The Wonder Book Of Knowledge Part 29

[Ill.u.s.tration: BRIQUETTING MACHINE

Enormous quant.i.ties of coal are lost at the mines in coal dust. By adding a binding material, such as pitch, and pressing the mixture into briquettes or small bricks, an excellent fuel is made.]

[Ill.u.s.tration: MINE RESCUE WORK

The mine rescue crew is using the canary-bird test for poisonous gas.

The bird succ.u.mbs to gas earlier than a man and thus indicates a dangerous condition of the atmosphere. The canary is revived by oxygen and the crew puts on safety helmets before proceeding.]

There are many varieties of coal, varying considerably in their composition, as anthracite, nearly pure carbon, and burning with little flame, much used for furnaces and malt kilns; bituminous, a softer and more free-burning variety; and cannel or "gas-coal," which burns readily like a candle, and is much used in gasmaking. The terms semi-anthracite, semi-bituminous, c.o.king coal, splint coal, etc., are also applied according to peculiarities.

All varieties agree in containing from 60 to over 90 per cent of carbon, the other elements being chiefly oxygen and hydrogen, and frequently a small portion of nitrogen. Lignite or brown coal may contain only 50 per cent of carbon. For manufacturing purposes coals are generally considered to consist of two parts, the volatile or bituminous portion, which yields the gas used for lighting, and the substance, comparatively fixed, usually known as c.o.ke, which is obtained by heating the coals in ovens or other close arrangements.

About 260,000,000 tons of coal are annually mined in Britain, the value being over $300,000,000. Large quant.i.ties are exported. The British coal-fields, though comparatively extensive (covering about 9,000 square miles), are far surpa.s.sed by those of several other countries, as the United States and China, the former having coal-fields estimated to cover about 451,000 square miles; the latter over 200,000 square miles.

Britain no longer mines the largest quant.i.ty, having been far surpa.s.sed by the United States. Other countries in which coal is worked are Belgium, France, Germany, Russia, India, New South Wales and Canada.

China has. .h.i.therto mined only on a small scale.

The annual production of anthracite coal in Pennsylvania is more than 86,000,000 tons of 2,240 pounds, valued at the mines at $198,000,000. In 1910 there were produced of bituminous coal 388,222,868 tons, valued at $463,654,776; amount of c.o.ke manufactured, 37,000,000 tons. This was distributed widely over the country, the greatest producers, after Pennsylvania, being Illinois, West Virginia, Ohio, Alabama and Colorado.

Recently a very large output of coal has been discovered in Alaska, the value of which is as yet undetermined, though it is believed to hold a vast quant.i.ty of coal. The value of the western coal-fields also is far from known, and since 1906 very extensive tracts of coal-bearing lands have been withdrawn from settlement, princ.i.p.ally in Wyoming, Montana, Colorado, Utah and New Mexico, their beds being largely of lignite.

These cover about 50,000,000 acres, and, with those of Alaska, are held by the government as national a.s.sets. The mines of Alaska are claimed to be exceedingly rich, both in bituminous and anthracite coal, the beds examined being estimated to contain 15,000,000,000 tons, while there are large districts unexamined. They have not yet been worked, the government keeping them back for public owners.h.i.+p.

How can We Hear through the Walls of a Room?

We are able to hear easily through the walls of many rooms because the material used in those walls are good conductors of sound. We know that some things are better conductors of heat than others, and just in that same way, some things conduct sound better than others. Wood has been shown to be an even better conductor of sound than air. Most of us have stood at the foot of an overhead trolley pole to see if we could hear a car coming, and we know that the reason we did this was because we could hear the wire humming, when we put our ears against the pole, even though we could not hear any sound in the air.

When we are in a room that has wooden walls we can hear sounds in the next room very plainly, not because the wall is thin, but because the wood in the wall is a good conductor of sound. Other walls made of different kinds of material, are not as good conductors of sound. While you may hear through them, you cannot hear as plainly as you can through a wooden wall.

What is a Diesel Engine Like?

The Diesel engine has caused a great deal of comment of late years because of the spectacular uses to which it has been successfully applied. A specially constructed Diesel engine was probably the chief aid in the accomplishment of the first submarine trans-Atlantic voyage by the German submarine "Deutschland."

It is an oil engine which was invented by Rudolph Diesel in 1893.

The engine operates at compression pressures very much higher than those used in any other internal combustion engines, and it dispenses with the usual igniting devices by rendering the air charge incandescent by compression.

[Ill.u.s.tration: THE DIESEL ENGINE]

The efficiency of the Diesel engine is high, and it can use low grades of fuel, but it has the disadvantage of greater weight per horse-power than other engines.

It has found increasing favor for use in marine propulsion, and in 1913 was adapted to high-speed railway service, and put into use in Germany.

What does the Sheep-Grower Get for the Wool in a Suit of Clothes?

A man's ordinary three-piece fall suit has about nine pounds of wool in it. Such a suit might cost somewhere between twenty and forty dollars, depending on whether it was bought ready made or whether it was made to order. If the price was questioned, the retailer would probably explain that it was all wool and that the wool cost was the reason it was expensive, and still the sheep-man who raised the wool only received an average of about eighteen cents a pound, or $1.62, for all the wool used on the suit.

Of course, the largest part of the cost of a suit of clothes is really accounted for by the cost of transportation, weaving, tailoring and selling, but we must all agree that the sheep-man who tends the flock all winter and cuts the wool in the spring is not to blame for high prices.

The Story in a Silver Teaspoon[16]

The spoon is older than history. There is, perhaps, no article or utensil of common use today that can trace an earlier origin. The evolution and development of the spoon into the graceful and beautiful forms in use on our tables is fascinating and instructive.

Primitive men of the Stone Age used an implement that might by courtesy be called a spoon. From then on down through the Egyptian, Greek and Roman civilizations it can be clearly traced in varying forms and substances--wood, sh.e.l.l, flint, bone, ivory, bronze and the precious metals, gold and silver.

A witty Frenchman has said that spoons, if not as old as the world, are certainly as old as soup.

In the Bible is the first recorded mention of the use of spoons made of precious metal. This reference is the twenty-fifth chapter of the Book of Exodus, wherein the Lord commanded Moses to make golden spoons for the Tabernacle.

Excavations in Egypt have brought to light early examples of spoons of various materials, and it is certain that the early Greeks and Romans used gold and silver spoons, both at the table and in the Temple. Early specimens of spoons made of wood, ivory, bronze, silver and gold are preserved in the museums of Europe and Egypt.

During the early Christian and medieval eras spoons were in common use.

Saxon and Early English examples are to be seen in the English museums today.

The medieval spoon was of silver, horn or wood, etc. On the Continent, silver spoons were made much earlier than in England. In Italy they were in use probably long before 1000 A. D.

During the Tudor and Stuart reigns a fas.h.i.+onable gift at christenings was the apostle, so called because at the end of the handle was the figure of an apostle. Sometimes a thirteenth spoon was added, called the "Master" spoon, because it bore the figure of Christ. A complete set was a very valuable gift, and could only be afforded by the rich.

Folks of limited means used copper, pewter, latten or alchemy spoons; the latter two materials being somewhat like bra.s.s, examples of which are sometimes found in this country in the graves of Indians of the sixteenth and seventeenth centuries, showing their intercourse with early English traders.

At this period the stems were hexagonal, ending in an acorn, a bird or a ball, while the bowls were fig shape. Later the stems were bal.u.s.ter shape with a seal top, and at the time of the Commonwealth the stem became flat and perfectly plain. These latter are called "Puritan"

spoons.

Naturally, the early New England colonists brought with them the spoons they had used at home, and the early Colonial silversmiths followed closely the designs which they found at hand or which were later imported from England. In fact, within a few years after a certain type had become popular in the mother country, it was adopted in this country as the fas.h.i.+onable style. It is, therefore, easy to date, approximately, an American-made spoon, because it follows so closely in style the dated or hall-marked English spoon.

During the last quarter of the seventeenth century, both in England and America, spoons were generally of a style now known as rat-tail. From the end of the handle, down the back of the bowl to about the middle, ran a ridge shaped like a rat-tail. This is sometimes thought to have been an attempt to strengthen the spoon, but its use must have been purely ornamental, for it adds little strength to these strongly made spoons. Sometimes the rat-tail was shaped like a long V and grooved, while on each side were elaborate scrolls. The bowl was perfectly oval in shape, while the end of the handle was notched or trifid.

This style of spoon was continued, with modifications, through the first third of the eighteenth century. Then the bowl became ovoid, or egg-shaped, and the end of the handle was rounded, without the notch.

The rat-tail was gradually replaced by what is known as the drop, or double drop, frequently terminating in a conventionalized flower or sh.e.l.l, or anthemion, while down the front of the handle ran a rib.

Later, the bowl became more pointed, the drop was replaced by a tongue, and the handle, after 1760, instead of slightly curving to the front at the end, reversed the position. Somewhat later, the handle became pointed, and was engraved with bright, cut ornaments and a cartouch at the end in which were engraved the initials of the owner.

During the first ten years of the nineteenth century a popular style was the so-called coffin-shaped handle, succeeded, probably about 1810, by a handle with a shoulder just above the junction with the bowl, while the end became fiddle-shaped or of a style now known as tipped, shapes produced to this day.

Until about 1770, spoons were of three sizes: the teaspoon, as small as an after-dinner coffee spoon; the porringer spoon, a little smaller than our present dessert size; and the tablespoon, with a handle somewhat shorter than that of today.

[Ill.u.s.tration: LATTEN SPOONS

One found in an Indian grave at Deerfield, Ma.s.s., and the other in an Indian grave at Hadley, Ma.s.s. Period of about 1660. Actual size, 6 inches and 6-1/4 inches.]

So few silver forks have been found in collections of old silver that it forces the belief that they were generally made of steel, with bone handles. There seems no reason why, if in general use, silver forks should not now be as common as spoons.