On the Electric Discharge in Rarefied Gases. 173 



2 and 6 grams of mercury and 2 grams of brass are given 



below: — 



2 grams mercury at 15 0, 8 0. Corrected rise 15*6 

 2 „ brass at 15 a 9 0. „ „ 46*0 



6 „ mercury at 15'25 0. „ „ 48*5 



An inspection of these results, knowing that the specific 

 heat of brass is about three times that of mercury, will show 

 that the principle of the instrument is experimentally verified. 

 The bore of the thermometer-tube being, unfortunately, large, 

 necessitated a small rise; greater accuracy hence could not be 

 expected. It is hoped shortly, however, to make further expe- 

 riments with a new instrument having a much smaller bore, 

 and with other needed improvements that could not in a first 

 instrument be foreseen as wanting. 



XXVII. On the Electric Discharge in Rarefied Gases. 



By Dr. Eugen Goldstein*. 



[Plate IV.] 



Pakt I. 



On a new Differentiation of Electric Rays. 



THE object of a considerable portion of my researches is to 

 determine the laws of that remarkable motion which 

 radiates from the kathode in a rarefied gas, and which, being 

 characterized by propagation in straight lines, must be placed 

 side by side with the well-known forms of vibration which 

 constitute light-waves and sound-waves. Hittorf has shown 

 already that this motion (or, as he terms it, an electric ray) is 

 terminated whenever it strikes a solid obstacle. I have found, 

 during the past year, that with this termination by solid bodies 

 is connected a peculiar differentiation of the rays which strike 

 on the solid wall. This knowledge then led, further, to a 

 satisfactory explanation of the luminous processes, often men- 

 tioned in the literature of the subject, formed on the walls of 

 the enclosing vessel by the light from the negative pole. This 

 excitation of light has been hitherto termed fluorescence, and 

 ascribed to the high refrangibility of the rays emitted by the 

 whole mass of gas around the negative pole. It was, moreover, 



* Translated from a separate impression, communicated by the Author, 

 from the Monatsberichte der koniglichen Akademie der Wissenschaften zu 

 Berlin for January 1880. Prof. Ilelmholtz, in presenting these researches 

 for publication, for the prosecution of which the author had received 

 assistance from the "Royal Academy, observed that the first paper formed a 

 part of a report presented at the meeting- of Jan. 28, 1878, the second (on 

 Electric Luminous Phenomena in Gases) part of a report presented on the 

 29th October, 1879, 



