518 Prof. Pliicker on the Nature of the 



Suppose l-f-p + p 2 =0, then 

 x % + y- + z 2 —yz—zx—xy=(x + py + p' 2 z)(x+p 2 y + pz); 

 and in fact 



3 \/u{z' -f- py' + pV) = - \/3^(l + 2p) {x + py + p 2 ~) 

 3 \/« (x' + phj + pz) = \/37?(l + 2p) (a: + p*y + p?) . 

 The preceding investigations have been in my possession for 

 about eighteen months. 



2 Stone Buildings, 

 April 18, 1855. 



LXXII. Contributions to our Knowledge of the Nature of the so- 

 called Coercive Force. By Professor Plucker*. 



1. TN a former memoir I proved that the magnetism excited 

 J- by paramagnetic or diamagnetic induction in various 

 substances is not proportional to the inducing force, but in each 

 particular substance, according to a peculiar law, approaches a 

 maximum which is the point of saturation of the substance. I 

 have shown empirically, that for each of the substances examined 

 by me, the induced magnetism, after assuming the unit of indu- 

 cing force, could be determined by means of two other constants 

 which are independent of each other. One of these constants I 

 have named the cojistant of induction, and the other the constant 

 of resistance^ . If it should be found that the constant of 

 resistance in any substance is zero, then for this substance the 

 induced magnetism would be proportional to the inducing force, 

 and the receptivity of the substance for magnetism would be 

 shown by the constant of induction alone. The induced mag- 

 netism of the substances examined by me (nickel, cobalt, iron, 

 oxide of iron, oxide of nickel, bismuth, phosphorus, oxygen, 

 hydrated oxide of cobalt) always falls short, in different degrees, 

 of the proportionality mentioned ; and the more so, the greater 

 is the constant of resistance. The few observations made at the 

 time rendered it to me probable that for those substances which, 

 after the inducing force to which they were exposed had ceased 

 to act upon them, still retained a considerable portion of their 

 magnetism, the constant of resistance was comparatively small; 

 so that the magnetism of such substances, when the inducing 

 force is augmented, increases more quickly, and more slowly 

 approaches the point of saturation, As far a3 regards hard steel 

 in comparison with iron, I could not doubt the correctness of 



* Extract from a paper in Poggendorff's Annalen, vol. xciv. p. 28. 

 t Some other term might have been chosen with advantage. — Ed. Phil. 

 Mao. 



