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WAX

2059

WAXWING

\/gh, where g, as before, is the acceleration of gravity and h is the depth of the water. The speed of waves in shallow water is, therefore, independent of wave length.

Ripples. In the case of water waves which are very short — say less than about 4 millimeters — the surface tension (q. v.) of the water is the principal factor in determining the speed of the waves,

which is-2.'"' -, where T is the value of the A. p.

surface-tension, A. the wave length and p the density.

The slowest of all waves are those which are about 16 millimeters long. Waves shorter than this are called ripples. It is important to note that the speed of ripples, unlike that of waves, varies inversely as the wave-length.

Waves in Stretched Strings. These waves are seen when a stretched clothes-line is struck with a walking stick. They occur also in all stringed musical instruments and often in long belts in power-houses. The speed of the wave here depends upon two factors only: the tension or the force with which the string is stretched, say F, and the mass per unit-length of the string, say p.

Then

Speed = -% / —•

Sound Waves. These travel in gases, liquids and solids. The character of these waves is described in ACOUSTICS. There also will be found the evidence for thinking that sound is a wave-motion.

The speed of sound-waves in air was first computed by Newton and Laplace, and found to be as follows:

where p denotes the pressure of the air, p its density and 7 a constant, viz., the ratio between the specific beats of air at constant pressure and at constant volume.

In the case of a sound-wave traveling in water we have

Speed

VBull Den.

•Ik Modulus •sity

But in case sound travels through a solid rod, as, for instance, a fence made of gas-pipe, we have

f Young's Modulus Speed — ^1 Density

Light Waves. The evidence that light consists of a wave-motion is presented in LIGHT. Concerning the nature of light-waves very little is known; but it used to be thought that they were elastic disturbances in a

solid ether, in which case the speed of light waves would have been given by the following equation:

Speed

I Rigi

= ^j Den

'.dity of Ether .sity of Ether

It is now generally believed that light consists in electrical disturbances of the ether, in which case the speed of light waves would be determined as follows:—

Speed=

i/

where \i is the magnetic permeability of the medium and K the specific inductive capacity of the medium.

Besides these, there are many other kinds of waves, as the tides, barometric waves, temperature waves, solitary waves etc., the discussion of which is beyond our limits of space. For these, as well as the composition of waves, stationary waves etc., the larger treatises must be consulted. One of the best of these is Lamb's Hydrodynamics. HENRY CREW.

Wax is a solid, fatty substance of animal and vegetable origin. It is harder than fat, and does not melt so easily. It will not dissolve in water, and burns with a bright flame. Bees' wax, Chinese insect-wax and spermaceti are animal waxes, while Japanese wax, palm-wax and myrtleberry-wax are vegetable waxes. Bees' wax is secreted by the bees, and forms the cells in which they store honey. It is prepared by draining out the honey, melting the comb in boiling water, and collecting the wax from the top of the water as it cools. It is, in its natural state, a light yellow color, and is made into white wax by bleaching. It is produced in large quantities, and used mainly for the manufacture of candles. Chinese wax is supposed to be the product of an insect. It is found as a thin white coating on the branches of certain trees, and is removed with boiling water. It is white, like spermaceti, and is used for candles. Japanese wax is got from the fruit of a tree by boiling it and collecting the wax; palm-wax is scraped from the branches of two kinds of South American palms; and car-nauba wax is found on the leaves of the carnauba palm, and is obtained by drying the leaves and shaking off the wax like dust. Myrtleberry-wax or candleberry-wax is made from the berries of the wax-myrtle or bay berry, and, as it burns about as well as bees' wax and costs only a quarter as much, it is largely used. Mineral wax is a substance found oozing in small quantities from rocks in coal regions. Paraffin, produced from shale and petroleum, is also much used as a wax for candles etc. See BEES, PARAFFIN and SPERMACETI.

Wax7wing', the name for birds having the* wings, at times, ornamented with sma,^