chief.

Native of New England. Ran away to sea. Fortunately fell into hands of a humane captain. Became chief clerk. Learned navigation. The captain's interest in him. The return. The meeting with the captain's daughter. The wedding. Sailing east with his wife in the captain's vessel. A plague-infected port. Death of his wife. Leaving the accursed port. Death of the captain. Disposing of the ship. Travels through India. Enlists at Gibraltar. Serves in Matabela campaign. Goes to England. Is tutor to a Lord. Goes to Greece. Serves in two campaigns. Returns to New York. Enlists for campaign against Indians. Five years' service. Goes to Egypt to conduct explorations. Returns fever-ridden. Accepts Professorship. Signs as Professor in the schoolship Investigator. Sickness prevents his sailing. Wanders to San Francisco. Engages with friends to search South Sea Islands for treasures. Shipwrecked. Finding a cave. Captured by savages. Escapes. Meets with an accident. Loses all memory.

How John's story impressed them. How the boys entertained John with the stories of their adventures. The story of the yaks. John tells them how they could have controlled them with the different knots and hitches. The spectroscope. Light as a medium. The composition of the heavenly bodies. The solar spectrum. The boys remember John's story of the cave. His story confirming their knowledge about the savages. The concert with the flute and violin. Making glass for windows. Silver and mercury. Looking-glasses. Amalgam. Making small glass mirrors for the inhabitants. The chief's surprise at the mirrors. His contribution to the larder. The Amarylla. The poison plant. The boys' suspicions of the chief. Good for food. Stomach or blood poisons.

Completion of the house. Furnishing it. The chief recovers health. Showing John the message from the lifeboat. "Waters" one of his crew. The mystery of the photograph. Information that others of the ill-fated Investigator were on the island. Reasons why certain tribes sacrificed white captives. A new expedition planned. Determine to go overland. Making new guns. Ammunition. The boys invite Ralph and Tom to visit the cave. The surprise of the boys at the skeletons and the treasure. Exploring the cave. A terrific roar. Alarmed. Determine to investigate. Finding the Professor and John. The surprise party.

The boys ask John about his wonderful cave. The charted treasure caves. Seeing the treasure in the cave on the hill where the boys were rescued. An occupied cave. The medicine men. The two entrances and the cross-shaped interior. How the hoards were acquired. Piracy on the high seas. The gold and silver of the world. The precious metals taken to Europe by the Spaniards. Rushing work on the preparations. The gun barrels. Chief showing the boys how to make and use the bows. The disappearance of chief. The invention of a portable fort. How it was made. Stocking the wagon. Experimenting with the fort. Necessity as the mother of invention. The improvements in the fort. A new suggestion. Using the fort as a raft.