The Arab tells me to hurry, for he sees a cloud of sand to the
     south—­he thinks it is the party coming to murder me, and he
     doesn’t want to be found with me.  So good-bye again.

     Yours,

     David Innes.

A year later found me at the end of the railroad once more, headed for the spot where I had left Innes.  My first disappointment was when I discovered that my old guide had died within a few weeks of my return, nor could I find any member of my former party who could lead me to the same spot.

For months I searched that scorching land, interviewing countless desert sheiks in the hope that at last I might find one who had heard of Innes and his wonderful iron mole.  Constantly my eyes scanned the blinding waste of sand for the ricky cairn beneath which I was to find the wires leading to Pellucidar—­but always was I unsuccessful.

And always do these awful questions harass me when I think of David Innes and his strange adventures.

Did the Arabs murder him, after all, just on the eve of his departure?  Or, did he again turn the nose of his iron monster toward the inner world?  Did he reach it, or lies he somewhere buried in the heart of the great crust?  And if he did come again to Pellucidar was it to break through into the bottom of one of her great island seas, or among some savage race far, far from the land of his heart’s desire?

Does the answer lie somewhere upon the bosom of the broad Sahara, at the end of two tiny wires, hidden beneath a lost cairn?  I wonder.