338 Intelligence and Miscellaneous Articles. 



from which 



— A = 1 I?»— I 



This is Frohlich's formula. 



Now this formula holds very well with feebly magnetic bodies ; 

 we may from this conclude that in this case the pressure p is 

 correctly valued. On the other hand, it does not agree with 

 strongly magnetic bodies, for which the value of the pressure p is 

 given by the formula of Yan der Waals. From the known pro- 

 perties of this equation, the pressure corresponding to two values 

 of I, corresponding to the same susceptibility K, is the same. 



4. For a fluid, in proportion as the temperature T decreases the 

 density of the saturated vapour decreases cotemporaneously with 

 the tension; at the temperature at which the density becomes 

 null, the tension is null also. Thus the second part of the equation 

 of Yan der "Waals vanishes, and we deduce from it the value of 

 the density of the liquid under the pressure null of its saturated 

 vapour. 



Applying the same method to the example mentioned above, the 

 parabola cuts the axis of abscissae at the point 47rK=516 ; the 

 corresponding value of I given by the equation of Yan der Waals 

 is 1=1260. The direct measurement on the parabola gives 1256. 

 This is an almost absolute coincidence. 



5. From this point the equation of Yan der Waals can no 

 longer represent the phenomenon, for the fluid can no longer 

 exist in the liquid state ; a change of state takes place, and the 

 representative curve changes suddenly. This is also the case 

 with magnetism ; it is from this point that the curve is no longer 

 parabolic. There is a change of state corresponding to the passage 

 from the liquid to the solid state. 



In fine, the phenomena of the magnetization of iron are ana- 

 logous to those presented by a saturated fluid, and might be 

 calculated by the same formulas ; I propose to try if we can find 

 experimentally a reduced equation independent of the magnetized 

 body. 



Feebly magnetized bodies are subject to laws analogous to those 

 of liquids at a distance from their point of saturation. — Communi- 

 cated by the Author, from the Oomptes rendus, Jan. 8, 1894. 



ON THE EXPERIMENTAL INVESTIGATION OF THE ROTATIONAL 

 COEFFICIENTS OF THERMAL CONDUCTIVITY. BY CH. SARET. 



In the very amiable and indulgent notice which the Archives 

 de Geneve has published of my Elemens de Qrystallographie 

 physique, M. Curie has proposed a method by which the existence 



