Intelligence and Miscellaneous Articles. 445 



Summing up our conclusions, we see that, contrary to the 

 opinion of Prof. Forbes, the theory of probabilities does not 

 affirm that a " perfectly uniform and symmetrical disposition 

 of the stars over the sky would (if possible) be that which 

 could alone afford no evidence of causation or any interfer- 

 ence with the laws of 6 random/ " On the contrary, I have 

 endeavoured to show that this theory gives a sufficient account 

 of the possible irregularities of distribution such as those ob- 

 served by Prof. Forbes in his experiments, or those presented 

 by the stars in the sky. The ingenious argumentation of 

 Mitchell respecting the improbability of the observed groups 

 of stars being merely accidental is by no means in contradic- 

 tion with the true principles of probability, and the exact 

 meaning of the "law of great numbers." 



St. Petersburg, October 2, 1887. 



LVIL Intelligence and Miscellaneous Articles. 



MAGNETIC CIRCULAR POLARIZATION IN COBALT AND NICKEL. 

 BY H. E. J. G. DTT BOIS. 



TF we consider an infinitely extended plate of any thickness in a 

 -*- uniform magnetic field normal to its plane sides ; the material 

 being supposed homogeneous, isotropic, and devoid of retentiveness, 

 the induced magnetization is given by the equation 



3 = 



4tt + 1/k 



where § a is the original field, k the susceptibility. From Rowland's 

 data for " Burden's best " iron, cast cobalt, and cast nickel the 

 relation between k (an essentially variable quantity in the case of 

 these metals), and is known, and curves are accordingly plotted 

 corresponding to the above equation. Their shape is represented 



with great approximation in the annexed diagram. The ordinate 

 of the singular point is the maximum TO given by Kowland, 

 its abscissa is 47r ?n ; the absolute values stand as follows : — 



" Burden's best " n , , r . «'.,.-,, 



iron cobalt. Cast nickel. 



Ordinate J 390 880 494 C.G-.S. 



Abscissa 17440 11060 6200 C.G.S. 



