128 Dr. Hammond and the [vm. 



it myself, I should not have believed it ! " The com- 

 monest acts of perception are so liable to be warped 

 by hypothesis (a fact which conjurors like Houdin 

 consummately understand) that it is quite useless to 

 conjecture what our witnesses may really have seen, 

 unless we know much more than they are likely to 

 tell us of the physical and mental conditions under 

 which their seeing was done. At a meeting of spiri- 

 tualists in Boston, Mr. Robert Dale Owen once saw 

 what he took to be an " apparition in shining rai- 

 ment," being quite clear in his mind that no deception 

 or illusion was possible under the circumstances. But 

 Dr. Hammond, making a diagram of the rooms from 

 data contained in Mr. Owen's account, shows that, 

 with the greatest ease, a " woman in white " might 

 have been brought into the room and illuminated by 

 means of a dark lantern without awakening suspi- 

 cion. The case of Angelique Cottin, the famous 

 "electric girl," is equally instructive. After tipping 

 tables, repeUing books, brushes, and other small 

 objects, and disturbing magnetic needles before nu- 

 merous " intelligent audiences," her alleged powers 

 were carefully investigated by a committee of the 

 Academy of Sciences, consisting of Arago, Becquerel, 

 Geofifroy St. Hilaire, and others. Tables, books, 

 brushes, and magnetic needles, all kept most 



