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ELEMENTS

ELECTRICITY

AND

ELECTRO-C H E MISTR Y.

By GEORGE JOHN SINGER.

LONDON:

PBIMTED FOB LONGMAN, HURST, SEES, OSHE, AN»
BBOWN, PATEBNOSTEB BOW;

AND B. TBIFHOOK, ST. JAMES's STBBET.

1814.

y . ,.

• !,:

K;C

30*1

T. B£NSL£Y> PRINTER^
B0U Cowt, IUm Strttt,

PREFACE.

JL HE Science of which a correct outline is
attempted in the following pages y has been
the subject of occasional consideration for up^
wards of two centuries^ but has rarely been
the object of earnest and complete attention.
The surprizing nature of ^ts phenomenay and
the ease with which many of them are pro^
ducedy have made it in the hands of the igno^
ranty and the empirical^ a mere vehicle of shew
and deception.

The attention of philosophers has indeed
been occasionally directed to Electricity^ as a
promising source of discovery ; and after the
immortal Franklin had demonstrated its con^

It PllfiFACU-

nexion mth atmospherical phenomena, if wan
always regarded as an important natural
agents But the insulated nature of many of
the observed facts, and the difficulty of re--
f erring them to any simple general principle^
Continued to mthkoldfrom it that active and
persevering cultivation which is essential to
the promotion, and correct application of every
branch of science*

The discovery of the electrical powers of
the Torpedo, and the Gymnotus, the researches
of Galvani on Animal Electricity, the inven^
tion of the Voltaic Battery, and the discove-^
ries with which it has so recently enriched
and diversified Chemical Philosophy, have
amply demonstrated the connection of Electric
city with the most interesting subjects of ex^
perimental enquiry. Its importance is there--
fore sufficiently obvious, and no obstacle is op-
posed to its extensive cultivation but the pre^
sent difficulty of attaining a competent ao^
quaintance mth the various facts that have

PaEFACli. V

been already ascertained^ and a just concept
tion of their mutual relation and depend^
ixnce.

There are indeed many useful works on
Electricity^ but in the present extended state
of the Science a proper acquaintance with its
principles can only be obtained by the labori^
Qus collection of its zmdely scattered mate*
rials ; which it Tsdll then require considerable
attention to arrange^ and tolerable Mil to
combine ; hence the appropriation of a portion
of time is required for this purpose, which i$
incompatible with the pursuits of many active
and intelligent enquirers, and mil be generally
considered as inconvenient and objectionable^

To remove this difficulty is the principal
object of the present work ; and the devotion
of a considerable portion of my life to the
practical consideration of the subject, tmth
the constant habit of explanation and arrange^
ment, in hectares, authorizes an expectation
that the attempt may be successful.

VI I'BEFACB

By a proper attention to arrangementj I
hme been enabled to communicate a more ex-
tensive collection of facts in a single volume^
than is to be found in any existing treatise
mth which I am acquainted; and that attention
may be expected to render even more concise
statements amply intelligible ; for materials
thus disposed^ are like the combination of
'stones in an Arch; tliey mutually support each
other J and form a connected series^ in which
every part is essential to the existence if the

whole.

The experiments descnhed^ are sufficiently
numerous^ and some of them original; the
simplicity by which many of tlie most essential
are characterized^ will be advantageous to the
indent who may not have access to a regular
apparatus^ or to proper experimental lee--
tares; and it will be of advantage to every
one J to repeat as many of the described ex-
periments as possible, during the regidar
perusal of the work^

PREFACE* Vll

Some apology may he necessary for the
free use of chemical term^s; but this could
not have been avoided withotU omitting a most
essential part of the subject, and a suffid*
ent explanation of them, would have been too
extensive for the limits of an elementary trea^
tise. Those who are unacquainted with Che^
^mistry, may prepare themselves for this part
of the subject, by an attentive perusal of any
of the very excellent works on that science,
of which we have at present such numerous
examples.

CONTENTS.

INTRODUCTION.

HISTORICAL AND EXPLANATORY 1

PART I.

^N £L£€TRICAL PHEN03IEXA, AKD TfiB CIR*
GUMSTANCES ESSENTIAL tO TfiHR PRO-
DUCTION.

CHAR T.

Haiure of Electrical Action^ and Sources of Electrical

^ » •

Exciiation. — Positive end Negative Electridtif.

Production of electncal phenomena « 21

Attraction 22

Electroscopes and electrometerg , ..••,. 23

Cause of the dirergence of electrified bodies .. ^ .•«••••• . 24

Sonroes of electncal excitation.. .••^•. •« •« 25

Fositife and.negative electricity • , p • • . . • 28

-itfethod of distinguishing positive ^om native 29

Experiments on the production of|K)sitive and negative elec-.

tridty ^ .. 30

Thi^ir production is always contemporaneous ^ .;...••«.•• » 32
Table of the efibcts of friction between various/substances • . 33
cVaiioit^ phenomena of excitation.. ^..•^•••.^. « 34

X CONTENTS.

CHAP. IL

Of Conductors and Nonconductors of Electricity ^ and

Ojf the Electrical Apparatus.

Electrical effects are not transmitted by some bodies^ but are

conducted with more or less rapidity by others 35

Demonstcation of the above fact 37

Table of conductors 38

Table of nonconductors 39

Influence of heat> and moisture on nonconductors 40

Remarkable changes produced by heat 41

Natvure of electncal insulatioa 42

Experiments in illustration 43

Structure of the gold-leaf electrometer 45

Electncal apparatus In geberal « . . . . 46

Plat^^tectiical mnohlne • « 4/

Cylinder electric^ machine «...«• 48

Proper construction of a cushion , Ag

Different methods of exciting glass ^ . 50

Necessary attention to the electrical machine 51

Haceipt for the amalgam * .^ . , . 52

CHAP. III.

Experiments with the Electrical Machine* — -Theory
of its Action, — Phenomena of Attraction and i?e-
cession.

'Lines of light> and sparks produced by the action of an elec<-

trical machine « ^ • . « ^ ^ . « . . . • •..«•••• ^

'Pieculiarities attendant on these appearances « . 54

Sunamaiy ^ the phenomena observed wi^ the deotrical

inachme ....,;..«...<.. .<•.«... -..•.. 55

^'Propositions deduced from those phenomena ih.

Theory dfdectric^ excitation 57

^Sxplanation of the- action of ithm tnaditne ..«.«•.•.•«•• ^.. . JlS

CONTENTS. XI

The plienoment produced by the action of a single electxic

fluid A)

DeaioDstnrtion of tins fact by experimentii ^,^, 6l

lAxoamom appearance of positive and negative points ^ 62

£xpenmeat with two hollow balls^ a lighted laper, and

pho^horas • ib«

Experiment on the tiansnusston of electricity through rare-^

fled air ..« .«« • .« ;t3

Stand^ds to which the diflerent electrical states are refeaaed 65

Motion of light bodies by electricity • • . • . 56

Illustration of electrical- attraction « a ib.

Illustrattcm of electrk^al recession ^^ 67

Bodies -similarly electrified recede firom (fttdi other.-— Bodies

differaitly electrified attract eachMher • . • 6lS

Inference from the preceding fact : entertaining experiments

that depend on it ...«•« Og

Piienomena produced by electrical attraction JO

Indications of the floateriality of the electric fluid .J2

Phenomena produced by the divergence of electrified bodies ib«
Motion by electrified points , . 74

CHAP. IV.

On the Phenomena of Electric LighL

Circumstances essential to the producdon of electric light. . • J6

Causes by which its appearance is -influenced • • .^ . JJ

Distribution of electricity on the surface of conductors ib«

Nature of .the action of points •• 79

Advantages of a spherical conductor ■. 80

Eflect of diflerent sized balls^ and of varieties in their situ-
ation.' A ^ngie prominent point more active than seve-
ral combined ;..... ••.••..••... 81

Effect of a point projected- more or less fi'om the suiface of

a ball *...... 82

Action of difletent jized condttcto» ib.

Xll CONTENTS.

Miethods of producing sparks of various leogtfa and denaitj. . 83
lAuniooas brush of rays: eflectof a pomt and a ball compared 84
Influence of surroonding bodies on the action of a poinL^^In-

creased elecdical capacity l^ extension of sor^Ke 85

Effect of the transmitting conductor, and the density, &c. of
the surrounding medium, on the brilliance of the spark. . 86

Tiig'tiSig form of the long q>ark. — Its cause 8jr

Apparatus^ for procuring theelectrlc ^larkin different gaseous

mecfiums: their efiects 88

£&ct^f the transmissiop of electricity through a barometri-
cal vacuum, more or less rarefied BQ

Difiised transmission of electricity through highly rarefied air po

Experiment with a ball and silver thread gi

JBIectrlc light similar to solar light : prismatic cdours pro-
duced by a spark through wood ib.

Various appearances of the electric spark : electric illumi-
nations 92

Brilliant efiects of electric light .«. ^ .. ^ ...•....«..«. .^^ . 03

CHAP. V.

On the Leydtn Jar^ and the Nature of Electrical

Influence.

Ejffect of opposing an insulated to «n uninsulated conductor Q5

Cause of the preceding effect 96

Insulated condnctors may be electrified to a greater extesat

^ when situated near those that are uninsulated • gj

.Coated pane of glass / 99

Construction of the Leyden jar. . Elecuric shock 100

Spontaneous explosion. Charging and dischmpng 10 L

Discharging rod. Henley's quadrant electrometer 102

Coated surfaces charge more slowly than insulated conductors 103
A Leyden jar cannot be charged unless one of its surfaces

communicates with the ground 104

Jf electricity be added to one sur&ce of coated glass an equal

qq^Qtity les^ves the. opposite sur&ce •• . • « ... 10^

CONTENTS. Xiif

Ad insulated jar may be chargpd when its coating comma*

nicates with the rabber 10©

Action of the discharging rod. — Fractare of jara by a higk

charge. — Effect of jars of different thickness 107

A charged jar can only be discharged by a conducting com*

mmiication from one of its sur^tces to the other 108

Jars charged and discharged by the contrary electricities. , 109

Division of a charge. — Action of the metallic coating 1 10

Method of charging an uncoated jar Ill

The coating only a conductor to the chaise 112

Permanence of the usual charge. — Construction of a Leyden

phial which retains its oharge in the pocket 113

Utility of varnishing the uncoated part of the glass.— Gene-
ral observations on theory 1 15

The phenomena of charged jars analogous to other electri-
cal operations. — Both sides of the jar evince the same
electrical state whilst charging, but are found oppositely

electrified when charged II7

Charge of a plate of air , 118

Analogous phenomena of sparks^ &c 120

Construction of the electrophorus • 121

Experiments with the electrophorus 122

Theory of its action 123

Construction of Volta^s condenser « 126

Mr. Cavallo*8 improvement. — Combined condensers 128

Other instruments of greater sensibility but more equivocal 129
Two methods of exciting electrical appearances ; first, by
the actual commanicatioti of electricity j second by its
unequal distribution • • ••• 130

XIV CONTENTS.

PART IL

OF THE MECHANICAL AND CHEMICAL AGENCIES

OF ELECTIIICITY.

CHAP. I.

InstrumerUt required for the Application of the EleC"

trie Power to the Purpose of Experiment.

General observations 131

Construction of an electrical battery 132

Precautions to prevent spontaneous explosion 134

Proper thickness for the jars — Lane's electrometer 136

Description of Cuthbertson's balance electrometer 137

Distinction between quantity and Intensity,— Method of

forming a circuit 135

Electricity passes through the best conductors and by the

shortest possible course 140

Velocity of the electric discharge, and distance to which it

may be conveyed 141

Measure of conducting power 14:J

Construction of Henley *s universal discharger 143

Regulation of the force of the electric spark.'-^Instruments

for passing it through fluids or gases 144

Mechanical skill essential to an electrician 145

CHAP. II.

Mechanical Effects of Electricity.

Mechanical power of tlie electric fluid Inferred from its

effects 147

Perforation of compact bodies.— Paper torn 148

Brittle bodies broken.-^Soft and fluid substances expanded 149

Fracture of stout pieces of glass 150

Electrical artillery.— Explosion over ice . . . ' 151

CONTENTS.. 31 y

Various eipaoslve e£^t8.-'-«-Spark under water ^ ........ • 152

Spark under various fluids.— £xpk)sion$ ov^r the surface of

water ^id acids «...••••..•• 153

Materiaiiiy of electricity.-— Perforation of glass ..•••••••• 154

Fiacture of a small jar by the charge of a large one 15d

Fusion of the coating at the point where the discharger is

applied.— Soldered coin ,..,... 157

Mechanical effects that indicate the course of the electric

fluid.in the discharge 158

Spontaneous discharge by a brush of rays ••.... 159

Spontaneous dischai'ge in rarefied air< — ^Transmission of heat

in the direction of the electric fluid 160

Motion of a pith-ball during the discharge l6l

The perforation of a card. — A bur is raised on each side by

expansion . . ^ l63

Mr. Synuner's experiment.— His mistake 1 64

Course of the fluid shewn by the efifect of a charge on a card

coloured with vermilion • l65

New mechanical demonstration of the course of the elec*

trie fluid 165

Another arrangement for the same demonstration l6i^

(Grepeiral remark on the preceding facts l6Q

CHAP. III. '

Chemical Effects of Electricity.

Light and heat frequently accompany the chemical action

of electricity 17^

Inflammation of combustible bodies by electricity 1 73

Similar effects produced on the surface of water 17^

Metals melted and driven into glass and paper 17^^

Designs impressed on silk or paper. — ^Wire flised 175

Two inches of wire fused by a single jar charged to fifteen

grains of the balance electrometer .' 176

Eight inches of wire fused by the same jar charged to 30

grains 3 or by two jars chained to 15 grains ......... 177

xri CONTEXTS.

E^hteen feet of wire melted at one explotioo • • IJK

Thick jare charged to the same intensity do not melt the

. same lei^th of wire as thin ones.— The fiision of wire

a good measiuie of the qoantitjr of electricity discharged

fit>ma jar (X' battery ,. ...^ 179

Varioos degrees of ^itioor.— Effect of different charges od

an iron wire ». « ••« 180

Ftodaction of metallic oxides by electricity 181

Apparatus for exploding wire in a receiver ; • • . . 182

Efiects produced in soch experimenta • . 184

Table of the comparative charges used to oxidate different

'vnres.— -Figures on paper and glass 185

Table of the comparative charges used to oxidate thinner

and shorter wire. — Curious efiect on a brass wire ISff

Bfivival of metals fi'om their oxides • ^87

Decomposition of water by electricity , T. ; . . 188

Dr. Wollaston*s apparatus for decomposing iKrater 189

Decomposition oi cnk, alcohol^ and ether> Src • igo

Separation of acid and alkali ; and revival of metab froHi

their solutions by electricity igi

Composition of water from oxygen and hydrogen jgfX

Inflammable air pistol.— Inflammable air lamp I93

Composition of nitrie acid firom oxygen and nitrogen 19§

Apparatus for experiments on the gases \fff

Table of the results of electrifying various mixed gases. ... 1 98
Table of the action of electricity on various compound gases 199

Phosphoric effects produced by electricity 200

Table of some phosphoric substancea 201

Opaque bodies rendered luminous 202

Kelation of electricity to magnetism.— 'The magnetism pro-
duced by electricity depends principally on the situation

of the needle whilst electrified 204

Magnetic polarity produced and reversed by electrical
discharges *..*.... 20i

CONTENTS. KVU

PART III.
NATURAL AGENCIES OF ELECTKICITY.

CHAP. I.

On the Identity of Electriclft/ ^ and the Cause of Lightnings

Introductory observations , 207

Conjectures of Mr. Grey and the Abbe Nollet 200

Dr. Franklin's comparison of the effects of electricity ^nd

lightning , , 23.1

His proposed experiment to ascertain the identity of the
electric fluid, and the cause of lightning. — Execution of
this experiment by some members of the French aca-
demy , : ^ ', . . 213

Lightning drawn from the clouds by the English philoso-
phers, and by Dr. Franklin. — Electrical kite , . ^ , 214

Remarkable experiment. of M. de Romas . • , - . . . 2iQ

Death of professor Richraan. — Necessary precaution 21/

Franklin's proposed defence for buildings from injury by

thunder storms 219

Experiments demonstrating its utility 219

Ditto as applied to ships 221

Experiments on the influence of points 1 ...... . . 2212

Best noethod of constructing conductcrs for (he defence of

buildings fiom lightning ^24

Conductors for ships 225

General remarks on conductors 220

Mt. Moi-gan*s proposed method of constructing therti. .... 227

Cause of chimneys being frequently struck ............ 223

Method of fixing conductors.— Most effectual security for

■ •hips........ .....^ 22^9

XVIU CONTENTS*

Defence for carriages.— 'Precautions for personal security . . 230
General remarks , • 232

CHAP. II.

On the Phenomena of Thunder Storms, and the pro*
table Sources of Atmospherical Electricity.

The effects of the discharge of a thunder cloud and that of

an electrical battery differ only in degree 233

Varieties of the noise of thunder 234

Method of calculating the distance of a thunder cloud .... 235

Different appearances of lightning 236

Relative action of the earth and clouds 237

Connexion of tlie electrical phenomena of the atmosphere

with the circulation of moisture 238

Volta's experiment on the production of electricity by eva-
poration • . ^ 241

De Saussure's objections. — Answered ^ 242

Observations of Mr. de Luc ^ . . . 243

Cause of clouds and rain not satisfactorily explained 244

General observations on the phenomena of the atmosphere 246

CHAP. III.

On some luminous Phenomena of the Atmosphere,
the Observation of Atmospherical Electricity,
and the Arrangement of a new System of InsU"
lotion.

The aurora borealis, or northern lights 250

Reasons for ascribing them to electricity 251

Probable connection between the northern lights and the
earth*s magnetism 252

CONTENTS. XIX

Description of a remarkable aurora by Mr. Dalton 253

Brilliant appearance of the northern lights in the polar re-
gions 256

Peculiar noise said to accompany the northern lights 257

Aurora Australis, or southern lights 258

Meteors. — Characteristics of the larger ones which are some-
times attended by the fall of stones 259

Falling stars, or shooting stars. —Their peculiarities 260

Occur in various weather, and sometimes are very numerous 201

Arguments in favour of their electrical origin 262

Imitation of the northern lights and falling stars 269

Electrical spark of five feet long 264

Other natural phenomena ascribed to electricity 265

Observations on atmospherical electricity. — Construction of

an electrical kite 266

Beccaria's exploring wire 269

Extensive atmospherical conductor constructed by Mr.

Crosse 270

Results of various observations on atmospherical electricity 272

Effect of a storm on the apparatus 273

Characteristic electricity of different kinds of weather .... 274

Diurnal changes of atmospherical electricity 275

Atmospherical apparatus of Mr. Read 276

Atmospherical apparatus by Mr. Cavallo and Mr. Bennett. . 277

Arrangement of a new system of Insulation 278

Electrometer which preserves its insulation without wiping

or drying ^79

Permanent insulator for an atmospherical apparatus ...... 28 1

Experiments of Mr. Ronalds. — His plan fcfr registering at-
mospherical changes during the absence of the ob-
server 283

XX. CONTENTS.

CHAR IV.

Connection of Electricitt/ with Medicine^ and Na^

iural History,

Expenments of the Abbe Nollet 285

Acceleration of the motion of fluids in capillary tubes , .. , 2S6

Fiction of the medicated tubes 287

Medical application of electricity 288

Proper machine and apparatus 289

Mr. Morgan's opinion of the application of electricity .... 29 1
Brief enumeration of diseases in which electricity has been

successfully employed 292

Effect of the electric charge on various part of the body. . . 295
Caution against the indiscriminate application of the shock.

— Influence of electricity on vegetation 2gS

Electrical powers of the torpedo, and the electrical eel . .. . 297

Brief description of these animals 298

Relation of their powers to other electrical phenomena . . . 30O

Short account of the discovery of Galvanism 301

Muscular motion produced by electricity • Z0%

Experiment with a frog 303

Experiment with a flounder. — Preparation of the detached

limbs of a frog 304

Muscular motion excited in the legs of a frog. — Experi-
ment with a leech 305

Galvanic sensations produced by the contact of zinc and

silver 30(5

Hypothesis of Galvani opposed by Volta 307

Various Voltaic combinations 308

Tables of Voltaic combinations by Sir H. Davy 311

Volta on the comparative action of metals and fluids 312

Invention of the Voltaic pile 313

CONTENTS, XXI

PART IV.

VOLTAIC ELECTUICITY.

CHAP. I.

Structure of the Voltaic jlpparatus^ and Nature of its

Electrical Phenomena.

•

VoIta*s experiments on the electricity produced by the con-
tact of different kinds of metal 315

Method of exhibiting the electricity of metals 31^

The same demonstration by metallic sieves and filings . 318

Probable cause of these ffK cts. — Metals by which they are

most readily obtained 319

Experiment of Professor Robison ib.

Construction of the Voltaic pile 321

Shock from the Voltaic pile 322

Construction of Cruickshank's improvement of the Voltaic

apparatus 323

Conscruction of Volta*s " Couronne des tasses" 326

Method of combin'ng different Voltaic batteries 32S

Effect of different fluids in the Voltaic apparatus.— Its elec-
trical power 329

Influence of the exciting fluid on the electrical power .... 330
Charge of an electrical battery by the Voltaic apparatus. . . 331
Experiments, which prove there is an accumulation of power

by ihe charge of an electrical battery 332

Probable cause of this phenomenon 333

Effects produced by different numbers of plates.— Excita-
tion, of muscular motion by Voltaic electricity. . . .... 334

Most efficient apparatus for the production of pure electri-
cal effects 336

XXll CONTENTS.

CHAP. II.

Chemical Effects of the Voltaic Apparatus.

DifFerence between the chemical agency of Voltaic electri-
city and that of the common machine 338

Decomposition of water by the Voltaic apparatus. . , . . , . 339
Separate collection' of the elements of the decomposed body 342
Their appearance at a distance from each other. — Mr.

Cruickshank*s experiments 343

Kevival of metals^ and transfer of acid and alkali by Voltaic

electricity 344

Experiments of Sir H. Davy 345

His discovery of the principles of Voltaic decomposition and

transfer 347

Transfer of the elements of compound bodies through men-
strua having a strong attraction for them 34^

Constant appearance of inflammable substances at the ne-
gative pole of the Voltaic apparatus : and of oxygen or

its compounds at the positive surface. : 351

Hypothesis of natural electric energies ... 352

Different electrical effects produced by the contact of a cop-
per-plate with various bodies 354

Electrical and chemical relations of different substances. . . 355
Illustration by the projection of various powders on an elec-
trified surface 356

Anomaly in these experiments. 357

Analogy of electrical and chemical action. ^-Chemical affi-
nity suspended or promoted by Voltaic electricity .... 359

Chemical effects of simple Voltaic combinations 3(50

Dr. Wollaston*s experiments and explanation 362

Objections to his hypothesis 364

Experiment opposed to the explanation of Dr. Wollaston. 365

COKTENTS. XXIU

The chemical powers of the Voltaic apparatus are only pro-
duced when two metals communicate with each other

by the interposition of a fluid 360

Experiments by Mr. Sylvester 36/

Chemical phenomena explained by the preceding fects . . . 369

Experiments on the revival of metals 370

Consideration of the hypothesis of electric energy 372

Diflerent conditions for the electrical and chemical effects

of the Voltaic apparatus 374

The same chemical effects continue ' when the electrical

state of the wires is varied 375

Curious experiments on the production of different chemi-
cal efiects in various fluids^ at every interruption of a

metallic circuit in them 37^

Explanation of the distant separation of the elements of a

compound, on the hypothesis of electric energy 379

Different explanation by Dr. Bostock 380

Revival of metal at every interruption in a metallic circuit. '382

Experiment by Sir H. Davy .... 383

General observations on the hypothesis of electric energy.. 384

CHAP. III.

Extensive Agency of the VpUaic Apparatus^ as an
Instrument of Analysis. — Its Influence in the
Evolution of Light and the Production of Heat.

Invariable results of Voltaic decomposition 387

Decomposition of the alkalies « • 388

Properties of Potassium 389

Production and properties of sodium • 39O

Power necessary to decompose the alkalies. 39 1

XXIV CONTENTS.

Aqaalgacn of their bases with mercury 394

Decomposition of the alkalies by heat • • • . 395

Metallization of ammonia • • 397

De€X>mposition of the earths ••.•.«.« 400

"Oeneral phenomena of Voltaic decomposition 402

Evolution of brilliant light between charcoal points 403

Voltaic spark under various fluids 404

Its action on compound gases. — Striking distance of the

Voltaic spark ^ 405

Intense heat produced by a powerful battery 406

Its .action on inflammable substances. , . 407

Deflagration of various metals 408

Continued ignition of wire 409

fijcperiment on the ignition of wire in rarefled air 410

Ratio tn which the power of the apparatus increases^ when

the number of plates is increased 411

Precautions necessary in experiments of this kind 413

Action of diflerent sized plates. 414

Experiment in illustration 4 16

Igniting power of diflerent batteries, supposed to be as (he

squares of the surfaces of the plates of which they are

composed, taken individually 418

Grand Voltaic apparatus of Mr, Children 419

Large Voltaic apparatus constructed by order of the French

government. — Experiments made with it 421

CONTENTS. XXV

CHAR IV.

Sketch of the State of Theoretical Knowledge in
Voltaic Electricity. — Structure and Properties
of the Electric Column.

ISlements of the Voltaic apparatus 42i

The contact of the different metals the primary source of

its electric power . . • *. 426

The power of the different pairs of metal is combined by

the conducting faculty of the Interpol fluid 426

Electro-motive property of the Voltaic apparatus. . • 427

Analogous efiects of the Voltaic battery^ and of a smgle pair

of zinc and copper plates 428

Probable cause of the action of the Voltaic apparatus 42Si

Correspondende of this opinion with the phenomena 431

Cause of the ignition of wire 432

No insulation between the plates of the Voltaic apparatus , . 433
Action of a battery when the different pairs of plates are

connected by metal 434

Explanation of this phenomenon 435

Experiment to prove that oxidation is not the cause of Vol-
taic electricity , 436

No chemical effects produced but when the opposite ends
of the battery are in conducting communication with

each other 439

Probable cause of the different action of various fluids .... 440

Mr. de Luc*s analysis of the Voltaic apparatus • . . . • 441

Division of the Voltaic apparatus into different ternary

groups 442

Different associations for chemical and electrical e^cts . . • 443

ConditioQ for th« production of the shock 444

XXVI COWTENTS.

Opinion of Mr. de Luc on the modification of the electric

fluid in the Voltaic apparatus 445

Reasons for dissenting from this opinion 446

The most active fluids are most transient in their action. . . 44B

Experiments of Mr. de Luc 449

His invention of the electric column 450

Structure of the electric column 451

Diflerent methods of construction 452

Perpetual bell-ringing apparatus 45^

Action of the electric column on electrometers.— Sponta-
neous changes in the action of the column 456

Structure of the column for meteorological observations. . . 457
itonanence of the power of the electric cdumn. — Catises

by which it is partially injured 458

Various experiments with the column. — Charge of a Leyden

jar. — Experiments with 20,000 groups 460

Pofwerflil electrical action of the column, but no chemical
e£fect.'»Propofied experiments with a series of 60,000
groups of silver and zinc. — Conclusion 462

APPENDIX.

VARIOUS ADDITIONS AND CORRECTIONS. EX-
PERIMENTS ON THE ELECTRICAL EFFECTS
EVINCED AFTER THE CONTACT OF DIF-
. FERENT BODIES.

Mr. De Luc's experiments on the effects of friction 465>

Influence of heat on conducting power. — Preparation of

amalgam 466

Demonstration of the vaiious intensity exhibited by <Mfferent

parts of the same electrified conductor 467

CONTENTS. XXVll

Proper materials £or an electrical battery ,, 460

Variation of the experiment on the motion of a pith-ball. . 470
Variation of Mr. Symmer*s experiment on the perforation

of paper by electricity 471

Preparation of electrical cements 47^

Experiments on the electrical effects exhibited by various

substances after their mutual contact 4/3

Medical application of Voltaic electricity 47^

Action of the sun*s rays on the electric column 476

Production of the electrical oxides 479

INTRODUCTION.

At the commencement of the 17th century,
a new branch of natural science was created by
the experiments and inquiries of an English
physician, William Gilbert; who, in a Latin
Treatise, " De Magnete," published in the year
1600, described the existence of an attractive
power as the effect of friction on various bodies.
This property had been observed by tlie an-
cients, as peculiar to the well-known mineral
production Amber; and hence all the sub-
stances enumerated by Gilbert and others, as
possessed of analogous powers, have been called
Electrics ; and the unknown cause of such phe-
nomena, Electricity.*

During the whole of the 17th century, but
little addition was made to the discoveries of
Gilbert; his Catalogue of Electrics was ex-
tended by the celebrated Boyle, who discovered

* From ti>.iY.Tfav, the Greek term for amber.

2 INTRODUCTION,

that their attractive power was much increased,
by wanning, and wiping them, before they
were subjected to friction ; in such cases he ob-
served, that the electrics, whilst rubbing, fre-
quently emitted flashes of light, and he con-
sidered this appearance as an additional charac-
teristic of the electric power.

The discoveries of Boyle were confirmed
by his contemporary Otto Guericke (inventor
of the Air Pump.) This philosopher constructed
an apparatus in which the electric was made to
revolve, as a more convenient mode'of apply-
ing friction. His instrument was the same ia
principle as that now familiarly known as the
Electric Machine. By its aid he ascertained
the constant appearance of light as an attendant
on strong electric excitation, and discovered
the curious fact, that electric attraction is ge-
nerally followed by apparent repulsion.

In the year 1675, Sir Isaac Newton dis-
covered that electric attraction was not pre-
vented by the interposition of a plate of glass;
the opposite side to that which has been rubbed
being also capable of attracting light bodies;
and exciting some curious varieties of motion
in them.

; . • ••

• • • • •

• •• •

INTRODUCTION. 3

At tlie commencement of the 18th centurjr,
the first Treatise on Electricity was published
by Mr. Hauksbee : it contains an account of all
the facts ascertained by his predecessors; and
a variety of new experiments, made principally
to ascertain the nature of electric light. His
discoveries were numerous and important, but
scarcely of sufficient magnitude to constitute a
distinct epoch in the science. His most singular
discovery was the great facility with whicl^
the electric light is produced in a vacuum.

Toward the year 1729, an important dis-
covery was made by Mr. Stephen Grey, a pen-
sioner of tiie Charter-house, who at that time
cultivated this then infant science with grx?at
industry and address. Directing his attention
to the nature of electric phenomena, he endea-
voured to excite them in all known bodies,
and by this means extended very considerably
the catalogue of electrics ; many substances in
which no attractive power was excited by fric-
tion whilst in their natural state, became strong-
ly attractive if rubbed after they had been mo-
derately heated, but lost this faculty sooner or
later when cooled. This fact clearly pointed
out a relation between the state of bodies and

4 INTRODUCTlOJf.

theif power of evincing electric appearances;
iand the nature of this relation was explained
by Mr. Grey's subsequent experiments. Every
attempt to render metals electric by friction
had proved ineffectual in the hands of Mr. G rey,
as well as m thbse of preceding inquirers, when
it bccurred to him, that as electric light ap-
peared to pass between excited bodies and su6h
as were incapable of excitation, the attractive
power might be also capable of communication
from. one to the other. He inserted a wire and
ball, by means of cork, in the extremity of a
glass tube, and on rubbing the tube, found its
Attractive power was communicated to the
wire and ball. He employed longer wires, till
their vibration prevented him from extending
■them further. He then suspended the ball by
means; of pack-thread, from the tube; the elec-
tricity was still communicated. He ascended
,a balcony twenty-six feet high, and suspending
the ball from his tube by a proportional length
of string, found that the electricity was com-
nmnicated frorti the tube to it, so as to attract
light bodies from the pavement of the court be-
low. Associated with Mr. Wheeler, Mr. Grey
iafterwards extended his experiments, and in

INTKODUCTION* O

one instance transmitted the attractive power
of his excited tube through nearly 800 feet of
packthread, without any apparent diminution
of its force. In arranging the apparatus for
these experiments, it was found that a silk line.
was incapable of transmitting the attractive
power of the tube ; an eiFect which these ex-
perimenters at first attributed to its compara-
tive smallness; but they afterwards observed
that a wire of much smaller diameter conveyed
the electric effect completely, and thus dis-;
covered that there are in nature variousi bodies
diflferently fitted for the transmission of elec-
tricity, some conveying it with facility to a
great extent, and others apparently unsuited to
transmit it to. any perceptible distance. The
first class of bodies are now called Conductors
of Electricity, and the second class Non-Con-
ductors, or Electrics: terms which appear to*

* •

have been first 'proposed by Dr. Desaguliers. .

The experiments of Messrs. Grey and
Wheeler show that conducting power does not
depend on the magnitude, but on some pecu-
liarity in the nature of bodies; a . peculiarity
whose cause has not yet been discovered.

In 1732, M. Du Faye, Member of the Aca-

6 INTRODUCTION'.

deiwy of Sciences at Paris, repeated and ex*-
tended the experiments of Mr. Grey: he ascer-
tained that the copducting power of packthread
and other vegetable and animal substances is
l>rincipally dependant on the water they con-
tain: he conveyed electricity to greater dis-
tances by wetting the packthread, and found
the conducting faculty became less perfect in
most fibrous bodies in proportion as their na-
tural moisture was expelled. He also observed,
that such substances as were least susceptible
of electric excitement by friction were the best
t^onducturs of electricity ; though all the bodies
he tried became electric by communication
when placed on a non-conducting support In
this way he electrified himself, being supported
by silk lines, and touched by an excited glass
tube; and on this occasion the Abb^ Nollet>
who accompanied him in these experiments^
drew the first electrical spark from the human
body,

M. Du Faye has also the merit of having
given the first clear account of that apparent
repulsion which obtains in most electric ex-
periments, and was first observed by Otto Gue-
ricke, who had noticed that the fibres of an

IKTRODUCTION. 7

electrified feather receded from each other, ahd
from the tube or globe with which they had
been electrified, Du Faye viewed this pheno^
menon as the indication of a general principle
in electricity, which may be thus expressed^
Electrified bodies attract all those which art
not so, but repel them as soon as they are elec-
trified by their contact. Thus leaf gold is first
attracted by an excited tube brought near to itv
becomes electrical by the contact^ and is then
repelled ; nor will it be agaia attracted while
it. retains ita electric quality : but if it come m
contact with any unelectrified body it loses itii
electricity, and will be again attracted by the
excited tube ; until, electrified by it, it is again
repelled : and thus may alternate attraction and
repulsion be produced as long as the excited
tube retains its power.*

The consideration of this general principle
led the same assiduous philosopher to a disco-
very of the first importance, viz. the existence
of two distinct attractive powers, produced by
the friction of different substances. The on^

« This principle is here stated nearly in the language of
Da Faye, and ef n^ost subsequent writers. Ids propriety will
be considered hereafter.

a IKT&ODUCTION.

excited by rubbing glass, rock crystal, gems,
wool, hair, and many other substances, he called
Vitreous Electricity. The other, resulting from
tb^ friction of amber, copal, gum-^lac, resins,
sealing-wax, &c. he named Resinous Electricity^
The characteristics of these attractive powers
are, that they strongly attract each other, and
|>rdduce a mutual counteraction of eflFect, wliilst
they separately act in an apparently similar
manner on all unelectrified bodies: but the
effect of either of them is destroyed or weakn
ehed by the approach of the other. If gold
leaf be electrified by rubbed glass it immedi-
ately recedes from it, and wiU not again ap-
proach whilst it retains its electric state. But
in this state it is strongly attracted by any ex-
cited . body - of the resinous class, and will fly
to sealing-wax or amber more rapidly than to
an unelectrified body. Hence it was concluded
by Du Faye, that there are two distinct electric
cities, each repulsive of. its own particles, but
having a strong attraction for those of the
other.' So that all bodies electrified with the
vitreous electricity repel those that are simi-
larly electrified, and attract such as are unelec^
trified or endowed with the resinous. electricity.

iktrddiiction; g^

And the converse of this is the case with such
as are possessed of the resinous electricity.

The terms resinous and vitreous electricity,
were sufficiently appropriate at the time they
were proposed; but it has been since found,
that either electricity can be obtaiiied at plea-
sure, both from glass and sealing-*wax, by vary-
ing the nature of the substance with which;
they are rubbed. Hence the vitreous electri-'
city of Du Faye is now called positive electri*
city; and the resinous, negative electricity;*
terms jfirst proposed by Dr. Franklin.

To the labours of Messrs. Grey and Wheeler,:
and their coadjutors Du Faye and NoUet, all
subsequent electricians are highly indebted;;
their means of research were extended by the
improvement of electrical apparatus, necessa?
rily resulting from the discovery of conduct-
ing and non-conducting power; whilst the
generalization of electric phenomena by Du

Faye, and his discovery of the distinction bci^
twecn! positive and negative electricity, was an^
edlargement of the existing sphere of know-
ledge in a degree before unparalleled. From.
tliis period, indeed, the science assumed a moK'
important aspect, its cultivators increased m

10 ZKXRODUCTIOy.

number, and the communication of their re*
searches constituted a prominent feature in the
transactions of the most celebrated societies
and academies of Europe.

In 1748| the Germans began to distinguish
theniselves by an active attention to electricity ;
they improved very considerably the electrical
apparatus, applying the principles discovered
by Grey to the perfection of the known sources
ef electrical excitation. To them we owe the
eiKiployment of a cushion instead of the hand,
as a means of applying friction to excite elec-
tricity: the idea of applying multiplying wheels,
as a method of accelerating in any proportion
the rapidity of such friction ; the cylindrical
form of the electric machine ; and the employ-
ment of an insulated conductor to concentrate
the power of the excited electric, and apply it
more conveniently to experiment.

The great power of the apparatus contrived
by the Germans, increased the analogy before
observed between the appearar.ee of electric
light and common fire ; and induced them to
apply it more extensively to the purpose of
experiment. They succeeded by its means in
inflaming ether, spirits of wine, and other in-

INtltODCJCTIOK* 11

flatnttiable bodies; and thus^v^ere the first to
demonstrate its possible applicatioi^ as a che**
mical agent. Dr. Watson and some oth^r mem-
bers of the Royal Society pursued the path of
discovery opened by these researches; and
tb^ singularity and novelty of th* effects pro-
duced, attracted very general attention to a
subject, which was soon destined to excite uni-
versal admiration and inquiry*

In the year 1746, a discovery was inacte by
some professors in the university of Leyden, of
a method of accumulating the electric power
to an extraordinary degi-ee. The experiment
consisted in enclosing some water or other con-
ducting substance in a glass vessel, and dec-
trifying it; if then the outside of the glass
vessel was grasped with one hand, and the en-
closed conductor or any substance connected
with it touched with the other, a bright spark
ensued) and a violent convulsive motion wa«
felt in the arms and across the breast. Pro-
fessor Muschenbrouk, Messrs. Cuneus> Akmand,
and Winkler, made the experiment with water
in glass jars or bottles; atid M. Von Kliest (who
it is said first made the discovery) employed k
phial in which a blunt piece of wire Was loosi^ly

18 INXnODUCTlOIf.

placed. This experiment soon becstme popular,
the. apparatus received the name of Ley den Jar,
or Ley den Phial, and the sensation it produce4
the Electric Shock. The first experimenters
gave ludicrous and exaggerated accounts of its
effects, and to this circumstance may perhaps
be partly attributed the public curiosity it so
promptly and highly excited. In the same year
it was shewn by itinerant exhibitors in almost
every part of Europe; and the experiment was
repeated and varietl by the electricians of every
country,

Tq trace the progress of electrical discovery
beyond this period in chronological succession,
would be incompatible with the limit of an
elementary work; and, from the extent and
variety of succeeding inquiries, even less eligi-
ble for a detailed history than a connected
arrangement of the discoveries in the order of
their mutual dependance; a plan which it is
my intention to adopt, at no very distant pe-
riod, in a comprehensive history of this science,
from its origin to the present time.

To complete the preceding sketch, as a ge-
neral outline of the science, . I shall now briefly
enumerate the most important electrical disco*

INTUODUCTION. 13

veries that have succeeded the Leyden experi-
Hient. Dr. Watson in England, and Dr. Frank-
lin at Philadelphia, nearly at the same time, and
without any previous concert, improved the
structure of the Leyden jar,- and advanced aa
explanation of the various phenomena of elec-
tricity. Their propositions were nearly similar;
but that of Dr. Franklin being most perfect,
and liaving a real priority of publication, waa
adopted, and has been since celebrated as the
Franklinean Theory of Electricity. He referred
all electrical effects to the motion of a peculiar
fluid, repulsive of its own particles, and having
an attraction for all other matter. And he
considered the opposite electricities of glass
and sealing-wax as indications of different states
of this fluid : the vitreous electricity being the
plus or positive state, and the resinous the mi-
nus or negative state. All bodies can contain
a certain quantity of electric fluid in a latent
itate. If this quantity be increased they be-
come electrified positively; if it be diminished
they are rendered negative. The production
of electrical effects is therefore nothing but the
result of the unequal distribution, by art, of a
naturally diffused fluid.

14 INTRODUCTION.

Such are the leading principles of the Frank-
Hneatt theory ; they have been considered ma-»
tfaematically by Mr. Cavendish, and by ^pinus^
and, with some modifications^ ^PP^y ^ niost of
the phenomena at present known.

Our existing theoretical views are derived
principally from this source, aided by the re-
searches of Messrs. Canton, Kinnersly, Henly,
Beccaria,CavallO; Bennet, Volta, DeLuc, Morgan,
Cuthbertson, &c. who have severally contributed
most extensively to this branch of knowledge.

Before the discovery of the Leyden Jar,
electricity had not been applied to any useful
purpose. Dr. Franklin was the first to supply
this deficiency; he pointed out a striking re-
semblance in the effects of lightning and elec-
tricity; and, conceiving they might result from
different modifications of the same power, pro-
posed to verify his conjecture by experiment.
He conceived the bold attempt of collecting
lightning from the clouds, and subjecting it to
examination. His suggestion was first attended
to by the French philosophers : they confirmed
bis conjecture on the 10th of May, 1752, and
performed the ordinary experiments in electri-
city hy means of that terrific power* Before

JNTRODUCTIOK. 15

any account of their success had reached Dr.
Tranklin^ h^ had himself obtained a similar r^
suit ; and the experiment was soon repeated in
almost every civilized country.* Franklin im-
mediately followed the confirmation of his dis*
covery, by its application to the defence of
buildings and ships from injury by thunder
storms ; and his endeavours were attended by
every expected success. They were followed
by the observations of other able philosophers>
and will (with them) be considered in a subse*^
quent part of this work.

The discovery of the atmospherical agency
of electricity drew the attention of philosophers
more closely to that subject, and their inquiries
have for the last sixty years been attended by
continued accessions of knowledge; many
other sciences have been enlightened and assist-
ed by its cultivation; and the more refined na-
tural phenomena are rarely investigated without
the cooperation of its principles.

Electricity has been applied to medicine
with various success ; much of empiricism

* It will be described mdfix tbQ sectioo 90 tb^ R«jlura]^^0'
cies vf eloctricrty.

1$ rXTRODUCTIOK.

clouded its earlier application ; for mysterioug
agents are always convenient implements of
imposture ; but the delusions of quackery, and
the mistakes of ignorance, ought not to operate
against the scientific employment of a power-
ful agent, so easily controuled and susceptible
of such various ' application. At present, the
medical employment of electricity is most fre-
quently adopted when other remedies have
failed; and its success, under such circum-
stances, is a cogent argument for more exten-
sive and impartial trials.

The connection of electricity with natural
history has been demonstrated by Mr. Walsh,
and Mr. Cavendish. They have shewn that the
torpedo and gymnotus owe their extraordinary
power of benumbing the faculties of animals
of superior strength, and of arresting the pro-
gress of the swiftest of the watery tribe, to the
faculty of suddenly accumulating electricity,
and of discharging it in any direction at plea-
sure. The effect of electricity on the animal
economy has been an object of attention at
intervals, since the first observation of the pe-
culiar sensation of the electric shock. Beccaria

I^TUODXrCTION. 17

of Turin, appears to have first noticed the
power of electricity in producing muscukr
motion. And Galvani, in 1791, instituted a
series of experiments which promised to kad
to a full developement of the nature of the
nervous influence, and of the origin of mus*
cular motion. His hypothesis, which supposed
the constant agency of electricity in the animal
economy, was opposed by professor Vol ta, who
had already distinguished himself by important
dectrical discoveries. This controversy gave
rise to the invention of a new source of elec-
tric power, the Voltaic Battery; an instrument
which, in the short space of thirteen years,
has created a new science, and effected the
most important discoveries in chemical phi-
losophy.

The application of electricity, as a chemi-
cal agent, was, as I have already stated, first
suggested by the experiments of the Ger-
mans.

It was successively employed in this way
by Dr. Watson, the Abb6 Nollet, Dr. Franklin,
Mr. Kinnersly, Signior Beccaria, and most ex-
tensively by Dr. Priestley. The inquiry was

18 iNTOOnUCTIOK.

imrsued by Mr. Cavendish, Professor ITolti;
the French academicians, a society of Dutch
chemists, Mr. Cuthbertson, Mr. Morgan, and
Pr. Pearson. I shall endeavour to notice the
most important of their experiments, as the
subjects to which they relate shall occur.

During the interval that elapsed from the
discovery of the Leyden Jar, to the invention
of the Voltaic Battery, many important prac«>
tical improvements had been made in the me-
thods of experiment. The original apparatus
was greatly improved, and many hew instru-
ments invented. Dr. Priestley, Mr. Naimci and
Mr. Cuthbertson, successively contributed to
the perfection of the electrical machine, and
the apparatus for accumulating its power, or
directing it to the purpose of experiment. And
for the more refined purposes of inquiry, vari-
x)us delicate tests of electrical action were con-
trived by Canton, Cay alio, Bennett, Volta,
Nicholson, Read, and Cuthbertson. To these
instruments we are indebted for some of the
most interesting discoveries.

From the period of the invention of the
Voltajc Pattery, the progress of experiment

INTRODUCTION. 19

has been so intimately blended with chemical
inquiry, as to constitute a distinct branch of
science. This part of the subject originating
with the discovery of Volta, and continued by
the researches of the most celebrated philo**
sophers of modem times, I have thought it
necessary to arrange, and consider separately
under the general term. Voltaic Electricity*

ELEMENTS

ELECTRICITY.

PART I.

OF ELECTRICAL PHENOMENA^ AND THE CIRCUM-
STANCES ESSENTIAL TO THEIR PRODUCTION.

CHAR L
Nature of Electrical Action^ and Sources of
Electrical Excitation. — Positive and Negative
Electricity.

If a white and a black silk ribbon, of two or
three feet long, perfectly dry, be applied to each
other by their flat surfaces, and are then drawn
repeatedly between the finger and thumb, or
over dry silk-velvet, or woollen cloth, they
will be found to adhere to each other; and if
separated at one end will rush together again

22 ELECTRICAL PHENOMENA.

with great rapidity. Each ribbon, when sepa-
rated^ will attract any light substances to which
it is presented; and if the experiment be made
in a dark room^ a flash of light will occasionally
attend the separation of the ribbons.

SticVs of sealing-W2^' resin, or flulpliurif when
rubbed with dry woollen cloth, or fur; and
tubes or rods of glass, when rubbed with silk,
exhibit similar powers ; and if of sufficient size,
produce, when applied widiin a short distance
of the face or hand, a distinct and singular
sensation.

These effects having been first produced b^
the friction of amber (electron), are called elec-
trical phenomena; and the processes employed
for their production, the excitation of elec-
tricity.

Attraction is the phenomenon most con-
stantly attendant on excitation ; it is therefore
considered as an indication of * die presence
ami action of electricity, and is the basia of
a}l its testB. Electricians formerly, * for sufcb
trials, employed a light wooden or metal nee«}{e,
supported by its centre on a point, or a thread
or feather delicately suspended. To thcsi Ae
excited body waS: presented^ and if they were

BXCITATION OF ELRCTAICITIT. iS

attracted by it^ the attraction was attributed
to electricity, and the excited body called an
electric.

The suspended needle, and every contrivance
employed for the same purpose, is called an
electroscope, when designed to indicate the
existence of electrical phenomena; atid an
dectrometer, when considered as a measure of
their force. The latter term alone appears neces-
sary ; for eviery contrivance hitherto employed
to ascertain the presence of electrical phe-
nomena is also calculated to measure their
power. Thus in the instance of the ballanced
needle, or suspended feather; the greater or
less distance to which it is necessary to bring
the excited body before attraction ensues,
supplies a measure of the force of such at-*
traction.

The most useful electrometers are construct-
^ by suspending two slips of gold leaf from
the cap of a glass cylinder^ as represented by
Fig, .1 . The slips of gold leaf hang in the cen-
tre of the cylinder, parallel and contiguous,
when unelectrified ; but separate from each
other (as shewn in the figure) when electrified ;

S4. BXClTilTrON OF ELECTAICtrr.

in consequence of their, attraction for the sar*
rounding air and the sides of the glass.* i

Small balls turned from the pith of eider^
and suspended by fine threads or silver wires,
are sometimes substituted for the gold strips^
They are less easily affected, but they are more
di^rablew The pith balls suspended by thread
or wire, are also occasionally used withoot isb
glas^ cylinder. — See Fig. 2. -

.Electrical phenomena then are characterized:
by the attraction and recession of light sub^
stances; the consequent production of motion
in them, and of sensation in living bodies, andr
by the evolution or production of light Various-
are the means by which these effects may be. '

* The separation of electrified bodies is usually ascribed
to repulsion ; an assumption quite hypothetic and unnecessary.
Lord Stanhope has shewn that the separation is less in raare tbaii
in dense z\x ; which is contrary to what ought to obtain if re-
pulsion was its cause. Mr. Kinnersley first remarked that
there were rio proofs of electric repulsion, and shewrd that the
supposition of its existence was a barrier to the explaAatioa d(
Electric phenomena. See Franklin's Electricity, page S84.— *
Mr. G. Mbrgdn has since expressed the same opinion 5 which
is, also* entertained by professor Volta. It occurred to me before
I .knew of these authorities, and would, I should presunoe, to>-
any one sufficiently acquainted with the varieties of electrical
action.

XXCITATION OF £L£CTRIC1TT. 25

produced, but their most obvious sources are
the following : ..*

J St Friction.

2d. Change of form. ' ' ' s

3d. Change of temperature*
4th. Contact of dissimilar bodies.
The instances of the first kind are most-
numerous, and indeed under certain limits uni-r
Tersal. They may be obtained by rubbing. any?
one of a most e:H:tensive list of resinous and
siliciou3 . substances ; and of dry, vegetable,,
animal, and mineral productions. The elec-,
tiicity thus .excited, is most readily shewn, by
presenting the rubbed substance to the cap of
the gold-leaf electrometer.

Examples of the second kind are also ex-
tensive. Sulphur melted and poured into a
conical wine glass, contracts, and becomes elec-
trical in cooling. A silk thread, or a stick of
glass should be inserted in the sulphur M'hilst
fluid, to serve as a handle; when cold it may
easily be separated from the glass by its handle,
and will then affect the electrometer, and evince
other electric signs. If the sulphur cone be
kept in the gl^ss in which it was made, it wiU
preserve its elegtric power for years, and evince

S6 EXCITATION OF ELBCTRICITT.

them perceptibly, whenever the glass and sul-
phur are separated.

Chocolate, when it congeals after fusion,
esihibits similar properties; and Chaptal ob-
served the same circumstance during the con-
gelation of glacial phosphoric acid« Calomel
also, when it fixes by sublimation to the upper
part of a glass vessel, has been found strongly
dectrical. The condensation of vapour, and
the evaporation of fluids, though apparently
opposite processes, are alike sources of electri*
cal excitation.

Various crystallized gems, and a stone called
the Tourmalin, become electrical by the mere
application of heat; but no other substances
have yet unequivocally manifested the same
property ; though the effects of friction are ge-
nerally increased, if it is preceded by a mo-
derate elevation of temperature.

The contact of dissimilar bodies is probably
in all cases the real primary cause of electrical
excitement, but it is rarely employed alone;
for electricity is known to us only by its effects,
which are constantly the result of an artificial
arrangement, and consequently may not imme-
diately succeed the primary cause of electric

XXCITAT^OX OFELECtRlCiTT. 27

motion. Muscovy talc/ when its lamina are
suddenly torn apart, appears electrical, and
sometimes exhibits a bright flash of light ; such'
is occasionally the case with other substances,
but we have no evidence from these experi-
ments that will enable us to decide whether
separation be the primary, or only the proxi-
mate cause of the phenomena. In most in-
stances contact app^rs to produce an eftect,
which is to hie ^kibited only by separation'; but
t^re IS one decisive instance of electricity pro-
duced by contact alone, the electric column,
(inventqd by J. A. De Luc, esq.) It consists of
800 of 1000 small discs, of silver, zinc, and pa-
pdr ; placed upon each other regularly, in the
order named, and enclosed within a glass tube
ib consecutive gtoi^ps.* Either extremity of
this apparatus will at any time affect an electro-
meter distinctly, without any previous prepara-
tibif. Its power must consequently arise from
the contact of the different materials of which
^t is compAsed. Now, as this is the most simple
instance of electrical excitement; and as the

• ■

' '-* A'tsS^ am^le ^ct\piioa-6£ tbi» constnictidn and pro*
perlied of th^dactrio coluoin will ba- foand. in anotfaer part of
this work.

S8 POSITIVE AKD N^fOATIVE SLBCTBSCITT.

effects produced are permanenty it is highly
probable that previous contact may be the re^
mote cabse of the effects attendant on other-
processes.

However various the means employed td
excite electricity, its effects are constantly the
same; but certain phenomena obsierved at a
very early period, shew that there is a distinc•^
tion between the -causes by which they are proM
duced. Sealing-wax and glassy, for instance^
equally rubbed, will either of them occasioti'
divergence in the leaves, or balls, of an electro^
meter, when presented to it separately ; but if
they are applied together, no effect is produced.:
Again, if the electrometer has been made to.
diverge by contact with excited wax, such di-'
vergence will be lessened by the approach, and!
destroyed by the contact of excited glass. Or;
if it be first electrified by. excited glass, the:
electricity, will disappear when excited wax is-:

presented to it ^ Here then appears two elecH

. " ■ . *

* Some care is necessary in these experiments* wfaich CBxt
only become familiar by practice. Tbe sealing-wax and glan
should not be excited more powerfully than is sufficient to affect
tbe electrometer distinctly; and when the leaves ato intended
to remain divergent, the excited. bo4yj>boi|14.. (ins brougjht Uuo
actual contact with the cap of the instmment.

POSITIVE AND NEGATIVE ELECTRICITV. 29

trie powers, similar in their separate action on
the electioraeler, and other indifferent matter;
but exerting a mutual influence on each other>
destructive of their individual properties.

It was at first conceived, that these pheno-
mena were peculiar to the substances by which
they were produced; and hence the power ex-
cited by rubbing glass was called vitreous elec-
tricity ; and that resulting from the friction of
sealing-wax, resinous electricity; but it is now
demonstrated, that both powers are produced
in every case of electrical excitation, and as
their mutual counteraction of effect resembles
that of an affirmative, and a negative power;
the terms positive, and negative electricity,
have been substituted for vitreous, and re-
' sinous.

The practical determination of these states
in different excited bodies, is of importance to
the electrician, and may be thus effected. Seal-
ing-wax, when rubbed on woollen cloth, is ne-
gatively electrified. Glass, when rubbed by
silk, is positively electrified. Let an electro-
meter be made to diverge by the contact of ex-
cited scaliug-wax; whilst thus diverging ap-
proach it with any excited body, whose dec-

JO FOSITiyi lAND KSOAT IVM IXXCTUClErT^

tripity is to be determined. If the divergence
of the electrometer increases, the presented
.body is negative ; if it is diminished, the prei-
sented body is positive. In other words^ all
tfaos€^ substances that lessen the divergence oc-
Casioned by excited wax, are positive; and such
as increase it, negative: whilst those which
lessen the divergence produced by cixcited
glass, are negative; and such as increase it,
positive.

If we examine by this test, the effects pro*-
duced in some of the instances of excitation
already considered, the truth of the preceding
statements will appear, and the relation of the
different electrical states to the processes by
which they are produced, will become more iur
telligible,*

Ej^riment 1. Roll up a warm and dry flan-
nel, so as to admit of its being held by one exr
tremity, whilst a stick of sealing-wax is rubbed
with its opposite end. After slight friction^
present the flannel to an electrometer, which

;* After everjr eiperiment, the divergence of the electro-
neter should be destroyed, obLbss it be otherwise stated. This
is 4iflfiBeted bj touching its cap^^with tW finger^ or a piece of

yOSITlTE AND NEGATIVE EXECTBICITY. 31

will diverge; whilst the divergence continues,
bring the stick of sealing-wax near the cap^
and the leaves of the electrometer immediately
close. Sealing-wax and woollen cloth are there-
fore both electrified by mutual friction; but
their electricities are opposite ; the wax being
negative, the woollen positive.

Eaperiment S. The electrical powers thus
excited, are equal to each other; for, if the
friction be repeated, and the wax and flannel be
both presented at once to the electrometer, no
sigtis of electricity appear. The opposite elec*
tricities, when applied together, producing a
reciprocal counteraction of effect.

Experiment S. Excite a black and a white
silk ribbon, in the manner described at the com*
mencement of tliis chapter. On separation, the
black ribbon will be found negative ; the white
one positive.

Eaperiment 4. Take the sulphur cond^
(formed by pouring melted sulphur into a coni-
cal wine glass), apply the cone, and the glass,
separately, in succession to the electrometer;
the former will be found negative, the latter
positive.

EjTperment 5. Apply the opposite ends of

92 POSITIVE AMD NEGATIVE BLECTRICITT.

the electric column^ alternately, to the electro-
meter; they will be found differently electri-
fied: the end terminated by zinc, being posi-
4ive; and that terminated by silver, .negative.*
Hence it appears, that positive and negative
electricity are produced atthe same time in ail
our experiments, and may be observed when
proper means are employed for that purpose.
But it is also seen, that by friction with the
same substance, different bodies are variously
affected; for glass rubbed with silk evinces
positive electricity; but sealing-wax rubbed
with silk is rendered negative. Again, polished
glass, when rubbed with silk, skin wool, or
metal, becomes positive ; but if it be excited by
friction against the back of a living cat, it ap-
pears negative. Wool, silk, or fur, rubbed
against sealing-wax, are rendered positive ; but
gold, silver, or tin, are by the same process ren-
dered negative. ^

* Some difBcuIty attends the negative electrization of tha
gold leaf electrometer^ by excited wax -, which sometimes sepa«
rates the leaves so powerfully, as to destroy ihero. The electric
column is more convenient for this purpose. A short contact
of its silver extremity with the cap of the instrument will com-
municate the proper negative divergence. It may therefore be
employed in the preceding experiments.

SOUHCES OT ELECTRICTTri SS

Tables have been formed exhibiting these
effects between a variety of siibstances. The
folloMring ii^. given on the authority of Mti
CavaUo:— ■

Is rendered BtffrittUmwUk

H^l-ckaf.catf Positi. { ^-, 3^tan<.^^^^

Soiboth Glass: .1 Positive I E^ry ii«bstan«i hiftci^

C . . t except the back of a cat»

Dry oiled silk, sulphur, metels
Woollen cloth, ' qbillsy wood,
paper, sealing-wax, wfake-
^n. the buman band.

f «--;,._- f Amber, Mast of Sir from bdi

ToormaHn ^ *^°"*"'* | lows.

( ^egativd Diatiidnds, the bttanan faandL

r p .. C Metals, silk, Ibadstonejesfther,
Hare's akin .... ^ rosuivc | ^^^^^ p^p^^^ ^^^ ^^^

f Positive

itaigi. eb«. . . . j N««».|

dte sBk • « • ^ . <

^^ative Other finei" furs.

. I'asitive Black silk, metflls, bldck clotin
Wlutc

J^egative t^aper, hand, hair, weii^Vs skiii.

r Positive Sfealing-\(rax.
t^t. • .ty y r Hare's, weasel's, andferret'sskto,

AiacK suK 4< Negative ^ loadstone, brass, sUver, iron,

( . C hand, \(rhtte sUk.

r Poative Some metals.*
^. f< J CHare'SyWeasers, and ferret's skin,

5eaiing-wax. ...< Negative ^ hand, Iwthcr, woollen-cloth,

( (. paper, soipe metals.

Baked wood. . . . <

Positive Silk*
Negative Flannel.

* Mr. Cavallo had inserted nietals, which appeared to imply.
thai tbeirictioDof i|ll ^oetajb electrified sealing-wax positively i
this I find is not the case : ircfn, st^l, plumbago, lead^ and bis-.

S4 SOtTRCES or ELECTBICITT.

The result of experiments of this kind is
much influenced by the state of the bodies em*
ployedj and the manner in which friction is
applied to them. In general, strong, electric
signs can only be produced by the friction of
dissimilar bodies ; but similar substances, when
rubbed together so that the motion they indi-
vidually experience is unequal^ are sometimes
electrified; and, in such cases, the substance
whose friction is limited to the least extent of
surface, is usually negative. Such is the case
with the strings of a violin, over a limited part
of which the bow passes in its whole length,
and the hairs of the bow become positive. Simi-
lar is the effect when two ribbons of equal sur-
face are excited by drawing one lengthwise
over a part of the other ; that wliich has suf-
fered 'friction in its whole length becomes posi-
tive, and the other negative.

mnth^ render sealing-wax negative^ and all the other metals i
have tried leave it positive. I have therefore made a slight al-
teration in the table. The least difference in the conditions of
such experiments will occasion singular varieties of result; with
the same rubber (an iron chain), positive electricity may be ex-
dted in one stick of sealing-wax and negative in another, if the
fimner have its surface scratched and the latter be perfectiy
stnooth. Many repetitions of each experiment are therefore
enentid t» an acoonte condwon.

SOURCES OF £LECTklCITr. 35

From these facts we learn that positive and
negative electricity are concomitant phenomena,
and that in aU cases of electrical excitement,
they are both produced^ though one only may
occasionally appear, (a circumstance whose
cause wiU be soon explained). . It is seen also
that these phenomena are not peculiar to any
distinct class of bodies, but may foe produced
indiflerently, or alternately, in various suW
stances^ by changing the materials or method
by which friction is communicated to them;
'itiis knowledge simplifies the appearance of
siicb electrical effects as have been here con<-
sidered, by referring them to a general origin ;
but the peculiarities of electrical action are not
yet Sufficiently developed to authorise any we^
sent speculation on its cause.

D 2

r<»

t ■ I

r . • .. :

CHAP. 11.

OfCmdttCtarsand Nmrcmdmctori of EUctridtyr
. and cf the Electrical Apparatus.

I?*, ;)]as beei) seen by the permanent divergence
of the eliectrofnct^r,- wbien an - excitisd electric
is brougUt in ' contact with it, that electricity-
capi be communicated or conveyed froA one
bodyto another J and a history of the :discQr'
veries of Mr. Grey, on this subjecti has been
giyepi in the Introduction. But the fecttlty of
flectrical transmission is very different ia dij^
f^ront bodies ; some convey ijt with great rapi*
dity ; others more slowly; and there are some
that appear absolutely to arrest its progress.
Examples of this fact are apparent in the most
simple experiments. The divergence of an
electrified electrometer may be destroyed, weak-
ened, or maintained, by touching its cap with
different bodies ; now, as the divergence of the*
electrometer is caused by its electricity, wdi
effects can only be produced by the relative
poirer of the touching bodies to deprive it

GONDucrdUft AND Kon-^coKBVCtom: ST

thereof; for whilst the electricity remains,^ itsr
divergence will continue unaltered*

Experiment 6. Touch the cap of an electric
fied electrometer with a stick of dry glasls, sul-
phur,, or sealing-iVax. The divergence of its
leaves will continue.. These substances then, do
not transmit electricity.

Experiment 7. Touch the cap of thie elec-
trified electrometer with a piece of wood, a rod
of any metal, a green leaf, or with the finger.
Its divergence immediately ceases. Such bodies
therefore permit the transmission of electri-
city.

By experiments of this kind it is found,
that there is a gradation of effect from one
class of bodies to the other. Those which trans-
mit electricity with, facility are called Conduc-
tors; those whose transmitting powers are in-
ferior^ Imperfect Conductors ; and such as have
no power of transmission, Non-conductors : but
m general the various bodies in nature are' di-
vided into two classes only; the remote ex-
tremes of each forming the intermediate class. -
• In the following enumeration of the princi-
]Ml Conductors, and Non-conductors, the sub-
Btuices M e placed niearly in the order of their.

38 CONDUCTORS AND KON-COITDUCTOES.

perfection ; but the determination of this cir-
cumstance has not hitherto been accomplished
with much precision.

Conductors.

All the known metals.

Well-burnt charcoal.

Plumbago.

Concentrated acids.

Powdered charcoal.

Diluted acids, and saline fluids.

Metallick ores.

Animal fluids.

Sea water, spiiBg water.

Biver water, ice and snow.

Living vegetables.

Flame, smoke, steam.

Most saline substances*

Rarified air. Vapour of alcohol and ether.

Most earths and stones.
Many of the preceding substances fail to
conduct electricity when they are made per*
fectly dry ; hence it is concluded their conduct*
ing power arises from the water they contain.
Indeed this faculty does not permanently exist
in many of the bodies enutnerated, but varies

CONDUCTORS AND NON-CONDUCTOBS.

or disappears with their modifications of tem-
perature, &c. Thus hot water is a much better
conductor than cold water; and such is also tli.e
case with charcoal, and other substances.

Non-conductors.*
Shell-lac, amber, resins.
Sulphur, wax, jet.
Glass, and all vitrifications; talc.
The diamond, and all transparent gems.
Raw silk, bleached silk, dyed silk.
Wool, hair, feathers.
Dry paper, parchment, and leather.
Air, and all dry gases.
Baked wood, dry vegetable substances.
Porcelain, dry marble.
Some siiicious and argillaceous stones.
Camphor, elastic gum, lycopodium.
Native carbonate of barytes.
Dry chalk, lime, phosphorus.
Ice at — 13° of Fahrenheit's thermometer.
Many transparent crystals, when perfectly
dry.

* Nancondactors are also sometlmea calkd electrics, and
-occaiionally insulators j but the latter temi is only applicable to
die most perfect of ihtm.

40 COMDUCTOltS AND NON-CO NBUC TOES.

The ashes of animal and vegetable sub-
stances.

Oils ; the heaviest appear the best

Dry metallic oxides.
The most perfect non-conductors becomip
C^onductors by the accession of moisture ; henc^
th^ necessity of preserving them clean and dry
during electrical experiments. Resinous sub-
stances, raw silH, and Muscovy talc, are least
liable to attract moisture, and are therefore
most useful where perfect non-copductors are
required. Glass becomes moist only on its sur-
face, and this tendeqcy may be checked by co-
vering the surface with sealingTwax or good
varnish. Glass consequently enters most ex-
tensively into the structure of an electrical ap-
paratus; its strengthji and the facility with
which it may be procured of any form, fitting
it most admirably for that purpose.

Many substances in the preceding list lose
their non-^conducting power, and become con-
ductors when intensely heated. Such is the
case with red-hot glass, melted resin, wax, &c. ;
but the most intensely heated air, if unaccom**'
panied by flame, is not a conductor. Many
l^brous substances attract water so readily, that

COKDUCtORS AND NOK-COKDUCTOM. 41

it is absolutely necessary to dry and warm them
before their non-conducting property appears ;
this is particularly the case with paper, flannd,
parchment, leather, &c. The influence of heat
on this property is indeed very remarkable, and
not perfectly intelligible ; it is well exemplified
in the following instance : Wood in its natural
state is a conductor ; if baked, its moisture is
expelled, but its organization is not altered ; it
is then a non-conductor. By exposure to a
gveater heat its volatile elements are dissipated,
and its indestructible base (charcoal replete
with alkali) only remains; this is a conductor;
but if exposed again to heat, with access of air,
it suffers combustion, and is converted into
ashes and gases, which are non-conductors.

There does not appear any definite relation
between the chemical characters of bodies and
their conducting powers; for the best con-
ductors, (metals) and the best non-conductors,
(resins, sulphur, &c.) are alike inflammable /sub-
stances. The products of combustion too, are
dissimilar in this respect: acids and alkalies
conduct electricity, but the metallic oxides do
not Neither does it appear that specific gra^
vity, hardness, tenacity, or crystalline arrange-^

1* ,

42 CONDUCTOmS AND NON-CO ITDUCTOSS.

ment of particles, are connected with the power
of electrical transmission; for similar charac-
ters of this kind are possessed by bodies of both
classes. Thus platina, the densest of bodiei^ is
a conductor ; but so also is charcoal and rarified
air. Carbonate of barytes has great density,
ftnd is a non-conductor ; but dry air, and the
different gases, which are amongst the rarest
forms of matter known, are of the same cha-
racter. Many non-conductors are brittle ; but
iG(ome also are elastic, and others fluid; and
there are bodies of all these classes that are
conductors.

Whatever be the cause of nonconducting
power, it is evident that without its existence
as a property of air, and other substances, elec-
trical phenomena would be unknown ; for if tlie
faculty of electrical transmission existed .uni-
versally, the cause of every effect of this kind
would be dissipated and lost at the moment of
its production. But by the property of non-
conductors any excited electricity which they
surround is preserved ; and it is then said to be
insulated. A support of glass, sealing-wax, silk,
or any nonconductor, is for the same reason
called an insulating mpporty or an insulator ; and

GOKBUCTOES AITP M09f4M>V»91llWOKS. 4S

a piece of metal or^irtber loonductor so support*
^ is named 4# imuktftii conductor.

TbiCff0C0f isndfttors and conductors in prac«-
tiQgJi jl^^GCiw^y may be exemplified by very
jiflspJe experiments, which will form no improi-
per' introduction to the consideration of more
important apparatus.

Experiment 8. Hold a sheet of writing paper
before a fire till it is perfectly dry and warm ;
lay it flat upon a table and rub the upper sur-
face briskly with Indian rubber. The paper
will adhere to the table, and if lifted up by one
tomer and presented quickly to any flat con-
ducting surface, as the wainscot, &c. ^vill be
attracted by and adhere to it. This adhercnce
is occasioned by the attraction of electricity
excited on the paper, which in its dry state is
an insulator or nonconductor; the necessity of
which circumstance to the success of the expe-
riment is rendered evident by the paper falling
down as soon as it has attracted moisture enough
to destroy its insulating property, and is fur-
&er apparetit from the impossibility of produc-
ing the same results by the friction of paper in
its. ordinary state of dryness.
' : Ejpperment9^ Repeat the excitation of the

44 CONDUCTORS AND NON-CONDUCTORS.

paper in a dark room ; when the paper is lifted
from the table by its comer, present the knuckile
of the other hand successively to various parts
of its surface, a series of faint divergent flashes
of light will ensue. This light is occasiqned
by the transmission of the electricity excited
on the paper to the hand; and it ocqurs at every
contact, because the nonconducting power of the
paper preoents its transmission from one part of
the surface to another, the effect existing over
the whole portion that has been subjected to
friction.

Ejcperiment 10. Excite the dry sheet of
paper with Indian rubber, as before, and place
it immediately on an insulating stand. Figure S,
consisting of a round plate of metal about six
inches diameter, supported on a pillar of glass;
Present the knuckle to the edge or under side
of the metal plate, a bright spark will appear;
but a second approach of the knuckle will pro*
duce either a very trivial effect, or none that
is perceptible ; for the metal is a conductor ^ and
transmits the whole effect of the excited electric
at once. Insulated conductors then are em^
ployed in the electrical apparatus to receive
or collect the diffused electricity of excited

XLtCTBICAL APPARATUS. 45

bodies, and to apply it to the purposie of ex-
periment

The atfucture of an electrical apparatus con-
sists in the judicious arrangement of insulators'
and conductors, so that the former shall pre-
vent the dissipation of the effects the latter are
employed to collect or transmit'; thus the cap
and leaves of the gold leaf electrometer form a
conductor intended as a test of electrical action;
but to fit this conductor for its purpose it is
msulated, being supported on the glass cylinder
by which the leaves are enclosed.

When electricity is excited by friction the
quantity of efiect is, within certain limits, pro-
portioned to the extent of the rubbed sufface;
hdice it appears that every part of that surface;
is concerned in the production of the general
efiect. Now, that this may be the case, it is
essential that every part of such surface be in-
sulating; for friction is a progressive process,
a succession of contacts; and the effect pro-
duced by it in the first instant would otherwise
be destroyed by conducting power, before a
aiecond operation could contribute to its increase.
Fot this reason electricity is most usually. ex-
ited ixy the ftSction of a conductor of limited'

4fi ELBCTBICAL APPARATUS.

limited size, against the extensive surface of a
nonconductor.

An apparatus properly arranged for the ex*
citation of electricity is called an electrical
machine. Usually, to excite positive electricity,
a glass tube, about an inch in diameter and two
feet long, is rubbed lengthwise by a piece o£
dry oiled silk held in the hand, which is made
to grasp the tube. In this way both the silk
and the tube are electrified ; but the electricity
of the silk is destroyed by the conducting power
of the hand, and that of the tube only appears.
In a similar way negative electricity is procured
by rubbing a tolerably large stick of sealing-
wax with dry flannel or fur; the electrical
powier of the sealing-wax being all that results.
Thus with the most simple machinery two pro-
cesses are employed to procure the opposite-
eleiptricitiesy although they are both excited
iu each ; but to obtain them both, it would be
necessary to insulate the silk, or flannel, used
as rubbers, either by employing them in a very.
dry state, rolled up, so as to produce the friction'
with one extremity, at a distance from the hand,
or by affixing them to a glass or other noncont
ducting support And neither of these methodf;

would be convenient where many experiments
are to be made. This difficulty does not occur
when large surfaces of glass are employed in*
stead of tubea as sources of excitation ; for
these may be made circular, and proper friction
be communicated to them from a fixed cusbkMiji
on an ; elastic support, against which t)Ml5>' are
made to revolve. There are two fornftlof the
electrical machine constructed on tSiese prin-
ciples, which have each peculiar advantages^
The one was first proposed t>y\Dr. Ingenhouz^
and has been perfected by Mr. Cuthbertson.
The other originated with the German elec-
tricians, and was greatly im.proved by Mr.
Naime.

Mr. iSttthbertscm^s machine consists of a
circular plate of glass, turning on an axis that
passes through its centre; it is rubbed by two
piiks of cushions fixed at opposite points of its
periphery by elastic frames of thin mahogany^
which are made to press the glass plate between
tbem with any required degree of force, by
means of regulating screws. A brass conductor,
siipi>orted by glass, is fixed to the frame of the
aaehine, with its branched extremities opposite
elih Mber, ^and near the extreme diamec<er of

ELECTRICAL MACHINES.

the plate, in a direction at right angles
vertical line of the opposite cushions,
branched extremities of the conductor are fur-
nished with pointed wires, that serve to collect
the electricity from the surface of the exciti
plate. — The machine is represented by Fig. 4.

Such machines have considerable power,
and may be constructed on a scale of greater
magnitude than those of any other form; they
are therefore highly useful when great electric
power is required; but they are seldom con*
structed so as to exhibit both electricities,
cause it Js dif^cult to insulate the rubbers, anj
at the same time preserve the compact fonn
the machine.

The most simple and perfect machine is
presented by Figure 5. It consists of a cylindw
of glass, from 8 to 16 inches diameter, and from
12 to 24 inches long, turning between two up-
right pillars of glass, fixed to a stout mahogany
base. Two smooth metal conductors equal to
the length of the cylinder, and one third of its
diameter, arc placed parallel to it upon two simi-
lar glass pillars, which are cemented into
separate pieces of mahogany that slide acn
the diameter of the base, so as to keep the coih'

ELECTRICAL MACHINES, i 49

ductors parallel to the cylinder while they ari
brought nearer to, or placed further from, its *
surface at pleasure. One of the conductors has
a . cushion fastened to it by a bent metallic
spring ; the surface of this cushion is accurately
fitted to. the radius of the cylinder ; it may be
from eight to ten inches long, and from one

. inch, and a quarter to one and three quarters
wide. To the upper part of the cushion a flap
of thin oiled silk should be attached: it is to
be sewed on the face of the cushion, about a

. qi^i^ter of an inch from its top edge,* so that the
silk at its juncture with the cushion may form
a neat straight line, rising: a little above the
surfuce. The silk flap should, reach from the
cusliiiqnj over the upper surface of the glass
<;ylinder, to within about an inch from a row of
points that are attached to the side of the oppo-
site conductor. • The conductor to which the
I ' • ■ ■ . .

■ I

cushion and . its silk are fastened is called the

negaft^ve conductor, because it exhibits the elec-

-■

. triiqity of the cushion : the opposite conductor
pcillects^and displays the electric poAver of the
f^f^ cylinder, it is therefore called the positive

. Cfl^duptor. ' Each conductor. is perforated in

50 %Lt6tUCJkL UACniJSt^

tariootf putts with holes about the size of a
g^otfe-^ill, for the convenience of attaching
wires and different articles of apparatus; and
tiiiat which carries the cushion and flap has its
diding nmhogany base attached to the bottom
df the machine by an adjusting screw, that
Mrves to regulate the pressure of the rubber
agaittst the glass. The motion of the cylinder
is always in the direction of the silk flap; it may
be communicated either by a simple handle^ or
by multiplying wheels ; the latter produce more
electricity in less time» but increase the labour
of turning.

The facility with which the electric power
of glass is excited varies with the nature of the
surface employed as a rubber. Dry silk is very
efficacious, but the most powerful effects^ are
produced by the use of an sunalgam of tin, zinc^
and mercury, supplied, by means of hogVlard,
to the surface of leather, or oiled silk. The
cushion of an electrical machine is always coat-
ed on the side which performs the office of rub-
ber with an amalgam of this kin^ which should
be spread evenly over its surface until level wifk
the fitte fiMrmed by the seam which joins the aflk

Hbp to the ftce of the eushfoi^: N^ lim^ttpLttL

should be placed over this seam, c^' tm ihk sHk
flip, ^ht6b last should be wiped dean wBeiiever
the coiitmued motion of the machine sfhall
Ikave soiled if, hy depositing ^trst or amalgam
6n *{ts surface. The same attetition is requisite
to fhe surface of the glitss, which often beceimei
xMiNWred with black spots and lines ; more par^
tiwlarly when the amalgam has been recently
aj^led, as they then appear in great abundance.
The*' it is essential to remove as often as they
are formed in any quantity, since they tend to
lessen the power of the machine. The surface
of the Bfiialgamed cushion is also soon soiled;
fbt the excited glass constantly attracts dust
£Fam surrounding bodies, and this dust is wiped
eff by the robber as the glass passes it. If the
dust is removed ifter every course of experi-j
ments, by separating the cushion from the ne^
gative conductor, and gently rubbing its surface
and the surface of the silk flap with a dry linen
cloth) the machine may be kept nearly in uni-
foriff good order, without a very frequent re-
newal of the amalgam ; which is only necessary
when that which has been applied becomes
irregiilar on the surface of the cushion, or im*

5S SLECTRICAL MACHINES.

pregnated with dust from long use, or inatten-
tive cleansing.*

The various articles of apparatus employed
with the machine consists principally of insu-
lating stands or supports, of various forms/ and
of wires and flexible conductors, by which a
proper connexion with either of the conductors
of the machine may be obtained. The applir
cation of the apparatus to the purpose of expe-
riment will best explain the nature of its subor-
dinate parts, and to this I shall now proceed.

* Tlie amalgam I use is made by melting together one
onnce of tin and two ounces of sine, which are mixed, whOit
floidj with six ounces of mercury, and agitated in an iron or
thick wooden box until cold. It is then reduced to very fine
powder in a mortar, and mixed with sufficient hogVlard to
form a paste. Amalgams have sometimes a much larger pro-
portion of mercuT)', but their action is more variable and tnm*
sient j as is also the effect of their partial application to the
iurfiioe of the mathinfe during its action^ as recommended by
aocne electricians.

CHAP. III.

Experiments with the Electrical Machine. — Theory
of its Action. — Phenomena of jdttraction and
Recession.

Xhe electrical machine being prepared agree-
able to the directions in the preceding chapter,
and the cushion pressed moderately against the
glass by the action of its adjusting screw, it may
be put in motion, and the following phenomena
will be observed,

1st. Distinct lines of light, accompanied by
lateral scintillations, pass from one conductor
to the. other across that part of the glass cyliii-
der which is not covered by the silk fliap. These
are called electrical sparks.

2d. Bright sparks pass between either of the
conductors and the knuckle, or any smooth un-
insulated substance presented to them at a mo-
derate distance ; and if received on the knuckle
or any part of the body produce a painful sen-
^tion.

3d. These effects are more distinct, and the
'^>arks from each conductor stronger, when they
ate taken from both at the same time.

54 VHTSOH%SA OF

4th. The power of the spark from either
the positive or negative conductor, singly, will
reach its maximum when the opposite con-
ductor is uninsulated, by suspending a chain
or wire from it to the ground.

5th. If the two conductors are connected by
a wire, or other conductor, the most vigorous
fription of the cylinder will not electrify either.

6th. If, instead of a wire, the conductors
are connected by a ^Ik string on which a num-
ber of shot or metal beads are strung at the
distance of a twentieth of an inch from each
other, a series of bright sparks will pass between
the beads as long as the turning of the machine
is continued.

It is to be remembered, that the conductor
to which the cushion is attached indicates the
electrical phenomena of the cushion, and the
opposite conductor exhibits the electricity of
the glass cylinder; therefore the observation
of their phenoniena is virtually an observation
of the circumstances that occur in all cases
when electricity is excited by friction.

The first and jsecond phenomeiut seem to
.tbfw that ihfi cauw of electricity is corporeal;
jTor Bensstitm^^itJiSfG^ «l jnechani-

XXC1T£D £L£CTfiICITT. $i

i^a} iinpul3e experienced^ wLieh it is d^cujt to
Ascribe to any other than a material cau^e^

The third phenomenon proves that there if
n mutual action between the electricities excited
in the opposite conductors; since their eifecfis
B^eman powerful when directed at the sm» timt
to mKe conducting body.

The fourth phenomdaon shews that the sMm
jpelatioid which is observed between the (jppmtt
electrified conductors exists also between either
i)f them and the ground, but in a different degree.

By the fifth phenomenon it is seen that
positive axid negative electricity^ if excited to the
;same extent, and unifed by amducting matietf
exhibit no electrical phenomena.

The sixth phenomenon is observed merely
to shew tlat when the conductors are connected^
^eonachine continues to excite electricity, but
}s prevented from di^laying it by their mutudl
«axitac&

From the conaideration of these appearances
4b(f^ following explanation of electrical pheno-
4MDft may be rationally deduced.
i« ii.^ . Propositions.
^\^'jMih-Tbt tause of electrical phenomena k
,fikid'. fioaseases the properties of an
Ic fluid.

S6 THEORY OF ELECTRICITY.

Sd. This ekctricjbiid attracts and is attract-,
ed by all other matter, and, in consequence of
"such attraction, exists in all known substances.

3d. The attraction of different bodies for
the electric fluid is various^ and so is that of
the same body under Afferent circumstances ; con«
sequeptly the quantity of electricity naturtilty
existing in different substances may be uneqttal;
and the same body may attract more, or less than
ifalonCy when combined with other matter : but its
original attraction will be restored by destroy*
ing the artificial combination.

4th. From soipc peculiarity in the nature of
the electric fluid, it? attraction by and for com-
mon matter is more influenced by Jigure than
by mass ; and is consequently stronger in ex-
tensive than in limited surfaces.

6th. From the same peculiarity, the electric
fluid moves w^th great facility over the surface
or through the substance of some hollies, and
is arrested in its progress by others.

6t]i. When the attractioi\ of ^y substance
for electricity is equal to. the electric fluid it con-
tains^ that substance will evince no electrical
signs ; but' these . are immediately produced
'When there is either more or less electric fluid

I'HEORY OF BLBCTRICITY. 57

than is stdequate to the saturation of the exist-
ing attraction : if there be more, the electrical
signs will \Hi positive; if few, they. will be nega-
tivei

Electrical excitation then may be thus ef-
fected : — The bodies employed have each a
certain quantity of the electric fluid proportioned
to their natural' attraction for it: this they re-
tain, and appear unelectrified so long as they
l^emain in their natural state. Now if two such
bodies are' brought in contact their natural at-
tractions are altered, one of them attracts more
than in its separate state, and the other less ; the
•electric fluid diffuses itself amongst them in
quantities proportioned to their relative attrac-
titmSf and they consequently appear unelectrified.
But if they are suddenly separated^ the new dis-
4ri^im' of iiie electric fluid remains, whilst the
migkkd attractions are restored, and as these are
fif /cyuo/ to each other the bodies will appear
'electrical t that whose natural attraction was
^JMVMii^^^'' contact, having received an addition
liiW^Aitity of electric fluid, will he positively
dMtnfied ; and that whose attraction was /e^-
't||l|M(^jb»ilftg'^ W a portion, will be negative.^
y i*ji^PljK^*4mn instance^ the electrical machine:

58 THBOKT OF

let the attraction of the cushion for the electric
fluid be represented by SO, and that of a similar
surface of glass by SO, the sum is ^0. Bring
the bodies in contact, their attractions alter;
that of the glass becomes 40, and that of the
cushion is reduced to 10; the sum of these is
still 50 : the natural electricity therefore, though
unequally distributed, is still equal to the sum
of the attractions, and does pot appear ; fbr the
cause of its unequal distributipn (the contaet)
is still active. Separate the glass from tihc
cushion, its original attraction of 30 will now
only operate, but it has acquired 40 of electri-
city by contact with the cushion ; the glass is
therefore positive with a force equal to 10. The
cushion also will now have its original attrac-
tion of SO, but its electricity amounts only tp
10 : it is therefore negative with a force equal
to 10. And here is seen the reason why posi-
tive and negative bodies act more powcrfi»%
on each othex than on indifferent matter, for
their mutual difference is often twice as gsneftt
as their individual ; siace if the latter be 19,
the former may be i20.

The effects now lieaccibed iDontcRiiaUy mcur
dwmg Ae. itnnilotipns ^ the pylsnder^ rvery

THEOKT OF XLICTKlCITri SS

part of which is succeseivcfly brought in cour
tact with the cu&hios, and passes forwafd with
the electricity it thus progressively acquires.
The silk flap may be considered as a continuar
tioQ of the rubber, which, by partially maintain-
ing the altered attraction of the glass, prerenti
the teadeucy of the acquired electricity to pass
back iiito the cushion. The surface of the glass,
vbere it passes from bene^h the silk Awp, has
not this compensatioa; hence the acquired cieo-
tricity is there uncombined, and has a tendency
todifiiise itself amongst the surrounding bodies::
the conductor, with its row of potnt-s, is the
jieareat reservoir, atid into this it passes, and
the conductor become« thereby positiveiy eko-
tr^ed. During this process the cushion and its
attached conductor constantly furnish electei-
xnty to the glass, and tha/ are consequently
negative in the same degree ; but they have
only ^Umttd surfooe, and a certain quantity of
astiinl electricity, and, if perfectly inadaitd,
jfll^rt is, nirfounded by nonconductors) can fur-
iTWifr (T*J ^ de6nite portion ; hut if they iire
, ttBHyifffitfff with the ground, whose surface is
^mparatively unUtmted, they operate upon an
extensive store, to t^ fuppjy of which there

60 TUBORT OF ELECTRICITT.

appears no assignable bound. It is for this rea-
son that the electricity of either conductor
separatefy is more apparent when the opposite
one is uninsulated.

The excitation of electricity thus appears
analogous to the evolution and absorption of
heat : simple mechanical touch is rarely attend-
ed by any perceptible change of temperature,
but such change is usual in cases of chemical
combination. During the solution of many
salts there is an absorption of heat; by the
union of acids and water heat is evolved ; and
by the contact of certain acids with inflam-
mable matter even light and ignition are pro-
duced. Such circumstances prove that some of
the most active powers of nature exist around
us at all times, latent in their natural states of
combination, but rendered active by the slightf-
est change.

Positive electricity has here been considered
as the effect of a redundance of the electric
•fluid, aradvQiegSti^6 electricity as a deficiency :
hence when sparks or other electric phenomena
occur between two oppositely electrified con-
ductors, it is supposed that such appearances
are produced by the elec-tric fluid passing from

THXOET OF XLECTEICirr. 6l

tlie podtive to die negatiye, which motion is
oocasioned by a tendency to r^am its nmtonl
itate of distribution. And on the same principle
the spukM and other effects that take phce be-
tvcen an nnmsuhited and a positiyely electrified
oondnctor are|>resumed to arise from the super^
sbondant electric fluid passing from: the elec*
tiified conductor to the ground; whilst those
vlnch occur between a negative conductor and
the ground result from the passage of the elec-
tric fluid from the latter to the former.

There are certain appearances that demon-
strate ^s direction of the electric fluid with
tdbrable accuracy; and, but for them» it must
have been considered as only a probable sup«
position : for the motion of electricity is too
rapid to admit of the detection of its course by
the eye, unless indeed under very peculiar cir-
cumstances.*

ErperimefU 11. Present a pointed wire to
any n^atively electrified body, — a divergent
peQqil of light will evidently pass from the

• • • -

* With verf Jl^e and powexfal electrical machUief, iparkt
ace spmetiipes procured of from ten to twentjr inches long ;
' AMl'fttidi sj^kft alwajs appear to pass from the posithre to the
n^gaiift, or from, the positive to the receiving btU< ;

(Hi TBBOkr or SLCCTfttofrr.

fK)iiit to tiie electrified sttifaee. Preseiit s sinft-
Itr {xrint to tny posritive ratfic^^-^tbe pomt
witt be iUvmimited by a neat Imlnaous HUtf.
The light m this experiment is^udAfuMtimiaMf
jptoduced by the motion of tiiie ekctrio ItM:
the point h to be condider ed M a pipe CflpaJbfe
of emitting of receiving it, and fhe dppearaneei
correspond with the supposed cMVSe 6f'tbt
electri^ty : for the mgative surface icr stated M
hanire a dejkiency^ and the point presented to it
is illuminated by a Soergent pencil, whieh indi^
Gates Aiat the cause of that light moves ^^tm
the point to the negative body. The poMtt
sarface is said to have an excels of electri<^ fltii^
and the point presented to it is merely illnmi*
nated by a globular sp&t of light, an appearance
whii^ may well be conceived to attend the m-
trmice of a subtle fluid into it.

If the points are connected with the oppo^
sitely electrified bodies, their appearance is pre-
eiwciy the reverse of that which occurs wheA
dMy we pf€mkted to them ; and such should bt
the case if the preceding supposition be correct

Et^imnt 12. Fig. 6L represents two Bol-
][0W metal balls about three-fourths of an inch
diameter, imsukCed on sepaiMe glass pillarft byr

vhidh tb€^ 4f e t^j^ort^d at two inches aput ;
^e ttf|ifyeF part of each ball 19 indented to Idtm
a sfttall cup in which a fragment of phosphofui
i»'to be placed. A smalt candle Or lamp hai iti
flame' situated mid- way between the baUs^ one
of them is connected with the positive an4 the
Otii« With tht negative conductor of the A^C*
ftical machine by means of a wire« tVbeli the
baUe are electrified, the flame is agitated^afid ifl^
oHiieB to that which is negative ; this it soon
heats sulfficiently to fire the phosphorus it COft*
taiins ; whilst the positive ball remains perfectly
eoUi^ and its phosphorus unmelted. If the
c<MiiieGting wires be now reversed, 1^0 that the
ball which was^ negative shall become positive^
and that which was positive be rendered nega^
tiv^ the phosphorus in the lattef will soon take^
fire. So that electricity passes from tki positive
ti^ the ftegaiive, and transmits with it the he^t of
«iiy kitervening ignited body.

Eseperbnmt 1 S. Take the transfer pkte of
aa air-pump^ and affix to its centre^ by a wire off
1|iree inches^ long, a ball of an inch in diameter;
oranect a similar ball, by a sliding wire, tO thi
Wp of a peeeiver, and pla^e thia c^vei" the tm»^

pitterjK) that the b«B# May foe of^tte^ te^eiiiAi

64 TH£OBT OF ELECTB1C1TT4

ptheri and at the disttoce of about an inclv-r
lee Fig. 7. Exhaust the receiver accurateljr by
s^eaus of an air-pumpi connect the pump plat^
by a wire with the negative conductor^ and the
upper wire and ball with the positive. When
the i^achine is turned/ a current of beautiful
purple light will pass from the positive to the
O/egi^tive ball, on, which it breaks and divides
ililtoia. luminous atmosphere entirely surround*
ing ;the lower ball and stem, and conveyiqg
xooa^t strikingly, the idea of a fluid running over
the.surface of a resisting solid which it; cfinniot
enter, with facility. No appearance" of light
o.ceuTs on the positive ball, but the straight lu-
minous line that passes from it : , but if itih^ ttnr
dered negative,, and the lower ball positive, these
effects. are entirely reversed.; . . . /. -

'^ When this experiment is made with due care,
it; furni^hes^ a. most satisfactory ocular demonr
stration of the course of the electric fluid; aad
few.^who witness it under such circumstances
¥l^j entertain any doubt on that subject. .
: , Electrical phenomena then are produced, bf
the iDotion of a naturally diffused fluid, which»
|>y certain processes, may be accumulated in soai^
Ijodicana^d ^Ojfaj but, tendiDg coor

:^0SITIVS Ayt) NEGATIVE ATTKACTIOK. 6^!^^

stantly to an equilibrium, will, if unobstructed^
restore its original difFusidn by passing y}*em
those that have a redundance to any that ate'de-
ficicfnt ; or, if none of these are near, to such as
have only their natural quantity.

Positive and negative are merely compara-
tive terms, expressive of different variations
from the natural state. There are two stand-
ards to which, under different circumstances,
these states are referred. When the effect is
measured by the divergence of pith-balls or
other light bodies suspended in this atmosphere,
the anibient air becomes the standard of plus
and niinus, these states being then only indi-
cated by the balls in proportion as they actually
differ from it; and, as the air is a nonconductor,
it may be considel*ed as insulated. But if any
substance connected with the ground be pre-
sented to an insulated electrified body, then the
ground becomes the standard by which the

■A ' .

positive or negative divergence of that body is
measured. Hence the standard is called a neutral
point, and all bodies having only their natural
quantities of electric fluid may be^egarded as
such ; and, although actually iinelectrified, are to
be considered positive when compared with such

66 KATUBB OW POSITIVE AND NSOATIY^

M have less than their natural portion, and n^;a>«
iive when opposed to those that have more.

The motion of light bodies produced by
cleetricity, and usually called attraction and re*
pulsion, is occasioned by the mutual attractkm
existing between the electric fluid and common
matter. Its nature will be best understood by
reference to experiment

Eaperment I4i. Take a small downy feather,
or a pitb-ball suspended by a metal thread (such
as ia used for gold lace), and hdding the thread,
bring the ball near any electrified conductor,
cither pointive or negative : the ball will be at-
tracted by and adhere to the electrified con-
ductor, and will remain in contact with it until
its electricity ia destroyed.

Such bodies as Biepasitheb/ electrified, tend
to diffuse their superabundant fluid amongst
surrounding substances; and those that are
Wigatwe^ endeavour to acquire electric fluid:
hence either state of electricity will produce
attraction ; for if light bodies are to be movedi
it ia indiiFerent whether the electrified surface
attracts their natural ekctrk Jhiid^ or the mattef
to which it is attached ; for the attraction arises
only from the d^erent proportions of these in

A*rftAe«ON AND EECisSWK* '6t

ibjtzpo bodies, and will of course tontinut whilst
that dijference exists. Now, in the preceding
experiment, the attracted body was in conduct'^
ing communication with the ground, and the
electrified surface, b^ing comparatively of
limifed extent, could not perceptibly alter the
electric state of the whole earth, the attrac-
tion must therefore continue until the elec-
trified body has received from, or cofiimuni-
^ted'to, the earth such a portion of the electric
fluid ais it is deficient in or overcharged with ;
and, consequently, till all ekctrkal difference

between the earth and it is annihilated.

^^ ('

" Experiment 15. Repeat the preceding ex-
^Hment with a ball or feather supported by a
silk thread : the light body will first be attracted
to the electrified conductor, and will then re-
ctdi &om it ; nor can again be brought in con-
tact until it has touched some uninsulated con-
diidtmg substanccf.

• The light body is here attracted for thti sathe
reason as before^ but it is insulated, and con-
sequently receives, by contact with the elec-
tiified surface, B:sinnlar electric state; it there-
fore recedes from that surface, being attracted
by ihf^ ambient air, or other surrounding bodies,

Fi2

68 VATUU: or positiv£ and negative

for thof have their natural portion of electricity,
.and therefore differ front the light body, which
has either more or less; but the electrified sur-
face does not differ from the light body, and,
C9n^quently, cannot attract it, till, by touch-
ing some uninsulated conductor, its natural
electric state is restored.

■ •

. . From these experiments it necessarily fol-
lows, —

1st. That bodies positively/ electrified in the
same degree will recede from each other i their
plus electric Jkdd being attracted by the ambient
medium, which is in its natural state.

. . . Sd. Negative bodies of equal power will re-
cede from each other, their matter having an
attraction for the mtural electricity of the sur-

rounding medium.

. Sd, Bodies electrified either positively or ne-
gatively, in differetit degrees, will be mutually
attracted, until their relative proportions are
eqmUzed^ when they will recede from each other
and tend towards unelectrified substances.

4th. Positive and negative bodies will reci-
procally attract each other, and, if of equal in-^
' tensity^ be unelectrified by contact.

ATTRACtlON AMD RECESSION. ^

5th. Such as are positive and negative in
Afferent degrees will attract each other, tod re-
main electrical, after contact, in proportion as
the sum of their electricities may deoiati firom
the state of the surrounding medium.

Hence we may conclude, that when any two
substances recede from each other, they are
simlarfy electrified ; and when they attrdct each
other, they are oppositely electrified.

• By the operation of these principles a variety
of entertaining experiments may be made ; for
light substances pkced between differently
electrified conductors will move from one too
iSht other, and by suph alternate motion produce
wm^ lingular results.

In the following experiments, which arc
common illustrations of electric motion, the
teoving body is dways pituated between an
electrified surface and one that is in communi-
cation with the ground ; it is first attracted by
the electrified surface, because H is i^ a different
state; by contact its electricity becomes the
Mme, and 4t is then attracted by the Body in
connection with the ground ; it touches that^
has its natural electricity restored^ and is thei)

79 ILECTRICAL I^S^FSRf MI^NW*

Tfsattrtcted by the electrified surface, ' beooines
agaiii electrical, and recedes to its original sitOr
aticm, whence it is agaiii attracted, fcc. md ibin
motioQ muf t necesss^rily continfie fmtil the i^
ferenf electrical states of the two surfaces ^e
equfilhfd and rendered simUar. Lig)it substances
mdved by electricity may therefore bo ^HUf
der^. as v^hicle^ of transfer, pmv(^fvm thf
electric fluid ffom one systetn .pf ^KHljes t9

amfttb^ri jwjd thus prpwoting ^te fiatnml diitri-
iriitipit

M^fpwimmf 16* Place a leaf of gpld, sar er,
or Dutch metal on the palm of tlsif h«n4' Ml4
bring it MTithin a few incbe* of mi elecJtHiffd
conductor; it will be attracted and eonliiHif' t9

movci alternately from the hatid to ^o oon-
ductpr, as long as tlie latter i9 electrified.
E3tp0rimwt \7, Suspend a bra^s plate firom tb?
4{onduetor of ^m electrical machine, and benetfli
it, at the distance of three or four inches, pl«e$
n similar brass plateiconnected with the ^rqnnft
fOn this put some small figures cut in paper;
whel) t^e upper plate is electrified the fignres
iriU rise and perform an electrical dance by thwjr
moitioft between the phttes* i

Experiment 18. Place a pointed wire on the
machine, electrify the inside of a drj glass ttttti^
bier by holding it over the wire Wlnllt the
machine is in motion ; place some pith balls on
the table and cover them with the electrified
glass; they will be alternately attracted by it
and the table, and continue their motion foi
some time«

• Eitperinmt 19* Insulate two small bells on
separate glass pillars, at three-fourths of an inch
distance from each other ; suspend a clapper by
a silk tiiread so as to hang midway between
them ; connect one of the belU with the coii<^
dttctor of t2)e machine and the other with the
ground; the clapper will vibrate fVom one to
die other during the action of the machfoei
producing an icleetric chimet
, JE^feriment 20, Insulate a circular ring of
brass so as to stand near an inch and a half from
the flat surface of a table; connect the brass
ling with the conductor of the electrical mii«
chine, and place within it, on the table, a very
light and round glass ball of two inches diame<i»
ter; the ball will be attracted I^ the ling*
touch it, and become electrified at the point of

72 ELZCTltlCAL EXPERIMENTS.

contact; this point will then, recede and be at-
tracted by the table, whilst another part of the
bqiU M attracted by the ring; and, by thie repe-r
titiQn.Qf this process, the ball is made to revolve
aiid travel round the circumference of the ring.
This phenomenon depends on the nonconductr
ing power of the ball, which confines the effect
of contact to a limited portion of its surface,
different parts of whiph are consequently vari-
pi}$}y..e}6C|t|*ified 4t the same time.
/ These phenomena of electrical motion, which
«je all referred to the same principle, certainly
eiYWcc the materiality of the . electric : fluid,
which; here,, by its attraction, displays one of
the. most essential . properties of matter, and
eyw : counteracts : the effects of gravitation^
The separation of .the parts, of similarly eleo?
trified; bodies confirms the preceding evidence,
9£[ will appear by the following illustrations. . .
EA^iment 2 1. ; Connect a pith-ball electro-
meter with each conductor of an electrical
machine,: both, remajning insulated;, when the
inachine is turned, each electrometer will di-^
verge, for th?y both diflfer from the surrounding
i|ir (one having more electric fluid and the

ELECTRICAL EXFERiMEKTS. 7$

otbcE less) ; connect the opposite conductors by
a wire, the divergence will cease, for the elec-
trical difference of the conductors and the am^
bteht air is destroyed,

. Experiment 252. Take a dozen threads and
jde them > together at top and bottom; annex
theoi (by a loop attached to the upper knot) to
4^e conductor of the electrical machine; when
electrified the threads .will sepai-ate from each
Other, and the knot at the bottom rising they
sirill assume a spheroidal figure, which will con-
tiaii^ as long as they are electrified. .
' Sujcpi^rirntnt 23. Insulate a condensed air-
fountainy and electrify it; the jet will be mi-
nutely subdivided and expanded over a con-
^idexable space, but will return to its original
Jiqiit wlieii the electrization is discontinued.

^J^^pptTxmmt. 24. Fasten a piece of sealing-
wax to a wire, and insert this in one of the holes
iOi . th^ : conductor of the electrical machine ;
soften the ^e^ling-wax by heat, and whilst it is
$tiU soft. turn the cylinder; very fine threads of
iWftx will be. separated^ and if received on a sheet
of^ paper will cover it with minute fibres like
fine red wool.

ir4 SLECTKICAL XXPEEIHENTS.

Experiment £5. It will be shewn hereafter
that pointed bodies transmit electricity with
greater facility than such as have blunt or
rounded terminations; hence, if any electrified
conductor have points on its surface, the air op-
posite those points is soon similarly electrified,
recedes from them, and is replaced by other \xb^
electrified particles, which also become electri-
cal and recede ; so that a current of air is con*
stantly produced by an electrified point, and
appears to issue from it, whether the point be
positive or negative. On this principle various
revolving motions are produced. Fig. 8. repre-
sents a wire cross with pointed extremities bent
in one direction ; when this is balanced by its
centre on a point, and electrified, it turns swiftly
round in the contrary direction to its points ;
the reaction of the air against the currents they
produce being the cause of its motion.

Light models fitted up with vanes, like the
floats of a water-wheel, may be put in motion
by the current of air produced by the action of
an electrified point ; and if a lighted candle be
presented to such a current, its flame will some-*
times be blown out.

ELECTRICAL BXPERIIIINT9* 75

Such are the principal phenomena of motion
produced by the action of electricity ; they are
susceptible of almost unlimited variety, but
uniformly result from the simple principles al-
ready stated, namely, the attraction of the elec-
tric fluid for common matter; its tendency to
equal difRision; and the occasional interruption
pf these properties by noncon^uctingpower an4
altered force of attraction.

' V

CHAP. IV.

On the Phenomena of Electric Light

The luminous appearances produced by clec-
tricity e:^hibit considerable diversity; it is

therefore necessary to consider them with at-
tention, and compare the circumstances of their
production with the general principles of elec-
trical action.

Light is not constantly attendant on the
excitation of electricity, but appears when that
process is vigorously performed, and is then
brilliant ii^ proportion to the intensity of the
excited electricity.

Suppose JO particles of electricity to be
added to or subtracted from a body whose na-r
tural attraction is for 35 ; the electrical differ'^
ence between that body and the substances (in
their natural state) by which it is surrounded
will be 10; the intensity of its positive or nega^
tive state may be then expressed by 10. If the
alteration in its natural quantity be now made
equal to 20 particles, its electrical difference

•

. ^tECTRJC LIGHT. 77

will be twice as greats and it will thierefore have
double ih^ intensity ; so that this term in elec-
tricity is employed to express the greater or
less deviation of any electrified body from the
standards of plus and minus. "^

The light evolved in ordinary cases of exci-
tation extends only to faint flashes and scintil*
Utions, sparks being only produced when these
effects are concentrated, as they are in the elec-
trical ^machine by the action of its conductors.
The spark in passing from one body to another
is influenced by the form of the conductors^
their extent, and the nature and density of the
medium through which it passes: it will be
necessary to consider each of these separately.

The distribution of electricity on conductors
has evidently little relation to their solid con-

* The elasticity of the dectric fluid admits the arrangement
of more or less particles in the same space, and its intensity or
tendency to an eqailibfiam will be proportioned to the quantity
accumulated in any given surface, or to its density : this corre-
sponds with the action of other elastic fluids ; air^ for instance,
of itrch density as to support a column of one inch of mercury^
will, sustain two inches when compressed into half its original
spacej and only half an inch when expanded to twice its original
bdlk^ and will unite with water or other liquids in quantities

.proportioned to its density. Positive and negative electricity

^^^aqatogQUsW'Condensed and rarified air.

78 EFFECT OF POIKTS.

tents, but depends almost entirely on svktfactf
for the same effects are produced by the thinnest
cylinder or sphere of metal as by the most com-
pact solid body of the same form and dinien*
sions; it is indeed even probable that the action
of insulated conductors consists in the ready
communication of their electric state to the con*
tiguous surface of the extensive stratum' of air
by which they are surrounded, and to the iaci'
lily they present to the discharge of that elec-
trified stratum when an uninsulated or differ-
ently electrified body is brought near them';
for every positively electrified conductor is sur*
rounded by a positive atmosphere, and evwy
negative conductor with a negative atmosphere
whose densities decrease as the square of their
tilCreased distance. Hence any insulated elec-
trified body will retain its electrical state until
its intensity is sufficient to overcome the resist-
ance of the air (which is the medium by which
4t may always be considered as separiated from
uninsulated or differently electrified bodies),
and the greater or less interval through which
the spark passes is called the striking distance.

When the surface of the conductor is uni-
form, the reaction of the air around it is also

EFFECT OF POINTS* 79

uniform ; but if the surface of the conductor be
irregular, the tendency of the electric fluid to
escape or enter will be greatest at the most pro-
minent parts^ and most of all when these are
angular or pointed. To understand this it is
only necessary to recollect that every electrified
conductor is surrounded by an atmosphere of
its own figure^ the contiguous surface of which
is simikurly electrified : and that electricity is
nU transmitted through air, but by the motion
of its particles. For this motion of particles is
resUted by a uniform surface from the similar
action of the air around it, which is all equally
capable of receiving electricity, and cannot tend
t# distribute it in one direction more than an*
otbeir; the immediate electrical atmosphere of
ttkt conductor will be therefore resisted in any
attmnpt to recede from it by a column of air
which is equally opposed in every part ; but if
tflber« be any prominent point on the conductor
pnojecting into the atmosphere, it will facilitate
tile recession of the ekctrified particles opposite
to it by removing them further from the elec-^
tarified surface, and opposing them to a greater
mmAer of suet as are tmelectrified.
,. The action of pointed or angular bodies con-

80 EFFECT OF POlNl'8-

sists then in promoting the recession of the pnt-^
tides of electrified air, by protruding a part of
the electrical atmosphere of the conductor into
a situation more exposed to the action of the
ambient unelectrified medium, and thereby pro-
ducing a current of air from the electrified point
to the nearest uninsulating body. Hence the
most prominent and the most pointed bodies are
such as transmit electricity with the greatest
facility, for with them this condition is most
perfectly obtained.

A spherical surface is that which, considered
with regard to its surrounding atmosphere, is
most uniform; balls, therefore, or cylinders
with rounded ends, are usually employed for in-
sulated conductors, and their magnitude is pro-
portioned to the intensity of the electrical state
they are intended to retain; for a point is vir-
tually a ball of indefinite diameter, and will in-
deed act as such with regard to very small
qujGUitities of electricity, and a ball of moderate
size may also be made to act as a point by elec-
trifying it strongly.

If two spheres of equal size are connected
together by a long wire and electrified, their
atmospheres will extend to the same distance

zivZCt OF I»QINtS. SI

. ■ . • ...

and they will of course have respectively the
same intensity ; but if the spheres be of unequal
size, the atmosphere of the smallest will extend
furthest, and it will necessarily hive the greatest
intensity ; so thjlt a longei* spark can be dhtwn
from a small ball anneiced to the side of a con*^
ductor than from the conductor itself, and
loliger in proportion as the ball projects further
from the side.* Hence the finer the point,
and the more freely it projects beyond any part
of the conductor to which it is- annexed, the
more rapidly will it receive or transmit elec*
tricity. M. Achard found that a single pointed
wire, screwed in the centre of a circular piece
of brass one mch and a half diameter, produced

a greater effect in transinitting or receiving

.■•■*.

' ^ 'Mr. Caveodish^t Cou1onnb>t Laplace, add Poiison,( hare
invcstigaied the ratio of electrical iDtensity on the aorface of
different conductors; each analysis involves an hypothesis^ but
that of Mr. Cavendish appears to me roost rational, alfhdugh
sefonal clrcamstances exist that preclude an accnnrte ezpcriooeii*
tal demofistnition : it is indeed probable that the intensitiei are
in the inverse ratio of the sur&ces 5 proceeding from a flat iur-
fice where it is least, to a point where it may be ^bniideted aa
iafinite.

f Phil. Tram. vol. Izi. p. 034. &c.

X Acad, dct Sciences, l7ta> 1787, 17M9 I7a9.

i Meokilies de rinstitnty 1819.

<•

88 fLECTRIC SFAEl^.

electricity than nine similar points screwed into
the same base, the proximity of the nine points
PfTcasioning them to act nearly as one conduct-
ing surface of the same area.

By inserting a fine point in the iixis of a ]Large
hf ass ball, from beneath the surface of which it
may be protruded more or less by the action of
a^e screw, the effect of a ball of any size may
be obtained : when beneath the surface of the
bfdl the point does not act, but in proportion
as it is protruded it increases the transmit-
ting, powerj andj^ if projected far enough, a^
length entirely overcomes the influence of tfacf
balL

Frpm the probable law of electrical distri-
bution, stated in the preceding note, it follows,
that the larger any insulated conductor may be,
the greater will be the electrical charge it re-
quires to pass through any given striking dis-
tance : hence very different effects are produced
with the same electrical machine, when the size
of its conductor is varied ; and hence also sparks
of the same length, taken from different sized
conductors, must vary in Jbrcey as they do in
fuantity, of electric fluid. Very long and ex-
tended conductors give shorter sparks than such

EUCTRIC SPAftK 89

as are more compact, but ihey are sometimes
more powerful.*

' The following are iUustrations of tiie in*
fluence of the farm and extent of the conductor
on the apptttrancebf 'transmitted electricity;

'Esperiitant^S: Pi^esent a brass ball of thre^
inches diameter to the positive conductor of a
powerful electrical machine; spstfks of brtUianii
white light will pass between them, accompanied
by aloud snapping noiisie: to produce theses
sparks in rapid succession the ball mxUlt be
brought near the conductor, and they then ap*
pear perfectly straight ' '

Experiment VI. Annex a ball of an inch and
a half or two inches diameter to the conductor,
soastd project three or four inches from it;
present the large ball to this, and much longet'
sparka will be obtained than from the conductor
itself, but they 'will be less brilliant and of a
siginigform; ^ ' ■ v,, ■

'i-

.* i/k. Brook* of Nor vicb/ formed a txMott extennve con*
doctor of many long metal rods, jMispeoded bji^laga sticka from
hia oeUingy and connected together nearly in theform of a grid-
inn r with thb apparatut the sjparks, though thorter, were muck
ffloie painful than those from a conductor of five feet lo^ and
ive Incfi^ cB^eter, dm^ed I7 thd same (Tliodef.

14 XLICTftIC 8PAlt«

■■ Eaferkmnt S84 Substitute a small ball for
^t attached to the conductor in the fonaer
experiment; the electric fluid will now pass to
a greater distance, but in the form of a divided
brush of rays/ but faintly luminous^ and pro*
ducing little noise : this brush will eVen occur
with larger balls, if the machine be very power*-
ful ; it is most perfect when procured by pre*
denting a flat imperfect conductor, as a piece
of wood 01^ paper, or thie crown of a hut^ instead
of the large ball

If, instead of a ball, a sharp point be affixed
to the conductor, no sparks can be procured
from it, but a divided brush of. rays more.minute
than that in the preceding experiment will ap«
pear; and the electricity will bo-transmitted; to
a greater distance.

If the uninsulated body on which the sparks
are received have its surface varied, the same
diversity of result is obtained as by changing
the surface of the conductor.

Experimaia S9. Whilst a current of sparks
are passing between a large ball and the con*
ductorat the distance of an inch ai^ a half,
piresent a sharp point at twice that distance,
aQd the sparks will immediately cea;Se, the

mtVCTKJt SPABX. 85

electric fluid . being silently transmitted by the

point. ;.. .

^Experimmt 30. Enclose a point in a glass tube
so that it may be placed at any distance from
one of the open ends of the tube; in this situ-?
ation its influence as a point will be destroyed^
and it will transmit electricity by sparks as a
balL The power of a point is also destroyed by
placing it between twQ balls, or in any way prci
Tenting its free and prominent exposure^

E:^erimefU 31. InsuUte a smooth metal cup
with rounded edges, and in the. cup place a
quantity of smooth chain, free from sharp, edges
or points; let a silk thread be attached to one
end of the chain, and passed Qver a pulley on
the ceiling, so that the chain may be raised, out
of the cup at pleasure ; attach a pith-ball eleor
trometer to the cup and electrify it; raise, the
chain from the cup, and as it rises the diy^rr
gence of the electrometer will dim wish i^. lowei:
the chain,, and the original divergence; will be
restored. The cup and the chain form togethei;
a conducior^ whQse surface is. increased by raising
the chain, and this increased surface dimimshes
the intensity of its electricity by piresenting it
to a more extenswe surface of unelectrified air«

S6 EUCTMC 8PAKK.

. . If this experiment be made jwith ml cup; and
chain of sufficient magnitude, well insulatedy
sparks may be employed as the test, and ^uy
will be most powerful when the surfaoe bJcast
extensive.: . -^i.

Electrical sparks are more.biailiant in pno^
portion as the substanees between whichi they
occur are better conductprs ; hence metala ace
almost exclusively employed for. this , purposCi
wood and other imperfect conductors, produoiiig
qnfy faint red streams; yet these substances act
as points with some efficacy^, and pai'ticles Qf
dust which collect around the apparatus are
often troublesome to electricians from the same^
cause. . .

Electricity is not less affected hy the natiue
imd density of the medium through which it
passes, than by the extent and figure of the trans-
mitting conductors ; usually its brilliance and
force are proportioned to the density and non-
conducting power of the medium in which, it
€>ccurarand hence -^ it has be^ conjectured by
Morgan^* and by Biot;t that light is extricated
from those mediums during tlie rapid, passage'
of the electric fluid by its mechanical compres**

* PbiL Thdnu toL Ixxt. p. ipS..

t Aonalcft de Chioue. vol, liii, p. 321.

ILECTItlC SPARK. S7

sion of their particles : an idea weU supported
l^ most of the experiments yet made on this
subject

The various forms of the spark proceed from
the different modifications of the powers by
which it is produced ; namely, the velocity and
i^uantity of the electric fluid, and the density
and insulating power of the ambient medium :
in the open air long sparks arc always crooked,
for the electric fluid moving with great rapidity
tondeHsfes the air before it^ and is then resisted
in that direction more than laterally ; it changes
its course, condenses the air in a new direction,'
is resisted, and again turned aside ; and this al-
temaite deflexion produces the zigzag appear-
anoe* When the interval is short the spark is
uguidly straight; or slig;htly curved^ but its ap^'
pearance^ is irregular; sometimes broken or in-
terrupted iti diflerent parts, and mostly redder
and less briiliaht in the middle than at the ex-
tremities. It is probable that these irregularities
arise principally from the heterogeneouai nature
of the atmosphere, for in a vacuum the short
Imparks are uniform, and the long ones rarely
deflected.

For experiments on the influence of different

8S BLECTfilC SPAR^;.

gaseous mediums a simple appa^ratus is requi}^;
a globe of glass about four inches cliameter, havT
ing two necks capped with brass ; to one of th«
pecks a stop-^pck is screwed, M^ith 4 wire, and
b^ll projecting intq the globe, another ball .19
attached to a wire that slides through a Cpllaj
of leathers screwed to the opposite qa:p, so thsfct
tlie b^l3 may be set at any required distance
from each other within the globe. — See Fig, 9,
This apparatus may be exhausted of air by. con^
necting the Sitop-cock with an air-pumpi an4
different gas^s piay be thus introduced into it,
or the W it contains may be rarefied or con-
denied, and th^ effect of tl^ese processes on the
form of the spark examinedt Ixi condeq^ed ai(
the light h white ^d brilliant ; iq rarefied aift
divided ^nd faint; aqd iq highly rarefied air, of
a dilute red or purple colour. The effect of
gases appears to be proportioned tp their d^n?
sity ; in carbonic acid gas the spark is white and
yiyid, in hydrqgeq gas it is red apd faint.

In proportion as the rarity of any mediyn^
is increased, a leas intensity of electricity is rert
quired to render it luminous : this fact may bQ
illustrated by a very simple apparatus.

J^spcrinifnt 3$. Seiil » short irpn or pl^tina

EtECTKIC UOHT. 89

Virc within one ^j^txemity of a glass tube of 30
iacfaes long, 30 that the wire may project a little
within its cavity, and scr,ew a^ ball on the ex-
ternal end of the wire ; fill the tube with quick*
ailyer, and invert it in a bason of the same; a
vacuum will be formed in the upper part of the
tube, which will occupy most , space when the
tube is vertical, and gradually diminish as it is
inclined; a spark which in the open air would
pass through only a quarter of an inch, will p^r-
yade, six inches of this vacuum with facility ;
Snd if the quicksilver be connected Avith the'
ground, a current of faint light will pass through
Jthe upper part of the tube whenever its ball is
brpvtght near ap electrified conductor. If, pre-
vious to the inversion of the tube, a drop of
>mter pr of pth?r be placed on the mercury at the
open end, and secured by the finger whilst the
tube is inverted, it will rise to the top, and when
the finger is. removed apd the quicksilver de-i
scends, the ether or water will expand and'ex?
tend the yaciium, s^d through this; expanded
yapour a current of electricity will become lu-r
minous, and of various colours in proportion tq
jts intensity; wheu the spark is strong, and

90 KLICT&IC LiOHT.

passes through some inches of the expaAdicd
ether, it is usually of a beautiful green colour.

Experiment S3. Take an air-pump receiver
of IS or 14 inches high and 6 or 7 inches dia-
meter ; adapt a wire (pointed at its lower ex-
tremity) to the top of the receiver, letting^ the
point project an inch or two into its inside J
place the receiver on the plate of the air-putbp,
and electrify the wire at its top positively;
whilst the air remains in the receiver, a brash
of iight of very limited size only will be seen*
but in proportion as the air is withdrawti by the
ibction of the pump this brush will enlarge, vary-
h)g its appearance and becoming more difiused
as the air becomes more rarefied ; until at length
the whole of the receiver is pervaded by a beau-*
tiful blush of light, changing its colour with
the intensity of the transmitted electricity ; and
producing an effect which (with an air-pump of
considerable power) is pleasing in the highest
deg^jee.

Even good conductors of electricity are
rendefed luminous by its passage through them;
if they have sufficient tenuity.

Experiment 34. Insulate a large brass hA\

XLECTRIC LIGHT. gi

«id connect with it a silver thread of twO: or
:three yards long, the other extremity of which
is lield in the hand ; when sparks ate made to
ttkike on the brass ball^ the whole of the thread
wilL be. rendered faintly luminous. •
-> The electric spark, viewed through a prisnft^^
exhibits all the prismatic colours, and is analo^ *
gcno^^o solar light in its power of displa^ying
tiiem sefiarately by the intervention of different
media; this is well exemplified by a very simple
mmgement.--

-'i E^eperimMt 35. Take a piece of soft diM^
about three inches long and anonch and ^ half
Mpuur^; insert two pointed wires obliqiiely into
it* surface at an ineh> and a^ half distance from
4ach o^efy and to the depth of to eigh& of an
incA; the wires should incline m oppoaite) d)^
«ecti<mt> and the track between the points be iidi
that of the fibres ; a spark m passing -inftm^ one
^Bt to another through the wood* will ;as(sttm^
difitnrent cok>u7s in propoi^tion as it ^passes moi^e
oi". less below^ the surface ; and by inserting on6
poiBt deep^ than the other^ so that* the qiark
may pass obliquely through difiereht depths
all t^e colours may be made to appear at once.
Sparks taken through balte of wood or ivory

92 ELECTRIC LIGHT.

appear of a crimson colour; those from the sur-
face of silvered leather are bright green ; a long
spark taken over powdered charcoal is yellow';
and the sparks from imperfect conductors have
a purple hue. The quantity of air through which
these sparks are viewed also influences their ap-
pearancie; for the green spark in the vapour of
ether appears white when the eye is placed
close to the tube, and reddish when it is viewed
from a considerable distance.*

Metallic conductors, if of sufficient sizey
transmit electricity without any luminous ap-
pearance, provided they are perfectly continu-
ous ; but if they are separated in the slightest
degree, a spark will occur at ievery separation ;
on this principle various devices are formed^
by pasting a narrow band of tin-foil on glass in
the required form, and cutting it across with a
pen-knife where sparks are wanted to appear,
(the pen-knife should be passed twice over the
strip of tin in opposite directions, as if to form
the letter X, which will take out two conicid
pieces^ and leave a small and well-defined sepa-r
rafion). If an interrupted conductor of thi$
kind be pasted round a glass tube in a spiral

* Morgan's Lectures, p.-^ai.

'dixectioii^.and one end of the tube be held in
the hand and the other presented to an electri-
fied, conductor, a brilliant line of light surrounds
the tube,, which has been hence called the spiral
tube, or diamond necklace. — See Figure 10.
By enclosing the spiral tube in a larger cylinder
of. coloured glass, the saphire, topaz, emerald,
and other gems may be imitated. Word?, flowers,
.and other .complicated forms are also procured
nearly in the same manner, by a proper dispo^
sition of an interrupted line of. metal on a flat
piece of glass, as may be seen in Figure 11.
Indeed the tendency of the electric fluid to
evolve light when it passes from one conductor
to another is such that even their apparent con-
tact does not entirely prevent it, for a chain
will become luminous at every juncture of the
links when an intense spark is passed through
it The light evolved by the action of a powerful
electrical machine is so considerable, when a cur-
rent of sparks are taken between two large balls,
as to enlighten the whole of a very large room,
80 that the objects it contains may be distinctly
perceived ; and with a cylinder machine of 14
inches diameter, I have occasionally illuminated
nine ^t of spiral tube, in which the electric

ELECTRIC LIGHT.

fluid becatbe luminous at near eight hundred
distinct separations.

Such are the principal phenomena of electric
light; they are certainly conformable to the
idea that it results from the mechanical action,
of the electric fluid on resisting mediums; but
\fbether^ the light evolved is to be considered
as a component part of those mediums, or of
the electric fli^id itself, these facts afford no data
to.det^rmiiie«

• «

» ^

i.1 ^ .

• ■ • t » '

t »

CHAP. V.

On the Lofden Jar, and tkf Nature ofEkctrical

Infiuence.

Xhh sources of . electrical accumulation yet
described consist of excited bodies and insu-
late conductors ; and in the preceding chapter
it has been shewn^ that the form and arrange*
ment of these last influence very materially the
appearance of the electricity they convey.-^—
When, an electrified conductor has its surface
amended, its intensity is diminished i and as this
exjtension is yirtuajiy an exposure to a greater
suiface^of tmelectrjfied air^ it might be expected
that a ;simil£^r effect would be produced by apr
pro^simating the conductor to the ground^ or to
any other body of sufficient magnitude^ in its
natural electric state; and such is. really the

case.
, M^^itnent i6. Insulate a flat metal . plate

with jsmooth rounded edges^ and connect with
it a pithrbaU electrometer; electrify the plate
either positively or negatively, and the balls
VJ3^ ^diverge.: bring: a similar plate unmsuhied

96 THE L£ri>EK JAR.

near that which is electrified, keeping their flat
surfaces parallel and opposite to each other ; the
balls of the electrometer gradually collapse as the
plates approach^ and when they are within about
half an inch of each other, the insulated plate
appears unelectrified; but on the removal of the
uninsulated plate the original divergence is re-
stored.— See Figure 12.

When the insulated conductor is electrified,
its pith-balls separate, because they are in a dif-
jftmtf electrical state to the air by which they 4re
surrounded^ whose niatter or electric fluid they
attract ; but all unelectrified^ bodies have - £he
same relation to the electrified balls ais the am-
bient air has, and such as are conductors and con-
nected with the ground present a more ample
source of matter and elective fluid ; consequent-
ly, if any such bodies are brought near the elec-
trified conductor, its attraction is exerted on
thenif and the influence of the surrounding aif
is proportionably diminished ; and if the proxi-
mity be sufficient, the attraction of the elec-
trified surface will be so exclusively exerted in
that direction as to be imperceptible in any
Other.
In this experiment the bodies are not brought

THE LBTDEN JAR, 97

in contact, but only near 6ach other, and con-
sequently there is no communication or Iqs^ of
electricity, but merely a compemation of itp. at-
tractive power; hence when the unin&utated
platcf is removed the divergence of the electro-
meter is restored.

This fact shewing the diminished intensity of

insulated electrified bodies when opposed to un-
insulated conductors, supplies a method of in-
creasing the positive or negative states (usually
obtained) to a very great extent ; for it is evi-
dent the electrical state of any body may be
altered in the greatest degree whilst it is opposed
to a conductor communicating with the ground,
since, in that situation, its electricity will be
compensated by the proximity of an exhaust-
less store, and cannot so soon acquire an inten-
sity which would oppose its further progress, as
the diminished or increased elasticity of the air
by rarefaction or condensation limits the opera-
tions of the air-pump and condenser.

Since electrical attraction diminishes as the
square of the increased distance at which it
operates, the action of this principle of compen-
sation will be greater in proportion as the dis^
tance of the opposed surfaces is less, provided

9i fUt tirdtir jau*

n itsiflltiag Medium be plAcid between them, to
ftevtut the tntMrnisisioii of the electric Aaid
fp6m ont tx> the dther. When air is the intei**
tMhig body» it will tesi^t only the paiisa^ of
Amall quantities of electricity, as the mobilitf
of its particles occasions it to yield to a very
riight force : glass and Muscovy talc are the
m6it cOtaipacit of the solid nonconductors tl&l
can be reduced to their lamina, and these there^
&i^ form vei^ fit media for the purpose of such
eij^erimehts.

Tte insulating faculty of nonconductors de^
•pth^ on their impermeability to the electric
finid; and,- in a perfect state, the most compact
of diern are never penetrated by it without me-
chanical injury: but electrical attraction is ex-
erted through thin sheets of glass or other non-
conducting matter with some facility : this has
been considered by some as anomalous; but it
h not more surprising than that the sun shoidd
act on bodies at many hundred millions of mll€»
distance without any apparent medium of con-
nexion: nor is it more remarkable that elec^
tricity and matter should act on each o their
through media that resist their transition, dmh
that a magnet axid a piece of iron should exot

iiifeir muttittt attiPttieticrti x^liett i^paMted %
bodies ihrbugh lirhich fldther the lA^et p«
iron cad passi

If a sheet o( ghm thm M^t^ciM b^tWMfc
two plated 6f n^etal^ otie of Trhich is ediittecitefl
with thie groufid and the other not \ th^ iilsti^
lated plate vill have a greater capacity fot elec-
trieal chafage than if f reefy insUlatdi, and May
be electrified either positively or negatively td
ft gteater extent The oppo&itioti of an insulated
to an uninsulated conductor is the conditiofa bf
tibe experiment I its success therefore does not
d«petid on the fofm of thfe glads, but its thitti^
iMSf which forms the med'naii^ ^HT il^tHration be*
tween the metal plates ; they may be laid oii th4
opposite surfaces of a glass plate^ a sphere of
tiw tatnc substance, or a jarj but, in either case^
the glusa must ea tend two ot three inches bt-^
yond the liiAit of tlu? metal coitii^gs^ that they
tiMiy;be teparattd by a sufficient interval of air.
Tfar middte only of a plate of glass shduld b#
coveted with metsAy leaving ati intei'val of two
mda^n sll jround. — See Figure IS. A plat^ M
pHi^ned is ealidd a^ coated pciT^v
r ^ : The bi4s# eoni^enient fotn^' i^ timof A ^flihi
^kaliJAFi €W€t^ ^ the |l»ide:aiid^f ^^0 #itU

H S

KK) THiE lETDEir jAb.

tinfoil to within two or three inches of the top
edge, the uncoated part must be kept clean and
dry; to the inside coating a wire and ball should
be attached, and rise two or three inches above
the top of the jar. — See Figure 14. This is nearly
the form in which the experiment was first made
Jn the university of Leyden, it is therefore called
a Leyden jar, or phial, and occasionally also an
electric jar.

The metallic covering on the inner surface
of the jar, with its attached ball and wire, is
called the inner coating; the metallic covering
on the outside of the jar, the outer coating ;
and the uncovered part of the rim, the uncoated
interval.

Expefiment 37. Present the knob of a Ley-
den jar to the conductorof an electrical machine
at the distance of about half an inch, the jar
being held in the hand by its outer coating;
a series of sparks will pass to the ball of the jar,
but will gradually grow weakei: and at last cease*
Remove the jar from the conductor and ^its
coating being still held by one hand) txmch the
ball of the jar with the other; a smcirt snap will
be: heard, and a violent and painful sensation
be experienced, principally at the wrists, elbows^

ajid.acioss the. breast This singular sensation,
whioh must be feltJto be conceived, is called ai^
electria shock : it is painful only for the mo-*
menty and. leaves no permanent impression but
that arising from surprise or fear.

Eaperiment 38, Make the uncoated interval
very clean and dry, and place the knob of the
jar in contact with the conductoj^, holding the
jar by its outer coating as before;- afte^* a few
turns of the machine flashes of light will be
seen on the uncoated interval, and these will be
soon followed by a loud explosion and a most
brilliant electric spark, passing £tom one coat^
ing to the other : if you now touch the knob^
but a very slight sensation will be felt, th? elec*
trical equilibrium being restored by the explo*
sion and spark, which having occurred by the
force of the accumulated electricity is called a
spontaneous explosion^ or discharge<i

The application of the jar tathe maehine,
to^prepare it for the production of these effects,
is called charging the jar; and any process* of
exiplosion by which the equilibrium is restored,
its discharge. To effect a discharge, a com**
munication must be mrade between the iiinet
4iid auter coatings by :s6me conductor, sa that

16A niE LSTDEK.IAR.

the . power of the jar arises from the difFerant
electrical states of these coatings ; and as theif
(;x)nimunication destroys all signs of electricity,
they spust be respectively positive aiid negl^ve
in an equal degree.

To avQid the shock during experimenta with
the jar, its discharge is usually effected by twQ
knobbed wires, connected by a joint like a jitaif
pf compasses, and mounted on a glass handle s
such aip apparatus iq called 9f discharging rod.-r^

Tq ascertain the degrees in which the jar is
f^harged, ^ particular eontriyaixce, called llent
liJy's elQCtrometet (from the name of its inventor)
19 employed : it consists of a smooth round stem
about seven inches long, with a ball on its top ;
immediately under this ball ^ sen^icirde of ivory
13 fastened tq the side of the stem ; in the cent
tre of the semicircle a pin is fixed, on which a
t^in pieee of cane, fouf inches long, with a light
hftU at its low^r end, turns freely, and traverses,
the semicircle as an index, Tl^e lower half of
1^ ivQry semicircle is divided at thi^ edge intQ
fiQ ilegr^e^. When this instrument is not elecr
trified, its isidex hangs parallel to the stem; but
lUffa^n el^rified^ the light ball reeedes^ and ca^rie^

Tim h^umv. uf^ 103

%}m ki4f^K Qv^r tlw gT^^wat^ oilrple to fc greater

the eleistriQ}^,— Se^ Figure lS^ The reccRsiioii
^ tb^ inikx; from the slew ia gTe»it9it wbeait
itiiQdipf 9t right aiigk$ to it, qi: poivitft horizovi'*
Wiy; ajid l^Yiog theft moved ov^rjft (ju^rter of
a circle, it is said to indicate an electricity of
80 degree; When the index ia parallel with
ijm ^?ait it stands at 0^ or the commencement
of the s0al« ; Bifid, 9A it gradually recedes, pas^
^ux)ugh 10, SO, 30, &c. to its horizontal positioii
of 90* HebCQ this instrument is also called ^
^adrant electrometer.

The power of the Leyden jar is not 'mor«»
than propprtioned to the time required to cl^arge
i%\ ipany bwBdred sparks will pass between th«»
i^t^uj^tor and its knoh during that, process, and
tbcfie are all ponoentiated into one spark when
tiie jar is discharged ; and hence th^ increased
IwilDess of the explosion, bdlliance of lights
and . acuteness of the sensation it produces.rT-«
. The. jar, when applied to the conductor of thf
Wacbioe, diminishes its intensity, and admits 4|
Viicb :greater change in its electric state before
tuy given resistance is overcome, or force q£
{ittractiQn manifi^s.ted ; this^ is seen by placing

104 THE LBTDEN JAB.

the quadrant electrometer on the conductor!
if the machine is turned, the electrometer im*
Biediately rises to its limit, but when the knob
of the jar is placed in contact with the conductor,
the machine m\ist be turned many times before
this is- effected, and the rise of the electrometer
l^then very gradual.

Experiment 39^ The power of the jar, as a
source of electric accumulation, depends on the
opposite states of its two surfaces, which cannot
obtaiu unless one of them is connected with the

ground. Suspend a globular jar* by its knob
from the positive conductor of the machine, it3
outer coating l)eing surrounded by dry air can-
not, part with ^ny of its natural electricity, and
consequently the action of . the most powerful
machine will not communicate any charge to
the jar (as will be seen by applying the dis-
charging rod to it), for the coatings are only to
be considered as conductors to the opposite sur«^
faces of tb^ jar ; and the glass has only an at*
traction for a certain quantity of electricity,
which, in its natural state, resides on each of its
surfaces, and tio addition can be made to the
quantity naturally existing at one surface^ but

* Figure ij.

THE LEYDEN JAB.

by a correspondent diminution of the quantity
naturally existing at the other. Hence, if a
finger or other conductor be brought in con-
tact with the outer coating of the insulated
jar, or if a point be presented to it, its natural
electricity will escape, and the jar will receive
a charge.

Experiment 40. Take ta-o Leyden jars of
similar size, insulate one of them by placing it
on a glass stand, and place the other on the
table, with its knob at half an inch distant
from the coating of the insulated jar, the knob
of which should be placed at tlie same distance
from the conductor of the machine; for every
ipark that passes from the co?idnc/or to the Knob
of thejirsljar, there will be a simila?' spark pass
from the coaling of the Jirst Jar to the kmb of
the second; and if they arc successively dis-
charged, the sound of the CNplosion and the
brilliance of the light will indicate that they
have each been charged to the same degree.
Now, as the second jar was charged by sparks
from the coating of the^W^, and as their charges
were equal, it follows, that for every particle
of electricity added to oiie side of coated glass, a
corresponding particle leaves the opposite surface.

)0$ THB IfETDBV JAR.

On thi^ principle a jar inay be charged by
|he transfer of its own tiatural electricity froin
one surface to the o^her, by insulating it and
connecting its knob with the positive condu^tof
and its outer coating with the rubber of the
niachine: electricity will be taken froni ths
outer surface by the negative rubber, and qon^
veyed to the inner isuri^ce by the positive pon-*
ductor ; so that the jar, though perfectly insu.^
lated, is charged by the unequal distribution of
its natural electriq fluid. This experiment i9 4
satisfactory proof of the impermeability of glass
l;o the electric fluid, for the conductor and the
rubber of the machine are separated from con^
ducting contact with each other only by the
thickness. of the glass jar, and a powerful accut
mulation of electricity takes place, which the
contact of the thinnest film pf conducting mat-
ter or the slightest fissure in the gla^ji would
have prevented.

When glass is charged, the attraction of itf^
in^tter at the negative surface is nece^sv'ily ex^
^nrted pn the electric fluid accumulated at the
pojsitive surface, which ii^ kept at a distance
^rQQi it by tb$ intervening thickness of glasa ;
)f tlie opposite snrf^^es are connected by a (:pn?

VHB LETDSK JAB. 107

ilSuotor, this dis^noe is annihilated/ th^ fiuper-^
fluous electricity nish^s to the attradting sur^
^ee and restores the equilibrium; suqh is the
^tion of the discharging rod. But if no such
eonnectiiig medium be applied, if the glass be
thin, ajtd its coatings separated by a sufficient
extent t)f uiicoated interval} the accumulation
may be carded tq such an extent as to break
through the. plate of glass to the attracting sur->
^e, producing amechanical Aractufe, which,
by rendering the glass permeable to electricity,
presents it from agaia receiving an dectric
pharge. Th^ thinnest glass, if sufficiently resist*
ing^ would produce the greatest accumulation,
twt a certain thickness is required to prevent
Idle, ehance of; fracture : Muscovy talc, in very
thill, lamipa, is still highly resjisting and •su3cep*
tible of a considerable charge.

The dificrent effects of the interposed sub-
stance QQ the quantity of electricity required
to.prbducea given intensity, may he illustrated
byjomting ^qual surfaces. of thick glass, thin
glaisB^ and a lamen of talc : if these be success
lovely .charged at a conductor with an elect9o«^
p^eter attached, it will be found that the index
(^ the electrometer will rise to apy given degree

lOS THB.LEYDZN JABk

with much fewer turns when glass is.charged
than with talc ; and that the number of turns
will be least of all with the thickest glass. — ,
Hence it is evident that the common electro-
meters do not indicate tlie actual quantity of
electricity^ but merely its intensity, or tendency
to an equilibrium by motion or explosion.

As the accumulation at the positive surface
of charged glass depends on the attraction of
the. matter at the opposite surface, it followi^
^hat no discharge can take place unless thesei
surfaces are brought in conducting communi-;
cation ; hence either side of a charged jar may
be handled with impunity if it be first placed
on an insulating stand ; nor will the knobs of
two differently electrified jars explode whep
brought together, unless their outer coatings
are at the same time connected with each
other.

Experiment 41. Take two equal jars, with
a quadrant electrometer attached to the knob
pf each; place one of them in contact with the
positive conductor of the machine and the other
with the negative conductor;* when the ma^

' • It »s to be recollected, that when one conductor of the
macfaioe only isused;^ a chain or wire is to be suspended frooa

THE IfiTDEN JAR, 109

tihine is tiiraed both jars will charge, and to the
same height, as may be seen by the receding in-
dex of each electrometer: remove the jars from
the machine and place them on two separate
insulating stands ; connect their knobs by aft
insulated discharging rod; no explosion will
'ensile, although they are oppositely electrified;
for their electricities depend on the attraction
T)f their outer surfaces, which, in this insulated
state, have no means of communication. Con-
Tiect the outer surfaces bv awire or other con-
ductor, and repeat the experiment; an explo-
sion will take place, and both jars will be dis-
charged.

' Eaj}eriment 42. Place a jar, with an clec-
^ometer on its knob, in contact with the posi-«
dve conductor, turn the machine until the index
rises to 60; remove the jar and place it in con-
tact with the negative conductor; on tutting
the machine the index will fall, and after ji few
turns the jar will be unelectrified, but if the^
turning be continued the electrometer will rise
again with a negative charge; when^ by remov-

(he other to the ground; but when loth are used togeUier^ 4^
diim (Sr wirfc U'to be eotirdx iiemoved

110 t)tLZ Lzrwv tAti

Ug it to the posiitiVfe conduCto/^ it may be agtdll
^fteleitrified.

Tbfi charge of any jar may be dividbd mC#
«qtual and definite paf ts : by cdnnecttn^ its inner
laad ^utir cdating with the inndr and outienr coat^
iAgs of an mnelectrififcd jar of the satnd ntztuni
•thicknesfil : the charge will be equally i^videdi
between them ; ahd by repeating this prbces^
.the quatteri eighth, sixteenth^ or any aliqiiof
^art of the original charge may be obtaiiied«

Experiment 49* Hold a clean and Atj pane
^f glassi by one comer, and paas it before at ball
^onnetted with the positive donductor of the
machine, so that the ball may successively confit
at contact with every part of the middle 6f the
{>ane t>f ^ss, .whilst the finger or any mrin^
iiftlated substance is opposed to it on tl» oppo^
aite. surface : h^ this process the glasis^ viU be
charged.. Apply the discharging rod to the
of^osrte iuilfaoes, ali explosion will ensue; make
the itbntadt ^ith the dischar^g rod ^ain wi,
aiiotiier part of the sorfatie, another expiaiioai
will' be jtfrgctttfid; and in this way tnaay are
sometimes obtained in succession. Repeat the
experiment of charging, and then plao* the

tHK UTBiSr JAS; 111

ttifttgtdi pkd»e between tW9 phies of metal of
(ilK)uf ' hiilf iu mcf on the afiplfclEitum of the
^^^huf^g md but cme ex]>fa)sion will be {)r»
cured, but it will be louder and niore brtUiatit
thmi tlioiie procured fr^xti tbi uticoated pane»
Hetiee it it seen that the use of the nsetallic
ooisUHhig is tD cM^9i^r the ejfedts of ^ery portkm
^f ^(6 sn^rface of the jar, so that it Bia^ be
ifUi^f^td or Sscharged by the iiiiipie aipphcsttioft
of the niacfhkie or dischlitging tcdtOMtportum
of irts «uirft(Q3.

EMpetimmt 44. Pla<se an uncoated jar h^
aeath the conductor of the machine) atidims^
pend l^'Ohain from theconductoir so te to hang
4n the centre of the jar ; on turning the m^hane
the^hs»n wilt move round, and apply itself im
siHknession to every part of the internal surfiiim
of the jar, wbieh by thit means recetyea a
<$hiirge. 'Apply the discharging rod, and ibe
chain wiU return over the parts with wiiieh it
tee' Jbeen in contact, and thus by a few ef its
ttsvoiations «be )ar will be discharged^

Eifperifnem 46. Take a Leyden Jar, Ooated
<bn l&e inside as nsual^ but wi^ a eotting of etnlgr
ot^e inch highpn the outside; during die ch*i|{e
%ttd discharge of this jar^ ranrifieti(kiaiis of «Un>

112 .THE JLEYDEK JAft.

trie light will be seen on the outside, which ate
occasioned by the natural electric fluid of the
outer surface passing from one part to another
during its departure and return.

Experiment A6. Procure a jar with a double
set of moveable tin coatings, either of which
may be adapted to it at pleasure; the outer
^coating being a tin can large enough to admit
the jar easily within it; and the inner coating
a similar can sufficiently small to pass readily
in the inside of the jar. The charging wire of
the inner coating should be surrounded by a
glass tube covered with sealing-wax, to serve as
an insulating handle, by which the inner coat-
ing may be lifted from the jar when that is
charged without communicating a shock to the
roperator. Arrange the jar with its coatings and
^charge it ; it will act in every respect as an or-
-dlnary coated jar. Charge the jar, and without
discharging it, remove the inner coating by its
iitsulating handle ; if this coating, when removed,
be examined, it will be found not at all, or but
iiUghtly electrified : lift the jar carefully from
^within its outer coating, and examine that ; it
cwill evince no signs of electricity. Fit the jar
-up;vith the othier pair of moveable coatings that

Imvie not been eliectrified, and 'apply Iht idia*
charging rod ; ah explosion and spaHc will en«-
siie ; proving that the accumulation is retaibed
by the attractive power of the giassy And that
the mr^mg-jf are consequently only useful as
conAc^ori to the charge.

The comparatively lofw intensity of any giveti
quantity of electricity accumulated in the Ley^
den jar, when compared with a similar quantity
d&posed on an insulated conductor^ occasions
the jw to retain its electric state for a very long
ttiae under favourable circumstances: this fact
was 'Observed soon after the discovery of the "^
instrumehi; ; and it has been since found, that
if the surfaces are well separated from eadi
otfaery the charge may be retained for many days
or even weeks.' The charge is usually dissipated
by the motion of piarticles of dust, or other con-
ducting substances in the atmosphere, from me
of the coatings to the other^ or by the uncoa^d
interval becoming moijity and losing its insulata^
power ; consequently a jsur will retain its charge
Vmgcr in dry than in damp weather: but; the
ittfluente of external causes may be partly pre-"
vented, by a particular coni^ruction. Coat the
inside and outside of a narrow QeckeB phial;

9 14 «HK nrssir jab>.

ud oraient into it a glass tube hmg etnmgb to
icadi to the bottom of die phial and extend an
inch iAove its heck ; the inside of this tube
tfaould be trovened with tinfoil to rather more
diaii half its length from the. bottom, and its
lining should be connected, with the inner, coat*
ing of the jar. A wire with blunt ends and half
•the length of the tube is to be placed loosely
"Within ity and the top of the tube closed with
a. smooth brass cap. By this arrangement the
contact of the atmosphere with any part of the
interior coating is entirely prevented, and the
conducting communi(»tioa for the charge is
procured by inverting the phial, which occa^
sions the loose wire to fonn a temporary con-
nection between the inner coating and the brass
cap of the tube. When the charge has been
eommuhicated, the phial is to be set upright;
the loose wire falls within the coated part of the
tube and cuts off all conducting communication
ynBi the brass cap and the atmosphere. The
phi^l will then retain its charge, and may be set
by^ or carried in the pocket until wanted ; .when
being inverted, and a communication establish-
ed between its outer coating and the brass c^,
the discharge will be effected)

THE JLETD2N JAK ' : :: IM

: fnio ftinipie operation of covering, tb^i^^r
coated part of the phial mtix melted deajijogt
wax, or with varaisb, prevents the depositkoi
of moUtupe upon it, aud consequently tenjda
also materially to. prevent the dissipation of tho
charge.*

- The properties of the Leyden jar, which liave
been developed by the preceding experiments^
may be further illustrated by the very numerous
varieties of them describe in many experim^en-
tal essays on the subject. The extent, to which
the modi^cation of these experiments has been
joarded, may have arisen,, in some in&tances,
from an attempt to establish particular opinions,
pr to oppose others ; and has been rendered
necessary by the apparent anomalies which at
^vst seemed to oppose any reference of the
-several phenomena of electricity to simple ge--
n^ral principles* The supposed existence of a

* The sur&ce of .glass may be coated with lealing-wtx^ by

• *

varmiDg it gradually before a fire until it is hot enough to fuie
the wax, a stick 6f which is then to be quickly rubbed over its
surface, . If varnish is used, it may. be applied with a flatcam^**
hair pencil^ the glass being previposly warmed. It is alp^qst
unnecessary so say, that any varnish that may be used lor this or
other electrical purposes^ should be perfectly tec ton dam*
miness. ....

116 ELECTRICAL INFLUENCE.

repulsive pbwer^ as a property of the dectric
Bmd, has also tended materially to confuse our
id»s on the subject ; as, in order to explain the
separation of negatively electrified bodies, it was
necessary also to imagine that the particles of
common matter were equally repulsive of each
other; a supposition which is contrary to; ex-
perience. Hence the fine superstructures of
Mr. Cavendish,* and of -Slpinus,f are consider-
ably reduced in value by the hypothetical basis
on which they are founded.

The mutual attraction of the electric fluid
and common matter ; the elasticity of the former,
and its tendency to the surface of the bodies
with which it combines ; the different conducting
faculty of various substances ; and the alteration
of their natural attractive powers by contact,
friction, expansion, or other change in their na-
tural arrangements ; are little more than simple
expressions of the facts we observe : yet these
simple principles have supplied an adequate so-
lution of the phenomena we have yet consider-
ed, and are equally applicable to other apparent
varieties of electrical action.

• Phil. Tians. vol. Ixi. p. 584.

f TenUmeo Theori® ElectricitatU et Magoetisniu

ELECTHICAL INFLUENCE; 117

In the Leyden jar it has been observed/ that
the addition of electricity to one surface is con-
stantly attended by the loss of electricity from
the opposite surface;* and this transfer, it has
been shewn, is essential to the charge, which
cannot take place without it. There are a va*
riety of analogous phenomena, some of which
it will be proper to consider in this place.

And first, with respect to the jar itself; it
must follow, from the preceding principle, that
during the process of charging, both surfaces
of the jar evince the same electrical state : for,
suppose the inner surface to be positive, it will

have a tendency to give electricity to unelec-
trified bodies ; and this is precisely what the

* That 18, when, by the jar being uninsulated, a sufficiently
extensive reservoir is provided for the reception of the displaced
electric fluid-, for, if the jar be insulated, a very small quantity
only of electricity can be added to either surface, and that addi-
don, by its action on the attractive power of the glass, occasioqs
.a similar portion to be released from its natural state of combi-
nation on the opposite surface: so that both sides of the glass
evince signs of positive electricity^ Such, therefore, is a case of
communicated electricity ; and^ it should be recollected, that such
cases are distinctly separated from the charge, and all sEinaiogout
phenomena, in which the natural quantity of electric fluid it
neither increased nor diminished^ bat is merely unequally dis*
-Mtrntcd.

i 1 S ELECTAICAL TV? LUENCEi

outside mu^t do before it can become negafive :
bnt the inner surface appears positive, because
the positive <ionductor is dddittg electricity to it
faster than it can appropriate the attraction of
tjle opposite i^urface to iti$ increased quantity;
khd the biiter surface appears so because its di^
ininished attraction causes its natural electricity
to leave it. Consequently, as soon as the turn-
ing of the machinie is discontinued, the outer
surface having losi a portion of its natural elec-
tricity, must be negative ; knd the inner surface,
which lias increased its Original quantity, must
De positive; although they appeared similarly
electrified during the process. And the converse
of this 'must be the case when the jar is charged
negatively.

A plate of air, or any other nonconductor,
may be charged in the same manner as a plate
of glass; but as air is more readily displaced by
electricity, in consequence of the mobility of its
particles, a thicker stratum of it must be em-
ployed. Th^ usual form of the experiment is to
employ two circular disks of wood covered with
tinfoil, and well rounded at thcf edges, having
a dii^uncter of frpm two to four feet One of the
boards is to be placed flat upon a table, and tb^

other |)eiQg suspended by a silk cord fron^ thf)
ceilmgy 16* adjusted so as to hang parallel oy^c
its surface; and at the distance of an inch or an
inch and a half from it The upper inaukted
board being connected with an electrical md-,
chine^ the stratum of air between the boards
becomes charged, and will cominunicate a shock
if the upper and lower one be touched at th^
same titne with opposite hands. The shock pr6«(
duced in this way is considerably less vioknl
than that from an equal surface of coated
glass;. for the distance of the coatings is of
necessity much greater, and the medium bet
tween them less perfectly insulating : and this
last circumstance operates so rapidly when th^
charge is high, that its maximum of effect can-:
not be obtained but by making the discharge
ij$fhilst the machine is still in action. If the
discharge be not made, spontaneous explo*
sions from one disk to the other, through th0
intervening plate of air, Will occur at inter-
vals, as long as the electrization of the Upper
disk is continued.

Analogous to the process of the last experi*^
mept Ja the production of the electric spark
und^r grdinary circumstances : when: any con-?

liO BLBorai €At iirpiiTiiires:

ducting sHbstaxioe, inJtsnatMal state, -is pre*
sented >=to a positive conductor, it». matter is at«
tracted by the proximate electricity of the
positive body, and the electric fluid before djf'
fusid oyer its surface retires to the most remote
parts : if the presented substance be insulated^
it will therefore become negative at the suiface
near the positive conductor, and positive at the
surfisu^e which is most remote ;^ and if it be suf-*
ficiently light or pendulous, it will move toward
the positive conductor until a spark occurs be*
tween them. If, instead of an insulated body,
any conducting substance in cojinectien with the
ground be presented to the positive conductor,
its presented surface will become more highly
negative, since its natural electricity has fiit-
Umitted room to recede : hence ufdnsuinted bodies
are attracted at greater distances, and receive
stronger sparks than the largest of such as are
insulated.

It is thus seen, that whenever sparks or at-
tractions are produced, the bodies between which
they pass are necessarily in opposite states of
electricity, and are therefore analogous to the
coatings of a Leyden jar, and serve indeed as
coatings to the plate of air by which they are

THE ELECTllOPHORUS.

131

separated : the force of the spark will therefore
be influenced by the extent of the insulated
conductor, and the perfect connection with the
ground of that which is opposed to it. When a
very large conductor is attached to an electri-
cal machine, the spark from it may be made
equivalent to a shock, by any individual stand-
ing on a wire connected with a well or water
pipe, and receiving tlie sparks from the con-
ductor on a large brass ball held in the hand.

From this tendency of electrified bodies to
produce an unequal distribution of the natural
electricity of all such substances as are brought
sufficiently near them, some curious phenomena
result; and the action of some of the most in-
teresting instruments are dependent entirely
on their opei-ation. Of this kind are the Elec-
trophorus, and the Condenser; two very re-
markable sources of electrical accumulation,
invented by professor Volta.

The electrophorus consists of two circular
plates of metal, or of wood covered with tinfoil
and well rounded at the edge; these are called
the conductors : between them is placed a resi-
nous plate, formed by melting together equal
parts of shelUac, resin, and venice turpentine,

ISi THE fi£BCTROFHOBUfl^.

and pouring this mixture, whilst fluid, within. m
tin hoop of the required size, placed on a maxhlc
table, from which the plate may be readily separ
rated when cold. This resinous plate should
be about half an inch thick : it is sometimes
made by pouring the fluid mixture on one of the
conductors, which is then formed with a rim
for that purpose. The conductor on which the
resinous plate is placed is called the lower con-
ductor, or sole; and that which is placed upon
the resinous plate the upper conductor, pr cover :
this last is always furnished with a. glass, or
<>ther insulating handle ; and when the electric
fttate of the lower conductor is to be examined^
the whole apparatus is placed on an insulating
stand. — See Figure 18.

Ejeperiment A7 • Rub the upper surface of
the resinous plate with a piece of dry fur (cat's
skin is the best) ; it will be excited negatively-.
Place the upper conductor upon it, and then
raise this last by its insulating handle; it will
l)e* found to exhibit very faint, if any, elec-
trical signs. Replace the conductor, s^nd^ whilst
it liies on the surface of the excited plate, touch
it with a finger or other uninsulated conductoi;,
mAikim raiise it again by its insulating handle*^

THE ILECTHOPHORCS. ISI^

it will now appear positively electrified and
a£Fbrd a spark : if it be then replaced on the
resinous plate, touched and again raised, another
spark will be procured ; and this process may be
repeated for a considerable time without any
perceptible diminution of effect.

The uniform result of this alternate contact
and separation of the conductor, without any
new excitation of the resinous plate, evinces
that the actual electric state of the latter is not
destroyed by that process; and the necessity
for the connection of the conductor with thfc
ground before it is raised, proves that the ac-
quired electricity is derived from that contact'

The nonconducting faculty of the resinotiis
surface, and the imperfect contact the fiat con-
ductor forms with it, precludes the transmission
of electricity of low intensity from one to the
other ; when in contact, they are therefore only
to be considered as very near each other : now
it has been seen, that when an insulated ccnducMr
isi brought near an electrified body, the natural
distribution of its electric fluid is disturbed, aid

■

the conductor becomes oppositely electrified it
4he anterior surface, and Similarly electrified Ajt
ibt posterior or remote surface; consequently

l!24 TRB ELECTRO PHORtTB.

the caoer of the electrophorus, when laid upon
the resinous plate, which is ii^^aifn)e, will have
its natural electric fluid determined toward that
plate, and it must then appear also negatvoCj
and will. receive electric fluid from any conductor
brought near it : this increased capacity, arising
. onjiy from its extreme /rronmiVjr to the resinous
plate, ceases when the cover is raised by its in>-
sulating handle ; and the additional electricity
it has received is then given oflF in the form of
a spark to the first conducting substance it ap-
proaches*

This explanation is by no means what would
be inferred from a superficial view of the phe-
. nomena, for the spark that passes to the cover
. whilst it is on the resinous plate is less consider-
able . in its appearance than that which passes
Jrom the cover when it is raised, although it is
here stated that they consist of the same quan-
tity of electricity : it is therefore necessary to
.shew that such is really the case.
I Experiment 48. Place the cover on the ex-
nted plate by means of its insulating handle,
aid bring the knob of an unelectrified Leydep
jir in contact with it, then touch the cap of an
\4ectrometer with the knob . of the j^j, and it

TH£ ELECXaOPHO&US. 1S5

will diverge with; negative electricity. Raised
the cover, and present the knob of the jar to it,
a. strong spark will pads ; bring the knob of the.
jar^ in contact with the negatively electrified
electrometer, its divergence will be exactly, de-
stroyed : now this effect could only be produced
by an equal quantity of positive electricity ; for
had it been morey the electrometer would have-
separated again with the excess, and have re-,
maihed slightly positive; and had it been kss^
the original divergence could not.liave been
vr^o/^ destroyed, and the electrometer must iu .
cofijiequence have remained slightly negative.
When the lower conductor of the electrophpru^
is also insulated, it evinces electrical signs : if
the excited plate only be placed on it, it is ne-
gative; but when the cover is placed on the
plate, its state changes to positive; and whea
the .cover is raised again, returns to negative ;
SO; that the opposite coatings of the plate, are
always in opposite states of electricity, whicl)
ought: be expected, since, their arrangement
is. similar to that of the coatings of a Ley den
phial, . from which instrument the elegtro^
liho.rus. differs only by combining the power of
fiA: eleQtrical mfichine^with the properties of the

iSfi THE CONDEKSEIt,

jar; the excited surface of the resinous pUte
being a permanent source of variable attractioa
in its contiguous conductors, and the approxi-
mation or removal of one of these modifying
the influential power of the excited surface on-
the opposite one.

The power of a well- constructed electr^i
phorus is sufficient to adapt it as an occasional
substitute for the electrical machine ; sinot
about 20 sparks from the raised cover of tW
instrument, given in succession to the knob of
a moderate sized Leyden phial, communicata
rather a strong charge to it ; and the permaneni
action of the excited plate admits the frequeirf
rej>etition of similar experiments. i

The Condenser, is an instrument in whictt
Professor Volta has applied the principle of apf
proxiniated surfaces, to the detection of suc^
shght electrical changes as are not appreciablt
by the most delicate electrometers- The pro*
ceding details have shewn, that any insulated
conductor, opposed to one that Is not insulated,
has its capacity of electrical change increased
by that proximity, and is more susceptible of
an increased or diminished quantity of electrif
fluid than when freelv insulated ; because in th«

THE CdN1>EK»n. tft7

State of a}^roxifflatioii a much more cMirider*
able change will be required to {mxlHce tbe
same kaeimty^ or teiidency to equililbiiliai. —
Now, wa3 the contiguity of the opposed platM
permsBent, no advantage wduM be obtained \
for the principle which renders^ the insukted
plate susceptible of more estteiMive -electrical
chaise, =also prevents it frotn rendering thtft
change evident : it is therefore essential thttt
the plates should be so arranged as to admit of
alteroate proximity and separation.

The most simple condenser may be fomed
by placing three small spots of sealing-waX| at
^ual distances, on the lower face of the <Govef
ef an electrophorus, to serve as short insutetiiil^
kgs by which it may be supported at the iJis->
tance of about a twelfth of an inch from this
surface of a smooth and even table. If a Ley*
ded jar be now charged, and afterwards c^
dialled, so as not to affect an electrometei^ loMl
ita knob be then placed in contact witib thi^
condenser resting upon the table for a ftv
seconxisy the very small residuum of electricity
iemaining/ in the jar will be absorbed by the
jdbondenaing plate ; and when this is raised fitos
Ab. table it wiU affect the electrometer wUh

IS9 VHB C0HDEV8BR.

the same electricity as that with which the jar
was charged.

The most improved condensers have the in-
sulated plate fixed on a glass pillar, and the
uninsulated plate supported by a brass wire
with a joint and stop : the plates are parallel to
each otheri and when electricity is to be com-
municated to them they are situated at the dis^
taiice of the thickness of a card from leach other;
the uninsulatied plate is then drawn back, and
the intensity of the insulated plate displayed.-—
See Figure 19*

The power of the condenser, thus construct-
ed, is not jal way s sufficient to manifest . very
sUght effects : Mr. Cavallo extended its appli*
cation, by transferring the electricity of the first
condenser to the insulated plate of another of
smaller .size ; this small plate is now usually at-
tached to the cap of a gold leaf electrometer,
and a similar plate is opposed to it by a jointed
wire connected with the foot of the instrument
See Figure 20.

' ; The use of these combined condensers af-
foxds a means of detecting very slight electrical
changes; and so obvious is the importance of
thit; p|X2perty, that many eminent electricians

£L£CTRICAL IKFLUEKCEi 189

liave bestowed considerable labour in attempts
to produce more perfect and delicate arrange*
ments for its application to purposes of researcb.
Of this kind are the doublers of electricity, in-
vented by Mr. Bennet and Mr. Nicholson f. the
multiplier of electricity, contrived by Mr. Ca*
vallo;-f: the electrical spinning instrument of
Mr. Nicholson ; ^ ^nd a double multiplier of
Mr. Wilson's ; § contrivances of considerable
ingenuity, l^ which the powers of the simple
condensers are far exceeded : but, unfortunate-
l}% the increased sensibility of these instruments
is attended by a tendency to produce the elec-
trical states spontaneously^ and the equivocal
results they consequently afford, is a very con-
siderable abridgment of their utility.

The various phenomena that have been now
considered, include the most important diver-
sities of electrical action; they cannot be con*
templated without perceiving a distinction be-
tween t\\e<:auses^ of the electrical appearance of
different insulated conductors ; for they display

* Phil. Trans, vol. Ixxvii. p. 288. and vol. Ixxviii. p. 1. 403.
t Cavallo^s Complete Treatise on Electricity, vol. iii. p. 99.

' . t Nicholson's Journal, 4to. vol. i. p. \6. .
i Nicholson's Journal^ 8vo. vol. in. p. 19.

190 nSCTRICAL INFLUENCE.

two Separate methods of exciting those appear^
snces. First, by an actual alieratian of the na*
turiU quantity of the electric fluid the conductors
contain ; and, secondly, by its unequal distri-
bution in ^[ntn pronmate and remote parts. The
first method can only be employed by conveying
electricity to or from the conductor; it is con-
sequently called communicated electricity, or the
electricity of contact, and remains permanent
so long as the insulation is maintained. The
second method obtains whenever an insulated
conductor is brought near an electrified body ;
the presented surface obtaining a contrary elec-
trical state> and the remote extremity being nmi*
larly electrified, whilst a neutral unelectrified
point exists between them : but these electrical
states being the mere effect of a disturbed elec-
trical arrangement^ are only permanent whilst the
proximity of the electrified body to the insulated
conductor is continued^ provided its insulation
ha£^ been perfect Such phenomena are classed
under the general term electrical influence; and
the positive and negative states so produced are
called, the electricities of position, or approxi-
mation, and by some wxiters induced electricity.

131

PART ir.

07 THE if ECHANICAI. AND CHEMICAI, AOSNCISS:

OS BLECTRICITY.

CHAP. I.

Instruments required for the ^application of the
Electric Power to the Purpose of Experiment.

The apparatus, hitherto described, is adequate
to the production and accumulation of electrical
effects ; but when the influence of the electric
fluid on the bodies through which it is made to
pass is to be investigated, some contrivances
are required for its accurate and convenient ap-
plication to that purpose.

The form in which accumulated electricity
is most usually employed, is that of a- charge;
bence a variety of Leyden jars are required ;
fcr, although the same intensity of charge may
ht obtained with every jar o£ equal thicknessi,
the quantity of electricity wtU be in proportion

K 2

132

THE ELECTRICAL BATTEItT.

to the ejrtent of surface ; and the quantity is i
consideration of importance when good coa
ductors are employed to transmit It.

Very largejars cannot be obtained; the largest
I have j'et seen is one lu my possession, which
is eighteen inches diameter and two feet high:
the coating on the outside of this jar exposes ij
surface of about six square feet, which is by ii*H
means sufficient for all purposes : when great
electric power is required, it is therefore usual
to combine several jars together, so that they
may be cliarged or discharged at once as a single
jar. Such a combination is called an Electrical
Battery; and it is obvious that, by increasing
the number of jars, any required extent of coate^ .
surface may be obtained. ^^

The structure of an electrical battery shouW*
be simple, for its parts are occasioually deranged
during its use ; one or two jars sometimes break
by a spontaneous explosion, and until they are
removed and replaced by others, the battery
will be useless. The jars are usually placed in
a box with thin partitions, to prevent tlieir mu-
tual contact. The bottom of the box ir
covered with a trellis of wire, or with tinft^
o)i which the coated bottoms of the jars restjjl

7h4 KiECTkieAt *A**BfRf. tii

and their outer coatings are consequently in con-
ducting communication with each other. If
fherc are? twelve jars, they may be placed in
thre^ rows of fouf ieach ; every jar hating its
charging wire terminated by a smooth ring in*
stead of a ball A brass rod, with balls at iU
extremities, being passed through the rings in
each row will connect the inner coatings of four
jar^; and the rods of the three rows may be con*
needed together by laying two shorter rods ixora
one to the other : as the short rods are move-'
able, either four jars, eight jars, or the whole
battery may be employed at pleasure.*
. A battery is charged and discharged in the
same manner as a single jar, namely, by bring*
ing the charging wires of its inner coating in
contact with the positive conductor of the ma-
chine whilst the outer coating is in conducting
communication with the table, and, after the
charge has been communicated, connecting the
outer and inner coatings by the discharging
rod or any other conductor. The communis'
cation from the machine to; the battery may be
made by jointed brass rods, or by a thick cop^
jper wire, care being taken that no points or

* Figure 21.

151 THE EtiSOTRlCAL BATTESTi

edges are exposedi which would tend to dissi*
pate or weaken the charge.

When the uncoated interval of a LeydeD
juf 18 very clean and dry, no very conaiderable
charge can be given to it before an explosion
takes place from coating to coating over tl»
dry glass ; and, as the charge is lost by this oc«
ourrence, it becomes a source of inconvenience,
and severely so when large batteries, which it
requires a long time to charge, are employed.
This tendency to spontaneous explosion may
be much diminished by covering part of
the uncoated interval with any imperfect con<«
ductor; such effects have been produced by
slightly soiling the glass with handling it when
the hand is in a state of perspiration, by breath*
ing slightly on one of its surfaces, by placing a
wet sponge within the jar, or by slightly oiling
its surface : but these methods are not perma-
nent in their effect, and have been consequently
superseded by a simple arrangement more re-
cently proposed; which consists in pasting a
slip of writing-paper, of an inch broad, on the
inner surface of the jar, so as to cover the un-
coated interval to the height of half an inch

MANAGEMENT OF THB BATTJERT. 135

above the uj>per edge of the inner coating. The
action of this, and of the other n^eans that have
been employed for the same purpose, appears
to consist in a gradual diminution of the in^
tbnsity of the charge at that part from whicK
it has the greatest tendency to explode, by an
extension of the charged surface through the
medium of an imperfect conductor.

The height of the uncoated rim of the jat
should be proportioned to the charge it is in-^
tended to resist; with small jars, S inches, or S|>
inches is sufficient, the coatings being then
separated by an interval of 5 inches : with larger
jars a rim of 3 inches will be usually adequate,
if they are fitted up with an interior paper
band.

The uncoated part of the jars in a battery
tte sometimes varnished, which prevents the
deposition of moisture, and is of advantage if
the varnish be good : when varnish is employed,
the paper band is indispensable, for the ten-
dency to spontaneous explosion is much in-
creased by the uniform dry surface the varnish
presents. If the jars are not varnished, the
exterior of the uncoated rim must be kept dry
and free from dust.

186 VARIOUS £L£CTROIf£T£B8«

. . The jars in a battery should not be very thiii^
for the chance of fracture is greater when a bat**
tery is employed than with a single jar, inpro^
portion to the number it may contain. If the
jars, are but^ moderately thick, it will be of ad^r
vantage to interpose a thickness of writing-paper
biQtween the poating and the glass, which may
be easily effected by pasting the tinfoil first oi^
paper aqd afterwards applying this combined
coating to the glass. The metallic coatings
^re thus placed at a greater distance from each
pther, and the chance of fracture is diminished.

Next to the sources of electrical accumun
lation, it becomes necessary to consider the
aieans of estimating and directing the power
we employ ; since the same jar or battery is
iiusceptible of various degrees of charge. The
application of the quadrant electrometer to this,
jidmeasurement has already been described ; it
i$. placed on the conductor, and consequently
in contact with the internal coating of the jar
or battery, and indicates, by the rise of its index,
^e intensity of the charge conveyed.

Lane's discharging electrometer is some-
what ditferent in principle: it consists of two
balls of equal size, one connected with the inside

VARIOUS £LECT]tOMXT£fiS. \it

€>f the jar, the other insulated opposite to th*
ifirM, but capable of being placed either in con*
tact with or at any distance from it. The insu*
lated ball is connected with the outer coating
by a wire : it is therefore a vehicle for the dis-^
charge, which will take place sooner or later in
proportion to the distance at which the balls
are placed. The principal imperfection of thia
electrometer arises from the occasional inlru-^
sion of particles of dust or other light conduct*
ihg matter between the balls, by which the in^
dications of the instrument are rendered falla-
cious.— Fig. 28 represents a jar fitted up with
I.Ane'8 electrometer.

The most useful electrometer for jars and
batteries is that constructed by Mr. Cuthbert-
son : it consists of a metal rod, about 13 inches
long^ terminated by balls, and balanced on a
knife-edged centre in the manner of a scale-
beam^. One arm of the balanced rod is gradu^
ated, and has a slider upon it, which, when
placed at different distances from its fulcrum,
loads the arm with a proportionate weight from
one grain to 60. The graduated extremity of
the balance, rests upon- a similar' brass ball^
which is supported by a bent metal tube from

199 TAWOUS £LICTftOM£T£R9.

the same insulating stand ; and at four iiiclfies
below the opposite extremity another insulated
ball is placed, which is to be connected with
the outside of a jar or battery. Now, if the
metallic support of the balance be connected
with the conductor, or the inner coating of the
jar, and this last be electrified, there will be an
attraction between the extremity of the balance
and the lower insulated ball, because they are
connected respectively with the opposite sur-
faces of the jar ; and when the force of this atr
traction exceeds the weight with which the
opposite arm is loaded, the attracted arm of the
balance will descend, and discharge its electri*
city on the lower insulated ball. The power
of the attraction is always proportioned to the
intensity of the charge ; and as, in this instru-
ment, the attraction has to overcome a resiat-
ance proportioned to the weight with which the
balance is loaded, that weight becomes a pro-
per comparative measure of the intensity of any
required charge. — Fig. 23 represents this instru-
ment surmounted by the quadrant electrometer,
which is useful to indicate the progress of the
fdiarge, as that is not shewn by the action of the
halance electrometer itself.

KATURE 0? 4 ClftCtJIIR. (159

AH these inatrumentfl indicate Ou(y the in*
tensity of the accumulated electricity, or its
deviation frbm ii stat^ of natural distribution :
the quantity can only be inferred from the com*
paia.tiv6 estent of the charged surface/ or esti*
mated by an examination of its effect^ and is
therefore by no meanly accurately appreciable. *

The discharge of a charg^ jar is (as it has
been alrefidy stated) effected by connecting -thi
inner and outer coatings with some conductor :
this process is called forming a Circuit ; arid
any substance interposed between two parts of
the connecting conductor, or between it and
one of the coatings of the charged surface, is
said to be introduced into, or placed in^ the cir"
cuit. The most simple way of effecting this is
to place .the body, through which the charge is
intended to pass, in contact with the outer
coating, and putting one knob of the discharge
ing rod upon it, bring the other quickly toward
the charging wire of the jar ; the electric fluid
is thus constrained to pass through the inter-
posed body, or over its surface. The rapid i)^
proximation of the discharging rod is necessary
to ensure the full force of the. charge, a part of

440 JTAtUBJi 6r A ttucvir.

which- would otherwise pass silently without
pFoducitig any (perceptible effect.

The foimation of a circuit has been defined
(when treating of the action of the discharging
rod) to be the annihilation of all distance between
the metallic coatings ; it will consequently ht
produced most rapidly through the best con-
ductors, and prefer the shortest possible course;
hence if a person hold a wire between his hands;
whilst with one he touches the coating of ai
charged jar and brings the other to its knob, he
will feel no sensation but at the points of con-
tact ; for the electric fluid having the choice of
two circuits prefers the best conducting, and
passes through the wire without affecting the
body of the person that holds it* If he, how-
ever, substitute a piece of wood for the wire,
a shock will be felt ; for dry wood is a worse
conductor than the animal fluids, and the charge
having two circuits^ passes through that which
affords it the easiest passage.

This fact is well illustrated in every method
of communicating the electric shock, which is
only felt along the muscles in the most direct
line that enters into the circuit. Let A, B, C,

NATUB£ OF A CIBCUIT. 441

D^ £i and F, hold each other by the hand, A
having the outer coating of a charged phial in
bis hand, the knob of which is to be touched
by F; each individual will be shocked in the
sam?^ manner^ and at the same time, the sen-,
sation reaching from hand to hand through the
arnps, and, if the charge be strong, across die
breast These are the parts of the body that enter
dir^ptly into the circuit Vary the experiment;
A holding the phial as before, and touching tl^e
right foot of B with his left foot The left foot
of B to touch the right of C, and so on to F,
who. is to complete the circuit, by touching th0
knob of the phial with his left hand : A will be
shocked in his right arm and left leg, B^ C, D^.
^nd £ in both legs, and F in the right leg and
left arm; so that the charge passes in the
most direct line from one point of contact to
another.

The extent to which a charge may be con-
veyed by good conductors is remarkable. At a
very early period the Abb6 NoUet communicated
an electric shock from a small phial to 180 of
the king's guards, and afterwards to a convent'

I: * •

of Carthusians ; and the sensation was felt by all^

143 l^At&R£ O^ A CtftCUIT.

tlie .persons forming that extensive circuit at
the same moment. -

Experiments have been made to ascertain
the velocity Mrith which an electric charge
moves^ but hitherto without success. Dr. Wat-
son tmd some other members of the Royal Sth
tiety formed a circuit, with iron wires, of up-
wards of four miles extent, but the charge re-
^uir«d no. appreciable time in passing through
this lengthened interval.*
* The tendency of the charge to pass through
the best conductors, offers a measure of con-
ducting power ; for if various substances of th^
same length and size are introduced at once into
a circuit, that through which the electric fluid
passes is the best conductor. Or if they are

introduced successively, that which conveys the

»-■.....■

* There is some doubt as to the accuracy of these experi-
ments ; they were made at a very early period, and have not,
r believe, been repeated since the improved state of the science
has afforded the tneans of effecting such experiments with pre-
cision. Metals, although the nM)st perfect conductors we have^
oppose some resistance to the motion of electricity, and a charge
viH even prefer a short passage through air to a circuit of 20 or
30 feet through thin wire. It is therefore rather uncertain that
the charge of a small phial has ever passed through an interval
of foiM: miles. *

VAEIETIES OF THE CIECUIT. 14S

charge most completely may be considered the
best conductor.

To transmit the charge with more certainty
and precision, an ingenious apparatus was con-
trived by Mr. Henly : it consists of a mahogany
board, 14 inches long and 4 wide, having ^
socket fixed in its centre, to which may be al*
temately adapted a small table with an ivory top,^
or a mahogany press. Two wir^s, sliding in
spring tubes, and mounted on universal joints,
are fixed to the top of two glass pillars, which
are cemented near the extremities of the mahor
gany base at equal distances from the central
socket The body through which the chiirge
is intended to be passed is placed on the table^
or screwed in the press, which is then adjusted
in its socket. The sliding wires, which are
moveable in every direction, are th^a brought
in conta:ct with its opposite sides, and one of
theiH: being connected with the outside of a jtf
or battery, and the other with the discharging
tpd or a discharging. electrometer, the charge ill
determined through it with great accuracy •--<9
The instrument is represented by Vijg. 24 : it is
called the Universal Discharge^

114 ELECTBICAL APPARATUS.

When electrical sparks are intended to be
passed through various substances, their action
may be rendered' uniform by receiving them on
an insulated ball, in contact with which the 8u]>
ject of experiment is to be placed^ and its op
posite extremity connected with the ground;
t}i^ insulated ball should be of the same height
with the conductor of the machine, and, being
fi^ced on a separate stand, may be placed at any
required distance from it ; by which means the
sparks may be made stronger or weaker at
pleasure. .

. When the electrical spark is to be passed
Ithrough different fluid or elastic mediums, these
substances are enclosed in glass tubes, and two
wires are inserted through the opposite sides or
ends of each tube, so as nearly to meet ia its
f^enti'e;. between these wires the spark is to be
passed, suid an experiment of this kind may be
continued for any time without opening the
«esseiLr-*See Figures 25 and 26.
? , When fluids are acted upon in this way, they
ari^ sofnetimes placed in a tube, closed at one
4e|i4i through which a platina wire passes, and is
continued through the centre of the tube until

£L£CTKICAL APPARATUS^ 145

it comes within a short distance of its open
cxtrieraity: the tube being inverted in a- brass
dish, sparks may be transmitted from the point
of the wire to the bottom of the brass cistern.
Sipc Fig. £7.

' It is evident that apparatus of this kind
may be modified to any extent, and that the
construction of it is, for the most part, exceed<»
ingly simple: the agencies of electricity, in
altering the forms or characters of other mat-
ter, arc only exerted when it passes from one
body to another ; so that an interrupted circuit
is essential to every electro-mechanical and
electro-chemical apparatus.

Tubes of glass, wires of different metals^
corks, and a few other materials, are adequate
to the construction of an endless variety of elec*
trical machinery, and the proper direction of
such resources is constantly followed by use^
ful discovery. Mechanical dexterity is there-
fore essential to the character of an electrician,
since his progress will be in proportion to the
facility with which he can adapt the objects
around him to new inquiries. He cannot
deviate from the beaten track of his prede*

IA6

ELECTRICAL APPARATUS*

cessors vt^ithout the aid of ne\^ combinations ;
and when thfe supply of these is derived
from his own industry and ingenuity, the
ardour of his pursuit will be unimpeded by the
delays or mistakes of others ; and thfc prbjco-
tioh^of ahy required improvement may conse-
quently be followed by its ittimediate consume
mation* ^

147

CHAt. n.

t - ...

Mechanical Effects of Electrkit^i

'•• ,'<.| . ,...■

-JLre tranttmisskm of the electric fluid fromont
body to another is always atteiided.by SQm^
mechanical effect^ when its motion is ftlow^
light substances are moved by it or currents oi^
air produced; when its motion is rapid, light is
evolved and a sharp sound ensues. The sound
is produced by the sudden collapse of the ^if)
which has been displaced by the passage of the
ejedtiric fluid ; and it is consequently greater isi
|>ropbrtia& tp the quantity and intensity of the
chai^Ci Hence when different s>zed jaxs are
charged to the same degree, and then succes^
lively diischarged, the explosions produced will
be louder in proportion as the jars 9re larger |
and the effect afforded by a battery of exten-
8i>^e sur£ic^ will be that of a <x>tnpaTatively
violent leport

The immiediate consequence of the passage
i^( all dectric charge thvough any mibstancCj
kfpeats to be ati exipttnsiott or removal of the

148 HECHAMICAL I^FFECTS OF ELECTRIC ITT.

particles directly in its course, and a consequent
compression of those by which they are sur-
rounded : so that the resplt of an electrical ex-
plosion is usually some evidence of the action
of an expansive power.

Experiment 49* Place a card, or the cover
of a book, flat against the outer coating of a
Leyden jar, exposing about a square foot of
coated surface; put one extremity of a discharg-
ing rod against the card, and bring the other
extremity to the knob of the jar : the charge
will pass through the card and perforate it, pro-
jducing a small bur or protrusion on the side
next the discharging rod, and a larger. bur. on
the side which was in contact with the coating
9f the jar. By employing a battery, a quire of
Strong paper may be perforated in the same
manner; and such is the velocity. with which
the electric fluid moves, that if the paper be
freely suspended, not the least motion is com-
municated to it

. Eaperiment SO. Put a piece of dry writing-
paper on the table of the universal discharger,
and, removing the balls from the ends of the
sliding wires, press them upon the paper at the
4Mtance of about two inches from each other ;

tXPANSiVE POWER OF ELEdTRICITY. 149

J>^ a strong charge from one wire to the other,-
and the paper will be torn in pieces. If a num?
her of wafers are placed on the table instead of
the paper, they will be dispersed in a curious
niiEinner, and many of them broken to pieces
when the charge is passed through them.

Experiment 51. Drill two holes in the oppo«
site ends of a piece of wood which is half an
inch 'long and a quarter of an inch thick ; insert
two wires in the holes, so that their ends within
the 'wood may be rather less than a quarter of
an inch distant from each other : pass a strong
charge through the wires, and the wood will be
split with violence. Loaf sugar, stones, and
many other brittle nonconductors, may be broken
in the same way, if a sufficiently powerful charge
be employed.

Eaperiment 52. Introduce two wires into a
soft piece of pipe-clay, and pass a strong shock
through them : the clay will be curiously- ex-
panded in the interval between the wires. The
experiment will not be successful if the clay be
either too moist or too dry.

Experiment 55. Insert two wires through
corks in the opposite ends of a small glass tube;
let the distance of the ends of the wires be

19Q f:XPAVIfV£ TOWER OF ELECTRICITY*

about hdf an inch : fill the tube with water, wi4
pa3S a moderate charge through it ; the tube will
\^ brokeii and the water dispersed^

The expansion of fluids by electricity is in*
deed very remarkable, and productive of some
singi^lar resi|Its. When the charge is st^Fong^
HQ glass v^sel can resist the sudden impulse,
Beccaiia inserted a drop of water between twci
yrires in the centre of a solid gl^s ball 0f two
indhes diameter ; on passing £^ shock tbiXMigh
the drop pf water the ball was dispersed with
gre^ violence. Mr. Morgan succeeded, by the
same means, in breaking green glass bottler
filled with water, when the distance between
the wires that conveyed the spark and the aides
of the glass exceeded two inches. With but a
pioderate charge I have, in this way, broken glaftii
tubes the thickness pf half an inch in the sides,
Snd with a bore pf the same diameter.

Experiment 54. Place a piece of plate glass,
about an inch square and half an inich thick,
within the press of the universal discharger, pf
lay it flat upon the small table and press it by
a weight ; set the points of the sliding wires
opposite ' to each other, and against the under
edge pf the glass, so that the spark may pass

ZXPA1I.8IVE POWER OF ELXGTRICITY» 151

Jbei]beath it : the charge of a large jar, transmit*
led in this way, rarely fails to break the glass.

JEo'periment 55. Form a small mortar of ivory^
with a cavity of half an inch diameter and an inch
deep ; insert two wires through the sides of the
mortar, so that their points within its cavity
may be separated by an interval of a fourth of
an inch; fit a cork cap so as to close the aper*
ture as accurately as may be without friction :
when a strong charge is passed through the
wires, the air withinside the mortar i$ suddenly
expanded, and the cork is projected to a distance
witli some violence.

Eaperiment 56. Let a spherical cavity be
turned in a piece of ivory capable of receiving
the half of a light wooden ball ; a small conical
cell is to be made at the bottom of the spherical
cavity, and two wires inserted through the sides
of the inortar into it: if a drop of water, oil,
alcohol, or ether, be put between the wires, and
the ball placed over them in its cavity, a charge
sent through the drop of fluid will convert part
of it into vapour, and expel the ball with coii«
siderable force.

If a discharge be passed over ice, the surface
is sometimes marked with .«pots, as if a hot chain

15S EXPANSIVE POWER OF BLECTRICITT.

had been laid upon it ; if it be passed over snow;
it divides the portion over which it passes; when
it is taken over the surface of soft dough; a per-
manent depression is made in the track of the
discharge ; and when it passes through a green
leaf, the leaf is torn to pieces. Hence it appears
that an expansive effect is produced at every
interruption of the metallic circuit, or when the
electric fluid elicits light during its passage; and
this expansive power produces a mechanical
effect proportioned to the nature and resistance
of the medium in which it occurs. Even, the
best conductors, when in a sufficient state of
tenuity, are considerably exp>anded by electri-
city. Let a capillary tube of glass be filled with
mercury, and pass a charge through it; the
mercury will be expanded with sufficient force
to splinter the glass tube.

. Electric light is evolved at every interrup-
tion of a metallic circuit, even in conducting
fluids when the charge of a jar is passed through
them. This experiment may be made with water
in a thick glass tube, having two wires within
it with their ends almost in contact. A mode-
rate charge will produce a bright spark ; but no
more power should be employed than is absor

ElfiFSCTS or THE BLECT&IC OHAftU^ \SS

lately necessary for the purpose, as there is some
danger of breaking the tube. A very low charge
niay. be first employed, and if it is found insuf-
ficient, it may be gradually increased until the
required power is obtained.

In oil, alcohol, or ether, the spark is more
readily, procured, as they are better insulators ;
^t the expansibility of these fluids renders the
experiment ev^n more dangerous with them than
with water. As the difficulty of eliciting elec-
tric flight in any medium increases with its con-
ducting power, a much higher charge is required
to procure' a spark in hot water than in cold :
in. saline fluids the difficulty is further increased;
and in concentrated acids, light can only be
procured when their volume is comparatively
trifling. .

The effect of some of these fluids on the
striking distance through air is very remarkable.
Dr* Priestley first remarked, that the explosion
from a large battery would pass to a grater
distance over the surface of water than in the
free atmosphere. This fact is best exemplified
in the following manner.

Experiment 57. Draw a line with a pen
dipped in water on the surface of a strip of glass;

)3tfp Bi»CT8 Of THE ELECTftXC CUABGE.

place one extremity of the line in contact with
the coating of a Leyden jar, and at six inches
difttaiice upon the line place one knob of tbe
discharging rod ; when the jar is fully charged
bring the other knob of the discharger to the
bftU of the jar, and the discharge will take place
luminously over the six inches of water.

E^xperment 58. With a pen dipped in sii^
phuric acid trace a line on a strip of glass, as in
the former experiment, and place one extremity
of it in contact with the outside of the jar ; the
ball of the discharger may be placed on the strip
at twelve inches distance, and the electric fluid
M'ill pass as brilliantly over that interval as over
the six Inches of water.

In either of these experiments, if the strip
of fluid be wider in any particular part, the light
lof the discharge will appear less brilliant in
passitig that portion ; which may arise from the
greater division of the fluid when passing over
nn extended conductor than over one that is
narrow.

The great mechanical power evinced by the
electric fluid in these experiments, is a strong
proof of its claim to the character of a material
substance ; and the impermeability of noncon*-

EFFECTS^ aF THE ELECTRIC C^ASft^ l^$

ductora to it, when in tlfffi penGpt^ «tat§, i^
abewn l>y the mecb2^8k»d;iD|iy|r they «usta49
when, hy reducin^f them tp sufficiently thu|
lamina^ a strgfifg electric ^a»?g^ i^ conveyed
through tbefn«

Tbr hardest ttp^ipaost compact bodies may»
bjr sucb^ rne^ui^ lie broken or perforated;. Init
£pom the \ft0iuencc of surface^ or other eay^es^
their r^M^anpe is not always proportioned t^
tlifljrjilksulating powers. The perforation of solid
l|pconductqrs is effected with the lea^t pow9?
^hen the discharge is confined to a single poinjl^
aiKi prevented from disj^rsion by being \snr«
ipounded by some nonconducting matter ;^ %$
may be thus exemplified.

Experiment 5&, Fill a small phial with olive
oil» and introduce within it a pointed wire bent
at right angles, so that by sliding through a cork
placed in the neck of (he phial the point of the
wke^ mdy be made to rest against any part of its
inside beneath the oil : suspend the phial by ita
wire to the conductor of an electrical machine^
and place the knuckle or a brass ball near the
Outside of the phial and opposite to the point of
the. wire that is within it ; a spark will pass from
the point to the knuckle, and make a small holf

156 £f FBCTS OF TH£ ElECTBtC CHABGCJ

in the glass. By turning the point round, or

raising it higher or lower, many such holes may

be made.

The point serves as an internal coating to a

very small portion of the glass, and the charge

• • . ■ . • ■ »

being prevented fVom extending by the sur-

rounding oil, the whole power of the machine

is concentrated to that point, and consequently

• • • * _»

soon overcomes its resistance. Similar effects

will ali;^ays ensue when a large quantity of elec-
tricity is suddenly transferred to a compara-
lively limited surface. ' '

Experiment 60. Charge a very large jar;
connect its outside with one that is ten or twelve
times smaller : make a communication between
their inner coatings with the discharging rod,
and the small jar will be broken; the quantity
of electricity transferred to it, being beyond
the proportion of its size.

To ascertain the resisting faculty of various
substances, a pointed wire should be procured,
and surrounded by a cylinder of wax or pitch,
which, being softened, may be applied to the
surface of a lamen of the substance to be tried,
and will confine the action of the point to one
part of that surface; the opposite side of the

£r«£CT8 OF THB. ELECTRIC CHAmGE. 157

resisting plate is to be connected with the out>-
^ide of a charged jar, and the discharge made
through the point In this way Mr. Morgan
ascertained that of bees'-wax or sulphur, a plate
of S-lOths of ail inch thick could be perforated
.by a high charge; whilst of plate glass 3-20ths
of an inch was the greatest interval that could
be: overcome by his apparatus ; and of shell-lac
only fl-SOths of an inch were struck through.
Hence, for its practical application, shell-lac ap^
pears CNae of the best nonconductors we have. ,

Many substances, that are tolerable con-
ductors of electricity, may be also perforated
by jan electric charge, when its action is ci^n-
fined to one part of their surface ; such is i|sually
the case with the tinfoil coating of large jars,

if^ when they are highly charged, the discharge

■• • •

is made.by touching the tinfoil only in one place
with. the discharging rod; the little spark that
occurs at the point of contact fuses the tinfoil^
and a slight adherence is almost always observe4

•i >

in. consequence, between the knob of the dis^
charger and the coating after every discharger
QQiis property may be thus exhibited.
-Experiment 61. Charge a large jar, w4
place, a shilling or other piece of coin be^ivea^

158 SfFXCn Olf THb ELECTaiC CHAME«

i^ kdob of the discharger and the coating cf
th^ jal* : when the discharge is made the eoili
^iU be slightly soldered to the tinfoil by its
ffn^H at the point of contact, and will Te^hnia
kdhering to the coating after the discharger is
temoved.

The mechanical effects of electricity hav*
%een employed to indicate the course of lilt
diectric fluid in the discharge, and thus to 6im*
firtn the proposition that assumes positive deo*
tricity tb be an accumulation of tlecUic fleid^
mid negative electricity to be a deflcietiey ; m
bppositioil to the hypothesis first proposed by
Dii Faye, that positive and negative are two
distinct electric powers.

It has been already shewn, that the pbeno*
mena yet considered indicate the agency of
bnly one fluid ; and the effects attendant on the
transmission of the charge will be found to af-
ford tile same indication, although some of them
nave been differently interpreted by some inex-*
perleneed electricians. There is, probably, no
tfCience in which manual dexterity is more essen-
tial to successful inquiry than that of electricity;
CK^ fikt& that constitute it are also numerous
iBId of tit versified character, yet so depemkiit

DtmXTIOH OP THE £L£CT RIO FLUX D« 1J^9

im ^ach other, that uatil their mutual relations
ai*e undclrstoodi and all the intricacies oF^eleo^
ttieal action clearly comprehendedi no just ap«
plication of its principles can be effected. It
is therefore, perhaps, not very surprising that
the tyro^ when he attempts to reason from a
limited range of observation, is frequently led
to adopt erroneous conclusions, which have mi
other foundation than in the inaccuracy of tiiis
experiments be may have made, and in his wafi^
of skill ill the arrangonent, classification^ and
comparison of phenomena^ ^

' Kxperment 62. The direction of the deetric
fluid is rendered visible when a Leyden jar;
which has been rendered slightly damp by
breathing oh it; is placed with its knob in con-^
tact with the positive conductor of the machine,
in a darkened room : when the jar is fully chiM*g^
ed, if the turning of the machine he continued^
the electric fluid will be seen to pass from the
itme^ tO;. the outer coating over the uncoated
interval in luminous streams, producing an eflect
similar to that of water overflowing from the
top of a vessel that is kept const;antly supplied;
If*tbejar be removed^ and its knob placed
AgAiiisi the> negative cqndtkci^xr, the ittream^

Ij60 DIRXCTIOH OF THB ELJICTRIC FLUID*

when the jar is overcharged, will evidently pass
in the contrary direction, that is, from the outer
to the inner coating. A certain degree! of dam^
ness.on the uncoated part of the glass is neces-
sary, in this experiment, to prevent the discharge
of the jar hy spontaneous explosion, in whiqh
case the fluid passes too rapidly from one sur&^6
to the other to admit the ascertainment of its
direction. If the moisture be hot sufficient,
divergent brushes of light pass from the posi*
tivc surface at intervals, instead of tlie continv*
ous streams before described.

Experiment .6^. Let a small jar be charged
positively on the inside; place it under the re-
ceiver of an air-pump: on exhausting the air,
brushes of light will pass from the knob of tlie
jar to its coating. Repeat the experiment with
a jar charged negatively; the direction of the
flashes of light will be reversed.

Experiment 64. Place a lighted taper be-
tween the wires of the universal dFscharger, they
being at four inches apart, and the flame, mid-
way between them; connect the coating of. a
small charged jar with one; wire, and bring its
knob in contact with the other : if the charge
be just suflScient to pass the interval without

t^IRBGTION OF THE ELECTRIC F£UiD< \6i^

explosion^ the flame of the taper ivill be ppn*»
s tartly blown from the positive wire tp th$fe
which is negative. ' . t

Experiment 66. Lay two very straight sticks
of sealing-wax on the table of the discharger
parallel to each other, so that the juncture of
their rounded edges may form a groove ; on thiii
a large pith-ball is j^o be placed, and the wire9
of the discharger are to be arranged with their
points in. the direction of the groove, and at fou.^
inches from each other, the ball being equal!}!
jdistiwt from each. On passing a ^mall charge
fVom one wire to the other, the ball will bedriveiv
from the positive to the negative; and this ef?
feet >vill be constant if the terminations of the
vires are pointed, which they should be foy
these experiments of transmission. If blunted
wires are employed, the ball frequently vibrates
between them, and apparently renders the result
equivocal ; but it should be recollected, that by
employing knobbed wires, the transmission of
the charge is prevented; and, as the wires .are
i^onnected virith the opposite sides of the jar, they
must necessarily attract the ball alternately, a^
liny other oppositely electrified conductors would
4fii : Ag^^i it niay s^lso ]i>e p]>servedv that

f63 DllitCTlOir OV THE ELECTRIC WtOtH.

with pointed wires the motion of the ball is not
ilways in the supposed direction of the fluid;
for if it be placed in contact with either mre^ it
will move Jratn that wire as soon as the circuit
is cbmpleted, whether the wire be in contact
with the /^/Virf or negative side of the jar; but
this, when attentively considered, proves nothing
relative to the course of the fluid ; for the ball
becoiiies electrical by its contact with the wirei
and consequently recedes from it toward tilt
oppo$ite surface, by which it is then ettrMte/L
That attraction is the cause of this apparent
anomaly may be proved by making the expeii^
ment with a jar exposing about a square foot of
boated surface, which is to be moderately charg-
ed, first with positive electricity and then witix
negative ; its outside being connected with the
wire toward which the ball is to move, and llie
circuit completed with the discharging rod, by
tonnecting the opposite wire (against which the
pith-ball is to be placed) with the knob o^the
jar. When the charge is positive, the ball may
be made to recede from the wire three or four
times by one charge, if it be replaced after each
contact of the discharging rod; but when the
Charge is negative, it will recede but once : tibe

JbiRBGTioN Of the blsctric Fi^xp. 1^9

€»Di8e of the ball's motion in these two instances
IS tiienefore different ; in the latter it is attri^o
tion ; in the former a continued current of elecr
tricity. In either of these experiments, if ji
strong dbarge is employ ed$ the ball will be enr
tirely driven out of the groove.

The perforation of a card, or of paper, by
tihe electric explosion, has been also proposed
as a test of the course of the electric fluid ; but
the efi^ct of expansion interferes very much
with its results. Two burs, or protrusions, wp^
mlwagrs^ pmduced ; but Mr. Gough has lately
iAewn that when the experiment is made with
acccntcy, the bur on the positive side is con*
jUtuMy the smallest; and a hole made in card-
fmper by a punch exhibits a similar result, a
iltaaU bur l}eing raised on the side to which the
piunch is applied, and a larger bur on the oppo«
jite side.* I have been informed, that when »
iwllet 13 discfaiarged through a sheet of copper
.asialogQPiis i^pearances are produced; and on
mMxig thii experiment of electrical perfoi^Htipu
mx mmiy todies, less expansible than card, .the
jmycationa were decidedly in favour of a current

f Nidipls(m*s Jouonal^ .vol. xxnii* p. i7^'

M 2

164 JDIRBCTtOK OF TBB ELICTRIC FLQItf.

from the positive to the negative : such is pat>
ticularly the case when a sheet of tinfoil or of
thin lead is pierced; and it also occurs rwrith
thin pieces of Wax or dry soap* These appear^-
ances are best observed with a magnifier after
the explosions have been taken*
\ Mr. Symmer made the experiment of per-
foration with a paper book, in the middle of
•which he placed a sheet of tinfoil; on pitssing
^an explosion through them, the leaves were
perforated, and the tinfoil indented in opposite
directions; hence. he concluded there was iEi
double current, one fluid proceeding from the
positive and the other from the negative*
If this experiment be attentively considered^
it will be obvious that, by the interposition of
the tinfoilfz, double interruption in the metallic
circuit is produced : now it has been already
shewn, that at every such interruption a ^Hirk
^and an expansive effect invariably appear ; con-
sequently such an expansion must have occurred
in the paper on each ^ide of the tinfoil, and the
' perforation and burs prove that it did so : now
• the expansion of the paper in this way must

* Pha. Trum. ?o1. li. p. 371. : '

DlEXCTlOlf OF 7HK. Bt£CTJIXC f JLITIP4. lOSi,

Becessarily effect an indentation of the tinfoil
oppfosite to it, and the indentations being on-
each side, from the paper to, the. tinfoil, mm%
of course appear in opposite directionsi^ . Hence
it is evident that Mr. Symmer mistook the ex-t
pansive effects of the electric fluid for an indit
cation of its direction; and his mistake has beeQ[
ingeniously amplified by Mr^ E, Walker, in ft
f^ent number of the Philosophical Magazine**
^ Mr. Cavallo discovered th^t some mineral
c^olouTS are affected by the passage of an electric
charge over. them; apd this circumstance may
be applied to shew the track of the fluid in pass-^
ing from one side to the other of a card or thick,
{>aper, when the transmitting wires are ^t aomc
distance from each other. ,

.' Esepcriment 66. Colour both sideaof a card
frith vermilion, and place it upon the titble of
the universal discharger; one of the wires should
be beneath the card, and the other in contact,
with its upper side ; the distance of the points
of the wires being one inch. If a charge be now
passed through the wires, the fluid will pass
from the positive wire across the surface of the
*• • ■• ■ • . »

. ' : . * P^ Map. vol xUL p, \6U

tBtd to the part over the negative wive, v^d it
will there perforate the card in its passage t9
the negative wire. The course of the fluid is
permanently indicated b^ a neat black Hne on
the card) reaching from the point of the posi^
tive wire to the hole ; and by a diffused black
mark on the opposite side of the card around
the perforation, and next the negative wire*
These effects are very constf^nt, the black line
always appearing on the side of the card which
j$ in contact with the positive wire, and tlic pcr^
foration being near the negative wire.

I hav^ lately contrived a means of demon'^
strnting the direction of the electric fluid by its
mechanical impulse, which confirms the general
bearing of the preceding facts, and illustrates
the assigned cause of their apparent anomalies.
It has been long known, that a light float wheels
made by inserting several vanes of card-paper
in the periphery of a cork that turns freely on
a pin or center^ will be put in motion by pre^
sen ting it to an electrified point ; and the motion
of the wheel being always^mw the point, whe-
ther that was positive or negative, has been
occasionally urged as an argument for a double
current of electric fluid ; although it is evident,

Ifpp whftt hits l)«e]i pi^v^iously ^t^t^, that i^
ji€ik]t» mther positiTf^ or negative^m^st produce
« cmrrwt by t^; rec^ssipi^ of the /^r oppoae4 tc^
H wben similarly electrified by its contact; which
i§ fully ad^uate to th^ prodDctjoB of these ef;
fect^. CotijecturiQg ^at the currents of eilec?
trijgisd alt would not tal^e plac^ in this mannet
if the points w0re opposed to each other^ I inad#
the following arrangement

JSljfperiment 67. A light float wheel, of the
prcK^eding description, being mounted so as tiai
turn^r^^ between two upright wires, is placed
on an insulating stem, and introduced between
the pointed wires of the universal discharger^
which are to be placed aa accurately as po/isiblo
opposite to each other, and at the distance of
an inch or more from the upper vanes on. their
ra$pective sides. — See Fig, 28. Now it is evi-
dent, from this disposition of the apparatus^
that if there are two electric fluids moving in
(jppasite directions, the wheel being efualfy acted
on by each, will obey neither, and remain sta^
tionaiy; but if one only exists, it will receive
aiotion in .the direction that fluid passes. Con*
sect one of the pointed wires with the positive
oonductor of an dectrical . machine, and tho

f 6s DIKECTIOK OF THE ELECTKICf FLITIll*

Other with the negative conductor ; as soon at
the machine is turned the wheel will move, thd
direction of its motion being frmn the pasifioe

m *

to the negative wire. Reverse the connections,
so that the wire which was negative shall be«
come positive^ and that which was positive h6
^rendered negative; the motion of the wheel
will be reversed, for it will still turn ynwi the
positive to the negative ; proving that the elec*
trie fluid actually moves in that direction. A
similar effect will be produced by the discharg<{
of a js^r, provided it be insulated during the dis-
charge, which is necessary to insure the tranfc-
iiiission of the charge from one wire to the
other, as it would otherwise be dispersed, by
passing in various directions to the conducting
bodies in contact with the outside of the jan

^ Experiment 68. Place a card vertically, by
inserting it in a small piece of cork that may
for^n a base of about a quarter of an inch wide
for it to stand on: the base should be barely
sufficient to support the card in its vertical po-
sition, so that it may be overthrown by the
slightest impulse. The pointed wires of the
universal discharger being opposite to each
Othery and s^t about four inches distance, the

DiEitTioN Of Tiaiet EtECTftitf wlviik -tB9
^rd is to be stood upright on the table between

• • • • •

them, and its height so adjusted that the line
of direction between the wires may be about a
)q[daHer of an inch below its top edge. If the
wirtsbenow respectively rendered positive and
negative, either by connecting them with the
Opposite conductors of the machine, or bring-
ing them in the circuit of an insulated jar, the
l5ard will be thrown down, and constantly fall

frcm tlit positive to the negative, changing its
direction when the electrical connexions of the
wires are changed.

If, instead of being placed midway between
the wires, the card be put in contact with either
of them, it falls Jrem that wire, whether it be
positive or negative ; but this arises from the card
being an imperfect tonductory and consequently
becoming electrical at its point of contact ; as
may be proved by covering it with silver leaf,
which, by rendering it uniformly a conductor^
prevents this effect. It will then remain erect
if placed in contact with either wire, and fall
froni the positive to the negative if situated at equal
distances from them.

Such ^re the leading mechanical phenomena
of electricity, and such the indications they

170 XNLUXTSOM OF THE £L10T>IC WhVllh

afibrd of the materiality of the electric . fluids
and the nature of its diffusion and transmissicm^
When the subtlety of this agent is considered^
it must be admitted (I should presume) that w«
have few instances in philosophy where the ac--
tion of an invisible power is so clearly define4
by its effects; or where those effects tend sq
uniformly to one inference, as to render tht
phenomena intelligible by the mere exposition
of their mutual relations and connexion.

•t

. k

171

CHAP. III.
Ciaaical Effect* ^ ElectrkUy.

X H£ ageiicy of electricity, in the producticm
of chemical changes, is even more remarkable
and extensive than its mechanical power, and
probably arises from the same cause. The most
obvious and simple of them are connected with
the appearance of light and the production of
heat; and may therefore arise from the rapid
motion of the electric fluid through the particles
of other matter : for light and heat are also och
casionally observed during the sudden mechar
nical compression of all elastic bodies. The.
simple motion of electricity through air is ao-
companied by a rise of temperature, as may be
observed by introducing the bulb of a thermo*
meter into the luminous current between two
oppositely electrified balls of wood. The spark
dr explosion, and indeed every appearance of
electric light, is accompanied by a peculiar
sme}l^ which has been considered as indicating
tbaA such appearances are the result of a species

173 CBBMICAL EFFECtS OF ELECTRICITY.

of combustion; but the continued appeai*ance
of the spark in a confined portion of air, in
which it produces* only a lii^ited change : and
its production under the surface of water and
other fluids/ militates strongly against ^his con-
clusion. In its concentrated state, electricity
is capaUe of inflainin^ most combustible bodies,
if passed as a spark through a stratum of air in
icontact with them ; and any idea of the diirect
agency of beat, in the production of these eff
fects, may be obviated by the transmitting com
ductor being formed of bodies that would ab-
sorb; it.

i Eaperiment 69. If ether, or highly rectified
-spirit of wine, be placed in a metal cup insu^
4ated and electrified, a spark may be drawn from
ihc bottom of the cup through the spirit, by
•presenting to its surface either the finger, a
'brass ball, or even a piece of ice; and with any
•of these substances the spark will inflame the
volatile fluid. If the spirit of wine be not highly
:rectified, it .will be necessary to warm it modev
lately before the experiment; but this precau*-
tibn is never necessary with ether. *

; ;-. Hxperiment 70. Dry the outside of a wine
^lassj^ that its stem may serve as an insulating

CH£MICAl4*AOENCIESO.F BLECTRICIT7. 17S

Stand ; fill the glass nearly with cold water».and
on the surface of the water pour a stratum of
ether : connect the water, by means of a wire^
with the conductor of the machine ; when that
is turned, if the knuckle be presented to the
aurface of the ether, a spark will pass from the
water to the knuckle, and the. ether will be set
on fire. ■ ' . . < . -

' '^ The same effect will take place if a seriet
of glasses, filled with a freezing mixture, and
connected by wires, are employed to transmit
the electricity from the machine to the water :
so that it is evident the absorbing power of the
intervening conductor does not prevent the
power/of the sparks

Experiment 71. Fill a flat porcelain dish
with water, and on the surface of the water
Btrew a quantity of powdered resin: place two
wires at the opposite sides of the dish, with their
ends near the surface of the water, and at fetir
or five inches distant from each other : pliss tfa^
charge of a jar from one wire to the other, and
the resin in the track of the explosion will be
inflamed. Similar effects are produqed vfaen
the resin is strewed on the surface ^f f /tciii|[]|^
piece' of wo<k1. or a.l<)Qse ball of tottott..

174 FUSION OF METAtS.

Phosphorus placed in a Itttie tin cup floats
ing on water may be also readily inflamed, by
passing a current of electrical sparks ov^er its
surface.

The most remarkable effects of combustion
that are produced by electricity^ result from its
action on metals. Dr. Franklin was the first
iKrho observed these effects: his experiments
were first extended by Mr. Kinnersly and by the
edebrated Beccaria ; and have since been pur*
sued with great accuracy by Mr. Brook, Dr. Van
Marum, and Mr. Cuthbertson.

Experiment 72. Place a strip of silver or
gold leaf on white paper, and pass a strong shock
through it: the metal will disappear with a
bright flash, and the paper will be stained with
a purple or grey colour.

Experiment 73. Take three pieces of window
glass, each an inch wide and three inches long,
place them together with two narrow strips of
gold leaf between them, so that the middle
piece of glass has a strip of gold on each of its
aides ; the extremities of the gold strips should
project' a little beyond the ends of the glass :
pjss the charge of a large jar through the gold
strips; they will be melted and driven into the

FUSIOK or MfiTALflk |7fi

superfices of the glass. The outer jUps of glass
are mually broken, but that in the middle fre-*
quently remains entire, and is marked with an
indelible metallic stain on each of its surfaces.

Experiment 74. The colours produced by
tile explosion of metals have been applied to
hnpress letters or ornaments on silk and paper.
The outline of the required figure is first traced
i>H thick <lrawing paper, and afterwards cut out
in the manner of stencil plates. The drawing
paper is then placed on the silk or paper inr
tended to be marked ; a leaf of gold is laid upon
it, and a card over that; the whole is then placed
in a press, or under a weight, and a charge from
a battery sent through the gold leaf. The staii|
IS confined, by the interposition of the drawing
paper, to the limit of the design ; and in this
Way a profile, a flower, or any other outline
figure may be very neatly impressed.

When a powerful electric charge is passed
through a slender iron wire, the wire is ignited
or dispersed in red-hot balls. Very large bat-
teries were formerly considered essential to the
^rod^etion of this effect ; but if the wire be su^
ficiently thin, a single jar, exposing a coated
Surface of about 190 square inches, will suf-

if$ jrusioK or s:je:tal$4

ficiently exemplify it. The finest flatted steel
•wire, sold at the watch-makers' tool-shops by,
the. liame of watch pendulum wire, answers ex-}
ceediogly well. Cuthbertson's Balance Etec:
trometer should always be employed to regelate
the. charge ; the circuit from .the inner to th^
outer surface of the jar should be as short ai|
jpossible ; and the wire intended to be melted
placed iu a straight line, and confined at the
^udjs, bet ween sxnall wire forceps. .

Edperiment 75. The. inside of the Leydeu
jar, and the bent arm of the eleqtrometer, being
connected with the positive conductor of an
electrical machine, and two inches of watch
pendulum wire placed by means of the wire for-
;ceps between the lower insulated ball of the
iclec trometer and the coating of the jar, the
slider is to be set on the graduated arm of thp
electrometer to 15 grains. The machine is t)ae^
tQ be put in motion, and when the intensity of
the charge exceeds the resistance of 15 grainsr,
the beam of the electrometer will descend, and
ihe;charge passing through the two inches- of
wire, will render it red hot, and melt it into
l)alls. .

Experiment 76. If the jar has not a paper

FUSION OF METAILS; 177

ring, it must now be breathed into, and eight
inches of pendulum wire heing placed in the
circuit, the slider of the electrometer is to be
set at thirty grains, and the turning of the ma-!
chine resumed : when the charge is sufficiently

intense, the beam of the electrometer will de-
scend, and the charge passing through the eight
inches of wire, will melt it with the same apr
pearances as the two inches in the last experi*
ment. ' '

Experiment 77. Arrange eight inches of wire
in the circuit, as in the last experiment; but
instead of one jar charged to thirty grains, em-
ploy two jars charged to 15 grains. The wire
will "be melted precisely in the same manner;
so that the effect is equally increased by doubling
the extetU of coated surface^ or the height to which
it is charged.

From numerous experiments of this kind>
it has been concluded by Mr. Brook and by Mn
Cuthfoertson, that the action of electricity on
y^ires increases in the ratio of the square of the
increased power ; since two jars, charged to any
degree, will melt four times the length of wire
that is melted by one jar ; and this will be again
quadrupled by doubling the height of thp charge.

178 nrsiOK or metals

This law, I have found, obtains in all accu^
rate experiments with moderate lengths of wire;
and it is ap{)arent, in Mr. Cuthbertson's experi*
ments, to some extent The batteries of his
construction usually contain fifteen jars, and
one of these will just fuse half an inch of iron
wire T4vth of au inch diameter ; but the whole
battery of fifteen jars will fuse sixty inches of
the same wire.*" I have made some experiments
with very slender iron wire (Tryth of an inch
diameter) on rather an extensive scale; but some
of the charge is lost in pervading a considerable
length of thin wire, and the explosion of the
battery (at other times remarkably loud) is then
scarcely audible. With a battery exposing forty
feet of coated surface I have frequently melted
eighteen feet of the last-mentioned wire by a
single explosion, and the phenomena were re-
markably brilliant, a shower of intensely ignited
globules being dispersed in every direction.

The preceding law of the proportion of ig-
niting power to the extent of coated surface,
and height of charge employed, varies when any
considerable difference exists in the thickness of

♦ Cuthbertsgn's Practical Electricity, p. 181, &c. or Nichol-
son's Journal, 4to. vol. ii. p. 525, &c.

FUSION OP METALS. 179

the jars made use of; as thick jars display the
same intensity with a comparatively small quan*
tiiy of electricity, and consequently have less
wire-smelting power. I have in my possession
a very large jar, which, from the extent of its
coated surface, should melt three feet of wire
with a charge of thirty grains; but from its
limited electrical capacity in consequence of
extreme thickness, it will melt only eighteen
inches ; and this is coiTcspondent to the con-
clusion drawn by Mr. Cavendish, that the quan-
tities of electricity required to charge different
coated jars of the same extent will be in the in-
verse proportion of their thickness.*

The fusion of wire may therefore be em-
ployed as a measure of the quantity of electricity
accumulated on any charged surface; for the
preceding experiments shew that any given
quantity of electricity will fuse the same length
of wire, whether it be disposed on two jars or one;
and hence it may be concluded, that the greater
6r less intensity of a charge does not materially
affect its wire-melting power. This test is there«
fore practically useful; for the various elec-
trometers nieasure only the intensity, and arc

* Phil. Tran9. vd. Ixvi. p. IQ6, &e.

N 2

180 FUSION OF METALS.

equally affected by one jar as by a battery of
one hundred. When the fusion of wire is em-
ployed as a test of electrical power, care should
be taken that the length of the circuit is always
the same, and that the degrees of ignition are
uniform; for a wire maybe melted. with but
slight variations of appearance when very differ
rent quantities of -electricity are passed . through
it. The lowest degree of perfect ignition ought
therefore to be obtained in all comparative ex-
periments, and its phenomena should be uniform;
that is, as soon as the discharge is made, the
wire should become red hot in its whole length,
and then fall into balls.

The effects of gradually increasing the power
of the charge, when wires of the same length
and diameter arc employed, are very remark-,
able. If the wire be iron or steel, its colour is first
changed to yellow, then (by an increased <;harge)
blue, by a further increase it becomes red hot, .
then red hot and fused into balls; if we con-
tinue to increase the charge, it becomes red hot
and drops into balls, then disperses in a shower
of balls, arid lastly disappears with a bright flash,
producing an apparent smoke, which, if .collect-
ed, is a very fine powder, weighing more than

-OXIDATION OF BIETALS. 181

the metal employed, and consisting of it and a

portion of the oxygen of the atmosphere, with

which it has combined. . ,

The conversion of various metals into earth*

like powders, of different colours, by exposing
them to heat, with free access of air, has been
long known ; and modern chemists have ac-
counted for such changes, by proving that a
peculiar gaseous substance, which constitutes
about a fifth part of our atmosphere, and is
called oxygen, is constantly absorbed by metals
when they lose their metallic appearance : and
they have shewn that such changes dp not oc-
cur by the mere agency of heat, unless air, or
soine other substance containing oxygen, be
present. Hence the substances that result from
the combustion of metals are called Oxides;
such is the red lead of the shops, which is an
oxide of lead ; the crocus of the shops, which is '
an oxide of iron; and the grey powder used by
lapidaries, which is an oxide of tin. These
changes do not occur to all metals with •the
same facility: platina, gold, and silver undergo
no change when expoaed to the most intense
beat ; and are therefore usually converted ijtito
oxides by the agency of acids, which afford

182 OXWATIOK OF METALS.

them dxygenc more readily : but by the power
of electricity all the known metals may be
converted into oxides, and the circumstances
of their change from the metallic state may be
accurately investigated.

The most complete series of experiments
that have yet been made on this subject were
instituted by Mr. Cuthbertson.* The apparatus
necessary for their demonstration consists of a
glass cylinder, two or three inches diameter and
eight inches high, mounted air tight with brass
caps at each end ; to the lower cap a stop-cock
is screwed, and in the inside of the receiver,
above the opening of the stop*cock, a small
roller is fixed, on which a quantity of wire (at*
tached to a packthread, that it may be readily
moved forward) is coiled. A brass tube, about
three inches long, is screwed into the centre of
the upper cap, and through this tube the end of
the packthread and wire is passed by means of
a long needle ; the tube is filled with hog s-lard
secured by cork, so that the wire and packthread
move through it air tight. The wire is by this
means extended in the centre of the receiver,

* Nicholson's Journal, 4to. vol. v. p. 136, or Cuthbertson's
Practical Electricity, p. 197.

OXIDATION OF MSTALS. 183

and when one length is exploded another may
be drawn forward by means of the packthread,
to which the wire is attached at intervals of
four inches ; and thus many lengths of wire
may be successively exploded without opening
the receiver. To ascertain the quantity of air
that has been absorbed during the process, a
straight glass tube» about 19 inches long, may
be screwed to the lower aperture of the stop-
cock;, the open end of the tube being tlien im-
mersed in a vessel of quicksilver, and the stop-
cock opened, the rise of the quicksilver in the
tube becomes a measure of the absorption. This
instrument is represented by Fig. 29, and its tube
or gage by A.
. The explosion of the wire alters the tem*
pierature of the air ^vithin the receiver consi-
derably ; it is therefore necessary, both before
and after the explosion, to lay the instrument
in a large vessel of water for some time, that
the measure of the absorption may not be ren-
dered inaccurate by the effect of expansion
that attends an increased temperature^ For this
reason a narrow receiver is preferable to a wide
one, for the temperature of the air within it is
more easily restored ; and the apparent anoma-

184 OXIDATION OF METALSi

lies that attended Mr. Cathbertton's first ex*
periments are thereby more effectually pre-
vented. .../..-* ;.-.. >

If- the air rema.ining in the receiver, aiftertf'
sufficient number of explosions, be examinecl, it
will be found to have lost a portion of its oxy-
gene. And if, instead, of atmospheric ^iiir, the
receiver be filled with hydrogen or nitrogen, no
oxidation of the metal will take place ; but it
win be fused, and very minutely divided, c >

The power of a large battery is necessary
for the oxidation of metals, as to accomplish it
completely, a higher power is required than
that which is adequate merely to their fusion ;
the quantities of electricity required are not the
same for every metal. Annexed is a statement

of the comparative charges employed by Mr.

Cuthbertson ; the length of each wire exploded
being ten inches. The column A expresses the
diameter of the wire in parts of an inch. The
column B the number of grains with which the
electrometer was loaded; and C the colour of
the oxide when collected in the receiver. The
coated surface employed in all the experiments
was the isame ; a battery of 15 jars, exposing
about 17 feet of coated surface. .

OXIDATION OF METALS;

18S

Lead wire . . ^ • • • 20 • . . Light grey.
Tin wire • » . ^ . . • 30 • . . Nearly white. >
Zinc wire . . • ^ . . . 45 . . . Nefirly white. ■>■
Iron wire . . . ^^ ... 35 ... Reddish brown.-
Copper wire . ^^4^ ... 35 . . . Purple brown.
Platina wire . -j^ ... 35 ... Black. — i
Silver wire . . tttt • • . 40 ... Black.
Gold wire . . -r^. . . 40 . . . Brownish purple.

These experiments may be varied by ex-
ploding the wires, when stretched parallel to,
and at about an eighth of an inch distant from
the surface of a sheet of paper or glass ; in
either case a very beautiful figure is impressed,
and on glass, a part of the metal in an unoxi-
dated state appears immediately under the wire;
whilst the oxidated portion produces a figure of
some width by which it is encompassed. The
colours of the oxides produced in this way, dif*
fer from those obtained in receivers, many co-
lours being in some instances obtained from
one metal.

The charges employed by Mr. Cuthbertson
are rather high, and consequently attended
^ith great risk of fracture to the jars of the

186

OXIDATION OF METALS.

battery ; 1 have used in my experiments finer
wires, and of shorter length, with a moderate
charge. The proportions are indicated accord-
ing to the preceding rule,, in the following
tfible. . .

, The length of wire exploded in each experir
ment is five inches. x .

Colours of the figures on paper.

Gold wire

l-g-BT

.00

Purple 2lnd brown.

Silver wire

• •

Grey, brown, and green.

Platina wire

Grey and light brown.

Copper wire

Green, yellow, & brown.

Iron wire

Light brown.

Tin wire

Yellow and grey.

Zinc wire

I
TT15-

Dark brown.

Lead wire

Tins'

Brown and blue grey.

Brass wire

Purple and brown.

Brass wire is sometimes decomposed by the
charge, the copper and zinc of which it is
formed being separated from each other, and
appearing in their distinct metallic colours when
the explosion is made over a strip of glass.
The figures of all the metallic oxides are usually
more beautiful when impressed on glass^ than
paper, but their colours are less permanent.

OXIDATION AND REVIVAL OF METALS. 187

The oxides produced by electrical discharges
appear to consist of several distinct portions, of
different degrees of fineness; when a wire is
exploded in a receiver, part of the oxide imme-
diately falls to the bottom; but another portion
remains suspended in the air for a considerable
time, and is at length gradually deposited. It
is probable this circumstance may partly occa-
sion the different colour of oxides produced in
close receivers and in the open atmosphere, for
in this last a portion of the oxide is always
lost.

The chemical agency of electricity is the
more remarkable, since it tends equally to pro-
mote combination, or decomposition. Metallic
oxides already formed, may be restored to the
metallic state by its means ; and for this pur-
pose a very simple arrangement will suffice.

Experiment 78. Introduce some oxide of
tin into a glass tube, so that when the tube is
laid horizontal the oxide may cover about half
an inch of its lower internal surface. Place the
tube on the table of the univei:sial discharger,
and introduce the pointed Avires into its oppo-
site ends, that the portion of oxide may lay be-
tween them. Pass several strong charges in

188 DECOMPOSITION OF WATEH.

succession through the tulie, replacing the oxide
in its situation, should it be dispersed. If the
charges are sufficiently powerful, a part of the
tube will, soon be stained with metallic tin,
which has been revived by the action of the
transmitted electricity. '

; Other metallic oxides may be revived in the
same \vay ; or if vermilion be employed, which
consists of sulphur and mercury, the mercury
will be separated, and that with such facility^
that the charge of a very moderate.sized. jar is
fully sufficient. *

When the electric spark is taken in various
fluids, they are decomposed by it. Water is
converted into two gases, oxygen and hydro-
gen ; in the proportion of two measures of the
latter to one of the former ; and when a suffi-
cient quantity of these are liberated, if an elec-
tric spark be sent through them, they inflame
and disappear, water being reproduced.

This experiment was first made by a society
of Dutch chemists, assisted by Mr. Cuthbert-
son ; it is a very laborious and tedious one,* but
has been much facilitated by an. arrangement of

*. See Dr. Pearson's paper in Nicholson's JouJ-nal, 4to. vbl.f.
p. 241> &c. or Phil. Trans, vol. kxxvii. p. 142.

DECOMPOSITION OF WATBR. 18^

Dr. Wollaston's.t Two very fine wires of gold
or platina are inserted in capillary tubes ; one
extremity of each wire is previously pointed as
fine as possible, and being introduced within
the capillary tube to a short distance from its
end, the glass is softened by heat until it ad-
heres to the ' point and covers it : the glass is
then gradually ground away until the point of
the gold wire is perceptible through a lens.
Two wires so prepared are introduced into a
vessel of -water, so that the points may be neai*
each other, and' form an interrupted metallic
circuit: one of the wires is to be connected
with: the ground, or with the negative conduc-
tor of. the machine; and the other with an in-
sulated ball placed at a short distance from the.
positive conductor. When a current of sparks
are passed in this way, a series of minute bub-
bles Jof^ gas rise from the points of the gold
wires, .;wliich may bjp' collected in a small in-
verteid receiver placed over the ends of the
wires, .and will explode on the application of. a
lighted taperj or by paissing ah electric spark
through; it: but it is to be observed,\that a con-
siderable: thne is required to produce a sufficient

t PhiI..TrSnj. toI. xci. p. 42/; '

190 DBC0HP08ITI0N OF tlTATER*

quantity for this purpose. Dr. Wollaston found
that the rapidity of the decomposition was in
proportion to the limited size of the point ex*
posed ; a point ^i^ of an inch diameter effected
the decomposition, when the spark from the con*
ductor to the insulated ball was l-8th of an inch
long ; and a point t-jV^t of an inch diameter, pro-
duced the same effect with sparks -^ of an inch
in length. These coated wires are necessary for
the decomposition of all conducting fluids ; as
they confine the action of the electricity to a
single point, and prevent the diminution of in-
tensity that would otherwise ensue.

With less perfect conductors, as oils, alco*
hoi, and ether, this precaution is unnecessary ;
they may be decomposed in the apparatus, Fig.
27; sparks being passed from the platina wire
to the bottom of the metal dish without any
risk of fracturing the tube, and the gaseous
product rising into the tube, which serves as a
receiver. The gases procured from inflammable
fluids are chiefly what are called hydro-car*
bonates, and consist of hydrogen, holding in
solution various proportions of charcoal. When
concentrated acids are decomposed, the gaseous
product is usually oxygen gas.

COMBINATION OF GASES* t9l

Dr. Wollaston transmitted a current of elec-»
tricity, by means of two fine gold points, along
the surface of a moistened card tinged with
litmus; after a few turns of the machine a red^
ness was perceptible about the positive wire.
The negative wire being afterwards placed on
this blue spot, soon restored it to its original blue
colour. It therefore appears that the effect of
an acid is by some means produced at the posi*
tive wire, and that this effect is counteracted
by reversing its electricity.

The same philosopher inserted two silver
wires (coated with sealing-wax, so that their
ends only Were exposed) into a solution of
copper: ou transmitting a current of electricity
from one wire to the other, the receiving or
negative wire became coated with copper ; and
the copper coating was removed when the elec*
tricity of the wire was reversed.

The facility with which the electrical spark
can be taken in air-tight vessels, renders its ap^
plication to chemical purposes an object of the
first importance ; and in no instance is its action
more extensive than in its application to the
combination or decomposition of various gases.
The formation of water is shewn by filling the

193 COVBINATION OP CABES:

tube, Figure £4, with quicksilver, and inverting
it in a vessel of the same ; a mixture of hydro-
gen and oxygen gases, in the proper propor-
tions/ are then to be passed up into the tube,
until they occupy about an inch of its. upper
part. A spark being now passed between the
wires, the gases will inflame, and the quicksilver
will rise to the top of the tube covered with a
thin film of water, which has resulted from the
coAibustion of the gases. For all experiments
of this kind the glass vessels should be. at least
half an inch thick, that they may resist the ex-
pansion produced in the gases by the explosion.
A perceptible quantity of water may he
formed in this manner by employing a stout
globe, with a stop-cock ; a wire passing through
its centre to within a short distance of the. cap
to which the stop-cock is screwed. The globe
is to be exhausted by means of an air-pump, and:
then screwed on a receiver containing a mixture
of oxygen and hydrogen gases, and furnished
with a stop-cock. — See Figure 30. The cocks
being opened, the globe will be iplled with the
gases ; they are then to be shut, and a spark
passed from the wire in the inside of the globe
to the cap. A bright flash ensues, and the

COMBINATION OF aAM:a. 196

inside of the globe becomes coated withmoisf-
ture; the cocks are then to.be op^ned^ and
more gas will rush into the globe. -The cocks
being again closed, a second explosiQn may be
made, which will increase the dew on the inside
of the globe ; and the experiment may be rCf
peated in this way until drops of water are per«
'ceived.*

Eaperiment 79»: Take a stout glass tube

<;losed at one end, and having two wires passed
through its sides so as to admit of a spark
being taken within the tube. Adapt a cork
to the open end of the tube, and, holding it
inverted, pass into it a mixture of hydrogcQ
and oxygen, pr of hydrogen and atmospheric
air. Close the tube with its cork, and pass^
spdrk through it; a loud explosion will follow,
and the cork will be expelled with violence^
An apparatus is sometimes fitted up for this pur-
pose as an amusive experiment; it is called the
inflammable air pistol.

The facility with which inflammable air is
lighted by even a moderate electric spark, in*
duced professor Volta to contrive his inflamma*

* This 6q)enment was fint made by Mr. Cavendishi in the
jear 1781.

194

EIECTRO-CHEMtSTHT.

ble air-lamp ; (for a modification of which, a1
patent was some time since obtained as a sourd
of instantaneous light.) It consists of a reser-
voir filled with hydrogen gas, subject to tbc^a
constant pressure of a column of water, an^lj
confined by a stop-cock, wliich, when opencdl'
permits it to escape in a slender stream from *
small aperture. In a box beneath the vessel of
gas an electrophorus is placed, and a wire passes
through a glass tube from the upper part of this'
box to the opening of the stop-cock. The co-
ver of the electrophorus is connected by a sillt*
string with the handle of the stop-cock; so*
that the same motion that opens the cock, raisesl
the cover of the electrophorus, and the sparlt
that strikes from it, is conveyed by the insiW
lated wire to the stream of gas, which :
flames. This eflrect takes place every time the!
stop-cock is opened, for the electrophorus will
produce sparks for a considerable time, without*
any new excitation; and the quantity of gal*
consumed at each repetition of the process iarf
inconsiderable, so that a light may be procured*
ftbdve a hundred times before the contents of'
the reservoir is expended ; and it may then be
easily replenished.

lORXATION OK NITBIC ACIB. l^

Dr. Priestley observed, that when electrical
sparks were taken for a considerable time in a
confined portion-of common air, the bulk of the
air >was diminished; -and on introducing any
blue vegetable liquor into the vessel iij which
the experim^t had been mad^ a redness re^
suited, evincing the presence of an acid.^ Mt*
Cavendish' repeated this experiment with great
precision, and proved that the elements of afr-
mospheric air (oxygen » and nitrogen^) were
by t;his means combined in a^ different propor**
tioui and formed nitric acid.^ The air on
which the experiment was made, was confined
between two columns of quicksilver jn the anr
gular part of a bent tube^ first filled with quick-
silver> and then inverted with its legs in two
sepaiate. glasses of the- same fluid; (see figure
31 ;) the ^ir being introduced into the tube af^
ter its invasion, so as ta occupy the upper part
erf tjie angle for the length of an inch, or an
inch and.a half. The quicksilver in one of the
glasses was then connected either with the ne^
gative conductor or the ground, and that in th^
other with an insulated ball placed near the po-

* Pbil. Trans, vxil. It^ar. p. 372^ and vol. UxTiii. p. 261.

o 2

IS6 FOSlf ATION OF NlTttlC ACID*

•itive conductor^ and in this way a current of
sparks was passed through the confined portion
of air ; and as the bulk of this diminished^ fresh
portions were passed up into the tube ; so that
the length of the column was preserved nearly
equal. The experiment was rarely completed
in less . than a fortnight or three weeks, the ma-
chine being M'orked for half an hour leach jdajr;
The internal diameter of the tube should be
aboil^t on^*tenth of an inch : insteaid of the form
above described^ it may be straight, with a pla-
tina wire sealed into one end, and its open ex*
tremity immersed in a basin of quicksilver.
(Figure 32.)

Mr. Cs^vendish found that the experiment
succeeded best when instead of common air
alone, a mixture of five parts of oxygen and
three parts of common air were employed : such
a mixture disappears almost entirely; and if a
small quantity of soap Ices, or solution of pot^
ash, be passed up into the tube, the process is
accelerated, and the solution becomes nitrate
of potash, or saltpetre.

This experiment was twice repeated on an
extensive scale by Mr. Gilpin, under the direc-
tion of Mr. Cavendish and other members of

ELECTBO-CHBM ISTRT. 197

the Royal Society. There was some* slight dif?
ference in the proportions of the gases absorbed,
but . from the mean result of the experiments,
it' appears that seven measures of oxygen unite
to three . measures nearly of nitrogen, to. form
nitric acid.

.. The experiments that may be made on. the
combination and decomposition of various gases
are very numerous ; to describe them in detail
would be useless to those who are not acquaint-
ed with the leading facts of chemistry ; and the
object of the chemical student will be as effec-
tually accomplished by a tabular enumeration
of the gases that are Jtffected by electricity, and
the results they aflFord. The gases are usually
exposed to the action of electricity in a closed
tube, with two wires passing through its sides
near the closed end : the tube is filled with mer-

• • • ... I

cury, and inverted in a vessel of the same; and
the gas being then introduced until it presses
the mercury below the wires, sparks are passed
between them until the required change is pro-
duced ; with mixtures of inflammable gases and
oxygen the first spark usually produces the
changei but with other mixtures it is sometimes

198 BLECTBO-CHEMISTRT.

necessary to continue the current of sparKfc fat
hours. . . ; *

When figures are prefixed to the gas,. or: its
result, as stated in the following table, ^dsejr in*
dicate the proportional measures employed or
produced; they are introduced principally in
cases where the use d different proportions oc-
tasiodis a variation of result '

Mixed Gases. Result.

Atdabs^eric air and h/droged . . Watet and nitrogen.

&%jgBa and hydrogen Watec

Chknino and hjrdrogen •,..... Muriatic aoid«

l^ln^tic acid and oxyigen , Chlorinj^.

Carbonic oxide and oxygen .... Carbonic acid.

Nitrogen and oxygen Nitric acid.

Sulphurous acid and oxygen .... Sulphuric acid.

Phosphtiretted hydrogct, ^"dl^^^ ^^^ j^ j^^^^^^;^
oxygen ., J *^ *^

Sulphuretted hydrogen and 7 ^^^^^ ^^^ ^^^ j^^^^ ^^.^
oxygen j ^

Oxygen and ammonia , , Water and nitrogen.*

100 defiant ga$ and tS4 oxygen Carbonic acid and water.

) 00 olefiant gas and 100 oxygen Carbonic oxide and hydrogen.

^ If there be^ an excess of oxygeny nitric acid is also a
product.

ELECTHO-CHEMISTRV. IfljJ

Compound Casts. Result. ,

Muriatic acid Hydrogen.*'

Fluoric acid Hydrogen.*

Nitrous gas Nitric acid and nitrogeD,

Carbonic acid Carbonic oxide and oxygen.

Siiipburetted hydrogen Sulphur and hydrogen.

Phoiphuretted hydrogen Phosphorus and hydrc^en.

Ammonia Hydrogen and nitrogen.

defiant gas Charcoal and hydrogen.

Carburetted hydrogen Charcoal and hydrogen.

And, from analogy, it is probable that all com-
pounds of Hydrogen with inflammable matter
are equally susceptible of electrical decompo-
• sition.

These various effects, produced by the same
agency, do not appear susceptible of any other
explanation than that which assumes the action
of electricity to be mechanical; and even on
this assumption they are not strictly intelligible.
The momentary agitation into which the various
mediums are thrown by the action of the spark,
might be considered as likely to promote a new
arrangement of parts ; but, admitting this, why
is the change instantaneous in some instances,
and gradual in others? and by what inversion
of principle is the same impulse that unites the

* On the authority of Dr. Henry and Mr. Dalton.

100 SLBCTKO-CHBMISTETa

particles of bodies, enabled subsequently to

•.- * ■ ^

separate them? These are ' questions it would
be interesting to resolve ; but there appears no
clue by. which such intricate processes can be
at present analysed. The chemist must there^
fore be content to avail himself of the practical
advantages they afford to his art, and await the
progress of discovery for the development of
their theoretical relations.

The luminous phenomena of electricity suf-
ficiently prove the influence of the electric fluid
on light, and this fact is remarkably confirmed
by its agency in the production of phosphoric
appearances in various bodies when it passes
luminously over their surface. Experiments x>f
this kind were first made by Mr. Lane and Mr.
Canton;* and have been since extended by
Wilson, Morgan, and Skrimshire-f

Ejcperiment 80. Place a piece of dry chalk
on the table of the universal discharger, and
adjust the wires on its surface, with their ends
at two inches distant from each other. Pass a
strong charge from wire to wire, and after the

* Priestley's History of Electricity, p. 312.

f Nicholson's Journal, vol. xv, p. 281 j vol, xvi. p. 101 ;
vol. xU. p. 153.

PHOSPHORTC EFFECTS Of ELECTKlClTy. 201

explosion a streak of light will be evident in
the track ot the discharge, exhibiting the pris-
4natic colours : it will continue for some seconds,
' Similar effects ensue when the charge is
passed over the surface of various other bodies;
l»ut the colour and the duration of the light
■vary considerably; and if the charge is passed
through the substance of some of them, they
will be dispersed in luminous particles that re-
tain their light for a considerable time. The
following table contains an enumeration of
several substances that may be thus rendered
phosphorescent, and displays the results they
produce.

Katlve sulpliatc of baryies Bright green light,

Native carbonaieof barytea. . . Ditto, less brilliant.*

Acelaie of potash (dry) Brilliant green light.

Succinic acid Ditto, and more durabl*

Loaf sugar Dltta.

Specular gjptium, or seleniie. . Ditto, but transient.

Calcined oyster shells Prismatic colours.

Bitto calcined with sulphur, . . Durable and bright light.

Rock crystal Light first, red, and ihen while.

^Quartz Dull white light.

fiorax Faint green light.

Boracic acid Bright green light.

* These results are taken from experimema made with the
specimtns I thauced to possess.

£03 PHO8P0O11IG ZFFECTf

The bodies here enumerated form but a very
small {>roportion of those that become pl|o»-
phoric. by the dis^^harge, but they fure such 9$
possess that, property in the most remarkable
degree. For a systematic examination of a very
e^ttensive series of substances the reader is re-
ferred to Mr. Skrimshire's. papers in Nicholson's
Journal.

Equally remarkable with this property of
exciting phosphoric phenomena, is the effect
of an electric explosion on : various opaque
bodies : it was first observed by Dr. Priestley^
and may be thus exhibited : —

Experiment 8 1 . Let two wires be fitted into a
groove on the surface of a piece of smooth maho-
gany, so that, by sliding tlie wires backwards or
forwards, their ends may be placed at any required
distance from each other. Wheii they are about
half an inch apart, place a thumb or finger over
the interval, and pass a charge from wire to wire;
the thumb will appear perfectly transparent dur-
. ing the passage of the spark beneath it, but no
unpleasant sensation will be felt.

Experiment 82. Substitute a jar of water,
or any coloured fluid, in the place of the thumb:

: or ELECTRICITT, BOS

'When, the discharge is mad^ the fluid will be dis«
itiictly.and curiously ilhiminated.

Esperimmt 83. Place the ends of the wires
at Uie distance of three-fourths of an inch ; and
ovier the inter vaV lay a thick piece of pipe-x:lay
Dr of pumice-stone : when the charge passes,
•these opaque substances will S4)pear perfectly
•transparent.

. ; . EjXperiment 84. Arrange five or six eggs in
a straight line, and in contact with each other:
pass a stn^U shock through them, and they will
Mcem perfectly luminous.

Experiment 85. Insert two wires, so as to
tcome within a short distance of each other, in
« small melon, an orange, or apple : pass a shock
.through the wires, and the fruit will appear
transparent.

These experiments are susceptible of con-
*siderable variety, since every substance that is
'not a good conductor, becomes more or les^
luminous by the passage of the charge r but no
correspondence has been yet observed between
-the existence of this property and the chemical
characters of the substances in which it obtains.

It may be, proper here to mention, that for
-experiments on electric lights and thejexcitation

204 MAGN£TTSM BY ELECTRICITY.

of phophorescehce, it is absolutely necessary to
operate in a dark room ; for the presence of -the
least extraneous light will prevent the obser-
vation of such phenomena.

In addition to the mechanical. and chemical
agencies of electricity already described; it has
been observed to have some relation to the phe-
nomena of magnetism. The needle of the or-
dinary ship compass has been often noticed to
vary during a thunder storm, and in some ^in-
stances its poles have been reversed. Dr. Frank-
lin passed the charge. of some large eleptrical
jars through fine steel needles ; their ends were
blued, and magnetic polarity communicated to
them. The effect depends principally on the
situation, of the needles when they are struck,
and is little affected by the manner in which
the charge is passed through them ; the com-
municated magnetism is strongest when the
needle is struck, whilst it lies in a direction
from north to south; and weakest when it
points from east to west.

Experiments of this kind are most effectu-
ally made with needles of steel wire, the fortieth
or fiftieth of an inch diameter, and three or
ibur inches long, with a small dent in the mid-

1IA.OXETXSM BYE LECTRICITY- 205 :

die by which they may be supported' on a point:
the ch^ge of a battery should be passed through
them.

E.iperiment 86. Place a feteel wire of the
preceeding description in the direction from
north to south, and pass a moderately strong
charge of a battery through it ; it wnll become
ms^neticy the end that lay southward being the
9outh pole.

. JEdperiment 87. Render a steel wire slightly
magneticy and place it in the magnetic meri-*
dtaiii with its south pole towards the north. A
strong charge of a battery will either destroy
its magnetism, or reverse its magnetic poles ;
if its magnetism is merely destroyed, a second
charge will magnetize it anew, but with re-
versed poles*

Experiment 88. Place a steel wire in a per-
pendicular direction, and pass a strong charge
through it ; it will become magnetic, the upper
end being the south pole. If this end be now
placed downwards, the transmission of another
charge will destroy its magnetism, or reverse
its poles.

A strong charge passed through a natural
magi;iet destroys its power.

206 HAONETISM BY ILECTRICITT*

These phenomena convey no mforniation'
relative to the nature of the electric flaid ; nor
can they justly be considered as displaying any
analogy between it and the cause of magnetism;
for that power is also excited. and modified by
mechanical action, and by the agency of heat;
and it is probable that in this particular in-'
stance, the three influential causes operate near*'
ly on the same principle : but until the nature
of magnetism is more clearly developed^ it is
useless to speculate on the probable action of
other powers in exciting or modifying its phc**
noanena.

907

PART III.

NATUliAt AGENCIES OF RLECTaiCITT.

CHAP. L

On the Identity of Electricity, and the Cause rf

Lightning.

JLluRtNG the consideration of the nature and
peculiarities of electrical action, the principal
stimulus to inquiry must arise from the novelty
and singularity of the appearances observed,
and some difficulty may be experienced in fix-
ing the attention on a series of facts apparent-
ly insulated and unconnected with the usual
sources of human interest : but in the experi-
mental sciences these preliminary steps are al-
ways necessary, and may be considered analo-
gous; to that collection and preparation of rude
niaterial$ which is the essential precursor of
every useful and valuable production of art.

208 IDENTITY or J^LECTfilClTT.

The utility of electrical science is most evi-
dent in its application to tlie phenomena of
nature; and more remarkably so, when the
vague hypotheses and conjectures that were
previously applied are compared with our pre-
sent conception of the subjects it has ex-
plained.

The philosophy of the ancients appears to
have been remarkably defective in its applica-
tion to the phenomena of the atmosphere; many
of the most interesting effects were entirely un-
observed, and the production of its luminous
phenomena was described by their best natu-
ralists as. amongst ^' the awful mysteries of Na-
ture;" whilst the phenomena themselves were
invested by their poets with the character of
instruments of punishment and revenge in the
hands of their deities.

In modern times, before the discoveries in
electricity, these phenomena were referred to
the inflammation of subtle effluvia or sulphureous
exhalations in the higher regions of the atmo-
sphere, or to the contending percussions of one
cloud against another ! In this way is the place
' of true knowledge supplied for ages by dreams
and fables; so disposed is the human mind to

AND THE CAUSE OF THUKDER. S09

create imaginary causes, when those that really
operate are beyond our comprehension.

In tlie infancy of this science, Mr. Grey,
(who had increased the effects of electrical ex-
citation by the application of his discovery of
conductors and non-conductors to the improve^
ment of the apparatus,) was led, by considering^
the appearance of electricity, when passing from
one conductor to another, to notice a faint si*
milarity between the snap and light of the sparky
and the phenomena of thunder and lightning.
His remark does not iappear to have attracted
the attention of electricians, until, in 1748, the
Abbe NoUet published, in the fourth volume of
his >* Lemons de Physique,"- the following ex-
tension of this conjecture: ^* If any one should
take upon him to prove, from a well-connected
eomparison of phenomena, that thunder is in
the hands of nature, what electricity is in ours,
that the wonders we now exhibit at pleasure,
are little imitations of those great effects which
frighten us; and that the whole depends on the
same mechanifim c if it is to be shewn, that a
eloud prepared by the action of the winds, by
heat, by a mixture of exhalations, &c. is when
opposite to a terrestrial object^ that which an

£10 TH£ CAU8B OF THUITDEE^

electrified body ia, when at a certam diataace
from one that is not electrified ; I confess this
idea, if it was well supported, would afford me
much pleasure; and to support it, how^maoy
specious reasons present themselves to a mau
well versed in electricity. The universality of
the electric matter, the rapidity of its action,
its inflammability, and its activity in inflaming
other bodies; its property of striking bodies
externally and internally, even to their smallest
parts, the remarkable example we. have of this
effect in the Ley den experiment,, the idea we
may legitimately form in supposing a greater
degree of electric power, &c. All these points
of analogy, which I have for some time raedi*
tated, begin to make me believe that one might,
by taking electricity for a model, form to one's
self, in relation to thunder and lightning, more
perfect and probable ideas than any that have
been offered hitherto." *

This remarkable observation reflects, consi-
derable credit ou the Abb6 NoUet for his pene-
tration and sagacity ; but it bears no compari*
son with the acute conception, sound p^iloso*
<. ....

* Legops de Physique Expenmentale^ torn. iv. p. 314.

Tiife CAUSfe tit THUNDlERv fill

}>liical argument, and satisfactory experiments^
by which Dr. Franklin has demonstrated th6
identity of the electric fluid, and the cause of
thtti&kler. This excellent philosopher made very
lYum^Fous original Observations on the pheno*
mena of electricity^ which were communicated
in a Series of Letters to a member of the Royal
Society, from the year 1747 to 1753. In these,
amongst an unexampled variety of electrical dis-
coveries, he first detailed an hypothesis to ex-
plain the phenomena of thtirider storms by the
Ictiown properties of electricity^ and afterwards
ddteonstrated the truth of his supposition by
thcmost extraordinary experiment ever made.
Dr. Frankliif had observed with equal attention
the peculiarities of the natural phenomenon,
^Itkd the porwer to which he ascribed its produc-
tion; h^ enumerated the following, as their
leading features of resemblance-

1st. The zigzag form of lightning corre-
sponds exactly in appearance with a powerful
electric spark that passes through a considerable
interval of air.

- 9d, Lightning most frequently strikes such
bodies as are high and prominent, as the sum-
ihits^ of hills, \the masts of ships, high trees,

SIS THE CAUS£ OF THUNDEIU

towers, spires, &c. The electric fluid, when
striking from one body to another, always
passes through the most prominent parts.

Sd« Lightning is observed to strike most
frequently into those substances that are good
conductors of electricity, such as metals^ water,
and moist substances ; and to avoid those that
are nonconductors.

4th. Lightning inflames combustible bodies.
The:Same is effected by electricity.

5th. Metals are melted by a powerful charge
of electricity. This phenomenon is one of the
most common effects of a stroke of lightning.

6th. The same may be observed of the frac-
ture of brittle bodies, and of other expansive
effects common to both causes.

7th. Lightning has been known to strike
people blind. Dr. Franklin found, that the
same effect is produced on animals when they
are subjected to a strong electric charge. .

Uth. Lightning destroys animal life. Dr.
Franklin killed turkies of about ten pounds
weight, by a powerful electric shock.

9th. The magnetic needle is affected in the
same manner by lightning and by electricity,
and iron may be rendered magnetic by both
causes.

franklin's experiments. 2 is

The phenomena are therefore strictly ana-
logous, and differ only in degree; but if an
electrified gun-barrel will give a spark, and pro-
duce a loud report at two inches distance, what
effect may not be expected from perhaps 10,000
acres of electrified cloud ? And is not the diffe-
rent extent of these conductors, equal to the
different limit of their effects ?

But, to ascertain the accuracy of these ideas,
let us have recourse to experiment. Pointed
bodies receive and transmit electricity with fa-
cility ; let therefore a pointed metal rod be ele-
vated in the atmosphere, and insulated; if
lightning is caused by the electricity of the
clouds, such an insulated rod M^ill be electrified
whenever a cloud passes over it, and this elec-
tricity may then be compared with that ob-
tained in our experiments.

Such were the suggestions of this admirable
philosopher : they soon excited the attention of
jthe electricians of Europe, and having attracted
the notice of the King of- France, the approba-
tion he expressed excited in several members
of the French Academy* a desire to perform

* Messrs, Dalibard> De Lor,.Ma2eas> BiifrQnj.and Monpier*

fil4 franklin's EXPERXMENTi,

.the experiment proposed by Franklin, ai:^^ sever
ral insulated and pointed metallic rods wer^
4Brected for that purpose. On the 10th of May
175£, oqe of jhese, a bar of iron 40 feet high,
^situated in a garden at Marly, I^ecame electrifie4
during the passage of a stormy cloud over it;
and during a quarter of an hour it afforded
sparks, by which phials wpre charged, and othiSF
electrical experiments performed. During thp
passage of the cloud a loud clap of thunder was
heard, so that the identity of these phenomena
was thus completely proved. Similar experir
nient3 were afterwards made \)y M.deLor, Buf-
fon, and Monnier, iu France, and by Dr. Watr
son, Mr. Canton, Mr. Wilson, and Dr. Bevis in
England.

Dr. Franklin had not heard of thps^ experi-
ments, and was waiting the erection of a spire
at Philadelphia to admit an opportunity of suf-
ficient elevation for his insulated rod, when it
occurred to him that a kite would obtain mora
ready access to the regions of thundpr than any
iplevated building. He accordingly adjusted a
silk . handkerchief to two light strips of cedap
placed crosswise; ai^d having thus formed a
kite, with a. tail and loop, at thp approach of

franklin's EXPERIHENT8. fil^

ifhe first storm he repaired to a field accompanied
by his son.

Having launched his kite with a pointed
•wire fixed to it, he waited its elevation to a
proper height, and then fastened a key to the
end of the hempen cord, and attached this by
means of a silk lace (which served to insulate
the whole apparatus) to a post. The first signs
of electricity which he perceived was the sepa-
ration of the loose fibres of the hempen cord :
•a dense cloud passed over the apparatus, and
-some rain falling the string of the kite became
-wet; the electricity was then collected by it
more copiously, and a knuckle being presented
to the key, a stream of acute and brilliant sparks
was obtained. With these sparks spirits were
fired, phials charged, and the usual electrical
experiments performed : and thus was this im-
portant discovery, which its author had modestly
called an hypothesis, established as a scientific
truth.

Dr. Franklin afterwards constructed an ap-
paratus for perpetual observations; it consisted

of an insulated rod placed on the top of his

house,. and connected with two bells and a pen-
dulum, which were so arranged as to ring when

216 ELECTJllCITT OF THE ATlIOSVUBfti:.

electrified, and thus gave notice of the appFoacls
of a charged cloud.

These experiments were repeated in almost
every civilized country, and with various suc-
cess : in France a most formidable result was
obtained by M« de Romas ; he had constructed
a kite of seven feet in height and three feet wide^
which was raised to the height of 550 feet,. by
a string having a wire interwoven through its
whole length to retider it a better conductor:
from the string of this kite, on the f^6th of Au-
gust i7*'>6, sparks, or rather streams, of light*
ning were darted to the earth, of an inch in dia-
meter and ten feet long, whilst the preliminary
phenomena were equally terrific*

It would have been surprising had such ex-
periments been constantly conducted with secu-
rity : in the management of the ordinary elec-
trical apparatus shocks are often received inad-
vertently, and the first experimenters on atmo-
spherical electricity were often severely shaken.
It is indeed rather fortunate that, amidst the
thousands of experiments of this hazardous
nature that have been made since the first dis-

* Memoires des SaTansEtraogers^ torn. ii. p. Sgs^ & torn. ir«

DEATH OF PROFESSOR RICRUAV. £17

ooTeryi but one fatal catastrophe has occurred,
and that happened at so early a period as to pre-
clude the chance of proper precaution having
been employed^ The individual, who will be
immortalized as the victim of electrical science,
was Professor Richman of Petersburgh. He had
constructed an apparatus for observations on
atmospherical electricity, which was entirely
insulated, and had no contrivance for discharg-
ing it when electrified too strongly. On the
6th of August 1753, he was examining the elec-
tricity of this apparatus, in company with a
friend: whilst attending to an experiment his
head accidentally approached the insulated rod,
and a flash of lightning immediately passed
from it, through his body, and deprived him of
life. A red spot was produced on his forehead,
his shoe was burst open, and part of his waist-
coat singed; his companion was benumbed, and
rendered senseless for some time; the door-case
of the room was split, and the door torn off its
hinges. *

This accident demonstrated the necessity
of the gieatest caution in such experiments;

* Phil. Trans, vol xhiii. p» 765 5 or Priestley's Historj,
p. 358.

1218 . CONDUCTORS FOB BiriLDINGI*

and they are now usually rendered secure by
•placing a metal rod, connected with the ground
or tlie nearest water, at a small distance from
the end of the insulated rod ; with this arrange-
ment, when the electricity becomes too power-
ful, it passes the interval between the rods, and
is conducted safely to the ground.

These experiments sufficiently prove the
agency of the electric fluid in the production
of lightning and thunder. Dr. Franklin had
anticipated, as a consequence of the verification
of his conjecture, that the known properties of
electricity might be employed to provide some
security against the concomitant dangers of a
thunder storm ; for if the injury usually sustainr
ed arises from the discharge of a large quantity
of electric fluid, it may be prevented by provid-
ing a proper conducting channel for such dis-
charge. Metals conduct electricity better than
any other substances known, and when build-
ings or ships are struck by lightning the greatest
damage is usually effected between detached
pieces of metal, since the electric fluid, in pass-
ing through the intervals, produces the usual
expansive effect observed in every interrupted
metallic circuit. Hence Dr. Franklin proposed

.CpNPUe.TOHS FOB BUILDINGS, fil9

te erect a perfectly continuous metallic rod by
the side of any building intended to be secured
from the effects of lightning : the rod was to
bp poipted at each extremity, and extended
above the highest part of the building and ber
low its foundation, the lower extremity being
cQQnected with the nearest water or other con*
ducting matter. In this way a perfect metallic
circuit is provided, and through this any elec-
trical discharge would pass more readily than
through the detached or imperfect conductor*
Df which the building is composed. Experience
lias sufficiently demonstrated the utility of this
proposed method of defence, and it is now very
generally adopted in situations where the chance
pf injury from thunder storms is considerable.
Tliere are some experiments usually employed
to illustrate its application, and these it may be
proper to notice in this place.

Experiment %9. Construct a pyramid of se-
veral pieces of wood placed one on the other ;
let the lowest piece form the square base of the
pyramid, and the upper conical part rest upon
the base by three small brass balls. A square
hole is to be made in one side of the base, and
a piec^ of wood fitted loose]y in it ; upon this

JtSO C0XDUCT0B8 FOR BU1LDIN69.

loose piece of wood one of the brass balls is to
rest, so that the upper part of the pyramid can
only preserve its equilibrium, whilst this wood
is in its situation. Pieces of wire are let into
the several parts of the pyramid in such a man-
ner, that when it is put together the ends of
the wires may come in contact, and form a con-
tinuous conductor from the top to the bottom :
the part of this conductor which traverses the
loose piece of wood, may, by reversing that, be
removed from its continuity with the others,
and will consequently occasion an interruption
in the metallic circuit. If a charge is passed
through the conductor when this interruption
exists, the piece of wood will be thrown out, and
the pyramid will fall ; but if the piece of wood
is placed so as to render the conductor continu-
ous, the charge will be conducted without pro-
ducing any effect.

In the same way, a model of a powder mill
may be blown up, or a house be set on fire, by
making an interrupted circuit within them, and
placing gunpowder, or other combustible mat-
ter in its interval. These models are usually
furnished with a moveable conductor; when
this is affixed to them^ the charge of a large jar

• CONDUCTOU6 FOR BUILDINGS* S21

or battery will produce no effect; but when
the conductor is removed, and the charge passes
through the interrupted circuit, the combusti*
bles are inflamed, and devastation ensues. Ap*
paratus properly fitted up for these demonstrar
tions are sold by the philosophical instrument
makers.

Experiment 90. To exemplify the method
of defending ships, a small model may be fitted
up, with a glass tube for the mast, to which aH
tlie rigging should be attached : the tube is to
have two wires inserted through its opposite
ends, until within half an inch of each other ;
it is then to be filled up with water and the
ends stopped. The lower wire is to be con-
nected with a small metal thread tied to the
stern ; the upper wire is to be surmounted by a
small ball, which may serve as the top of the
mast, A moveable conductor may be formed of
a thin copper wire placed parallel with the mast,
rising above it, and connected at bottom with
the metal thread If a powerful charge is passed
along the mast whilst the conductor is attached
tty it, no effect is produced^ but if the conduc-
tor is removed, the charge passes through the
"^body of the mast, and shatters it to pieces.

J2i UtitfTT OF POIKTED CON^UCfOR*.

If the conductors employed in these expert-*
tnents are pointed at the extremity, it wiH be
found difficult to make the charge pass with an
explosion, and it wiH in general be transmitted
either silently or with considerably diminished
force. It was on this principle that Dr. Frank-
lin recommended that the ends of the conduo*
iors, etected to preserve buildings from ^ the
effects of lightning, should be acutely pointed;
for a point will always reduce the intensity of
any electrified surface to which it is presented,
and will act upon its electricity at a consider-
able distance : a pointed conductor must conse-*
qucntly tend to weaken the charge of any cloud
that may approach it, before it comes near
enough to explode; and if the approach of the
cloud be gradual, its charge will be even en-
tirely dissipated without explosion. These factsr
may be readily exemplified by experiment.

Experiment 91' Suspend a number of downy
feathers, or an expanded lock of cotton frpm
the conductor of an electrical machine^ so aa to
represent a cloud. When the machine is tum^;
the fibres will expand and separate from eac||^
other ; and if a large ball or a flat surface be
presented, they will extend themselves towards

ITTILIXT OF POINTED CONDUCTORS, £S3

it : bat if the ball be removed, and a pointed
wire be presented at the same distance, the di<»
vergence will diminish, and the fibres will col-*
lapse and shrink up from the point.

Experiment S^. Charge a very large jar ;
touch the outer coating with oiie hand, and
bring a sh,arp needle held in the other, very
gradually toward the charging wire; the jat
will be - entirely discharged without explosion.
Repeat theexperiment, approximating the nee-
dle more rapidly. A very inconsiderable explo-
sion Avill be produced.

If the point used in these experiments be
not connected with the ground or the outside
of the jar, by a perfectly continuous conductor,-
it will not produce a silent discharge, but will
receive .an explosion like a ball. Hence the
necessity, that conducting rods be perfectly
continuous, and well connected with some con-
siderable mass of conducting matter, ^s water,
water pipes, or a moist stratum of earth.

At one time there was a ridiculous dispute
amongst electricians concerning the propriety
o£ pointed terminations to conductors, and it-
was proposed by some to place a. ball of mode-'
rate, i^izeon .them, -to prevent their action aa

224 B£ST FOBM OF A CONDUCTOR.

points. Independent of the weakness of the
arguments employed to shew that on some oc-
casions a blunted conductor might be prefer-
able to a pointed one, the size of the balls pro-
posed was such, that when opposed to a thuu-
der-cloud, or even to a powerful electrical
machine, they would have virtually acted as
points !

There are two instances on record, of houses
in this country having been struck by light-
ningi so as to sustain some damage, altliough
they were furnished with pointed conductors.
The conductors attached to these buildings
were not constructed in the most perfect man-
ner, and had they been so, the occurrence of
two failures in so many years, and amongst the
thousands of conductors that have been erected,
is a circumstance scarcely to be urged as an ob-
jection.

This method of defence can scarcely fail to
be effectual^ if employed with an attention to
the following circumstances. The conducting
rod, or rods, (for if the building is large there,
should be several,) should be formed of copper
or iron, three quarters of an inch thick. Its up-
per extremity should be acutely pointed, and

CONSTRUCTION OF CONDUCTORS. 225

rise three or four feet above the highest part of
dte building. The parts of which the rod is
formed should be joined closely, the ends that
are applied to each other being screwed toge-
ther. All the metallic parts of the roof should
be connected with the rod, and it should pass
down in as direct a line as possible, and pene-
trate several feet below the foundation, from
-which it should be inclined outwards. Tlie
.underground part of the conductor is better
.formed of copper, to prevent its decay; it should
,be connected, if it possibly can, with a moist
. stratum of earth, or with a large body of water.
The penetration of the conductor to some depth
below the level of the foundation, will in many
instances procure this advantage for it.

The conductor is sometimes made wholly of

• copper, it may then be thinner than if made

of iron; for a stationary conductor, I should

.conceive, that a copper rod of half an inch

thick, would answer every required purpose;

and there is little doubt that a less quantity of

^metal made into a hollow tube, so as to increase

. its superficies, would be equally, or even more

effectual.

Conductors for ships have been made of

226 CONSTHUCTION OF CONDUCTOR.

chains, (which are highly improper,) and of cop-
per M'ires, which are easily attached ; but they
are with equal ease detached ; and I have been
informed by several captains, that many ships
furnished with such conductors keep them in
an inactive state, packed up below, during long
and hazardous voyages. For this reason it
would be better that fixed conductors should be
employed; they might, I should conceive, bis
attached to the mast ; and where motion is re-
quired, an interruption might be made in the
inflexible conductor, and its parts be connected
together by a length of spiral wire, which woutd
be at once perfectly continuous, and sufficiently
flexible to yield to every necessary movement.
Although the various metals are affected
very differently by the same quantity of elec-
tricity discharged through them, yet they are
all proper for the construction of conductors,
provided they are employed of sufficient thick-
ness to resist fusion by a stroke of ligfatning :
for this reason the gutters, ridges, rain-watUr
pipes, and other external metallic parts of a
building, may form part of the conductor eni-
plo3^ed for its defence ; and it is a reprehensible
instance of wanton expenditure, when conduct-

CONSTRUCTION. OF CONDUCTORS. 227

' ing rods of thirty or forty ftct long are placed
by the side of a thick lead pipe of equal extent
In arrangements of this kind it is however ne- '
cessary to observe, that the perpendicular con-
ductor should pass in as direct a line as possible
from the top of the house to the bottom.

•The conductors for powder magazines aie
usually placed at a short distance from the
building ; when this method is adopted, .tl)e
conducting rods should rise eight or ten feet
above the highest part of the magazine, and
penetrate as much below itai foundation.

For the provision of perfect security from all
possible danger, it has been proposed by Mr.
Morgan to ^^ attach to the sides of the founda-
tion of each partition-wall, a strip of lead con-
nected with a similar strip that entirely sur-

> rounds the foundation of the building. A per-
pendicular strip, on each side of; the house,

• should rise from this bed of metallic conduc-

^tors; and being connected with wa^r-pipes,
&c.,,be continued to the roof, where the method
of guarding the bottom should be imitated. The

f top should be surrounded by a strip, whose con-
nexion must spread over every edge. and proijni-

228 covsTaucTiox of conductors. :

nence, and hence continue to the sumtnit eT
each separate chimney.'' *

The protection of the chimneys is of parti-
cular importance, for to these the discharge in
most frequently determined. It has been said,
that this circumstance arises from the conduct-
ing power of hot air ; but this cannot be true,
for no hot air issues from a chimney without a
fire, yet these are frequently struck. The true
cause is to be found in the superior conducting
power of the charcoal, or ^oot, with which all
chimneys that have been used are neces^rily
lined ; for over a surface of this kind an elec-
trical discharge will pass to a considerable dis-
tance.

The method of defence proposed by Mr.
Morgan may be objected to as considerably ex-
pensive ; for the strips of lead should be two
inches wide, and a fourth of an inch thick;
but he has justly observed, that if a proper use
be made of the leaden pipes and copings that
belong to most houses, and the common plum-
ber or blacksmith is employed to fix the con-
ducting strips, (which requires no other care

♦ Morgan's Lectures, vol. ii. p. 297.

CONSTRUCTION 01 CONDUCTORS. Sfi9.

than tbs^t they be aecure, and well connected
Ayith ea<;k other,) a considerable proportion of
this expense may be avoided. Hence, on the
whole, this method may not be objectionable,
where, from peculiarity of situation, a, building
is much ei^posed.

TbiP rods employed for conductors may be
listened to the wall by iron or copper staples,
considerably larger than the rod ; and the part
of it that passes through them, should be co-
vered with twq pr thrpe thicknesses of wooUei^
f^lotl) dipped in lipelted pitch ; this serves to in«
fuliite thfi rod more con^pletely from the build*

Independent of the protection required for
the mast of a ship, it would be e;Kpedient to
surround the deck >rith a strip of metal, which
should be connected with the copper bottom f
ox if the ship is not coppered, the strip should
be continued qypr the bottom or side of the
keel, and be connected with others embracing
the sides of the ship* The conductor or con-
ductors for the masts, are to be connected with
these metallic strips ; and it then appears im^
posible for injury to occun

Carriages aire tisually filletted roand xnth*
metal ; if these fillets are connected with each
other, a covered carriage appears to be a suffi*-
oiently secure' situation.

As a provision for personal security during*
a thunder storm, a few priecautions ar« ncces-
s&ry. In' the open air, shelter should not be
sought immediately under a tree or building,'^
ftir should they be struck, such a situation is'
pirticuferJy dangerous. Tlie distance of twenty
or thirty feet from tall trees or houses^ i«, on
the contrary, an eligible situatiori; for $boiiklaf
discharge take placej. these prominent 'bodi».
are most likely to receive it, and the less ele-
vated bodies in their neighbourhood n,»y there-
fore escape uninjured.

It is quite essdntial, during a thunder storm,-
t6 avoid every considerable mass of water, litid
even the streamlets that may have resulted from
k recent showcfr ; for these are all excellent con-*
ductors,>fid the height of a human being; whect
cfontiected with them, is very likely tadeter^iiMi
the course of an electrical discharge^

The partial conductors, through which tl)e
lightning directs its course vrhe:?i it enters 4

KERSONAL SAFETT' 831

building, are usually the appendages of. the walls
and partitions; the most secure situation is
therefore the middle of the room» and this situ-
ation may be rendered still more secure by
standing on a glass-legged stool^ ^ hair mat-;
tress, or even a thick woollen hearth rug,-:-i
ITie part of every building least likely to ijc-
ceive injury is the middle story, as the ligbtr
ping does not always pass from the clouds to
the earth, but is occasionally discharged from
the earth to the clouds: hence it is absurd to

• • ■ • - ... '. ... ; I.

take, xefuge in a cellar, or in the lowest story
of a house; and many instances are on record
in which the basement story has been the only
part of a building that has sustained sevarc^
injury, the electric charge being divided and

weakened as it ascended^. Whatever situation
be chosen, any approacii to the fire-place should
be particularly avoided; for (as it has beei|
already stated) the chimneys are very likely to
determine the course of the lightning. The
same caution is necessary with respect to gilt
furniture, bell wir^s, and moderately extensive
surfaces of metal of every description. In a
carriage, the precaution of keeping at somp

132 vfCECAvnovs, kci

inches distant from its sides or back is alsd
adviseable.

I have been rather ample in the enumeni-
tYdn of these particulars, from a desire to supply
What useful information the present state of
our fcAoWlledge may afford, and to diminish that
SiiMetf dnd fear by which the minds of many
4re Oppressed during the occurrence of these
^^rfic^nt but awful phenomena. The ope-
tiUdn of irtysterrous agents has always consider-
ii^le effect on the human niind ; and, By cdti-
jMng up a host of unreal terror^; may suspend
:Ue action of its best en^gies : bnt what wi
krt enabled to ascerf din the nature aiid inftcrenctf
of the powers which surround us, we are pre-
pared to meet their effects with feeKng^ equally
remote from vain confidence and useless fear ;
and are thiis enabled to avoid their dangers ef-
fectually and without ;^gitation.

S3S

CHAP. 11.

On the Phenomena of Thunder Storms^ and oit
the probahit Sources of Jtmosphericdl Eke-
fficity.

L ut experiments that have been detailed de«
inofidtrate, inconttovertibly, that electricity ii
identteal with the phenomena of thunder and
lightning; but its precise operation in the pro*
dttetion of these impressive effects is by no
Hieans clearly understood. The circumstances
inost easily explained are the concomitants 6f
{his natural display of electrical power ; for they
do jiot differ materially in character from the
phttibmekii of the electrical apparatus, and the
ekteiisive scale on which they are produced, ai
wtW as the circumstances of their occurrence,
are ample sources of more considerable variety.
The spark and its attendant report, observed
>Vhen a jar or battery is discharged, are effects
perfectly analogous to a flash of lightning and
its consequent thunder ; and the variety of
tound whi^h characterizes this last, is equally

234 PECULTAErriKS of thundsb.

the characteristic of every single explosion
when it reaches the ear from a distance. A
piece of artillery, discharged in any situation
where the surrounding objects present irregular
sources of reverberation, produces an effect

which might be mistaken for the roar of thunder.

This I have observed in several open situations
of irregular surface, particularly on Hampstead
Ifeath ; and it may also be noticed when the
guns are fired in St. James's Park, ipos^t remark-
ably when the observer is situated, between
them and the buildings towards. Whitehall.

An observation of the varieties, of the natu*
ral phenomenon will confirm this idea. At sea,
where there is no diversity in the reverberating
objects, the sound is reguUr, and decreases in
intensity at every reverberation, until it gra-:
dually dies away ; but in other situations, where
the bodies capable of reverberating are nume7
rous and irregularly placed, a succession of
sounds are heard, varying in loudness and du-
ration with the situation, distance, and nature
of the sources of reverberation, and having no
relation to the interval of time. When the
9ash is immediately followed by the report, a
single explosion of a peculiar crashing sounc|

PtSCULIARlTIES OF THUNDEB. S35

is usually all that is hciurd, for the diiKifaarge has
tihen- tiken place very near the observer, and
damage will m 'Such cases most frequently be
found to hfme occurred in l^e immediate neigh-*
bourbo0^. When the sound does not imme-
diji^y follow the flaMi^ the rumbling and irre^
^lar noise most frequently occurs, for the dis<*
tance is then sufficient to render the reyerbe*
ration (from its extent) the most prominent
feature of the phenomenon.

T^ interval between the flash and the ex-
plosion offers data for calculating the distance
Sif a thunder stroke. For light moves with such
velocity, that the time it requires to traverse
any ordinary distance may be considered! ai|
nothing ; but sound travels only at the rate of
1 142 feet in a second. Tlie flash and the re-

port are really contemporaneous, but the one
ijs immediately seen, and the other requires a
second of time to tra^verse 1 142 feet Conse-
quently the interval that elapses between the
flash and the report being multiplied by 1 14g,
or this last by the number of seconds in the
<interval, will give the distance of the explosion
from the observer in feet. Thus, suppose the
flash of lightning to take place five seconds be-

236 TSCVLIAMTIZB OF TH9NDEB.

fore the thunder is heard, then 5 X 1 142=5710,
or 1 mile 430 feet, which is the distance of tihbe
explosion from the observer. This distance, it
may however be proper to state, cannot be con«
sidered as a measure of his removal from danger;
for it is the measure of an explosion which has
taken place, and those that follow may occur
in very different situations ; for thunder clouds
are sometimes continued over a considerable
extent of country, and two or more flashes arQ
not unfrequently seen in distant parts of the
atmosphere at nearly the same time.

When the spark which causes lightning is
seen, it is of the zigzag form, assumed by all
powerful sparks when they traverse a consider-
able space of air, and in this its natural exhibition,
the spark sometimes traverses a most prodigious
interval. The appearance of two distinct streams
at no very considerable distance from each other
is sometimes produced, when part of a long zig-
zag is concealed by an intervening cloud; and
the sudden and universal flash, called sheet-light-
aing, results from the reflection of an explosion
which is more completely concealed. Of this
last kmd also appear those bright flashes which
occur on summer evenings, and are not accom-

PHENOMSITA OF TUUNDEB. SST

panied by thunder; a circumstance which it is
difficult to account for, unless it may arise from
their great distance from the earth's surface.

By far the greater number of flashes of
lightning are harmless discharges from one
cloud to another, and the instances in which it
strikes the earth are comparatively rare ; hence
it appears that the clouds, or different portions
of the atmosphere, are oppositely electrified ;
and it has been conceived with good reason by
Mr. Morgan, that when the lightning strikes
the earth, the latter may merely act as a dis«>
charging rod to shorten the striking interval
between two charged clouds. Mr. Moi-gan has
indeed supposed, that the earth cannot have its
natural quantity of electric fluid either increased
or diminished, because it is a conductor ; but it
is surrounded by air, and consequently is an in^
sulated conductor ; and our experiments teach
us, that insulated conductors may be rendered
^either positive or negative; therefore the same
may be inferred relative to the earth.

Others have supposed, that when such dis-
charges occur, they result from the electrified
cloud, producing by its proximity the contrary
electricity in the ea^ th ; but when the size of

S23S PUEN051ENA OF THUNDEft;

the largest thunder cloud is compared with our
globe, it will be evident that such an opposition
could produce no more effect than would result

from the approximation of an excited stick of
sealing-wax to an insulated mountain. Besides,
we have experimental evidence that, during the
occurrence of such phenomena, different parts
of the atmosphere are in opposite states of elec-
ti'icity at the same time; and as these states are
dependant on each other, the discharge cannot
take place but by passing from the positive to
the negative, either directly, or by the inter-
vention of part of the earth, between them. •
The different electrical state of different
parts of the atmosphere, obtains principally in
the masses of vapour or clouds that float in it;
and the origin of this electricity, as well as the
cause of its various changes, is probably to be
traced to the mutability of these masses ; for it
has been seen, that change of form, heating and
cooling, friction, and the contact of dissimilar
bodies, are the artificial sources of electrical ex-
citation; and the clouds experience in succes-
sion the operation of all these causes. That
electrical changes are connected with the state
of vapour in the atmosphere, is evident from a

fiLECTEIClTT OF TUe ATMOSPHERE. ^239

consideration of all the phenomena, as will be
apparent from the following facts.

1st. The electrical phenomena of the atttio-
■sphere take place in all climates to the greatest
extent, during or near to the period of greatest
heat, when the operation of the sun's rays has

• ^

occasioned a considerable accumulation of va-
pour.

2d. Where this cause operates to the greatest
extent, as in the countries within the tropics,
these natural electrical phenomena are pro-
duced on a scale of the most tremendous mag-
nitude.

3d. When the natural source of evaporation
is assisted by collateral causes, electrical changes
occdr with astonishing activity. The eruption
of a volcano is almost constantly attended by
vivid lightnings; and the regions that surround
the extensive sands of Africa, where the action
of the sun's rays is assisted by reflection from
•an arid soil, are remarkable for violent storms
and tempests; the air roasted by its passage^
over these sands, producinga rapid evaporation
of the first moisture it meets, and becoming
thereby so loaded as to evolve copious showers
on any sudden din}inution of temperature. ^ . -

S40 KLECraiCITV of the ATMOSPHfiBIJ.

4tb. By the action of wind^, currents of 4|r
of different temperatures are pft^n mixed ; ani^
such as liave been heated and charged vith
moisture, are suddenly cooled ; by this, process
water is precipitated, and electrical changes al-
most constantly occur ; such are tl^c hurrioanes
and terrific lightnings produced by the harinat;*
tan on the coast of Guinea, when it comes in
contact with the cool air on the surface of the

• • • ^

ocean; and. such are also the electrical pheno-
mena of all high ranges of mountains, for they
occasion a condensation of the heated and moi^t
winds that pass over their frozen summits;
hence the magnificent hghtpings of the Cordil-
leras, and the corruscations of the Alps.

5th. Electrical changes are in every. situa-
tion most frequent when the causes of evapora-
tion and condensation suddenly succeed each
other. Those who have made regular observa-
tions on the electricity of the atmosphere, have
alwa)- s observed the greatest diversity when a
rapid succession of rain and sunshine occurs;
and such variable weather is also the most fre-
quently attended by thunder storms. Even the
diurnal changes of heat and cold, produce a per-
ceptible effect on the atmospherical electricity;

fiLfiCTElCITt OF THE ATMOSPfiEEE» 241

for, accordirfg to the bbi^ervations of Mr. Read,
it is most obvious during the morning and even-
ing dew, and weakest in their intervals.

Although the connexion of the circulation
of water in the atmosphere with the production
of its electrical phenomena is thus clearly
pointed out, the immediate nature of this rela-
tion is by no means obvious. Volta discovered,
that when water is rapidly converted into va-
pour, it leaves the vessel from which it has
been evaporated, negative^ and if the ascend-
ing vapour be received on an insulated piece of
metal, it appears positive.* Hence he con-
cluded, that water in expanding has its capacity
for electricity increased, and consequently re-
ceives it from such bodies as are contiguous :
admitting this, the condensation of vapour must
necessarily be attended with positive signs of
electricity, and the circulation of this subtle
fluid in the atmosphere would be analogous to,
and attendant on the circulation of water. But

*. Thk experiment may be made with great fiicllity by
placing a few lighted coals in a crucible^ on the cap of a
gdld-leaf electrometer, and projecting a few drops of water
on them^ whilst an insulated tin funnel is placed about a foot
or 18 inches above. The electrometer will be electrified ne-
gatively, and the insulated funnel positively.

Hi BI-ECTRICZTT OF THE AT¥OSPHERB«

it has been observed by De Sausure and others,
that the electrical effects of evaporation are not
uniform, being directly opposite when different
vessels are employed, and scarcely at all percep-
tible when the evaporation proceeds slowly, as
it does in nature. To this it may be replied,
that by the employment of different materials
for the evaporating vessel, counteracting causes
are probably introduced, by admitting the in-
terference of chemical action, or the contact of
dissimilar bodies; and such anomalous results
have not been observed to occur when the wa-
ter is evaporated from any substance analogous
to the usual materials of the earth's surface. As
to the different intensity of the electrical signs
when the evaporation is more or less rapid, it is
rather favourable than inimical to the opinion,
for such, it has aheady been observed, is also
the case in nature; and if the usual process of
natural evaporation produced an effect for each
drop of vapourized water, equally powerful with
that obtained in the usual mode of conducting
these experiments, the assigned source of at^
mospherical electricity would be by far too pro-
lific, and perpetual thunder storms an almost
unavoidable consequence. For it has been cal-

ELBCTKtCITT OF TH£ ATHOSPHERE. Sl4S

culated, that about 5280 millions of tuns of
water are probably evaporated from the surface
of the Mediterranean in one summer's day.*
And a more recent estimate considers the mean
evaporation from the whole earth, as equal to a
column of 35 inches, frort every inch of its sur-
face in a year ; which gives 94.450 Cubic miles
of water, as the quantity that circulates through
the atmosphere annually .t

The extent of these phenomena is therefore
fully adequate to the production of all the ob-
served effects of atmospherical electricity ; and
the constant proportion of the effects to the
operation of their assigned cause, renders that
idea extremely plausible : but the observations
of M. De Luc :j; militate rather strongly against
it ; they are not indeed opposed to the preced-
ing statement, for that is an enumeration of
facts ; but diey tend to overthrow the principal
hypotheses that have been advanced to account
for the production of atmospherical electricity.

* Ca¥a11o*8 Natural Philosophy, vol. ii. p. 409.

t Thomson's Chemistry^ vol. ir, p. T^i ^^^ Manchester
Memoirs, vol. v. p. 360.

t Ides sur la M6t6orologie, torn. ii. p. 158; or Nicholson's
Journal^ vol. xxyti. p^ 241, &c.

S44 ELECTBICITY OF THE ATM08JPU£iEt£.

The attention this excellent philosiopher has
paid to every subject connected with Meteor-
ology, the acuteness of his views, the accuracy
and extent of his experiments, and the unre-
mitted continuation of his inquiries^ conferva
value on his observations that it is impossible
to appreciate too highly; and whilst it affords
me considerable pleasure to acknowledge . the
general accuracy of the objections he has urged,
and the insufficiency of the tenets to which
they are opposed, it is with no small diffidence
I decline an assent to some of the explanations
he has proposed in lieu of them. The limits of
this work will admit no extensive theoretical
discussion, I must therefore refer the reader to
the Id^es sur la Meteorologie, and to M. De
Luc's various papers in the Philosophical Trans-
actions, and in Nicholson's Journal, for an ac-
quaintance with his luminous views ; which em-
brace the most important phenomena in Meteor-
ology and the sciences connected with it.

The labours of M. de Luc, last referred to,
sufficiently prove that we are at present quite
unacquainted with the nature of the process by
which the apparent circulation of water through
the atmosphere is effected. Evaporation will

£L£CTRICITT OF THE ATMOSPHEIIE: S45

go on for months, and the air appear still dry;
and driest in its upper strata, where th^ ascend-
ing vapours are supposed to pass : and in a stra-
tum of this kind, where there is no evidence of
the existence of any adequate quantity of mois-
ture, clouds will suddenly form, andi produce
violent rain, accompanied by thunder and light-
ning, frequently of long duration. Nor are
these clouds produced by any ^Sudden conden-
sation, for the heat of the clouds themselves is
sometimes greater than that of the air by which
they are surrounded;* and clouds that have
been formed in the day frequently disappear at
liight, when, from the increased condensation,
their continuance or increase might have been

expected. • - .

None of the principles, then, that have been
hitherto advanced are adequate to account for
the formation of clouds and rain ; we have no
evidence that thfey result from the saturation
of the atmosphere with moisture, for they are

* De Luc sur la M6t6orologie^ Vol. ii. p. 100. This obser-

yatioD appears to me anomalous, for all bodies that are condensed

have their tempeiiature raised ^ and, consequently, if clouds are

formed by the eondensation of vapour, their heat should le

9:€ater than that of tbe air by which they are-surrounded*

S46 BLECTRICITY OF THE ATIIOWftEai*

frequently formed in apparently dry air; we
cannot shew that they are produced by cold,
for the most remarkable changes of temperature
are sometimes unattended by such phenomena ;
nor can we conclude with Dr. Hutton that they
are occasioned by the mixture of air of different
temperatures^ for they frequently occur in a part
of the atmosphere unagitated by winds either
above or bdlow; and it is not easy to conceive
a mixture of this kind that will account for tbe
quantity of rain that is frequently discharged on
a sudden from a calm atmosphere.

In what state then does vapour exist in tlrt
atmosphere, when it is thus shrouded as it were
from our observation ? and by what process is it
enabled so suddenly to display its energies, and
leave its concealment with the accompaniment
of such tremendous phenomena ?

To this question we can reply only by sup-
positions, which are probably as remote from
the truth as those which have been exploded by
the discovery of these facts.

Mr, De Luc thinks its essential to conclude,
that water may be converted into atmospheric
air, and that the production of clouds and va-
pours arises from the decomposition of this

SLECTRICITT Of TH£ ATHOSPHSRS. 247

nir; and he also conceives that the electric Huid
is a composite body, consisting of light, heat^
and a peculiar species of matter which are com*
bined together during some chemical changes
in the atmosphere, and thus give rise to its elec*
trical phenomena.

To me it appears quite unnecessary to sup*
pose, that when any power or substance is la**
tent, it has necessarily changed its form ; and
no such supposition has been yet admitted in
various decisive instances of the kind : heat, fot
example, when it passes from an appreciable to
a latent state, is not conceived to have under-
gone any change in its identity, but to have
passed into a state of combination, or natural
distribution ; and the same may be said of elec-
tricity, which, as it has been already shewn, is
always latent when its natural attraction is ba-
lanced. Even the power of attraction itself may
be considered in the same way ; that power is
evident when a stone m falling; it i» latent
when the stone has fallen ; but it still exists,
unchanged, though unobserved.

The density of the air decreases in propor-
tion to its distance from the earth ; its particles
are consequently at the greatest di&tadce from

248 ]KLECTRICITT OF THE ATMOSPHERE.

each other in the most elevated stratum ; and
this may possibly be one cause in the produc-
tion of these intricate phenomena. The rays of
the sun reach the upper part of the atmosphere
first, yet there the effect they produce is most
trivial. The earth is most probably the original
source of atmospherical electricity ; but its ef-
fects are most apparent in the higher parts of
the atmosphere ; may not therefore the greater
or less distance of the particles of air have an
influence on the action of the electricity, heat,
and vapour, that exist between them ? and is it
not equally plausible, that the phenomena in
question may be produced by the approxima-^
tion or recession of these particles, as that they
result from unknown combinations and decom-
positions ?

Speculations of this kind are only useful as
a stimulus to inquiry, and should therefore be
always regarded with caution, and offered with
diffidence ; . they are indeed more favourably to
the. progress of true knowledge, when proposed
as questions for experiment to resolve, than
when expanded ipto hypotheses for experi-
ment to confirm, For it is an impolitic ex-
citement of false confidence, to erect a mas-

ELECTRICITY OF THE ATMOSPHERE. 249

sive superstructure on a basis of doubtful sta-
bility.

Although the immediate causes by which
the various phenomena of the atmosphere arc
produced, are still far beyond our comprehen-
sion ,• yet the connexion of their several effects
is a sufficient demonstration that they are not
purely mechanical, but subservient to the direc-
tion of supreme power arid intelligence. By
this means the most simple arrangement be-
comes the source of sublime effects. The. pro-
cess of evaporation which modifies the action
of the sun's rays, and conveys to every part of
the earth's surface a source of fertility, at the
isjame time diversifies the appearance of the at-
mosphere by an endless variety of imagery, en-
livens the horizon with the most brilliant and
glowing tints, and probably effects those elec-
trical changes, which are the precursors of the
most magnificent phenomena in nature.

260

CHAP. IIL

On some luminous Phenomena of the Atmosphere^
the Observation of Atmospherical Electricity^
and the Arrangement of a new System of In-
sulation.

The satisfactory demonstration of the agency
of electricity in the production of thunder and
lightning, has occasioned the application of its
principles to the solution of other phenomena,
and in some instances it applies more plausibly
than any other existing explanation. Such is
particularly the case with some of those lumi-
nous appearances that occasionally enliven our
atmosphere; effects, which have always been,
and still continue amongst its most mysterious
phenomena.

The Aurora Borealis, or northern light, is a
phenomenon of this kind, whose appearance so
exactly resembles some of the effects of artifi-
cial electricity, that those who have had the op-
portunity of comparing it with them, can en-
tertain no doubt that their causes are identical.

yORTHERK XIOBTS; S51

When electricity passes through rarified air,
it exhibits a diffused luminous stream, which
has all the characteristic, appearances of the
northern lights^ There is the same variety of
colour, and intensity ; the same undulating mov
tion, and occasional corruscations ; the streams
exhibit the same diversity of charadter, at one
moment minutely divided in ramifications, and
at another beaming forth in one body of lights
or passing in distinct broad flashes ; and when
the rarefaction is considerable, various parts of
the stream assume that peculiar glowing colout
which occasionally appears in the atmosphere^
and is regarded by the uninformed observet
with astonishment and fear.

There is therefore little doubt, that the na^
tural phenomenon i& occasioned by the passage
of electricity through the upper regions of the
atmosphere. The lowest estimate that has been
made of the distance from the earth's surface at
which it occurs, is that of Mn Cavendisli, who •
states that distance to be 7 1 miles ; now, at 70
miles, the air is 1048576 times more rare thatt
at the surface of the earth ; and this is a degree
of rarefaction beyond the power of any air-
pump yet qqnstructecL .

252 KORTHERV LIGHTS.

These circumstances tend almost to a de-
0ionstration, that the light of the aurora is pro-
duced by the same means as the light of elec-
tricity; but there are other characteristics of
that remarkable phenomenon that still remain
unexplained.

Dr. Halley has described very fully the ap-
pearance of a remarkable Aurora, and has col-
• lected together a variety of observations that
may serve as a history of its phenomena;* he
ascribed its production to the same influence as
that which causes magnetism^; and the observa-
tions of Mr. Dalton prove that the dhrection of
the luminous beams of the aurora is really that,
of the dipping needle.f Signior Beccaria con-
ceives that, the phenomena of magnetism are
occasioned by a constant natural circulation of
the electric fluid from north to south, origi-
nating from several sources in the northern he-
misphere. The aberration of the common cen-
ter of these currents from the north point, he
supposes, may cause the variation of the needle;
the period of this declination . from the centre

* Phil. Trans, vol. xxx, p. IO99, or Mottc's Abridgmcot,
vol. ii. p. 116.

f Dalton's Meteorological Essays, p. 157.

NORTHKaN; LIGHTH. S5S

itiay be the period of the variation ; and the ob-
liquity of the currents the cause of the dip of
the magnetic needle. '

The northern lights arc at present very
rarely visible here; a very few years since I ob-
served them several times, and on one occasion
their appearance was remarkably brilliant, and
very similar to that noticed by Mr. Dalton in a
phenomenon of this kind, which appeared ou
the 13th of October, 1792. An extract from his
description will convey a general idea of an
effect we have but rarely an opportunity to obr
serve. ■ ,

" Attention was first excited by a remark-
ably red appearance of the clouds to the south,
which afforded sufficient light to read by, at
eight o'clock in the evening, though there was
no moon, nor light in the north. Some remark-
able appearance being expected, a theodolite
was placed to observe its altitude, bearing, &c,

" From 9x to 10 P. M. there was a large,
luminous, horizontal arch ta the southward, al-.
most exactly like those we see in the north ;.
and' there was otie or more faint concentric
arches nor^h^^ard. It was particularly noticed,
that all the arches seamed exactly bis^qted by

25i KORTtnLRW LIGHTS.

the plane of the magnetic meridian. At half
past 10o*clock, streamers appeared very low in
the S. E. running to and fro, from W. to E., they
increased in number, and began to approach the
zenith, apparently with an accelerated velocity ;
when, all on a sudden the whole hemisphere
was covered with them, and exhibited such an
appearance as surpasses all description. The
intensity of the light, the prodigious number
and volatility of the beams, the grand inter-
mixture of all the prismatic colours in their ut-
most splendour, variegating the glowing canopy
yrith the most luxuriant and enchanting sce-
nery, afforded an awful, but at the same time
the most pleasing and sublime spectacle in na-
ture. Every one gazed with astonishment ; but
the uncommon grandeur of the scene only last-
ed about one minute; the variety of colours
disappeared, and the beams lost their lateral
motion, and were converted, as usual, into the
flashing radiations ; but even then it surpassed
all other appearances of the aurora^ in that the
whok hemisphere was covered with it.

" Notwithstanding the suddenness of the ef-
fulgence at the breaking out of the auroray there
was a remarkable regularity in the manner.—

SOUTHERN L10BJ$, S55

Apparently a ball of fire rah along from east to
west, and the contrary, with a velocity so great
as to be barely distinguishable from one con-
tinued train, which kindled up the several rows
of beams one after another : these rows were
situate before each other with the exactest or^
der, so that the bases of each row formed a
circle crossing the magnetic meridian at right
angles ; and the several circles rose one above
another in such sort, that those near the zenith
appeared more distant from each other than
those near the horizon, a certain indication that
the real distances of the rows were either nearly
or exactly the same. And it was further ob-
servable, that during the rapid lateral motion of
the beams, their direction in every two nearest *
rows was alternate, so that whilst the motion
in one row was from E. to W., that in the next
was from W. to E.

The point to which all the beams and flashes
of light uniformly tended, was iu the magnetic
taeridian, and as near as Could be deteimined,
between 15 and 20 degrees south of the zenith.
The tmrora continued, though diminishing in
splendour^ for several hours. There were se-
veral meteors (falling stars) seen at the time;

256 NOftTHBftN LIGHTS.

they seemed below the aurojra, and unconnected
therewith."*

When the northern lights are visible in thisf
country, they are said to appear chiefly in the
spring and autumn, and usually after a period of
dry weather ; they do not refract the light of
the stars, which are often distinctly seen through
the luminous arch or beams*

They are seen more rarely in countries
nearer the Equator, but occur almost constantly
during the long winters, iii the polar regions,
and with a lustre of which we can form but a
faint conception.

In the Shetland iles they are called " merry
dancers," and are the regular attendants of clear
• evenings, giving a diversity and cheerfulness to
the long winter nights. Their first appearance
is at twilight, just above the horizon; they
have at first no particular brilliance or motion,
but after some time break forth into streams of
refulgent light, whose Protean columns gradu-
ally assume every possible variety of form, and
shade of colour; frequently covering the whole
visible hemisphere; which then presents the
most brilliant spectacle imagination can con-
ceive.

* Daltpn^s Meteorcjogical Essays^ p. 65,

...i-«

NORTHERN LIGHTS. 257

In Hudson's Bay, the refulgence of the au-^
rora is stated to be frequently equal to that of
the full moon. In the northern latitudes of
Lapland and of Sweden their brilliance is so
remarkable and constant, as to enliven the path
of the traveller during the whole night. In the
north-eastern parts of Siberia they are also de-
scribed as moving with incredible velocity, and
clothing the sky with a most brilliant luminous
appearance, ^* resembling a vast expanded tent,
glittering with gold, rubies, and sapphire." This
phenomenon is said to be accompanied by a
loud hissing or crackfliig noise, so terrific, that
when the fox hunters, on the confines of the
icy sea, are overtaken by it, their dogs lie close
to the ground, and refuse. to move until the
noise has passed.

That a noise of this kind occasionally ac-
companies the northern lights, has been testified
by several observers, and amongst others by
Mr. Nairne and Mr. Cavallo ; the last says, he
has heard it distinctly on several occasions.
This effect is the most extraordinary of all that
accompany these phenomena, and if established
as a fact, is perfectly unaccountable; for, from
the extent of country ov^r which the aurora is

25& NORTUlttN LIGHTS.

frequently seen, it is certain that it mu«t occur
at a very considerable height above the earth's
surface; and though the calculations on this
subject differ remarkably,* yet the very lowest
estimate gives an elevation, at which, accord-
ing to the known principles of philosophy,
there exists no medium capable of transmitting
sound !

An aurora has been sometimes observed near
the south pole, which seems to favour Beccaria's
idea, that its cause is the circulation of a fluid.
Its appearance is similar to that of the northern
light, but without the same diversity of co-
lour.

The beams of the aurora appear to converge
towards the zenith, and their summits seem
narrower than their bases ; but this, as was ob-
served by Dr. Halley and Mr. Cavendish, is
merely an optical illusion; and it has been
shewn by IMr. Dalton, that the beams are really
cylindrical, and parallel to each other; and that

* The height of an aurora was determined by Boscovich at
825 miles. By Bergman, from a mean of thirty computations,
at 468 miles. By Euler, its height is estimated at several thou-
sands of miles. By Mairan, at 200 leagues. Mr. Cavendish,
by a comparison of observations, states it at from 50 to 7^
miles. Mr. Dalton and Mr. Crosthwaite, at 150 miles.

the distance of their bases from the earth, is
equal to^ or probably greater than the length
of the beams.: and he has calculated diat these
beams are 75 miles long, and 74- miles dia*
meter.*

The other luminous appearances of the at-
mosphere which have been attributed to elec*^^
tricity, are those usually called Meteors, or Fire-
Balls. Of these there are two very distinct
classes ; the one of considerable apparent size,
moving progressively over a very considerable
space, and sopietimes dispersing in divided
fiparks.f ' These occur but rarely, and their dis-
persion is sometimes attended by the fall of
stones; a fact which renders the application of
electrical principles quite insufficient to explain
them. Until lately, tlie statements of the fall
of meteoric stones were but slightly credited;
but considerable attention having recently been
bestowed on the investigation of these ac-^
counts^ and the examination of the stones said

* Meteorological Essays, p. 177.
' f A remarkable meteor of this kind occorred in Augnst 1 783.
It!waa observed by Mr. Cavallo, from the terrace of Windsor
Castle, and is described by him in the Philosophical Transac-
tions for 1784, article 9th J and also in the 4th volume of bis
Natural Pbilosopby, p. 359.

860 2IETE0ES.

to have fallen ; the fact appears' to be establish-
edy and with the remarkable circumstance, that
all the stones of this kind hitherto examined
are of nearly similar composition. .

In the present state of our knowledge no sa-
tisfactory explanation of these meteors can be
given: all that has been proposed on the subject
is perfectly visionary ; and the details of vague
speculation would be but tedious and useless.
Electricity is inadequate according to our pre*
sent acquaintance with its agencies, and some
of the concomitant phenomena indicate, almost
to a demonstration, that combustion is con*
cerned in the production of these appearances.

Tlie second kind of meteors occur much
more frequently; they are usually called falling
stars, or shooting stars; they vary somewhat
in size and colour, but have nearly the same
rapidity of motion, moving swiftly in various
directions, but chiefly inclining towards the
earth. They occur in various states of the at*
mosphcre, but most frequently when the ob-
served causes of electrical change have been
most active ; hence they are found to prevail ia
clear frosty nights, and at other times when
there are dry easterly winds, and a clear sky;

HETE0R8. S6l

they also abound in the clear intervals of
showery weather, and on those summer even-*
ings when well-defined clouds are floating in a
clear atmosphere. I have observed them most
frequently at times when considerable extrane*
ous light prevailed, either from the clear re-
fulgence of the s.tars and planets, or from the
presence of the moon ; but I have also noticed
theni on partially cloudy, and dark nights.

Various are the observations that prove theij
occurrence during the splendid display of the
northern lights; and it is a remarkable fact,
that they always appear lower than those lights,
which seems to indicate that they are in all pro-
bability the same matter moving through a
more resisting medium.

' In favourable states of the atmosphere these
appearances succeed each other with such ra-
pidity, that I have frequently counted 30 in
the space of a single hour ; and on some occa-
sions nearly twice that number. The frequency
of their occurrence indicates, that they are pro-
duced by some of the usual atmospherical
changes ; and the circumstance of no meteoric
stones being produced by them, renders it al-

S6S METEORS*

most certstin, that their nature is mat^ialijr difi
ferent from that of the large meteors.

Independent of other sources of analogy, the
following are striking arguments in favour of
their electrical origin.

1 St The light of falling stars is siniiiar to
the light of the electric spark.

2d. They occur as frequently and as irre-
gularly as other electrical changes in the atmo^
sphere.

3d. Their motion, like that of electricity, is
inconceivably rapid; and the longest interval
they strike through, is traversed in an interval
of time too minute to admit of measurement.

4th. They occur most frequently, during, or
near to those changes of weather, that are
known to influence the electrical state of the
atmosphere.

5th. Their direction is never constant; they
occur in every part of the atmosphere, and move
in almost every variety of inclination ; such is
also the case with lightning.

6th. The appearance of falling stars may be
accurately imitated by electricity ; and the cir-
cumstances on wliich the success of such ex-

periments depend, are such as are likely to ocw
cur in the production of the natu]:al pheuon
menon.

If electricity be passed through a,n exbausjb^
ed receiver gradually, it assumes the appearance
of the northern lights; but if a considerable
electrical accumulation be suddenly transpnitted)^
it will pass through the receiver with all the
straightness and brilliance of a falling stan If
the receiver is six inches diameter, and fourteen,
or sixteen inches high, the full charge of a mo-,
derate sized jar is necessary to produce this efn
feet, and it occurs most readily when the re-
ceiver is but moderately exhausted, so that the
rarefied air it contains may have some degree of
resistance.

The artificial imitation of the two pheno-
mena, therefore, require the same conditions for
their production as appear to obtain in nature.;
for the aurora occurs in the highest parts of the
atmosphere where the air is most rarefied ; and
th^ most accurate imitation of its appearauce,
is obtained in the most perfectly exhausted re-
ceiver; falling stars take place much lower,
where the air has more density^, and to imitate

them, it is necessary to employ a medium that
opposes some resistance.

These facts are confirmed by almost every
possible variation of the experiment, and in
some instances the approach to the appearance
of the natural phenomenon is remarkably strik-
ing ; for the electric fluid may be made to pass
over a very considerable interval by the em-
ployment of a proper apparatus*

I employ for this purpose a glass tube, five
feet in length, and j-8ths of an inch diameter, .
capped with brass at each extremity. When this
tube is exhausted, no ordinary spark will pass
through it in any other than a diffused state,
but by employing the charge of a very large jar
a brilliant spark is obtained through the whole
length of the tube. Mr. Morgan found, that
in a shorter tube of the preceding description,
the appearance of a falling star was produced
by a spark which would pass through ten
inches in the open air, provided the tube did
not exceed forty-eight inches in length, and
contained a quantity of air, which under com-
mon circumstances would have filled one-twen-
ty -fourth of its capacity; but if this small

IIETEORS. SI65

quantity of air was further dilated by the action
of an air-pump, the most powerful spark would
pass through it in a divided stream. By employ-
ing a very narrow tube of the same length, the
confined column of rarefied air resisted the
charge sufficiently to produce the appearance
of the brilliant spark through its whole length,
whenever the accumulated electricity was suf-
ficiently powerful to pass through it.

These experiments, and the analogies by
, which they are supported, render it highly pro-
bable that electricity is connected with the ap-
pearance of these lesser meteors ; but neither
the precise mode of their production, nor the
purpose they answer, is as yet by any means
explained.

In a very electrical state of the atmosphere
Q. luminous appearance is sometimes observed on
the summits of spires and the masts of ships,
and a similar effect has been occasionally no-
ticed on the points of spears ; it is analogous
to the light that appears on any slender and
prominent conductor, when it is surrounded by
electrified air, or approximated to an excited
electric.

Earthquakes, water-spouts, and even volca-

S66 ELECTBICAL KITE.

noes have been ascribed to the agency of eleo-
tricity ; but the idea is not supported by any
othier circumstance than the occasional occor-
rence of some electrical effects during the ope-
ration of such phenomena ; and it i^ much more
probable that these are a consequence of their
action^ than an evidence of the caus^ by whicH
they are produced.

The electrical phenomena of the atmosphere
are not confined to its luminous effects, for it
has been found that the air is almost constantly
electrified; and observations have been made
on the character and mutations of its pheno-
mena, by the aid of kites, insulated rods, and
extended wires. It may be interesting to give
some account of the structure and arrangement
of these several sources of inquiry.

An electrical kite should be constructed in
the most simple manner, for it is an apparatus
very liable to be injured or lost; its size should
be moderate, as there is not often sufficient
wind to raise one that is very large, which is
besides, on several other accounts, very trouble-
some to manage. An ordinary paper kite, about
four feet in height, and two feet wide, varnished
with drying oil to defend it from the rain, h

.ELECTfUCAI. KITI, ' 267

•ufficicntly well adapted for this purpose. Th«
string must be made with a thin copper or silver
thread (such as is used for gilt lace) en twisted
with the twine of which it is formed through
its whole length. When the kite is raised, the
string is insulated by attaching to it a silk cord,
•whose opposite extremity may be fastened to z
rail, or any fixed or heavy body. The end of the
metallic string is to be connected with an insu-
lated conductor, and at two inches from the
extremity of this conductor a brass ball, well
connected with the ground or the nearest water,
is to be placed ; so that when the electricity is
sufficiently intense to pass an interval of two
inches, it will be conducted safely away with*
out injury to the experimentalist, who should
be cautious, in such cases, not to approach the
insulated conductor; but if he has occasion to
remove any apparatus to or from it, to do so by
the aid of long insulating handles or forceps.
jBy an attention to these circumstances, M. de
Jlomas was enabled to manage with security the
very formidable accumulation already stated to
have occurred in his experiments ; but as no
useful purpose appears likely to be accomplish*
ed by such temerity, I should rather advise, on

S68 ELECTBICAL KITE.

every similar occasion^ an immediate retreat to
a secure distance from the apparatus.

In raising or lowering the kite, the shocks
that are sometimes inadvertently received may
be effectually prevented by suffering a part of
the string between the operator and the kite to
bear constantly against the brass ball that is
connected with the ground; and this precau-
tion is very essential when thunder clouds are
over head; but on such occasions, it is quite
unnecessary to raise the kite, since the atmo-
spherical electricity may then be observed by
more simple means.

The effects obtained by an electrical kite
are usually greater in proportion to the length
of the string; and when the atmospherical
electricity is very weak, it has been sometimes
found necessary to employ two or three kites,
one above the other, that a sufficient length of
conducting cord might be exposed to the air.
These additional kites have each a long slit
through the middle stick, or straiter ; and when
the first kite has taken as much cord as it will
carry, the end is passed through the slit of a
second kite and tied to its string; and when
tliis has arisen as high as it will, a third kite

beccaria's expjeiriment. 269

inay be added in the same manner; but it is to
be observed, that the opposite currents of air
that frequently prevail at different heights in
the atmosphere are very apt to interfere with
the success of an experiment of this kind.

,It is evident that the kite serves merely to
extend a length of conducting cord in the at-
mosphere, and as it is not suited for permanent
observations, other means have been employed
for that purpose. Signior Beccaria extended a
long wire permanently between the top of a
cherry-tree and the summit of a long pole at*
tached to a stack of chimneys. Its extremities
were insulated by glass covered with sealing^
w^, and defended from the rain by small funr
nela of tin. A branch proceeded from this wir«
through a pane of glass into his room, where
observations were made on the electricity col-
lected by this apparatus, and its indications
compared with the action of the hygrometer,
and with other concurrent phenomena.

The wire usually extended was 132 French
feet in length ; it was placed on the top of the
Hill of Gar^egna, in the vicinity of Mondovi;
an elevated situation, from which the whole
co]:Dpass of the Alps and the plaiqi of Piedmont

t70 BSCCABIA'b £XP£EI1ISKT.

is perceptible. At one time be also streicbed
an insidated rope, of 1500 Paris feet long, oveit
tbe river Po, wbich exhibited intense signs of
electricity wbenever a shower was falling.

Tbe observations, of this assiduous philoso-
pher were continued above fifteen years ; they
prove that the atmosphere is almost constantly
electrified, and that its electricity is usually
positive^ and has a manifest relation to the state
of the vapour it contains : the electrical indi-
cations of the apparatus are frequently affected
by tbe passage of clouds over it, and by the
transition of a cuxrent of air from any situation
where clouds are forming or vapours faUing.
With the exception of the action of circum-
stances of this kind, negative electricity is rarely
observed in tbe atmosphere, arid it appears
therefore probable, that when it does occur, it
may result from the action of the strong posi*
tive charge of one part of the atmosphere oft
the natural electricity of another contiguous
portion ; or, in other words, that the signs the^i
produced result from the influence of the per-
manent atmospherical electricity, and not from
its actual communication.

My friend, Andrew Crosse, Esq. of Broom-

£L£.CTRIGITT QF THE ATMOSPHEUL 271

field, near Taunton, a most active and intelli-
gent electrician, has lately made very numerous
observations with a remarkably extensive atmor
spherical conductor, consisting of copper wire
one^sixteenth of an inch thick, stretched and
insulated between stout upright masts of from
100 to 1 10 feet in height The most unwearied
exertion has been employed to give unexampled
extent and perfection to this apparatus ; the in*
sulated wire has been extended to the extraor*
dinary length of one mile and a quarter ; and a
variety of ingenious contrivances have been
applied to preserve the insulation ; but the
length of the wire rendered it so liable to in-
jury, and subject to depredation, that it has
been found expedient to shorten it to 1800 feet;
and until the present time no means have been
devised that sufficiently preserve the insulation
during a dense fog or driving snow.

There are some minor inconveniences at-
tendant on the use of this apparatus, which are
obviated by fixing it very securely, and pro-
viding a contrivance by which it can readily be
raised or lowered to cleanse the insulators ; for
these are sometimes rendered conducting by
fl{>ider'& webs ; and the secure fixing of the wire

273 ELECTRICITY OF THE ATH0S:PH EKE.

is essential to resist the weight of inniunerable
swallows that occasionally perch upon it, and.
of wood pigeons and owls, which frequently fly
with considerable force against it.

A wire of this kind has been kept strained
for eighteen months without injury ; and from
the obseri'ation of its indications, and those
obtained in other experiments of less duration^
the following deductions have been made.

1st. In the usual state of the atmosphere, its
electricity is invariably positive,

2d. Fogs, rain, snow, hail, and sleet pro^
duce alterations of the electric state of the
wire : it is usually negative when they first ap*-
pear, but oftentimes changes to positive, in-
creasing gradually in strength, and then gra-^
dually decreasing and changing ^its quality
every three or four minutes. These phenomena
are so constant, that whenever the negative
electricity is observed in the apparatus, it is
considered as certain there is either rain, snow,
hail, or a mist in its invnediate neighbourhood,
or that a thunder-cloud is near.

3d, The api)roach of a charged cloud proi-
duces sometimes positive and at others negative
signs at first j but, whatever be the original

ELECTRICITY OS THE ATMOSPHEBEi 273:.

character, the effect gradually increases to a cer-.
tain extent, then decreases, and disappears, and
is followed by the appeawnce of the- opposite
signs, which gradually extend beyond the formei*
maximum, then decrease, terminate, and are again
followed by the original electricity. These alter-,
nations are sometimes numerous, and are more
or less rapid on different occasions ; they usually
increase in intensity at each repetition, and at
last a full dense stream of sparks issues from
the atmospherical conductor to the receiving
ball, stopping at intervals, but returning with
redoubled force. In this state a strong current
of air proceeds from the wire and its connect-
ed apparatus ; . and none but a spectator can^
conceive the awful though sublime effect of
such phenomena. At every flash of lightning
an explosive stream, accompanied by a peculiar
noise, passes between th$ balls of the apparatus,
and enlightens most brilliantly every surrqundT
ing object, whilst these effects ^tq heightened
by the successive peals of thunder, and by the
consciousness of so near an approach to its

cause. ...

During this display of electric power, so
awful . to . ^n ordinary observer, the electrician

Sl74k SLECTEICITT OF THE AXaiOSPHEKE. '

sits quietly in front of the apparatus, conducts
^ lightning in any required direction, and
employs it to fuse wires, decompose fluids, or
fire inflammable substances ; and when the ef^
fects are too powerful to attend to such experi^
mehts securely, he connects the insulated wire
with the ground, and transmits the accumulated
electricity with silence and with safety.

4th. A driving fog, or smart rain, frequently
electrifies the apparatus nearly to the same
extent as a thunder cloud, and with similar
changes.

5tk In cloudy weather weak positive elec''
tricity usually prevails : if rain falls it frequently
changes to negative ; but the positive state is
resumed when the rain ceases.

6th. In clear frosty weather the positive
electricity is stronger than in a fine summer's
day. The intensity of the electrical signs at
different seasons is expressed, in descending
order, in the following list, commencing with
that whose effects are most considerable.

1. During the occurrence of regular thunder-
clouds.
2.- A driving fog, accompanied by small rain.

ELECTRiCIXr OF THE ATltOSPVERE. 475

\ 3. A fidl of snow, or 1 brisk hail-stdrm. .

4. A smart shower, especially on a hot day.

5. Hot weather succeeding a series of wet day^;
- 6. Wet'weather following a series of dry days*^

7. Clear frosty weather, either night or day, ^

8. Clear warm summer weather.
•9. A sky obscured by clouds.

10. A mackarel-back, or mottled sky.

\\. Saltry weather, the sky covered with light

hazy clouds.
12. A cold damp night

To this may be added, as least electrical of
all, a peculiar state of the atmpsphere which
sometime^ occurs during the prevalence of
Borth-easterly winds ; it is characterized as par*
ticularly unhealthy, and is remarkable in pro-
ducing a sensation of dryness and extreme coldy
which is not accompanied by a correspondent
depression of the thermometer.
' The usual positive electricity is weakest
during the night ; it increases with the sun rise,

decreases toward the middle of the day, and in-

. . • • • ■,

creasing as the sun declines, it then again di-
luinishes, and remains weak through the night.
This fact is one of the most^nstnictive result-

T S

276 TABIOUA )NSTaUM£NT9. . .

ing from these observations, and is confirmed
by most of the regular experiments on atmo-
spherical electricity that have been made; it
clearly proves that the electricity of the atmo-
sphere is influenced by the same causes that pro-
mote the equal distribution of moisture.

A very regular series of observations on the
electricity of the atmosphere, have been also
made by Mr. Read of ICnightsbridge. His ap
paratus consisted of a deal rod 20 feet long,
which was secured very firmly at the bottom
by supports of glass covered with sealing- wax,
within a room in the upper story of his hoiise;
the insulation was by this means better pre-
served than when freely exposed in the open
air. The upper extremity of the rod passed
through the centre of a hollow wooden cylinder
fixed through the cieling and the roof; and the
interior of the cylinder was defended from the
rain by a large tin funnel affixed to the rod at a
little height above its upper extremity.* The
observations made during two years with this

* A description of the apparatus, and a journal of the obser*'
vatioDS made ^ith it, may be seen in-^ 81st volume of the
Phil. Trans, p. 185, &c. or in Bead's Summary View of Spon-*
taneous Electricity, p, 103.

VARIOUS INSTRUMENtS. S77

apparatus, agree very nearly with the precede
ing deductions.

For temporary or occasional observations^
very simple contrivances may be employed, A
common jointed fishing-rod having a glass stick
covered with sealing-wax substituted for its
smallest joint, may be occasionally projected
out of the upper window of a house. A pair of
pith balls must be attached to a cork in which
the end of the glass stick is thrust; and this
partof the apparatus is to be occasionally un-
insulated, by placing a pin in the cork, connect^
ed with a thin wire held in the hand. In this
uninsulated state, the fishing-rod and its attach-
ed electrometer are to be held for a few seconds
projecting from the window, and whilst in this
position the pin is to be withdrawn by pulling
the thin wire ; this insulates the electrometer,
which may be then drawn in and examined.
Its electricity will bQ contrary to that of the
atmosphere.

Mr. Bennet recommends a tin funnel insu-
lated by means of cement at the extremity of a
long rod. A wire is to proceed from the funnel
to a sensible electrometer placed within doors;
and when the atmospherical electricity is weak^

tjt KEV^ rrsTxir of iksulatxcn.

a. torch or small lamp may be attached' to tibc
funnel, for flame facilitates the cpUection of
electricity froih air.

. . In every arrangement of this kind» the prin/*
cipal difficulty is the preservation of the inau^
lation; and when minute differences fh>m the
electrical standard are to be investigated, this
difficulty is productive of the most serious in*
eonvenience. Insulation may, (as it has been
before noticed,) be partially preserved by coat-
ing all the glass insulators with sealing-wax;
but this supplies only a temporary defence
moisture is eventually precipitated on them^
and in removing this, it is scarcely possible to
avoid exciting the surface of the wax, which>
by producing a new source of electricity, ren-
ders the result of every delicate experiment
equivocal. I have been successful in an at-
tempt to obviate this inconvenience to a very
considerable extent, by a new arrangement of
those parts of any delicate electrical apparatus
on which the permanence of its insulation may
depend.

Reflecting that the perfection of insulators
is constantly diminished by the deposition of
jnoisture from the atmosphere on their surfaces,

K£W &Y8TEM OF INSUJLATIOBT. S79

.and that this moisture exists therein difiiised as
one gas mixed with another; it seemed to fol-
low, that if the contact of the atmosphere with
the insulators was less free, their insulation
would be longer preserved, as the transition of
moisture from it to them would be necessarily
retarded. It was obvious this might be effected
-by enclosing the insulator within a narrow
channel, as the air in contact with it would be
then limited in quantity and little disposed to
motion ;, for all gases communicate slowly with
each other when separated by narrow tubes,
and slower in proportion as these are less in
diameter, and of greater extent

The application of this principle to the per-
fection of the gold leaf electrometer was iht
iirst trial of its excellence ; and the result was
the most satisfactory demonstration of its
utility.

The instrument is constructed, as usual,
-with a glass cylinder surmounted by a wooden
or metal cap. The insulation is made to de-
pend on a glass tube of four inches long, and
one-fourth of an inch internal diameter, covered
both on the inside and outside with sealing-
wax, and having a^ brass wire of ,a sixteenth or

380 K£W SYST£M OF INSULATION^.

twelfth of an inch thick, and five inches long,
pass through its axis so as to be perfectly free
.from contact with any part of the tube, in the
middle of which it is fixed by a plug of silk,
.which keeps it concentric with the internal dia-
meter of the. tube. See fig. 33- A is a brass cap
screwed upon the upper part of this wire; it
serves to liaiit the atmosphere from free con-
tact with the outside of the tube, and at the
same time defends its inside from dust. To the
lower part of the wire the gold leaves are fas-
.tened. The glass tube passes through the centre
of the usual cap of the electrometer, and is
cemented in it at about the middle of its length,
as may be seen by the dotted lines which repre-
sent this cap. When this construction is con-
sidered, it will be evident that the insulation of
the wire, and consequently of the gold leaves,
will be preserved until the inside as well as the
outside o^ t\iG glass tube is coated with moisture;
.but so effectually does the arrangement pre-
clude this, that some of these electrometers that
were constructed in 18iO, and have never yet
been warmed or wiped, have still apparently
the same insulating power as at first. The in-
strument is represented complete by figure 1.

NEW SYSTEM OF INSULATION. '281

Had this simple arrangement been found
insufficient, it was my intention to lengthen
the narrow channel, and thus increase the se-
curity of the insulator; for this might easily

- be effected to almost any extent, by enclosing
a series of open tubes one within another, and
securing each in its place by a plug of silk,
touching the adjoining tube in one point only.
In this way, by multiplying the tubes the most
perfect possible insulation may be obtained.

For the insulator of a vertical atmospheri-
cal apparatus, a stick of glass, ten inches long
and one inch diameter, coated with sealing-wax,
may be capped with brass at each extremity.

•Each cap is to be furnished with a screw to re-
ceive the lid of a cylindrical tin funnel. There
are to be two such funnels, one screwed at each
end of the insulating pillar ; they may be about
eight inches long, and one smaller than the other,
in such proportion that the circumference of
the stick of glass and the two funnels may form
a series of concentric circles, distant from each
other about a quarter of an inch. The appara-
tus is represented by Fig. 34, the funnels being
delineated by dotted lines. It is evident that,
in this apparatus, the vapour must first traverse

.'S82 NEW BTSTBH OF lASUlATIOK.

the space between the outeir and inner funnels,
and then the interval between the inner funnel
and the stick of glass, before the insulation can
be destroyed; and this space may be lengthened
to any extent by increasing the number of con-
centric funnels. This arrangement is very
simple and durable, and though the limit of its
insulation is the distance of the funnels, that is
a quarter of an inch; this will be found suf-
ficient for the most essential observations oi\,
the atmosphere, and the higher intensities may
be obtained if desired by prolonging the insu-
lator to some inches below the cap of the lower
funnel, as shewn in the figure; or by making
this lower and internal funnel of a glass tube
covered with sealing-wax.

If an apparatus of this description be used
to insulate the horizontal wire, the open end of
the larger funnel should have a circular tin plate
of nearly twice its di(imeter placed opposite to
it at a short distance, to prevent the intrusion
of driving rain or snow.* Or, what might per-
haps prove more effectual, it may be placed
within a sort of pigeon house, having a hole in
its side for the wire to pass through.

* Sec Figure 35.

jeSW ATMOtPHEMCAX APFABATUS.^ £83

This method of insulation is applicable to
almost all the varieties of an electrical appa*
ratus : my present limits will not allow a detailed
istatement of its modifications, but the ingenious
electrician will not find it difficult either to com-
prehend or employ them ; and he who does this
will not fail to acknowledge and appreciate their
value.

An exploring wire for atmospherical elec-
tricity has been insulated nearly agreeable to
this plan by a very assiduous and promising
electrician, R Ronalds, Esq. of Hammersmith.
The apparatus was erected in a field near Highr
bury Terrace, Islington, and continued ia con-
stant activity for several months : the insulation
was tolerably well preserved, but not uniformly
BO ; this he attributes, in part, to the hasty and
probably imperfect construction of the appar
fatus, and partly to the insufficiency of the most
pferfect insulators, when the stratuni of air be-
tween the wire and the ground is so moist as to
become a conductor of electricity, I commu-
nicated to this intelligent friend a plan of the
Chevalier Landriani, to mark the diurnal mutar
tions of atmospherical electricity, by an insur
kted wire, connected with the conductor, and

tZ84 K£W ATMOSPHERrCAt ArYARATUS.

carried round over a resinous siirfkce by means
of the index of a dial ; powders being afterwards
projected on the resinous plate would nciark, by
the figures they assumed, the intensity and
quality of the electricity that bad prevailed
during the different hours of the day. Mr. Ifto-
nalds proposes to substitute for the resinous
plate a series of electrometers, constructed 'on
my principle of insulation : a soft wire proceed-
ing from the atmospherical conductor being
connected with the index of an insulated dial,
is to be so arranged that it will touch in suc-
cession the cap of each electrometer. These
being perfectly insulated, will retain the elec-
tricity communicated to them, and being ad-
justed for separate hours, or other divisions of
time, the various electricity of each period of a
day, or any longer interval may be ascertained
by one observation. This method may be rea-
dily put in practice ; it will be very useful to
register the changes (if any) that occur during
the night, and promises to afford a tolerably
accurate indication at any required time of the
state of atmospherical electricity during th^
absence of the observer.

sa5

• CHAP. IV.

/ • « • •

J *

(%nntrhn of Ekctricittf with Medicine^ 'and with

Natural History.

\ ut numerous extraprdinary properties of this-
surprizing ag^nt, occasioned the application of
its powers at a very early period to various or-
ganized bodies; and the results observed, or
imagined, gave rise to a variety of fanciful
opinions, which are now referred to but as mo-
numents of credulity and imposture.

The Abb6 NoUet is said to have made the
first experiments of importance on this subject^
and they do not appear to have been extended
or repeated with greater accuracy. From his
results it may be deduced; 1st. that the con-
version of evaporable fluids into vapour is pro-
moted by electrifying them ; Sd. that the mo-
tion of any fluid through a capillary tube is ac^
celerated by electricity, and that the accelera-
tion is comparatively greater the smaller the
capillary tube ; 3d. that the motion of any fluid
through a tube of moderate size is iK>t 3en8ibly

286 MEDICAL BiEtTRlCITT.

affected by electricity, neither is the circular
tion of the blood promoted or retarded there*
by ;* 4th. the insensible perspiration of aniroali
is increased during the time they are electri-
fied, and the same may be observed of v^*^
tables.

These remarkable facts, (and such they really
a{^>ear,) render it highly probable that the ^jec*
trie fluid may be active in the production of
many phenomena of nature, that exhibit not
the slightest trace of its usual effects : the sup-
position that electricity is connected :«rith anir
xs^aA and vegetable life, has been derived almost
wholly from their evidence, and its applicatton
as a medical agent, if proposed on rational prin-
ciples, was in all probability derived from the
same cause.

* This is confirmed by the experiments of Mr. Cavallo, and
the more recent and extensive trials of Dr. Van Marum and Mr.
CuthBertson, with the large machine at Harlem j but Mr. Part-
ington^ whose experience as a medical electrician is considerable,
assured Mr. Cavallo, that in a diseased state of the body, an
evident acceleration of the pulse is often observed to result from
the ppplication of electricity. Mr. Carpue states, that having
cyencd a vein from which the blood did not readily flow, be
electrified the patient, and the blood then streamed forth freely.

UEDICAL ELECT&ICIXr. £8?

Soon after the experiments ' of Nolbet^ ac-*
counts were received from Venice and Bologna
of some pretended miraculous effects of elec-*
tricity in medicine. It was asserted, that by
that power, odours, and the medical action of
drugs, might be transmitted through glass ves-»
sels, and iron chains ; and, that to produce the
most remarkable cures, nothing more was re-^
quired than to place some simple drug in the
patient's hand, whilst he was electrified, or to
enclose the medicine in a cylinder or phial, and
transmit its efficacy with the electric fluid to
any required' distance. These assertions were
made with the decisive language of experience,,
and were apparently supported by respectable
testimony ; they were investigated with great
care by the Abb6 Nollet, who was at the ex-
pense of a journey to Italy for that express pur-»
pose ; they were also examined by several mem«»
bers of the Royal Society, and by Dr. Bianchini
ef Venice. The result of these inquiries deci-»
sively proved that the whole of Uiese pretended
miracles were artful fabrications, entirely un*
supported by experiments, and invented for tho
deception of the credulous, and the burthen and
c^isgrace of science.

9188 HBDICAL BLECTRICITT.

Too many instances have since occurred of
similar absurd pretensions to the cure of diseases
by the influence of imaginary natural powers*
An atmosphere charged with electricity has bieen
proposed as the vehicle of strength and vigour;
and the motion of a pointed piece of metal has
been represejitedas a panacea! To dwell on such
mummery would be an undeserved attention to.
that empiricism, which should be forgotten, or
despised.

The scientific application of electricity to
medicine, has made le$s progress than the sue-*
cess which has attended it might have been
justly expected to produce. It appears from
almost every trial of its power hitherto made,
that under judicious management its application
can do no harm, and that in many of the most
distressing disorders it has frequently been of
considerable service. These are powerful re-
commendations, and when it is added, that it
is an external, and by no means painful re-
medy ; and that it may be applied immediately
to the affected limb without interfering with
any other part, its advantages must appear to
be considerable.

My own experience, although comparatively

SfSDICAL ELECTHICITV. f 89

limited, sufficiently warrants the preceding opi*
nion; even in those 'case& which I have con*
sidered as unsuccessful, some relief has usually
l>een obtained, and it is probable that more con?
tinued attention than I have had the opportu-
nity to bestow, would have been followed by
more perfect results.

The machine employed for medical purposes
should have sufficient power to furnish b, con-
stant stream of strong sparks, for in many cases
an application of that kind is essential. If it is
a plate machine, the diameter of the plate
should not be less than from eighteen inches to
two feet ; if it is a cylinder, the diameter may
be from eight to fourteen inches.

The auxiliary apparatus is very simple ; the
most essential are, 1st. A jar fitted up with
Lane's electrometer,* by which shocks may be
given of any required force. Sd. A pair of di*^
T'ectors, each consisting of a glass handle, sur^
mounted by a brass cap with a wire of a few
inches in length, having a ball screwed on ita
extremity; this ball may be occasionally un-
screwed and a wooden point substituted for it..
When shocks are passed by the aid of these di^n

* Figure 22»
V

fi90 JIKDICAL £LBCTRICITr«

rectors, they are applied at the opposite extre^
mities of the part through which the charge is
to pass, and being respectively connected by
conducting wires, the one with the outside of
the jar, and the other with the receiving ball
af Lane's electrometer previously placed at the
required distance, the jar may be set to the mat
chine, which is then put in motion until any
required number of shocks.has been given.

The insulated director is also employed to
give sparks, being held by its glass handle, and
its ball previously connected with the conductor
by a flexible wire being brought near the pa-
tient, or rubbed lightly over a piece of flannel
or woollen cloth laid on the affected part. When
the eye or any delicate organ is electrified, the
ball of the insulated director is unscrewed and
the wooden point applied, at the distance of
about half an inch from the part The stream
of electrified air which passes from the point
under such circumstances produces rather a
pleasant sensation.

Very excellent flexible conductors for me-»
dical purposes, may be made by sewing a thin
spiral brass wire (such as is used for braces,)
within a thick silk ribbon.

UEDICJk/L ELECTRICITY; S,9l

Sd. An insulated stool, (that is, a stool with
glass legs,) is sometimes employed; it should
be of sufficient size to receive a chair upon it,
with a resting place in front of the chair for the
feet. The patient being placed on the insulated
chair, and connected with the conductor of the
machine, - l>ecomes a part of it, and sparks may
be drawn from any part of the body by a person
who stands, on the ground and presents a brass
ball to it. If the ball is held by a wooden hanr
die, the sensation is less painful than when it is
hdd by metal.

It has been doubted by Mr. Morgan whe*
ther any of the minor applications of electricity
can be at all effectual, for he supposes that the
electric fluid in such c^ses passes only over the
surface of the skin^ and not through the bodyi
But this objection is purely hypothetical, for we
know not in what manner conductors, like- the
human body transmit flight accumulations ofi
the electric fluid ; nor have we any correct idea;
of the principle on which the medical powers of
electricity depend ; but experience has most de-^i
cisively praved, that iti its mildest form, (that
of the current of electrified air from a point,) iU
has frecjuenjly cflfec$ed very remarkable cur«s.

u 2

99i JIEDICAX ELECTRICmr.

The most instructive collection of edses of
the medical application of electricity I have yet
5een, may be consulted in a very neat " Intro-
duction to Electricity and Galvanism/' pub-
lished by Mr. Carpue. The unsuccessful case)
are given, as well as those that were more foN
tunate ; and from a personal knowledge of the
science, talent, and impartiality of Mr, Carpuei
I ani satisfied that a better authority cannot be
referred to.

A brief enumeration of some instances of
disease, in which the application of electricity
has been beneficial, it may be proper to insert.

1st. Contractions. Those only that depend
on the affection of a nerve; and in many of
these it has been employed without effect,
whilst in others of long duration immediate re*
lief has been obtained.

2d. Rigidity, Very frequently relieved, but
usually requiring some perseverance in the ap-
plication, to complete the cure.

3d. Sprains^ Relaxation^ S^c. Electricity may
be applied in all these cases with good effect,
but its application should be deferred until the
inflammation has subsided.

4th. Indolent Tumors. Strong sparks, an4

islight shocks, are often effectual* Tlie most
Bumerous cases are those of scirrhous testicle ;
and there are some instances of the successful
dispersion of scirrhous induration of the breast.
Ganglions have also been removed from the
wrists or feet by the frequent application of
sparks,

5th, Mr. Carpue states, that electricity is a
good preventative against chilbains; and men-^
tions two instances in which they were removed
by the action of electrical sparks.

6th. Epilepsy. In several instances of per-
severing applicatioPi not one successful case
occurred.

* 7th. Deafness. Sparks thrown on the Mas-
toid processj and round the Meatus auditorius
extemus^ and drawn froni the sam^ parts on
the opposite side, usually afford relief; and
about one in five are permanently cured*

8th.. Opacity of the Cornea. This is some-r
times cured by the long continued action of
electricity thrown for ten minutes a day on the
eye by a wooden point. When caused by the
small-pox, it is said to yield most readily. I
have known an instance in which considierable
benefit was received from the application of

f94 ' MEDICAL BLBCTRICITYir

electricity ; but its use could not aftenfrard^ be
discontinued for more than a week at a time,'
Avithout a return of the disorder.

9th. Gutta Serena. The method of electri-r
fying for opacity of the cornea has been sue-"
cessf ul in some instances of gutta serena ; but
there are very many unsuccessful cases.

10th. Amenorrhcea. Cases of suppressed
menstruation are generally relieved by sparks
and slight shocks \, but in retention of the men«#
ses electricity has been tried without success.

1 1 th. Knee Cases, In instances of pain and
swelling of the knee the application of sparky
has been effectual in about one case in ten.

12th. Chronic Rheumatism. Very numerous
are the instances of success; the usual applica-
tion is by sparks, for JO or 15 minutes everyday.
In recent cases, a few days is sometimes suf-
ficient; but in those of long standing, very con*^
siderable perseverance is often required.

13th. Acute Rheumatism. In one case out
of six a cure was effected in about a month by
the application of the electrified current of air
from a point.

14tli. Palsy. Moderate shocks, with sparks
occasionallv, have been successful in about on^

JHEDICAL ILECTRICITr. Q95

case of paralysis in every fourteen that liave
been tried.

St. Vitus s Dance has also been frequently
relieved by electricity. There is indeed scarcely
any disease in which some successful instances
of its application are not recorded; but we are
still in want of a scientific exammation of the
statements that have been made on this sub*
ject.

The nerves appear to be most powerfully
affected by electricity; and the consequences
of an electric charge sent through any part of
the body are generally most conspicuous in
their track. When the charge of a battery is
sent through the head of a bird, its optic nerve
is always injured or destroyed; and a similar
shock, given to a larger animal, is said to pro-
duce a general prostration of strength, with
trembling and depression. I once accidentally
received a considerable charge from a battery
through the head ; the sensation was that of a
violent but universal blow, followed by a tran*
gient loss of memory and indistinctness of vi*-
sion, but no permanent injury ensued.

Mr. Morgan has stated, that if the dia-
phragm be brought into the circuit of a coated

mrface equal to two feet, fully charged, the
luugs make a sudden effort, which is followed
by a loud shout; but that if tlie charge be small,
it never fails to produce a violent fit of laugh*
b.ter; and that even those whose cahnuess and
'■"ioleninity are never disturbed by ludicrous oc-
currences, are rarely able to withstand the comic
powers of electricity. The first eft'ect of a strong
charge on the diaphragm is frequently followed
fay involuntary sighs and tears, and sometimes
by a fainting fit.

If the charge is passed through the spine, it
produces a degree of incapacity in tlie lower
extiemities; so that if a person be standing at
the time, he sometimes drops on his knees, o(
falls prostrate on the floor.

. Great caution is required against the indiit
criminate applicatioti of the shock, which ha»
frequently produced .unpleasant consequeniCe$
when injudiciously applied. Its employment 8#
a .source of amusement in large compaitic*
fihould therefore be conducted with care; na
«vil effects are likely to occur by passing t\^ ■
charge through the arms. ....

Some experiments have been made to ascer-
itain th&supposed influence of electricity in ttkf

NATURAL HISTORT. 297

|>romotion of vegetation and animal life ; but
the results obtained by different inquirers are
very contradictory, and it does not appear that
Any real progress has been made in this investi*
gation, which certainly offers a most interests
ing object for the researches of the electrical
philosophen

One of the most interesting discoveries in
Natural History was that of the electrical power
of certain fishes which had been long known
to possess the faculty of communicating at plea-
sure a tremor or benumbing sensation. Two of
these animals, the Torpedo and the Gymnotus,
are sufficiently well known; and a third the Si*
lurus Electricus, has been described by Brous-
sonet, under the name of Trembleur, in the Hist*
xle I'Academie Royale des Sciences, for 1782.
It is but very imperfectly known.

The Torpedo was noticed by the ancient
writers on natural history, and the analogous
properties of the Gymnotus were observed to-
wards the close of the 17th century; but the
first demonstration of the identity of their
powers with electricity, wasefFccted by Mr. Walsh
in 1772.* The shocks of these animals are conip-

-* See the 63d vol. of the Phil. Traos. jp. 46l^ aod followiog.

i9% £LECTRieAL VI8HE5.

nunicated through all the substances that atf
conductors of electricity , and they are not
transmitted through non-conductors ; and those
of the larger Gymnoti^ when passed through a
minute interruption in a metallic circuit, even
produce a spark.

The dissection of these animals displays t
peculiar organ, consisting of an extensive series
of irregular columns divided by horizontal par-
titions, and exposing very considerable surface:
the interstices appear to contain a fluid, and it
is highly probable that the occasional propuU
sion of this fluid into the interstices, by which
an extensive contact of two dissimilar bodies is
suddenly effected, may be the. source of their
electric power.

The Torpedo is of the order of rays, it in-
habits the Mediterranean, and the North seas ;
they rarely exceed eighteen or twenty pounds
weight, when fully grown ; the rapidity with
which their shocks are communicated is con-
siderable, fifty having been received in a mi-
nute and a half. The shocks appear to depend
on the will of the animal, and their communi-
cation is constantly attended by a depression
of its eyes ; they are said to be four times as

KLECTRICAL FISHES. 399

strong when the fish is insulated and surrounded
by air.

Spallanzani has stated^ that when dyings the
Torpedo communicates its shocks more frc*
quently than usual, but that they are then con*
siderably weaker. He also asserts, that the
young Torpedo can exercise this power the
moment after its birth.

The Gymnotus Electricus, or Surinam Eel,
abounds in the rivers of Surinam and Senegal ;
it resembles a large eel, but is thicker in pro-
portion to its length, and rather of an unpleat
sant appearance. Its usual length is about three
feet ; but it is said they occasionally occur of
ten or twenty feet long, and of sufficient elec-
trie power to occasion the death of a human
being. The electric organ is somewhat more
simple than that of the Torpedo, but of very
considerable extent.*

The nerves connected with the electric
organs of both these animals, are much larger
than those appropriated to any other part of
the body.

The demonstration of the electrical origin

* See Mr. Hunter's account of the Gjmnotns. Phil. Trans.
91^. Liv« And of the Torpedo^ vol. liiiL

SOO EtlCTHlCAL FI8U£$.

of the {>ower of these fishes excited consider^
able attention ; their relation to common eleo
trical phenomena was shewn by Mr. Cavendisb,
in an admirable paper published in the 64th vo-
lume of the philosophical Transactions. We
have now abundance of facts that are strikingly
analogous* The appearance of any definite
quantity of electricity, and its tendency to
(Escape, may be almost infinitely modified by
disposing it on different conductors. A coated
plate of Muscovy talc will appear scarcely elec*
trified when it has received a considerably
charge; and the jars in a battery may be mul-»
tiplied to such extent, that a very trivial spark
from them shall melt a considerable length of
wire. The intensity of the electric power of the
torpedo, and the Gymnotus, is so inconsider*
able^ that it will not penetrate any evident in-
terval of air; but the multiplied surface of their
electrical organs renders the quantity accumu-
lated subservient to the destruction of their
prey-

The actual proof of the active exertion of
electric powers in the animal system afforded by
this discovery, increased the speculations on tlie
probability of its universal agency. Numerous

DALVANISM»^ 301

Hverc the hypotheses formed, and the conjco
tares advanced, but for a considerable period
they excited no particular attention. In the
year 1790, L, Galvani, professor of anatomy at
Bologna, accidentally discovered that the pas*
sage of a small quantity of electricity through
jth^ nerve of a frog that had been recently killed,
had the property of exciting distinct muscular
contractions. He produced the same effect with
?itmospherical electricity ; and afterwards by the
mere contact of two different metals. His dis-
coveries were published in 1791 ^ he proved the
phenomena to be electrical, and says, *' if you
lay bare the sciatic nerve of a frog, and remove
the integuments, then place the nerve on a piece
of zinc, and a muscle on a plate of gold, and
connect these metals by any conducting sub*
stance, contractions are produced ; but if non-t
conductors are used to connect the metalci^
contractions are not excited." The experiment!
of Galvani received considerable attention.;;
they were varied and extended with the greatest
perseverance and address by professor Voltfl^
Dr. Valli, Humbolt, Fowler, Monro^ Robison,
and many others. Many curious facts Fesultedl,
from these researches^ but they are much to<i|

803 GALVANISM*

extensive to detail in this place : an account of
them will be found in the supplement to th«
Encyclopedia Britannica, article Galvanism**

The effects obtained in the experiments of
these naturalists may be illustrated by very
simple experiments. The most important fecti
they establish are, first, that the passage of a
small quantity of electricity through the nerve
or nerves of any animal, occasions a tremulous
motion or contraction of the contiguous muscles^
and sometimes an extension of the limbs. This
effect takes place both in living animals and
such as have been recently killed, and even in
the detached limbs of these last. It is produced
when the transmitted electricity is considerably
too weak to affect the most delicate electrome-
ter, and obtains in all animals for some time
after death ; their susceptibility being greatest
at first, and gradually diminishing as the limbs
itiffen. Animals with cold blood, as frogs and
fishes, retain the power of action after death
longer than others, sometimes for many hours
QT even days.

*. See also Fowler's Essay on Animal Electricity ; Valli's
Experiments on Animal Electricity; and Cavallo's complete
Trcati»e on Electricity, vol. iii. fourth edition.

GALVANISM* 503

Secondly. The same effects that are pro-
duced by the passage of electricity, also result
from the contact of different metals with the
nerves and muscles. If a communication be
formed between any nerve and muscle by a
single metal, contractions are but rarely pro-
duced, and when they appear are very feeble ;
but if two metals are employed in contact with
each other, motion is always obtained, and the
effects are most considerable when the metals
are most essentially different; thus zinc and
gold, or zinc and silver, form a very active
combination.

Thirdly. By the same means that muscular
motion is excited in these trials, some of the
senses are remarkably affected, as will be evi-
dent when the experiment is made on living
animals.

The demonstration of these facts is easily
effected. For the excitation of muscular mo-
tion any small animals may be employed ; the
most convenient are frogs and fishes. Frogs
are peculiarly susceptible. If one of these
animals be employed alive, a piece of tinfoil
may be pasted on its back, and the frog being
then placed on a plate of zinc, spasmodic con*

904 j0ALVANISir>

vulsions wilt be produced whenever a commu*
nication is made by a wire between the zinc
and the tinfoil. This experiment will succeed
either in the open air or under water.

Small flounders, which may be usually ob«
taincd alive at the fishmongers, are also con«
venient for these experiments. The flounder it
to be placed in a dish upon a slip of zinc, a shiU
ling is to be placed upon its back, and when«
ever the zinc and the shilling are brought into
metallic communication by means of a wir^
strong muscular contractions are produced.

The smallest charge from a Leyden phial,
(^ven such as will not produce a spark), when
passed through a frog that has been recently
killed, will produce muscular motion in it.

The most convenient preparation of the
limbs of a frog is obtained by separating the
head and upper extremities from the rest of the
bodj', and removing the skin and the contents
of the abdomen from the lower extremity; the
crural nerves may then be distinctly seen, and
the spine may be separated below their inser-
tion into it, and will then remain attached to
the legs by the nerves only. All the super*
fluous part of the spine is to be cut off, and

-GALVANISM. 305-

the small piece that remains attached to the
n€rve is to be wrapped round with tinfoil. With
this preparation various experiments may be
made ; the following are as illustrative as any.

Place two small glasses full of water near
each other with the legs of the frog in one and
the spine coated with tinfoil in the other; con-
nect the two glasses by a silver wire, the legs
will move, and sometimes so powerfully as to
quit the glass.

Hold the prepared frog by one leg, the other
hanging down with the coated piece of spine in
contact with it. Interpose a piece of silver (a
dollar or other coin,) between the lower thigh
and th^ nerves, so that it may form a commu-
nication on the one side with the thigh, and on
the other with the coated nerves; the hanging
leg will immediately vibrate very powerfully.

Experiments of this kind have been made
on almost every description of animals, from
the grashoppcr to the ox, and the effects of
contraction or motion, occur in all, even in
those that have been considered destitute of
n^rvies. Place a dollar upon a large plate of
zinc, and put a leech upon the dollar ; so long
as it is in contact with the silver only, it wiU

906 GALVANISM.

evince no uneasiness; but if in moving about It
shou)d stretch beyond the silver, and come m,
cpntact with the zinc, it will immediately ret
coil as if from a sudden pang..

Let any one place a piece of silver upaii the
tongue, and a piece of zinc under the tongu^
or vice versa. Whilst the metals remain sepa*
rate no effect is perceived, but if their edges are
brought in contact, a slight shock will b^ f^t^
and a peculiar taste be experienced ; occasion?
ally, also, when the surfaces of the metab are
extensive, a bright flash of light appears to pass
before the eyes. This latter effect may be also
produced by placing one metal between th^ up-
per lip and the gum$, and the other upon the
tongue, and then effecting the contact between
them ; or by covering the bulb of the eye with
tii\foil, placing a silver spoon in the mouthy
and tl>en completing a metallic communication
between the tinfoil and the spoon*

These eflFects, produced by the contact df
dissimikir metals evince the excitatioa of some
power by that means, and destroy the hypo*
thesis proposed by Galvani to account for tbr
muscular contractions he had produced.

Galvani supposed, that different parts of an

galvanism:. 307

aninial are naturally or by some p.rocesi^ of na-
ture in opposite states of electricity, tod that
the contractions are produced by effecting a'
metallic communication between them. Pro-
fessor Volta opposed this statement, and shewed
that the effect depended on the contact of dis-
similar bodies, and not upon a communication
between different parts of the animal. He de-
monstrated, that contractions might be. excited
in either part singly, by the application of two
different metals or other very dissimilar sub-
stances, and accounted for the phenomena, by
assigning a principle of electro-motion, (or
power of producing a circulation of electricity,)
to any circle formed by three bodies of different
conducting powers. Thus zinc, silver, and the
moisture of the animal are three bodies of dif-
ferent conductilig powers, and they produce in
thSese experiments the same effect as artificial
electricity. He found also, that the effects were
produced by a single metal and two different
fluids, as well as by a single fluid and two dif-
ferent metals, and thus accounted for the effect
obtained by a single metal when connected with
opt>osite parts of an animal.

Alkaline sulphurets,' (fiver of sulphur,) and

X 2

308 GALVANISM.

silver, he found as effectual as zinc and silver/
and he demoiistrated, that either of these. com*
binations must form a circle with the animal
before they can act upon it. A demonstraticm
of this fact is easily obtained. Place a cup of
silver filled with water on a plate of zinc stand->
ing upon a table, and touch the water with the
tip of the tongue ; no particular sensation will
be felt, for the body does not then form a circle
with the metals. Moisten the hands, and grasp
the plate of ainc with th^m, whilst the tongue, is
brought to touch the water; a peculiar sensa-.
tion, and a saline taste will be immediately ex-
perienced ; for the body then forms a commu-
nication between the opposite surfaces of the
associated metals ; which is the condition esta-
blished by the experiments of Volta.

The peculiar action exerted by combinations
of this kind appears to be instrumental in the
production of some effects which have been
often observed, but were inexplicable before
the discovery of these facts.

It has been often noticed, by those who
drink porter, that that fluid has a materially
different flavour when drank out of a pewter
pot, thai^ when drank from a vessel of glass or

GALVANISM. SQ9

earthen ware. In this case the moisture of the
lips and the porter, are two different fluids be-
tween which a metallic connexion is formed by
the pewter of the pot, and this it has been seen
is a proper voltaic circle. Professor Robison
has asserted, that even the flavour of a pinch of
snuff is affected by keeping it in a box of tinned
iron, from the surface of which a part of the tin
has been worn by long use.

The sheathing of ships cannot be securely
fastened by iron bolts ; for the copper sheath-
ing, the iron bolts, and the sea-water, form a
Voltaic combination ; and the metals are soon
corroded at their juncture : copper bolts are
now therefore generally employed.

Vessels that are soldered, tarnish isoonest at
the seams, for there two metals form a voltaic
chrcuit with the water of the atmosphere.

On the same principle, the Etruscan inscrip-
tions engraved upon pure lead are preserved to
the present time, whilst medals of mixed metals
of a much more recent date are much corroded.
There are many other circumstances of a simi-
lar nature, which may be easily comprehended
when attentively coudidered and compared with
th^se.

SIO GALVANISM*

Volta supposed that the faculty of forming
these combinations depended on the differei^
conducting powers of the associated bodies, aad
he divided them into classes, according to their
fitness for the production of these effects.-^
There are two principal classes ; 1st. Dry aad
perfect conductors, ' as metals and charcoal:
fid. Imperfect conductors, as fluids and fibrous
solids, which derive their conducting power
from the fluids they contain.

A proper voltaic combination consists of
three bodies taken from these two classes^ and
their energies are greater in proportion as they
differ from each other more considerably. >

When two perfect conductors are combined
with one imperfect conductor, (as silver and
zinc with water,) the combination is said to be
of the first order. When two imperfect con-^
ductors are combined with one perfect conduc-
tor, (as silver with alkaline sulphuret, and water
or acids,) the combination is said to be of the
second order.

Sir Humphrey Davy has constructed the
following tables, expressive of some simple
combinations of each kind.

6ALTAXISM.

311

FIRST ORDEU.

"Most oiidable
Substances.

Less oxidable Substances.

Oxydating Fluids.

Zinc

Iron

With gold, charcoal, sil-
ver, copper, tin, iron
mercury.

. . • • ffold, charcoal, sil-

•

Solutions of nitric acid
in water, of muriatic

Tin

ver, copper, tin.
.... sold, silver, char-

acid, of suipbunc acid,

/ &c. Water holding

in solution oxygen.

Lead

coal.
• • . • fifold. silver. • • . .

atmospheric aur, &c.

Copper

.... srold. silver

C Solution of nitrate of
3 silver and mercury.

^K I'f*'* • • • • •

Silver

. . . . gold , .

j Nitric acid, acetous
(, acid.

. . Nitric acid.

SECOND ORDER.

Perfect Con-
tactors.

Imperfect Conductors.

Charcoal • . .
Copper ....

Silver

Lead

Tin

Iron

Zinc

Solutions of alkaline hy-
dro-sulphnrets, capable
of acting on the first
three metals, but not on
the last.

Solutions of nitrous acid,
chlorine, muriatic acid,
&c. capable of actiqg
on all the metals.

These combinations are more or less power-
ful, nearly in the order of their arrafigetnent,

the most j^ctive occupying the top of the co*
lums.

Some difficulty attends the demonstration
of the electrometrical effects which, agreeable
to the supposition of Volta, should take place
with these combinations. That excellent elec-
trician succeeded in producing them by the dd
of the condenser, which ha,s been already de-
scribed as his invention. He proved, that when
two metals are employed, the humid or. imper-
fect conductor combined with them has but a
very trivial share in the production of Galvanic
effects, the metals themselves being the primary
source of electrical motion. When two fluids
and a metal are employed, one of the fluids only
'•acts with the metal as a motcr of electricity,
the other serving merely to facilitate the effect
by its conducting power, or to convey a cur-^
rent of electricity from one of the motors to
the other.

The endeavours of this celebrated philoso-
pher, to establish these principles, led him to
attempt the arrangement of more powerful
combinations, and the concentration of their
effects ; and in the year 1 800, he communicated
in a letter to Sir Joseph Banks, a description of

.GALVANISHf. 91S

.some arrangements by which these purposes
were attained, , and very . remarkable electrical
powers manifested, ,

This communication must he regarded as
the first dawn of a splendid era in electrical
philosophy, which has been advanced by.it from
the glimmer of twilight to the unclouded bril-
liance of open day. It was hailed by philo-
sophers with an enthusiasm commensurate to
its importance, and employed with a degree
of skill, attention, and assiduity, as unprece-*
dented as the success by which it has beec^
Uttended,

Amongst the most active inquirers may be
enumerated Messrs. Nicholson and Carlisle,
Mr. Cruickshanks, Dr. Henry, Sir H. Davy,
Dr. WoUaston, Messrs. Pepys, Sylvester, Chil-
dren, Ritter, De Luc, PfafF, Thenard, Van Ma-
rum, Biot, Desormes, l^riestley, Bostock,^ Simon,
Wilkinson, Hisinger, Cuthbertson, and Berze-^
lius. The detail of their labours would oc-
cupy volumes; the apportionment of their
praise will be the duty and the pride of future

ages.

The arrangements proposed by Volta are

314 GALVANISM.

named, in just commemoration of their inven-
tor, the Voltaic apparatus ; and the ekctrical
effects they produce are considered by the appel-
lation of Voltaic electricity. This subject
will be detailed systematically in the following
section.

SI5

PART IV.

VOLTAIC £L£CTHIC|[TT.

CHAP. I.

Structure of the Voltaic apparatus, and Nature
of its Electrical Phenomena.

In the enumeration of simple Voltaic combif
nations, it has been stated that those of the first
order consist of two metals and a fluid, and that
Signior Volta supposes the association of the
two metals to be the primary cause of the phe*
nomena they produce.

There are two methods by which the pro*
duction of the opposite states of electricity, by
the contact of dissimilar metals, may be exhi-
bited. The first requires for its action on the
electrometer, the aid of a condenser ; the bc^
cond is more simple, and produces its action
immediately on the electrometer.

The most convenient condenser has been

316 VOLTAIC ELECTRICITY.

already described;* when employed in these
. experiments its insulated plate is to be con-
nected with a very delicate gold leaf electro-
meter.

Experiment I. Procure two circular platesy
about four inches diameter, the one of copper,
and the other of zinc, perfectly clean and
bright; let an . insulating handle be screwed
into the centre of each plate. Hold the plates
by their insulating handles and apply their flat
surfaces together, suffering them to remain in
contact about a second, then separate them and
touch the insulated plate of the condenser with
the copper ; bring the zinc and copper in con-
tact with each other again, then separate them
and touch the condenser with the copper ; re-
peat this operation ten or twelve times, then
remove the uninsulated plate of the condenser,
and the electrometer will diverge with negative
electricity.

Experiment 2, Take off the electricity of the
electrometer, and prepare the condenser as be-
fore. Repeat the contacts of the insulated zinc
and copper plates, and every time they are sepa-
rated touch the condenser with the zinc plate.

* See page 128 3 the instrument is represented by Fig. 19.

VOLTAIC ELECTRICITY. 317

Remove the insulated plate of the condenser,
and the electrometer will diverge with positive
electricity.

Experiment 3. Place a Co[)per plate upon
a table, and a zinc plate upon the copper. Lay
a disk of moistened leather, pasteboard, or cloth
upon the zinc, and connect this moist conductor
by means of a wire with the insulated plate of
the condenser. After about half a minute's
contact the wire may be removed, and the in-
sulated disk of the condenser being connected
with the cap of a condensing electrometer,
(Fig. 20.) its uninsulated disk is to be turned
back : this process transfers the charge of the
large condenser to the cap of the electrometer;
The condenser is now to be removed, and the
smia.ll uninsulated plate of the electrometer be-
ing turned back, its gold leaves will diverge
very slightly with positive electricity. If the
group of copper, zinc, and wetted cloth, be then
reversed, and the contact of the condenser be
established with the copper, on transferring the
electricity of the condenser to the electrometer
its leaves will diverge negatively.^

* These experiments require great care. The electrometer
and the insulated disk of the condenser shoukl be. verjr perfectly

518 VOLTAIC BLECTRICITT.

Ejpperimmt 4. Procure a small sieve of cop^
per, made by drilling a number of small holer
in a concave piece of that metal. Fit an insii^
kting handle to the sieve, and fill it with zinc
filings. Place a broad plate of tin or brass oa
the cap of a gold leaf electrometer. Hold ^the
sieve by its insulating handle, and sift the zinc
filings through it upon the electrometer: thcf
leaves will diverge with positive electricity ;
and if the copper sieve be examined it will be
found negativehf electrified.

Experiment 5. Repeat the preceding ex:pe-
riment, substituting a zinc sieve and copper
.filings, for the copper sieve and zinc filings.
The sieve will be electrified positively^ and the
filings negatively.

Similar experiments may be made with other
metals ; almost any two that are dissimilar become
oppositely electrified when they are brought in

■

contact with each other, and afterwards sepa-
rated. If we enumerate them in the following
order, namely, zinc, iron, tin, lead, copper, sil-
ver, gold, platina, it will be found, on trial, that

insulated, and the manipulations be conducted with great care
aod attention. Even when all these circumstances areobser\ed>
the divergepjce of the electrometer is very slight.

VOLTAIC APPARATUS. S19

any one of these becomes positive by contact
with any ihaXfoikm it^ and negative by contact
with any that precede it.

From these facts it appears probable^ that
when t^^o different metals are associated toge^
ther, their natural attraction for the electric
fluid is altered, and a portion consequently
flows from one to the other. If this be admit*
ted, the manifestation of the opposite states of
electricity, when the metals are separated, is
analogous to the usual effects of elect;ncal ex^
citation.

Copper and zinc are the metals most usually
employed in the construction of Voltaic appa^
ratus, for their effects are greater, in proportion
to the value of the metals, than those of any
other combination. Silver and zinc, or gold
and zinc, would be more powerful^ but not so
much so as to compensate for the increased
expense.

As the effects produced by a single pair of
metals, of any size, are still exceedingly feeble,
attempts were made to combine the action of
several pairs. Professor Robison arranged a
series of zinc and silver plates, about the size
of a shilling, so as to form a rouleau ; and on

3S0 VOLTAIC APPARATUS.

applying his tongue to the edge of this, th^
sensation experienced was more manifest than
by a simple pair of metals; but its power in
other respects did not appear more consider-
able. In this arrangement every zinc plate was
niecessarily between two silver plates, and every
silver plate between two of zinc, with the ex*
ception of the first and last. Now it has been
stated, that the contact of zinc with silver, or
copper, occasions some electric fluid to flow
from either of those metals to it; and, conse^
quently, when a single pair of metals are asso*
elated, the outer surface of the ^zinc appears
positive, and that of the silver or copper nega-
tive. But if both surfaces of the zinc are in
contact with copper or silver, electricity will
flow into it in contrary directions, so that nei-
ther surface can exhibit the effect ; and the
same circumstance occurs, in a contrary order,
when both surfaces of a silver or copper plate
are in contact with zinc. Hence every arrange-
ment of this kind, however numerous the pairs
of metal, will exhibit at its opposite extremities
the powers of a single pair of metals only,

Volta had the penetration to ascertain the
cause of this defect in the rouleau of Professor

VOLTAIC APFARAT0S. 32 1

Robison ; and his ingenuity supplied a ineans of
obviating it. . His experiments on the combi*
nation of two metals with an imperfect con-
ductor, (ai water or saline 6uids,) had taught
him that the electro-motive power of these fluids
interfered but little with the more powerful
energy of the. combined metals; and, that in
feet they acted principally a£ conductors to that
energy. He therefore interposed imperfect con-
ductors of this kind between a series of pairs of
metal, and thus combined their power without
producing a counteracting current ; for th^ zinc
and silver, or zinc and copper, were then \n
contact with each. other at one surface only^
but the conducting communication existed
throughout.

To construct an apparatus of this kind, pro-
cure a number of plates of zinc and copper^ or
zinc and silver, either round or square, of any
size ; and an equal number of pieces of cloth,,
leather, or pasteboard, of the same form, but
rather smaller. Soak these last in salt water,
until they are thoroughly moistened; place a
plate of silver, (or copper,) upon the table, then
upon that placQ a plate of zinc, and on the zinc,
one of the moistened disks ; upon this a second

SSS VOLTAIC APPAEATUf.

series of silver^ zbc, and moistened clodi, (or
pasteboard,) in the same order ; and thus con-
secutivcly until a series of fifty or sixty repeti-
tions have been placed one upon the other.*
Particular care must be taken to place the plates
in regular order ; if in the first group silvtnr i$
placed lowest, zinc next, and then the nxHSt^
ened disk, the same dispos;tion ipust be observed
throughout,

Rvperhnent 6. The Voltaic pile being thits
formed) let th? operator moisten both his haadf
with brine, and grasp a silver spoon in »ch* If
the top of the pile be then touched with one
spoon, and the bottom with the other, a dis-
tinct but slight shock will be felt at every re-
petition of the contacts. This shock resembles
Very nearly the sensation produced by a very
large electrical battery weakly charged; it is
greater in proportion to the number of groups
of which the pile is composed. If the commu-
nication is made with any part of the face near

* To prevent the pieces from falling down, when tlieir niun-
"ber is cooiiderable, it is usual to build them up between three
pillars of varnished glass, placed at equal distances from each
other in a triangle, and cemented into a thick piece of woqdj
which saves as a base for the pile. See Fig^ 36.

VOLTAIC APPARATUS, 323

the eyes, or with a silver spoon held in the
mouth, a vivid Qash of hght is perceived at the
moment of contact, and that whether the eyes
be open or shut.

The power of an apparatus of this kind con-
tinues for some time, but gradually diminishes,
the zinc surfaces becoming oxidated by the ac-
tion of the moisture ; it therefore letjuires to be
taken to pieces and cleaned, an operation that
is very troublesome when the number of plates
is considerable. This inconvenience was dimi-
nished by soldering each pair of zinc and copper
plates together, instead of simply laying them
on each other ; and a further improvement was
devised by Mr. CruickshankSj which consisted
in cementing tlie pairs of plates in regular or-
der, in grooves made in the sides of a mahogany
trough, so as to form water-tight cells between
each pair. These cells being filled with water,
or any conducting fluid, served as a substitute
for the moistened disks used in the pile ; and as
the fluid could be easily poured out, and re-
placed, it required considerably less time to
keep it in proper order. This form of the ap-
paratus, which is called the Voltaic trough, or
battery, has been much used in this country ;
V 2

8S4 VOLTAIC APPARATUS/

at is perhaps, on the whole, the best arrange^
ment hitherto devised, and its construction is
sufficiently simple. . .

The zinc plates are made by casting' thai
metal in an iron or brass mould ; they noay be
about an eighth of an inch thick* The copper
need not exceed twelve or fourteen ounces to
the square foot, and may be soldered to the
zinc at one edge only, the other three being
secured by cement in the trough.

The trough must have as many grooves in
its sides as the number of plates it is intended
to contain, which should be fewer in proportion
to their size, otherwise the apparatus will be
inconvenient from its weight. When the plates
are not more than three inches square, tlieir
number in one trough may be fifty, and the dis-
tance of the grooves from three-eighths to half
an inch. The trough must be made of very dry
wood, and put together with white-lead or ce-
ment. The plates being placed to the lire, the
trough is to be well wanned, and placed hori-
zontally on a level table, with its bottom down-
wards, very hot cement is then to be poured
into it, until the bottom is covered to the depth
of a quarter of au inch. During this process'

VOLTAIC ^AP^ARATUS.' S%5:

the plates M'ril have become tvai*niy aod tbey aror
then to be quickly slided into the grooves andi
puslied firmly to the bottom, so as to be4 tlxem-
selves securely in the cement. In this way thft
plates are very perfectly cemented at the; botr)
tom^ and when this cement is sufficiently cool,,
a slip of thin deal is to be ^lightly nailed on the-:
top edge of one of the sides of the trough^ so as
to overhang: the inner surface about a quarter
of an inch.' The trough being about three-quar'*
ter& of an. inch deeper than the diameter of the
plates, there will be an interval between tfeieift
top edges atid the; deal slip ; and- when the. side,
of the, trough to which the slip is attached ia
laid flat upon- the table, this interval forms a
channel into ^vbich very hot cement is to ba
poured^ and^ it will flow between eac^h; pair of
plates, so aai tO' ceQient one side of all the. cells
perfectly^ As soortjas the channel is quite &ilbof
fluid cement, the Sitrtp of deal is to be. torn.ojff^
and the trough incUn^ isq as. to admttb^^ su«9
perfluous cement to run, out. = When tbis i»
effected and th6 ceipent cool, a slip of deali^ Xo
be nailed on the opposite side, aod the san^e
process purwed with tba]|;. . The- ins trun^ei^li

S38 VOITAIC AVPARATVB*

will tiien be cemented in the most perfect man*
Hen and it may be cleaned off and yamiabed.

I liare been rather particular in this deacrip*
tion, because I have not yet noticed an. account
of this instrument that would enable anyjdM
successfully to attempt its construction. It is
Hapreseuted by fig^ 37.

Volta pix>posed another form of the apps-
ratus> %o which hegaV*e the name of ^ conronne
des'tasaea.^ It consists of a row of wine glasses^
or^'tu^/tibistainingsalt and water^ or amy satine
fluid; into each of these one extremity of a
finietaliio attv consisting of a platei of sine een-^
neoted by a wire with a plate of copper, is
plunged. These arcs are so arranged that the
copper extremity of the. first is in the same glass
with the ainc extremity of the second, the cop-
pisrof the -second with the zinc of the third,
and^sio on in* regular order through the whole
sierley, the ex^eme gkssesfovming the opposite
ektreftiities. Ah apparatus of this fciad occu-
pies ebtwidcrable space; it has been modified
of teti^ by employing troughs of mahogany, di-
vided into ccWs^ by glass partitions ; or troughs
6# W^edgewood ware> with the partitions formed

VOLTAIC A:?PARAiP0^. ^27

of tb6 samfe ift&tefial : the plateii of cdpper and
zinc are soldered together in one point only^
aftd each pair of pla'tes is arranged so as to en-
<;lose a partition between them ; there is con^
se^iiently itf eadh cell a cdpper plate connected
with the zinc of an adjoining cell, and so on in
rtgttlai* succession. The troughs usually con-
tain teh or twelve pairs of plates, and these are
connected togetheir by a slip of baked wood, so
that they n^y be lifted into or out of the cells
together. Sec Fig. 38.

Thid Cbh^ruction has the conv^i^ttce of
admitting the fluid to remain in the trough
whilst the iei^oib m sUspendled >by lifting the
plates ftom t!h^ cells ; the plates are also easily
replaced wheii injured or worn; but both sur-
faces being eiifposed they wear much faster, and
it does^not appeat that any effect commensurate
to the itHci^eftsed surface is ever obtained by
them.

The size of the plaites in the Voltaic appa^
r&tus has been greatly varied ; they have been
constructed as sftoall as half an inch diameter,
aud as large as 2 feet 8 inches by 6 feet The
largest ptotes are useful only for some particu**
lar purpMed, to be het^fter described. The

328 VOLTAIC APPARATUS^

mo9t useful sizes ai*e from 2 inches to 6 inches
square.

. It is obvious that, in all the arrangements^
deacribed, the order of the plates i^) similar, the
copper and zinc alternating regul^jly: with each
other ; hence, if the first plate in any battery
be zinc, the last will be copper; and in all cases
the uncombined surfaces of the copper and the
zinc plates are opposite to each other. That en4
o£ the; battery to which all the copper surfaces
are turned is called the copper extremity ; that^
to which the zinc surfaces incline is called the
zinc extremity.

When many plates are required, the power
of several batteries may be combined together,
by connecting them in proper order, endwise,
with slips of copper : the usual rule is to con-
nect the zinc end of one battery with the copper
end of another, and so on ; for in this way their
plates tend all in one direction : if one battery,
or even a few plates in an extensive series,
should be reversed, a very considerable diminu-
tion of power will be sustained.

The fluid interposed between each pair of
plates is essential to the combination of their
power;, but independent of this, it appears to

VOLTAIC APPARATUS. S&S

have a manifest influence on the effects pro^
duced. A single pair of zinc and copper plates
will not readily affect the common condensiing
electrometer, if they are merely placed in con*
tact with each other, whilst one of them is con-
nected with it; but if a piece of wet cloth i^
placed on the zinc, the electrometer is usually
affected. Again, if a pile or battery of 50 pair*
of plates be put together with water interposed^
the shock will be exceedingly faint; but if the
.water have a considerable portion of salt dis-^
solved in it, the shock will be much stronger^
Hence the introduction of the interposed fluid^
is, with some propriety, called exciting the Vol-
taic battery. >
If the opposite extremities of any excite4
Voltaic battery be accurately examined, they
will be found in different states of electricity ;•
a few plates will manifest this by the aid of the.
condenser ; but with a series of fifty groups, ; a
delicate gold leaf electrometer will be affected
without the aid of the condenser. With one
hundred pairs the divergence of the gold leaves,
\& sufficiently distinct; and with a series of one
tjbK)usand groups, even pith balls are made to
diverge. lu these experiments, a wire proceeds

ddO TLEtttLitAt EFFBCTS OF TUB

hig ftom one extremity of the -battery is to ht
eonttected with the foot of the electrometer,
irbil»t n wire proceeding from the opposite ex*
trenftity is brought to touch its cap. The deo
tricity of the zinc side is always positive j Aat
of the Copper side always negative.

It fs a shigular fact, that though the libock
from the Voltaic battery is increased by brine,
or other fluids that have some chemical action
on the tihc, this is by no means the case witb
its electrical indications. Voltft first ptoved this
by noting the divergence of an electrometcf
produced by his *^ couronne des tasses-/* *hen
charged with water, and then putting a pinch
of salt into each cup, which increased the shock,
but not the effect on the electrometer. I have
made many experiments of this kind on an ex-
tensive scale, employing from one hundred to
one thousand groups, and have found the elec-
trical effects gieatest when the chemical action
has been least. One hundr^ plates were
charged with water, and their effect on the
electrometer noted ; the shock was scarcely ap-
preciable. The water was poured out, and a
Weak solution of muriatic acid introduced ; the
shock i^as greatly increased,^ but the effect on

irOLTAlG APPASATVt. 3S]

tiife dectnimeter ursls evidently dimioished^ I
have varied and extended these experiments
with some care» and have constantly found that
tbe most considerable electrical efFects are prch
dnced when common river water ii employed ;
but the most remarkable circumstance is^ that
id this iray of employing a battery^ the most
distinct evidence may be obtained. of a real in-f
crease of the electrical effects of the Voltaic
aiqDoratus,, by comhiinng with it an elcttrical
battery. If a wire connected wkfa one exttb*
mity of a Voltaic battery charged with, watet,
be brought to the other extremity^ a very faint
spark only wiii be perceived, even if the series
-be 800 or 1000; and if it extend to bot one
hundred, there is rarely any peircepirble effect
But if a wire proceeding from each extretiity,
be lespectiveiy coainected with the inner and
buter suifiace of an electrical battery, of not
less than twelve sx|*aite feet of coated surface^
tUs will be chai ged sa rapidly, that sparks may
bo abtaaned fioni it in rapid succosstoo^. by con*
tttcting a fine ison wire with its outer siufae^,
Wfd successively striking the knob with its
odier extremity: these sparks «ret so stroAg
whe&i the ebavgo is comntinicated by a series

332 VOLTAIC APPARATUS.'

of three or four hiindretl, that the end of the
iron wire is made to scintillate or throw offi
sparks ; aud with a series of one thousand, the
sparks are attended by a distinct crackHn^
noise, and have sufficient power to bum th
metallic leaves, though no such power is poi
sessed by the Voltaic battery itself, when em
ployed with river water-
On one occasion I employed in this '
four hundred pairs of four incJi plates;
affected an electrometer distinctly, but prdi
duced no action on combustible bodies. I tha
proceeded to interpose an electrical battery 1:
tween tbc opposite extremities of the Voltajja
apparatus; it was charged instantly, so as 1
produce scintillating sparks in quick successioaj
and the charge was so incessantly kept up, ■
almost continuous discharges were procured^
and with these phosphorus was inflamed, an<f
fulminating mercury exploded.

The most powerful electrical machine wouldq
not produce an effect of this kind, though by
its long continued action the battery might be
charged to a much higher degree. The quant,
tity of eleclricity put in motion by the Voltaio
apparatus must therefore be very considerablo^J

but from the circumstances; of its production,
* very limited intensity is all that can be ob-
tained.

There is reason to believe tlmt a considerable
portion of the effect produced by a Voltaic com-
bination, is lost by the conducting power of the
bodies with which it is cotmected. When an
ilectrical battery is interposed between its
|>oleSy there is a kind of reservoir for the recep-
tion of the power excited ; this will therefore
accumulate in proportion to the extent of that
reservoir; and it is probably for this reason,,
that more considerable effects are manifested
by a large battery than by a single jar, more
from a large jar than from a small one, and
more from this last, than from the apparatus
itself.

A single jar is always charged by the short-
est possible contact with a Voltaic apparatus
excited with water, to rather more than the in-"
tensity of the apparatus itself, and will conse-
ijuently affect an electrometer somewhat more
distinctly.

The action on tlie electrometer increases in
every Voltaic apparatus with the number of its
pairs of plates, and Volta has stated that' the-

934 VKFVCT8 OF TH« VOLTAIC/ ff^TVp^flir.

increaM i^ e^^actly propoFtioaed to the numlw.
According, to Rittf^r, the effect of the shocki
when water is used, increases with the number
of plates to the extent of five or six hundred ;
it then decreases with higher numbers* When
the exciting fluid i^ brine, the effect increases
with the number, and continues a proportioQata
increase with the most extensive series that
have b^^n hitherto tried, I have obsferved the
same effect with weak acid solutions; th^ shock
from one thousand plates is very sharp and
painful.

The power of a very limited Voltaic batterjf
to produce muscular motion is considerable ; if
two wires be placed in the ears of an ox,* a
sheep, or other animal, soon after its death, and
one of the wires be connected with one extre-
mity of a battery of one hundred plates, whilst
the other wire is brought occasionally in con-
tact with the opposite extremity, at every com-

* The parts with which the wires are brought in contact
must be previously wetted with salt water, the intensity of Vol-
taic electricity being insufficient to overcome the resistance of
the dry cuticle. This circumstance is also necessary to be at-
tended to when Voltaic electricity is applied to the cure of
disease.

£rrSCTll PF 794 VOLXAI0 BATTIET. 335

pletion of the circuit very stroQg muscular ao
tion will be excited, the eyes may be made t<>
move, and the apparent effects of smelling^
chewing, &c. may be produced. With a much
less power the legs of a frog may be made, to
move very powerfully, and even to. leiap to a
considerable distance, and that too an hour
after its death.*

If a battery has been out of use for some
time, it will, when charged with water, evince
but a slight effect in the production of the
shock ; and however extensive it may be, will
scarcely evolve a perceptible spark, but its acr

* The toQgue of an ox wai secured to a tabl^ bf an irpq
skewer; when the power of a Volcaic battery waa applied^ thf
tongue was drawn in with such force as to detslch the skewer
from the table. An entire sheep exhibited motions resembling
the struggles of animals in ao epileptic state, but mora powerful
than the natural aqtions. (" Wilkinsou's £lem6oti4*' yql. iL pt
464.^ It was supposed that the application of the Voltaic ayn
paratus might be serviceable in cases of suspended animation ;
and trials have been actually made on some criminals a short
time afier their execution. Very violeqt muscular action iMU
produced^ but no evidence of returning life. (See Aldini on
Galvanism^ p. IQl.) This power has beei^ also applied to the
cure of disease, and apparently with some success 5 but the cases
bttborto published are scarcely of sofficient Importance to war-i
raut.any ampHficattqq gn tbi^ ml^ct

936 ■' £Ff XGTtf OF tfi£ V4[>LTAie BAtTEftr.

tion on the electrometer^ and its power of charge
ing an electrical battery, will be found consider^
able. If a weak acid solution be now substituted
for the water, the effect of the shock M'ill be
remarkably increased, and a vivid spark may
he obtained; but if the electrometer be applied^
its divergence will be less than in the preceding
instance, and the same may be said of the power
to charge a battery. If the acid be now poured
out, and the troughs washed, and refilled with
water, the force of the shock will remain, or
experience a stight increase ; the spark will be
weaker, and the electrical effects a little
stronger, than with the acid charge : but the
usual effect of the excitation by water will not
be correctly obtained until the apparatus has
been frequently rinsed out and refilled.

From the preceding facts it is evident, that,
for the illustration of the electrical effects of
Ihe Voltaic apparatus, a very extensive series
of plates, excited by water only, will be the
most efficient arrangement. Such an apparatus
has the capital advantage of maintaining its
power without any renewed attention for
months, and probably for years. Its energies
are increased when communicated to an elec-

EFFECTS OF THE VOLTAIC BATTERT. 337

trical battery ; and as the intensity of the charge
it communicates increases with the number of
plates through all the series hitherto tried, there
is little doubt that if 50 or 100,000 plates were
employed, a considerable charge might be con-
stantly kept up in an electrical battery, and
that at no expense but the first cost of the ap-
paratus; which would be sufficient if formed of
plates two inches square.

33S

CHAP. 11.

On the Chemical Effects of the Voltaic

Apparatus.

J/hb chemical phenomena produced by Voltaic
electricity are much more remarkable and ex*
tensive than those that result from the action
of the ordinary electrical apparatus. Many of
them are produced by the most simple combi-
nationsy and are conducted with a degree of
tranquillity analogous to the spontaneous ope-
rations of nature.

Mechanical action is generally evident dur-
ing the operations of common electricity, but
such phenomena are rarely exhibited by the
Voltaic apparatus. Few are the instances in
which the action of the electrical machine i]$
unattended by the appearance of light, yet it
rarely exhibits any unequivocal effect of heat,
but what may be considered as the consequence
of its mechanical agency.

In the Voltaic apparatus, when no light is
evolved, an elevation of temperature may be

iiiCOMPOilTIOK OF'WATii. $9§

usually observed; aiid when, by its intense ac-
tion, there is a copious evolution of light, heat
is produced in a superior degree to that which
results from any other process of art

The chemical agency of the Voltaic appa-
ratus was discovered by Messrs* Carlisle and
Nicholson, during thie first experiments madd
with it in this country;* and within a year
after its introduction, the distinct peculiarities
of its action, in this way, were partly developed
by the activity of the British philosophers.

The decompositions produced by thfe Voltaic
apparatus are eiFected with remarkable precision.
The component parts of the bodies subjected to
its action are separated at some distance from
each other, and no bbsefvable change occurs in
the intermediate space. If two wires of gold
or platina, for instance, are respectively con-
nected M:ith the opposite extremitieii of a Vol-
taic battery, and are then plunged at some dis*
tance from each other into a vesselof watcr^
bubbles of air will soon arise from each, but in
the greatest quantity from that connected with
the copper (or negative) side of the battery. If
these gases are collected, by sufTerihg them to

* See Nfchblson^s Jourtial, 416. voT. ir. p. 179, ^*

Z S

%.%

jiw into two imall tabtM; ^Ued iiffiify apffitfUi tmd
|4|Med over the icspygtive wmf^ljuit fVf^AvaA
mllie greatest^uiiitttgr.wiUbe fb m d^pp, citiffttr

nation to be hy drogepr^ii^ tbait |u;pdacc4>iMM^
smaUest quantity oj^g^j*tbdr«<)^l«4T«q|q^
titles being by ^biitt;^ nearly as-one A9. twvwhidi
ii*tbe ^i|oportii» in whicb«tliey^]ue £Miwi hfr
ezperioient to combine^' jnd fimn. waters; f - VI < '^
• 'If^ instead of gpld or platiQ»-:wireSk'ai^.flM^
tall more readily swceptilde.; 0^4 joi^y.^^!^ br
empU^Fedy tbe- «ke Monected witfa^^thCf »iifa(ftr
pqeitive) eztremit^.of'^he^Mtteigic^'wi)^ ^ pxy-
dated, and evolve-AO;gfs> but. that, c»qiMc4^
with the copper (or negative) sidewiUtContinae
to evolve hydrogen.

Hence it is an established fact, that when^
ever water is made the medium of communi-
cation between two wires proceeding from the
opposite surfaces of a Voltaic battery^ oxygen
is separated by the positive wire, and hydrogen
by the negative.

The demonstration of these facts may be
effected by a very simple apparatus. To evince
the distinct appearance of the gases, two platina
wires may be inserted through, corks in the op^
posite ends of a .glass tube filled with i^aten

DECOMPOSITION OF VATBR^ iW!

On connecting the wires with the opposite
ends of a Voltaic battery of 50 or 100 two-inch
plates, gas will be copiously evolved from each;
and the process will take place^ though with
diminished energy, when the ends of the wifes
are distant from each other even three feet!

When both gases are collected ill one tube,
they may be, reconverted into water by passing
an electrical spark through them. A simple
and elegant arrangement for this experiment is
shewn by Fig 39. It consists of a brass cup,
supported by a thick brass wire, which passes
through its bottom and rises about an inch
within it. This wire serves as a support for a
small receiver, having a platina wire sealed in
its top and projecting withinside near half an
inch. There is a small hole in the top of the
thick brass wire, which receives the end of a
thin wire of platina, whose length extends to
within a twentieth of ah inch of the extremity
of that in the top of the small receiver. • The
apparatus is filled with water, and a connexion
heing then established between one extrcinity
of a Voltaic battery and the bn^ss cup; the cir-
cuit is completed by a wire brought from the
opposite extremity to the platina at ^ the top of

t ■

urines, .a|id riaies to the iof of ^lienvni^tw^nl^
pn|^4g4|fr«piler.mrtil it miaktiiBm^im^
fiflthf iHVir V^S 4(1 :FrW«M.-4^9Prfti)|ff» fini

j«rr.-|i9«^ PM j»fe to 0)0 otbor, ^}ij^4bm m-
fmyinubeMl'AnolymitfriitHatMNi^ "jnie pi

f|D<;Ml)9'>a9f|r^ii.v r-- -• ,; ; - -.; j '■"■

, ThfB fligtt niqiplft amjBggnDfpft^f tQ «eoHoet .%
gafte^ ffparately, is rcfusefiented by Fignre^
A and B are two . separate receivers, formed of
glass tubes three or four inches long, havisg
each a plating .^ire pealed in its top, and exr
tending withi9 it through its whole length.
Thf»e receivers are to be filled with water, and
inverted i^ ^ ^V^9^\ g\^^ half filled with th^jt
llaid. The receivers are then to be connected
;^^!|pectively with the opposite surfaces of a
ypltaic battery. That connected with thf
copper surface will be soon filled with bydrof
gep^ and that i^ttach$4 tp ^h^ . ^inc surf^^ce wil)
}9 thje same tijfn^ be kf^i 6}lfd wit^ pxygeor

&BVIVAL QF H£TA£S» 343

This effect will even take place wbeh each re-
ceiver is placed in a separate glass, provided the
water in the glasses be connected by any moist
fibrous substiance ; as a moistened thread or a
piece of moistened asbestos. This curious fact,
which was first noticed by Sir H» Davy, and has
been extended by him to a most interesting se-
ries of experiments, renders the explanation of
these phenomena very difficult The oxygen
and hydrogen procured, are supposed to result
from the decomposition of the same particle of
water, yet they appear at very distant situa-
tions; at the opposite extremities of a long
tube, or even in separate glasses of water con-
nected by a moistened fibre. At whatever part
of the circuit the decomposition is effected, it
therefore appears certain that one of the gases,
after its separation from the other, mu^t tra-
verse a considerable portion of the fluid in an
invisible state, wliich is lost the moment it
reaches its correspondent wire !

Mr. Cruickshank discovered, that the same
agency which evolves hydrogen from water will
revive metals from their solution in acids, and
produce the separation of alkaline and acid
matter from neutral fluids; these phenomena

S44 flX^iVAL Of H£TAW«

may be illustrated by very simple . experi-
. ments.

Eaferiment 7. Adapt. two corks to a glass
tube of half an inch diameter, and four inches
long, with two wires passing through the corks
to within an inch of each other. Ilil the tn^t'
with, a dilute solution of acetate of lead, ami
place it in the circuit of a Voltaic battery. Me^
tallic lamina, and fibres will almost immediately
appear adhering to the negative wire, and will
soon cover it with a beautiful vegetation of
metallic lead. This experiment may be re-
peated with muriate of tin, or nitrate of silver
with nearly the same result; with tin the ap-
pearance is very beautiful. Many other metals
are revived, but none that I have tried appear
with the same metallic brilliance.

Experiment 8. Bend a small glass tube in
the shape of the letter V, so that it may form
an inverted syphon, and introduce a platina
wire into each of its legs. Fill this syphon
with neutralised infusion of red cabbage :* con-

. • To prepare this, when intended as a delicate test for acid
or alkali, minced leaves of red cabbage are to be infused for a
ihort time in a sufficient quantity of warm distilled water to
cover them j the fluid being strained off, will be foujid to have

TRAKSf Ba OF ACID AKK AL^AI^I. 345

Hect one of the wires with the negative, and the
other with the positive side of a Voltaic bat-
tery; gas. will be evolved, and in a short time
the liquor . in :the positive leg of the syphon
will become red, and that in the negative leg,
green. Reverse the connexions of the wires,
so that the one which was positive may be ren-
dered negative, and that which was negative
become positive. The red liquor: will first re-
sume its original blue colour, and then become
green ; and the green liquor, after returning to
its original blue,, will become.red.

These changes may be repeated, at pleasure
for a considerable time by changing the con^
nexions of the. wires; they-.may be. effected
with very moderate power, even. thirty pairs of
two inch plates.

This determination of alkali to the negative
wire, and acid to the positive wire, was mis-

acquired a fine blue colour^ which becomes green by the contQct
of alkalies, and red by acids; it cannot be preserved for any
length of time. A more usefid infusioa for experiments of
transfer is made by adding to every pint of water, poured on the
minced leaves, a few drops of sulphuric, acid j this exti|9cts a red
infusion, which is more readily preserved, and a portion of it
m^ be neutralized at any time, by cautiously adding a few drops,
of ammonia, until the b)ue. colour appears.

9ii r9MunMfom\£iMVt MUk^wmuA

of. thearhddin by. the ^IMtaio affNuMM^ : >Sir

noM imkfatlgdjle: kiddttejr «iid frioMniBtoilh
skill ; ud liraitertntod! fagr« iMcr «f wMaS^
McCTt p g ri t nc pts, tlwt idiey iroM fiob thsi«fQ«i
ntioit .'of some pMnMar- ftcmior in >titt2¥flitm
appftmtas, by whidi lqrdirogel^ m< hwniw i b h>M»
<Besy alkalicft and mettda^ «n attiMtod tauHi "Mf*
gative (or doppar) auti^KX^ and osyget^raad
addair to ita poaitnre (of ainc) atiffiuie; . iHa
shewed that thii attnractiiMi is ^xaMismklii^wdi
ficient force to separata these aebalimanaileai
their most intimate combinations^ and to mani^
fast their presence when they exist even in the
smallest (Quantities. Thus distilled water ex-
posed to the action of the Voltaic apparatus, in
separate vessels of glass connected by mois-
tened fibres, had been observed to evince the
presence of alkaline and of acid matter; the
new experiments proved that the alkali arose
from a partial decomposition of the glass, and
the acid from the combination of the nascent
oxygen of the water, with the nitrogen of the
atmosphere,* Acid and alkali were indeed ap-

* PhU. IVaos. for 1807, p. 1 to 56.

parent in a slight degree when vessels of pure
gold were employed with common distilled wa-f
ter^ but it was afterwards found that such water
Itlways contains a minute portion of saline mat«
ter; and it was shewn^ that when water is slowly
distilled in a silver stilly and decomposed in
gold vessels, out of the contact of the air, no
trace of either alkali or acid appears.

These eixperiments displayed the importance
of the Voltaic battery as an instrument of analy-
sis ; for the elements of almost all the bodies
subjected to its action, were separated and col*
lected at the wires connected with its opposite
surfaces.

Very numerous experiments were made on
this subject ; the apparatus employed consisted
usually of two cups, sometimes of glass, but
more frequently when great accuracy was re-
quired, of agate, or gold ; the cups were con-
nected together by a few fibi^s of moistened
asbestos,'* and respectively connected with the
opposite surfaces of a Voltaic battery. If a
portion of any saline compound was placed in
each cup, and the action of the battery con-

* For ordinary experiments moistened cotton may be sub-
sibvted fiu: asbeitQs.

led for a sufficient time, all the alkaline
atter was collected in the negative cup, and
the acid matter in tlie positive. Thus, when
the common Glaubers salt, which consists of
siilpliunc acid and soda, is placed in solution in
the apparatus, after a few hours, the positive
cup will be found to contain a solution of sul-
phuric acid, and the negative cup a solution of
Boda. The acid and the alkali must conse-
quently have been transmitted in opposite di-
rections through the moistened fibre, or rather
through the water it contains. Similar experi-
ments may be made with any neutro-saline
compound.

' Any compound solution may be plaiced in
one cup,' and distilled water in the other: '■ If
the cup containifig the solution - be made^Ki^i-
tive the acid will remain in it, and thi^ otiffir
element of the coiApbund be transferHed tb-die
negative cup. ■ If it be made negative, the add
*ill be transferred; and the other dctnent'Will
remain. In this w'ay insoluble "earths, -^revm
metak mfty be transfetYed. ■ .1:

A- very pleasing experiinent of traiisfer nrty
be made with three cups placed side by side in
f line, and connected together- by mobtencd

DSCOiLPOSlrTION AND TRANSFBKr 349

cotton. Sulphate of potash may be placed in
the middle cup, and blue infusion of cabbage in
each of the others. When this apparatus is
placed in the Voltaic circuit, the outer cups
being respectively connected with the opposite
sides of the battery, the sulphuric acid will col-
lect in the positive cup and render its blue in--
fusion red, and potash will deposit in the oppo-
site cup and tinge its blue contents green.

The vessels themselves may be formed of
compact saline bodies, as sulphate of lime, sul*
pljate of barytes, &c. and being filled with dis-
tilled water, and connected by.raoist fibres, their
elements will be gradually separated, and collect
at the opposite wires, but considerable time is
required for this purpose.

So powerful are these means of decomposi*
tion and transfer, that the elements of com-
pound bodies may be conveyed through chemi-
cal menstrua for which they have ' a strong at-
traction. Thus, when three vessels were em-
ployed, sulphate of potash being placed in that
connected with the negative side of the battery,
a solution of ammonia (which has a strong at-
traction for sulphuric acid) in the middle vesr-
sol ;. and ^ water in that connected with the posit

$56 nnnvtMiiftma £»» ¥MM IH ltkL

tiv««iiiiai Tfteiulplta^ add'ipi^ ftdtltm
negfttifo CQp ' thfMqgli dwtfniikniWp MMf iMi*
leoted id tlier positive eup; Bjratvittfoii^of
tliiv cxperinMit^ wk wild bciii^ sftntitiiteu nlP
tiw ammeBia» iid the MlphMie tUf poVftA li^
Kudefed'peiitiTe^ the petatlr ' wtfi '^tnuuuflMleB
1llMrMigh'th<»icid'to''the negatirtf tdiftce^i tlinft
liie same renlt was- obtahiied with- me^
•alts. ItiwledonljidientfaeiMtfermediiiti^
fenned -an iHsolable compoond *wit!i' thetraas*
mitted rabstance; aa in the attttlipt to iiMAttl^
mit bary tea ttetNtgh^sulpfadric achl/ok' titl^lMfe
atid through a aoltttioii of iMryl^ *''-

• ■

The want of chemical actidii hetweea tMt
interposed menstrua and the transmitted bodies,
appears to arise from some peculiar annihilation
of enei^ during the process, which is perhaps
also the cause of the invisible transmission of
gas. For acids may be transmitted through de«
licate vegetable colours without affecting them;
and such is also the case with alkalies. To il-
lustrate this, let three glass cups be arranged as
before described, connected with each other by
moistened cotton, and introduced into the Vol*
taic circuit; the centre cup being filled with
blue infusion of cabbi^, the positive cup

DCCOMl^OSITiaK AND TRANSFER, 851

pure water tinged with the same infusion^ and
the negative cup with sulphate of soda ; a red^
ness will soon be produced in the water of the
positive cup, and it will shortly become strongly
acid. Now, the acid thus collected must have
passed through the middle vessel, but the infu-
sion it contains will experience no change of
colour. By altering the connexions of the outer
cups with the surfaces of the battery, the soda
may be transferred in the same way ; it will be
collected in the tinged water of the negative
cup, and render it green, but no effect will be
apparent in the intermediate infusion through
which it has passed.

The singular phenomena attendant on^hese
experiments, and the constant uniformity of
their results, evince decisively the existence of
some property of Voltaic electricity analogous
to tlie usual operations of chemical attraction.
The opposite surfaces of the battery appear to
have a natural attraction for different elemen-
tary bodies; inflammable substances, alkalies,
earths, and oxides, being constantly determined
to the negative surface ; and oxygen, chlorine,
and acids, to the positive surface : now, if it be
conceived that these phenomena are occasioned

Hi HTjKPmVMf 9M: VUCWM;

plmpd. by ^suppQi^ttg thati tbt^-i^ititnii^tmAf

»jfintit» havo iwitmtdly aoon^raiy. de€l|li«it|i^ ^
ihat^of 1^ surface, .to iwbichi .tfaeypraw vdri t w i '

aitert^ned without wtoftttluft , t3Mt\ idKwiwi^
^nd, electrical attractiofi 4r« idcAtioilt ^^^ or pnisV
doced'b^ the same power acting in. one caaMBft?^
masses^; land in the other on partiolea.'! .TheftilS'
l)ifitrip)a& phUoiopbex^ to Who^e- akiU a^ penr;
ft^verance w^ :are inddited for tlje ampk; dc(f c^ '
Ippem^t of these fac,tv» advanpe4<a:v.ai3ety,i9l
phenomena in support of tbia :opimm» aodidife'
played the same ingenuity and talent in ttjl^
structure of an hypothesis, as in the discovery
of important truths.

If water be interposed between the wires •
from a Voltaic battery, oxygen separates at the.^
positive wire, and hydrogen at the negative.-^
It is tlierefore supposed that oxygen is natu-»
rally negative, and hydrogen naturally positive;
they consequently attrac| each other and form
water, which is neutral, the electricities com-
pensating each other. Now the union of the
oxygen and hydrogen arises from the operatioiv
gf a certain attractive power which has always

HYBOTHB818 OF ELECTRIC ENBIIGY. 353

the same limit ; if, then, a stronger attractive
power be presented, they will separate. The
extremities of the Voltaic battery may be ren-
dered respectively positive and negative to any
•extent by increasing the number of plates.--—
When two wires from the opposite extremities
of such a battery are introduqed into water, if
their electrical states are itiore powerful than
•the natural electricities of its elements, these
virill necessarily separate, and pass to the oppo-
sitely electrified wires. The gases thus attract-
ed to the wires will combine with them, if they
are susceptible of combination ; but if this is not
the case, they will escape. Thus, when the
•wires are formed of a metal that readily com-
bines with oxygen, no gas appears at the posi-
•tive wire, but a quantity of the oxide of the
metal is gradually formed there; and it has
been observed, that when. tellurium is employed
for the negative metallic surface, a sfolid com-
pound of that metal :and hydrogen is. formed.

The phenomena of Voltaic decomposition
appear very simple, when considered in this
way; for the reasoning applied in the case of
water will apply in most other cases, as the
bodies that usually appear at the positive wipe

354 HYPOTREBIS 01^ EtECTfttC XHKIOT.

are, for the most part, either compounds of cncy-
gen, or of analogous properties, and may there-
fore be considered as naturally in the same
electric state (negative): and the substances
that appear at the negative wire are principally
analogous to hydrogen, either from their actual
inflammability, or from their containing a con-
siderable portion of inflammable matter. Hence
they may be considered as having the same
natural electricity (positive).

These natural electric powers may indeed,
in some instances, be exhibited. Touch wilii
an insulated plate of metal some dry crystals
of benzoic, oxalic, or other solid acid, and
apply the plate with which the contact has been
made to the insulated cap of a condensing elec-
trometer; the leaves will open with positive
electricity : hence it is fair to conclude the
acid is negative, and this is agreeable to the
hypothesis. Again, make a similar experiment
with an insulated plate and dry lime, strontites,
or barytes, and they will be found positively
electrical. The same effect would probably be
obtained by the alkalies, did not their rapid
attiaction for moisture interfere with the re-
sult.

fiTP0¥H£SI8 Of XLECTRtC ENEftOT. S55

It may also be observed, that those bodies
which are capable of forming active Voltaic
combinations, are, for the most part, such as are
capable of combining chemically when their
parts have freedom of n^otion : this is obvious
in the arrangements of different nietals; those
which have the highest attraction for oxygen
being positive with respect to all that have a
less attraction for it; this is the case also with
sulphur and the metals, and with acid and alka-
line substances. Thus, in a combination of iron,
copper, and an ajcid solution, the iron is the me-^
tal most affected by chemical action, and it is
positive with respect to the copper; but in a
combination of iron, copper, and an alkaline
tulphuret, the copper is most affected, and it Is
then positive with respect to iron.

Substances that become electrical by con-
tact, lose this power when combined. Copper
amd zinc, by mechanical touch, become elec*
trical, but when fused together evince no elec-
trical signs ; and the same may be said of sul-
phur aud copper, and of zinc and mercury.

An apparent illustration of this idea of
natural electric energies may be obtained by
an experiment priginally contrived by professor

S A S

iichtenbeig, «iid since unpromd imd* ezpl^foied
hy Mr. Gavailo ,i)iid Mr. Bentiett ' * /. .: ' j 7^ ;
Experinmnt ^. Pracunc a resynouA |»li^4Df
18 inches square and iial£an inchtliidL^^Dqar
the knob of a. small Leaden bottle^ 'ciaiged
with negative • electricity, ov«r one port uiE ^
suifac^ and the knob of a similaT botlie^cbnipAi
*vith positive electricity, over anotber ;piHrtnf
its surface. Place the plate vertically, and pior
jedt * towards it from a<q>ring powder pnifl^a
mixture of rM leadand^flowers of. sulphiii; Up
mixed powder will be separated by tfaedificmit
eleiotricities on the surface of the resinous platie
The r^ lead irill adhere to the part touehedfafr
the negative bottle, and the flowers of sul*
phiir to the part touched by the positive
bottle. The figures they fomi are very cuxit
ous, and always of different characters; they
may be diversified in a very pleasing man-^
ner by describing letters or other figuries ^rith
the kndbs of the electrified bottles, or bycomr

* It may be formed bj melting together five pounds of resio,
half a ^KHind bfhte'S'Wax, and two ounces of lam|>-black,-aiM|
pouring the mixture on a board having a rim round n^ edge to
confine the compo^iiion whilst fluid. The blisters that form on
the surface may be removed by frequently heating it before a
flre^ and suffering it to cool after each application of h^t.

•n-

HTFOTHESIS O? SLBCTRIC XNCBOT. S57:

mttoicating electricity to the resinous surface:
by conductors of any required form^
- Ea^periment 1 0. This remarkable phenome- »
non of the separation of mixed powders by the>
action of the contrary electricities, can only-
arise from the actual electric state of those
powders being different. This was first discp^
Tered by Mr. Cavallo, ajid may be tbui» exr
hibited.

Place a broad metallic plate on the cap of
the gold leaf electrometer, and project some,
flowers of sulphur on it, either by an elastic-gum-
bottle, or spring puff, or even by shaking the sul-
phur through a linen hag; the. electrometer will
in a few moments open with negative electri-^
city. Discharge the electrometer, remove the
aulphur, and repeat the experiment with powder
of redhead, which should be made dry previ*
ously ; the leaves of the electrometer will open

with positive electricity.

This last result is stated on the authority of
Mr. Bennett,* but it is a curious fact, that all
the specimens of red lead I have hitherto triedi
produce negative electricity when projected pu
the cap of the electrometer, though they arc

* See his New Experiroeoti in Electricify^ P*^l orttie
Fbilofopbical^raaMcdoiis itx 1781^, vol. lixvii. p. ^.

358 HYPOTHESIS OF BLKCTKIC EVBtoT.

attracted by the negatively electrified surface
in Lichtenberg's Experiment This anomaly
can only be explained by supposing that the
electricity of the red lead is different when it is
projected with another powder. I state this
circumstance, because the separation of the
mixed powder of red lead and sulphur, or red
lead and resin,' has always taken place when I
have projected them on a surface charged with
both states of electricity ; but either red lead,
sulphur, or resin, separately sifted on the elec-^
trometer, has invariably occasioned it to di-
verge negatively.

The general accuracy of Mr. Bennett's ex-
periments, and the coincidence of the greater
number of them, with my own experience, lead
me to believe, that the red lead he employed
really produced the described effect ; and there
is probably a difference in that article resulting
from various methods of manufacture. In
Derbyshire, where Mr. Bennett resided, red lead
is manufactured by the direct oxidation of the
metal; but a considerable proportion of that
sold in London is said to be made from Li-
tharge, and is considered as less pure. This
variety may account for the different results ob-
tained by Mr. Bennett and myself, but it by no

UYPOTHESI6 OF ELECTRIC SN||EliQV,, S59

means explains the singular phenomenon of 91
negatively electrified powder being determined
to a negative surface, when at the same distance
from one that is positive !

The hypothesis of electric energy is sup*
ported by some other analogies. Thus the ocr
casional evolution of heat and light, is common
to both chemical and electrical action ; and the
developement of both chemical and electrical
energy, is facilitated by elevation of temperar
ture. But the most striking fact is, the power
of promoting or suspending the usual operations
of affinity by electric powers. Nitric acid, for
instance, ^cts strongly upon copper; and ac-
<:ording to the hypothesis, this arises from the
copper being positive with regard to acids,* and
experience shews, that by reducing this posi*
tive energy the action is really either lessened
or suspended.

Experiment 11, Into a glass filled with di*
lute nitric acid, introduce a platina wire pro*-
ceeding from the positive side of a Voltaic bat*

* It has been shewn, that the metals are positive and nega-
tive, with regard to each other, nearly in the order of their at-
traction |br oxygen; but they are all posttive with jreq»ect to
acids, and negative with respect to alkalies.

360 HTP0TBE8IS OF ELECTRIC £N£RGT.

tcry. Connect a copper wire with the negative
side of the battery; and complete the circuit
by plunging the extremity of the copper wire
in the nitric acid. There will be very little ac-
tion, for the copper is rendered negative by its
connexion with the battery ; in proof of which,
if it be separated from that connexion, it will
be dissolved rapidly.

By a similar process, two substances that
have no action on each other may be made to
unite; there are many experiments of this kind ;
the following is one of the most simple.

Experiment 12. Fill a glass with a solution
of sulphate of copper, and . connect it with the
positive end of a Voltaic battery. Imqierse a
slip of silver in the solution of copper, and .suf-
fer it to remain any length of time; no effect
will be observed. Connect the silver with the
negative extremity of the battery suffering it
to remain in the solution^ and in a few minutes
it will be coated with copper. ^

In the same way various metals may be re-
vived from their solutions, by others which
have no natural attraction for them, until con-
nected, with the negative side of a Voltaic
circuit.

HYPOTHESIS OF ELECTRIC ENERGY. S6\

The most material objection to the infetence
drawn from these experiments, appears tO;be
the very slight electrical change that is adequate
to the production of such phenomena, for they
occur when a single pair of metals are associated
together, and even when such an association
consists of two slender pieces of wire, yet in
such cases no electricity would be manifested
even by the tnedium of the most delicate in-
struments.

Experiment 13. If a wire of silver and an-
other of zinc, be immersed in a glass containing
dilute muriatic acid, so as to remain at a little
distance from each other, the zinc will give off
hydrogen gas rapidly, but the silver will pro-
duce no eflfect. Bring the ends .of the wires
that are out of the acid in contact, by twisting
them together ; the quantity of hydrogen given
off by the zinc will be diminished, and bubbles
will be evolved from the silver.

If zinc, iron, or copper, are employed in the
same way with gold, in dilute nitric acid, simi^
lar phenomena ensue, but the gas produced is
nitrous gas.

E^rperiment 14. If a wire of iron and an-
other of silver are immersed in a solution of

copper, the iron will soon become coated with
copper, but the silver will remain unchanged.
Bring the wires in contact by twisting their
upper extremities together, and the silver will
be soon covered with a coat of copper.

Similar experiments may be made with n
sine and a silver wire, in solutions of leai^X

' or tin. ■

Dr. Wollaston, to whom we are indebted for
the two last experiments, has proposed the fol-
lowing explanation of them, " We know that
when water is placed in the circuit of conductors

, of electricity, between the tw^o extremities of a
pile, if the power is sufficient to oxidate one of
the wires of communication, thewke <^oaM\^Cit^
with the opposif£ extremity affords . }^drogeii
gas.

" Since the extrication of hydroget^,in this
instance, is seen to depend on el^tit^ty, it is
probable, that in other infit;anc^ .electricity

. may be also requisite for its convefsion.into
gas. It would appear, therefore, that in the
solution of a metal, electricity is evolved during
the action of the acid upon it; and that the
formation of hydrogen ^s, even in that pis^

VAHIOVS GHEIIICAL PBEKOMEKA. S69.

<kpeD^ on a tfansitioh of electricity between
the fluid and the metal.

" We see moreover, in the thirteenth ex-
periment, that the zinc, without contact of any
othdr metal, has the power of decomposing wa*
ter; and we can have no reason to suppose thai
the contact of the silver produces any new
power, but that it serves merely as a conductor of
electricity, and thereby occasions the formation
pf hydrogen gas.

^^ In the fourteenth Experiment also, the iron
by it^lf has the power of precipitating copper,
by means, I presume, of electricity evolved dur-
ing its solution ; and here likewise the silver, by
conducting that electricity, acquires the power
of precipitating the copper in its metallic
state." *

The experiments of this ingenious philoso-
pher, by which the attraction of alkali, and the
precipitation of copper on the surface of silver,
were produced by the influence of negatiinr
electricity excited by the ordinary machine,
have been already recited at page ipi. They
are eonsideved by him as favouring the preced**-
JQg explanation, and proving that oxidation is

* Pbi). Tnms. for l^l, vol. ici. p. 427, «nd follovmg.'

364^ ELICTRO^CHEMICAL PHENOMBKA.

the. primary cause of electric phenomena. To'
me they do not appear to favour any such sup-
position, but rather the contrary; for m the
experiment with two different wires, touching
each other, both produce the same chanical ef-
fect y yet, if they are electrical at all, the one is
positive and the other negative, as all experi-
ments on the association of different metals
prove ; and if two wires, tliat have no chemical
action on the fluid in which they are immersed,^
be rendered respectively positive and. negative,
they are well known to ^xo6\\ct different, chemi^
col effects. , . ;

But it is said the chemical effect produced by
the silver wire, arises from electricity commu-
nicated to it by the zinc ; and, that we have no
reason to suppose that any new power is pro-
duced by the contact of the metals. Now, if this
were the case, the mere conducting communi-
cation of the metals would be the only condi-
^on necessary to give the silver its chemical
power; but the case is widely different; the
communication must be not only conducting^ but
metalliCy and even then no chemical effect will
be produced, unless the extremities of the wires
are immersed in the same liquid, or in two se-

£££CTIlO-CH£M ICAL: PHE NOMEK A. 965

parate portions of liquid that:have a coHduoting
communication with each other.

Ea^periment 15. Place two glassies filled Avith
a solution of copper near each other. Make a
cotnipound arc, by t>^isting. together the end of
a wire of zinc, "with the end of a similar wire of
silver. Connect the two glasses by placing th«
silver leg of the arc in one, and the zinc in the
other. The zinc will immediately attract cop*
per from the solution, but it does not commu-
nicate that power to the silver, though they are
both closely connected. Whilst the compound
arc remains, connect the two glasses by a second
arc, formed of a piece of bent wire of any kind,
except gold, or platina. The silver will be imme-
diately covered with a coating of copper, and will
continue to separate copper from the solution as
long as the disposition >of the apparatus remains
the same. Now, the only difference in the ar-
rangement, that appears to have operated as a
condition to the chemical power of the silver, was
the provision of another conducting commnniG#
tion between the glasses, in addition to that esta-
Jblished by the compound arc ; it therefore ap-
pears that the associated me.t?\s cannot serve as
qenductors to the effect produced ; ^nd indeed if

566 ELECTRO-CHEMICAL PHENOMENA.

they did, it would be scarcely possible any ac-
cumulation of powec could result from the in-
creased number of plates in a Voltaic battery.

This experiment does not display any of the
electric powers of a Voltaic combination ; but
it shews that the association of three different
lubstances is essential to the chemical agency of
such a combination ; and the phenomena will
be found to correspond with some experiments
of Mr. De Luc, on the efficient groups in the
Voltaic pile. This celebrated philosopher found
that no chemical effects were produced by any
Voltaic arrangement, unless two metals were
employed with a liquid between them ; and in
the experiment last described, zinc, silver, and
a metallic solution vere inactive, though .» eon-
tact teith each other, until the Jliiid was made the
medium of conductii^ communkatim ietteeen the
free extremities of the ambined metais.

The experiment last described will succeed,
when the two glasses containing the metallic
TOution, are connected by any moistened con-
ductor; but the chemical power of the silver
wire will be evinced slower, in proportion as
the length of the moistened conductor is in-
creased ; and in all experiments of the kind,

ELieTR(H:a£HlCAL ^HBNOMENA. S67

the less the interval between the extremities of
the compound arc, the more rapid is its action
on the interposed fluid. Hence, in the arrange-
ment of Voltaic apparatus, for the purpose of
chemical decomposition, the ends of the con-
ducting wires are placed at a greater or less disr
tance from each other, in proportion as their
action is required to be more or less intense.

Experiment 1 6. The arrangement of a sim-
pile Voltaic combination, by Mr. Sylvester, in
which this effect is apparent, is represented by
Fig. 41. It consists of a tall glass jar filled with
very dilute muriatic acid. Through a cork
placed in the neck of this jar two wires are in-
serted ; the one a short straight wire of zinc,
the other a long bent wire, of platina, or silver;
by turning this last round, its upper end may
be brought in contact with the zinc, or sepa*
rated from it at pleasure. When they are se-
parate, the zinc only is acted on ; biit as soon as
they are brought in contact, the platina or sil-
ver becomes covered with bubbles of gas, whicil^
appear soonest, and are evolved in the g^atest
quantity from the point S, and the part C;
which are those separated by the least stratum
of fluid from the zinc wire.

d68 £li£CTBO<|lElIICAL \BMf}S!0»MnA.

Notwithstanding this circumstance, the
j power of a simple Voltaic combination con-
tinues to exert its effect when the stratum of
interposed fluid is considerable. If a tube. <^
three feet long be filled with dilute muriatic
acid, and a wire of platina be inserted through
a cork in one of its. extremities, and a wire of
zinc in the other ; on connecting the wires, gas
will be soon evolved from the silver. . If the
tube be bent the effect will take place mote
jslowly; but I have always found it occur. J
took two similar tubes of eighteen inches long,
and connected them by a short piece of flexible
pipe, so as to form together a tube of three feet
in length, with a joint in the middle, which ad*
mitted of its employment either as a straight
tube, or as a syphon with a bend of any re-
quired inclination. In the open ends of this
tube I placed respectively a zinc, and a platina
wire; and found, that whenever their outer
ends were connected by a M^ire, hydrogen wste
soon evolved from the platina; but this effect
took place soonest when the tube was straight,
and hence it appears that the power put in mo-
tion by these combinations, can pass more rea-

ELECTRO-CflfMICAL PHEt^OHSNA< 3^9

dily through any given column of a fluid in a
straight line> than in any other direction. --
It has beeijL seen, that when any metal is in-
solution in the interposed fluid, it is revived by^
the wire which in other cases evolves hydrogen;
and it hats been shewn, by the effect of the sil-
ver and the platina wire, that metals which
have no chemical action on the interposed fluid
alone; may decompose it when combined with
another metal; These facts, though far from
being perfectly understood, may serve to ex-
plain some chemical effects which were before
rather, obscure. If a zinc wire, for instance,
be iriimersed in a solution of lead^ the latter
metal will be revived in the form of a metallic
vegetation, which increases gradually by ad-
dition's to its extremities. The first separation
of the lead is sufficiently intelligible; the acid
in which that metal is dissolved, having a
stronger attraction for the zinc, dissolves a
portioln of it, and deposits on its surface an
equal portion of lead. But the lead,- so revived,
continues to revive more, and to receive ad-
ditions at its remote extremities, whilst it would
have been rather expected these additions would

2 b

570 £fc«e«RIM;M£MICAtfr ^alTCOKlHA.

hsitt beeft mtiit on tbe zinc, and the rtgeUtifW
that had heen first formed protruded faxther
into the tktid by that means. The e^^ntrary re-
sult is now understood to be obtained, by the
Fevived particles of lead forming a Volt^c com*
bination with the zinc and the surrounciKng fluid.
This effect is analogous to that which obtains
in various other instances.

Experiment 17. Spread a few drops of a so*
hrtion of silver upon a pane of glass, and place
a smaH piece of platina and a similar piece el
copper wire upon it, at a little distance fironi
each other. A vegetation will take plai?e about
the copper wire; but no effect >vill be produced
by the platina. Bring the wires in contact with
each other, and the Voltaic combination thus
formed will occasion a beautiful vegetation of
metallic silver to surround the platina wire.

With a solution of tin, and wires of zinc and
platina, similar phenomena occur; but a con-
siderable time elapses, after the contact, before
the vegetation appears round the platina.

TTie immediate contact of the oxidable me-
tal with the metallic solution is not absolutel;f
necessary to the success of these experiments ;
it is only essential that a regular Voltaic circle,^

coni&isting of two difTeretit metals, and a moist
cotiductof, be establiiihed.

Expermtnt 18. Fig, 42 represents a glaSS
tirbe baring a piece of bladder tied Over IM
lower extfemity water tight, atid a cork Inserted
1*1 its ttpprir end with a platina wire pfassing
fhi^ugh it. The tube is to be filled with ftee-J
tate 6f lead, and placed in a small cup of zinc
containing dilute muriatic acid ; when a inetai-
fic communication is formed between this cup^
afid the platina wire, the latter becomes stutldcd
with brilliant crystals of metBllic lead. In this
cdse tlie okidable metal has no connexion with
th€l metallic solution but through the medium of
the ptatina wire on the one side and moist blad-
der oh the other ; but, on the principle of thef
i5th experiment, a somewhat similar result
iWay be obtained when there is no connexion
but through metal.

Ejperifnent 19. Fill two similar glasses, the
tme with a solution of silver, the other with di^
kite muriatic acid; connect them by a compound
wire arc of zinc and platina; the tihc beiti^
pinftged in the muriatic acid, and the plating
in the metallic solution. Immerse a second
ate, formed of a bent silver wire, in the tw6

2b 2

glasses one of its legs heiog'in^sx^i^^B^
time the zinc wire wi]l be :€a^fi^d\^^
imd the pUuina^iH be fonndoovinp^ifRtii^i^
pute crystalsiif metallic silver, (U&pUyiijg^ipy
(leautiful appearance under the micrqil^;]^

Acoorduig to the h jpotlie|i|s iq|;r^l99^
energy^: all the jrhenomeiia of; decottipiQaf^
and tr^nnfer are occasioned by t^rPfp^^
electridties x>f the wires in the mtermptgi €W-
(^1;, and the supposed mtiirajl ieljectoicsAvcv^
l^es of the elements of all cprnpojund hf^^fii^.
Of these energies more wiU be .said jK i ie aft ey , ;
it is sufficient at present to. observe^ thstl; Ilia
characteristic energies of oxygen and hydrogen
have been entirely assumed from the phenomena
of their separation, and appear to have been
considered incapable of demonstration; yet,
from the important and extensive action of
these bodies, I should conceive such a demon-
stration is quite essential, before any reliance
can be placed on the accuracy of the data on
which the hypothesis is said to be founded.
But with regard to the powers of the Voltaic
apparatus, it may be asked, have we any evi-
dence that the opposite electrical state of the
wires in an interrupted circuit is essential* to

M'iriPOtHESIS OF ELECTRIC E^BR^T. S7S

their chemical action? : I believe, when all the
phenoinena afe examined, not the slightest
rational groudd will be found for any such con-
elusion.' As far as common electricity is con-
cerned,' it is obviously iiot so ; for the strongest
artificial eliectrization of the. Voltaic apparatus
lias no -effect- on its chemicd powers. Now it
may be observed, that the electro-motive power
<>f a Voltaic apparatus is too considerable to be
overcome by the action of our electrical ma-
chines ; but where is the proof of this ? All
the usual electrical effects disappear when
the apparatus is electrified by communication
'with an electrical machine, their continuance
can only therefore be inferred from the stability
of the chemical effects, and such an inference
'would, serve but as an argument in a circle.
/ Dr. WoUaston, indeed, succeeded in pro-
ducing chemical changes by the action of an
electrical machine, and with an arrangement
nearly similar to that employed for Voltaic de-
compositions ; different effects being produced
by the wires connected with the opposite con-
ductors. This shews a relation between the
effects of the Voltaic battery and the electrical
'machine, but is no demonstration of the exist-

974 9TP0Ta£SI$ OF ELECTRIC i:i^|(pi^r;«

ence of electric energy ; for th« diffiprfpi^ ^ lepp
trical states of tho wires cau oev^r b«-o<^Lfj|^<-
able, in consequeqce of the coi)duqt|Qg f|Mv4'f
df the fluids interposed l>etwe^A tb^m ; ^ai4 it
1$ consequently a far k3S probably c^we pf |^
plienomena they prodiice, than the f:uFKB( Cif
electric fluid that passes from one wur^ tp thf
other.

In reasoning on these phenomenal it i^ouW
be always recollected, that no eleqtiical e^e^tP
of the Voltaic battery can be observed but
"whien it is in an insulated state; thatil* wb«p
its opposite extremities are unconnected by any
conducting substance. Now the very converse
of this obtains with regard to its chemical
agency, which is never exerted but when a con-
ducting connexion exists between the opposite
ends of the battery; it is therefore, I think,
more rational to conclude, that the phenomena
arise from the circulation of some peculiar
power, (which every experiment indicates,) than
from an imaginary difference in the electrical
state of the wires.

To demonstrate tliat the electrical state of
the wires has no connexion with the chemical
phenomena, Mr. De Luc contrived an apparatus

HYPOTHESIS <)F ^^^qTM<^ f5K«*»Y» 3T5

ia which ^ cofitral wire was placed ^^iilway in
fwater^ between two wirc$ proceeding fronn the
opposite $urfaces of a Voltaic apparmtii^ ; he had
abo a ccmtrivaBce by which the acttial electric
atate of the three wires could at any time be
ascertained. When the end wires were respec*-
tivdy positive and negative the centre wire wan
neutral, yet the opposite extremities of this
MFi?e were at the same iitif^ prodiuciBg oppmtf
4A€fmcal ^e€t9 ; one end separating o^gm^ and
1^ other hydrog^. By a simple variation of
the apparatus the central wire wa3 rendered v^
gative, and thf^ negative <rnd wii-e, neutral.; yet
they eontinued to produce the same chemical
effects as before. Again, the central wire wa$
rendered positive, and the positive end wii^e
4ieuj:rd; and still no change was observed im
43ie chemical effects. The wire coxmected with
4^e copper end of the battery continued to se-
parate hydrogen, whether negative or neutral ;
the wii-e connected with die zinc extremity
luniformly evolved oxygen, whether neutral
or positive ; and the centre wire separated oxy^
gen at one e^iremityy and hydrogen at the other,
equally f when positive^ negative, orneutraL*

« See De Loc's Analjrsis of the (SalyaAie Fib. Kicbdson's
Joanial, vol. xxvi. p. 124.

S76 HYPOTHESIS OF ELECTEXC ENEROT*

I have made .mapy similar experiments on
an extensive scale, with batteries of from 100
to 1000 pairs of plates; which my attention to
the proper means of exciting and • employing
such apparatus has enabled me to do with pre-
cision. The results I have obtained -correspond
very nearly with those recited by Mr. De.Luc^
and I cannot but consider his analysis, as by fax
the most correct and masterly investigation of
the immediate phenomena of the Voitaic apfNi-
ratus, that has been published since the original
demonstration of its properties by Volta, .
- ' When a series of metallic wires are placed
in a line at equal distances from each other, and
are immersed in a fluid ; on connecting the ex-
treme wires with the opposite ends of a Voltaic
battery, every wire produces a different che-
mical effect at each of its extremities ; the ends
that point towards the copper side of the bat-
tery separate oxygen, those that point towards
the zinc extremity, separate hydrogen ; and
these opposite effects occur at each interruption
of the metallic circuit, however nunierpus.
Nov/ it is scarcely possible, that a number of
conducting wires, surrounded by a conducting
fluid, can each have a different electricitv at its

PHENOMENA OF THE VOLTAIC CIRCUIT, 377

opposite ends ; and the obscure notion of an
electrical polarity, (or induction,) which has
been advanced to explain this anomaly, is quite
incompetent; for no series of conductors can
be made polar, or positive and negative at their
oppo&ite ends, but by the temporary derange-
ment of their natural electricity, which can
only obtain when they are iSeparated from each
other by some nonconducting substance ; and no
one can maintain^ thai watery or any saline Jluid,
or acid mixture^ is a nonconductor , either of the
chemical^ or electrical effects of the Voltaic appa^
ratus ; yet the usual chemical changes produced
by Voltaic electricity occur at every interrup-
tion of the metallic circuit in such fluids.

Experiment 20. Procure four glass tubes,
one-fourth of an inch internal diameter, and
fcur or six inches long, bent in the form of the
letter V. Fill these tubes with blue cabbage
liquor, and arrange, them as represented by
•Fig- 43 ; the interrupted metallic circuit being
formed through them by connecting arcs of
platina wire. When the extremities of this ap-
paratus are connected with the opposite wires
of a Voltaic battery, after a short time the li-
quor in that leg of each syphon which inclines

• ^ ri *^ "I •'

■ 9 * 1

fM tkose i^t w^ n^ -eowirwtH^itoi gHWfW sr!
or Th«(tb«09flMooB9ievi»^d<9icii4MitlwilMi|ii^

Jlmt^e-,A«fip cud imeik 9°^ iOo^^\^ffm

mid wires have been fsomettmeoottmeeted witii

the opposite end^ of the biittary» the liquor iu
the two syphons next the copper aide, will be
wholly changed to green, and that in the two
^yphonis next the zinc extremity/ will be wholly
^changed to red. Hence it is probable, that
when the electric fluid passes from metal to
Wftter, it separates oxygen or acid ; and wheu
it passes from water to metal, it separates hy-
drogen^ alkali, or inflammable matter.

The most difficult feature of all the Voltaic
^QOmpositioDS, is the invisible form, in which
ilhfi separated elements of various compcHind^

appear tp traver^ the fluid, and arrange them-
selves at the <^ppo«ite wires. The pi^ygen and
hydrogea ?^bat appear in $oroe of our experi-
ments ^t the distance of three feet from each
other^ are necessarily supposed to result from
the ^fime particle of water ; and if thi& he situ-
ated at either wire, one of its element^, (either
the oxygen or hydrogen,) must pass through
the whole length of the tube to reach the other,
and that in an invisible state, for the gases are
separated at the opposite extremities without
any apparent alteration of the interposed fluid.
.On the hypothesis of electric energy, the by-
xlrogen is said to be attracted by the negative
wife, because it is naturally positive ; and the
oxygen by the positive wire, because it is natu-
rally negative ; this does not explain how the
same particle of water can have its elements li-
berated at ^ great a distance from each other;
and to account for thU fact, according to that
hypothesis, it is necessary to supj>Qse that the par^
tides of water between the wires are arranged
with their eleipents in Ju^ta-position, UHe two
parallel rows of beads, the one of hydrogen, the
other of oxygen ; as the decomposition goips on
these are supposed to slide past each other, so

580 PHENONENA OF THE

that each particle of oxygen comes succeiisivcly
in contact with different particles of hydrogen.
In other words, an atom of hydrogen escapes at
the negative wire, and at the same moment an
atom of oxygen is attracted to the positive;
the number of atoms of oxygen and hydrogen
between the wires are therefore still commen-
surate to each other, and have only changed
their places.*

To me this supposition appears to increase
the difficulty, for it infers a series of decompo-
sitions, and recompositions, of which we have
no proof; and yet it does not seem probable
that such phenomena could occur, without pro-
ducing some apparent motion, or change in the
-interposed fluid. Besides, it cannot operate
when the last particles of a saline compound
are separated, and arrange themselves at the re-
•mote wires, or even in separate vessels; for,
towards the conclusion of such an experiment,
it is obvious no parallel rows of particles can
^xist.
* Dr. Bostock has proposed an explanation, on

* See Dr. Heniy on the Theories of Galvanic Electricity.
Manchester Memoirs^ vol. ii. New Scries^ p. 293 > or Nichol-
ion*i Joonal^ toI. xxxT..p. 25g.

TOLTAIC ciacuiT. 381

the supposition that the separation of oxygen
and other bodies at the positive wire, is occa*-
sioned by the union of the electric fluid with
the other element of the compound, with which
it forms, an invisible combination and passes
through the fluid to the negative wire; the
electric fluid being strongly attracted by this
wire^ enters it, and deposits the hydrogen or
other element with which it had previously
combined ; and this then becomes visible. This
opinion is sufficiently ingenious, but it is liable
to various objections.

1st. The attraction of the electric fluid for
one of the elements of certain compound bodies
in preference to their whole mass, and that too
with a force equal to the subversion of their na-
tural affinity, is an assumption perfectly gra-
tuitous, and supported only by the phenomena
it is advanced to explain.

2d. The invisible transmission of ponderable
matter, as a consequence of its combination
with the electric fluid, is purely hypothetical,
and very difficult to conceive; more particularly
when the substance so transmitted is a metal.*

* Dr. Bostbck advanced this opibion some years ago, when
the phenomena were less numerous > he applied it only to ths

KiMW 'fhit any iatiit'jilMABMitx^M^
hklctk ytlt *bmMOi toT ui itf &ny ' ilnpniUts it is CuHr

flthm'^ iiiediwtt'of tohneilAMi btiiw^'tt^
6pttoritc iriirciiB^' tad' uittost w inte ^6st]pcrattt!fit!%

>iT« t6 Oie dtiler. ' *

iikj&litts^ of tiM ftist in wiigfn, Ainl'iutlf an"nion
diameter. Insert in il^ by mdaaH&IP dMdii
pieces of cork, A wcAet <tf ^9me% dtchaiiliich
amd ft lialf, or tteo htehet iott^; ttr iSiftt fb«ti!

ends may be about an inch distant from each
other. Fill the tube with a solution of lead, and
closie its ends with two sound corks, with a wird

transmission of hydrogen. The statement above given diners
tfaen^re its some degr^ fVom his hypothesis ; and bedfs equal
reMtabldnde in princtple to one (Mposed at an eftrty period by
Mr. Cffuiduhftok. See Nicholson's Jo!umal> 4to. vol. it. p. 257,
&0. In the papers of this ingenious chemist, published in the
above volume, it will be seen, that he developed the germe (if
I may be allowed the expression) of the most important facts
tkai faavt beeaaiDce established relative to the driemical agency
^flto y^lfaic fippiratas;

passing through each. liitrodue^ the tube into
Itoe circuit of a Voltai<3 battery, and in a shortj
time that end of each wire, which points to-'
wank lAie negative ^de of the battery^ will b€f
covered with a vegetation of metaUic lead ; th€^
direction of which appears to indicate the pro^
gress of some power through the tube, from th^
f^ositive to t^e negative sidie of the batte]ry« JSee;
Fig. 44.

Sir H. Davy has mentioned an ^perim^nf^
in which a vessel of water, containing a few
globules of mercury, was made the medium of
connection between the oppoi^ite ends of a Vol*'
taic combination of 1000 plates weakly charged?
the mercury was violently agitated, and a pof**
tion of oxide formed, which passed " in a rapid
current from the positive towards the negative
pole." No hydrogen was given off whibt Ihn
charge of the battery was moderate ; btit vrhttt
the action was increased so as to evolve hydWM
gen, the. globules of mercury became rtatibnafy {
as if the same power that had given motioi^ to
the mercury was neutralized by^ of ctinrptoy^d
in, the separation of the hydrogen.*

*• £Icfmentl of Cbemical Phtlosopby, p. lyi*

984 UTPOTHESIS OF ELECTRIC ENERGT.

Whatever be the true qause of the chemical
phenomena of the Voltaic apparatus, its effects
are invariable : at that wire of any combination,
which in an insulated state affects an electro-
meter negatively, hydrogen, inflamniable. mat-
ter, or alkali, are sure to separate when the cirr^
cuit is made through a fluid; and at the op-
posite wire, which in an insulated state affects
the electrometer positively, oxygen or. acid is
as invariably found under similar circumstances.
The regularity of the^e. phenomena has occa-
sioned a classification pf chemical substances
according to their electrical relations, which
has been adopted by Sir H. Davy in his " Ele-
ments of Chemical Philosophy."

The indefatigable Berzclius, who appears to
^aye been the first proposer of this arrangement,
has denominated those substances that con-
stantly separate at the negative wire, " Electro
positive," and those that appear at the positive
wire, " Electro negative," on the supposition
that they are respectively in an opposite state
pf electricity to that of the wire by which they
are separated. This nomenclature appears to
me rather too hypothetical in the present

HYPOTHESIS or EL1ECTRIC ENEnOT. S83f

state of our knowledge. We have no unequU
"vocal demonstration of the existence of what
have been called >' natural electric energies,"
and considerfed as an "essential property of
matter." The different electrical states, obJ-
tained by the contact add separation of difi-
ferent bodies, is certainly no evidence that they
are naturally possessed of inherent electrical
qualities. The operation is analogous to the usual
process of excitation ; and when two substances
exhibit different electricities after such mani^
pulation, the phenomena more probably result
from the change of electrical capacity, induced
by the contact of dissimilar bodies, than from
any natural energies they possess. Besides, by
an accurate performance of these experiments,
I find the results are sometimes inimical to the
hypothesis;* and it may also be observed, that
we have many instances of pure chemical ac-
tion in which no trace of electrical effect is
ever discovered. But it is unnecessary to ex-
tend these objections ; the hypothesis was mo*

* The result of my experiments on this subject will be given
in a snbsequent chapter.

'' •-ft.- " « ^- %

X' '

8f9 - MMnMtiH|iM:flMWVSM.4MMi^^

- «

» i O

'\ t ' '■ **'*,'**.'. « ' . ' r. ^ *

a$7

* -i

CHAP. in.

JEj^iemtve - Agency of the Poltaic Apparatus (U
an Instrument cf Chevtical Analysis^ Its tn*
Jluence in the Evolution of Light and tlie Pro*
duction of Heat^

Xhe uniform action of the Voltaic battery iti
diisuniting the elements of compound bodies^
and determining different specific substancasi
invariably to the wires proceeding from its op-
posite extremities^ offers a most advantageous
and ready means of general analysis ; which has
been already applied with the happiest success,
to the decomposition of an iirteresting class of
chemical substances, and to the discovery of
pew and important agents^

The extensive experiments of Messrs. Hi«
singer and Berzelkis,'^ confirmed by the re^
searches of Sir H. Da^y^f had denwnstrated
the constant separation of oxygen, and com-
pounds in which it prevailed, at the wire pro-

2c 2

DECOMPOSITION OF

ceeding from the zinc surface; and of hydrogen
and other inflamnuble matter, at that connected
with the copper surface : at this latter, alkaii
was also frequently found, and from analogy it
was in consequence concluded, that the alkalies
probably contained a considerable proportion
of some inflammable substance.

This conjecture was confirmed by Sir H.
Davy in 1807: he found that a thin piece of
potash, or soda, slightly moistened by exposure
to the air, and placed between two conductors
of platina, proceeding from the opposite sides
of a powerful Voltaic apparatus, was resolved
into a peculiar metallic substance highly inflam-
mable, which appeared at the negative surface;
and oxygen gas, which was evolved at the po-
sitive surface. By an extensive series of ex-
periments, it was shewn that these bodies are
in reality metallic oxides, and that the propor-
tion of their constituent parts is somewhat dif-
ferent, being in round numbers, for p6tash six
parts of metallic base to one part of oxygen,-
nearly ; or it may be stated, that potash is com<
posed of 86 parts of metal, and 14 of oxygen in
each one hundrpd parts. The proportions in
soda are nearly seven parts metal to two of

THE ALKALIES. 389

oxygen ; or 78 metal and 22 oxygen in ; each
100.*

. The metal obtained from potash, is called
Potassium ; it is lighter than water in the pro-
portion of eight to ten. At common tempera-
tures it is solid, but soft and plastic. At a tem-
perature of 150 it becomes fluid, and evaporates
at a heat rather below redness. In colour it near-
ly resembles silver, but it tarnishes immediately
when exposed in the open air, and can only be
preserved under Naptha.f Its attraction for
oxygen is so powerful, that it will detach that
substance from almost all its combinations; and
the result of this action is its consequent oxida*'
tion and reconversion into potash. If thrown
upon water it immediately inflames, floats upon
the surface, and burns with a mixed flame of
white, red, and violet ; rendering the water in

* For a full accoont of tl^e experiioents on the production
of these metals^ their properties, &c. see the very interesting
paper in the Philosophical Transactions for 1808, p. 1, &c. or
Nicholson's Journal, vol. ilx. p, 29O, &c. ■

f Naptha is a very light and sonietimes colourless oil : it is
found in a state nearly pure io some parts of Persia; but is
usually obtained, for the purpose of experiment, by repeated
distillation in a glass retort from a viscous substance called
petroleum, which may b^ piuch98e4 at the dm^ists.

tvllk'li the experiinent is made alkaline. Simi'
lar plienoincna ensue when it is brought iu con-
tact witli ice. When niod«rately lieated ift'
oxygen gas it inflames and reproduces potasU,
Its action on water is always attended by th^
decomposition of that fluid ; hydrogen is evolvi,
ed, and the oxygen combines with the pota«
Bium to form potash. By measuring the qoan^i
tity of liydrogen separated from water by the
action of a given weight of potassium, the quan-
tity of oxygen that metal combines with ta
form potash may be readily learnt. Each grain
of potassium detaches about 1.06 cubic inch of
hydrogen gas, and consequently combines with
half that quantity qf oxygen. - ■

• The metal obtained from ioda w named
Sodium; it is rather lighter tbui^ater, nearly
83 0,9S48 to 1000. It has the colour of silver;
is leas fusible than potassium, but tarnishes in
air in the same way. It is fluid at the tempe-
rature of 30O»and passes into vapour ^t a strong
red heat. At commoQ temperatures it i» ascift
metal, and a globule of it may be .easily spread
into a thin leaf by the action of a knife. It
decomposes water violently, and float? on its
surface, but does not inflame ; the water^la ren-

TH% ALKALIES. 391

dered alkaline, and when examined is found to
contain pure soda. It acts nearly in the same
manner as potassium, but with less energy on
most substances, and must consequently be pre^
served under naptha. When thrown on the
surface of nitric acid it inflames, and bums
with great brilliance ; it also occasiotially scin^^
tillates when thrown upon hot water. The pro*
portion of oxygen with which it combines to
form soda, may be learnt by noting the quan*
tity of hydrogen evolved from water by a given
Weight of the sodium«

Both these new metallic substances unite
with mercury in various proportions, and form
amalgams which decompose water, but more
slowly than the metals themselves; these amal*
gams act upon all other metals, even platina
and mercury.

The decomposition of the alkalies may, by
care and attention, be effected with a battery, of
fifty pairs of plates of three or four inches
square; but the results are rather uncertain.
Two hundred plates form a very efficient arr
rangement ; they should be excited by a weak
acid mixture, (about one part strong muriatic,
or nitrous acid to thirty parts of water.) A platt

of silver ur platiua being connected with the
negative side of tlie battery, a thin piece of pure
potash or soda is to be placed upon it, and a
platina or silver conductor proceeding from the
positive side of the battery, is to he brought in
contact with the upper surface of the alkali,
which soon fuses at the points of contact ; nie-
taUic globules shortly appear near the negative
surface, and gradually increase in sJze, until a
crust of alkali begins to form on their surface;
at this moment they should be removed by the
point of a knife, and instantly plunged under
I naptha; or if the experiment be merely iuteud-
wed to demonstrate their production, tliey may
be brought in contact with the surface of vrftter
or nitric actd. It sometimes happiens that no
globules appear, but if the contaiCt be- preserved
for some time, and the alkali be afteirwasd: rais-
ed, several will be found imbedded in its under
surface. If the action of the battery be str^g,
it also sometimes happens that the globules in-
flame, and even detonate at the mom^t pf .their
production; it is therefore adviieabl^ nott to
Iwing the eyes too near during the experiment,
or else to cover them with glassesi These ex-
periments always require great care tp. insure

THE ALKALIES^ S9S

their success,, which a trifling variation in. the
powei: of the battery,. purity of the potash, or
moisture of, the atmosphere, may prevent.-—
Soda is rather more difficult to decompose than
^ potash, and therefore requires to be employed
in thinner pieces ; the pieces of potash should
rarely exceed a quarter of an inch in thickness,
»nd those of soda one-eighth of an inch.

^To prevent the loss of the alkaline bases
during their separation, by the powerful action
of the air .upon them, it has been proposed to
effect the deoomposition under naptha: the
moist potash being placed between two plates
of platina in a proper vessel, which is to be
filled with naptha as soon as the contact with
the battery is established ;* in this way the ac-
tion of the air is prevented, but the naptha de-
composes, and. hydrogen and charcoal are libe-
rated, which renders the result less satisfactory
than in the more simple form of the experiment.
The most essential precautions are to preserve
the alkali as dry as is consistent with a suf-
ficient degree of conducting power, and to em-

* An ingenious apparatus for this purpose is described by
Mr. Pepys^ in the 31st volume of the Philosophical Magazine,
page 241.

* I rlfiiii 111 M tllT - I idlai MiliMM^-A^yifci ■ ■*rf i> ^rf^

The plitfib^ %ire, fttftouildiid hy ntemiiy, U
then to be cotmected with the negative end of
a Voltaic battery^ and the circuit completed faj
bringing a platina wire from the positive end^
in contact with the toltition of alkali. Gas will
be evolved from this wire, and die surface of
the mercury will be greatly agitated ; when die
action grows weaker, the mercury may be poured
into a glass of water, and the presence of tiie
alkaline metal will be immediately indicated
by the evolution of a cloud of minute bubbles
of hydrogen gas, which may be collected by
inverting over the mercury a small closed g^lass

T9B ALKALIES, $9$

tube filled with water. This result I have fre-
quently obtained with a battery of thirty pairs
of plates of only two inches square.

The amalgam may be obtained more highly
charged with the alkaline metal by employing
a solid piece of alkali, with a small cavity on its
rarface, in which a globule of mercury is to be
placed* The alkali is to be connected with the
zinc surface of a battery, and the mercury with
the copper surface; the mercury soon becomes
more tenacious, and sometimes is converted
into a soft solid, and in this state, if thrown inta
water, it produces a rapid decomposition.

The strong attraction of the metals of the
alkalies for oxygen, renders them most active
agents of chemical decomposition; by the
strongest Voltaic power they can only be ob-
tained in small quantity ; and for the purpose
of experiment they are now usually procured
by another process first devised by the French
chemUts. A gun-barrel is bent nearly in the
form of the letter S. An iron tube of the ca-
pacity of two cubic inches having a small hole
at the lower extremity, and an iron stopper at
the top, is ground into one end of the gun-
barrel, and a tube of safety is fitted to the

other. The iron tube is to be filled with pure
dry potash, and the bent part of the gun-
barrel nearest to it, with clean iron turnings :
this part of the barrel is to be luted and placed
in a small blast furnace; the iron tube project-
ing out on one side, and the vacant part of the
gun-barrel, with its attached tube of safety,
charged with clean oil, or naptha on the other.
A strong heat is then to be raised in the furnace,
and when the iron turnings have attained an in-
tense white heat, a small furnace is to be ap-
plied to the tube containing the potash, which
being fused thereby, will flow gradually through
the small bole at the bottom of the tube, upon
the iron turnings. The oxygen of the potash
combines with the heated iron, and the potas-
sium, cobdenses in brilliant lamina in.the vacant
part of the gun-barrel, which must be kept cool
by ice, during the process. As potash always
contains water, that is also decomposed, and
hydrogen escapes during the experiment,' from
the tube of safety ; the cessation of this libera-
tion of gas, is the sign for removing the small
furnace from the tube, and the heat being raised
in the blast furnace for a few minutes, as high
iS possible, to expel the last portions of potas-

int ALttALTtS. 39^

slum from the iron, the whole apparatus is suf-
fered to cool. The giin-biarrel is thfen to be cut
at the commieilcfeinent of the part which has
been kept cool, for there the greatest portion
of potassium is usually found ; it must be de-
tached by a chisel in as large pieces as possible;
and introduced quickly into naptha, a portion
of which fluid it is expedient to pour into the
barrel as soon as it is first opened.

This process is attended with some diffi-
culty, but it has been repeated successfully by
many cheniists in this country : a more detailed
account of it may be consulted in thfe 32d vo*
lume of the Philosophical Magazine, pp. 89,
and 9.76.

Another process, by the action of heated
charcoal, has been employed by Curaudau ; it
is described in Nicholson's Journal, vol. xxiv.

p. 37.

The composition of the fixed alkalies was

entirely unknown before these experiments, but
the volatile alkali, or ammonia, had been shewn
to consist of hydrogen and nitrogen, in the
proportion of three of hydrogen to one of ni-
trogen by vohime. Now it is singular, that of
three bodies whose properties are so analogous;

398 METALLIZATIOif OF AMUdNIA«

two should be metallic oxides, and the third a
compound of two gases ; but there are eicperi*
tnents that seem to prove that either «oe or
both of these gases contain a metallic sttbstaB€r»
and that consequently ammonia may be^ lika
the other alkaliesi a metallic oxide !

Messrs. Berzelius and Pontin of StockbdUn^
discovered that when mercury is placed in a
Voltaic circuit with solution of ammooii, the
mercury being connected with the copper ex-
tremity of the battery, and the ammonia with
the zinc, the mercury gradually expands to
four or five times its original volume, and be^
comes a soft solid, nearly of the consistence of
butter, having its metallic characters quite un-
impaired. It is very remarkable, that by this
change it gains only about one-twelve-thou-
sandth part of its weight} yet has its specific
gravity so much diminished, that from being
thirteen or fourteen times heavier than water,
it becomes only three times heavier. By a short
exposure to the atmosphere it regains its ofigi-
nal size and fluidity, absorbing oxygen, and re-
producing ammonia. When thrown into water
a similar effect is produced, the water being de-
composed and hydrogen liberated.

. UETAtLIlATIOK Qt AtlMOttlA. SQI^

These phenomena are very analogous to
those obserred with the fixed alkalies; some
substance combines . with the quicksilveir and
alters its properties materially, without impair^
ing its metallic character; now, according to
all existing analogiesi this substance must l>e a
metal, and this metal in returning to the state
of alkalii absorbs oxygen^ as is seen by its ac-
tion on water* Hence it appears that ammonia
jCK>nsists of oxygen, and a peculiar metal^ which
may be called ammonium ; but its analysis by
otjfier means evinces only the two gases, hydro*
gen, and nitrogen ; the former of these being
the lightest of all gravitating bodies, is most
probably a simple or elementary substance ; and
on such a view, it would seem that nitrogien,
though a gaseous body» is a compound of oxy«
gen^ and a metaL

The amalgam of ammonium, may be formed
moat xeodily fay making a cavity in a moistened
piece of muriate, or carbonate of ammonia, con*
nected with the positive aide of a Voltaic bat*
tery, and inserting in it a globule of mercury
tonnected by a platina wire with the negative
sur&ce ; in a few minutes a soft amalgam' ia
formed; it muat be transferred into water aus

I '

«|0O ^ iwcoMmtxTxoir ortntMMHi;

m to be obibrv^ iiBWt}maigtsihyli»
: Sir Hi Davy ImitAimPfred^'iim^i^

to^'dclcompMe'tomoidafeiiieii'Hri^ it^idljir-tiiift
thd Voltait; battery ; anil if ail aittii]|gMb bPf»
tassitim and^'wareury be 'placed m a cati^'ltt
]noi«teiied muriate :pf aramOBii, it ImniedialMff
JBcreaaes to : rise,' ma4 bdiciAnca ib9re te]i|iataiiift

M sAaaonieof thiisidntaiiciW'eafM'eaf^
aemblfe the alkalies iia*vu1ottii)propertieiiritivla
icohj^ctitred, that die|jr 'alio; i»«e ^te etJaUic «|^
idea; and tbia ccmjecfore luuj ' bdto vpaMly iveft^
fied by the experiments of Messrs. Pontin and
Berzelius, and Sir H. Davy. If a paste be
formed ^dth water, and either barytes, stron-
tites, lime, or magnesia ; and this paste be con-^
nected with the positive side of a Voltaic bat-
tery^ ^nd touched with an iron wire proceeding
from the negative surface, the wire obtains the
ptoj)erty'of decomposing water.

! If aglobule of mercury be placed in a cavity
in the earthy paste, and touched with a wire
proceeding f romt the copper end of the battery,
^e paste being connected with the zinc,) an

DECOMPOSITION OF THE EARTHS. '401

amalgam will be soon formed, which has the
property of decomposing water, and forming
with it a solution of the earth employed. If
this amalgam be introduced into a little tube
made of green glass, and bent in the form of <a,
retort, then filled with the vapour of naptha
and hermetically sealed ; on the application of
heat to the end of the tube containing the amal-
gam, the mercury will distil over and leave the
pure metal of the earth behind. This process
is rather difficult, and requires great care ; Sir
H. Davy has by its means obtained an acquaint*
ance with some of the properties of these me*
tallic bases, but they have never been obtained
in sufficient quantity to admit of a very accu^
rate exa minaticn.

The amalgam from barytes, strontites, and
lime, may be obtained with a battery of from
100 to 200 four-inch plates, in moderate time;
that from magnesia requires a longer continu'r
ance of the action of the battery, and the otheic
earths do not yield to its powers. These metald
are named from the earths of which they appear
to.be the bases, as follows; namely, that from
barytes, barium ; strontites, strontium ; lime,.
..2d

PUESrOMEN'A OF

calcium ; magnesia, magnesium ; alumine, alu-
minum ; silex, silicum, &c.

The decomposition of the alkalies and earths
which had previously resisted very numerous
attempts at analysis, are a monument of the im-
portance of the Voltaic apparatus as an instru-
ment of chemical research ; and a proof of the
ability with which it has heen employed, which
will he regarded with admiration and applause,
as long as science shall continue to be culti*
vated.

The phenomena tliat have been described as
the consequences of Voltaic decomposition ob-
tain in every variety of experiment. Sulphuric
acid introduced into the Voltaic circuit, gives
off oxygen gas, and sulphur is deposited. Pbos-
phoric acid evolves oxygen gas, and phosphorus
combines with the negative wire. Ammonia
separates into hydrogen and nitrogen with i
smail proportion of oxygen. Oils, alcohol, and
•ther, when acted on by a powerful battery de-
posit charcoal, and give off hydrogen, or car-
bonated hydrogen. And Mr. Brande has shewn,
that when animal fluids containing albumen,
are plac^ in the Voltaic circuit, the albumen is
separated in combination with alkali at the ne-

yOLTAIC DECOMPOSITION* ' 405

gative wire^ and in combination with acid af
the positive wire. And, that with a powerful
batteiy, it separates at the negative wire in the
solid form ; and with a less i>ower, in the fluid
form, so that it is probable animal secretion
may depend on some such power.*

The eflFects that have been hitherto de-»
scribed result from the introduction of fluid
bodies into the Voltaic circuit, and are nearly
allied to the usual operations of chemical affi-
nity. I hdve now to notice its action on solid
conductors, inflammable substances, and gases.

When the opposite extremities of a power*
ful Voltaic apparatus are connected by a wire^
at the moment of contact a distinct spark is
perceived, which occurs every time the contact
is alternately broken and renewed. If the con-
tact is made with a wire terminated at the end,
by a piece of well-burnt charcoal, the spark is
considerably more vivid. And if two wires pro-
ceeding from the opposite ends of the battery
are armed with charcoal points^f and brought

* Kiil. Trans, for I8O9. p. 385, Ac.

f Charcoal for this purpose is usually made from box- wood,
cut into pieces of about au inch long, and three-eighths of aii
inch thick. The pieces of wood are to be put into a cruciblCf

S B S

404 VOLTAIC SPARK,

in contact with each other, the light evolved
more brilliant and intense than any that h
been procured by other artificial arrangements.
When the battery is powerful, the emission of
light may be kept up for a considerable time;
it is so dazzling as to fatigue the eye even by a
temporary glance, and when it ceases, leaves the
most brilliantly illuminated room in apparent
darkness.

This light appears to be principally derivi
from the immediate action of the Voltaic ap^
paratus, and not from the combustion of the
charcoal; for, though that is partly ignited, it
suffers Comparatively but little waste, and the
light is evolved with equal splendour when the
experiment is made in gases which ccmtain no
oxygen ; and will even take place, though with
diminished energy', under water, alcohol, ether,
oils, and other fluids whose conducting power ia
not too great

, The influence of the Voltaic spark on Turi*
0U8. gases may be ascertained' by the appatatus
described at page 83, and represented by fig. 0,

COTcred with 6ry sand -, wfaidi ts to be pIsKcd in a 6rc, &i»d kept
red hot for one hoor. Or the wood nuy be charred t^ptmigr
ing it beneath the surface of red hot lead.

FRODUCTfON OF LIGHT AND HEAT. 405

the wires within the globe being terminated by
pointed' pieces of charcoal, instead of balls.
When a globe of this kind has been exhausted
and filled with sulphuretted hydrogen, on taking
the Voltaic spark in it, the sulphur is separated,
and deposited on the interior of the globe, and
produces, during its separation, a very beautiful
appearance.

Some other compound gases are similarly
affected; phosphorus separates from . phosphu->
retted hydrogen, and arsenic from arsenuretted
hydrogen^

With the most powerful Voltaic batteries
the striking distance of the spart, or interval at
which it passes from one conductor to another,
is very inconsiderable. Mr. Children measured
this effect by means of a micrometer, attached
to two polished points of platina, which were
inserted in a receiver containing very dry air.
With 1250 pairs of plates the points were
brought within one-fiftieth of an inch of each
other before the spark took place.* With a
large apparatus employed at the Royal Institu-
tion, which extends to 2U00 pairs of four-inch
plates, points of charcoal were brought within

* Phil. TVam. for 1809* p- 9^.

406 PRODUCTION OF LIGHT AND UEAT.

a thirtieth or fortieth of an inch of each othi
before any light was evolved ; but when
points of charcoal had become intensely ignitcJ,
a stream of light continued to play between
them when they were gradually withdrawn even
to the distance of near four inches. The stream
of light w;is in the form of an arch, broad in
the middle and tapering towards the charcoal
points; it was accompanied by intense heal
and immediately ignited any substance intro-
duced into it; fragments of diamond, and points
of plumbago disappeared, and seemed to evapo-
rate, even when the experiment was made in an
exhausted receiver; though they did not ap-
pe«j to have been fused. Thick platina wire
melted rapidly, and fell in large globules; the
Baphire, quartz, magne^a, and lime, were dis-
tinctly fqspd.*

In rarefied air, the dischaj^ took place at a
girater distance, and the beam of light was
made to pass through an interral of ^x or seven
indies.

These phenomena nuty be exhibited on a
smaller scale by means of 100 pairs of plates of
Aix inches squere, an apparatus wfaicl^ is weli
• Elemonto of Chemical PhysKifih]', p. 153.

PROPUCTIOMT OF LIpHT AND HBAT. 4Qf

suited for all experiments of fusion apd igr
nitioa.

The arched form pf the stream of light pass«>
ing between two charcoal points, is often very
perceptible ^hen the distance of the points doe^
not exceed half an inch^

From the low intensity of the most power-
ful Voltaic apparatus^ but little attention to lUr
sulation is required in the transmission of its
effects. The conductors employed for this pur-
pose con/sist of popper wires passed through n
fhort piece of glass tube, which serves as an in«-
sulator to hqld them by^ Such conductors ar$
represented attached to the battery, and placed
on a glass plate to inflame gunpowder, i^

fig. 37.

As the charcoal points usually become ig-
nited wl^en the battery l>as moderate power, al-
most any combustible sut»stance may be in-
Oamed, if pUced between them. Oils, alcohot,
ether, and n^ptha^ are decomposed when the
points are plunged into them, and inflamed
when they are brought near each other upopi

the surface.

Some of the most pleasing effects of the

Voltaic apparatus result from its action on

DEFLAGRATION OF METALS-

metals; if these substances in thin leaves, are
made the medium of communication between
the opposite ends of a powerful battery, they
inflame, and by continuing the contact may be
made to burn with great brilliance. The best
method of performing these experiments, is to
suspend the metallic leaves to a bent wire pro-
ceeding from one extremity of the battery, and
to bring in contact with them a broad metal
piate connected with the opposite extremity;
the brilliance of the effect may be increased by
covering the plate with gilt foil. Gold leaf
burns with a vivid white light tinged with blue,
and produces a dark brown oxide. Silver leaf
emits a brilliant emerald green Hght, aud leaves
an oxide of a dark grey colour. Copper pro-
duces a bluish white light attended by red
sparks ; its oxide is dark brown. Tin exhibits
nearly similar phenomena, its oxide is of a
lighter colour. Lead bums with a beautiful
purple light; and zinc with a brilliant white
light, 'inclining to -blue, and fringed with red.
For "the distinct appearance of these colours it
is essential to make the contacts with raetal;
'for if charcoal be used, the brilliant white light

IGKITIOK pP WIKE. 4(>9

it evolves absorbs the colours produced by the
combustion of the metals.

^k( a fine iron wire be connected with one
extremity of a powerful battery, and its end be
brought to touch the surface of some quicksil-
ver connected with the other extremity, a- vivid
combustion both of the wire and the quick-
silverresults, and a very brilliant effect is pro-
duced.

If a fine iron wire of moderate length be.
made the medium of connexion between the
extremities of the battery, it becomes ignited,
and may be fused into balls; or if a platina wire
is employed, it .may be kept at a red, or even
white heat, for a considerable length of time;
which seems to prove that some power is con-
tinually circulating through it; but however
powerful the battery,' wires are never dispersed
by it, as they are by the action of a charged
surface.

If the slender wire be inserted in any fluid,
and then introduced into the Voltaic circuit,
the fluid may be made to boil.

It has been lately noticed, that if any two
wires of different thickness are taken, on either
of which a certain battery can produce ignition.

tFFXCT O** INCREASING

a greater length of the thickest wire will be
ignited than of that which is thinner. This
effect may probably arise from the cooling in-
fluence of tlie air, for the surface of the thia

tarire is most extensive in proportion to its quan-
mty of metal ; and that the surrounding medium
has an influence on the degree of ignition may
■ be proved by another experiment.

Experiment 23. Stretch a fine wire of pla-

■■ tJHJ I . pilliJMiiiihauigaw ivtcciMir. ^kmH^^^m

%n«KiiUqmi»«o #dhU«iBrf hw#.^. jMiliiiil^
iiig its opposite extremities viththe wtres ftots
a Voltaic battery, of sufficient power for tbst
purpose. Rarefy the air by the actioa of the
pump; and as the rarefaction proceeds the ig-
nition of the wire will become more vivid, ua>
.til at length it obtains a glowing white heat
Admit air into the receiver and the wire viU
-lose its intense heat, and appear more dull than
at ^Tst. Barefy the air again ; the ignition viil
increase. Restore it to its original density, it
will again diminish. These effects may be r&
peated many times, and will maiataiix the same

THJB laUMBKR Qf ?tATfiS. 411

proportion to each otbri) though they are lesa
intense at each repet)4i(cm*

I have ignite() |^ina wire in yarious gases,
without obtaining iMiy remarkable result, with the
excepcioQ of Q^fi experiment, in which a platina
wire stretchf^d in a receiver filled with hydrogen
gas, was split into a number of minute fibres
the moment the connection with the battery
was made. The result appears to have been ac»
cidental, and has not been obtained a second
time, in numerous repetitions of the experiment
under similar circumstances.

The power of a Voltaic apparatus increases
with the number of plates it contains; within
certain limits, but the limit is different for the
various effects it produces, and varies also with
the manner of employing the apparatus.

The effects have been stated by Volta to be
in the simple ratio of the numbers, but very li-
mited series only, had be^a put tc^ther at the
time this statement was made ; and there ap^
jMcars to be a loss of power when very extensive
arrangements are employed. The pure electri-
cal effects, and the force of the shock, I have
always found increase with the number, and I
have employed an arrangement of 1500. The

41t EFltatT OF mCRClAStKO *

power of chemical decomposition, and transfer;
also continues to increase with the number
when the battery is excited by dilute acid ; but
if it be charged with river water, the power does
nidt increase after four or five*hundred plates.
The powers of ignition have increased in exact
proportion to the numbers within' the limit of
one hundred plates,* beyond that limit there
appears to be a loss of power; for Sir H. Davy
found that one hundred plates ignited three
inches of platina wire one-seventieth of an inch
diameter, and one thousand similar plates
charged in the same way ignited only thirteen
inches.f t'rom the uniformity of the results I
have obtained, and their correspondence with
the experiments of Van Marum and PfafF, on
the continent; and Dr. Wilkinson, and Mr.
Cuthbertson in this country; I am disposed to
think the igniting power would be usually pro-
portioned to the number of plates, if they
could be always applied with the same effect;
but when the series is extensive, there are va-
rious sources of dissipation, and it is rather

* See Nicholson's Journal^ vol. xxix. p. 2Q, &c.
t Elements of Chemical Philosophy, p. 156.

THB NUUBEA.OF ?LATtS* 415

difficult to render the large propot-tion of acid
mixture then required, of uniform strength.

The French chemists have investigated the
ratio of increase for different numbers of plates,
as^ indicated by the quantity of gas liberated by
the decomposition of water; and they announce
that the increase is as the cube root of the num-
ber of plates.* The apparatus they employed, was
arranged in the form of troughs of a particular
construction, being part of a large apparatus
constructed by order of the French government.
Sir H. Davy states, that he has made similar ex-
periments with the large combination of Porce-
lain troughs employed in the Royal Institu-
tion, and the results he obtained, indicate an
increase nearly as the squares of the numbers.

The result of every experiment of the kind
must be uncertain if a series of minute atten-
tions are not observed, which appear to have
been overlooked in those already instituted.
The vessels employed for the decomposition
should be of the same size and form ; the wires
of the same length and thickness, and placed at
equal distances from each other, in a fluid of
uniform conducting power.

* Rechercbes Ph7S2co«Chimi^ues/ p,.30, &c. vol. i.-

414 SFF£Ct OF DIFFBEEVT SIZED ELATES*

When the size of the plates is increasedi
their effects on perfect conductors, such as me«
tals, cliarcoaly and strong acid solutions, are
greatly augmented; but their action on imper-
fect conductors, as water, and various weak sa-
line solutions, remains unaltered. If a battery,
for instance, of thirty pairs of plates of two
inches square, be compared with another bat-
tery of thirty plates of six inches square, charg-
ed with diluted acid of the same strength;
there will be no material difference in the shock
they produce, or the quantity of water they de-
compose in a given time ; but the small battery
will not melt wire, or bum metals, and will
scarcely produce a spark between two points of
charcoal ; whilst the large battery will evolve a^
brilliant light between the charcoal points, de-
flagrate metallic leaves with rapidity, and ignite
several inches of wire.

This remarkable fact, which appears to have
been first noticed by the French chemists, is
susceptible of some explanation, (on the suppo-
sition that the phenomena are electrical,) by re-
ference to what has been said in other parts of
this work on the subject of quantity and inten-
sity. If a Leyden jar, for instance, having a

EFFECT OF DIFFBRBNT SIZED PLATES. 415

3quare foot of coated surface, be applied to an
electrical machine with another jar, whose coat^
cd surface is equal to four square feet ; after a
certain number of turns of the machine, they
will both be charged, and to the same intensity,
for they will equally affect an electrometer*
But the large jar will contain four times the
quantity of electricity that the small one docs,
and will fuse sixteen times the quantity of wire.

Now, suppose an imperfect conductor, ca-
pable of transmitting only such a quantity of
electricity as is adequate to the charge of half
a square foot ; and it is obvious either of the
jars before mentioned, would produce the same
ieffect on such a substance ; for they both con-
tain more than it can transmit, and its conduct-
ing power, which remains the same in both
cases, limits the effect that can be produced by
either. It is consequently found, that if seve-
ral different sized jars are charged to the same
degree, the shock is nearly equally painful when
received from either of them.

Mr. Cavendish has stated, that ** iron wire
conducts four hundred million times better than
rain or distilled water ; that is, the electricity
meets with no moi^e resistance in passing through

tFlECT OF DIFFERENT SIZED PLATES.

, piece of iron wire 400,000,000 inches long,
* than through a column of water of the same
(iidiameter only one inch long. Sea water, or a
^:.8oltition of one part of salt in thirty of water,
^'Conducts 100 times, anil a saturated solution of
haea salt about 7'20 times better than rain wa-
hter."* It is therefore probable, that the power
I flxcited by a Voltaic apparatus, with plates of
ftwo inches squai'C, is in quantity equal or supe-
■ ^!«or to the conducting capacity of most aqueous
kfluids, and consequently no increased effect can
m%e produced on such fluids by larger plates,
'•which increase the quantity of that power, but
not its intensity. But if a conductor be pre-
sented to the large plates which is capable of
receiving the increased quantity tltey furnish,
the effect must necessarily be greater on such
conductor in proportion to the increased im-
pulse it may be supposed to receive. These facts
are capable of easy illustration.
■ . Experiment 24. Let two wires, proceeding
from the extremities of a battery of fifty or
one hundred plates of two inches square, be
plunged in separate glasses of water, if the
glasses are connected by putting a finger into
I • Phil. Trani. vol. Uvi, p. 198,

EFFECT OF DIFFERENT SI2ED PLATES, 417

each of them a shock will be felt at the moment
of contact. Connect the water in the glasses
by some fibres of moistened cotton, or by an in-
verted syphon filled with water ; on repeating
the contact with this arrangement, either no
shock, or a very slight one will be felt. Make
a sitAilar experiment with another battery of
the same extent, but with plates of six inches
squai:e. The shock will be nearly as great when
the glasses are connected by moistened fibres,
as when no connexion exists between them ;
and whilst the circuit exists through the mois-
tened fibres, and the human body, if a second
circuit be formed through a fine wire, several
inches of it may be ignited. The imperfect
conductors being incapable of conducting more
than a «mall portion of the power excited by
the large plates.

Whkt€ver be the cause of the power of the
Voltaic apparatus, I should conceive that the
quantity of that power excited by any given
number of plates under similar circumstances,
will be in direct proportion to the size of the
plates; and if the power be electricity, or should
obey the sajne law that operates with charged
surfaces, the comparative action of different

BATIO OP ICKITING POWER.

sized batteries, containing the same number of
,plates, should be, with itgard to their power of
igniting wire, in the pvoportion of the square
of the increased surface; thus if two batteries
.are taken, one containing fifty plates of twenty
square inches surface, and the other fifty plates
]0f forty square inches, the latter ought to ig-
nite four times the length of wire, the former
can ignite. From some experiments with plates
pf four inches square, and others, with plates of
eight inches square, made many years since, it
has been stated by Dr. Wilkinson, " that the
power of ignition, in batteries of the same to-
tal surface, but with plates of different sizes,
increases in tbe proportion of (he squares of th^
Burfaces of tfa« elementary plates, singly taken
ill eadi.'* * . It was aft?i:wards. shqwn by Mr,
Harrison of Kendal, that whe^ t^ total, surr
hce^ are not equal, the rate of i^itipn. ^uat be
es the sixth po>per of th^ diameters oi the; pUf-
pientaiy |>lates, or as the cubes pf tlwir'respiap*
|ave surfaces.-)- It appears also froip .sqm^.ex-
periinen.ts witli Urge plates, m^ntipned t^ySip
a* Davy,. thai; ^_ power of ignitiop fpr equal

i- * NichoItMi's Jonnial, vol, vti. f . KJ^* ■■'

- f Ibid. voLix. p. 24,2

LARGE VOLTAIC APPAAATI))^ 419

numbers of plates probably increases in a higher
proportion than the squares of their surfaces ;
for twenty double plates, each exposing a sur«
£ice of eight square feet, ignited more than
ifixteen times as much wire as twenty double
plates having each a surface of two. square
feet^

Experiments of this kind should be made
with batteries that have never been employed
bjcfore, for the least, difference in the state of
the plates will have a material influence on the
results obtained. Trials should also be made
with various sized plates, increasing in regular
progression from the smallest that are capable
of igniting moderate-sized wire to some of at
least a foot square.

Some inquiries of this kind haA^'e, I believe,
been instituted by Mr. Children; who has ar-:
longed some gigantic . batteries, having the
largest plates hitherto constructed. The first
arrangement consisted of twenty pairs of cop-
per and zinc plates, each plate four feet high
and two feet widq, placed in a wooden trough
covered with cement : the quantity of fluid re-
quired to excite it was 120 gallons. The efject

* lAiemical Philosophj^ p. i$6^

2^2

•'•.■■, Z^,

I 4S0 tARGB VOLTAIC APPARATUS.

of this enormous battery on imperfect con-
ductors was very inconsiderable, and it did not
■ r afifeCt a gold leaf electrometer ; but it produced
powerful effects of ignition; rendered tbrec
feet of platina wire, 1 -30th of an inch diameter,
perfectly red hot, so as to be visible by strong
I day-light ; melted completely eighteen inches
of the same wire; ignited points of charcoal,
and evolved a most brilliant light; but its
agency in chemical tlecoinpositiou was scarcely
perceptible.*

More recently, tlie same active philosopher
has put together a battery of similar extent,
but with plates of two feet eight inches wide,
and six feet long. The plates were fastened to
a beam, which was suspended by counterpoises
ffom the ceiling of his laboratory, so that the
plates could be easily raised or let down into
Uie cells. With this apparatus six feet of thick
platina wire was ignited, and shorter pieces'
melted with facility. Iridium was melted ioto
a. globule, and the ore of iridium and osmium
was partially fused; the heat produced appears:
to have been more considerable than has been
hitherto obtained by any other;means. ,
* Philou^icil TraDnctiooi for 180pj p. 32.

EXTENSIVE SERIES OF LARGE I^LATES. 4S1

A very powerful Voltaic apparatus has been

recently constructed by order of the French
government. It consists of 600 pairs of ptates,
each neai^ (eleven inchies^ square, and consequently
exposing together near 500 feet of surface;
they are arranged nearly on the principle of the
trough already described as the invention of
Mr. Cruickshank.* Bes^ides this extensive ar-
rangement of large plates, thei'e is a sei'ies of
1500, of a smaller size. No experiments on
the igniting power of this battery' appear to
have been made; its action having hitherto
been principally applied to imperfect conductors
and to the production of electrometrical effects.
The first experiments were on the comparative
action of different fluids, both as exciters of the
power of the battery, and mediums for the ex-
ercise of its chemical agency. The fact I have
before adverted to, namely, that the electrical
and chemical energies of a battery are never at
their maximum together, but require different
conditions for their production, was noticed
during many of these experiments. Twenty-
four of the large plates, excited by a mixture
of acid and water, decomposed the alkalies, and

* Page 323.

42S EXPERTXRMTS OF THE

effected many other chemical changes, distinct-^
]y ; but produced only a slight effect on the elecf
trometer by the aid of the condenser. The
whole series of 600 large plates, when charged
with water, did not produce any similar che«
mical effects, but their electrical power was
much more considerable. The best conducting
jQuids were found to be most active as exciters
of the chemical powers of the battery ; thus
saline solutions acted more powerfully than
water, acid mixtures more powerfully than sar
line solutions, and strong acid mixtures were
0iore powerful than those more diluted. In
some instances, a mixture of acid and salt Mras
more active than acid alone ; and when acid
mixtures of various strength were successively
employed, the quantity of gas disengaged by
two platina wires, from the same fluid, were
nearly proportioned to the increasing strength
of the acid used to excite the battery. The
fluids which were most efficient in exciting the
chemical power of the battery, were most ra*
pidly decomposed when exposed to its action;
and their excellence in this respect appeared to
be proportioned to their conducting power. —
Saline solutions were found to conduct better

FRENCH CHEMISX8.: 4SiSt

than water, alkalies bettet than salts/ land acidi:
better than alkalies. With sulphate of soda a
curious result was observed ; the facility of de-
composition was as the cube root of the quan-
tity of salt contained in the solution ; so that
if one solution of sulphate of soda yield twice
as much gas as another in the same time, and
with the same power, it is found to contain eight
times as much salt. In the employment of dif-
ferent series of plates for the decomposition of
water, the effect was found not to increase by
any means in proportion to the number of the
plates ; so that when many batteries are applied
to this purpose, it is better to employ theih.
separately, on different portions of water, thau
collectively on one portion.

With batteries of different sized plates,
charged with diluted sulphuric acid, the quan-
tity of gas disengaged from weak nitric acid,
by any given number of plates, was nearly in
the proportion of their respective surfaces.

The large battery of 600 plates was usually
excited by a mixture of 1 part sulphuric acid,
70 parts water, and 9 or 1 parts of common salt.
The shock from it, when taken by an individual,
wais exceedingly painful, but when received by

4S4

EXPEaiMENTS, &C.

three or four joining hands, was much more
moderate. The intensity of the battery in this
state of action was such, that a spark could be,
obtained from water by its means ; and the ac-
tion was always too violent at first to permit the
successful decomposition of the alkalies, which
may be better accomplished with a lower;
power.

In twenty minutes the poM'ers of chemic^
decomposition usually ceased; but the shock wa|r'
still produced very powerfully, and the electrit
cal effects continued without any diminution.*^

From these experiments it appears, that thA^
chemical action of a Voltaic battery is greatest^
when the fluid by which it is excited has most;
cooductiDg power, and the greatest facility of
decomposition; but that these circumstaDces
liave not the same influence on its electrical,
powers. .

• Kediercbea Pbyiico- Cbimiiiues, vol. i. pp. l to Ml ■

425

' <

CHAP. IV.

Sketch of the State of Theoretical Knowledge in
Voltaic Electricity. Structure and Properties
of the Electric Column.

In the preceding Chapters the most import-
ant properties of the Voltaic apparatus have
been described, and in some cases the opinions
that have been advanced in explanation were
considered ; it is therefore unnecessary to ex-
patiate very extensively on this part of the sub-'
ject, in Avhich our knowledge is still very im-
perfect : a statement of the facts, which must
be considered in every rational theory, promises
therefore to be more useful than a detailed ex-
position of the various theories that have been
proposed.

In all our Voltaic apparatus, there is a com-
bination of three different substances in contact
with each other, in successive groups ; in gene-
ral it is an arrangement of copper, zinc, and
some conducting fluid. It is demonstrable, (as

42$ INDICATIONS OF

has been shewn,*) that the primary source of
the electrical power of the apparatus, is the as-
sociation of the two metals ; and according to
Volta, the interposed fluid serves only as a con-
ductor of the effect of one pair of metals to an-
other. As far as electricity is concerned, this
opinion appears to be correct, for the electro-
meter is acted on, whatever be the nature of the
interposed fluid, f and the degree of divergence
is proportioned to the number of the plates.
The electrometrical effects prove also, tha[t the
arrangement of a series of zinc and copper
plates, with an interposed fluid, forms a con-
ducting column, which in its insukted state is
positive at one extremity, negative at the other,
and neutral in the middle. This may be easily
shewn by three gold leaf electrometers, con-
nected at the same time with an apparatus of
three or four hundred pairs of plates. The elec-

* Seepage 3l6 to 318.

f Thus Volta found the same effect on the electrometer
when his apparatus was charged with pure water or with brine.
And in the experiments of the French chemists, the large
battery produced the same electrometrical effect when first
charged with diluted acid, which bad a strong chemical action
on the plates, and when the acid had dissolved so much zinc as
1*0 form a saline solution which had no chemical action.

EI^ECTRO-MOTIOIV. 4S7

trometer connected with the copper extremity/
will diverge with negative electricity, that con-*
nected with the zinc end, will separate to the
same distance positively, and that connected
with the centre plate of the series, will not be
affected. But if either extremity of the battery
be connected with the ground by means of a
wire, the leaves of the electrometer connected
with it will close; and those of the central elec*
trometer will open with the same electricity^
and to the same extent, whilst those of the op^
posite extremity will have their original diverge*
ence increased.

Hence it appears there is a real electro-mo*
tive property in the apparatus, by which the
zinc end constantly tends to become positivey
and the copper end negative ; and it is also pl>
vious, that the extent of this operation at either
extremity, is increa9ed by connecting the op-
posite end with the ground. This last experi*
ment, by which the central plate may be ren*
dered either positive, negative, or neutral at
pleasure, proves also that the interposed fluid
never acts as an insulator, for if it did so th^se
changes could not possibly occur.

As th^ contact of dtber surface of the ba<>'

428 INDICATIONS OF

tery with the ground, exalts the electrical state
of the opposite extremity, the same circum-
stance may be i)resumed to take place with
every pair of associated metals, when their sur-
faces are in contact with a conducting fluid.
Whilst the apparatus is insulated, the first zinc
plate can only act on the electricity of its asso-
ciate, the first copper plate ; but the second zinc
plate, through the conducting interposed fluid,
can act on both these, besides its companion
the copper, and may therefore become more
highly positive ; and it is easy to conceive that
such a repetition of action would be attended
with an increase of effect proportioned to the
number of plates, and tliat the electrical ten-
sion of either end must be increased by con-
necting the other with the ground.

To ascertain if this principle really operated
with a single combination ; I took a pair of cir-
cular plates six inches diameter, very clean and
even, one of zinc and the other of copper, and
each provided with an insulating handle. When
both plates were held by their insulating han-
dles, and the zinc was successively applied to
the flat surface of the copper, and after each
contact made to touch the insulated plate of a

ELECTRO-MOTION, 4&9

condenser of six inches diameter ; twenty con-
tacts were required to communicate such a
charge to the condenser, as would occasion the
leaves of a very delicate electrometer to sepa-
rate to a quarter of an inch. But when the cop-
per plate, instead of being held by its insulating
handle, was simply laid on the hand, or on any
similar conducting body; ten successive con-
tacts of the insulated zinc plate, cominunicated
a charge to the condenser, which occasioned
the gold leaves to separate to the distance of
more than half an inch ! On repeating these ex-
periments, with the variation of touching the
condenser with the copper plate, held by its in-:
sulating handle, and brought in contact with
the zinc plate, first insulated, and then uninsu-
lated, similar results were obtained, but with
the contrary electrical state. Hence the simi-
larity of action in a single pair of metals, and a
combined series is sufficiently proved; and the
preceding statement of the manner in which
the electrical power is supposed to* increase with
the number of associated plates, is rendered
highly probable.

So far the phenomena are sufficiently simple,
and consistent, for those described are not ma«<

490 PROBABLE CAUSE OF

terially influoiced by the nature of the inter*
posed fluid, nor do they occur^ but when the
extremities of the apparatus are unconnected
with each other, and consequently capable of
maintaining the opposite electrical states. But
(he chemical effects,, the shock, and the power
of ignition^ take place (mly when the extremi-'
ties of the apparatus are connected by some con^
iuctor^Mnd are also materially influenced by the
nature of the interposed fluid. If these effects
then, are produced by electricity, they can only
resnlt from its circulation in the apparatus ; and
as. there is no. reason to suppose that the electro^
motive power of the associated metals ceases
when there is a conducting communication be-
tween their opposite surfaces ; but rather that
it is accelerated by such a circumstance ; that
very acceleration may be the cause of the phe-
nomena, and the effects observed correspond
very nearly with such an idea ; for if it be ad-
mitted that the connexion of the opposite ends
of the Voltaic battery by a conductor, occasions
2L current of electricity from the positive to the
negative, that current must be more rapid, in
proportion as the conductor is more perfect.
Now it is found that the chem.ical effects ara

XHB PHENOMENA. 431

most considerable, and more promptly produced
in fluids of the highest conducting power; thus
the quantity of gas liberated in a given time
from common water, is greater than from dis-
tilled water; saline fluids furnish more than
common water; solutions of alkali more than
saline fluids, and acids more than alkalies : and
as the effects of a simple combination are inr
fluenced by the same causes as those that operate
with a series ; the fluids that are susceptible of
the most rapid decomposition, are also most ac
tive in exciting the chemical eflfects of the batr
tery, when employed as the connecting.medium
between its plates.

Acids are of all other fluid bodies, excepting
metals, the most perfect conductors, and the
chemical eflfects of the battery is more power-
fully excited by them than by any other sub-
stances ; it i^ possible their chemical action on
* the zinc may have some share in modify'ing the
quantity of electric fluid, or the rapidity of its
motion ; but it is certain the effects are not in
proportion to the chemical action: sulphuric
Mid, for instance, acts, as powerfully on the
zinc as nitric or muriatic acid; but it is not sa
active, ii^ producing the chemical agency of the

4dS THEOEETICAL VIEWS.

battery: in like manner the alkalies which exert
a very trifling action, on the battery, excite its
powers with greater energy than many saline
4uids which are more efficient as chemical

agents.

The ignition of wire, and of charcoal, in the
Voltaic circuit, is conformable to this view;
these substances are the most perfect conduc-
tors known, and when made the medium of
communication between the opposite efids of a
battery, must accelerate its electro-motive power
to the greatest extent. The rapid circulation
of electricity thus obtained, produces ignition,
if the conductor be not too large in proportion
to the quantity of electricity ; but within this
limit, the effect will be greatest with the thickest
wire, because the acceleration will be more con^
siderable in proportion to the facility of trans-
mission. There is perhaps no other view on
which the continued ignition of wire, and the
increased action of large plates is so intelli--
gible.

The cessation of chemical agency, and ig-
niting power, as the chemical action of the
acids or other menstrua declines, may arise from
the total change which then occurs in the na-

THEOR&tlCAL VIEWS. ^ 439

ture of those fluids; their conducting power is
much diminished, and they may possibly by the
chiEiQge in their chemical properties, acquire
some faculty of electro-motion subversive of
the effect of the combined metals.

' These observations are offered, as the most
plausible inference from the observed facts that
has yet occurred to me; jand I shall be very
highly pleased, if they are the means of elicitt
ing somie more satisfactory explanation of these
phenomenar ' ;

It has been sometimes supposed that the
fluid by which the different pairs of plates in a
battery are separated from metallic contact with
each other, does not act as a conductor ; but,
that " with regard to electricity of such low in-
tensity, water is an insulating body." Did the
action of the battery, or the phenomena of fluid
decomposition depend on* a circumstance of thii^
kind, that action, and those phenomena^ would
be necessarily produced most perfectly by die:
most insulating fluids, but the very Converse of|
this is observed ; and s^ little does the electro«»
j^tion of the Voltaic apparatus depend pn any,
insulation between its plates, that?aU its pheno«,
mena are produced when ^^ c^lUs of' a , tr<9i^b

434 GINGULAU EXPERIMENT.

are filled so as to overflow, and the differeut
plates arc consequently connected over their
top edges hy a considerable stratum of fluid.
Nay, the effects continue, though with dimi-
nished energy, when all the plates are connected
together by tnelal, and consequently when every
part of the apparatus is equally conducting. I
cut a number of thin slips of sheet copper, and
bent them into the form of the letter U, so a%^
to form a series of simple springs. I then
troduccd both legs of one of these springs into,
each cell of a Voltaic battery, so that it pressed
forcibly against the copper surface on one sids
the cell, and the zinc surface on the other.
Having, in this manner, made a regular' meOiiie
communicatioH between every pair of ptatesnt
a 4atteiy cbntaimng 50 of three' inehea square,
I' filled the cells with a diluted a»d, and found,'
that notwithstanding the total absence Of iosu-
lation, water was decomposed witfe greatra-
pidity, a' -vivid spark produced by- charooal
- points, and gunpowder ' inflamed v Qi^d oiV"ap-
plyiHg the condenser, a charge was coaimum-
cated which occasionefl. the gold leaves of- the
electrometer to strike the sides of tbe glass.
. This phenomenoa 9{^eart the mor&extpvor-

THEORETICAL TIBWS* 435

dinary at first view, because it is well knowti
that if the plates are all connected together by
a thin wire, the effect is almost totally destroy-
ed ; but in such case, the opposite copper, and
zinc surfaces of each pair of plates are made to
communicate with each other, and consequently
their electricities circulate individually, instead
of being propelled forward from one cell to the
other. But in the arrangement above described^
the metallic springs are in contact with the zinc
surface of one pair of plates, and the copper
surface of another ; there is consequently no
communication between the opposite surfaces
of any individual pair but what arises from the
association of the copper and zinc; and as their
mutual contact produces a motion of the elec<*
trie fluid from the copper to the zinc, it cannot
operate as a conductor in the contrary direc«
tion. The effect is therefore only diminished
in proportion as the copper spring, by placing
part of the zinc plate between two copper sur*
faces, diminishes its electro-motive energy. This
experiment appears to me a satisfactory proof
of the electro-motive power produced by th<i
association of the metals, and of its tendencq|[
to produce a current of electricity from one ex*.

2F 2

436 £XPSBIM£KT8 OF BBRZBLIUS*

tf emity of the battery to the other, and con*
sequently a circulation of electric fluid when
the opposite extremities are connected : it also
l^oves that the electromotive power is influ'^
enced i!>y the nature of the substance interposed
between the different pairs of metal, and thus
accounts in some measure for the different ef^
feet produced by different fluids. This last cir*^
cumstance is an interesting subject of inquiry;
<ome instructive facts respecting it have been
detailed by Professor Berzelius, in an account
of an ingenious experiment made to prove that
oxidation is not the cause of the electricity of
the Voltaic apparatus. The following is ex-
tracted from his description. *' I took twelve
tubes of glass, half an inch diameter and three
inches in height^ and closed at one end. I half
filled them with a strong solution of submuriate
of lime (such as is obtained from the residue
after the preparation of caustic ammonia), and
alx)ve this fluid I poured diluted nitric acid>
with the precaution not to mix the liquids.
I arranged these tubes in succession, and then
took copper wires, round one of the extremities
of each of which I had melted zinc, in order to
attach a knob of that metal to that end. I inr-

2X7SRIMENTS OF BEnztLlOtf. 43^

xnersed the zinc-coated ends of each into ont
of the tubes to the bottom of the submuriatc^
and then bended the upper ends of the respec-
tive wires so as to immerse them in the middle
of the acid of each nearest tube. This arrange-
ment consequently formed a scries in the order
following: copper, zinc, submuriate of lim^
nitric acid ; copper, zinc, &c. It is evident that
the chemical affinity which produces oxidation
iit the common temperature, was here at the sur-
face of that part of the copper which was in
contact with the nitric acid ; and that if this
oxidation had been the primary cause of the

electricity of the apparatus, the pok of coppery

in this construction, ought to have possessed the
same electricity (namely, the positive) as the
zinc pole in the common pile. Before the extre-
mities of' this small apparatus were connected,
the copper continued to be constantly dissolved
in the acid, which it turned blue, and the sur-
face of the zinc remained metallic and without
any perceptible change. And lastly, I com-
bined the poles, by means of silver wires, passed
iato ^ tube filled witiii a solution of muriate of
soda. But I waa greatly surprised to find the
effect, directly contrary to what the theory^

Experiments or bekzelius

which considers oxidation as the cause of the
electricity of tlic pile, had led me to expect
The solution of the copper instantly ceased,
and the zinc became covered with a mass of
white oxide, vegetatlnfi; on all sides in the form
of wool. The pule of the copper produced hy-
drogen gas as usual, and the zinc pole caused
an abundant precipitate of muriate of silver.
Tlie electric state, tliercfore, produced in this
case an affinity, which at the ordinary tempera^
ture of the atmosphere is inactive, and caused
another very active afliiiity to cease, which yrsM
already in operation ; and this could be effectat
by no other cause than that of the electricity pro-
duced by contact, which occasions the electric
charge of the pile, and disposes the affinitieB
which shall be put into activity.

*' This little apparatus was very powerfid»
and disengaged so large a quantity of gasj
would not have been exceeded by one hundi
pairs of plates. But what could be the cause
this? — I exchanged the submuriate for neuti
muriate; it then produced a very moderate
feet, corresponding with the number of pai
and, lastly, I substituted neutral muriate
zinc instead of the muriate of lime, and tl

EXPERIMENTS OF B£RZ£LIUS. 43^

the effect was scarcely perceptible, though it
continued sufficient to prevent the oxidation of
the copper in the nitric acid, and tp show^hat
the conductor of the zinc pole continued always
to be oxided." * :

This eitperiment demonstrates the influence
of the interposed fluid on the cheitiical effecibs
of the apparatus, which may probably arise from
its action on the electro-motive power produced
by the association of the metds. It indicates
alsoi that the chetnical action of the battfcry is
never exerted but when the electric fluid cir-
culates from one extremity to the other; and
corresponds in this respect with an experimeat
mentioned by Sir H. Davy, in which forty pom-
,pound arcs of zinc and silver were arranged in the
usual order, in a series of glasses, filled with a ^-
lution of muriate of ammonia rendered slightly
acid by niuriatic acid; whilst the extreme part3
. remained unconnected, no gas was disengaged
frdnfi the silver, and the zinc was scarcely acted
upon'; but when they were coilnected, all the
zinc wires wiere dissolved more rapidly, and hy-
drogen was disengaged from every silver wire.

* Memoirs of the Academy of Stockholm for 1812) or
|Iichols6n*s Joaroal, vol. xxxiv. p. l6l.

440

PHENOMESA OV THE

la gimple Voltaic combinations, it appeal's
essential to the production of chemical eflccts,
that there be a transition of the elements of the
interposed fluid; and as this may be presumed
to take place also in each cell of a battery, it is
perhaps one cause of the superior action of those
fluids which arc most readily susceptible of de-
composition. When, for instance, (as in exp&«
riment 19,) a compound arc of zinc and plj
tina is placed with the platina leg in a solutio
of silver, and the zinc leg in dilute muriatic
acid, no precipitation of silver takes place uoi
less the glasses are connected by some fluid ni*t
dium, or by a metal which is soluble in the acift
of the solution of silver. With arcs of platina^
or gold therefore, no effect is produced, eithofj
in this arrangement, or that of the fifteenth ex-t
periment ; but with any other metal, a portion
of the silver or copper of the solution is revived,
and a corresponding portion of the simple con-
necting arc is dissolved, and occupies the place
of the revived metal in the solution. Henee
the corrosion of the zinc plates in the Voltakw
battery, and the liberation of hydrogen at th«
copper surfaces.

From the phenomena liitherto described, it.

VOLTArC APPARAtUa. 441

appears that the primary source of the electric
power of the Voltaic apparatus may be con-
sidered to be the association of the metals of
which it is composed ; but the chemical effectd,
though probably arising from the same cause,
are obviously influenced by the nature and ac-
tion of the interposed fluid. The relation of the
various parts of a Voltaic apparatus, (as usually
constructed,) to the various effects it produces,
have been recently developed by the masterly
experiments of Mr. De Luc** The ordinary
apparatus consists of three constituent parts,
namely, two metals and a fluid, being usually
when arranged in a pile; copper or silver, zinC,
and wet cloth, following each other in succes-
sive groups. Now, if these be regarded atten-
tively, without any regard to Volta's theory,
they may be considered as divided into ternary
groups under three different aspects.^ — 1. Zinc
and silver with wet cloth between them. — 2. Zinc
and silver in mutzutl contact with wet cloth on
the side of the zinc. — 3. Zinc and silver still in
mutual contact, but the wet cloth on the side of
the silver. Either of these ternary associations
may be the cause of the action of the apparatus;
* Nicholson's Journal, toI. xxn. p. 1 13, ftc.

442 EXPERJMSKTS OF MR. DE LUC.

but the really efficient giotips may be ascer-
tained, if each of the ternary associations are
successively mounted as a pile, the different
groups being separated from each other by some
conductor that does not materially affect their
electro-motive power. Mr. De Luc employed
for this purpose small trijiods, formed of brass
wire so bent, as to touch the plates bet\reen
which the tripod was placed, only at the three
points of support.

The first dissection of the pile by this me-
thod was to form an arrangement of seventy-six
groups of zinc and silver with wetted cloth be-
tiveen them ; one group being placed first, (sup-
pose with the zinc plate lowest,) then npon the
silver plate a tripod of braxswire; upon that
another group with the zinc plate lowest; again,
itpon its silver, a tripod, upon that a thifd group
in the same order, and so on until the whole
seventy-six groups were arranged.

Under these circumstances the same chemi-
cal and ^ectrical effects were obtuoed, as when
the apparatus was put together without the
brass tripods. It tlierefore appeared that the
efiBcient groups for all the effects of th^ appa-
ratus, were an association of silver and zinc,

EXPERIMENTS OF JklR. D£ LUC. 443

with wetted cloth between them. To ascertain
the truth of this indication, a second dissection
•was made. In this the two metals were placed
in contact with each other, and the wet cloth in
contact only with the zinc plate. Suppose a
-pair of zinc and silver plates in contact with
each other, placed on the base of the pile with
the silver lowest, iiien a disk of wetted cloth
upon the zinc, and a tripod upon the wetted
cloth ; then another group of zinc and silver,
with wet cloth upon the zinc ; then again a tri-
pod, and so on in regular order, until the se-
X^enty-six groups were arranged.

With this apparatus the electrical effects
were produced as before; but though these
ceased when the usual glass tube for decompos-
ing water was made to connect the opposite
poles, not the slightest chemical effect was pro-
duced.

From this it appears, that the condition for
the production of chemical and electrical effects
is different, the latter requiring the arrangement
of silver and zinc in mutual contact, the sue-
cessive pairs being separated by a moist con-
ductor, which may be in actual contact with the
zinc only ; the former requiring the association

4-44 EXrEEJMENTS Of MR. DE lUC.

of silver and zinc, with wetted cloth bet-ween
them.

A third dissection of the pile was thus ar-
ranged: silver and zinc in mutual contact,
wetted cloth in contact with silver : 76 of these
groups were placed in regular order, with a tri-
pod upon the wet cloth of each group, as in
the former experiment. With this arrangement
neither chemical nor electrical effects were pro-
duced; the absence of electrical signs Mr.de
Luc ascribes to the zinc plates being in con-
tact on one side with the silver, and on the other
with the brass of the tripod, which he regards
as a counteracting effect. The absence of che-
mical signs arises from the want of the con-
dition for tlieir production, namely,, successive
associations of zinc and silver, witli a fluid ;be-
tween them and in contact with both. .

When either the continuous pile or that
composed of the. efficient ternary groups are
put together with the pieces of cloth moistened
with pure water, although chemical effects are
produced, no perceptible shock can be felt; but
when the pieces of cloth are moistened by a solu-
tion of common. salt, the shock is very distinct
Hence Mr. de Luc concludes, that for thepjo-

EXPERIMENTS OF MR. D£ LUC. 445

duction of chemical effects in the circuit it is
essential that the zinc undergo oxidation, and
for the production of the shock it is necessary
that such oxidation be effected by the action
of an acid.

Mr. de Luc conceives the phenomena of the
pile may arise from some modification of the
electric fluid which pervades it during the Oxi-
dation of the zinc ; and as, in his experiments, ,
he obtained more perceptible electrical indicar
tions by the aid of the condenser, from wire3
immersed in water, when the chemical effects
and the shock were produced, he concluded that
this modification of the electric fluid was at-
tended by a retardation of its course, by which
k very small quantity w^as enabled to produce
effects which are not obtained by a much larger

quantity when set in motion by the electrical
machine.

This idea, it may be observed, is the very
converse of that which, from a more general
and extended view of the phenomena of the
Voltaic apparatus, I have ventured to propose.
It was indeed a natural inference at first view,
from the experiment in question, when that
alone w^i considered; but the increased rapi-

44(» PHENOMENA OP TUB.

dity of liecompositioii wliicli always attends the
increased operation of that influence, which is
here supposed to cause a retardation of the cur-
rent that occasions decomposition, is very inimi-
cal to any such supposition ; and the usual phe-
nomena of electrical analysis are equally at
variance with it.

When any fluid is decomposed hy the action
of the common electrical apparatus, the effect is
always proportioned to the intensity of the cur-
rent of electricity that passes through it; and
in the decomposition of water, when the metal-
lic surface in contact with it is of moderate ex-
tent, very strong shocks in rapid succession are
required. It is to the acute intelligence, of Dr.
Wollaston we are indebted for the means of
executing this analysis with a more moderate
power. He enclosed the metallic conductor in
glass, or wax, and exposed only a very small
portion of its surface to the fluid. The current
of electricity being thus reduced in volume,
was proportionably increased in force ; and by
rendering the exposed surface very minute, a
sufficient intensity was produced, by a moderate
quantity of electricity.

when a circuit is made through water, by

VOLTAIC CIRCUIT. 447

wires proceeding from the opposite extremities
of a Voltaic battery, those wires can impart no
charge to the condenser, unless the quantity of
electricity evolved by the battery is greater
than the water can transmit t • therefore any
cause that increases the quantity,- will produce
an augmentation of effect by this test, whilst
the column of water remains the same : or if
the velocity of the electro-motion of the appa<*
ratus be increased, whilst the same imperfect
conductor is interposed between its extremities,*
a similar effect must take place ; for the posi«
tive wire will receive electricity from the pile,
faster than it can transmit it to the water, and
thC' negative wire yields electricity to -the pile^
more rapidly than it can receive it from the
water ; so that a slight positive, and negative
charge will be given to the condenser by these
wires respectively, whenever the electro-motion
of the pile supplies^ electricity faster than the
water can conduct it ; and the charge will be
highest when the supply is modt rapid. Kow,
according to the principle I have proposed, the
most rapid electrio-motion of the apparatus, will
be produced when the different pairs of plates*
communicate with caj^h.otiber through* the iM^

448 EFFECT OF DIFFEEENr FLUIDS.

dium of the best conducting fluids : it is there-
fore obvious, that the result of Rlr. De Luc'a
experiment, in which a more considerable charge
was communicated to the condenser by wires
immersed in water, when the pile was excited
by a saline solution, than when it was excited
by pure water, is conformable to the principle
I have state<l ; and the legitimacy of this in-
ference is confirmed by a variation of the ex- -
perimcnt; for if, when the apparatus is excite^ I
by a saline fluid, the tube that connects its ex- »
tremities be filled with the same fluid instead of
pure water, no increased charge will be given
to tlie condenser by either of the wires, becausq ■
the increased electru-iiiulion of the apparatus
is then compensated by the increased conduct-
ing pQwerof the fluid by which its extremities
are connected.

When different degrees of chemical action
are excited in the Voltaic apparatus by the in-
troduction of various fluids, I have always found
that the, mor^ powerful the action that is pro-
duced, the more transient is its dura^on. This;
circumstance is of importance in the pra»ctical
application of the instrument, -^ince it offers the.
nie^nspf judiciously ap^lyipg various toethod*

TltE ELECtmC COLtXMlr. 440

of experiment, and of continuing the action of
the apparatus during any required tim€. When
the battery is charged with water, it» chemical
action is feeble, but it appears to continue with-
out diminution for an indefinite length of time;
by the addition of a minute quantity of muriatic
acid, -^^Trth part for instance, its chemical ac-
tion is greatly augmented, and still continues^
for a considerable period. When the proportion
of acid is increased to a 30th or 20th part, the
action is considerable, but comparatively of
short duration. I have found no solutions so
advantageous as those of acids, and I prefer the
muriatic acid to all others ; the nitric is indeed
rather more powerful in the same proportion,
but its cost is four times as great, and I have
found that it destroys the copper plates as well
as the zinc. The nitrous gas evolved by itis action
is also much more offensive than hydrogen,
which results from the employment of muri-'
atic acid.

The experiments of Mr. De Luc induced
him to conclude with Volta, that the electrical
effects of the apparatus result entirely from the
successive association of the different metals,
separated jinto pairs by some conducting »nh^

460 WIK BLECTRIC COLUMH..'

Stance that does not interfere with their eleetro-
niotivc power. To ascertain if a liquid was
essential to this effect, he mounted a pile with
pieces of cloth not moistened, and he found the
electric effects were still produced, but some-
what weaker than with the M'-etted cloth. He
the.n instituted a series of experiments, suc-
cessively mounting the pile with different ani-
mal and vegetable substances, interposed be-
tween the pairs of metal, instead of wetted
cloth. Of the various substances tried, he pre-
ferred writing paper, as the most convenient of
those that were efhcicnt. The apparatus con-
structed in this way was found to have the
same electrical indications as the commprv Vol-
teic pile, but it produced no chemical eiFects,,
hqw-ever numerous the pairs of plates ; nor was
any oxidation of the zinc produced by its most
protracted action. These circumstances led to,
the idea, that by the extension of the number
of groups, a kind of perpetual electric machine
might be formed ; and, as inthe previous trials,
it had been found that the effect was rather in-,
creased by pasting the paper upon the silver or,
ccxpper. Dutch gilt paper, which consists of
thinxopper leaf, laid upon paper, was employed.

THB ELECTRIC COLUMN* 451

instead of the usual silver, or copper plates, and
moist conductors. Eight hundred plates of
tinned iron being put together with the same
number of Dutch gilt paper between them, the
copper sides being all turned in one direction:
the combination was found to affect the electro-
meter more powerfully than any Voltaic battery
had been ever observied to do ; but on the ap-
plication of the usual glass tube with water, no
chemical effect was noticed. The apparatus
was left for a considerable time, and its action
on the electrometer continued without diminu-
tion ; and subsequent experience has shewn that
it does so for any period during which the cx^
periment has been continued.

Thus was invented a new and important
Voltaic arrangement, highly valuable both in a
theoretical and practical view : in the former,
as separating the pure electrical effects of the
Voltaic battery from its chemical power, and
demonstrating thq permanence of its electro-
motive faculty: in the latter, as providing a
spontaneous and permanent electrical machine,
in which the opposite electrical states perpetu-
ally exist, without any new excitement. Be-
sides these properties, the new apparatus pro-

2 G 2

IHK F,r.KCTntC COLUMN.

mises 1,0 become an important meteorologicai
instrument; for the degrees of its electrical in-
dications have been observed to vary with the
different seasons of the year, and arc probably
inflnenced by some of the causes by which our
atniosplierical phenomena are produced.

To distinguish this instrument from the
usual Voltaic apparatus, from which it differs
in many respects, Mr. De Luc has proposed to
call it " tlie Electric Column," an appellation
suthciently appropriate, since the effects it pro-
duces are purely electrical.

I have made very numerous experiments on
► the construction of such columns, and have
varied their combinations most extensively. The
materials I prefer, are thin plates of flatted zinc
alternated with writing or smooth cartridge pa-
per, and silver leaf. Tlie silver leaf is first laid
on paper, so as to form silvered paper, which is
afterwards cut into small round plates by means
of a hollow punch. In the same way an equal
ifumber of plates are cut from thin flatted zinc,
and from common writing or cartridge paper.
These plates are then arranged in the order of
zinc, paper, silvered paper with the silvered side
upwards; zinc upon this silver, then paper, ant!

ti.

PERPETUAL CHIME. 453

again silvered paper with the silvered side up,-
wards ; and so on, the silver being in contact
with zinc throughout, and each pair of zinc and
silver plates separated by two discs of paper
from the next pair. An extensive arrangement
of this kind may be placed between three thin
glass rods, covered with sealing-wax, and se-
cured in a triangle, by being cemented at each
end into three equi-distant holes in a round
piece of wood ; or the plates may be introduced
into a glass tube previously well dried, and hav-
ing its ends covered with sealing-wax, and
capped with brass ; one of the brass caps may
be cemented -on, before the plates are intro-
duced into the tube, and the other afterwards ;
each cap should have a screw pass through its
centre, which terminates in a hook outside«
This screw serves to press the plates closer to-
^ether, and to secure a perfect metallic contact
with the extremities of the column. The in-
strument constructed in this way is shewn by
fig. 45.

Soon after the invention of the column, Mr.
B. M. Forster discovered that, when a suffi-
ciently extensive series was put together, it$
electric power was sufficient to produce a sort

454 PlillPETl/AL CHIME.

of chime by the motion of a small brass ball
between two bells, insulated, and connected
with the opposite extremities of the column.
He constructed a series of 1500 groups, and by
its agency kept a little bell-ringing apparatus
in constant activity for a considerable length
of time. If the electro-motive power of the
apparatus be really permanent, as it appears to
be, there is no doubt a perpetual motion may
be thus produced. I have contrived an arrange-
ment which is well calculated to ascertain this
point, by excluding to a very considerable ex-
tent, the operation of extraneous causes of in-
terruption, and it at the same time renders the
disposition of the apparatus rather elegant. A
series of from IS to 1600 groups are arranged
in two columns of equal length, which are sepa-
rately insulated in a vertical position by glass
pillars constructed on my new principle of insu-
lation ; the positive end of one column is placed
lo\vest, and the negative end of the other, and
their iipper extremities being connected by a
■wire, they may be considered as one continuous
column. A small bell is situated between each
extremity of the column, and its insulating sup-
port a|id a brass ball is suspended by a thin

PERPETUAL CHlilE. '455

tliread of raw silk, so as to hang midway be-
tweea the bells, and at a very small distance
from each of them. For this purpose the belts
^^re connected, during the adjustment of the
pendulum, by a wire, that their attraction may
not interfere with it; and when this wire is re*-
moved, the motion of the pendulum commences.
The whole apparatus is placed upon a circular
mahogany base, in which a groove is turned to
receive the lower edge of a glass shade with
which the whole is covered.— See Fig. 46.

I have an . apparatus of this kind, cohtain-r
ing only 1200 series, which was constructed
fourteen months since, and has never ceased
to ring, but when removed from one situation
to another, which convenience has rendered
necessary several times during that period*
There was, however, one interval of more than
six months in which it was never disturbed,
and during that time its motion never ceased.
Mr. de Luc has a pendulum which has con<p
stantly vibrated between two balls for more
than two years, and its motion still continues.

If a column of about 1000 series is placed
horizontally, with each of its extremities restr
ling ovl a gold leaf electrometer, as shewn ia

THE ELECTRIC COLUMN.

Fig. 47, the electrometers will eacli diverge;
that connected with the zinc extremity of the
column will be positive, that connected with
the silver extremity will be negative. If the
column be very powerful, the gold leaves of the
electrometers will alternately strike the sides
of the gUss, but this motion is soon stopped by
their slicking to it. It" the simple divergence
only is produced, on touching either extremity
of the column, the electrometer connected with
it closes, and that at the opposite extremity has
it£ divergence increased. This is analogous to
' tiie effect of the Voltaic battery wlien disposed
' in a similar maaner ; but the motion in the co-
lumn is slower^ which {I suppose) arises from
tiie more imperfect {HmducCors of which it it
coni|K«ed.

There ij siMiw causey not yet perfectly dcr
yeloped, that appears to influeoce the power of
tbe column to produce tlie motion of light me*
tallic pendula. In the bell-ringing, apparatus^
for instancia, though the motion always con-
iinues, it in much more rapid at some times tfaad
at others, and the oscillation of the pendulum,
^ugh usually as uni^rm as that produced .by
piedmniam, is on some occasions singularly

THE ElfECTRXC COLUBIV. 457

wild and irregular. The frequency with which
-the gold leaves of an electrometer istrike the
sides of the glass, when connected with an elec-
tric column, is also different at different times:
the variations observed in some experiments of
Mr. de Luc are much more considerable than I
liave yet noticed, with the more powerful co-
lumns of my construction.

Mr. De Luc has proposed, as an interesting
object of enquiry, to make regular observations
on the action of the column, and the numlJer of
oscillations it produces in a given time, at each
observation. For this purpose a single column
of from one to two thousand series may be sup-
ported vertically on an insulating pillar. A
bent wire with a ball at its lower end, is to be
connected with the upper extremity of the co-
lumn, so as to hang parallel with, and ut some
distance from it ; the bail at its lower extremity
being diametrically opposite to a similar ball
that is screwed into the lower cap of the column.
To the same cap there is also screwed a brass
fork with a fine silver wire stretched between
its extremities; this is placed above the ball and
projects farther from the column, so that wfa^i
the pendulum moves towatds the ball it strikes

458 tH]EEt£:ctlllC COLITM^.

this wire first, and receives a kind of jerk, whicH
prevents it from sticking. The pendulum con-
sists of a gilt pith ball suspended by a very fine
silver wire, which hangs parallel to the bent
brass wire, to which it is fastened at top ; the
arrangement is such, that the gilt pith ball would
be always in contact with the brass ball thaib
proceeds from the upper extremity of the co-
lumn, if the apparatus had no electrical power ;
it therefore always returns to this situation^
when, after being attracted to the lower extre-
mity of the column, it discharges its electricity
by striking against the cross silver wire. This
apparatus (which Mr. De Luc has called, " aerial
Electroscope,") is represented, covered with a
glass receiver, by fig. 48.

There appears every reason to believe, that
the action of a well constructed column will be
permanent ; I have several that have been con-
structed nearly three years, and they are still as
active as at first. There is however a precaution
necessary to their constant and immediate ac-
tion ; the two ends of a column should never be
connected by a conducting substance for any
length of time; for, if after such continued com--
munication, it be applied to an electrometer.

THE ELECTRIC COLUMH. 45^

it will scarcely affect it for some time. It is
therefore necessary, when a column is laid by,
that it be placed upon two sticks of sealing-wax
so as to l^eep its brass caps at the distance of
about half an inch from the table or other con-
ducting surface on which it is laid. And if a
column which appears to have lost its action by
laying by, be insulated in this way for a few
days, it will usually recover its full power.

There is another cause of deterioration
which is more fatal ; it is the presence of too

much moisture. If the paper be perfectly dry
it is a non-conductor, and will not therefore
produce any action in the column; but this per-
fect dryness can only be obtained by exposing
the paper to a heat nearly sufficient to scorch it,
and in its dryest natural state I have always
found the paper sufficiently a conductor, even
when, by exposing the paper discs to the heat
of the sun, they have been so dried as to warp
considerably. When the paper is sufficiently
dry, the action of the column continues without
diminution ; and on taking such an apparatus
to pieces after it had been constructed thirty
months, no trace of oxidation was evident on
the zinc plates«

460 THE KLECTEIC COLUJIN.

I have formed some columns of very extra-
oniiiiary power by various novel melhoda of
c'ljiiibination; and have noticed some very sin-
gular phenomena during various experiments on
this subject, iu which I ain still engaged; but
the results are not yet sufficieutly mature foi
publication.

The size of the plates iu the cohinm need
not be large; 1 have constructed them of vari-
ous si/es, and iind no proportionate advantage
hy extending the diameter beyond 5-8tlis of au
inch; they may even be constructed much
smaller than this.

By connecting the extremities of a columtt
of at least 1000 seiies, with the opposite coat-
ings of a Leydenjar, during a period of from
one to five minutes, a charge is usually commu-
nicated to it capable of affording a small but
distinct spark, when tlie discharge is made by a
wire that is not very thick.

The most extensive series I have yet made
experiments with, consisted of twenty thousand
groups of silver, zinc, and double discs of wri-
ting-paper. Its power was considerable. Pith
ball electrometers, with balls of one-fifth of an
inch diameter, and threads of four inches long,

THE ELECTRIC COLUMN. A6l

diverged to the distance of two inches atnd up-
wards, when connected with its opposite extre-
mities. An electrometer at the center was not
affected. When either extremity of the column
was connected with the ground, the electro-
meter attached to that extremity closed, and
the central electrometer opened with the same
electricity, whilst that connected with the op-
posite extremity had its original divergence
considerably increased ; but the electro-motion
was so slow, that some minutes were required to
produce the fiili effect.

By connecting one extremity of the series
with a fine iron wire, and bringing the end of
this near the other extremity, a slight layer of
. varnish being interposed, a series of minute
bright sparks were obtained by drawing the
point of the iron wire lightly over the varnished
surface.

A jar containing fifty square inches of coat-
ed surface was charged by ten minutes contact
with the column, so as to convey a disagreeable
^hock, felt distinctly in the elbows and shoul-
ders, and by some individuals across the breast.

Tlie charge from this jar could perforate
thick drawing-paper, but not a card. It had

46i THE ELECTRIC COLUMK.

just power to fuse one inch of platinawire, of
the five thousandth of an inch diameter.

Notwithstanding the considerable electric
power of this combination, it had not the
shghtest chemical action ; neither the best nor
worst conducting media were affected. Saline
compounds tinged with the most delicate vege-
table colours, were exposed under the most fa-
vourable circumstances to its action, and in
some instances for many days, but no chemical
effect was produced.

It therefore appears indispensably necessary
to the chemical power of the Voltaic apparatus,
I that a Hquid be interposed between each pair of
its plates, whilst for the pure electrical effects,
the only condition appears to be the associatioa
of the two metats ; and the connexion of the
different pairs, by some conductor that does
not interfere with their electro-motive power.

I am now constructing, and have nearly
completed, an addition to the above series of
columns, which will form an arrangement to-
gether of 60,000 groups ; it was not possible for
me to make the experiments with them in time
for this publication; hut my principal inten-
tion is to ascertain if any chemical effect can

THE ELECTRIC COLUMK^. 465

be produced by the most powerful column ; if
it cannot, I think the assigned condition for
chemical action must be considered as establish-
ed : and the determination of that circumstance
will be one step towards a correct theory of
Voltaic electricity.

The discoveries of Franklin displayed the
influence of electricity in the production of the
most magnificent phenomena of nature. That
of Volta has led to the rapid developement of
its connexion with her more silent, but im-
portant processes. Like the power of gravita-
tion, it seems to apply more extensively, the
farther its investigation is pursued. Like that
power too, its nature may for ever escape our
cognizance ; but the contemplation of its effects
may supply new facts calculated to extend the
resources of art, and enlighten our conception
of the infinite variety, and harmony, of natural
phenomena. Such pursuits are amongst the best
sources of intellectual improvement, for they
call into action the highest powers of the mind,
and present a constant succession of interesting
objects for their exercise.

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A6S

APPENDIX^

Various Additions and Corrections. Experiments
on the Electrical Effects evinced after th^ Con-^
tact of Dissimilar Bodies.

1. Sources of Electrical Excitationt.

• •* ■ •

■ I

An useful supplement to the table on the ef»
facts of friction between various bodies, (given
at-page 33,) will be found in the experiments
of Mr. De Luc on the same subject, which are
detailed in the 28th volume of Nicholson's
Journal, p. 1. He obtained a determination of
the electrical effects produced by friction, by
constructing a minute machine, in which vari*
ous bodies were applied to each other as cyiin-^
der and rubber ; the rubber being insulated, and
an iusulated conductor receiving the electricity
of the cylinder, so that the effect produced oei
both could be correctly ascertained. The elec-
tricity of the rubber was always contrary tp
that of the cylinder, but varied with different

bodies..

2»

466

2. Conducting Power.

It is generally stated by writers on this sub-
ject, that hot air is a conductor of electricity,
because flame, or red hot substances destroy
the effect of ipsulation. I have said at page 40,
that the most intensely heated air, if unaccom-
panied by flame, is not a conductor. My rea-
sons for this statement are the following.

1. I do not find that an electrified gold-leaf 1
electronieter, or Leyden jar, is discharged whett J
placed at but a very moderate distance in froittl
of a, large fire, unless the glass becomes so h«|
as to be rendered a conductor.

2. The rays of the sun, concentrated by the
' fqtloB of a lens, dp not coodMi3t electiFicity.

3. Mr. ^ea«d found tha^ ^.«lQ<:^ig«4 el«Cr
tpfK^eter, wbi^n passed quickly ii3i.to ^iid w(. of
af^. oves, »«> hot a» to bioFn oS one. of its b^dl^i^
M^U fenutined eli^ctfi^d. Se« R«ad oq 3p4at^
OfDU$ Electricity, p. 8, 3;c.

3. PbEFABATION of AuALGAlf.

The awalgaai described ait p»ge 52, aoawer*
^xceediiigly well: but I have sincQ m»d« it
with a still less proportion of mercury witb

APPENDIX. 46f

eqtial effects The pro]f>ortion8 may be ttro ot^
of tin, four oz. of zinc, and aeven oi. of liier-'
ci»y. Tlie mercury must be heated to« about
three hundred Farenheit^ before the fused mcM
l^ls ^te added to it When the amalgam ba9
been €igitaif€id untU cod, md finely powdered,
k is to be mixed with hog'is-lard by trituration
m a moFt^r; and should it at silay time becottt^
hard^ more lard ttius^ be added, md t^0 tritam^
tion be repeated.

4. Ratio of Electrical Intensity, As in-

FLUENCED BY FiGURE.

•It ha^ betn stated at pag^ 81, th^t if t\^(»
spheres of^ ifrtifeqtral size ire coiiii^cted togfetjief
atiid electrified, that whir^b i» smallest iv'ill cvijied
the greatest ittteMity, A very- i^tiiifa<5l;6ry de^
nio*'Stratio6' of this falct w^ G0*itrived by MiV
IteLue, aftd requires but' a ^»imple apparstfc^
Two eiFctlar plates of metal, with smooth rotrtid
edges, are* to be provided ; one of thenfe, whi<jlt
1 shrtll eatll A, mafy be tem or tvl^elVe iflohefe dii-t
meter, it is to be supported? in ai< hori^fltal p6*
fiition by an insulating pillar ; the other which I
name B, should not exceed an inch in diameter,

2 H2

46s APPEN'DIX.

and a twelfth of an inch thick, and must he pro-
vided with an insulating handle.

A is to be slightly electri6ed, either posi-
tively or negatively : B is then to be held by
its insulating handle, and applied by its flat
surtace to any part of A; and being then re-
moved in tlie same manner, and applied to the
cap of an electrometer, will indicate by tlie di-
veigence it produces the intensity of that part
A second contact is to be made with some other
portion of A's surface, and on bringing the
small plate again to the electrometer, its diverg-
ence will be cither increased or diminished, and
will consequently indicate the different inten-
sity of two parts of the same conductor. In this
way repeated trials may be made, and it will be
found that the intensity is least at the centre of
the flat surface of A; and that it gradually in-
^jreases towards the circumference, being great-
est at the extreme edge. A similar experiment
may be made by a series of balls regularly de-
creasing in size and connected together by a
wire; the smallest ball will exhibit the most
considerable intensity.

appendix^ 469

5. Electrical Battert.

The practical electrician will (without great
care,) find this essential part of his apparatus a
source of considerable expense, from the fre-
quent fracture of jars by spontaneous explosion.
It may be therefore useful to know, that it is
by no means absolutely necessary to employ jars
all of the same size ; for if their thickness is
nearly the same, and their uncoated rims of
equal extent^ the effect will approximate to the
proportion of the sum of the coated surfaces,
though considerable drfference may exist be-
tween the sizes of the jars. My friend Mn
Crosse has lately communicated to me a very
extensive series of experiments on this subject;
in some of which, the difference between the
size of the combined jars was very considerable,
yet the wire melting power (within the limits
, of their charging capacity,) was very nearly the
proper proportion of the whole coated surface.
Large green glass bottles may be coated for an
electrical battery, and answer well where ap-
pearance is not considered.

appendix.

6. Motion of a Pith Ball, by the dis-
charge OF A Jak.
This experiment, dcBcribed at page 161, i»
by no means a satisfactory indication of the
course of the fluid in the di&chavge, and from
frequent repetition under circumstances of cod*
giderable variation, it appears to me that the
inotion is always produced by electrical attrac-
tion; for I find, that if the bull is placed on the
groove, Q3 directed, at an equal distance from
each of the pointed wires, it will move from th*;
one with which the discharging rod is con-
nected, whether that lie brought in contact with
^popttively charged jar, or one tliat is negatively
charged.* If the discharging rod be kept ia
S(iHt»ct wi(h tjie knob of the jar, the ball rer
niains 3,1 the -^'ue to ^hich it has heeq driven,
Butj if aft^r the cpntact has b^eq made» the

* &fr- Howldf hsA BUM in Nicholspn's Jotirml, vol. x^xif.
!>• ^99i that a piib bgll placed ia a grpove at an equal distance
ftora the ends of the two wires, does not move whtin tha dis-
charge ii pasted froiD one to the othoc ; bat tbc groove h* op-r

ployed " was fitlcd as nearly as could be to the curvature of the
pith ball, and was as deep as half i(s diameter;" consequently
the motion of the ball was prevented by friction, which the
(light charge he employed could not oveiconie.

APFEXDIX. .471

discharging rod is quickly withdrawn^ and then
br6ught in contact and withdrawn ag^in> aeve*
ral times, the ball will move from one wire to
the other, and back again repeatedly, as it would
between tM'O oppositely eledtrified bodies.

7. Pebfobation of Paper by the expansive

Force of the Charge.

The truth of the reasoning applied to Mr«
Symmer's experiment (at page 164,) is confirm-
ed by a variation of it« Let six or eight sheets
of tinfoil be interposed between the leaves of a
quire of paper, so that the pieces of tinfoil are
separated from each other, in every place, by
three or four thicknesses of paper. On passing
a sufficiently strong charge through the quire,
its leaves will be perforated in different placeii,
and each piece of tinfoil will have two indenta-
tions in opposite directions to each other. On
the supposition that this effect is produced by
contrary currents of electricity, it would be ne-
cessary to admit the existence of twice as many
electric fluids as there are pieces of tinfoil ; for
the indentations that point in either direction
are not in a line with each other. But as a fur-
ther proof that it is merely tlie usual expansive

effect of a spark at each interniption of the me-
tallic circuit, the impression on the tinfutl is
greater or less, in proportion to the number of
leaves of paper that separate one piece from an-
other; and when the sheets of tinfoil are sepa-
rated by single sheets of paper only, the effect
Js very trivirtl ; or if the whole thickness is in-
considerable, both the paper and the tinfoil are
aonietimcs perforated in one direction, and that
evidently from the positive to the negative.

8. Prkpabatiox of Elkctrical Cemi srs.
The various cements employed in the con-
■Rtruction of electrical apparatus are formed
principally of resin, with the addition of some
substances to render it more adhesive, and less
brittle. Five pounds of resin, one pound of
bee's-wax, one pound of red ochre, and two
table spoonfuls of plaster of Paris ; when melt-
ed, and well incorporated together, form a very
good cement for general purposes. One that is
well adapted for cementing large Voltaic bat-
teries, and which is cheaper, may be formed of
six pounds of resin, one pound of red ochre,
half a pound of plaster of Paris, and a quarter
of a pint of linseed oil. Other cements in grea.t

variety, more or less fusible, &c. may be formed
by combining the preceding-ingredients in vari-
ous proportions. The ochre and plaster of Paris
should be well dried, and added to the other in*
gredients when they are well melted-

9. Ox THE Electrical Effects exhibited
BT VARIOUS Bodies, after their mutual
Contact.

I have lately made many experiments on thii^
subject, which, by the aid of the new method
of insulation, I M^as enabled to do with a degree
of facility and precision before unknown.

As it was desirable to compare the electri-j
city of the substances under examination, as ob^
tained by their contact with the same body, two
methods were employed. 1 st. That of sifting
them on the cap of a delicate electrometer
through a fine sieve, which was thoroughly
cleansed after each operation. 2d. By bringing
an insulated copper-plate repeatedly in contact
with extensive surfaces of them spread on a dry
sheet of paper ; the copper-plate being brought
in contact with the condenser after every repe-
tition of the touching, until a sufficient charge
was communicated. By each process the effects

increased very considerably when the sub-
stances employed were reduced to a fine pow-
der ; and it was in this way I succeeded in ob-
taining very distinct effects from the alkalies,
by contact with a copper or a silver plate; an
experiment which Sir H. Davy had hefore at-
tempted with great care, but without success.
The pure alkalies were broken into small pieces,
and being placed in an open phial were exposed
for a quarter of an hour to a moderate heat, not
sufficient to fuse the alkali, which was then
quickly reduced to powder in a warm and dry
I mortar, and immediately spread on a dry sheet
of card paper, which for some time will con-
tinue to attract moisture from the alkali, as fast
OS the alkali receives it from the air. The whdc
operation was performed as rapidly as possible.

The greater effect produced in all these cxpe-
limeots by an increased division of the powder,
renders it highly probable that they are merely
Varieties of the usual process of excitation.

The following substances produce negative
electricity when sifted on the cap of an electro-
meter.

Copper, iron, zinc, tin, bismuth, antimony,
nickel, black-lead, lime, magnesia, barytcs,

jstrontite$, alumine, silex^ hxown o^ide of cop-
per, white 03^ide of arsemc, red oxide of leitd,
litharge, white lead, red oxide of iron, acetate
of copper, sulphate of copper, sulphate of soda,
phosphate of soda, carbonate of soda, carbonate
of ammonia, carbonate of potash, carbonate of
lime, muriate of ammonia, common pearl ashes^
boracic acid, benzoic acid, oxalic acid, citric
acid, tartaric acid, cream of tartar, oxymuriate
of potash, pure potash, pure soda, resin, sulphur^
sulphuret of lime, starch, orpiment, &c.

The following substances produce positivfj
electricity when sifted on the cap of an electro-
meter,

Wheat^flour, oatmeal, lycopodiuip, quassia^
powdered cardamom, charcoal of wood, sulphate
of potash, nitrate of pota3h, acetate of lead,
oxide of tin.

Hence it appears, that there are compara-
tively but few substances that appear positively
electrified when sifted through hair, flannel, or
muslin. For,, in erxperiments made with each
of these substances separately, they were found
to produce similar effects.

The following table, exhibits the results of
experiments of contact with a copper-plate;

476 APPENDIX.

the different substances arc arranged in a co-
lumn under the electricity they really obtain^
which is contrary to that of the copper-plate.

POSITIVE. NEGATIVE.

Lime, barytes, strontites^
magnesia, pure soda, pure
potash, common pearl-ashes^
carbonate of potash^ carbonate
of soda^ tartaric acid.

Benzoic acid, boracic acid,
oxalic acid, citric acid> silex>
alumine, carbonate of amnio>
nia, sulphur^ resin.

These experiments were several times re-
peated with uniform results. On the whole,
they by no means favour the idea of natural
electrical energy ; and the result obtained with
sulphur, and with resin, being similar to that
produced by their friction, nearly establishes as
a fact the opinion, that the contact of dissimilar
bodies is in general the primary source of elec-
trical excitation.

10. Medical Applicatiox of Voltaic Elec-
tricity.

The current of electricity produced by a
Voltaic apparatus, has been applied with occa-
sional success in some cases of palsy, rheuma-
tism, rheumatic head-ach, deafness, and opacity
of the cornea. The parts through which it is

APPENDIX. 477

transmitted are moistened with water, and
som«time?s a small piece of gold or silver leaf is
applied ; for, as it has been t)efore stated, the
power of u moderate Voltaic appairatus is not
sufficient to penetrate the dry cuticle. When
applied to the eyes, a moistened piece of sponge
attached to the end of a wire, is a convenient
vehicte for its transmission; and a very mode-
rate power only should be appl^^; for I am
assiiried,; that in some instances bljjid^Q^is h^d
been produced by the injudicious applif?atj.on qf
iB active battery to this ; delicat?;. organ j Tko
size of the plates; is not of so much.consequence
as the, nature of the fluid by which they are ex-
cited; i am decidedly of opipion^ that a strong
aoid mixture should never be employed ; and
t^ie contrary practice will render the action of
the battery more uniform and.pen^anent;; it is
highly prpbable^ that ^^Trth part of muriatic acid
will be found the most useful proportion for
most medical purposes. The practitioner may

derive some useful information on the effect of
different degrees of Voltaic power on the ani-
mal fluids, from Mn Brande's paper in the Phi-
losophical Transactions for 1 809, p- 385| &c.

APPENDIX,

,11. Action of the Sus's HAys on the,,
t F.LECTR1C Column.

*' Mr. De Luc has recently observed, that thS
power of an electric column (as indicated by tlw
ojcillation of a pendulum,) is increased when
the snn slfmes upon it, and his observation has
been corroborated by Mr, Hausmann.* Mr. De
Luc conceived, that the effect did not arisrf,
from the heat of the sun, because he Iiad ol
served that a column put together with discs
paper that bad been thoroughly dried, evinci
Very little power. It is however certain, that It
nioikrate heat does increase the power of the
column, for the bell-ringipg apparatus I have,
is kept in a room where there is rarely a ftre,
and I fiml that it pulsates most slowly in win-
ter; but (fa fire is made in the room, the ring-
ing soon becomes moi*e rapid. I took a column
of a thousand series, and applied it tO' the cap
of a g&M leaf electrometer, wlien the Eenipew-
ture of my j-oom was fifty. Tlie gold leavi
stnuck the sittes of tite glass nine times in sixl
secoiwts. I then, placed the column for ten
notes before a ftrc, where the tliermooFieter n

• Xicholson's Journal, vol, xxxvi. p. 307, &c.

AFP£VDIX. 479

to 85v and it then, on being aipplied to the eleo
trMieter^ oqqasioned the gold leaves to strike
die sides thirty-aevcn times in sixty seconds. It
maA aftenrards removed to another part of the
tooanimtil: it had recovered its original temper;^
ture of 50, and it then occasioned the gold leaves
of thesame electrometer to strike only nine times
in a mioute as at first ; hut on. placing it before
the fire again for ten minutes^ it pfoi&iced
thicty^seven strikings in a minute. Some facts
Skearly- analogous, to this^ whkh demonstrate a
very remarkable influence of temperature on
the. electricity: produced by the contact of dif*
ferent bodies^ and on the action of the Yoltaie
apparatus ; are detailed in a Memoir read before
the French Institute^ Sept 33d. 1811. By J. F.
Dessaignes* See the Journal de Pl^siqae for
18i), vol. bsxiii, p. £30. And at page 417 of
the same volume, a supplement to the Memoir,
in a letter to the editor^ from M. Dessaignes.

12. Production of the Electbical Oxwes.

The oxidation of metals by electricity, de^
scribed at page 1 83, is usually effected l^ ratheir
high charges of a moderate sized battery, and
under such circumstances some of the jars are

APPENDIX.

very frequently broken. I have fouml, that by
increasing the extent of the battery, moremotie-
rate charges are sufficient ; and my friend, Mr.
Crosse, has observed tlic same circumstance in
the employment of hia very extensive and
powerful apparatus.

The law- first noticed by Mr. Brooke with
regard to the fusion of metals, seems also to
obtain when they are oxidated, for I find that .
a battery of 40 square feet of coated surface^ i
charged to 10 grains, will oxidate the same j
quantity of gold wire as a battery of 20 feetj J
charged to 20 grains, and the chance of frac^l
ture is much less with the lowest charge.
:, . itiAVaa by the employment of a very exten-
sive'.battery in thiis way, that the specitneiis of
the Dxides of gold and -copper, with w:hich a
■few. copies of this work arc illustrated, w«re
produced. . -.

. The figures impressed oh glass and paper by
the electrical oxides, vary materially, even when
produced under apparently similar circumstan-
ces, and in a veiy considerable niimber of ex-
perinients, I have never obtained two specie
mens exactly alike.

ERRATA.

Table of Contents, p.*xx> 1. 12, for various part, read various parts.
Introduction, p. 11, 1. 12, for Muschenbrouk, read Muschenbroek.
Page 98, line 9, for their lamina, read thin lamina.

192, line I, for fig. 24, read fig. 25.

24(J, line 23, fm- thinks its, read thinks it.

247, line 9,ybr its form, read its nature.

256, line \A,for iles, read Isles.

417, line 13, for second, read third.

447, line 24 y for Electrio, read Electro.

*^* The various new and improved articles of electrical appa-
ratus described in this work may be obtained, of the most perfect
construction^ at No. 3, Princes Street^ Gaveodish Square^ London.

^4n Account of the Itiitrumentt and Observatinna mint

essential in Meteorology,

AND AS INDICATIONS OF APPROACHING CHANGES

OF WEATHER.

:w If

^^OTJ