268 Mr. G. A. Hemsalech: Excitation of Spectra of Carbon, 



the red fringe originated below. But, in either case, the 

 result is of the utmost importance with regard to the cause 

 of the fringe emission. The strong continuous -spectrum, 

 due to the ed^e of the plate, is slightly widened owing to 

 the bending of the latter under the stress of the magnetic 

 force. Below the plate the spectrum shows the usual de- 

 velopment, except that the bands and lines of the fringe 

 emission are appreciably shortened by the strong magnetic 

 field. The lines emitted by the luminous vapour pass, as 

 usual, much farther down and fade away only gradually. 

 Now, on this side of the plate all these lines are fairly strong 

 as compared with those of the fringe spectrum. But in the 

 region above the graphite plate we find, on the contrary, 

 that the fringe spectrum is relatively more important than 

 that due to the vapours. Thus, to cite only one example, 

 the two aluminium lines 3944 and 3962, which, below the 

 plate, are much brio-liter than neighbouring titanium lines, 

 are, above the plate, relatively fainter than these same lines 

 of the fringe spectrum, although they pass to a greater 

 height. It is evident, therefore, that the two emissions — 

 namely, that due to thermo-electrical excitation and that 

 caused by thenno-chemical excitation, are differently af- 

 fected, and we are led to assume, either that only a small 

 amount of luminous vapour is present above the plate, or 

 that the temperature here is considerably less than what it 

 is below the plate. But, whichever explanation holds, this 

 record constitutes ah indisputable proof for the reality of 

 the existence of two independent emissions and, furthermore, 

 from the total experimental evidence furnished in the course 

 of this paragraph, it is manifest that the emission of the red 

 fringe spectrum is primarily controlled by the thermelectronic 

 current and not merely by the temperature of the plate. 



§ 10. Possible cause of excitation of red fringe spectrum. 



The spectroscopic evidence furnished by this research goes 

 to show that the thermelectronic current on passing through 

 the ionized vapours (probably carbides) in the vicinity of the 

 hot plate of graphite, is responsible only for the emission of 

 the spectra of carbon, titanium, vanadium, and some bands 

 of unknown origin. There is indeed no indication that the 

 lines of iron, manganese, potassium, sodium, etc., are in 

 the least influenced by it under these particular experi- 

 mental conditions, it will, however, be shown in a subse- 

 quent communication that when the intensity of the acting 

 electric field is increased (in the present case the electric 



