Mr. Faraday on Sig. Negro's Magneto-electric Experiments. 'iS 



meet with no sensible resistance from the ethereal medium. 

 Supposing the aether to be constituted like air, and the matter 

 of the earth and planets to consist of very minute spherical 

 atoms, (suppositions, which I have already advanced to ex- 

 plain some phasnomena of light*,) it will follow that no part of 

 the resistance, caused by the condensation of the medium, 

 varies as the simple power of the velocity: also the term 



rf'U) 

 "^—^ — must be quite insensible. With respect to that 



part of the motion of the asther which is unaccompanied by 

 change of density, we may say that the velocity of any particle 

 in the same position relatively to the centre of the planet, and 

 to the direction of its motion, has always the same ratio to 

 the velocity of the planet. The consequence of this would 

 be, that the law of the force tending to the sun would not be 

 changed, but its quantity would be diminished. This effect 

 would be accounted for by taking the mass of the planet of 

 less magnitude than it really is, and therefore probably can- 

 not be easily detected by observations. Hence if any resist- 

 ance be sensible by any change of the orbits or the periodic 

 times, it will depend on the square of the velocity. Also it 

 must be much less sensible in deiise bodies like the planets, in 

 which the particles that precede diminish the resistance on 

 those that follow, than in such a rare substance as Encke's 

 comet. This singular body has in fact, in the opinion of 

 competent judges, determined the existence of a medium, or 

 something equivalent, resisting according to the square of the 

 velocity. 



Papworth St. Everard, April 17, 18.32. 



XI. New Experiments relative to the Action of Mag7ietism on 

 Electro-dynamic Spirals, and a Description of a new Electro- 

 motive Batteiy. Bij Signor Salvatore Dal Negro; with 

 Notes by Michael Faraday, Esq., F.R.S., M^R.I. Corr. 

 MemI). Roy. Acad. Scien. of Paris, t^x.f 



[Addressed to Dr. Ambrogio Fusinieri, Director oftheAnnali 

 dclle Scienzc, ($-c. c^-f.] 

 Sir, 

 /^N repeating the experiments relative to the action of ter- 

 ^ restrial magnetism on electro-dynamic spirals, an action 

 which was first observed J by the two illustrious Italian jjhilo- 



• Sec Phil. Mag. and Annals for March last, p. IBl. 

 1 ('oniinuiiitHtcd hy Mr. Faraday. 



; ['I'his is an error. A Ion;; section is devoted to terrestrial niagncto- 

 elfctrif induction in my original researches. (I 10 to 19'-') of the dale of 



