420 Mr. W. Brown on the Effects of Percussion and 



3. Course of values of the coefficient of field -magnets and 

 armature of a dynamo. 



The numbers stated in the paper may possibly be mislead- 

 ing, as it is not sufficiently explained that the number deter- 



mined from the motion of the machine, I ^ — 1, is not of the 



> (gs> h 



same nature as the two results of determinations made at rest, 

 which precede. 



£- J is necessarily infinite 



when the current is evanescent, if there is any retention of 

 magnetism in the machine, and diminishes continually as the 

 current increases. The following corresponding values of 

 this coefficient and current are given by the data referred to 

 in the paper. 



Coefficient. Current in amperes. 



10 7 x 7-054 3-8 



x 6*250 5-5 



x 5-600 7-6 



x 4-732 10-5 



XLIX. The Effects of Percussion and Annealing on the 

 Magnetic Moments of Steel Magnets. By William Bkown, 

 Thomson Experimental Scholar, Physical Laboratory, Uni- 

 of Glasgow*, 



Pakt II. 



IN Part I. of this paper, which appeared in the March 

 number, certain preliminary results were given, showing 

 the effects of percussion on the magnetic moments of steel 

 magnets. In the present communication these effects are 

 considered in greater detail, with tables giving the results of 

 an extended series of experiments, and the question of an- 

 nealing is treated with respect to exact measurements of the 

 annealing temperature. 



The steel experimented on in this case was furnished to Sir 

 William Thomson for experimental purposes by two different 

 steel-makers. 



The following Table gives approximately the relative per- 

 centage proportions of all the substances found in the steel, 

 the quantities in specimen I. being taken as unity. They are 

 tajien, not from analyses of the particular pieces experimented 

 on, but from a general analysis of the sample in each case. 



* Communicated by Sir William Thomson. 



