Sir Henry stopped to rest.  “Let me,” offered Herold; and went on as the Englishman had done, holding up each spadeful for inspection.  And it was thus that we made a strange discovery.

We all saw it at the same time.  Embedded in the bluish earth was a small, egg-shaped piece of light-coloured stone.  And protruding from its upper surface was a tiny, blood-red pebble, no bigger than a good-sized shot.

Herold thrust the point of his spade under the stone, to lift it up.  Whereupon he gave a queer exclamation.

“Well, that’s funny!” holding the stone up in front of us.  “That little thing’s as heavy as—­as—­it’s heavier than lead!”

Sir Henry picked the stone off the spade.  Immediately the material crumbled in his hands, as though rotting, so that it left only the small, red pebble intact.  Sir Henry weighed this thoughtfully in his palm, then without a word handed it around.

We all wondered at the pebble.  It was most astonishingly heavy.  As I say, it was no bigger than a fair-sized shot, yet it was vastly heavier.

Afterward we weighed it, upstairs, and found that the trifle weighed over half a pound.  Considering its very small bulk, this worked out to be a specific gravity of 192.6 or almost ten times as heavy as the same bulk of pure gold.  And gold is heavy.

Inevitably we saw that there must be some connection between this unprecedentedly heavy speck of material and that lighter-than-air gem of mystery.  For the time being we were careful to keep the two apart.  As for the unexplained footsteps, they were still slightly audible, as the invisible creatures moved around the cellar.

At last we turned to go.  I let the others lead the way.  Thus I was the last to approach the steps; and it was at that moment that I felt something brush against my foot.

I stooped down.  My hands collided with the thing that had touched me.  And I found myself clutching—­

Something invisible—­something which, in that brilliant light, showed absolutely nothing to my eyes.  But my hands told me I was grasping a very real thing, as real as my fingers themselves.

I made some sort of incoherent exclamation.  The others turned and peered at me.

“What is it?” came Herold’s excited voice.

“I don’t know!” I gasped.  “Come here.”

But Sir Henry was the first to reach me.  Next instant he, too, was fingering the tiny, unseen object.  And such was his iron nerve and superior self-control, he identified it almost at once.

“By the lord!”—­softly.  “Why, it’s a small bird!  Come here.”

Another second and they were all there.  I was glad enough of it; for, like a flash, with an unexpectedness that startles me even now as I think of it—­

The thing became visible.  Right in my grasp, a little fluttering bird came to life.

XXVII