of metal. Bronze. Ancient guns. Manganese. Making
stocks for the guns. Commencing the hull of the new boat. Size of
the vessel. About shape or form of hulls. Momentum. Resistance. Red
Angel's attempt to whistle. Amusing performance. Teaching Red Angel
accomplishments. Vibration, the universal force.

III. THE HIDEEN MESSAGE

The new yoke for the yaks. Some of the mysteries. Discussion
concerning future discoveries. Rainbows. Musical pitch and colors.
Reflection and refraction. Riding the yaks. Completing some of the
guns. The trip after the wrecked wagon. Finding their runaway team.
Accounting for their disappearance. Prospecting. Sugar cane
discovered. Sorghum. The Tamarisk. Rigging up the lifeboat with
sails. Discovery of a hidden message in the lifeboat. Examining the
place where it was found. Determining the time when the message was
written. Rushing preparation of guns and ammunition. Galena. Lead.
Getting rid of the sulphur. Making bullets.

IV. THE TERRIBLE MONSOONS

Completing the guns. Description of the new ones. Polishing grit.
Emery. Corundum. Laying the keel of the big boat. Terrible winds.
The monsoons. Trade winds. Length of summers north and south of the
Equator. Disappearance of the flag from Observation Hill. George
and Angel's hunt for the flag. Disappointment. Angel finding the
flag. Angel's laugh. Facial expression in animals. Brass. The form
of bullets. Why pointed at one end and hollow in the other. Rifling
guns. Spiral movement. Molds for castings. The Professor's desire
to fully explore the cave. Weaving the sails for the new boat.
Angel's work on the loom.

V. THE VOYAGE FOR THE BENEFIT OF ANGEL, AND THE DISCOVERY

Completing the hull of the new boat. Making manilla rope. Decide to
take Angel along. Enticing him aboard. His consternation. Rounding
the cliffs. Discovering their first boat among debris. Taking it
along as a trailer. Sailing up Cataract River. Evidence that their
boat had been used by some one. Proof of its use by the natives.
One of the signs of civilization. Leverage. Fulcrum. Mechanical
powers. Delay of voyage owing to weather. Tourmaline. Harry's
invention. The bamboo tubes. Testing how fast the guns could be
loaded and fired. Cartridges. The marine works. The boats. Three
cheers for the new ship.