“Necessarily so, because I can only lead you to my discovery step by step,” replied the other steadily.  “I wish you to be thoroughly prepared for anything that may happen, so that you can deal intelligently with results that might otherwise overwhelm you.”

“Overwhelm—?” faltered his listener.

“Might, I said.  Note carefully my use of words, for they are accurately chosen.  Before I can tell you all I must submit you, for your own sake, to certain tests—­chiefly to the test of Alteration of Form by Sound.  It is somewhat—­er—­alarming, I believe, the first time.  You must be thoroughly accustomed to these astonishing results before we dare to approach the final Experiment; so that you will not tremble.  For there can be no rehearsal.  The great Experiment can only be made once ... and I must be as sure as possible that you will feel no terror in the face of the Unknown.”

IV

Spinrobin listened breathlessly.  He hesitated a moment after the other stopped speaking, then slewed round on his slippery chair and faced him.

“I can understand,” he began, “why you want imagination, but you spoke of courage too?  I mean,—­is there any immediate cause for alarm?  Any personal danger, for instance, now?” For the clergyman’s weighty sentences had made him realize in a new sense the loneliness of his situation here among these desolate hills.  He would appreciate some assurance that his life was not to be trifled with before he lost the power to withdraw if he wished to do so.

“None whatever,” replied Mr. Skale with decision, “there is no question at all of physical personal injury.  You must trust me and have a little patience.”  His tone and manner were exceedingly grave, yet at the same time inspired confidence.

“I do,” said Spinrobin honestly.

Another pause fell between them, longer than the rest; it was broken by the clergyman.  He spoke emphatically, evidently weighing his words with the utmost care.

“This Chord,” he said simply—­yet, for all the simplicity, there ran to and fro behind his words the sense of unlawful and immense forces impending—­“I need for a stupendous experiment with sound, an experiment which will lead in turn towards a yet greater and final one.  There is no harm in your knowing that.  To produce a certain transcendent result I want a complex sound—­a chord, but a complete and perfect chord in which each note is sure of itself and absolutely accurate.”

He waited a moment.  There was utter silence about them in the room.  Spinrobin held his breath.