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POPULAR SCIENCE REVIEW. 
itself. By drawing a series of exceedingly fine lines on steel, 
or any other metal, we may produce the same phenomena. Iris 
ornaments or Barton’s buttons are obtained by cutting such 
fine lines on the surface of polished steel. 
Space will allow only of our referring very briefly to the 
splendid chromatic phenomena dependent on the Polarization 
of Light. In some future number we may possibly be tempted 
to enter more at large into this fertile field of inquiry. To 
take the most simple form of illustration : — If we receive a ray 
of Light upon a plate of glass placed at an angle of about 56°, 
a portion of the ray is transmitted, and a portion is reflected. 
Now, if we place a blackened mirror, to receive the reflected 
ray, it will be found that the ray has undergone the change 
which we term Polarization. If a slice of sulphate of lime or 
mica be placed between the two and we observe its image in 
the black mirror, we shall see a series of colours such as are 
shown in Fig. 7 ; while, if this is turned round a quadrant of 
the circle, these are changed, and appear as represented in 
Fig. , 8 - 
Brief and necessarily imperfect as this description of the 
phenomena of colour has been, it is hoped that the more 
important physical states upon which the production of colour 
depends will have been rendered intelligible. 
All colour is dependent upon Light. Every variation in tint 
or hue is determined by the physical condition of the surface 
upon which the incident Light falls. Reflection, absorption, 
refraction, diffraction, and polarization, are all engaged in pro- 
ducing that exquisite display which adorns the fields of Nature, 
and which is so effective within the domains of art. 
