350 Dr. C. Bums on the Relation betiveen the Thermoelectric 



the rods with their respective parts of the bridge by means of 

 mercury. 



The efficient length was determined by deducting from 

 the total leno-fch that of the amalgamated ends. For the mea- 

 surement of the diameter, use was made of the microscope ; 

 a determination of this dimension from known length, weight, 

 and specific gravity was impracticable, inasmuch as the use of 

 the pyenometor, which alone would have given sufficiently 

 accurate results, would have compelled me to break the rods. 



VI. Experimental Results. 



A. Thermoelectric Hardness of Rods suddenly immersed in 

 Cold Water while in different states of Red Heat. 



The following (older) results were obtained directly by 

 Ohm's method. E T was put = const, r — a condition nearly 

 fulfilled by couples of soft and hard steel between 0° and 80°, 

 in which case also the T. E. H. and the constant of propor- 

 tionality are identical. The rods were hardened in the appa- 

 ratus described in § II. ; diameter =0*678 millim. ; the num- 

 bers preceded by the point (•) were afterwards checked by 

 the method of compensation. T. E. H. is expressed in Weber- 

 Siemens units. 



The third column of the following Table contains the num- 

 ber of large Bunsen cells employed in the heating of the wire, 

 the fourth the observed degree of redness at the time of sudden 

 cooling. 



Table I. 



No. 



T. E. H. 



Bunsen 



Elements. 



Remarks. 



1 



0-0000004 





Soft, cooled slowly. 



.2 



0000003 



4 



Below redness. 



B 



0-000012 



5 



1 



0-000000 



5 





{1 



o-oooooo 



6 





0000000 



6 



► Dark red. 



(.! 



0-000052 



7 





0000049 



7 





' 9 



0000054 



7 



) 



r. io 



0000056 



8 



\ 



i n 



0-000057 



8 



\ 



1 12 



0-000063 



8 



y Brick-red. 



(A3 



-1 14 



0000064 



9 



0-000065 



9 



| 



15 



0000064 



9 



J 



