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III. A Farther Examination of the Edison Effect in Glow 

 Lamps. By J. A. Fleming, M.A., D.Sc., F.R.S., Pro- 

 fessor of Electrical Engineering in University College, 

 London*. 



§1. rpHE experiments described in this paper had for their 

 X object the further examination of an effect which can 

 be produced in certain forms of electric incandescence lamps 

 and to which attention was first drawn by Mr. Edison in 1884. 

 This effect may be generally described as follows : — A carbon 

 filament incandescence lamp having 'the ordinary horse-shoe 

 loop carbon has a metallic plate placed in the exhausted bulb, 

 the plate being carried on a platinum wire sealed through the 

 globe, and fixed so as to stand up between the legs of the 

 horse-shoe (see fig. 1). If the lamp is set in action at the 



■Fig. 1. 



Fig. 2. 



usual incandescence by a continuous current of the proper 

 strength, and a suitable sensitive galvanometer is connected 

 between the insulated metal plate and the positive terminal of 

 the lamp, it will in general be found to indicate a current of 

 some milliamperes flowing through it. The direction of this 

 current is from the positive electrode of the lamp through 

 the galvanometer to the insulated metal plate, or wire. When 

 the same galvanometer is connected between the negative pole 

 of the lamp and the middle plate, unless it is very sensitive, it 

 indicates no current. This effect was very carefully examined 



* Communicated by the Physical Society : read March 27th, 1896. 



