The Wonder Book Of Knowledge Part 31

A patent automatic scale, designed to weigh the silver while depositing, is balanced to the exact weight of silver to be deposited on the article. The circuit is completed by turning a switch and the plating begins.

As soon as the articles receive the proper weight of silver, the scale beam rises, thus making a separate connection with the electro-magnet, which springs the switch, breaking the electric current and stopping the plating at the same instant, also ringing an alarm bell to notify the workman that the articles have received the proper weight of silver.

_Quality._--Standard silver-plated spoons are made in two grades of plate--triple and quintuple. The former, however, is the one generally used and answers all ordinary requirements. The quintuple grade is designed more particularly for hotels, restaurants, clubs and other inst.i.tutions where the wear is especially severe.

The Evolution of a Knife.

There are thirty-six stages in the evolution of a plain steel knife. At one end of the journey we see the cylindrical bar of steel, black and unlovely; at the other, the silver-plated knife, light, well-balanced and heavily plated with pure silver. In the case of other than plain knives, the work involves also the stamping of the pattern.

_Double Burnishing._--The thickness of the silver deposited, however, is not the only requisite to insure quality. The plating must be hard as well as thick. This is accomplished by means of a double-burnishing process after the article is plated and before it receives its final buffed finish.

The first burnishing is on machines and this is followed by hand burnishing. This process produces a hard plate.

[Ill.u.s.tration: 1. Steel cut to length. 2. Handle formed by 1,000-pound blow. 3. Handle margin, or flash, removed. 4. Blade drawn out through a pair of rolls. 5. Blade cut out to shape. 6. Knife roughed with coa.r.s.e emery. 7. Trade-mark etched. 8. After plating. 9. The finished knife.]

No matter how heavy the plate, if it is not properly burnished or hardened after plating, the article will not give satisfaction in long wear. When manufacturers treat their wares to as little burnishing as possible, practically relying upon the buff alone for their finish after plating, the result is most unsatisfactory. The buff finish looks all right, but it does not harden the silver sufficiently and in consequence the latter does not wear well. When the article comes out of the plating bath the silver deposited is in a comparatively porous and "fluffy"

state. The buffing will hit the high spots but the proper process turns the minute edges, closes the pores and makes the silver hard and compact, vastly increasing the wearing quality.

The silver thus deposited, is absolutely pure--finer, in fact, than any articles of sterling silver. Sterling is but .925 fine, requiring an alloy to stiffen it, whereas silver for plating can be used .999 fine.

How do Chimes Strike the Hour?

Chimes are ordinarily produced mechanically by the strokes of hammers against a series of bells, tuned agreeably to a given musical scale.

The hammers are lifted by levers acted upon by metallic pins or wooden pegs stuck in a large barrel, which is made to revolve by clockwork, and is so connected with the striking part of the clock mechanism that it is set in motion by it at certain intervals of time, usually every hour or every quarter of an hour.

The chime mechanism is sometimes so constructed that it may be played like a piano, but with the fist instead of the fingers.

[Ill.u.s.tration: _Courtesy of the Niagara Falls Power Co._

NIAGARA ELECTRIC TRANSMISSION LINE

Tower supporting high tension transmission cables of long span crossing of Niagara River between Buffalo and Fort Erie, Canada.]

How is Electricity Brought into a House?

The electric transmission of power is effected by employing the source of power to drive a machine called a dynamo, which generates an electric current.

This current is conveyed by a copper conductor, insulated from the earth, to the distant station, where it pa.s.ses through a machine called an "electromotor," one part of which is thereby made to revolve, and imparts its motion to the machinery which is to be driven.

This is the simplest arrangement, and is that which is commonly employed when the original currents are not of such high tension as to be dangerous to life in the case of accidental shocks. There is, however, a great waste of power in employing low-tension currents when the distance is great; hence it is becoming a common practice to employ high-tension currents for transmission through the long conductor which connects the two stations, and to convert these into low-tension currents before they reach the houses or workshops where they are to be used. This is done sometimes by employing the high-tension currents to drive a local dynamo which generates low-tension currents.

The discovery that a Gramme machine is reversible--that is to say, when two Gramme machines are coupled together and one is operated as a generator, the other will act as a motor--was an important step taken in the transmission of power. Numerous efforts, since then, have been made to utilize electricity for the transmission of power over a long range.

For this purpose the alternating current seems eminently adapted, as transformers only are needed to raise the line to high transmission voltage and to lower it again for use.

The possibilities offered by electrical transmission of water power for sections of country favored with waterfalls are numerous and have been extensively developed, which should result in making them great industrial centers. In this direction much has been done in utilizing the immense power of the Niagara Falls by electrical transmission, works having been built for this purpose both in New York and Canada, and several hundred thousand horse-power developed. The application of the power of waterfalls to the generation of electricity is rapidly extending, and promises to become a great source of mechanical power in the future.

What was the Origin of Masonic Signs?

Fable and imagination have traced back the origin of freemasonry to the Roman Empire, to the Pharaohs, the Temple of Solomon, the Tower of Babel, and even to the building of Noah's ark. In reality, it took its rise in the middle ages along with other incorporated crafts.

Skilled masons moved from place to place to a.s.sist in building the magnificent sacred structures--cathedrals, abbeys, etc.--which had their origin in these times, and it was essential for them to have some signs by which, on coming to a strange place, they could be recognized as real craftsmen and not impostors.

What is a Dictograph?

The dictograph, to which much publicity is now given, by reason of its use in detective work, is an instrument for magnifying sound. It was invented by K. M. Turner of New York, in 1907.

It consists of a master station in the form of a box less than a foot long and six inches deep, and any number of sub-stations that may be required. Any voice within fifteen feet is taken by the receiving instrument and carried over the wires to any distance within about a thousand miles.

It has now been adopted by a great many business organizations as a convenient means of inter-communication.

The Story of the Wireless Telegraph

Though one or more means of transmitting messages by electricity have been known now for a great many years, the mechanisms by which they are accomplished are understood only by those who take a general interest in physical science, and the few to whom electrical communication is a profession. So far as theory and details of working are concerned, there are a good many people still in the same shadowy frame of mind as the old Aberdeen postmaster, of whom the story is told. When asked to explain the working of a telegraph instrument he said, "Look at that sheep-dog. Suppose we hold his hind-quarters here and stretch him out until his head reaches Glasgow. Then if we tread on his tail here he will bark in Glasgow. As it is not convenient to stretch a dog, we stretch a wire, and that serves the purpose."

As the name implies, "stretching a wire" is unnecessary in wireless telegraphy, though in order to understand the finer points of theory one needs to stretch the imagination a little. That, however, is not so much, because there is any inherent obscurity or difficulty in the underlying principles, as because the mechanism of all electrical effects is more or less intangible. Electricity and magnetism operate across apparently empty s.p.a.ce, and the links which connect cause and effect have to be guessed at.

Three different methods have been made use of in wireless telegraphy, which may be cla.s.sed as conduction, induction and wave methods. In the first method currents are sent through the earth from an electrode to another at the sending station. In induction, use is made of the property which alternating currents possess of exciting similar currents in neighboring conductors, the aim being to get as intense a current as possible in the secondary circuit. Mr. W. H. Preece, of England, by combining the two, signaled in this way as far as forty miles. The third and the only method which has proved practically available is by the use of electro-magnetic waves.

Guglielmo Marconi, an Italian, after long experiment, patented in 1897 a method entirely independent of wires, the electric waves being sent, presumably, through the ether, by the aid of a transmitting apparatus, and being detected by a coherer, a gla.s.s tube filled with metallic filings, into the end of which the terminals of a relay circuit enter.

The wave falls on conducting material and, the spark gap being replaced by a coherer, the metallic filings magnetically cling together, closing the relay circuit, so that a signal is made. On breaking the current, a slight tap on the coherer or other means breaks the cohesion of the filings and the relay circuit is broken. In this way a rapid succession of signals can be sent.

In 1899 Marconi conducted in England an exhaustive series of successful experiments, sending messages across the English Channel from the South Foreland to the French coast near Boulogne, and extending his results until much longer distances were covered. The process of development was continued until, to the world's astonishment, signals were sent across the Atlantic and, finally, commercial messages were transmitted over this distance.

Marconi's system is based on the property supposed to be exerted by the vibrations or waves of electric currents pa.s.sing through a wire of setting up similar vibrations in the ether of s.p.a.ce. These waves extend in every direction from the point of departure, and by ingenious and very delicate receiving instruments their presence in s.p.a.ce is indicated and they are taken up in sufficient strength to repeat their pulsations and in this way reproduce the signals sent from the transmitter. One difficulty hitherto has been that a message may be received by hundreds of receiving instruments in all directions, thus preventing secrecy.

Many efforts have been made to overcome this defect, but as yet with only partial success.

The distance to which messages can be sent has so far depended largely on the height to which the wires extend above the earth's surface, lofty poles being erected at the stations. The height of these has been gradually increased until the Eiffel Tower at Paris has been utilized as a sending station. The strength of the electric waves has been similarly increased to add to their s.p.a.ce-penetrating capacity. The record of wireless telegraphy has been in this way improved until now it has come into daily compet.i.tion with other means of news sending. Methods of tuning the instruments have been adopted which limit the influence of the currents to properly tuned receivers and in this way some degree of secrecy is attained.

[Ill.u.s.tration: MARCONI WIRELESS STATION]

Though the honor of inventing the art of wireless telegraphy is generally ascribed to Marconi, this is to give him more credit than he deserves. The principles involved were discovered by others and the utmost done by him was to invent a practical method of applying them.

There are other systems of wireless telegraphy of later invention than that of Marconi, through a different application of the same principles.

Messages have been sent to enormous distances, far surpa.s.sing the width of the Atlantic, as from Nova Scotia and Ireland to Argentina, a distance of 5,600 miles. Under exceptional conditions a distance of 6,500 miles has been attained, but the daily effective range of the best equipped stations is little over 3,000 miles. For overland messages the limit of distance is about 1,000 miles.

There are a number of kinds of interference which arise from electrical disturbances in the earth's atmosphere. A flash of lightning is liable to give rise to a wave of enormous power which will set half the aerials on the earth vibrating in spite of the differences of pitch to which they are tuned. Thunderstorms are at their worst in the summer in temperate lat.i.tudes, but they occur to some extent all the year round, and those in the tropics are of extreme violence. As a consequence it is frequently almost impossible to decipher earthly messages owing to the imperious signals from the clouds. Of the various methods adopted for choking off the "atmospherics," as the disturbances are called, one is to use receiving circuits which respond only to a narrow range of oscillations very different from those produced by a lightning flash.

The employment of a high-pitched musical note in the telephone is also an advantage because its extreme regularity distinguishes it from the marked irregularity of the stray waves.