the age of passion for the purpose of gaining experience by helping older teachers; then, in fully ripe age, to fertilize the new generation with the best essence of one's own thought. And when a Prophet denounces a "curse" on young men whom impatient ambition makes neglectful of their elders, he is only speaking from the same scientific stand- point as a doctor who predicts future debility as the consequence of any physical sort of premature indulgence.
Several portions of this work were suggested by the conversations of Dr. Alfred Wiltshire, who had spent many years in the study of periodicity and of occasional reversal of attitude, as agents in the development of the human faculties, physical and mental. The foregoing paragraph is the substance of much which he said to me before his disease was apparent to others, but after he knew himself to be a doomed man. He told me that he had made his discovery of the danger of original work done young, too late to save himself; he hoped that his sorrowful experience might be of use in warning others.
The nature of my work precludes the possibility of specifying in detail the precise extent of my obligations to my various teachers. But one motive which spurs me on to complete it is the desire to keep the promise I made when Dr. Wiltshire was dying; that his children should know all I could tell them of the value of their father's life-work.
The most beautiful and powerful of all logical formulae is also the simplest. It is the great Master Key of Prophecy; used, as such, by the mathematician Boulanger; and handed down, (for those who have eyes to
