d some fifty feet wide, over which the sea makes a clean
breach in heavy weather; but the lagoon is about five miles long and
three miles wide, with good anchorage for ships in a pretty uniform
depth of ten fathoms. Two miles due west of this island there is a
shoal, some seven miles long, by from two to four miles wide, with
twenty-eight feet of water over it. And this shoal is almost entirely
covered with pearl-oysters, yielding some of the finest and most perfect
gems that I have ever seen.' Now, what think you of that, my friend.
Is that good enough for you?" demanded the professor.

"Quite good enough," answered Sir Reginald. "Now, skipper," he
continued, turning to Mildmay, "how far off is this famous oyster-bed,
and how long will it take us to get there?"

"What did you say is the position of the spot, Professor?" asked
Mildmay.

The professor restated the longitude.

"Um!" observed Mildmay, figuring upon a piece of paper that he drew from
his pocket; "it is a goodish step from here to there! roughly, about
seven thousand miles, as the crow flies. As to how long it will take us
to get there; we can do the distance in sixty hours, by going aloft into
the calm belt, shutting ourselves in, and going full speed ahead.
Otherwise--"

"Thanks, very much; and never mind the `otherwise,'" answered Sir
Reginald. "This is going to be a _sea_ trip; and we are going to do at
least a part of it in leisurely fashion, say, about ten to fifteen knots
an hour. When we are tired of that, and at night, we can go aloft and
put on the speed if we wish. And, now that I come to think of it, is
there any reason why we should not start at once?"

No one, it appeared, had any reason to advance against the baronet's
proposal. Accordingly, he and Mildmay forthwith adjourned to consult
the chart and lay off the course; and ten minutes later the remainder of
the party, who were still sitting on deck, awaiting the return of the
absentees, became conscious of the fact that the night-breeze had
suddenly strengthened; and when they looked about them in search of an
explanation, they saw the sea about three hundred feet beneath them, and
the land slipping away into the gloom of the night astern.

The travellers had been at sea a week, pottering along on the surface
during the day, and rising some three hundred feet into the air at
night--just high enough, in fact, to take them over and clear of the
masts of any ships that they migh