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                               LETTERS

                                  ON

                            NATURAL MAGIC,

                             ADDRESSED TO

                        SIR WALTER SCOTT, BART.

                                  BY

                   SIR DAVID BREWSTER, LL.D., F.R.S.

      [Illustration: Three figures on hill-top saluting sunrise]

                           SEVENTH EDITION.

                                LONDON:
                WILLIAM TEGG AND Co., 85, QUEEN STREET.
                              CHEAPSIDE.
                                 1856.




CONTENTS.


  LETTER I.

  Extent and interest of the subject--Science employed by
  ancient governments to deceive and enslave their subjects--Influence
  of the supernatural upon ignorant minds--Means
  employed by the ancient magicians to establish
  their authority--Derived from a knowledge of the phenomena
  of Nature--From the influence of narcotic drugs
  upon the victims of their delusion--From every branch of
  science--Acoustics--Hydrostatics--Mechanics--Optics--M.
  Salverte’s work on the occult sciences--Object of
  the following letters                                  Page 1


  LETTER II.

  The eye the most important of our organs--Popular description
  of it--The eye is the most fertile source of mental
  illusions--Disappearance of objects when their images fall
  upon the base of the optic nerve--Disappearance of objects
  when seen obliquely--Deceptions arising from viewing
  objects in a faint light--Luminous figures created by
  pressure on the eye, either from external causes or from
  the fulness of the blood-vessels--Ocular spectra or accidental
  colours--Remarkable effects produced by intense
  light--Influence of the imagination in viewing these
  spectra--Remarkable illusion produced by this affection
  of the eye--Duration of impressions of light on the
  eye--Thaumatrope--Improvements upon it suggested--Disappearance
  of halves of objects or of one of two persons--Insensibility
  of the eye to particular colours--Remarkable
  optical illusion described                                  8

  LETTER III.

  Subject of spectral illusions--Recent and interesting case
  of Mrs. A.--Her first illusion affecting the ear--Spectral
  apparition of her husband--Spectral apparition of a cat--Apparition
  of a near and living relation in grave-clothes,
  seen in a looking-glass--Other illusions, affecting
  the ear--Spectre of a deceased friend sitting in an
  easy-chair--Spectre of a coach-and-four filled with
  skeletons--Accuracy and value of the preceding cases--State of
  health under which they arose--Spectral apparitions are
  pictures on the retina--The ideas of memory and imagination
  are also pictures on the retina--General views of
  the subject--Approximate explanation of spectral apparitions  37


  LETTER IV.

  Science used as an instrument of imposture--Deceptions
  with plane and concave mirrors practised by the ancients--The
  magician’s mirror--Effects of concave mirrors--Aërial
  images--Images on smoke--Combination of
  mirrors for producing pictures from living objects--The
  mysterious dagger--Ancient miracles with concave
  mirrors--Modern necromancy with them, as seen by Cellini--Description
  and effects of the magic lantern--Improvements
 