NOTES ox KONTGEN KAYS 575 



shown that some of the rays penetrate vulcanite and other opaque 

 bodies, and we have only to look at an unpainted door, on the other 

 side of which the sun is shining, to convince ourselves that sunlight 

 penetrates wood to a considerable depth. 



As to the theory of the Eontgen rays we know little. If the rays 

 are vibrations we can readily determine a rough limit to their length, 

 from the sharpness of the shadows. 



Thus our photographs have such sharpness that the complete waves 

 cannot be more than -0005 cm. long, but are probably much shorter. 

 This is independent of whether the waves are longitudinal like sound 

 or transverse like light, and of course only applies to that portion of 

 them which affects the photographic plate. There may be others of 

 larger size that do not affect the plate. 



All efforts to bend the rays from their course, either within or with- 

 out the tube, by means of a strong magnetic field, have failed, both in 

 our hands and in those of others, and thus, if the rays are radiant parti- 

 cles of matter, they cannot be highly charged particles like the cathode 

 rays. The rays are not refracted by any solid bodies so far tried, and 

 this seems to be against their being waves either in air or ether. They 

 pass through solid bodies, and thus their wave-lengths cannot be very 

 small. We have before seen that it cannot be very great. They cannot 

 be sound waves as they proceed for some distance through a very perfect 

 vacuum. 



Altogether we are at a loss for a theory. If we have not yet got a 

 satisfactory theory of light after more than a hundred years of labor, 

 how can we hope to have a theory of the Kontgen rays after knowing 

 of them for only a few months? Let us suspend our judgment for a 

 while, and let us, above all things, be willing to alter our opinions at 

 any moment when fresh light appears. 



