,
the line will cross line 1 at C."

"That is correct. Now, if it is one inch from A to B, we may use that
inch as a measurement to get the distance along the line."

"Let me step it off," said Harry. "I find it is just two and
three-quarters inches."

"What was the distance, in feet from A to B?" asked John.

"I have the figures here," said George. "We found it was six hundred and
ninety feet."

"If, now, you will multiply 690 by 2-3/4, we shall have the distance
from this point A, and yonder point, or headland C."

[Illustration: _Fig. 6. The Second Limb._]

"I make it out to be just 1897.5," was Harry's conclusion.

The boys, together with John and a half dozen of the natives, went along
the shore, and mounted the point C, and from that place selected another
point in a southerly direction, and again made the same calculations.

The vessel in the meantime was put under sail and anchored a mile
below, giving the surveying party time to make several triangulations,
and late in the afternoon the party came on board, tired and ready to
take a rest.

From the position taken up by the ship they could see a long stretch of
shore line, practically straight, trending toward the southeast, and
with their glass could see, miles away, a headland which afforded a
pronounced point for observation.

The next morning the same parties rowed to the shore, and Uraso was left
with the party to guard the shore boat, while Muro accompanied John and
the boys. On this occasion John issued the following instruction:

"The long point which you see in the distance is, probably, 15 miles
beyond. It is not more than that, but this clear atmosphere is liable to
deceive. I have instructed Sutoto to wait until one o'clock today, and
if by that time there is no word from us Uraso will return to the ship,
and you will take up anchor and steer for the headland beyond."

"So that you may understand our movements, we will strike into the
interior, taking a course due east, for ten miles, or thereabout, and
then turn to the south, and reach the sea near the place where the
vessel will be located."

"I understand, now, how the distance can be measured by triangulation on
land; but how to get the distances, on shipboard, is what puzzles me,"
said Harry.

John smiled as he replied: "I knew you would come to that sooner or
later, so I prepared a little sketch (Fig. 7), which shows the bow of a
vessel, and the tall mast. The lines from A to