92 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



The wires selected for the four junctions to be used in the experiment 

 upon the acetylene flame were measured under a microscope with 

 micrometer stage. Their diameters were as follows : — 



Junction I. 

 " II. 

 " III. 



" IV. 



Diameter 0.0199G cm. 

 " 0.01598 cm. 

 " 0.01089 cm. 

 " 0.00821 cm. 



Readings were first made with junction I. (diameter 0.01996 cm.). 

 The flame was set at a distance of 6 mm. from the face of the junction, 

 and the potentiometer was balanced. The flame was then moved step- 

 wise nearer and nearer, and the potentiometer rebalanced at each step 

 until the face of the junction coincided with the edge of the luminous 

 mantle at a point just above the apex of the inner nonduminous zone. 



The rise of temperature indicated by the potentiometer readings is 

 shown in curve a (Fig. 11), the data for which as well as for the other 

 curves in that figure are contained in Table II. 



TABLE II. 

 Temperatures indicated by thermo-junctions I., II., III., and IV. at various 



DISTANCES FROM THE MEDIAN PLANE OF THE ACETYLENE FLAME. 



