at a high rate of
speed with the wiper in the bore, and during the rotation the wiper is
drawn in and out. This operation should be continued for an hour at
least, frequently withdrawing it to add more of the polishing grit."

"What is the best grit to use?"

"If we can find a sample of the adamantine spar, in sufficient
quantities, it would be the best substance."

"What kind of material is that?"

"It is a substance known as corundum."

"Is that the same as emery?"

"What is known as emery is the more or less impure product from the same
source. I think I have stated heretofore that both of these products
come from the precious gems; the blue variety is known under the name of
sapphire; the red as ruby; the yellow as oriental topaz, and the violet
as oriental amethyst."

During that and the following day the Professor spent some time in
prospecting for the gems, but if he succeeded in finding any samples he
did not make the discovery known.

A few days after this Harry announced that he was ready to lay the keel
of the new boat. All the material had been prepared, and was at the
beach. Prior to this the island had been visited by a heavy storm. They
had been frequent within the past month, but this was not considered
unusual.

The Professor insisted that a temporary shed should be erected to cover
the material, as moisture would make it very undesirable for the vessel,
and a day was occupied in putting up the structure.

An entire week thus passed, every hour of which was devoted with the
utmost diligence to the various enterprises. The keel was laid and the
work of putting on the bottom boards was progressing rapidly. One night,
a few days after the laying of the keel, a brisk wind sprang up, which
continued during the night, increasing in fury, and in the morning
evidences were seen on all sides of the effect of the tempest.

"It seems very singular," was George's observation, "that we should have
such terrible winds here."

The Professor had evidently expected the storms. "Do you remember the
experience we had less than a year ago? We had five days of this on the
ocean."

"I had forgotten that. Do they occur every year?"

"You may have heard of the monsoons, a periodical wind in the Indian
Ocean, which is a northeast wind, and they blow with greater or less
force from November to March."

"What causes them to blow with such regularity during those periods?"

"Ah! that is one of the things whic