644 MR JAMES RUSSELL ON 



one direction takes place when a constant transverse magnetising force is maintained." 

 They add: "The experiments described have nothing whatever to do with the initial 

 part of the force induction curve for iron to which so large an amount of attention has 

 been devoted, and which is of so little practical importance." 



But it is sufficiently obvious that any conclusions based upon experiments in which 

 strong magnetising forces are used cannot be legitimately used as against the Weber 

 hypothesis, which explains induction at high values, on the assumption that the 

 rotating molecular magnets have already placed themselves well in line with the 

 resultant of the strong forces at right angles to each other. The results of the 

 experiments on superposed inductions given in the preceding sections are quite in 

 harmony with and satisfactorily explained by the usually accepted theory that induction 

 consists iu the definite orientation of molecular magnets. Such experiments, however, 

 to have any bearing on the subject, must be conducted during the process of this 

 molecular turning, and not when the turning is nearly completed. This subject is again 

 considered when dealing with the magnetic seolotropy of demagnetised iron (see § 30), 

 and it is also shown (see § 36) that a sufficiently well marked increase of permeability 

 actually exists when the iron has been left with residual magnetisation at right angles 

 to that of the subsequently applied magnetising forces. 



II. Superposed Magnetic Inductions in Iron. — (b) Cyclic Conditions. 



§ 22. In the preceding sections, the two components of the final resultant induction 

 were considered, when upon an induction due to a magnetising force first acting, 

 repeated reversals of a force at right angles were superposed. These components, 

 however, were co-ordinated, the one with the other, only at the extreme positions of the 

 superposed reversals. In the experiments now to be described, each superposed 

 reversal is a cyclic process performed in a series of steps. The component of the 

 induction due to the force first acting (H c or H, as the case may be) can thus be traced 

 at each step of the superposed cycle or cycles. 



The longitudinal induction component being measured, Table XL gives the measure- 

 ments obtained, when upon a longitudinal induction of B ? = 7300 sustained a field of 

 H; = 20'4 C.G.S. units, the superposed circular force is first increased by increments 

 from zero to a maximum of H c =12 C.G.S. units, and then carries the B c . component 

 round complete cycles between positive and negative extremes of approximately B t — 

 10,000. The first and fifth columns give the values of the magnetising force H c , the 

 second and sixth columns the corresponding readings of the galvanometer in scale 

 divisions measuring Bj as above mentioned. In the fourth and eighth columns, the 

 cyclic changes of B^ are given in C.G.S. units. In the last four columns, a sufficient 

 number of intermediate points are taken to determine more fully the shape of the curve 

 after the changes have become cyclic. All the B.G. columns give the average results 



