Photographing the Unseen 



packing case, its side being perhaps five inches 

 from the Crookes tube. 



The professor explained the mystery of the tin 

 box, to the effect that it was a device of his own 

 for obtaining a portable dark-room. When he 

 began his investigations he used the whole room, 

 as was shown by the heavy blinds and curtains so 

 arranged as to exclude the entrance of all inter- 

 fering light from the windows. In the side of the 

 tin box, at the point immediately against the 

 tube, was a circular sheet of aluminum one 

 millimetre in thickness, and perhaps eighteen 

 inches in diameter, soldered to the surrounding 

 tin. To study his rays the professor had only 

 to turn on the current, enter the box, close the 

 door, and in perfect darkness inspect only such 

 light or light effects as he had a right to consider 

 his own, hiding his light, in fact, not under the 

 Biblical bushel, but in a more commodious box. 



" Step inside, " said he, opening the door, which 

 was on the side of the box farthest from the tube. 

 I immediately did so, not altogether certain 

 whether my skeleton was to be photographed 

 for general inspection, or my secret thoughts 

 held up to light on a glass plate. "You will find 

 a sheet of barium paper on the shelf, " he added, 

 and then went away to the coil. The door was 

 closed, and the interior of the box became black 

 darkness. The first thing I found was a wooden 

 stool, on which I resolved to sit. Then I found 

 the shelf on the side next the tube, and then the 

 sheet of paper prepared with barium platino- 

 97 



