“You have quite a river there,” he remarked.

She nodded.

“That used to be the principal waterway from Burnham village.  Quite a large boat can get down now at high tide.”

They entered the house and Isabel gave a little gesture of dismay.  She clutched for a moment at Granet’s arm.  An elderly man, dressed in somber black clothes disgracefully dusty, collarless, with a mass of white hair blown all over his face, was walking up and down the hall with a great pair of horn-rimmed spectacles clutched in his hand.  He stopped short at the sound of the opening door and hurried towards them.  There was nothing about his appearance in the least terrifying.  He seemed, in fact, bubbling over with excited good-humour.

“Isabel, my dear,” he exclaimed, “it is wonderful!  I have succeeded!  I have changed the principles of a lifetime, made the most brilliant optical experiment which any man of science has ever ventured to essay, with the result—­well, you shall see.  I have wired to the Admiralty, wired for more work-people.  Captain Chalmers, is it not?” he went on.  “You must tell your men to double and redouble their energies.  This place is worth watching now.  Come, I will show you something amazing.”

He turned and led them hastily towards the back door.  Isabel gripped Granet’s arm.

“He thinks you are the officer in command of the platoon here,” she whispered.  “Better let him go on thinking so.”

Granet nodded.

“Is he going to take us to the workshop?”

“I believe so,” she assented.

They had hard work to keep up with Sir Meyville as he led them hastily down the little stretch of shingle to where a man was sitting in a boat.  They all jumped in.  The man with the oars looked doubtfully for a moment at Granet, but pulled off at once when ordered to do so.  They rowed round to the front of the queer little structure.  A man from inside held out his hand and helped them up.  Another young man, with books piled on the floor by his side, was making some calculations at a table.  Almost the whole of the opening of the place was taken up by what seemed to be a queer medley of telescopes and lenses pointing different ways.  Sir Meyville beamed upon them as he hastily turned a handle.

“Now,” he promised, “you shall see what no one has ever seen before.  See, I point that arrow at that spot, about fifty yards out.  Now look through this one, Isabel.”

The girl stooped forward, was silent for a moment, then she gave a little cry of wonder.  She clutched Granet’s arm and made him take her place.  He, too, called out softly.  He saw the sandy bottom covered with shells, a rock with tentacles of seaweed floating from it, several huge crabs, a multitude of small fishes.  Everything was clear and distinct.  He looked away with a little gasp.

“Wonderful!” he exclaimed.

Sir Meyville’s smile was beatific.