VACUUM TUBES. 



RV C. M. RROOMALL. 



About three years ago the writer, in the course of some 

 electrical studies, was surprised to find that an ordinary incan- 

 descent electric light globe could be made to faintly glow 

 without the use of electrical apparatus. All that was neces- 

 sary to produce the light was to rapidly and lightly stroke or 

 rub the glass globe with the bare hand, when it would be 

 found that the interior of the bulb would glow with a momen- 

 tary faint bluish light. This light filled the whole interior of 

 the globe more or less, but was more intense at the point of 

 contact with the hand. 



The experiment excited some interest among the Institute 

 members, and as the various text books at hand gave no ref- 

 erence to such a phenomenon, many theories were advanced 

 to account for it. Although the light seemed in some way 

 attributable to electricity, its indifference to atmospheric con- 

 ditions, insulation, etc., made it difficult to reconcile with this 

 explanation. 



With the hope of obtaining a satisfactory explanation of 

 the phenomenon, a communication was sent to the Scientific 

 America)! under date of October iith, 1904, which communi- 

 cation appeared shortly after in the columns of that journal. 

 As the modus operandi of producing the light is fully described 

 in this communication f it is reproduced here, as follows : — 



" In some recent experiments the writer was astonished to 

 find that a vacuum tube could be made to glow without the 

 use of apparatus. This fact, perhaps familiar to some, will 

 be new to others, and being easily demonstrated, seems worth 

 describing. 



" If an ordinary incandescent light bulb or a Crookes tube 

 or radiometer tube is subjected to rapid friction with the hand, 

 it will be found that the whole interior of the tube glows with 

 a faint bluish light. The light lasts only during the actual 



