Together they all three set to work on it, and after half an hour's work Sandy cried:
"Hooray! One more shove, and down she comes!"
The shove was given, and with a will. As the Scotch lad had prophesied, the partition fell with a crash, amid a cloud of dust. As it fell, a strong whiff of fresh air blew in their faces.
"It's as I thought," declared Sam Hartley, "this tunnel opens on the lake shore."
"Did that rascally gang dig it?" wondered Sandy.
"No," rejoined the detective, "I guess it's of Indian origin. There are drawings on the wall. In one case that I worked up, I had to study such things, so that I recognize them. I guess Indians dug this tunnel, and then the gang, when they found it, speedily took advantage of the fact that it was here to make a secret 'getaway' place."
As we know, from what old Sam on board the submarine had said, such was the case.
"Well, let's get to the air and find out what's going forward," said Jack impatiently.
The others were nothing loath. But they found their way barred by a strange assortment of encumbrances in the passage-way. Bales, barrels, boxes, kegs, all these cluttered it up, almost to its roof. It was hard work effecting a passage among them.
"Boys, do you realize what we've stumbled on?" said Sam Hartley, as they worked at the task of displacing them.