There are two cla.s.ses of chemical fire extinguishers: the soda and acid tank or three-gallon type, and the one-quart pump type. The latter came when the efficiency of carbon tetrachloride as an extinguishing agent became known. All the extinguishers of this type use a liquid which has carbon tetrachloride as a base. The liquid is a combination of organic materials with an aromatic odor and high specific gravity. When subjected to a temperature of 200 F. or over, it changes to a heavy, cohering, non-poisonous gas blanket which surrounds the burning material and cuts off the air supply necessary for the life of the fire.

The first one-quart pump type of extinguisher appeared in the United States in 1907. There was little resemblance between it and the extinguisher of today. A cylindrical tube with a perforated end contained the liquid. The user was expected to sprinkle the liquid over the fire just as salt is sprinkled from a saltcellar over meat.

One company applied the idea of pumping the liquid on the fire in 1909.

They introduced a single-acting pump. The user inserted the nozzle in the liquid, drew it into the pump, and then ejected it on the flames.

This company subst.i.tuted a double-acting pump early in 1910. The container for the fluid and the pump were thus combined and the extinguisher had the general appearance of those now on the market.

Bra.s.s construction was subst.i.tuted for tin in the latter part of 1910, and in 1911 all bra.s.s construction was adopted. The extinguisher has remained practically unchanged since 1911.

This was the only one-quart type extinguisher on the market until 1911.

Since then several others have been marketed. All use an extinguishing liquid with carbon tetrachloride as a base. They differ princ.i.p.ally in the manner of its ejection. The original type pumps the liquid out by hand. Others eject it by air pressure or by a combination of the two methods. The objection made by some people to the use of air pressure is that it demands attention and the use of a complicated mechanism which more readily gets out of order.

[Ill.u.s.tration]

The liquid extinguishing agent has seen little change since 1907. In 1914 it was modified so that it injures nothing with which it comes in contact. It puts out fires originating in oily wastes, turpentine and sh.e.l.lac, and fires resulting from the ignition of gasoline, benzine or acetylene gas, on which ordinary chemicals and water are useless. It extinguishes electrical fires without injuring insulation or apparatus and without injury to the operator. A stream of this liquid has been directed upon a circuit of 110,000 volts without the least harm to the operator.

A German originated the soda and acid type of extinguisher from tests made in Denmark between 1830 and 1835. The enterprising Teuton divided a hogshead into two parts. He filled one part with a solution of alcohol and water; the other division was partly filled with sulphuric acid. His problem was to unite the two when he wanted to put out a fire. This was accomplished by fastening a charge of gunpowder in such a way that when exploded it would break the part.i.tion and mix the solutions. French ingenuity added slight improvements a short time later.

[Ill.u.s.tration]

Alexander Graham, of Lexington, Virginia, applied for patents on this type of extinguisher a number of times between 1844 and 1849. He was unable to patent his invention. A fire extinguisher company in Chicago and one in Baltimore obtained patents on what was known as the "bicarbonate of soda and sulphuric acid" extinguisher by a special act of Congress in 1865. These patents were known as the Graham patents, and both extinguishers were called the "break-bottle type" because the soda and acid were mixed when a gla.s.s bottle containing the latter was broken.

The "up-set" type of soda and acid extinguisher was adapted by Meyerose in St. Louis in 1891. The improvement lay in the vessel containing the acid being upset instead of broken. This extinguisher was of copper construction and had a capacity of three gallons. One fire extinguisher company improved upon the original type of "up-set" extinguisher in 1893 by lining the extinguisher with lead which the acid did not affect.

Since 1893 there have been no improvements of consequence on the soda and acid extinguisher. It consists of a cylindrical container with a solution of sodium bicarbonate. Over the bicarbonate is suspended a vessel containing sulphuric acid. When in use the acid is tilted over and comes in contact with the bicarbonate. This liberates carbon dioxide. The pressure generated is sufficient to throw a stream of the bicarbonate solution forty feet. The chief disadvantages of the soda and acid type of extinguisher are that its weight makes it c.u.mbersome to operate and it cannot be safely used on electrical fires until the current has been turned off.

How is Gold Leaf Made?

The gold is cast into ingots weighing about two ounces each, and measuring about three-quarters of an inch broad. These ingots are pa.s.sed between steel rollers till they form long ribbons of such thinness that a square inch will weigh six and one-half grains. Each one of these is now cut into 150 pieces, each of which is beaten on an anvil till it is about an inch square. These 150 plates are interlaid with pieces of fine vellum about four inches square, and beaten till the gold is extended nearly to the size of the vellum leaves. Each leaf is then divided into four, interlaid with goldbeater's skin, and beaten out to the dimensions of the skin. Another similar division and beating finishes the operation, after which the leaves are placed in paper books ready for use. The leaves are about three and a quarter inches square and are produced in ten different shades of color, according as the gold was alloyed with much or little copper or silver.

What is the Natural Color of Goldfish?

It is greenish in color in the natural state, the golden-yellow color being found only in domesticated specimens, and retained by artificial selection.

These fishes are reared by the Chinese in small ponds, in basins or porcelain vessels, and kept for ornament. By careful selection, many strange varieties have been propagated.

They are now distributed over nearly all the civilized parts of the world, but in large ponds they readily revert to the color of the original stock.

When was "Liquid Fire" First Used in Warfare?

Long before the European war, an inflammable and destructive compound was used in warfare, especially by the Byzantine Greeks.

It was poured from caldrons and ladles, vomited through long copper tubes, or flung in pots, phials and barrels.

The art of compounding it was concealed at Constantinople with the greatest care, but it appears that naphtha, sulphur and nitre entered into its composition.

How did the Greyhound Get His Name?

The name appears to have no reference to the color, but is derived from the Icelandic "grey," meaning a dog. They are used chiefly in the sport of coursing, a work for which their peculiar shape, strength, keenness of sight and speed make them exceedingly well fitted. This sport is preferred by many people to horse racing. There are several varieties, as the Irish greyhound, the Scottish, the Russian, the Italian and the Turkish.

The common greyhound is of an elegant make of body, and is universally known as the fleetest of dogs.

A good hound has a fine, soft, flexible skin, with thin, silky hair, a great length of nose, contracting gradually from the eye to the nostril, a full, clear and penetrating eye, small ears, erect head, long neck, chest capacious, deep, but not wide, shoulders deep and placed obliquely, ribs well arched, contracted belly and flank, a great depth from the hips to the hocks of the hind-legs, fore-legs straight and shorter than the hind legs.

[Ill.u.s.tration: THE GATEWAY TO AMERICA

The famous statue of Liberty in New York Harbor. The gra.s.sy s.p.a.ce in the foreground is Battery Park, and the round building is the Aquarium. Here in the early days stood a rude "castle" or fort, later supplanted by an opera house. Washington often walked in the old garden around the building, as did other great Americans.

_Copyright by Underwood & Underwood, N. Y._]

Why is It Called "Battery Park"?

The extreme southern end of Manhattan Island is both popularly and officially known as "Battery Park" because it was fortified in the seventeenth century for the protection of the town. In the picture the round building is the Aquarium, which is abundantly supplied with sea and river fishes. The picture was taken from a platform of the Elevated Railway, the trains of which run from this point to practically the northern extremity of the island, making stops en route at stations situated at approximately every eighth street.

Manhattan Island was first visited in 1609 by Henry Hudson. The first settlement was located three years afterward on the present site of Battery Park. The Dutch settlement here formed gradually grew into a town called New Amsterdam, which in 1648 had 1,000 inhabitants. In 1664 it surrendered to the British and took its new name from the Duke of York, into whose hands it came. It was the capital of the State of New York from 1784 to 1797, and from 1785 to 1790 it was the seat of the Federal Government. Washington was inaugurated to the presidency at New York in 1789. The opening of the Erie Ca.n.a.l in 1825 gave the city command of internal commerce and since that date its progress has been rapid, almost beyond example.

How do we Know that the Earth is Round?

We have all been taught that the earth is a nearly spherical body which every twenty-four hours rotates from west to east around an imaginary line called its axis--this axis having as its extremities the north and south poles respectively--while in the course of a year it completes a revolution around the sun.

To an observer whose view is not obstructed, any part of the earth presents itself as a circular and horizontal expanse, on the circ.u.mference of which the heavens appear to rest. Accordingly, in remote antiquity, the earth was regarded as a flat, circular body, floating on the water. But even in antiquity the spherical form of the earth began to be suspected.

It is only on this supposition that we can explain how the horizon of vision grows wider and wider the higher the position we choose, how the tops of towers and mountains at a distance become visible before the bases, how the hull of a ship disappears first as she sails away, and how, as we go from the poles towards the equator, new stars become visible. Besides these proofs, there are many others, such as the circular shadow of the earth seen on the moon during an eclipse, the gradual appearance and disappearance of the sun, and especially the fact that since 1519 the earth has been regularly circ.u.mnavigated.

The earth is not, however, an exact sphere, but is very slightly flattened at the poles, so as to have the form known as an oblate spheroid. In this way the polar diameter, or diameter from pole to pole, is shorter than the diameter at right angles to this--the equatorial diameter. The most accurate measurements make the polar diameter about twenty-seven miles less than the equatorial, the equatorial diameter being found to be 7,925.6 miles, and the polar 7,899.14.

What were "Ducking Stools"?

A ducking stool was a sort of a chair in which "common scolds" were formerly tied and plunged into water. They were of different forms, but that most commonly in use consisted of an upright post and a transverse movable beam on which the seat was fitted or from which it was suspended by a chain.

The ducking stool is mentioned in the Doomsday survey; it was extensively in use throughout the country from the fifteenth till the beginning of the eighteenth century, and in one rare case at least--at Leominster--was used as lately as 1809.

The Story in Photo-Engraving[30]

Modern advertising would not have been possible without photo-engraving.

Attention has been attracted, desire has been created and goods have been sold, largely through the pictorial or other artistic embellishments which have lifted particular "ads" out of the ma.s.s and attracted the favorable attention of the cursory reader. Pictures are the universal language, not only to those of divers tongues, but to those of every stage of mental development.