The rays of light are reflected from substances which are light and brilliant, as glass, crystals, steel, etc. Other substances absorb light, and always appear dark and dull.

We see ourselves in a mirror by the reflected rays of light from our own face, which, striking the surface, are reflected back to our eyes. The reason of this is, that the rays cannot pass through the metal with which the back of the glass is covered, and therefore, are thrown back in reflection. Looking-glass is an excellent reflector of light, water is a good one, and polished metal also; therefore before glass was known, the maiden gazed at her face in a limpid stream, or decked her tresses by the reflection of a polished steel mirror.

Light is of the utmost importance to health. Mothers should beware of a dark nursery; neither animals nor plants will flourish in dark places. It is to light that we owe the beautiful colours which deck the universe.

Every ray of light contains the colours of the rambow. Some things reflect one of these colours and some another, according as their surface is constructed, physically and chemically. The swiftness or slowness with which the undulations of ether are thrown back from surfaces causes colour. Quick undulations produce blue, violet, and their different shades. in order to produce the violet colour, the undulations of ether must be 699 millions of millions in a second of time. Slow undulations produce red; the ether being thrown off the surface of the body at the rate of 477 millions of millions of vibrations in a second.

A Simple demonstration of the property of Retraction.

Yellow is the medium of undulations between blue and red. Red. blue, and yellow are the three primary colours, the others are compounds of them and affected by the same laws.

Black objects are without colour, because their surfaces will not reflect at all the undulations of ether which touch them, and which consequently cease. White objects set in motion all the undulations of ether, so as to reflect all the rays together, the effect of which is to produce white light.

There are of course many colouring matters in existence, that is, matters which affect these undulations of ether. Chlorophyll, for example, which gives the green colour to leaves and is formed by the agency of the sun's rays; vegetation grown out of sunlight is yellow and faded-looking.