What is an Anemometer?

An instrument for measuring the velocity and force of the wind, and by which storms, at a distance, can be predicted.

What is a Chronometer?

A time-piece of delicate and exact construction, chiefly employed by astronomers and navigators.  It differs only from an ordinary watch in 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?

We are told that the principal source of light on earth is the sun, either directly with its own beams or indirectly by supplying us with combustibles to produce light; for oil, gas, candles, and most of the substances used for producing light and heat when burning are but sending forth in another form the rays of the sun which were stored up in nature’s economy.

Another source of light is the result of chemical action, such as the lime, magnesium, and electric light.  A third source of light is phosphorescence, as we see it in the glow-worm and fireflies.

What is the Drummond or Lime Light?

It is one of the most brilliant of artificial lights.  When a stream of oxygen and one of hydrogen under pressure are brought together and mixed within a few inches of the end of a blowpipe, the mixture on lighting burns with a colorless flame possessing intense heat.  If this flame be made to play upon a ball of carbonate of lime, the lime on becoming white hot gives off a powerful incandescence.

     Incandescence, the glowing whiteness of a body caused by
     intense heat.

What is a Blowpipe?

A tube, usually bent near the end, terminated with a finely-pointed nozzle, for blowing through the flame of a lamp or gas-jet, producing thereby a small conical flame possessing intense heat.  It is used in soldering silver, brass, etc.  A mixture of oxygen and hydrogen when ignited constitutes the hydrogen blowpipe, invented by Dr. Hare of Philadelphia.

What is Magnesium Light?

When the metal magnesium is rolled out into a fine ribbon and heated to red heat it burns with a dazzling light.