That was what tearful Miss Iris thought, or tried to persuade herself to think.  Perhaps her cogitations would not bear strict analysis.  Perhaps she harbored a sweet hope that the future might yet contain bright hours for herself and the man who was so devoted to her.  She refused to believe that Robert Anstruther, strong of arm and clear of brain, a Knight of the Round Table in all that was noble and chivalric, would permit his name to bear an unwarrantable stigma when—­and she blushed like a June rose—­he came to tell her that which he had written.

The sailor returned hastily, with the manner of one hurrying to perform a neglected task.  Without any explanation to Iris he climbed several times to the ledge, carrying arm-loads of grass roots which he planted in full view.  Then he entered the cave, and, although he was furnished only with the dim light that penetrated through the distant exit, she heard him hewing manfully at the rock for a couple of hours.  At last he emerged, grimy with dust and perspiration, just in time to pay a last visit to Summit Rock before the sun sank to rest.  He asked the girl to delay somewhat the preparations for their evening meal, as he wished to take a bath, so it was quite dark when they sat down to eat.

Iris had long recovered her usual state of high spirits.

“Why were you burrowing in the cavern again?” she inquired.  “Are you in a hurry to get rich?”

“I was following an air-shaft, not a lode,” he replied.  “I am occasionally troubled with after wit, and this is an instance.  Do you remember how the flame of the lamp flickered whilst we were opening up our mine?”

“Yes.”

“I was so absorbed in contemplating our prospective wealth that I failed to pay heed to the true significance of that incident.  It meant the existence of an upward current of air.  Now, where the current goes there must be a passage, and whilst I was busy this afternoon among the trees over there,”—­he pointed towards the Valley of Death—­“it came to me like an inspiration that possibly a few hours’ hewing and delving might open a shaft to the ledge.  I have been well rewarded for the effort.  The stuff in the vault is so eaten away by water that it is no more solid than hard mud for the most part.  Already I have scooped out a chimney twelve feet high.”

“What good can that be?”

“At present we have only a front door—­up the face of the rock.  When my work is completed, before tomorrow night I hope, we shall have a back door also.  Of course I may encounter unforeseen obstacles as I advance.  A twist in the fault would be nearly fatal, but I am praying that it may continue straight to the ledge.”

“I still don’t see the great advantage to us.”

“The advantages are many, believe me.  The more points of attack presented by the enemy the more effective will be our resistance.  I doubt if they would ever be able to rush the cave were we to hold it, whereas I can go up and down our back staircase whenever I choose.  If you don’t mind being left in the dark I will resume work now, by the light of your lamp.”