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by Newton (was Snell in Calcite)



Another calcite dominated weekend. We are trying to understand
under what conditions the refracted (on two perfectly parallel faces of
natural CaCO3) laser beams (O and E) are parallel to each other and
under what conditions they are diverging. Both situations are being
experimentally observed; the divergence angles are sometimes as
large as nearly one degree. I am working with Bob Dorner and
Brian Heinold; we will share the conclusion, when (and if) the
puzzle is resolved, one way or another.

Meanwhile let me quote I. Newton who did examine the double
refraction in "Iceland Crystal" and shared his recipe for polishing
it "... with Pitch, Lather or Parchment. Afterwards it must be rubb'd
with a little Oil or white of an Egg, to fill up its Scratches; whereby
it will become very transparent and polite. But for several Experiments,

it is not necessary to polish it. If a piece of this crystalline Stone
be
laid upon a Book, every Letter of the Book seen through it will
appear double, by means of a double Refraction. And if any beam of
Light falls either perpendicularly, or in any oblique Angle upon any
Surface of this Crystal, it becomes divided into two beams by means
of the same double Refraction. Which beams are of the same Colour
with the incident beam of Light, and seem equal to one another in the
quantity of their Light, or very nearly equal. One of these ...."

I found this in the book "Polarized Light" edited in 1975 by William
Swindell (ISBN: 0-470-83997-X). It is a compilation of classical
quotes on various aspects of polarization, eight pages from Newton
(Qu.25 of "Optiks", 4th ed., London 1730, pp 354-361), twenty
pages from C. Huygens, etc. etc. up to 1973.
Ludwik Kowalski