294 LIGHT SCIENCE FOR LEISURE HOURS. 



observed some years since, and a set of carte photo : 

 graphs were sent from America to Dr. "Walker, of 

 Edinburgh, in which photographic phantoms were very 

 obviously, however indistinctly, discernible. More 

 recently an English photographer noticed a yet stranger 

 circumstance, though he was too sensible to seek for a 

 supernatural interpretation of it. "When he took a 

 photograph with a particular lens, there could be seen 

 not only the usual portrait of the sitter, but at some 

 little distance a faint " double," exactly resembling the 

 principal image. Superstitious minds might find this 

 result even more distressing than the phantom photo- 

 graphic friend. To be visited by the departed through 

 the medium of a lens, is at least not more unpleasing 

 than to hold converse with spirits through an ordi- 

 nary " rapping " medium. But the appearance of a 

 "double" or "fetch," has ever been held by the 

 learned in ghostly lore to signify approaching death. 



Fortunately, both one and the other appearance can 

 be very easily accounted for without calling in the aid 

 of the supernatural. At a recent meeting of the Pho- 

 tographical Society it was shown that an image may 

 often be so deeply impressed on the glass that the sub- 

 sequent cleaning of the plate, even with strong acids, 

 will not completely remove the picture. "When the 

 plate is used for receiving another picture, the original 

 image makes its reappearance, and as it is too faint to 

 be recognizable, a highly-susceptible imagination may 



