Difference in Phase of two Harmonic Currents. 295 



both by transverse and longitudinal magnetization in the 

 thermal conductivity, the electrical conductivity, and the ther- 

 moelectrical power of the metal, we must be driven to the 

 conclusion that magnetism in all metals exerts two distinct 

 influences ; one by rotation of the molecules about their axes, 

 the other in some way which is not yet understood. In such 

 metals as iron, and to a less extent in cobalt and nickel, the 

 first of these influences probably plays a not unimportant 

 part ; but in such metals as bismuth, antimony, and tellurium, 

 the second must entirely predominate. 



XXXYI1I. On a Method of Determining the Difference between 

 the Phase of two Harmonic Currents of Electricity having 

 the same Period. By Thomas H. Blakesley, M.A.* 



IT has been brought to my notice by both English and 

 Foreign journals connected with science that a method of 

 determining the difference in phase of two Harmonic Currents 

 of Electricity having the same period, which I invented and 

 published some years ago, forms an important part of the 

 subject matter of a paper communicated to the Royal Academy 

 of Sciences of Turin, second series, vol. xxxviii., by Signor 

 Galileo Ferraris, in which that philosopher lays claim to the 

 invention above mentioned, producing it as original, with no 

 sign of acknowledgment that the method has before been 

 made public. 



The method consists in employing the two coils of an elec- 

 tric dynamometer in a peculiar way. When an harmonic 

 current is sent through the coils of such a dynamometer in 



series, its reading will measure the quantity -^-, where I is the 



u 



maximum value of such a current. In this way we may 



J 2 J 2 



successively determine ■— and ~, where the subscripts refer 



to two currents having the same period. 



But if we place one of the coils in one circuit and the other 

 in the second circuit, the reading of the instrument will 



measure -^ cos 0, where is the angle representing the 



phase-difference of the two currents, to which the name 

 " de'calage , ' > has, I have no doubt with great propriety, been 

 accorded by M. Hospitalier. 



It is clear that from the three readings we can deduce the 



* Communicated by the Physical Society : read March 10, 1888. 

 X2 



