The journey into the forest. Restlessness of the yaks. The alarm. Wild animals. George Mayfield and Harry Crandall. Their companion, an aged Professor. Their history. How they were shipwrecked. Thrown on an island without weapons, tools, food, or any of the requirements of life. What they had accomplished previous to the opening of this chapter. Making tools. Capturing yaks and training them. The three previous expeditions, and what they discovered. The mysterious occurrences. The fourth voyage of discovery. Losing sight of the strange animals. The forest. Discovering orang-outans. Capturing a young orang. Christening the "Baby." Its strange and restless actions. A shot. A wild animal. The wildcat. Enemy of the orang-outan. Distances deceptive, and why. Peculiar sensations at altitudes. Tableland. The fifth day. Discovery of a broad river. Progress barred.

A mountain chain beyond the river. Adventures along the river. Decide to follow the river to the north. Camping at the shore of a small stream. Prospecting tour on the stream. The flint arrow. The arrow in the skull of an animal. Different kinds of arrows. Home-sick. The light across the river. The test of firing a gun. Disappearance of the light. Seeking explanation. The night watch. The early breakfast and start. Scouting in advance. Qualifications in scouting.

A coast line of steep hills. Shooting an animal. The answering shot. The wonderful echo. Calculating distance of the bluff by the sound. The bear. The attack of the bear. The Professor's shot. The frightened yaks. Recovery of the wagon. Death of the bear. Rugged traveling. Changing their course. Deciding to return to their home. Stormy weather. The traveling chart. Methods used to determine course in traveling. An adjustable square. Obtaining angles from the shadows.

Breezes from the north. Indications of proximity of the sea. Warm winds. What wind temperatures tell. The missing yak herd. Mystery of the turning water wheel. The mill and workshop. Their home. "Baby" learning civilized ways. The noise in the night. The return of the yaks. The need for keeping correct time. Shoe leather necessary. Threshing out barley. The flail. The grindstone. Making flour. Baking bread. How the bread was raised. What yeast does in bread. Temperature required. The "Baby" and the honey pot. The bread with large holes in it. George's trip to the cliffs. A peculiar sounding noise and spray from the cliffs. An air pocket. Compressed air. Non-compressible water.

Earthquake indications. The seismograph. The theory about the interior of the earth. How geologists know the composition of the interior of the earth for miles down. The earth's "crust." The weekly hunting trip. Determine to cross South River and explore. The lost hatchet found. Making a raft to cross the river. Going into the interior. The sound of moving animals. Caution in approaching. Discovering the beast. Two shots. The disappearing animal. Indications that the animal was hit. Trail lost. Returning to the river. The animal again sighted. Firing at the animal. The shots take effect. The animal too heavy to carry. Return to the Cataract home. Finding the camphor tree. Its wonders as a medicine. Calisaya. Algoraba, a species of bean, or locust. Sarsaparilla. The trip to South River with the team. Finding the shot animal. The ocelot. Two bullet holes instead of one. The animal not at the place where it was shot the night before. Mystery explained by the finding of second animal which they had shot. Skinning the animals.

The accomplishments of George and Harry. Theory and practice. Fermentation. How heat develops germs. Bacteria. Harmless germs. Tribes of germs. Septic system of sewage. The war between germs. Setting germs to work. Indications from the vegetable world as to the climate. Prospecting in the hills. Tanning leather. Bark, and what it does in tanning. Different materials used. The gall nut and how it is formed. Different kinds of leaves. The edges of leaves. The most important part of every vegetation. Trip to the cliffs. Hunting for the air pocket. Discovery of a cave. Exploring the cave. The water in the cave. Indication of marine animal in the water. Return to the mouth of the cave. Discovering the air pocket. The peculiar light in the cave. Calcium coating.

Speculation as to the animal in the cave. Determined to explore the mystery of the "hole" in the hill. Trip to the hills. Difficulty in finding the "hole." Accidental discovery of a rock. The "hole" found. Indication that it was made by man. Why plants flourish around holes and stones. Moisture and heat. Object of cultivating plants. Lead and silver ore. Zinc. Working with their ore furnace. Putting metals to work. Labor-saving tools, what they are and what they do. Roasting ore. Melting roasted ore in crucible. Recovering zinc. Light from zinc and copper. Harry bitten by a "cat." The zibet.

Different fruit, flowers and vegetables. The thistle. Its nutritious qualities. Why animals can eat it. The sorrel and the shamrock. Significance of the latter. Vanilla. Smell is vibration. Harmony and discord in odors. What essences are composed of. Preserving seeds for planting. Food elements in vegetables. Surprising increase in their herd of yaks. Investigation. The wild bull. Apollo, the bull of their herd. His absence. The wild bull charging George. Stampede of the herd. George carried with them. Appearance of Apollo. Engaging in combat. Apollo the stronger. Reappearance of George. Return of the cows. Apollo the victor. Finding a brand mark on the wild bull. Inventory of their stock. Work in tanning vats. The flash of Harry's gun in the distance. Explanation of the difference in time between the flash and report. "Sound" or "noise." Vibrations. Light. The locomotive whistle explained.

Health on the island. Illness of Harry. Fever. Determining temperature. Making a thermometer. Substitutes for glass and mercury. How Fahrenheit scale is determined. Centigrade scale. Testing the thermometer. Determining fever. Danger point. Why a coiled pipe tries to straighten out under pressure. Medicine for fever. Rains and rising Cataract River. Decision to explore sea coast to the east. Yoking up the yaks. Gathering samples of plants and flowers. The beach. Following the shore line. Discovering the boat which had disappeared from the Falls in South River. Surprising find of strange oars and unfamiliar rope in the boat. Harry and George decide to sail the boat around the cliff point to the Cataract River. The Professor takes the team home. Sighting an object on the cliffs. Going ashore at the foot of the cliffs for an examination. Ascending the cliffs. Discovering the wrecked remains of their life-boat. Consternation when their boat is washed away from the shore. Getting the wreck of the life-boat down to the water. The watching and waiting Professor. The boys launch the life-boat and float to the mainland. Meeting the Professor. Explanations.

Theory that their island is near some other inhabited island. The mysterious occurrences of the fire in the forest; the lights across the river. The disappearance of their boat. The removal of the flagpole and flag; the arrows; the hole in the hillside; the finding of the boat with unfamiliar oars and rope on it. Conclude to make another boat. Unsanitary arrangement of their kitchen. Purifying means employed. Different purifying agents. Primary electric battery. The cell; how made. The electrodes. Clay. The positive and the negative elements. How connected up. The battery. Making wire. How electricity flows. Rate of flow. Volts and amperes. Pressure and quantity. Drawing out the wire. Tools for drawing the wire. Friction. Molecules and atoms. Accomplishments of "Baby." Climbing trees and finding nuts. George as cook. Making puddings. "Baby's" aid. Finding eggs of prairie chicken. Planning a surprise for the Professor. The birthday party. George's cakes to celebrate the event. Harry's gong. The missing cakes. "Baby" the thief. The feast. Why laughter is infectious. Odors. Beautiful perfumes wafted to long distances. Bad odors destroyed. Why. Oxygen as a purifying agent.

The Cataract water. Common oak chips as purifiers. Tannic acid. Bitter almonds. Universal purification of water. The Bible method. Albumen impurities in water. Electric battery. The electrode. How the cells were made. Object of plurality of cells. Volts, amperes and watts, and their definitions. A new boat determined on. Determining size of the boat. Recovering their life-boat. Visit to Observation Hill. Hunting for the lost flagpole and flag. Wreckage of a ship's boat discovered. The Professor sent for. Ascertain it is not part of their wrecked boat. Gathering up portions of the boat. Amazing discovery of skull and skeleton. Methods of determining age. Condition of the skull and teeth. Carrying the remains to the Cataract. The funeral. The seven ages in the growth of man. Sadness. The skeleton at the feast. Why is death necessary. One of the many reasons.

The endive. Chicory. The principle in the plant. The root. Curious manner of preparing it. A surprise for Harry. Making clay crocks. How to glaze or vitrify them. The use of salt in the process. A potter's wheel. Uses of the wheel. Its antiquity. Inspecting the electric battery. How it is connected up. Peculiarities in designating parts of the battery. Making the first spark. Necessary requirements for making a lighting plant. The arc light. What arc is and means. The incandescent light. Why the filament in bulb does not readily burn out. Oxygen as a supporter of combustion. Carbon, how made. Essential of the invention of the arc light. Determine again to explore cave. The lamps, spears and other equipment. Exciting discovery of a sail. Signaling the ship. The ship disappears. Discouragement. Determine to make a large flag and erect a new flagpole. Visiting the cave. Exploring it. Mounting one of the lamps on ledge for safety. Water not found where it was on previous visit. Discovery of a large domed chamber. Bringing forward the light on the ledge. Entering the chamber. Disappearance of the light from the ledge. The outlet of the chamber. Searching for the lost light. Determine to chart the cave. Steps taken. Surveying methods. Substitutes for paper and pencil. Soot. The base, the angle, and the projecting lines. How the side walls were charted.

An eventful day. Accounting for the disappearance of the water in the cave. The animal in the cave. Subterranean connection with the sea. Starting to make the large flag. Regulation flag determined on. The stripes and their colors, and how arranged. Their significance. The blue field and how studded. Its proportional size. How the yellow ramie cloth was made white. The bleaching process. Chloride of lime. The red color. The madder plant. Its powerful dyeing qualities. Coffee. The surprise party for Harry. Chicory leaves as a salad. Exhilarative substances and beverages. The cocoa leaf. Betel-nut. Pepper plants. Thorn apples. The ledum and hop. Narcotic fungus. "Baby's" experiment with the red dye test sample. Test samples in dyeing. Color-metric tests in analyzing chemicals. Reagents. The meaning and their use. Bitter-sweet. Blue dye. Copper and lime as coloring substance. The completed flag. A hunting trip for the pole. Making a trailer. A pole fifty feet long determined on. Tethering the yaks at the river. Searching for pole. The shell-bark hickory. The giant ant-killer. His peculiarities. Weight of hickory. Weight of the pole. Problem to convey it to the river. Determine to get the yaks. Swimming them across the river. The Professor absent on their return. Searching for the Professor. A shot heard. Going in the direction of the shot. Another shot from vicinity of the team. Returning in the direction of last shot. Find the Professor with team on way to river. How they made a circle without knowing it. A lesson in judgment.

Absence of Red Angel. The search. Sorrow at his flight. The morning breakfast. Reappearance of Red Angel with nuts. The honey pot and Red Angel. The voluntary exchange of nut for honey. How the orang reasoned. Preparation for pole-raising day. The capstans. The ropes and forked poles. The Angel invited to attend. How the pole was raised. Preparation to hoist the flag. The interference of Red Angel. How he mounted the pole. How honey was no temptation. George's discovery that Angel had eaten all the honey. The ceremony of raising the flag. Trying to sing the Star-Spangled Banner. The failure. Taking possession of the island in the name of the United States. Significance of the act of taking possession. Heraldry and the bending of the flag on the halliards. The banner and flag in ancient times. Leaving the flag at half-mast. The banner in the Bible. The necessity for making glass. Its early origin. The crystal of the ancients. What it is made of. The blowing process. An acid and an alkali. Sand as an acid. Lime, soda, and potash as alkalis. The result when united. Transparent and translucent. Opaqueness. Making sheet glass. Why the eye cannot see through rough glass. How sheets are prevented from being cracked.

Heating the crucibles for fusing glass. Eliminating impurities. Result of too much alkali. A test sample of glass. Speculation as to the inhabitants of the island. Their knowledge of the presence of savages. Mysterious occurrences while on the island. Determining to make further explorations for their own safety. The guns they had made. The hesitation about the trip inland. The hope for another ship. Discussing the probability of meeting the savages. Questions to be decided in building their boat. Possibilities of an island near them. Reasons for that view. A year from the time they sailed from New York. The spring. Planting a garden. Preparing the ground. The buckwheat. Propagation. Wild oats. How cultivated. Budding, grafting and inarching. Seedless fruit. Conclude to utilize the wrecked part of the life-boat as part of the new boat. Size of the new vessel. Its size and weight What is a ship. A brig, a sloop. Single masters. The sails. Different parts of the masts. The bowsprit and boom. The triangular sail.

The hunting expedition. The forest below South River. Suggestions of the Professor concerning the importance of that section. The trail through the dense woods. Wild animals. Different varieties of game. Directing course by the sun. Character of the country. Discovery of native huts. A vegetable garden. The surprising contents of the huts. Accidentally finding paper containing writing. Other articles of interest among the rubbish. A mineral spring. A monogrammed silver cup. The return journey. Discussing the articles found.

Trying to decipher the writing traces on the paper. Conclusions. The Professor's journey. Prospecting in the hills. Discovery of numerous fissures in the rocks. A skeleton in one of them. The telltale arrows. Mute evidence of the character of the inhabitants of the island.

Work on the new boat. Variety of their work. The regular hunting day. The joke on the Professor. Old age. How old age becomes a habit. The discussion on hunting. Deciding where to go. Conclude to visit the forests to the west. Provisioning for the journey. Reaching the edge of the main forest, accompanied by Red Angel. In the proximity of the Falls. Decided to go in that direction. Reach the river. Searching for the spot where the boat was left and from which place it had been taken. No traces of the mooring place. Examining driftwood and debris along river bank. Amazing discovery of one of Investigator's boats. Speculation as to the mystery. Evidence that it came over the Falls. Disappearance of the lockers of the boat, similar to those on their own. Discussion as to the fate of their companions. Decide to seclude the boat. Sudden appearance of Red Angel in excitement. Following him back to the location of the wagon. Disappearance of the yaks and wagon.