96 PROCEEDINGS OF THE AMERICAN ACADEMY. 



may be found in the outer non-luminous layer of the flame, but that it 



is unlikely that the difference amounts to more than twenty degrees. 



The point of intersection referred to above lies neaily one hundred 



degrees above tlie highest temperature recorded by even the smallest 



of the thermo-elements, and it is safe to infer that nearly all previous 



attempts at the measurement of flame temperatures must, for lack of 



correction of the erroi', due to loss of heat through the wire, be regarded 



as much too low. The junction IV. is, so far as I am aware, the smallest 



in cross-section that has been used in such work. With larger wires, 



tlie correction for loss of heat would be even greater, except in cases 



where, as in the observations made by Smithells, and by Waggener, the 



precaution was taken to immerse an extended portion of the wires within 



the flame. 



Temperature of Other Flames. 



For the purpose of comparison, I measured in a manner analogous to 

 that just described, the temperature of the luminous flame of ordinary 

 illuminating gas and the flame of a candle. The gas flame employed 

 for this purpose was obtained from a lava tip rated at one cubic foot and 

 giving a flat flame of the upual form. The image of this flame, when 



viewed upon the ground-glass screen of my 

 camera, was found to be comparatively ill- 

 defined and unsteady ; but although the outlines 

 of the luminous sheath were much less clearly 

 marked than in the case of the acetylene flame, 

 they were discernible. Owing to the continual 

 motion of the flame, due to the small velocity 

 of the gas i-suing from the jet, no attempts 

 were made to plot curves of temperatures outside 



the flame. All readings were made with the 

 Figure 13. . . , * ., , . 



junction as nearly as possible in contact with 



the outer surface of the luminous sheath, at a point in the brightest por- 

 tion of the flame. This position is approximately indicated by the letter 

 X in Figure 13. The four junctions already described were mounted, 

 one after another, in such a position that the flame could be moved up 

 until they came into contact with the sheath at the point indicated. The 

 temperatures of the junctions when in that position are given in tlie 

 following table 



