of the Flame and Furnace Spectra of Iron. 221 



at 4376 and class II. triplet at 4384. At the low tempe- 

 rature of 1600° C. group 7 stands out conspicuously, the 

 line X4376 being much more intense than its neighbour 

 \4384; at 2100° C. 4384 is brighter than 4376, and the 

 relative intensities of the triplet lines with respect to those 

 of group 7 increase considerably at still higher furnace and 

 flame temperatures. 



The furnace spectra, as has already been explained, extend 

 a little farther towards the red than the flame spectra. But 

 it should also be remembered that I was unable for the 

 reasons given elsewhere* to work the high-temperature 

 flames to their full thermal advantage. Thus in the 

 oxy-hydrogen flame spectrum of iron published by Dr. de 

 Watteville and myselff, and in which we included for want 

 of space only the lines down to intensity 2, the lines 5328 

 and 5371 are marked 5 and 2 respectively, so that most 

 undoubtedly the other lines which are weaker, namely 5397, 

 5405, and 5430, should be expected to exist among those of 

 intensities 1 to 000. As further evidence to the effect that 

 my high temperature flames in the present experiments were 

 not quite developed to their utmost perfection may be men- 

 tioned the fact, that no traces of class III. lines were observed 

 with the oxy-acetylene flame. Their presence in this flame 

 was, however, particularly noted by l)r. de Watteville and 

 myself. Since the appearance of lines of this character in 

 the oxy-acetylene flame is of the utmost importance for the 

 true appreciation of furnace spectra, I have added them to 

 the present list from the data previously published J. None 

 of these lines are observed in the furnace spectrum below 

 2500° C, nor in any flame below the temperature of 2700° CL 

 But they are easily emitted by chemical excitation in the 

 air-coal gas cone, and some of them attain considerable pro- 

 minence under the influence of electric actions, as for 

 example the group at 4957. The fact that these lines 

 appear only as feeble traces at the high temperature of the 

 oxy-acetylene flame is another proof that the mode of 

 excitation which is prevalent in the furnace up to 2400° C. 

 and in the several flames examined is absolutely different 

 from that which underlies their emission in the air-coal gas 

 cone, arc, or spark. On the other hand, as is clearly demon- 

 strated by my results, the mode of excitation in the furnace 



* Hemsalech, I. c. I. p. 7. 



t Hemsalech and de Watteville, Comptes Rendus de V Academie des 

 Sciences, vol. cxlvi. p. 962 (1908). 



X Hemsalech and de Watteville, Comptes Rendus de V Academie des 

 Sciences, vol. cl. p. 330 (1910). 



