February 14, 1896.] 



SCIENCE. 



231 



15. I have sought for interference 

 effects of the X-rays, but possibly, in con- 



ft'L"' 



Fig. 1. — Photograph of the bones in the fingers of a 

 living human hand. The thiril finger has a ring 

 upon it. 



sequence of their small intensity, without 

 result. 



16. Researches to investigate whether 

 electrostatic forces act on the X-rays are 

 begun, but not yet concluded. 



17. If one asks, what then are these 

 X-rays ; since they are not cathode rays, 

 one might suppose, from their power of excit- 

 ing flourescence and chemical action, them 

 to be due to ultra-violet light. In opposi- 

 tion to this view a weighty set of considera- 

 tions presents itself. If X-rays be indeed 

 ultra-violet light, then that light must pos- 

 sess the foiling properties. 



(a) It is not refracted in passing from 

 air into water, carbon bisulphide, alumin- 

 ium, rock salt, glass or zinc. 



(6) It is incapable of regular reflection 

 at the surfaces of the above bodies. 



(c) It cannot be polarized by any ordi- 

 nary polarizing media. 



(d) The absorption by various bodies 

 must depend chiefly on their density. 



That is to saj', these ultra-violet rays 

 must behave quite differently from the visi- 

 ble, infra-red, and hitherto known ultra- 

 violet rays. 



These things appear so unlikely that I 

 have sought for another hypothesis. 



A kind of relationship between the new 

 rays and light rays appears to exist; at least 

 the formation of shadows, fluorescence, and 

 the production of chemical action point in 

 this direction. Now it has been known for 

 a long time that, besides the transverse vi- 

 brations which account for the phenomena 

 of light, it is possible that longitudinal vi- 

 brations should exist in the ether, and ac- 

 cording to the view of some physicists must 

 exist. It is granted that their existence 

 has not yet been made clear, and their 

 properties are not experimentally demon- 

 strated. Should not the new raj's be as- 

 cribed to longitudinal waves in the ether ? 



I must confess that I have in the course 

 of this researcfi made myself more and 

 more familiar with this thought, and ven- 

 ture to put the opinion forward, while I am 

 quite conscious that the hypothesis ad- 

 vanced still requires a more solid founda- 

 tion. W. C. RONTGEN. 



BONTGEN BAYS. 

 Professor Eontgen's discovery brings to 

 a close a most interesting chapter in the 

 history of electricity; it is the chapter 

 dealing with electric discharges through 

 rarefied gases. Experiments on electric dis- 

 charges through vacua have for quite a long 

 period now attracted the attention of phy- 

 sicists. Elaborate accounts of these ex- 

 periments can be found in the transactions 

 of learned societies throughout the last 

 century. A systematic research into the 

 various phenomena accompanying vacuum 

 discharges dates from the time of Faraday. 

 Pliicker, Hittorf and Goldstein in Ger- 

 many, and Spottiswoode and Crookes in 

 England, may be mentioned as the foremost 



