hopes; and in return for your services, the worth of which you cannot realize, whatever guidance I can give you in the future for your physical and spiritual life, is yours.  I have done something for you, but not much—­I will do more.  Only, in communicating with me, I ask you to honour me with your full confidence in all matters pertaining to yourself and your surroundings—­then I shall not be liable to errors of judgment in the opinions I form or the advice I give.”

“I promise most readily,” I replied gladly, for it seemed to me that I was rich in possessing as a friend and counsellor such a man as this student of the loftiest sciences.

“And now one thing more,” he resumed, opening a drawer in the table near which he sat.  “Here is a pencil for you to write your letters to me with.  It will last about ten years, and at the expiration of that time you can have another.  Write with it on any paper, and the marks will be like those of an ordinary drawing-pencil; but as fast as they are written they disappear.  Trouble not about this circumstance—­write all you have to say, and when you have finished your letter your closely covered pages shall seem blank.  Therefore, were the eye of a stranger to look at them, nothing could be learned therefrom.  But when they reach me, I can make the writing appear and stand out on these apparently unsullied pages as distinctly as though your words had been printed.  My letters to you will also, when you receive them, appear blank; but you will only have to press them for about ten minutes in this”—­and he handed me what looked like an ordinary blotting-book—­“and they will be perfectly legible.  Cellini has these little writing implements; he uses them whenever the distances are too great for us to amuse ourselves with the sagacity of Leo—­in fact the journeys of that faithful animal have principally been to keep him in training.”

“But,” I said, as I took the pencil and book from his hand, “why do you not make these convenient writing materials public property?  They would be so useful.”

“Why should I build up a fortune for some needy stationer?” he asked, with a half-smile.  “Besides, they are not new things.  They were known to the ancients, and many secret letters, laws, histories, and poems were written with instruments such as these.  In an old library, destroyed more than two centuries ago, there was a goodly pile of apparently blank parchment.  Had I lived then and known what I know now, I could have made the white pages declare their mystery.”

“Has this also to do with electricity?” I asked.

“Certainly—­with what is called vegetable electricity.  There is not a plant or herb in existence, but has almost a miracle hidden away in its tiny cup or spreading leaves—­do you doubt it?”

“Not I!” I answered quickly.  “I doubt nothing!”

Heliobas smiled gravely.