t is wonderful! It is
providential! It is the finger of Heaven! Pen and ink, and let me work it
out."

In his excitement he got up without assistance, and was soon busy
calculating the longitude of Godsend Isle.

CHAPTER XL.

"THERE," said he. "Now the latitude I must guess at by certain
combinations. In the first place, the slight variation in the length of
the days. Then I must try and make a rough calculation of the sun's
parallax. And then my botany will help me a little; spices furnish a
clew; there are one or two that will not grow outside the tropic. It was
the longitude that beat me, and now we have conquered it. Hurrah! Now I
know what to diffuse, and in what direction; east, southeast; the ducks
have shown me that much. So there's the first step toward the impossible
problem."

"Very well," said Helen; "and I am sure one step is enough for one day. I
forbid you the topic for twelve hours at least. I detest it because it
always makes your poor head so hot."

"What on earth does that matter?" said Hazel, impetuously, and almost
crossly.

"Come, come, come, sir," said Helen authoritatively; "it matters to me."

But when she saw that he could think of nothing else, and that opposition
irritated him, she had the tact and good sense not to strain her
authority, nor to irritate her subject.

Hazel spliced a long, fine-pointed stick to the mast-head, and set a
plank painted white with guano at right angles to the base of the mast;
and so, whenever the sun attained his meridian altitude, went into a
difficult and subtle calculation to arrive at the latitude, or as near it
as he could without proper instruments. And he brooded and brooded over
his discovery of the longitude, but unfortunately he could not advance.
In some problems the first step once gained leads, or at least points, to
the next; but to know whereabouts they were, and to let others know it,
were two difficulties heterogeneous and distinct.

Having thought and thought till his head was dizzy, at last he took
Helen's advice and put it by for a while. He set himself to fit and
number a quantity of pearl-oyster shells, so that he might be able to
place them at once, when he should be able to recommence his labor of
love in the cavern.

One day Helen had left him so employed, and was busy cooking the dinner
at her own place, but, mind you, with one eye on the dinner and another
on her patient, when suddenly she heard him shouting very loud,