“I propose to provide at Diana’s Grove, as soon as it comes into my possession, an enormous amount of such sand, and shall take an early occasion of pouring it into the well-hole, which it will in time choke.  Thus Lady Arabella, in her guise of the White Worm, will find herself cut off from her refuge.  The hole is a narrow one, and is some hundreds of feet deep.  The weight of the sand this can contain would not in itself be sufficient to obstruct; but the friction of such a body working up against it would be tremendous.”

“One moment.  What use would the sand be for destruction?”

“None, directly; but it would hold the struggling body in place till the rest of my scheme came into practice.”

“And what is the rest?”

“As the sand is being poured into the well-hole, quantities of dynamite can also be thrown in!”

“Good.  But how would the dynamite explode—­for, of course, that is what you intend.  Would not some sort of wire or fuse he required for each parcel of dynamite?”

Adam smiled.

“Not in these days, sir.  That was proved in New York.  A thousand pounds of dynamite, in sealed canisters, was placed about some workings.  At the last a charge of gunpowder was fired, and the concussion exploded the dynamite.  It was most successful.  Those who were non-experts in high explosives expected that every pane of glass in New York would be shattered.  But, in reality, the explosive did no harm outside the area intended, although sixteen acres of rock had been mined and only the supporting walls and pillars had been left intact.  The whole of the rocks were shattered.”

Sir Nathaniel nodded approval.

“That seems a good plan—­a very excellent one.  But if it has to tear down so many feet of precipice, it may wreck the whole neighbourhood.”

“And free it for ever from a monster,” added Adam, as he left the room to find his wife.

CHAPTER XXV—­THE LAST BATTLE

Lady Arabella had instructed her solicitors to hurry on with the conveyance of Diana’s Grove, so no time was lost in letting Adam Salton have formal possession of the estate.  After his interview with Sir Nathaniel, he had taken steps to begin putting his plan into action.  In order to accumulate the necessary amount of fine sea-sand, he ordered the steward to prepare for an elaborate system of top-dressing all the grounds.  A great heap of the sand, brought from bays on the Welsh coast, began to grow at the back of the Grove.  No one seemed to suspect that it was there for any purpose other than what had been given out.

Lady Arabella, who alone could have guessed, was now so absorbed in her matrimonial pursuit of Edgar Caswall, that she had neither time nor inclination for thought extraneous to this.  She had not yet moved from the house, though she had formally handed over the estate.