me are small. By
striking an average we may be able to tell about how far from the
supposed location of the Pandora we ought to look for her."

The night passed without incident and as calmly and peacefully as
though they were all in some deep cave beneath a great mountain. In the
morning after breakfast Tom and his friends went outside the submarine
again and noted the weighted objects. Some had drifted farther than
others. Measurements were carefully taken, and then began a series of
intricate calculations.

The distance each object had drifted from the iron bar marker was
considered in reference to its size and shape. Also the elapsed time
was computed. The results were then compared, an average struck, and
then the size and weight of the Pandora, as nearly as they could be
ascertained, were figured. The resultant figures were compared, and Tom
announced:

"If we are anywhere near right in our conclusions we ought to begin to
search for the treasure-ship about four miles from here, in a general
northerly direction."

"Do you think she has drifted that far?" asked Ned.

"Fully that," Tom answered. "That is only our starting point--the
center of a new series of circles."

A moment later Tom gave the order to rise to the surface.

"Going up?" exclaimed Ned.

"Yes, I want to make some observations to determine our exact nautical
position."

"But suppose that other steam--"

"We'll have to take a chance. We can submerge quickly if we have to,
and I don't believe she's able to do that."

An observation was taken through the conning tower, however, before the
M. N. 1 went all the way up, and there was not a sail nor a smudge of
smoke on the horizon.

"So far so good," murmured Tom. "Now we'll 'shoot the sun,' and after
we submerge we'll begin our search in earnest. I think we are on the
right track now."

The observation was made at noon, and then, as nearly as possible, the
submarine was moved to a position approximately four miles north of the
place where the Pandora was supposed to have foundered.

"Down we go!" exclaimed Tom, and down they went.

The depth gauge showed more than a thousand feet below the surface when
the M. N. 1 came to rest. This was deeper than Tom had thought to find
the wreck, but his craft was able to withstand the pressure. A brief
wait, to make sure that everything was in readiness, was followed by
the beginning of the new search. In gradually widening circles the
craft moved