THE 
LONDON, EDINBURGH anno DUBLIN 
PHILOSOPHICAL MAGAZINE 
AND 
JOURNAL OF SCIENCE. 
[FOURTH SERIES.} 
MAY 1861. 
XLIX. On the Determination of the Direction of the Vibrations 
of Polarized Light by means of Diffraction. By L. Lorenz*. 
1 ae question whether the vibrations of polarized light are 
perpendicular to the plane of polarization, or in that plane, 
notwithstanding its great theoretical importance, is still unde- 
cided. On comparing the different arguments that may be ad- 
vanced in favour of either hypothesis, only two will be found 
that have an essential bearing on the subject,—the experiments, 
namely, of Jamin on the reflexion of light by transparent media, 
and the polarization of light caused by diffraction. 
The experiments of Jamin have hitherto been explained on 
the supposition that the vibrations of polarized light are perpen- 
dicular to the plane of polarization. ‘This, however, is not deci- 
sive of the question, since it has hitherto been assumed that 
there is an instantaneous change of refractive power at the 
boundary of two transparent media; whereas I shall prove, in a 
subsequent essayt ‘On the Reflexion of Light,” that Jamin’s 
experiments can only be brought into complete accordance with 
Fresnel’s formule for the reflexion and refraction of light, on the 
hypothesis that these formule hold good for infinitely small 
changes of the refractive index, that is to say, on the hypothesis 
that there is a gradual passage from one medium to the other. 
It may be asked whether Fresnel’s formule really hold good 
for an infinitely small change of refractive power, and whether 
these formule may be deduced on either hypothesis as to the 
direction of the vibrations of polarized light; two questions 
which I shall answer in a third essay. 
alee by F. Guthrie, from Poggendorff’s Anzalen, vol. exi. p. 315, 
'-> See Poggendorff’s Annalen, vol. cxi. p. 460: a translation of -this 
paper will be given in a future Number of this Magazine, 
Phil, Mag. 8. 4, Vol. 21, No. 141. May 1861, Y 
