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PROCEEDINGS OF THE AMERICAN ACADEMY. 



fusion of the wire by the flame. An examination of the remaining 

 portions under the microscope showed that the metal had been melted 

 down into clean, well-rounded beads, and had not been consumed by 

 oxidation or any other chemical reaction. 



Smithells's contention that the temperature of flames cannot be 

 obtained directly from the indications of a thermo-element because of 

 the loss of heat by conduction and by dispersion from the surface of the 

 latter, so that the portions submerged in the flame never arrive at the 

 temperature of the surrounding gases, is well founded. Lewes and 

 likewise Waggener recognized this fact, and in their measurements 

 made use of wires of different sizes. 



The apparatus which I employed for the determination of the temper- 

 ature of the acetylene flame has already been described (see Figure 6). 

 The method was similar to that used in the calibration of the thermo- 

 elements. The electromotive force of the elements, as these were 

 gradually brought into the flame, was measured by means of the 

 potentiometer previously employed in the calibration of the thermo- 

 elements and subsequently in the determination of the temperature 

 of the carbon rods. It consisted of a sensitive galvanometer of the 

 d'Arsonval type and au accurately adjusted resistance box containing 

 coils ranging from 50,000 ohms to 1 ohm. A large Clark cell of the 

 old Feussner type was mounted in series with the resistance box. The 



thermo-element, the galvan- 

 ometer, and a subsidiary re- 

 sistance of 10,000 ohms were 

 looped around a portion of 

 the resistance box, the ratios 

 being varied until complete 

 balance was secured. The 

 electrical connections are 

 shown in Figure 10. The 

 type of standard cell selected 

 for this work is subject to 

 considerable errors from diffu- 

 sion lag. It has, however, the 

 advantage of being capable 

 of furnishing a much larger 

 amount of current than the small types of cell, in which diffusion lag 

 is avoided, without appreciable loss of electromotive force. Two of 

 these cells were placed side by side in a thick-walled inner room which 



THERMO JUNCTION 



10,000 

 OHMS. 



110,000 OHM8. 



CELL 



Figure 10. 



