350 Mr. R. H. M. Bosanquet on Electromagnets. 



(see Phil. Mag. [5] xv. pp. 285 & 286) ; whence 



log e n=(l— 7) logC+ const., 

 or 



n— const, x C 1- ^ 

 or 



n x = const. C ; 



and we have deduced the form of equation before assumed, 

 from the principles of the dynamic action of the machine. 



In practice these considerations and laws are much modified, 

 chiefly by the enormous magnetic retentiveness of the field- 

 magnets. 



I shall have to deal with this subject in discussing the 

 performance of my Gramme machine. 



Errata in recent papers. 



Phil. Mag. vol. xxii. p. 307, for the heading of the Table substitute 



Bars with P.P. without Magnetizing-Force term. 



pcalc. =-00252+ I, 1=1 centim., log- =2-35933, 

 P> P 



^=•415 (18,366-33) cos 8, log/= '16500, 



8=/6, 33=* 



'-G>0 



p sin 



Phil. Mag. vol. xxii. p. 308, for the heading of the Table substitute 

 Bars with P.P. with Magnetizing-Force term. 



p calc. = -00252+ -, 7= 1 centim., log n = 1-08160, 

 P 



<w33 



/x=-69 (— +16,421-23) cosS, log- =2-57346, 

 \ P ' p 



K 60°— CO0 



p sin 



b=f0, 23 = - Wj=^, log/ = -16878. 



Phil. Mag. vol. xxii. p, 536, line 3, for -526 centim. in diameter read -526 

 inch in diameter. (This clerical error appears in the description of the 

 instrument, but does not affect the calculations.) 



