78 



SCIENCE. 



[N. S. Vol. IV. No. 81. 



heretofore neglected by my predecessors. After 

 the reading of the paper referred to before the 

 Congress of Astronomy and Astro-Physics, 

 Chicago, 1893 (No. 118, p. 746): ''in the dis- 

 cussion Prof. H. A. Eowland expressed his 

 belief in a magnetic condition of the sun, and 

 remarked that he considered its eflfect upon ter- 

 restrial magnetism a subject well worthy of 

 careful investigation." 



Prof. Franklin should properly have at- 

 tempted to show some defect in the magnetic 

 observations themselves or in my handling of 

 them ; also he should show that some other in- 

 terpretation of them can be given than the one 

 I have offered. A very little mathematics, all 

 well known, has been introduced at certain 

 passages, but nothing of the kind was employed 

 when it could have influenced the nature of 

 the residuals. On the other hand, having ob- 

 tained the residuals, it was proper to seek the 

 corresponding mathematical solution. 



4. Our reviewer now proceeds to remark on 

 the ether fields : " The idea that vortex motion 

 of the ether constitutes magnetic field is, as yet, 

 mere speculative theory intensely interesting, 

 coming from §uch masters as Lord Kelvin and 

 Clerk Maxwell ; supremely foolish as coming 

 from one who, for example, uses the word 

 ' spiral ' in speaking of it, or from one who 

 thinks a magnetic field to be a stream of 

 energy." While I admit my intellectual debt 

 to Thompson and Maxwell in my study of these 

 subjects, I must also confess that it seems to me 

 that Heaviside and Hertz are the real masters 

 of modern electricity and magnetism, and that 

 their duplex-law of circuitation is the funda- 

 mental principle. 



For example, Heaviside summarizes his views 

 (Electromagnetic Theory, p. 35) as follows : 

 * ' The electric current is the curl of the mag- 

 netic force. The magnetic curi-ent is the nega- 

 tive curl of the electric force." In a word, any 

 change in the ether stress is accompanied by 

 an electric and a magnetic current ; p. 79, "in 

 the case of a simple progressive plane wave 

 disturbance, in which a distribution of electric 

 force and magnetic induction mutually perpen- 

 dicular in the plane of the wave is propagated 

 unchanged through a medium at constant speed, 

 it is a self-evident result that the energy of the 



disturbance travels with it ; " page 80, ' ' the only 

 dynamical analogue that is satisfactory in this 

 respect is that furnished by Sir W. Thompson's 

 rotational ether, when interpreted in a certain 

 manner ;" p. 110, "this is the pressure exerted 

 by solar radiation ; ' ' and much more to the 

 same effect. The essence of this view is that 

 whatever may be predicated of the electric sys- 

 tem can be transformed to the magnetic system 

 by a simple interchange of words in the nota- 

 tion (Hertz, Waves, p. 225); and in harmony 

 with it an ordinary steady magnetic field sur- 

 rounding a uniformly magnetized sphere is in 

 reality a dynamic system. Certainly when the 

 magnetization varies for any cause the effect is 

 a propagation of energy throughout the entire 

 system till equilibrium is regained. It is true 

 that the mechanical analogue is lacking in the 

 relations of electricity and magnetism. Flem- 

 ing (Transformer, p. 11) : "The question which 

 yet remains unanswered is, what is that action 

 or operation along certain lines in this medium 

 which causes a line of force to exist? The 

 future of electric and magnetic investigation 

 will perhaps conduct us step by step to the so- 

 lution of this supremely important problem." 



Prof. Franklin continues his comment as fol- 

 lows, p. 809 : ' ' Now the magnetic field in light 

 and heat waves is at right angles to the ray and 

 is reversed in direction millions and millions of 

 times per second ! It is to be noticed that 

 Prof. Bigelow considers the coronal field to be 

 a stream of energy. If such is the case it is of 

 course not a magnetic field, but he surely so 

 considers it and he has also determined its 

 C.C S." In reply to the first case, the radiant 

 flux of energy from the sun is W^V. EH, vec- 

 tor product of electric force and magnetic in- 

 duction. The rapid reversal, incident upon the 

 passage of a magnetic wave with lag of a quad- 

 rant on the electric, makes the field equivalent 

 to a steady field when falling upon a mass whose 

 moment of inertia, like a common magnet, gives 

 a much slower time of swing, and will always 

 be so to any magnets not of atomic and molec- 

 ular dimensions. The electro-magnetic field at 

 the earth has, therefore, the effect of a uniform 

 field surrounding a conductor, and its lines are 

 disturbed accordingly. In answer to the sec- 

 ond case, Heaviside says. Electrical Papers I., 



