Researches in Electricity and Magnetism. 457 
phzenomena in which light is in any way evolved. It is univer- 
sally admitted that nothing passes from the permanent mag- 
net to the lifter when temporary magnetism is induced on the 
latter. It is also admitted that nothing passes from the lifter 
to its surrounding coil when voltae electricity is induced on 
the latter. The polarity of the electricity essentially belong- 
ing to the soft iron is rapidly changed by the change of poles 
in the soft iron horseshoe lifter. ‘The electricity thus thrown 
into a rapid vibratory state must derange the stable equili- 
brium of the electricity belonging to the coil of copper wire. 
Hence if this wire or the circuit be suddenly broken, which is 
the case when one of the points leaves the mercury, the rapid 
motion of the electricity at the point of separation must com- 
municate a corresponding rapid vibration to the electric fluid 
contained in the surrounding air, and consequently to the elec- 
tric fluid contained in the humours of the eye, retina, optic 
nerve, and brain, which will be followed by the sensation of 
light. 
The ‘appearance and indefinite continuance of the mag- 
neto-electric light, without deriving supply from any foreign 
source, thus affords a powerful argument in favour of the 
undulatory theory of light, whilst it appears to me an unan- 
swerable objection to the Newtonian doctrine. As long as 
the lifter is made to revolve, light of the same degree of 
brilliancy continues toemanate. We can conceive this motion 
continued for ever; so that the light, according to the New- 
tonian theory, lurking in a small copper wire and actually 
given out, would ultimately surpass all the light which has 
been given out by the sun since the creation of the world. For 
an infinite number of sparks, however minute, will constitute 
an infinite light; whereas the whole light given out by the 
sun since the creation is only a very limited quantity. Since 
gold-leaf placed in the circuit is deflagrated, and a fine platina 
wire heated red hot, these effects are obviously produced by 
the rapid vibration of the electricity or ether essentially be- 
longing to them. The metals then are obviously heated by 
their own heat, an unanswerable argument against the chemical 
theory of caloric. 
2. In order to account for the production of the physical and 
physiological effects by wires of different lengths, we must take 
into view the striking difference between good and imperfect 
conductors of voltaic electricity. The metals not only con- 
duct much deter than liquids, but also convey the vibratory 
wave much quicker. In the case of a short conductor the 
whole electricity belonging to it has polarity induced on it in 
an indefinitely short period ; and also returns to its natural 
Third Series. Vol. 8. No. 49. June 1836. 22 
