The waiter and diver understood in a minute.
Hurriedly they collected the tools—pickaxes, crowbars, chisels, and hammers—and they all set to work on the masonry.
But their momentary hopes soon subsided.
The mortar had, in the course of ages, become even harder than the stone itself.
It was impossible to make any impression upon it.
When they saw this, disappointment was depicted upon every countenance.
Jack flung down, in sheer despair, the chisel with which he had attempted to break the mortar.
As the implement fell upon the stones of the courtyard, Thyra's quick ear noticed the peculiar sound.
"It is hollow beneath here," she exclaimed, eagerly.
Again testing the floor in the same way, they became convinced that she was right.