"Now let's go back to the other tunnel," he continued, after the detonator and the fuse had been inserted and the latter fired. "There's no hurry; the explosion will not take place for five minutes."
As the moments sped, the lads awaited in breathless silence the sound of the detonation.
Presently a dull rumble echoed through the rocky passage, followed by a blast of air mingled with the acrid fumes of the cordite.
"Not so fast! Not so fast!" cautioned Mr. McKay, as the lads began to run towards the hitherto baffling barrier. "Some of the rock may be dislodged."
As it was, they were obliged to wait some considerable time, as the atmosphere in the tunnel was so vile that it was impossible to breathe with comfort. Then as the mist gradually cleared, the dull yellow glare of the lanterns revealed a mass of shattered woodwork where the door had stood; while a foot beyond was a barrier of steel rods, which, serving the purpose of a portcullis, had fallen from above.
"That's what we heard fall," observed Mr. McKay. "The idea was, I suppose, that any unauthorised person who escaped the lance-thrust on this side of the door would, on opening it, be impaled by the weapons concealed in the roof. Now to settle with this obstruction."
A few powerful strokes with an axe shattered enough bars to enable Mr. McKay to squeeze through, and, followed by his eager companions, he entered the mysterious cavern.
At first there was little to attract the attention of the explorers. The cave was of irregular form, being about fifty feet in length, thirty in breadth, and varying in height from twenty-five to six feet.
On the floor were six wooden chests, ordinary in appearance and apparently of simple construction; they would have easily been mistaken for seamen's chests placed in a lumber-room.
Striding up to the nearest one, Mr. McKay raised the lid. There was no creaking of rusty hinges, no glitter of gold and jewels to dazzle the eyes. The chest was empty!