712 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



0.00040 and 0.00031. The actual temperature coefficients at room tem- 

 perature are always less than these mean values, and in the case of the 



Figure 5. 



last-mentioned form the coefficient between 10° C and 40° C. is not 

 greater than 0.00013. 



If the slender part of such a casting as No. 1 be wound as uniformly 

 as possible with insulated wire, and if steady currents of different 



