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In passing through a prism a ray of light is divided into colours. To explain this it was supposed that the atoms from the sun were compound consisting of several colored bodies bound together into one wh. were separate in their passage through the glass .  Addition No 2.
Again it is discovered that at certain equidistant places in a prism [[image - light hitting prism]] the rays of light go through at others are reflected.  To explain this it is sugested that the atoms are polerized that they revolve in space and that the distance at wh. they go through & are reflected from the prism is equal to half a revolution.  But it is also discovered that the atoms must have different sides as well as different ends.  They will go through prism in certain directions & not in others.  The theory has become more and more complex and is at
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last abandoned but very many interesting and valuable phenomena have been discovered by its means.
It is known that sound is produced by undulations of the ethereal medium it is now suggested that light may be attributed to the same phenomenon.  Two waves of sound may be made so to interfere with each other that intervals of silence are produced.  The crest of one wave meeting the hollow of another if we may so speak - as in the beats of an organ pipe.  If light consists of waves intervals of [[darkness?]] ought to be produced in the same way.  This by experiment is found to be the case.  The great thing in testing a theory is to devise experiments that will give the information desired with accuracy.  We were here interrupted
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