Of late, some of our learned men have given a particular attention to a subject hitherto branded with the mark of “superstition.” They begin speculating on hypothetical and invisible worlds. The authors of the _Unseen Universe_ were the first to boldly take the lead, and already they find a follower in Professor Fiske, whose speculations are given in the _Unseen World_. Evidently the scientists are probing the insecure ground of materialism, and, feeling it trembling under their feet, are preparing for a less dishonorable surrender of arms in case of defeat. Jevons confirms Babbage, and both firmly believe that every thought, displacing the particles of the brain and setting them in motion, scatters them throughout the universe, and think that “each particle of the existing matter must be a register of all that has happened.”[309] On the other hand, Dr. Thomas Young, in his lectures on natural philosophy, most positively invites us to “speculate with freedom on the possibility of independent worlds; some existing in different parts, others _pervading each other, unseen and unknown_, in the same space, and others again to which space may not be a necessary mode of existence.” If scientists, proceeding from a strictly scientific point of view, such as the possibility of energy being transferred into the invisible universe—and on the principle of continuity, indulge in such speculations, why should occultists and spiritualists be refused the {186} same privilege? Ganglionic impressions on the surface of polished metal, are registered and may be preserved for an indefinite space of time, according to science; and Professor Draper illustrates the fact most poetically. “A shadow,” says he, “never falls upon a wall without leaving thereupon a permanent trace, a trace which might be made visible by resorting to proper processes.... The portraits of our friends, or landscape-views, may be hidden on the sensitive surface from the eye, but they are ready to make their appearance, as soon as proper developers are resorted to. A spectre is concealed on a silver or glassy surface, until, by our necromancy, we make it come forth into the visible world. Upon the walls of our most private apartments, where we think the eye of intrusion is altogether shut out, and our retirement can never be profaned, there exist the vestiges of all our acts, silhouettes of whatever we have done.”[310] If an indelible impression may be thus obtained on inorganic matter, and if nothing is lost or passes completely out of existence in the universe, why such a scientific levee of arms against the authors of the _Unseen Universe_? And on what ground can they reject the hypothesis that “_Thought, conceived to affect the matter of another universe simultaneously with this, may explain a future state_?”[311]