1823.] Mr, Wheatstone on Sound, 89 



same plane with the right angle, in which case the former will 

 be trans versally, or the latter longitudinally transmitted in the 

 new direction; or their axis may be perpendicular to the plane 

 of this new direction, under which circumstances neither can be 

 communicated.'^ In explaining the polarization of light, there 

 is no necessity to suppose that the reflecting surfaces act on the 

 luminous vibrations by any actual attracting or repulsing force, 

 causing them to change their axes of vibrations ; the directions 

 of the vibrations in different planes, as I have proved exist in 

 the communication of sound, is sufficient to explain every phe- 

 nomenon relative to the polarization of light. 



Let us suppose a number of tuning forks oscillating in differ- 

 ent planes, and communicating with one conducting rod ; if the 

 rod be rectilinear, all the vibrations will be transmitted, but if it 

 be bent at right angles, they will undergo only a partial trans- 

 mission; those vibrations whose planes are perpendicular, or 

 nearly so, to the plane of the new direction, will be destroyed. 

 The vibrations are thus completely polarized in one direction, 

 while passing through the new^ path, and on meeting with a new 

 right angle, they will be transmitted or not, accordingly as the 

 plane of the angle is parallel with, or perpendicular to, the axes 

 of the vibrations. In this point of view, the circumstances 

 attending the phenomena are precisely the same as in the 

 elementary experiment of Mains on the polarization of hght. 



Double refraction is a consequence of the laws of polarization, 

 by which a combination of vibrations having their axes in differ- 

 ent planes, after travelling in the same direction, are separated 

 into two other directions, each polarized in one plane only. 

 That this well-known property of light has a correspondent m 

 the communication of phonic vibrations, I shall now demonstrate. 

 When two tuning forks, sounding different notes by a constant 

 exciter, and making their oscillations perpendicularly to each 

 other, have their vibrations transmitted at the same time through 

 one rod, at the opposite extremity of which two other conduc- 

 tors are attached at right angles, and when each of these con- 

 ductors is parallel with one of the axes of the oscillations of the 

 forks, on connecting a sounding board with either conductor, 

 those vibrations only will be transmitted through it which are 

 polarized in the same plane with the angle made by the two rods 

 through which the vibrations pass ; either sound may be thus 



• I have just seen a paper by M. Fresnel, entitled " Considerations Mecaniques sur 

 la Polarization de la Lumiere," in which this emment philosopher had previously arrived 

 at the same conclusions with respect to light, as I have proved in this communication 

 respecting sound. The important discoveries of Dr. Thomas Young, followed by those 

 of M. Fresnel, have recently re-established the vibratory theory of light, and new facts 

 are every day augmenting its probability. The new views in acoustical science, which 

 I have opened in this paper, will, I presume, give additional confirmation to the opinions 

 of these eminent philosophers ; and I hope, when I resume the subject, to be enabled to 

 account for the principal phenomena of coloration, v/ith regard to their acoustic analo- 

 gies, in a way calculated to establish the permanent validity of the theory. 



