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Transactions of the Wisconsin Academy of Sciences, Arts and Letters
volume IV (1876-1877)

Davies, J. E.
Report on recent progress in theoretical physics,   pp. 241-264 PDF (6.7 MB)


Page 241


              Recent Progress in Theoretical Physics.           241
REPORT ON RECENT PROGRESS IN THEORETICAL
                            PHYSICS.
                   By J. E. DAVIES, A. M., M. D.,
             Professor of Physics in the University of Wisconsin.
                              PART II.
      THE MAGNETIC ROTATORY POLARIZATION OF LIGHT.
  it is a well known fact that a ray of plane polarized light,
vibrating in any azimuth, will, on passing through a lamina of
quartz, have the azimuth of that vibration changed by an amount
depending upon the thickness of the lamina and the wave length
of the particular kind of light employed. The direction, right or
left, of this rotation of the plane of vibration depends upon the
            NOTE TO PREVIOUS PAPER ON "VORTEX MOTION."
  For the production of large-sized vortex rings, the device shown in Fig.
1
is used by Prof. Tait. It is an ordinary wooden box, with a large circular
hole cut out of one end, and the other covered tightly with elastic cloth.
It
                                                    can be filled with
                                                    smoke    from  a
                      - -~~~~--, ~ ~ ~ ~   ~        couple of retorts,
                                                 0 one    containing
                                                    Ammonia and the
                    \\\~\\\\\i\\ยบ\\\ \\\\\\\\other Hydrochlor-
                                                    ic Acid. This will
                      I       I II                 ~~~~give copious
                                                    clouds of chloride
                                                    of Ammonium,
                      Tigs                         'which are driven
outjin vortex rings, on striking the elastic cloth. It has been objected
that
the rings thus produced do not behave as Helmholtz' mathematical results
imply. It is not to be expected that they should; for Helmholtz' investiga-
tion upon vortex motion expressly assumes that the medium in which the
rings are formed is afi-ictionless fluid, which air is not. The rings are
truly
air rings, the accompanying smoke merely serving to make them visible.
This is finely shown by sending air rings from a second box against the
smoke rings already formed. The invisible air rings are made manifest by
the jostling of the smoke rings as they are struck by them. The suddenness
of this movement is often very striking.
16


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