its delicate springs, in not being so much influenced by heat and
cold, and consequently in its accuracy in giving the time.




CHAPTER XX.

LIGHT, LIME LIGHT, MAGNESIUM LIGHT, ELECTRIC LIGHT, RAINBOW,
PRISM, SPECTRUM, COLORS, PHOTOGRAPHY, CAMERA OBSCURA, STEREOSCOPE,
KALEIDOSCOPE.


Do you know something about the nature of Light?

Light is a mere form of vibration like sound, and like sound it
requires some source to set this vibration going, and some medium to
carry this vibration as air carries sound.


Is not the air this medium?

No, it is supposed that there is an elastic fluid called "ether" which
pervades all space and matter, and if the molecules of a body are in
motion they have the power of setting this ether in motion. The
movement thus produced will appear either as heat or light according
to its velocity.


What sources of light do you know?