Roentgen rays

Were it not that the power is possessed of changing these rays to light rays, man could know nothing of the Roentgen rays.

Or, instead, a photographic plate may be used, for the Roentgen rays affect the materials from which these plates are made.

A piece of uranium ore, as has been found in recent years, emits various kinds of rays related to the now famous X- or Roentgen rays, yet no indication comes directly through any of the five senses that such is the case.

The X- or Roentgen rays have been mentioned several times.

To the uninitiated all this disturbance about a few lines on the trunk of a tree seemed unintelligible and ridiculous, but to the print collectors it was considered a magnificent "find," ranking with the discovery of electricity or the Roentgen rays.