A HISTORY OF SCIENCE 



first as a rumor, little credited; then as a pronounced 

 report; at last as a demonstration. It told of a new 

 manifestation of energy, in virtue of which the interior 

 of opaque objects is made visible to human eyes. One 

 had only to look into a tube containing a screen of a 

 certain composition, and directed towards a peculiar 

 electrical apparatus, to acquire clairvoyant vision more 

 wonderful than the discredited second -sight of the 

 medium. Coins within a purse, nails driven into wood, 

 spectacles within a leather case, became clearly visible 

 when subjected to the influence of this magic tube ; and 

 when a human hand was held before the tube, its bones 

 stood revealed in weird simplicity, as if the living, pal- 

 pitating flesh about them were but the shadowy sub- 

 stance of a ghost. 



Not only could the human eye see these astounding 

 revelations, but the impartial evidence of inanimate 

 chemicals could be brought forward to prove that the 

 mind harbored no illusion. The photographic film re- 

 corded the things that the eye might see, and ghostly 

 pictures galore soon gave a quietus to the doubts of the 

 most sceptical. Within a month of the announce- 

 ment of Professor Roentgen's experiments comment 

 upon the "X-ray" and the "new photography" had 

 become a part of the current gossip of all Christendom. 



It is hardly necessary to say that such a revolution- 

 ary thing as the discovery of a process whereby opaque 

 objects became transparent, or translucent, was not 

 achieved at a single bound with no intermediate dis- 

 coveries. In 1859 the German physicist Julius Pliicker 

 (1801-1868) noticed that when there was an electrical 

 discharge through an exhausted tube at a low pressure, 



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