to draw an unlimited supply of power from gravity by simply changing the position of the crystal; for example, by raising it when lighter, and letting it fall when heavier.  This form of ’perpetual motion’ might be equally obtainable if Dr. Preston’s[3] theory of an ether as the cause of gravity be true.  Indeed, Professor Poynting is now engaged in searching for such a crystal, which, if discovered, will upset the second law of thermo-dynamics.  I merely mention this to show that science is on the track of concealed motive powers derived from the ether, and we cannot now tell what the engines of the future will be like.  For ought we know, the time is coming when there will be a regular mail service between the earth and Mars or Venus, cheap trips to Mercury, and exploring expeditions to Jupiter, Saturn, or Uranus.”

    [Footnote 3:  Philosophical Magazine, February, 1895.]

CHAPTER III.

A NEW FORCE.

     “SIR,

“I have read your article on the possibility of travelling to the other members of the Solar system with much interest.  It is a problem at which I, myself, have been working for a great many years, and I believe that I have now discovered a means of solving it in a practical manner.  If you would care to see my experiments, and will do me the honour of coming here, I shall be glad to show them in confidence any time you may appoint.—­Yours truly,

     “NASMYTH CARMICHAEL.”

The above letter, marked “Private,” was forwarded to me through the editor of The Day After To-morrow.  The writer of it was a total stranger to me, even by report, and at first I did not know what to make of it.  Was the man a charlatan, or a “crank?” There were no signs of craziness or humbug in his frank and simple sentences.  Had he really found out a way of crossing the celestial spaces?  In these days it is better not to be too sceptical as to what science will accomplish.  It is, in fact, wise to keep the mind open and suspend the judgment.  We are standing on the threshold of the Arcana, and at any hour the search-light of our intellect may penetrate the darkness, and reveal to our wondering gaze the depths of the inner mechanism of Nature.

I resolved to accept his invitation.

A few days later I presented myself at the home of my unknown correspondent.  It was a lonely little cottage, in the midst of a wild flat or waste of common ground on the outskirts of London.  I should say it had once been the dwelling of a woodman engaged in the neighbouring forest.  A tall, thick hedge of holly surrounded the large garden, and almost concealed it from the curiosity of an occasional wanderer on the heath.

Certainly it did not look the sort of place to find a man of science, and the old misgivings assailed my mind in greater force than ever.  Half regretting that I had come, and feeling in a dubious element, I opened the wicket, and knocked at the door.