With regard to the second, though no sparkling elixir distilled from some rare flower, such as that Septimius Felton sought in Hawthorne's tale, has been discovered, the great scientist Metchnikoff has brought to light a preserver of youth more in keeping with the science of the day--namely, a microbe, possessing power to destroy the poison that produces age. Whether perpetual youth is to lead to immortality in the flesh will probably be a question for other centuries to discuss, though if Metchnikoff is right there is no reason why we should not retain our youthfulness all our lives in this century. Add to this, machinery run by the perpetual energy of radium--a possibility, if radium can ever be obtained in sufficient quantities to supply the needed power to keep modern civilization on its ceaseless "go"--and we may picture to ourselves, before the end of the twentieth century, youths of ninety starting forth on voyages of thirty years in radium ships, which, like the fairy watch of the Princess Rossetta, will never go wrong and will never need to be wound up, metaphorically speaking. It would almost seem as if some method of enlarging the earth, or of arranging voyages to the moon and Mars, would be necessary in order to give the new radium machinery sufficient scope for its activities. However, at present it seems unlikely that it will ever be possible to produce more than half an ounce of radium a year. As it would take a ton to run one ship for thirty years, and the expense would be something almost incalculable, it is a dream only to be realized by the inventing of methods by which the feeble radio-activity known to exist in many other substances can be utilized. These methods have not yet been invented, but it is a good deal that they have been thought of, for what man thinks of he generally seems to have the indomitable energy to accomplish.