Latest / History of the Universe Physics & Electricity Vol. 3 / 023 - Electricity - Chapter 6 - History of Electric Lighting Part 1

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023 - Electricity - Chapter 6 - History of Electric Lighting Part 1 · History of the Universe Physics & Electricity Vol. 3

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Speaker 1: Section twenty three of the Science History of the Universe,
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Speaker 1: Volume three. This is a LibriVox recording. All LibriVox recordings
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Speaker 1: in the public domain. For more information or to volunteer,
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Speaker 1: please visit LibriVox dot org. Recording by Marianne The Science
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Speaker 1: History of the Universe, Volume three, edited by Francis Rold Wheeler. Electricity,
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Speaker 1: Chapter six, The History of electric lighting, Part one. The
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Speaker 1: history of electric lighting begins soon after the discovery of
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Speaker 1: electric currents in eighteen hundred. Sir Humphrey Davy, while experimenting
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Speaker 1: with the effects of currents, obtained bright sparks between two
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Speaker 1: charcoal points upon breaking the contact between them. The number
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Speaker 1: of cells with which he worked was, however, insufficient to
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Speaker 1: produce a continuous light. After a few years, he increased
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Speaker 1: the number of cells in his battery until it was
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Speaker 1: composed of two thousand elements. With this powerful source of current,
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Speaker 1: he was able to obtain a continuous distric charge between
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Speaker 1: the carbon points, which sustained itself across a gap of
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Speaker 1: seven inches and emitted a dazzling light. This light was
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Speaker 1: exhibited in eighteen thirteen at the Royal Institution. Davy found
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Speaker 1: that the conducting power of the charcoal points was improved
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Speaker 1: by extinguishing the charcoal under mercury. The consumption of these
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Speaker 1: points was very rapid. The name voltaic arc came from
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Speaker 1: this experiment of Davies, from the fact that the stream
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Speaker 1: of vapor formed itself into a bow, the charcoal points
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Speaker 1: being horizontal. Owing to the high cost of producing the
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Speaker 1: electric current, no one seems to have cared either to
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Speaker 1: develop a lamp or to ascertain the properties of the
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Speaker 1: arc itself until eighteen forty four, when Foucault constructed a
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Speaker 1: lamp using carbons from the retorts of gas works, which
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Speaker 1: were much harder and more compact than Davy's charcoal points,
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Speaker 1: and less easily consumed. Thomas Wright of London devised the
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Speaker 1: first apparatus eighteen forty five, in which the use adjustment
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Speaker 1: of the carbons is brought about automatically. Wc Straight used
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Speaker 1: the electric current for the regulation of the carbons in
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Speaker 1: eighteen forty eight. In eighteen fifty eight, Foucault devised a
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Speaker 1: lamp in which the carbons were made to approach automatically
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Speaker 1: by means of a clockwork feed, the clockwork being controlled
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Speaker 1: by an electromagnet. As the current diminished in strength due
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Speaker 1: to the increase in the length of the arc. As
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Speaker 1: the carbons burned away, a magnet in series with the
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Speaker 1: arc weakened and released the escapement of the clockwork, thus
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Speaker 1: moving the carbons together. In this lamp, both carbons moved
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Speaker 1: and were so regulated in their motions as to maintain
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Speaker 1: the arc in a fixed position. In later lamps used
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Speaker 1: for general illumination, this was not considered necessary and the
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Speaker 1: regulating mechanism was considerably simplified. The lamps were known as
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Speaker 1: focusing or self centering lamps, and are still necessary in
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Speaker 1: some cases, such as stereoopticon work. Before proceeding with the history,
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Speaker 1: some of the properties of the arc may be examined.
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Speaker 1: If it is attempted to produce an arc by means
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Speaker 1: of a few cells of battery, the attempt will be unsuccessful.
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Speaker 1: It is necessary that a difference of potential of about
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Speaker 1: forty volts should exist between the carbons before any stream
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Speaker 1: of vapor will be formed. The longer the arc produced,
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Speaker 1: the higher is the voltage necessary to maintain it. In
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Speaker 1: the ordinary carbon lamp, practically no light comes from the
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Speaker 1: arc itself. It is all emitted from the white hot
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Speaker 1: carbon points. If the source of current is direct or continuous.
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Speaker 1: Most of the light is radiated from the positive carbon
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Speaker 1: or that by which the current enters, and this carbon
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Speaker 1: is consumed about twice as rapidly as the other. From
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Speaker 1: this fact, it will be seen that in such lamps
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Speaker 1: as vocults, it was necessary to arrange the mechanism so
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Speaker 1: that the positive carbon should move at about twice the
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Speaker 1: rate of the negative. Another peculiarity is the manner in
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Speaker 1: which the carbon points burn away when the combustion takes
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Speaker 1: place in the air. The positive carbon has a depress
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Speaker 1: or crater formed in it, and upon the negative is
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Speaker 1: produced a nib. This seems to be due entirely to
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Speaker 1: the fact that combustion takes place in air, as the
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Speaker 1: phenomenon disappears when the arc is enclosed and both carbons
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Speaker 1: become blunt. This seemingly slight difference was, however, a factor
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Speaker 1: of considerable consequence, as the greater part of the light
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Speaker 1: is emitted from the intensely hot crater of the positive carbon,
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Speaker 1: so that in the open arc much of the light
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Speaker 1: is cut off from the horizontal direction by the rim
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Speaker 1: of the crater, which is removed by enclosing the arc.
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Speaker 1: The temperature of the arc is the greatest of all
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Speaker 1: earthly temperatures, nearly all substances, volatizing almost instantly. Our clamp
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Speaker 1: development was stimulated by the construction of the magneto electric machine,
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Speaker 1: which greatly decreased the cost of power. The introduction of
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Speaker 1: the dynamo, however, completely solved the problem of power, and
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Speaker 1: the field was immediately opened for the electric light. One
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Speaker 1: of the first successful lights was the electric candle of
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Speaker 1: Paul Jablokov, invented in eighteen seventy six. This is probably
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Speaker 1: the simplest of all electric lamps, as shown of Fig.
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Speaker 1: Twenty two. It consists of two carbon rods placed parallel
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Speaker 1: and separated from each other by plaster of paris, the
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Speaker 1: rods having brass tubes at their lower ends which make
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Speaker 1: contact with springs set in the holding device. To start
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Speaker 1: the candle, a thin plate of graphite was laid across
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Speaker 1: the tip, this being heated by the passage of the
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Speaker 1: current sufficiently to start the arc. Difficulty was of course
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Speaker 1: encountered in operating these lamps un direct current, on account
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Speaker 1: of the unequal rates of burning of the positive and
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Speaker 1: negative carbons. It was attempted to overcome this by making
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Speaker 1: the positives twice as thick as the negative carbon, but
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Speaker 1: the ratio not being exact and libel to variation caused
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Speaker 1: the failure of this method. They were therefore operated on
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Speaker 1: alternating current, and over four thousand were used in Paris alone.
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Speaker 1: The lamps, however, were not satisfactory, and inventors gradually reverted
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Speaker 1: to the lamp with the adjustable mechanism. As soon as
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Speaker 1: arc lamps had to be operated over considerable territory, it
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Speaker 1: was seen that the mode of connection, known as a series,
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Speaker 1: wherein a single wire is used to connect the lamps together,
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Speaker 1: was preferable to the parallel system, which required two wires,
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Speaker 1: both in economy of wire and in saving of power.
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Speaker 1: This required a special arrangement of the lamp mechanism. On
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Speaker 1: the series system, the same current passes through each lamp,
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Speaker 1: and since it requires about fifty volts to operate a lamp,
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Speaker 1: the generator must develop as many times fifty volts as
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Speaker 1: there are lamps. This necessitated the construction of a generator
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Speaker 1: which should develop a high voltage, as there were often
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Speaker 1: as many as one hundred and twenty five lamps on
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Speaker 1: one line, requiring one hundred and twenty five times fifty
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Speaker 1: or six thousand, two hundred fifty volts. Such a suitable
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Speaker 1: generator was devised by mister Charles Brush and is known
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Speaker 1: as the Brush arc lighting Diye. Returning to the mechanism
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Speaker 1: of the lamps suitable for such a current, one of
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Speaker 1: the first of these was constructed by Hefner Alternach and
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Speaker 1: is known as the Siemens differential lamp. This type of
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Speaker 1: regulator is still in use, although of course modified and improved. Fig.
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Speaker 1: Twenty four illustrates the method of regulating. The lower solenoid
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Speaker 1: r is known as the series coil and carries the
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Speaker 1: same current that passes through the arc. The upper solenoid
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Speaker 1: tea has many turns of fine wire and is connected
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Speaker 1: across the arc. The two coils act upon the same
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Speaker 1: core in opposite directions, hence the name differential. If the
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Speaker 1: carbons approach too closely, the current in the series coil
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Speaker 1: increases and pulls them apart. But as the length of
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Speaker 1: the ark is increased, thereby the voltage across it grows
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Speaker 1: greater and the shunt coil TEA receives more current. This
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Speaker 1: prevents the series coil from producing too great emotion, and
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Speaker 1: the carbons are held by the balancing action of the
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Speaker 1: two coils. The upper carbon alone is fed down by
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Speaker 1: the action of gravity, the lower carbon being fixed. This
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Speaker 1: style of lamp was also developed by Brush in America,
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Speaker 1: and many thousands had been used. The combination of the
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Speaker 1: brush high voltage generator and the differential series lamp was
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Speaker 1: quite satisfactory as a means of lighting, and many of
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Speaker 1: these arrangements are in use at the present time, although
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Speaker 1: they are fast being replaced by more modern systems. With
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Speaker 1: the open arc lamp of the Brush type, the replacement
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Speaker 1: of the carbons was required daily and became quite an
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Speaker 1: item in the total expense of operation. About fifteen years ago,
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Speaker 1: arcs enclosed by a thin glass were introduced, which required
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Speaker 1: trimming only once in ten or fifteen days. At first,
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Speaker 1: it was thought that the enclosing glass would cut off
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Speaker 1: so much of the light as to seriously impair the
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Speaker 1: efficiency of the lamp. The fact previously mentioned concerning the
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Speaker 1: flattening of the carbon tips and a consequent better distribution
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Speaker 1: of the light here came to the aid of the
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Speaker 1: enclosed lamp, so that although there was some loss of
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Speaker 1: light due to the glass, the improved distribution overbalanced that effect.
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Speaker 1: A grave fault, however, was the disposition of the silicious
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Speaker 1: impurities of the carbons on the enclosing glass, with a
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Speaker 1: consequent diminution in light. Efforts were accordingly directed towards the
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Speaker 1: improvement of the carbons, and although it had not been
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Speaker 1: found possible to produce carbons free from such material, that
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Speaker 1: fault is not at the present time serious. Although the
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Speaker 1: series system in operation is the only practicable one over
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Speaker 1: long distances, it is often required to operate arc and
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Speaker 1: incandescent lamps on the same circuit, as in buildings, et cetera.
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Speaker 1: For such work, the differential mechanism of the series systems
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Speaker 1: is not suitable. In that system. The lamps act to
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Speaker 1: steady one another, for with so many in the circuit,
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Speaker 1: the fluctuations of one lamp do not appreciably affect the
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Speaker 1: current in the circuit. The operation of a single lamp requires, therefore,
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Speaker 1: something to replace the steadying action of the other arcs,
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Speaker 1: and this is accomplished by means of a dead resistance.
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Speaker 1: Some energy is of course wasted in this resistance, about
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Speaker 1: twenty five percent, but the operation is very satisfactory. An
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Speaker 1: ordinary carbon arc lamp, although one of our most efficient
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Speaker 1: sources of light is still far from the ideal. Of
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Speaker 1: the total energy radiated from it, only about ten percent
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Speaker 1: has the proper frequency of vibration to affect the eye
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Speaker 1: as light. The ideal light would emit rays, all of
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Speaker 1: which would affect the eye. One means of affecting this
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Speaker 1: increase is to raise the temperature of the heated body,
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Speaker 1: another to employ a different material. Since all materials do
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Speaker 1: not emit equal light at the same temperature, Attempts to
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Speaker 1: utilize the latter principle resulted in the production of luminous
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Speaker 1: and flaming arcs. Some of the most prominent workers on
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Speaker 1: the subject are Bremmer, our nerdst. Blondel, Whitney, and Steimets.
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Speaker 1: The luminous arc is composed of two electro which supply
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Speaker 1: a stream of light giving vapor. One of the most
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Speaker 1: prominent examples of this type is that developed by mister
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Speaker 1: Steinmeants and known as the magnetic arc. The positive electrode
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Speaker 1: is a rod of copper, the negative a rod of
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Speaker 1: magnetite or iron ore. The light given off is an
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Speaker 1: intense greenish white, the efficiency being several times that of
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Speaker 1: the ordinary arc. They have recently been established on a
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Speaker 1: commercially operative basis, although still unsatisfactory in some respects. They
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Speaker 1: can operate only on direct current, which usually involves the
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Speaker 1: rectification of the alternating current. Now almost universally generated. The
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Speaker 1: flaming arc is almost invariably produced by utilizing the intense
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Speaker 1: heat of the carbon arc to render incandescent various refractory materials.
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Speaker 1: For this purpose, either one or both of the carbons
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Speaker 1: are impregnated with metallic salts having great light giving power
11:55
Speaker 1: as calcium, titanium, strontium, et cetera. The most efficient of
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Speaker 1: these are the salts of calcium, which emit dazzling yellow rays.
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Speaker 1: For some purposes as interior lighting, these rays are objectionable
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Speaker 1: on account of the distortion of color which they produce,
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Speaker 1: and the salts of titanium are preferred as these emit
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Speaker 1: a beautiful white light, although of less intensity. The lamps
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Speaker 1: may be operated on either direct or alternating current. The
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Speaker 1: objectionable features of these lamps are the increased cost of
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Speaker 1: the carbons and their short life. For that reason, they
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Speaker 1: have not yet come into general use for street lighting.
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Speaker 1: In respect of life, the magnetic arc has the advantage
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Speaker 1: its life being about the same as the enclosed carbon
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Speaker 1: arc one hundred and fifty hours. Developments in arc lighting
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Speaker 1: have followed one another with such rapidity during the last
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Speaker 1: seven or eight years, and are still progressing so swiftly
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Speaker 1: that one hardly knows where they will stop. The fine
12:51
Speaker 1: organizations of engineering and scientific skill under the control of
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Speaker 1: large electrical enterprises, have made possible these rapid developments of
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Speaker 1: the last few years. Admirable as is the system of
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Speaker 1: electric arc lighting for use in streets and open spaces
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Speaker 1: and in workshops or large halls. Says Henry Morton in
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Speaker 1: his Electricity in lighting, it is entirely unfit to take
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Speaker 1: the place of numerous lights of moderate intensity employed for
13:16
Speaker 1: general domestic illumination. For this purpose, it was at a
13:20
Speaker 1: very early period perceived that the incandescence, or heating to
13:24
Speaker 1: luminosity of a continuous conductor by an electric current was
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Speaker 1: the most promising method. It was also, at a very
13:32
Speaker 1: early period perceived that the conductor to be used for
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Speaker 1: this purpose must be one which would admit of being
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Speaker 1: raised to a very high temperature without being melted or
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Speaker 1: otherwise destroyed. The first material which was thought of in
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Speaker 1: this connection was platinum, or one of its allied metals.
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Speaker 1: Such as iridium, which had the highest melting points among
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Speaker 1: such bodies, and are besides entirely unacted upon by the
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Speaker 1: air at all temperatures. In eighteen forty eight W. E.
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Speaker 1: Strait took out a patent for making electric lamps of
14:01
Speaker 1: iridium or iridium alloys shaped into an arc or horseshoe form.
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Speaker 1: One of the most serious difficulties, however, even with these materials,
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Speaker 1: was that to secure from them an efficient light, it
14:13
Speaker 1: was necessary to bring them so near to their fusing
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Speaker 1: points that a very minute increase in the current would
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Speaker 1: carry the temperature beyond this and destroy the lamp by
14:21
Speaker 1: fusing the conductor. An escape from the difficulty was offered
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Speaker 1: by the use of hard carbon, such as that employed
14:28
Speaker 1: for the electrodes of arc lamps. But here the compensating
14:31
Speaker 1: drawback was encountered in that this substance, when highly heated,
14:35
Speaker 1: was attacked by the oxygen of the air, or in
14:37
Speaker 1: other words, burned. To meet this, plans were devised for
14:42
Speaker 1: the replacement of the consumed carbon in a non active
14:45
Speaker 1: gas or in a vacuum. Thus, in eighteen forty five
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Speaker 1: a patent was taken out in England by Augustus King,
14:53
Speaker 1: acting as an agent for an American inventor named J. W.
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Speaker 1: Starr for an incandescent lamp, the important parts of which
15:00
Speaker 1: which are representative Fig. Twenty three. Here, a platinum wire
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Speaker 1: is sealed through the top of a small glass chamber
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Speaker 1: constituting the upper end of a barometer tube. This platinum
15:11
Speaker 1: wire carries at its power end a clamp which grasps
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Speaker 1: a thin plate or rod of carbon, and also a
15:18
Speaker 1: non conducting vertical rod or support which helps to sustain
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Speaker 1: another clamp which grasps the lower end of the carbon
15:25
Speaker 1: strip and connects it by a wire with the mercury
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Speaker 1: in the barometer tube below. By passing a current through
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Speaker 1: the platinum wire and thence through the upper clamp carbon strip,
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Speaker 1: lower clamp wire and mercury, the carbon strip could be
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Speaker 1: made incandescent and was to a certain extent protected by
15:43
Speaker 1: the surrounding vacuum. Though this lamp produced a brilliant light,
15:47
Speaker 1: it proved in various respects unsatisfactory and was abandoned after
15:50
Speaker 1: numerous trials. Other inventors, as for example, Kuhn of Saint Petersburg,
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Speaker 1: continued to work with rods or pencils of hard carbs
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Speaker 1: and achieved a limited success, but the irregularity and brittleness
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Speaker 1: of the material seemed to have been an insuperable objection
16:06
Speaker 1: in drawback, and the problem of commercial electric lighting by
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Speaker 1: incandescent conductors yet remained without solution. This was the state
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Speaker 1: of affairs even up to the fall of eighteen seventy eight, when,
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Speaker 1: as is claimed, William E. Sawyer, in combination with albun Man,
16:24
Speaker 1: after many preliminary experiments, produced their first successful incandescent lamp
16:28
Speaker 1: with an arc shaped conductor made of carbonized paper. In
16:32
Speaker 1: their application for a patent while January eighth, eighteen eighty nine,
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Speaker 1: these inventors used the following remarkable language in their fourth claim,
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Speaker 1: an incandescing arc of carbonized fibrous or textile material. This
16:47
Speaker 1: indicates that they realized the importance of what seemed to
16:49
Speaker 1: be the common features of the present incandescent lamps, namely
16:53
Speaker 1: the arc or arch or bow or loop form and
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Speaker 1: the carbonized fibrous or textile material. They also specially refer
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Speaker 1: to carbon incandescent conductors made from paper. After a long
17:06
Speaker 1: and hotly contested interference, the United States Patent Office has
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Speaker 1: granted them a patent in which these points are broadly
17:12
Speaker 1: stated the lamp brought out by Messrs Sawyer and Man
17:16
Speaker 1: soon after their application for a patent, and described and
17:20
Speaker 1: shown in that application, was a rather large and complicated structure,
17:24
Speaker 1: and had no improvement and simplication of this structure been made,
17:28
Speaker 1: the present immense development in electric lighting would no doubt
17:31
Speaker 1: have been unattained. It is to t A Edison without
17:34
Speaker 1: doubt that we owe many of the simplifications and modifications which,
17:39
Speaker 1: by cheapening the lamp and diminishing its weight, have extended
17:42
Speaker 1: its range of use and its usefulness to a remarkable degree.
17:47
Speaker 1: On his return in the fall of eighteen seventy eight
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Speaker 1: from the far West, where he had gone in company
17:51
Speaker 1: with doctor and Missus Henry Draper, Doctor George P. Barker,
17:55
Speaker 1: and the present writer to observe the total solar eclipse
17:58
Speaker 1: of that year, mister Edison visits to the shops and
18:00
Speaker 1: laboratory of William Wallace at Ansonia, Connecticut, where many experiments
18:06
Speaker 1: with electric arc lights and dynamo machines were in progress,
18:09
Speaker 1: and while studying these, was impressed with the desirability of
18:13
Speaker 1: producing an incandescent electric lamp. Like so many before him,
18:18
Speaker 1: he first turned to platinum and platinum alloys and devised
18:21
Speaker 1: a form of lamp admirable for its simplicity, but unfortunately
18:24
Speaker 1: open to fatal objection. This first lamp of Edison's is
18:28
Speaker 1: shown in Fig. Twenty five, in which A B is
18:31
Speaker 1: the incandescent platinum wire. The announcement of a new system
18:35
Speaker 1: of electric lighting, made by mister Edison and his friends
18:38
Speaker 1: on the foundation of this device, attracted universal attention and
18:42
Speaker 1: even caused a serious fall in the value of gas
18:45
Speaker 1: stocks in the country and abroad. It is indeed amusing
18:49
Speaker 1: now to look back upon the extravagant assertions and predictions
18:52
Speaker 1: made at that time and widely circulated, when we realize
18:55
Speaker 1: how more than frail was their foundation. In fact, mister
18:59
Speaker 1: Edisison very soon found out that this simple device was
19:02
Speaker 1: entirely insufficient for the purpose proposed, because the heated platinum
19:06
Speaker 1: wire gradually stretched by his own weight, and thus was
19:09
Speaker 1: constantly getting out of adjustment and finally would become attenuated
19:12
Speaker 1: and break. It also happened that though the secret of
19:17
Speaker 1: this great invention was carefully guarded, some inkling of it escaped,
19:21
Speaker 1: and this enabled those who were familiar with such subjects
19:24
Speaker 1: to perceive the close similarity between This Edison lamp and
19:27
Speaker 1: a similar device constructed and used by doctor J. W.
19:30
Speaker 1: Draper prior to eighteen forty seven, and described and figured
19:33
Speaker 1: in articles published by him during that year in the
19:36
Speaker 1: American Journal of Science and Arts, the London, Edinburgh and
19:40
Speaker 1: Dublin Philosophical Magazine, and Harper's New Monthly Magazine. The sepparatus
19:46
Speaker 1: was used by doctor Draper as a source of light
19:48
Speaker 1: or lamp with which he determined the relations between temperature
19:52
Speaker 1: and luminosity. At the conclusion of this article, doctor Draper says,
19:56
Speaker 1: an ingenious artist would have very little difficulty by taking
19:59
Speaker 1: advantage of the movie of the lever, in making self
20:01
Speaker 1: acting apparatus in which the platinum should be maintained at
20:05
Speaker 1: a uniform temperature, notwithstanding any change taking place in the
20:08
Speaker 1: voltaic current. It also appeared that precisely the same idea
20:13
Speaker 1: had occurred to another inventor, Hiram S. Maxim, who has
20:16
Speaker 1: recently developed such marvelous improvements in magazine or repeating guns,
20:21
Speaker 1: and who on December twenty second, eighteen seventy nine, filed
20:25
Speaker 1: an application for a patent, which, after an interference litigation
20:28
Speaker 1: with Edison, was finally issued to Maxim. On September twentieth,
20:32
Speaker 1: eighteen eighty one, for the form of electric lamp shown
20:35
Speaker 1: in Fig. Twenty six. It has also been shown that
20:39
Speaker 1: in eighteen fifty eight M. G. Farmer, one of the
20:41
Speaker 1: veteran electricians of America, to whose work in connection with
20:44
Speaker 1: the Dynamo electric machine allusion has been made before, lighted
20:49
Speaker 1: a room in his house at Salem, Massachusetts, for several
20:51
Speaker 1: months with platinum lamps of similar structure controlled by automatic regulators.
20:57
Speaker 1: During eighteen seventy eight and eighteen seventy nine, however, mister
21:00
Speaker 1: Edison was most diligently at work, and perceiving the imperfections
21:04
Speaker 1: of his first ideas, sought in every way to overcome them.
21:07
Speaker 1: It thus came to pass that by December twenty first,
21:09
Speaker 1: eighteen seventy nine, at which date he made his first
21:12
Speaker 1: revelation to the public in the pages of the New
21:14
Speaker 1: York Herald, he had perfected a platinum lamp which is
21:17
Speaker 1: shown in outline in Fig. Twenty seven, as well as
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Speaker 1: some other forms substantially like it. But these platinum conductor
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Speaker 1: lamps were not the only outcome of mister Edison's work.
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Speaker 1: Between the fall of eighteen seventy eight, and December eighteen
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Speaker 1: seventy nine. As this herald article related, mister Edison, like
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Speaker 1: many before him, having experienced the insuperable difficulties present in
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Speaker 1: metallic conductors, had turned his attention to carbon in various forms, and,
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Speaker 1: like Sawyer and Man, had found fibrous textile materials when carbonized,
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Speaker 1: to be most convenient, and paper especially to be in
21:50
Speaker 1: the first instance, the most available substance. Like Sawyer and Man,
21:55
Speaker 1: he had also found the arc or horseshoe form to
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Speaker 1: be the most desirable. Though working with the same materials
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Speaker 1: and form, Edison produced a structure very different in appearance
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Speaker 1: from that of Sawyer and Man, as will be seen
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Speaker 1: by a reference to Fig. Twenty eight, which represents one
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Speaker 1: of Edison's paper carbon lamps, which was the first one
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Speaker 1: whose electric properties were accurately measured, these measurements having been
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Speaker 1: made at the Stephens Institute of Technology early in eighteen
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Speaker 1: eighty by the present writer, acting in his capacity as
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Speaker 1: Chairman of the Committee on Scientific Tests of the United
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Speaker 1: States Lighthouse Board, that body, desiring information as to this
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Speaker 1: new light, and deputing the work of investigation to this committee.
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Speaker 1: In this lamp, the carbon conductor is supported on platinum
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Speaker 1: wires and held in minute platinum clamps at the ends
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Speaker 1: of these wires, which are sealed through the walls of
22:45
Speaker 1: the pear shaped enclosing tube in a manner which has
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Speaker 1: been familiar for twenty years in the construction of the
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Speaker 1: beautiful toys known as Geisler tubes. The interior of this
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Speaker 1: glass vessel has likewise been exhausted and hermeneutically sealed in
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Speaker 1: the manner usual with many Geisler tubes and with the
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Speaker 1: radiometers of doctor William Crooks. Since its invention, the Edison
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Speaker 1: lamp has maintained a practical monopoly, and it is only
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Speaker 1: within the last few years that other competitors have loomed
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Speaker 1: up which threaten its supremacy. They still have difficulties to surmount, however,
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Speaker 1: which have already been overcome in the carbon filament lamp
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Speaker 1: end A Section twenty three