CHAPTER VII.

LIGHT.

Theories of the Nature of Light--Hypotheses of Newton and Huygens--Sources of Light--The Sun--Velocity of Light--Transparency--Dark Lines of the Spectrum--Absorption of Light--Colour--Prismatic Analysis--Rays of the Spectrum--Rainbow--Diffraction--Interference--Goethe’s Theory--Polarisation--Magnetisation of Light--Vision--The Eye--Analogy--Sound and Light--Influence of Light on Animals and Vegetables--Phosphorescence arising from several Causes--Artificial Light--Its Colour dependent on Matter 118