THE X-RAYS. 143 



tus covered with black paper. The picture is weak, but unmistakably 

 correct. 



15. I have much sought to obtain interference phenomena with 

 X-rays, but unfortunately — perhaps on accountof their slight intensify — 

 without result. 



16. Experiments have been begun to see if electrostatic forces can 

 in any way influence X-rays, but these are not yet finished. 



17. If the question is asked what the X-rays — which certainly are 

 not cathode rays — really are, one might at first, on account of their 

 lively fluorescent and chemical action, compare them to ultra-violet 

 light. But here one falls upon serious difficulties. Thus, if the X-rays 

 were ultra-violet light, then this light must possess the following 

 characteristics: 



(ft) That in passing from air into water, carbon bisulphide, aluminum, 

 rock salt, glass, zinc, etc., it experiences no notable refraction. 



{h) That it is not regularly reflected by these substances. 



(c) That it can not be polarized by the usual materials. 



{(1) That its absorption by substances is influenced by nothing so 

 much as by their density. 



In other words, one must assume that these ultra-violet radiations 

 comport themselves quite differently from all previously known infra- 

 red, visible, and ultra violet rays. 



I have not been able to admit this, and have sought some other 

 explanations. 



A kind of relation seems to subsist between the new radiaticfii and 

 light radiation, or at least the shadow formation, the fluorescence, and 

 the chemical action, which are common phenomena of these two kinds 

 of radiation, point in this direction. It has been long known that 

 longitudinal as well as transverse vibrations are possible in the ether, 

 and according to various physicists must exist. To be sure, their 

 existence has not, up to the present time, been proved, and hence their 

 characteristics have not thus far been experimentally investigated. 



Should not the new radiations be ascribed to longitudinal vibrations 

 in the ether? I may say that in the course of the investigation this 

 hypothesis has impressed itself more and more favorably with me, and 

 I venture to propose it, although well aware that it requires much 

 further examination. 



WtJKZBUEa, Physik. Institut d. Univ., December, 1895. 



II. — UPON A NEW KIND OP RAYS (ABSTRACT).' 



As my work must be interrupted for several weeks, I take the opj)or- 

 tunity of presenting in the following some new results : 



18. At the time of my first publication I was aware that the X-rays 



1 Translation of a portion of the paper by Professor Rontgen in the Sitzungsber. 

 der Wlirzburger Physik-Medic. Gesellschaft, Jahrg. 1895, as reprinted in Annalen 

 der Physik und Chemie, 64, p. 12, 1898. 



