July 5, 1895.] 



SCIENCE. 



13 



PSYCHOLOGICAL NOTES (/.)• 

 THE SPECTRUM TOP. 



Eecent numbers of Nature have con- 

 tained not fewer than eleven communica- 

 tions on ' a spectrum top,' and the instru- 

 ment has been extensively discussed in 

 La Nature, The Scientific American and other 

 journals. Yet none of the writers seem to 

 know that the phen.omena were described 

 by Fechner in 1S3S (Foggendoi-fi's Annalen), 

 and were given a careful quantitative study 

 and correct explanation by Eood in 1860 

 (Am. Journal of Science and Arts'). They 

 have also been discussed and illustrated by 

 Briicke (Wiener Akad., 1864); by Aubert 

 (Physiologie der Netzliaut, 1865), and by 

 others. Indeed Aristotle described the 

 colored images following the exposure of 

 the eye to white light. In view of these 

 facts, it is somewhat amusing to find that 

 Messrs. Newton & Co. write to Nature 

 (March 14, 1895) that auyone supplying 

 the tops will be infringing their copyright. 



The form used by Aubert is shown on 

 the accompanying figure. If such a disk 

 (best enlarged) be revolved 10 to 40 times 

 per second colors will appear, varjdng 

 with the rate of revolution, the intensity of 

 the light, the observer, etc. Under favor- 

 able circumstances the colors may be of 



great brilliancy. They are undoubtedly 

 subjective, being due to the fact that the 

 components of white light vary in the time 

 they require to call up a sensation, and in 

 the time the sensation continues after the 

 light has been withdrawn. But while we 

 may refer these phenomena to inertia and 

 fatigue, we are very far from having a satis- 

 factory theory of all the facts of color vision. 



'AJSriMAIi MAGNETISM.' 



When a work on hypnotism is issued 

 as the thirty- fifth volume of a series of elec- 

 tro-technical primers, we do not look for 

 a critical treatise. Nor do we find one in 

 Magnetismus und Hypnotismus by G. W. Gess- 

 mann (Hartleben, Vienna). A full-page 

 picture of ' Lina ' in the attire and attitude 

 of a Sybil, reading a closed book through 

 the top of her head, is scarcely a part of 

 modern electrical science. The work is in 

 a way more interesting than others of the 

 long series of articles and books describing 

 in endless repetition the well ascertained 

 phenomena of hypnotism— more interesting 

 not only to the credulous, but also to men 

 of science, owing to the historical references 

 to Greek oracles, demonaic possession, mir- 

 aculous cures, Reichenbach's ' od,' etc. 

 Still such books do harm by making a 

 subject notorious through the popular in- 

 terest in the abnormal and the marvelous, 

 and really prevent the scientific investiga- 

 tion of hypnotism and its use as a thera- 

 peutic agent. Experiments on hypnotism 

 by untrained observers have much the same 

 results as giving or taking 4 ounces of alco- 

 hol in order to study the phenomena of intox- 

 ication. Hypnotism, dreaming and somnam- 

 bulism, intoxication, delirium, hysteria, in- 

 sanity, etc., are related phenomena the study 

 of which has thrown much light on the nor- 

 mal workings of the mind, but they are phe- 

 nomena that can be studied to advantage 

 only by students skilled in psychology, physi- 

 ology and pathology. J. McK. C. 



