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<v Speaker 1>Section twenty five of the Science History of the Universe,

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<v Speaker 1>Volume three. This is a LibriVox recording. All LibriVox recordings

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<v Speaker 1>are in the public domain. For more information or to volunteer,

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<v Speaker 1>please visit LibriVox dot org. The Science History of the Universe,

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<v Speaker 1>Volume three, edited by Francis Rolt Wheeler. Electricity, Chapter seven

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<v Speaker 1>The development of electrochemistry. The striking effects brought about by

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<v Speaker 1>electricity formed the subject of much study about the middle

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<v Speaker 1>of the eighteenth century. At that time, friction electrical machines

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<v Speaker 1>were in use, and in order to intensify the effects produced,

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<v Speaker 1>very large machines were constructed. The most famous of these

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<v Speaker 1>is still to be seen in the Taylor Museum in Harlem.

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<v Speaker 1>Pater Baccaria some one hundred and thirty years ago. By

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<v Speaker 1>using such machines, found that metals could be revivified, that is,

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<v Speaker 1>reduced from their calcis oxides, when the electric spark was

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<v Speaker 1>passed between two pieces. In this way, he obtained zinc

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<v Speaker 1>and mercury. Some time later, Priestley investigated the action of

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<v Speaker 1>the electric spark on air and observed that an acid

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<v Speaker 1>was produced. He mistook this for carbonic acid until Cavendish

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<v Speaker 1>recognized it as nitric acid. Van Marum studied the behavior

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<v Speaker 1>of several other gases in this path of the electric spark,

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<v Speaker 1>which led him to notice the formation of ozone, and

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<v Speaker 1>made experiments also by passing the spark through liquids. Before him,

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<v Speaker 1>Priestley had discovered that in oil and ether, the electric

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<v Speaker 1>spark produces gas, and proved that this gas contained hydrogen.

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<v Speaker 1>The first actual electrolysis was made by Demon and Pates

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<v Speaker 1>von Truswick and Harlem in seventeen eighty nine, in which

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<v Speaker 1>they successfully decomposed water into hydrogen and oxygen. In their experiments,

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<v Speaker 1>the water was contained in a cylindrical tube, closed at

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<v Speaker 1>the top and having a metal wire sealed into its

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<v Speaker 1>upper end. Another metal wire was interduced into the lower

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<v Speaker 1>end of the tube, which dipped into a basin of water.

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<v Speaker 1>When the spark struck through the water, bubbles of gas

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<v Speaker 1>were disengaged from the metal wires and rising in the

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<v Speaker 1>tube gradually displaced the water. As soon as the column

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<v Speaker 1>of water sank below the upper electrode, the gas, which

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<v Speaker 1>was a mixture of hydrogen and oxygen, exploded. This experiment

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<v Speaker 1>was later repeated by Ritter using silver wires and a

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<v Speaker 1>solution of a silver salt, and he observed that the

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<v Speaker 1>negative pole became coated with precipitated silver. On changing the poles,

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<v Speaker 1>silver was dissolved from one and deposited on the other,

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<v Speaker 1>now the negative pole. In Deemon's experiment, oxygen and hydrogen

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<v Speaker 1>were simultaneously formed both at the positive and at the

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<v Speaker 1>negative poles, so that the process was not a true

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<v Speaker 1>electrolytic one like that of Fritters. The whole state of

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<v Speaker 1>the science was changed in a great degree by the

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<v Speaker 1>discoveries of Galvani, and particularly by those of Volta. In

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<v Speaker 1>seventeen ninety five, Volta arranged the metals in a series

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<v Speaker 1>according to the their behavior in galvanic experiments, and in

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<v Speaker 1>seventeen ninety eight Ritter showed that the same series is

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<v Speaker 1>obtained when the properties of the metals to separate other

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<v Speaker 1>metals from their salt solutions are compared. Quote. After the

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<v Speaker 1>introduction of Volta's pile in eighteen hundred, the physiological and

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<v Speaker 1>optical phenomena were less studied quote remarks Spen Aarnius in

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<v Speaker 1>his textbook of Electric Chemistry quote, and more attention was

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<v Speaker 1>paid to the chemical actions as opposed to the electrical machines.

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<v Speaker 1>These piles gave large quantities of electricity at a comparatively

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<v Speaker 1>low potential. Nicholson and Carlisle in eighteen hundred studied the

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<v Speaker 1>evolution of oxygen and hydrogen in salt solutions at immersed

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<v Speaker 1>gold electrodes which were connected with the poles of a

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<v Speaker 1>voltaic pile, and observed that litmis in the neighborhood of

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<v Speaker 1>the positive pole was turned red by the acid produced there.

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<v Speaker 1>Some years later, Davy made his brilliant electrochemical discoveries. He

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<v Speaker 1>succeeded in decomposing the oxides of the alkali and alkaline

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<v Speaker 1>earth metals, which had previously been regarded as elementary substances,

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<v Speaker 1>and in preparing the pure metals. Further progress in obtaining

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<v Speaker 1>the more difficultly reducible metals in this way was later

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<v Speaker 1>made by Bunsen and his pupils. At the time of

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<v Speaker 1>Davy's discovery of the alkali metals, Brasilius was just beginning

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<v Speaker 1>his scientific investigations. In one of the first of these,

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<v Speaker 1>carried out jointly with Hissinger, he studied the action of

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<v Speaker 1>the electric current upon solutions of various inorganic substances, resulting

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<v Speaker 1>chiefly in the establishment of the first electrochemical theory. This

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<v Speaker 1>theory dominated the science of chemistry for many decades. According

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<v Speaker 1>to it, each chemical atom, when in contact with another, possesses,

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<v Speaker 1>like a magnet, an electropositive and an electronegative pole. Moreover,

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<v Speaker 1>one of these poles is usually much stronger than the other. Consequently,

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<v Speaker 1>an atom behaves as if it possessed but one pole,

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<v Speaker 1>either electropositive or electronegative, according as the positive or negative pull, respectively,

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<v Speaker 1>predominates in strength. The magnitude and sign of this resultant

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<v Speaker 1>polarity upon the atoms of a given element determines its

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<v Speaker 1>chemical behavior. If, for instance, the atoms of an element

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<v Speaker 1>are electropositive, it will react with elements whose atoms are electronegative,

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<v Speaker 1>and conversely, during this reaction, the two kinds of electricity

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<v Speaker 1>neutralize each other more or less completely, according to the

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<v Speaker 1>degree of inequality existing between the positive and negative charges

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<v Speaker 1>upon the reacting atoms. If complete neutralization does not take place,

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<v Speaker 1>the resulting compound itself is electropositive or electronegative, according as

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<v Speaker 1>the electropositive are greater or less than the electronegative charges

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<v Speaker 1>upon the component atoms. Compounds which thus possess a resultant polarity,

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<v Speaker 1>may then enter into further combinations with each other in

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<v Speaker 1>such a way as to form a complex compound which

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<v Speaker 1>is more nearly or quite neutral. Thus, the theory explains

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<v Speaker 1>not only the formation of simple compounds from their elements,

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<v Speaker 1>but also the formation of complex compounds such as double salts,

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<v Speaker 1>from their component simple compounds. According to this theory, chemical

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<v Speaker 1>and electrical processes are closely related, and all compounds have

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<v Speaker 1>a dualistic nature, being formed of an electropositive and an

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<v Speaker 1>electronegative component. This theory is therefore known as the electrochemical

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<v Speaker 1>or dualistic theory. It was applied throughout the domain of

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<v Speaker 1>inorganic chemistry, which at that time was practically the entire

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<v Speaker 1>science of chemistry, and although it contained many arbitrary assumptions,

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<v Speaker 1>it performed a great service to science because of its

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<v Speaker 1>systematizing influence. For several decades after the establishment of the

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<v Speaker 1>dualistic theory, no considerable advance was made in electrochemistry. This

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<v Speaker 1>lack of progress was soon counterbalanced by the important discoveries

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<v Speaker 1>which were made by Faraday about the year eighteen thirty five.

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<v Speaker 1>He was the first to show that whether electricity is

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<v Speaker 1>produced by friction or by means of a voltaic pile,

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<v Speaker 1>it is capable of producing the same effects. This fact

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<v Speaker 1>convinced him that there exists but one kind of positive

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<v Speaker 1>and one of negative electricity. He next attempted to discover

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<v Speaker 1>a relation between the quantity of electricity flowing through a

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<v Speaker 1>circuit and the magnitude of the chemical and magnetic effects

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<v Speaker 1>which it could produce. His results may be expressed as follows.

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<v Speaker 1>The magnitude of the chemical and magnetic effects produced in

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<v Speaker 1>a circuit by an electric current is proportional to the

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<v Speaker 1>quantity of electricity which passes through the current. A further

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<v Speaker 1>discovery was made by Faraday by comparing the quantities of

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<v Speaker 1>different substances and solution which are decomposed by the same

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<v Speaker 1>quantity of electricity. This comparison may be made in a

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<v Speaker 1>very simple manner by connecting into one circuit a series

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<v Speaker 1>of solutions of different substances, so that the same quantity

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<v Speaker 1>of electricity passes through each solution. The chemical decomposition produced

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<v Speaker 1>by the electric current in each solution may then be

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<v Speaker 1>ded determined by analysis. Their results obtained may be summarized

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<v Speaker 1>as follows. The quantities of the different substances which separate

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<v Speaker 1>at the electrodes throughout the circuit are directly proportional to

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<v Speaker 1>their equivalent weights, and are independent of the concentration and

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<v Speaker 1>the temperature of the solutions, the size of the electrodes,

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<v Speaker 1>and all other circumstances. Those who first recognized the decomposition

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<v Speaker 1>of water by the electric current sought an explanation for

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<v Speaker 1>the simultaneous appearance of hydrogen at one electrode and of

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<v Speaker 1>oxygen at the other. It was not until eighteen o five, however,

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<v Speaker 1>that a comprehensive theory for this phenomenon was put forward.

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<v Speaker 1>During that year, such a theory was published by Grotus.

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<v Speaker 1>According to this theory, the electric current charges one electrode

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<v Speaker 1>positively and the other negatively, and these charged electrodes then

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<v Speaker 1>exert an electrical influence upon the water molecules. Under this influence,

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<v Speaker 1>the water molecules acquire a polarity, the hydrogen atom becoming

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<v Speaker 1>charged with positive and the oxygen atom with negative electricity.

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<v Speaker 1>The positive electrode then attracts the negatively charged oxygen atom

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<v Speaker 1>and the negative electrode the positively charged hydrogen atom, causing

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<v Speaker 1>the water molecules to arrange themselves in a row or chain.

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<v Speaker 1>As science gradually developed, the imperfections of the theory advanced

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<v Speaker 1>by Grotis became more and more apparent. According to this theory,

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<v Speaker 1>the splitting of the molecule, which is necessary for the

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<v Speaker 1>conduction of electricity, cannot take place until the electromotive force

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<v Speaker 1>is sufficiently great to overcome the affinity or cohesion between

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<v Speaker 1>the two components of a given compound. As a matter

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<v Speaker 1>of fact, however, it was found that under suitable conditions

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<v Speaker 1>of experiment, it is possible to cause an electric current

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<v Speaker 1>to pass through a solution even when the electromotive force

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<v Speaker 1>of the current is extremely small. Clausius was the first

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<v Speaker 1>to direct attention to the disagreement of the Grotis theory

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<v Speaker 1>or conception of all electrolysis with facts. Basing his conclusions

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<v Speaker 1>upon the experimental results already obtained, he declared, quote every

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<v Speaker 1>assumption to be inadmissible which requires the natural condition of

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<v Speaker 1>a solution of an electrolyte to be one of equilibrium,

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<v Speaker 1>in which every positive ion is firmly combined with its

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<v Speaker 1>negative ion, and which at the same time requires the

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<v Speaker 1>action of a definite force in order to change this

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<v Speaker 1>condition of equilibrium, into another, differing from it only in

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<v Speaker 1>that some of the positive ions have combined with other

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<v Speaker 1>negative ions than those with which they were formerly combined.

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<v Speaker 1>Every such assumption is in contradiction to Ohm's law. At

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<v Speaker 1>about the same time that Clausius advanced this theory, Hitchhorf

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<v Speaker 1>began work upon the migration of the ions, and a

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<v Speaker 1>little later coal Rausch commenced experiments upon the electrical conduction

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<v Speaker 1>of solution. The work of these investigators greatly increased the

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<v Speaker 1>knowledge of the process of electrolysis. Making use of their work,

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<v Speaker 1>Ireneus in eighteen eighty seven replaced the theory of vibrating

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<v Speaker 1>ions of Clausius by the theory of free ions. According

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<v Speaker 1>to the material conception of electricity, an ion may be

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<v Speaker 1>considered to be a compound of positive or negative electrons

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<v Speaker 1>with the element in question. The formation of an ion

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<v Speaker 1>is then entirely analogous to the formation of a compound

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<v Speaker 1>from two ordinary elements. For instance, in the formation of

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<v Speaker 1>ions from sodium iodide, the sodium atoms combined with positive

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<v Speaker 1>and the iodine atoms with negative electrons. This conception is

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<v Speaker 1>very comprehensive, for, according to it, the law of electrochemical change.

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<v Speaker 1>Faraday's law appears as a consequence of the laws of

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<v Speaker 1>definite and multiple proportion. Although the theory of electrolytic disassociation

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<v Speaker 1>was not spared great opposition in its early years, it

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<v Speaker 1>has successfully advanced until at the present time, by far

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<v Speaker 1>the greater number of investigators accept it and recognize its value.

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<v Speaker 1>It would be impotois possible to give, in a few

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<v Speaker 1>words a clear conception of all the reasons which led

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<v Speaker 1>Erhnius to adopt his now almost universally accepted views. Unquote,

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<v Speaker 1>says Langbine in his Electrodeposition of metals quote, and a

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<v Speaker 1>short statement of these views must therefore suffice. He discovered that,

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<v Speaker 1>according to the degree of dilution and the nature of

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<v Speaker 1>their combination, salts and aqueous solutions are, to a more

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<v Speaker 1>or less far reaching extent, decomposed into independent portions, that is,

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<v Speaker 1>the ions, and the term electrolytic dissociation is applied to

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<v Speaker 1>this phenomenon. Only combinations which dissociate are decomposed, and thus

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<v Speaker 1>form ions can be conductors of the current, the progressive

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<v Speaker 1>motion of the latter being solely taken care of and

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<v Speaker 1>affected by the ions. The ions are supposed to be

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<v Speaker 1>charged with a certain quantity of electricity, the cathions with

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<v Speaker 1>positive the anions with negative electricity, and so long as

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<v Speaker 1>current passes through to the electrolyte, they move free in

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<v Speaker 1>the latter. However, when a current is conducted through the electrolyte,

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<v Speaker 1>the ions are attracted by the electrodes, the positively charged

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<v Speaker 1>cathions by the negatively charged cathode, and the negatively charged

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<v Speaker 1>anions by the positively charged anode. By reason of these

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<v Speaker 1>movements of the ions to the electrodes, this phenomenon is

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<v Speaker 1>called migration of the ions. The ions, on reaching the

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<v Speaker 1>electrodes are freed of their charge, that is, they yield

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<v Speaker 1>their electricity to the electrodes. They lose thereby their ion nature,

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<v Speaker 1>being transformed by their separation on the electrodes into the

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<v Speaker 1>allotropic or isomeric form of the element or combination. After

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<v Speaker 1>the true action of Volta's pile had been discovered, the

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<v Speaker 1>first modification was to immerse the plates of copper and

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<v Speaker 1>zinc in the liquid. This arrangement gave a more powerful

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<v Speaker 1>and lasting effect than the original pile. Volta arranged the

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<v Speaker 1>cells in a circle and called such a battery a

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<v Speaker 1>crown of cups. In eighteen o six, the Royal Institution

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<v Speaker 1>of London became possessed of a battery of two thousand

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00:14:06.960 --> 00:14:10.879
<v Speaker 1>elements on the trough system. It was with this apparatus

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00:14:10.919 --> 00:14:15.440
<v Speaker 1>that Davy succeeded in decomposing potash and soda. This simple

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<v Speaker 1>type of cell would, however, only work for a short

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<v Speaker 1>time on account of the collection of bubbles of gas

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<v Speaker 1>on the plates. That is, the cells became polarized. Beccarel

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<v Speaker 1>studied this effect and succeeded in overcoming it to a

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<v Speaker 1>great extent in eighteen twenty nine by employing two different

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<v Speaker 1>liquids separated by a porous partition, each of which enclosed

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<v Speaker 1>one of the electrodes. In eighteen sixty three, Professor Daniel

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<v Speaker 1>invented the cell known by his name, and which is

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<v Speaker 1>one of the most constant current cells ever made, although

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<v Speaker 1>not so powerful as some. The zinc and copper electrodes

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00:14:50.919 --> 00:14:54.399
<v Speaker 1>are here separated by a jar of porous earthenware, the

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<v Speaker 1>zinc being surrounded by dilute sulphuric acid, and the copper

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<v Speaker 1>by a saturated solution of sulfates copper. This latter solution

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<v Speaker 1>is the depolarizer, acting to prevent the bubbles of hydrogen

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<v Speaker 1>from collecting on the copper plate, as would be the

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<v Speaker 1>case in the simple cell. Instead of hydrogen being thrown

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<v Speaker 1>out at the copper pole, copper is deposited from the

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00:15:15.159 --> 00:15:19.480
<v Speaker 1>sulfate of copper depolarizer, so that this solution becomes constantly

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<v Speaker 1>weaker and the copper heavier. To prevent the weakening, sulfate

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<v Speaker 1>crystals are added Occasionally. This battery has been much employed

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<v Speaker 1>in telegraphic work. A form of this cell, known as

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<v Speaker 1>the gravity cell, has been much used for this purpose,

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<v Speaker 1>the porous partition having here been done away with, and

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<v Speaker 1>the separation of the liquids affected by the difference in

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00:15:40.559 --> 00:15:45.080
<v Speaker 1>their densities. In eighteen thirty nine, Grove introduced a cell

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<v Speaker 1>in which the depolarizer was strong nitric acid, which surrounded

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<v Speaker 1>a platinum plate. This is a much more powerful depolarizer

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<v Speaker 1>than sulfate of copper, and the cell was very energetic.

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<v Speaker 1>It had, however, the disadvantage of high cost and gave

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<v Speaker 1>off disagreeable fumes. The first drawback was overcome by Professor

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<v Speaker 1>Bunsen in eighteen forty three, who substituted for the platinum

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<v Speaker 1>plate one of gas retort carbon. The fumes however, still remained.

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<v Speaker 1>This battery was useful to the early experimenters as it

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<v Speaker 1>furnished a strong and constant current. Another good depolarizer is

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<v Speaker 1>chromic acid. This is used in the same manner as

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<v Speaker 1>nitric acid in the carbon zinc cell of Bunsen. It

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<v Speaker 1>does not, however, give off fumes, and yet is almost

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<v Speaker 1>as powerful as the Bunsen cell. Various forms of this

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00:16:34.960 --> 00:16:37.480
<v Speaker 1>cell have been made, and they have been extensively used,

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<v Speaker 1>especially for telephone work. They deteriorate only slightly on standing.

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<v Speaker 1>Perhaps the most extensively used primary cell is the laclants.

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<v Speaker 1>This is also a zinc carbon cell, but cell ammoniac

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<v Speaker 1>is used to replace the sulphuric acid of the preceding cells,

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<v Speaker 1>and the depolarizer is the black oxide of manganese. This

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<v Speaker 1>depolarizer is celow in its action, and the cell is

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<v Speaker 1>therefore not good for constant current work, but it has

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<v Speaker 1>a very slow rate of deterioration. This cell is very

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<v Speaker 1>extensively manufactured in the dry form, in which the exciting

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<v Speaker 1>fluid is held as a moist paste. The cell is

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<v Speaker 1>not entirely dry, however, as is sometimes supposed, for if

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<v Speaker 1>it dries out, it ceases to work. One of the

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<v Speaker 1>most recent primary cells, as well as the best, is

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<v Speaker 1>the zinc copper oxide cell of the land. In the

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<v Speaker 1>Edison form of this cell, the copper oxide is pressed

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<v Speaker 1>into plates and mounted in the cell between two zinc plates.

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<v Speaker 1>The exciting fluid is caustic potash. The copper oxide acts

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<v Speaker 1>as the depolarizer and is reduced to metallic copper. The

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<v Speaker 1>cell is very efficient, has a long life, and does

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<v Speaker 1>not deteriorate on standing. Thousands are now in use for

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<v Speaker 1>such work as operating railway signals, sparking gas engines, et cetera.

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<v Speaker 1>The existence of secondary currents was discovered by Ritter in

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<v Speaker 1>eighteen o three, having substituted to the actions of a

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<v Speaker 1>volta's pile another pile formed only of discs of copper

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<v Speaker 1>separated by moist cloth. He remarked that this second pile,

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<v Speaker 1>though enacted by itself, gave in its turn an electric

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<v Speaker 1>current in the opposite direction to the current of the

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<v Speaker 1>first pile. This current was of but short duration, and

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<v Speaker 1>the electromotive force was lower than that of the pile

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<v Speaker 1>used in charging it. In eighteen twenty six, De la

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<v Speaker 1>Revee also found that a secondary or inverse current could

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<v Speaker 1>be obtained from plates of platinum upon which oxygen and

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00:18:32.599 --> 00:18:36.200
<v Speaker 1>hydrogen had been disengaged in the experiment of the decomposition

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<v Speaker 1>of water by a battery. This phenomenon took the name

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<v Speaker 1>of polarization of the electrodes, and the current itself that

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<v Speaker 1>of the current of polarization. After that, secondary currents were

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<v Speaker 1>the object of many researches made by physicists, among whom

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<v Speaker 1>many may be mentioned Faraday, Grove, Wheatstone, Pogendwarf E. Becquerel,

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<v Speaker 1>and Gaugene. In eighteen fifty nine, gastone Plant studied the

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<v Speaker 1>influence of different metals and different liquids on the production

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<v Speaker 1>of secondary currents and on their intensity. Since that date,

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<v Speaker 1>the question has assumed great importance, having received scientific and

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<v Speaker 1>practical applications, due mainly to the researches of this acute observer.

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<v Speaker 1>He experimented on voltameters with wires of copper, silver, tin, aluminium, iron, zinc, gold,

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<v Speaker 1>and platinum, and for each of them varied the nature

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00:19:28.039 --> 00:19:31.519
<v Speaker 1>of the liquid into which the electrodes were placed. He

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<v Speaker 1>found that quote all the metals oxidizing at the positive

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00:19:35.319 --> 00:19:38.799
<v Speaker 1>pole of the cell, the secondary current obtained after the

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<v Speaker 1>interruption of the primary current was as much more intense

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<v Speaker 1>as the oxidation was more complete if the oxide form

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<v Speaker 1>remained adherent and insoluble in the ascidulated liquid of the voltameter.

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<v Speaker 1>Even gold and silver did not resist the action of

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<v Speaker 1>the oxygen of the pile. They were covered with dark

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<v Speaker 1>deposits of oxide and furnished an energetic secondary current. Platinum

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<v Speaker 1>did not oxidize, it is true in a visible manner,

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<v Speaker 1>but the secondary inverse current was of shorter duration than

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<v Speaker 1>that of the metals which were covered with a layer

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<v Speaker 1>of adherent oxide, an effect which was explained by the

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<v Speaker 1>rapid decomposition of the oxygenated water produced around the positive

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<v Speaker 1>electrode of the voltameter. The action of the hydrogen was,

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<v Speaker 1>on the other hand, stronger with platinum than with all

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<v Speaker 1>the other metals, for the electrode around which this gas

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<v Speaker 1>was disengaged furnished with another neutral electrode a more intense

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<v Speaker 1>secondary current than when any other metal was employed. The

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<v Speaker 1>most important result of these interesting researches is that which

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<v Speaker 1>assigns the greatest intensity to this secondary current produced by

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<v Speaker 1>a voltameter with electrodes of lead and dilute sulphuric acid

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<v Speaker 1>as the liquid. Measuring the electromode of forest developed in

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<v Speaker 1>such a voltameter after the rupture of the primary current,

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00:20:57.160 --> 00:20:59.759
<v Speaker 1>plot found it was equal to about one and a

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<v Speaker 1>half half times more exactly one point four eight to

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<v Speaker 1>one point four nine that of the most energetic voltaic element,

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<v Speaker 1>such as a grove or bunsen. This suggested the idea

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<v Speaker 1>of constructing secondary cells and uniting them in a battery

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<v Speaker 1>so as to store up or accumulate the work of

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00:21:17.599 --> 00:21:21.519
<v Speaker 1>the voltaic pile, in the same way that static electricity

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<v Speaker 1>is condensed by the aid of conductors of great surface

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00:21:25.039 --> 00:21:29.240
<v Speaker 1>separated by an insulating material. The action in a storage

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00:21:29.279 --> 00:21:32.440
<v Speaker 1>cell is as follows. When the battery is charged, the

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00:21:32.480 --> 00:21:36.000
<v Speaker 1>positive plate consists of lead peroxide and the negative of

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00:21:36.079 --> 00:21:40.160
<v Speaker 1>pure lead in a spongy condition. When the cell discharges,

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00:21:40.359 --> 00:21:44.079
<v Speaker 1>both plates become a form of lead sulfate. Upon being

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<v Speaker 1>charged by having a reverse current sent through them, they

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00:21:47.200 --> 00:21:51.640
<v Speaker 1>are reformed into lead peroxide and sponge lead. If the

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<v Speaker 1>plates were platinum, oxygen would be given off where the

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<v Speaker 1>current enters and hydrogen were it leaves, but with the

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<v Speaker 1>lead sulfate plates, the oxygen and hydrogen combine thus oxidizing

347
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<v Speaker 1>one and reducing the other. Storage cells have many uses.

348
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<v Speaker 1>They are employed in large sizes and central power stations

349
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<v Speaker 1>to equalize the load on the machinery, serving to help

350
00:22:14.359 --> 00:22:17.119
<v Speaker 1>the engines carry the maximum loads so that they are

351
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<v Speaker 1>not strained. Electric automobiles are largely used, but the weight

352
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<v Speaker 1>of the battery seriously handicaps their other excellent qualities. They

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<v Speaker 1>also find application in lighting trains, operating industrial locomotives, supplying

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<v Speaker 1>telephone lines, and igniting gas engines. End of Section twenty

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<v Speaker 1>five Electricity, Chapter seven