"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 about under water.
If the voyagers had expected to locate at once the treasure-ship, they would have been disappointed. For the first day gave no signs. But Tom had not promised immediate results, and no one gave up hope.
It was shortly after noon on the second day of the search at the new location that, as they were proceeding at rather greater speed than usual, something happened.
Ned had just suggested that he and Tom might go out and try the current-setting experiments again, when suddenly they were both thrown off their feet by a terrific jar and concussion. The M. N. 1 seemed to reel back, as if from a great blow.