[ 49 ] 



IV. Energy Distribution in Spectra. — I. By R. T. Beatty, 

 M.A., L).Sc, Lecturer in Physics, The Queen's University 

 of Belfast*. 



[Plate II.] 



[The expenses of this investigation have been partly defrayed by 

 grants from the Government Grant Committee of the Royal Society 

 and from the Institut international de Physique Solvay.J 



IN this paper the author describes an investigation of the 

 energy emitted by the lines o£ the spectrum of hydrogen 

 in the visible region. The light from a Geissler tube was 

 analysed by a monochromator, and its intensity was measured 

 by a photo-electric cell which was calibrated by means of a 

 carbon filament glow-lamp. 



The Production of the Light. 



A Gramme machine was fitted with two slip-rings con- 

 nected to two opposite points of the armature-winding, so 

 that when the machine was excited by a direct-current 

 dynamo supplying current at 60 volts it acted as a rotary 

 converter, giving alternating current with a frequency of 

 about 40 alternations per second. The terminals A A (fig. 1) 



Fig. 1 



Cw 



A A 



MVWW -i- 



■WAAAAA; (/} 



i-V»WWW 



to earth 

 j< — »to earth 



to earth 



were connected to this source of alternating supply. The 

 current passed through the primary P of an induction-coil 

 and a variable rheostat, and a fine adjustment could be made 

 by sliding a copper bar C along two parallel resistance wires. 

 In the secondary circuit the induced high potential current 

 passed through the secondary S o£ the induction-coil, the 

 Geissler tube, and the liquid resistance L consisting of a 

 mixture of copper sulphate and glycerine. 



* Communicated by the Author. A preliminary account of this work 

 was given in a paper read before Section A of the British Association at 

 its Newcastle Meeting, September 1916. 



Phil. Mag. S. 6. Vol. 33. No. 193. Jan. 1917. E 



