,illustration3 ,fig4 #a4 ,fig4 #b4 ,folwell4 ,sc4 ,,an ,,epitome ,,of ,,electricity ,,galvanism4 ,,by ,,two ,,gentlemen ,,of ,,philadelphia4 ,causa latet2 vis est notissima4----,ovid's ,met4 ,b4 ,,iv4 l4 #bhg4 ,,philadelphia3 ,,printed ,,by ,,jane ,,aitken1 ,no4 #ga1 ,,north ,,third ,,street4 #ahji4 ,,district ,,of ,,pennsylvania1 ,,to ,,wit3 ,sidenote3 ,,seal4 ,,be ,,it ,,remembered1 ,that on the fourteenth day of ,december1 in the thirty-fourth year of the ,independence of the ,united ,states of ,america1 ,a4 ,d4 #ahji4 ,jane ,aitken1 of the said ,district1 hath deposited in this ,office1 the ,title of a ,book1 the ,right whereof she claims as ,proprietor1 in the words following1 to wit3-- 8,an ,epitome of ,electricity and ,galvanism4 ,by two gentlemen of ,philadelphia4 ,causa latet2 vis est notissima4--,ovid's ,met4 ,b4 ,,iv4 l4 #bhg40 ,in conformity to the ,act of the ,congress of the ,united ,states1 intituled1 8,an ,act for the encouragement of ,learning1 by securing the ,copies of ,maps1 ,charts1 and ,books1 to the ,authors and ,proprietors of such ,copies1 during the times therein mentioned40 ,and also to the ,act1 entitled 8,an ,act1 supplementary to an ,act1 entitled1 8,an ,act for the encouragement of ,learning1 by securing the ,copies of ,maps1 ,charts1 and ,books1 to the ,authors and ,proprietors of such ,copies1 during the times therein mentioned10 and extending the benefits thereof to the ,arts of designing1 engraving1 and etching historical and other prints40 ,d4 ,,caldwell1 ,clerk of the ,district of ,pennsylvania4 ,,recommendations4 ,having perused this ,epitome1 it appears to me to comprise1 in a concise and perspicuous manner1 the principal discoveries that have been made in ,electricity and ,galvanism1 illustrated with a variety of amusing experiments2 and ,i have no doubt that it will prove useful and entertaining to those who wish for information on these subjects4 ,,john ,m#8,,dowell1 ,professor of ,natural ,philosophy1 and ,provost of the ,university of ,pennsylvania4 ,philad4 ,dec4 #aa1 #ahji4 99 99 99 99 99 ,having read1 at the request of the authors1 a work under the title of 8,an ,epitome of ,electricity and ,galvanism10 ,i am of opinion that it is well calculated for the instruction of youth2 and also that it may prove a useful manual to gentlemen who wish to acquire1 without extensive reading1 a general knowledge of the subjects discussed4 ,,john ,,maclean1 ,professor of ,natural ,philosophy and ,chemistry in the ,college of ,new-,jersey4 ,nassau ,hall1 ,oct4 #bj1 #ahji4 ,the ,epitome of ,electricity appears to me to contain a concise1 but perspicuous and correct statement of the laws of that branch of ,philosophy1 and an interesting collection of facts and experiments1 by which they are illustrated4 ,,jeremiah ,,day1 ,professor of ,mathematics and ,natural ,philosophy4 ,yale ,college1 ,nov4 #be1 #ahji4 ,as the authors could not transmit to ,professor ,,day a copy of the ,epitome of ,galvanism1 without unduly delaying the publication1 his testimonial1 of course1 refers only to the ,epitome of ,electricity4 ,,preface4 ,having denominated the following work an epitome of ,electricity and ,galvanism1 it seems reasonable to request that the reader should keep the nature of our plan in view4 ,if the book do not contain1 on the subjects proposed to be treated1 all that is most important1 let it be condemned4 ,but let not detail be expected where the design requires conciseness4 ,there are some articles under which we were obliged1 either to omit unimportant improvements1 or to occupy several pages in describing them4 ,where1 however1 omissions of any consequence have taken place1 we have endeavoured carefully to refer to the books which will supply them2 so that our work may not only teach the elements and substance of the science1 but direct those who wish to pursue it most extensively--,we particularly regretted that we could not describe a variety of electrometers4 ,short as our work is1 we found it1 notwithstanding1 scarcely practicable to avoid some repetition4 ,in a few instances the historical and scientific parts may be observed1 in a small degree1 to interfere4 ,where history was useful to illustrate experiment1 or experiment composed a part of history1 we did not choose to separate what perspicuity required to be kept together4 ,we hope1 on the whole1 that we do not need more indulgence in this respect1 than we shall readily find1 from those who are fond of the subjects which it was our business and our pleasure to investigate4 ,in making our epitome1 we have often written without a special reference to any book2 sometimes we have abridged the writings of others2 sometimes we have taken paragraphs with the alteration of a few words2 and sometimes we have introduced full quotations4 ,in the latter case1 we have always wished to make a distinct reference to the author quoted2 and in other cases1 we have generally made our acknowledgments where we were particularly indebted4 ,but as our work was begun without any determination to publish it1 we have probably made some selections1 of which we have ourselves forgotten the authors from whom they were taken4 ,of the fairness of a work of this nature1 we suppose there can be no question4 ,johnson1 when speaking of the system of logic published by ,watts1 has made our apology--8,if he owes part of it to ,le ,clerk1 it must be considered1 that no man who undertakes merely to methodise or illustrate a system1 pretends to be its author40 ,as impositions are often attempted1 by soliciting patronage for publications of little value1 we felt the importance of obtaining1 in behalf of our work1 the approbation of competent judges--,the public will admit that it has been obtained2 and the professional gentlemen who have favoured us with it in the most obliging and disinterested manner1 will excuse our offering them this public tender of our grateful acknowledgments4 ,with these remarks we commit our little work to the candour of the public1 conscious of having assiduously laboured to furnish a book which1 though it appeared to us to be much wanted1 had not yet been written or compiled4 ,our views will be fully answered1 if it shall be found well adapted to assist youth in their academical and philosophical studies1 and at the same time1 to afford amusement to men of learning1 and some useful information to gentlemen of leisure4 ,,introduction4 ,,section ,i4 ,electricity as known among the ,ancients4 ,in examining the progress of almost any branch of human knowledge1 curiosity must meet with many repulses4 ,by the time the attention of society is attracted to the accumulation of detached truths1 which compose a science1 it is often impossible to retrace its history4 ,the real origin of most discoveries is obscured by antiquity1 their authors have already sunk into oblivion1 and important improvements are ascribed to different inventors4 ,electricity is however oppressed by few of these difficulties4 ,with the exception of some small discoveries mentioned by ancient authors1 this science derives its origin and all its improvements from the two last centuries4 ,neither is the historian perplexed in giving every invention to its proper author4 ,those who cultivated this science were commonly men of talents and condition2 they pursued it with ability and perseverance2 and either themselves published the result of their observations1 or deposited them in those literary institutions which they found established in their country4 ,the historian of electricity1 therefore1 with no extraordinary exertion of industry or talent1 may fully collect and accurately arrange the materials of his work4 ,on the subject of electricity nothing earlier is on record than the observation of ,thales1 that yellow amber1 when rubbed1 has the property of attracting light bodies4--,so struck was he with this property of amber1 that he imagined it was animated4 ,thales1 the contemporary of ,pythagoras1 was born at ,miletus1 a city of ,ionia1 about six hundred years before ,christ4 ,like all the ,grecian sages1 he travelled into ,egypt2 lived in that country a number of years2 contracted friendships with the priests1 then the depositories of science2 and became deeply skilled in all their mysteries and learning4 ,returning to his own country1 stored with the knowledge of the ,east1 he was ranked as the first of the seven wise men of ,greece1 and became the founder of the ,ionic school1 as ,pythagoras did of the ,italic4 ,it may deserve remark that the same philosopher who is recorded to have observed the first phenomenon in electricity1 is also said to have discovered the cause of thunder and lightning4 ,we shall give to the curious1 the remarkable passage containing this account1 as we find it in ,apuleius1 a learned and eloquent writer of the second century1 while he is rapidly enumerating the discoveries of ,thales4 ,thales ,milesius ex septem illis sapientia memoratis viris facile prcipuus3 fuit enim geometric penes ,grajos primus repertor1 et natur rerum certissimus explorator1 et astrorum peritissimus contemplator1 maximas res parvis lineis reperit1 temporum ambitus1 ventorum flatus1 stellarum meatus1 tonitruum sonora miracula1 siderum obliqua curricula1 ,solis annula reverticula2 idem ,lun vel nascentis incrementa1 vel senescentis dispendia1 vel delinquentis obstacula4 8,thales the ,milesian was decisively the most eminent of the seven famous sages2 for he was the first inventor of geometry among the ,greeks1 the most judicious inquirer into nature1 and the most skilful observer of the stars2 he made great discoveries by small geometrical lines1 the regulation of times and seasons1 the theory of the winds1 the course of the stars1 the wonderful causes of thunder1 the oblique motions of the planets1 the annual revolution of the sun1 the reason of the increase1 decrease1 and eclipse of the moon40#a ,though it is no where expressly affirmed that electricity was discovered by ,thales to be the cause of thunder1 yet when the two facts are placed together1 they will furnish an additional argument to those writers who contend that the ancients knew much more than we are willing to allow them of those shining truths1 which are the peculiar boast of modern ages4 ,nor should this early discovery1 if we could admit it to be real1 excite our surprise4 ,whatever hindrances might impede the progress of the ancients in other branches of knowledge1 from the abstruse nature of the subject1 or the want of necessary helps1 it may rather excite our wonder1 that the effects of electricity should remain so long unobserved4 ,the electric fluid is no local or occasional agent2 it is coeval with the world2 its presence pervades every substance2 it is the principal cause of the grandest scenes in nature1 and its operations can hardly fail to show themselves wherever bodies are concerned4 ,from the time of ,thales1 there is a chasm in the history of electricity for three hundred years4 ,indeed1 natural science of all kind appears to have languished1 during this period4 ,theophrastus1 who flourished #cga years before ,christ1 the disciple and successor of ,aristotle1 and he to whom the learned are indebted for the preservation of his master's works1 then adds one more fact to the history of electricity4 ,in his treatise on stones1 after speaking of the attractive power of amber1 found on the coast of ,liguria1 he goes on to ascribe the same properties to the lapis lyncurius1 the same substance now called tourmaline4 8,it possesses 7says he7 an attractive power like amber3 and as they say attracts not only straws and leaves1 but copper also1 and iron1 if in small particles4#b0 ,these two discoveries of ,thales and ,theophrastus are all1 on the subject of electricity1 that industry has been able clearly to collect from the barren records of antiquity4 ,pliny indeed has observed that 8amber being rubbed with the fingers1 and having thereby become warmed1 attracts to itself straws and dried leaves1 in the same manner as the magnet does iron40 ,he also attributes to the ,lyncurium the same properties4--,solinus and ,priscian1 also1 make similar statements4 ,but as these are no more than what ,thales and ,theophrastus had remarked before1 they are to be considered only as a repetition of what the preceding writers had made known1 not as any addition to the information possessed on this subject4 ,in like manner it might be mentioned that ,aristotle1 ,pliny1 ,oppian and ,claudius1 were fully acquainted with the benumbing effects produced by the touch of the ,torpedo2 but as they do not appear to have suspected that these effects were produced by electricity1 they cannot be considered as communicating or possessing any additional knowledge in regard to this powerful agent4#c ,on subjects which regard taste1 or which address themselves to the imagination1 on poetry1 eloquence and the fine arts1 it is to the ancients we are to look for information and the models of perfection4 ,but on the various branches of knowledge which depend on observation1 on experiment1 on investigation1 which comprehend all the parts of mechanical philosophy1 the philosophers of antiquity afford little that is either new or just4 ,hurried away by the vivacity of their genius1 which their peculiar complexion invited them to cultivate1 and the particular circumstances of the age were calculated to inflame1 they investigated facts1 not that by accumulated discoveries they might lay the foundation of solid science1 but so far only as they served to support or illustrate some favourite hypothesis4 ,aristotle1 to whose profound and elevated genius we are accustomed to turn for satisfactory information on so many other subjects1 affords no remarks on electricity1 and little worthy of observation on most of the branches of natural science4 ,one1 who on this point has a right to speak1 observes4--8,that though there are several very sublime questions in his physics1 which he clears up in a very masterly way1 yet the main1 the gross of the work is good for nothing1 infelix operis summa4#d0 ,from the time of ,theophrastus till the beginning of the #agth century of the christian ra1 there is no unequivocal evidence that in the science of electricity any discovery or improvement was made1 except the solitary and unimportant fact that jet1 and perhaps agate1 is endued with the same power as amber1 of attracting and repelling light bodies4--,nor is it ascertained by whom1 or at what particular period1 this fact was added to the slender stock of electrical knowledge which was then possessed4 ,and thus it appears that for the space of about #aijj years1 the part of philosophy1 of which we trace the history1 was nearly stationary4 ,,section ,,ii4 ,electricity as known to the ,moderns4 ,having seen1 in the preceding section1 the very limited knowledge of electricity possessed by the ancients1 we now come to give an account of what may properly be called its real origin1 and to trace its progress to the present day4 ,in doing this1 we shall be careful to note all the original authors who have touched upon this subject2 and to exhibit most of their discoveries4 ,we believe it to be generally the case1 that1 in the earlier periods of a science1 the mind is curious to observe the gradual developement of principles1 and the gradual increase of facts1 however unimportant these facts may afterwards appear4 ,but as the science progresses1 as the ground widens and observations multiply1 this curiosity proportionably abates1 and we require of the historian selection rather than detail4 ,however minute1 therefore1 the history of the first stages of this branch of philosophy must be1 the after periods will exact only a careful selection of those more prominent discoveries1 which show the advances of the science and mark its gradations4 ,during the sixteenth century1 the phenomena of magnetism having engaged the study of philosophers1 they were naturally led to bestow some attention on substances which appeared to possess similar properties with the load-stone4 ,indeed1 it was not till after #agbi that the idea was entertained1 that electricity was a distinct fluid1 or any thing else than a certain property of bodies1 resembling magnetism2 nor was any other meaning affixed to the word1 than a power of attracting and repelling4 ,fifteen centuries having elapsed from the time of ,theophrastus1 ,william ,gilbert1 physician to king ,james ,i1 in #afjj published a latin work1 entitled1 ,de ,magnete1 magnetesque corporibus1 in which1 having discussed the phenomena of magnetism1 he1 towards the close1 relates a great variety of electrical experiments4 ,the principal merit of this philosopher is1 that he greatly augmented the list of electrical substances1 noted the bodies on which electrics can act1 and remarked several circumstances relating to the manner of their action4 ,he enumerates1 as having the power of attracting light bodies1 ,diamonds1 ,saphirs1 ,carbuncles1 ,iris1 ,opals1 ,amethysts1 ,beryl1 ,crystal1 ,bristol-stones1 ,sulphur1 ,mastick1 ,hard ,wax1 ,hard ,rosin1 ,arsenic1 ,sal-gemm1 ,rock-,alum1 common-glass1 ,stibium1 or glass of ,antimony4 ,he also observed that the influence of these substances extended1 not only to leaves and straws1 but to all matter which was not extremely rare4 ,friction1 he says1 is1 in general1 necessary to excite the virtue of these substances2 and the most effectual friction1 he affirms1 is that which is light and quick4 ,electrical appearances1 he asserts1 were strongest when the air was dry1 and the wind north or east1 at which time electrics would act ten minutes after excitation4 ,the simple experiments of this philosopher were mostly made with long thin pieces of metal1 and other substances freely suspended on their centers1 to the extremities of which he presented the electrics he had excited4 ,the phenomena of magnetism were accounted for1 in the time of ,gilbert1 by means of emanating effluvia1 and he applies the same theory to the explanation of electrical attraction1 imagining it to be performed in the same manner as the attraction of cohesion4 ,two drops of water1 rush together when they are brought into contact1 and electrics1 he says1 are virtually brought into contact by means of their effluvia4 ,effluvia illa tenuiora concipiunt et amplectuntur corpora1 quibus uniuntur1 et electris tanquam extensis brachiis1 et ad fontem propinquitate1 invalescentibus effluviis1 deducuntur4 8,those subtle effluvia continually embrace certain bodies1 to which they are united1 as it were by their extended electric arms2 and the effluvia prevailing1 the bodies are drawn to the contiguous source of the effluvia40 ,gilbert has been stiled the father of modern electricity2 and when we consider how little was known of the subject prior to his time1 and the merit that belongs to himself1 not only from his own experiments1 but also from turning the attention of philosophers to a new branch of natural science1 we cannot but allow that he eminently deserves the title4 ,cabeus followed ,gilbert1 but did little else than add to the list of electrics1 wax1 gum elemi1 ,gum guaiaci1 ,pix ,hispanica and ,gypsum4 ,thirty years after the publication of ,gilbert's work1 the celebrated ,sir ,kenelm ,digby1 in his 8,treatise of the nature of ,bodies10 touches upon electricity3 but as the age in which he lived was still busying itself with the hypothetical philosophy of ,aristotle1 so this philosopher in what he says of electricity1 appears to be rather amusing himself in inventing theories1 to explain the manner in which electric attraction is performed1 than in advancing the science by new facts and experiments4 ,his theory of electric attraction is1 however1 of some celebrity3 it was allowed by his contemporary ,des ,cartes1 in his principles of philosophy1 and was embraced by the chief writers of his age2 though it does not differ essentially from that of ,gilbert4 8,attraction 7says he7 is made by a tenuious emanation1 or continued effluvium1 which after some distance retracteth into itself1 as is observable in drops of syrups1 oil and seminal viscosities1 which spun at length1 retire to their dimensions4 ,now these effluviums advancing from the body of an electric1 in their return do carry back the bodies whereon they have laid hold1 within the sphere or circle of their continuities2 and these they do not only attract1 but with their viscous arms1 hold fast a good while after4 ,and if any shall wonder why these effluvium issuing forth1 impel and protrude not the straw before they can bring it back2 it is because the effluvium passing out in a smaller thread1 and more enlengthened filament1 stirreth not the bodies interposed2 but returning into its original1 falls into a closer substance and carrieth them back into itself40 ,sir ,thomas ,brown succeeded to ,sir ,kenelm ,digby4 ,in his 8,inquiry into ,vulgar ,errors10 this inquisitive philosopher has a chapter on electricity1 in which he corrects some mistakes into which his predecessor had fallen1 adds some new experiments of his own1 and gives us a summary view of the state of electrical knowledge at the time he wrote4 8,by electrical bodies1 7says he7 ,i understand not such as are metallical1 mentioned by ,pliny1 and the ancients2 for their electrum was a mixture made of gold1 with the addition of a fifth part of silver2 a substance now as unknown as true ,aurichalcum1 or ,corinthian brass1 and set down among things lost by ,pancirollus4 ,nor by electric bodies do ,i conceive such only as take up shavings1 straws1 and light bodies1 in which number the ancients only placed ,jet and ,amber2 but such as conveniently placed unto their objects attract all bodies palpable whatsoever4 ,i say conveniently placed1 that is1 in regard of the object1 that it be not too ponderous1 or any way affixed2 in regard of the agent1 that it be not foul or sullied1 but wiped1 rubbed1 and excitated2 in regard of both1 that they be conveniently distant1 and no impediment interposed4 ,i say1 all bodies palpable1 thereby excluding fire1 which indeed it will not attract1 nor yet draw through it2 for fire consumes its effluxions by which it should attract40 ,brown augmented the list of electrics1 and found attraction not only in simple bodies1 but in such also as were compounded4 ,he observed1 that the attractions of bodies were different4 ,resinous bodies1 he says1 attract most vigorously1 and 8good hard wax so powerfully1 that it will convert the needle almost as actively as the load-stone4 ,gums easily dissolved in water1 draw not at all2 no metal attracts1 nor wood1 though never so hard and polished4 8,glass1 7he says17 attracts but weakly1 though clear3 and some slick stones1 and thick glasses but indifferently40 ,these experiments on the electricities of bodies1 he performed by means of a needle1 8settled freely upon a well pointed pin1 so that the electrics might be applied to it without disadvantage20 he tried them also in straws and paleous bodies1 powders of wood and iron1 in gold and silver foliated4 ,how the attraction of electrics is performed1 he acknowledges is not easily determined2 though1 he says1 8that it is performed by effluviums is plain1 and granted by most2 for electrics will not commonly attract1 except they grow hot and perspirable4 ,for if they be foul and obnubilated1 it hinders their effluxion2 nor if they be covered1 though but with linen or sarsenet1 or if a body be interposed1 for that intercepts the effluvium4 ,if also a powerful and broad electric of wax or anime be held over fine powder1 the atoms or small particles will ascend most numerously unto it2 and if the electric be held unto the light1 it may be observed that many thereof will fly1 and be as it were discharged from the electric to the distance sometime of two or three inches4 ,which motion is performed by the breath of the effluvium issuing with agility2 for as the electric cooleth1 the projection of the atoms ceaseth40 ,sir ,francis ,bacon in his 8,physiological ,remains10 has inserted a catalogue of bodies attractive and not attractive2 but he differs in nothing worth mentioning from his predecessors4 ,mr4 ,boyle1 who so eminently distinguished himself in the latter part of the seventeenth century1 was led by the study of chemistry1 to give some attention to electricity4 ,he enlarged the catalogue of electrics2 and noticed some circumstances relating to electrical attraction1 which had escaped former philosophers4 ,the electrical properties of bodies he found were increased by wiping and warming them1 before they were rubbed4 ,bodies of all kinds1 he observed1 were indiscriminately attracted2 and this attraction he supposed took place in vacuo as well as in the open air4 ,hitherto the attraction of electrics was the single phenomenon noticed by philosophers4 ,gilbert1 even when remarking on the characteristic differences between magnetism and electricity1 observes1 that in magnetism there is both attraction and repulsion1 but in electricity only the latter1 and not the former4#e ,boyle made an approach to the discovery of this fact of electrical repulsion1 by remarking that light bodies1 as feathers c4 would cling to his fingers and other substances1 after they had been attracted by electrics4 ,otto ,guericke1 the celebrated inventor of the air pump1 who was contemporary with ,mr4 ,boyle1 improved the science much farther4 ,he made use of a sulphur globe1 whirled on an axis1 much in the same way with our present glass globes4 ,he could thus excite the electricity with greater power1 and try all the experiments of his predecessors to greater advantage4 ,his was the full discovery of electric repulsion4 8,a body once attracted1 he remarks1 by an excited electric1 is repelled by it1 and not attracted again till it has been touched by some other body40 ,in this manner he kept a feather a long time suspended in the air1 above his sulphur globe4 ,he also made another remarkable discovery1 which has since been very generally overlooked2 namely1 that a feather1 when repelled by an excited electric1 always keeps the same face towards the body which repels it1 as the moon does to the earth4 ,the electric light was probably observed by ,mr4 ,boyle in the diamond2 but ,otto ,guericke saw it more clearly in the excitation of his glass globe1 and also heard the hissing sound which attends it4 ,as this light1 however1 was exhibited to ,dr4 ,wall1 about the same time1 in a much finer manner1 we shall rather give his account of it4 8,i found1 says he1 upon swiftly drawing a well polished piece of amber in the dark1 through a piece of woollen cloth1 and squeezing it pretty hard with my hand1 a prodigious number of little cracklings were heard1 and every one of them produced a flash of light2 but when the amber was drawn gently and slightly through the cloth1 it produced only a light1 but no crackling2 but by holding one's finger at a little distance from the amber1 a large crackling is produced1 with a great flash of light succeeding it4 ,and1 what to me is very surprising1 upon its eruption1 it strikes the finger very sensibly1 wheresoever applied1 with a push or puff1 like wind4 ,this light and crackling seems1 in some respects1 to represent thunder and lightning4 ,sir ,isaac ,newton is the next in chronological order1 who made any discovery of importance4 ,he first observed that the electrical attraction and repulsion1 penetrated through glass4 ,it cannot but be lamented1 that this great philosopher1 among the vast variety of important subjects which he cultivated and improved1 had not applied himself to electricity1 with greater assiduity4 ,mr4 ,hawksbee1 in #agji1 wrote a treatise on electricity1 and distinguished himself by discoveries which far surpassed those of his predecessors4 ,besides a variety of new facts in regard to attraction and repulsion1 he observed the electric light distinctly1 and made some delicate and curious experiments on its nature4 ,the electric light was considered by ,mr4 ,hawksbee1 as well as by all those who first observed it1 as a species of phosphorus1 and all the experiments made1 were conducted under this impression4 ,holding an exhausted globe within the effluvia of an excited one1 he observed a light in the former1 which presently died away1 if it was kept at rest2 but was revived1 and continued very strong1 if the exhausted globe was kept in motion4 ,the greatest electrical light he produced1 was when he enclosed an exhausted cylinder within one not exhausted1 and excited the outermost of them1 putting them both in motion4 ,he observed no difference1 whether the globes were turned in the same direction1 or otherwise4 ,he made many experiments to shew the extreme subtlety of the electric light1 and found out a method of rendering opaque bodies transparent4 ,he lined with sealing wax more than half the inside of a glass globe1 and having exhausted it1 put it in motion4 ,on applying his hand to excite it1 he saw the shape and figure of all the parts of his hand distinctly and perfectly1 on the concave superficies of the wax within4 ,it was as if there had been pure glass1 and no wax interposed between the glass and his hand4 ,this lining was in many places the eighth of an inch thick2 and in some places where it did not adhere so closely to the glass as in others1 yet the light on these appeared just as on the rest4 ,he repeated these experiments with pitch instead of sealing wax1 and with equal success4 ,it is to be regretted that these facts have not engaged more of the attention of philosophers4 ,after the death of ,mr4 ,hawksbee1 twenty years elapsed before any farther improvements were made4 ,the great discoveries which were then making in other branches of philosophy1 by ,sir ,isaac ,newton1 so absorbed the public attention1 that electricity was entirely overlooked4 ,mr4 ,grey1 after this long interval1 took up the subject1 and by his discovery of the distinction between electrics and non-electrics1 formed an important epoch in the history of electricity4 ,an account of this discovery of ,mr4 ,grey1 is thus abridged from the ,philosophical ,transactions1 by ,dr4 ,priestley4 8,in the month of ,february #agbi1 ,mr4 ,grey1 after some fruitless attempts to excite an electric power in metals1 recollected a suspicion he had for some time entertained1 that as a glass tube1 when excited in the dark1 communicated its light to various bodies1 it might at the same time possibly communicate to them an electricity2 that is1 a power of attracting light bodies2 which1 as yet1 was all that was understood by the word electricity4 ,for this purpose he provided himself with a glass tube1 three feet five inches long1 and near one inch and two-tenths in diameter4 ,to each end was fitted a cork2 to keep the dust out when the tube was not in use4 ,his first experiments were made with a view to determine whether a tube would attract equally well with the ends shut1 as with them open4 ,in this respect there was no difference2 but he found that the corks attracted and repelled light substances1 as well1 and rather better than the tube itself4 ,he then fixed an ivory ball upon a stalk of fir about four inches long1 and thrusting the end of the stalk into one of the corks1 he found the ball endowed with a strong attractive and repulsive virtue4 ,this experiment he repeated in many different ways2 fixing the ball upon long sticks1 and upon pieces of brass and iron wire1 always with the same success2 but he constantly observed1 that the ball at the end attracted more vigorously1 than that part of the wire nearest the tube4 8,the inconvenience of using long wires in this manner1 put ,mr4 ,grey upon trying whether the ball might be suspended by a pack-thread1 with a loop on the tube1 with equal success2 and the event fully answered his expectation4 ,having thus suspended bodies of the greatest length he conveniently could1 to his tube1 he ascended a balcony #bf feet high1 and fastening a string to his tube1 found that the ball would attract light bodies on the ground below4 ,this experiment succeeded in the greatest heights to which he could ascend2 after which1 he attempted to carry the electricity horizontally4 ,his first attempt miscarried1 because he suspended his line1 which was intended to carry the electricity horizontally1 by a pack-thread2 and thus the fluid got off from it2 but though ,mr4 ,grey knew this was the case1 he could not at any time think of any method to prevent it4 8,on the #cjth ,june #agbi1 ,mr4 ,grey paid a visit to ,mr4 ,wheeler1 in order to give him a specimen of his experiments2 but told him of the unsuccessful attempt he had made to carry the electric fluid horizontally2 ,mr4 ,wheeler proposed to suspend the conducting line by silk instead of pack-thread4 ,for this advice he could give no reason1 but that the silk thread was smaller than the other2 however1 with it they succeeded perfectly well4 ,their first experiment was in a matted gallery at ,mr4 ,wheeler's house1 on the #b;d of ,july #agbi4 ,about four feet from the end of the gallery they fastened a line across the place4 ,the middle of this line was silk1 the rest pack-thread4 ,over the silken part they laid one end of the conducting line1 to which was fastened the ivory ball1 and which hung down about nine feet below the line stretched across the gallery4 ,the conducting line was about #hj #a-b feet in length1 and the other end of it was fastened by a loop to the electric tube4 ,upon rubbing the tube1 the ivory ball attracted and repelled light substances1 as the tube itself would have done4 ,they next contrived to return the line1 so that the whole length of it amounted to #adg feet2 which also answered pretty well4 ,but suspecting that the attraction would be stronger1 without doubling or returning the line1 they made use of one carried straight forward1 for #abd feet2 and as they expected1 found the attraction in this manner1 stronger than when the lines had been doubled4 ,thus they proceeded with their experiments2 still adding more conducting line1 till at last their silk string broke with the weight4 ,this they endeavoured to supply1 first with a small iron wire1 and then with a brass one4 ,the result of these experiments1 however1 soon convinced them1 that the silk refused to conduct the electric fluid1 not on account of its smallness1 as they had supposed1 but on account of some difference in the matter4 ,the wires were smaller than the silk threads1 yet the electricity was effectually carried off by them4 ,they had recourse1 therefore1 to thicker lines of silk2 and thus conveyed the electric matter to the distance of #gfe feet3 nor did they perceive the virtue to be at all diminished by the distance to which it was carried40 ,in the manner in which silk was found to be a non-conductor1 the same quality was also discovered in many other substances1 such as hair1 rosin1 c4 ,mr4 ,grey also made many electrical experiments on fluids and animal bodies4 ,as he knew no other method of trying whether bodies were electrified or not1 but by making them raise light bodies placed under them1 to put a fluid in this situation1 he dissolved soap in ,thames water1 and suspending a tobacco pipe1 he blew a bubble at the head of it2 and bringing the excited tube near the small end1 he found the bubble to attract leaf brass to the height of two and of four inches4#f ,he contrived afterwards1 by a curious experiment to shew the effects of electricity upon water1 in a more satisfactory manner4 ,he filled a small cup with water higher than the brim1 and when he had held an excited tube over it1 at the distance of about an inch or two1 he says1 that if it were a large tube there would first arise a little mountain of water from the top of it1 of a conical form2 from the vertex of which there proceeded a light1 very visible when the experiment was performed in a dark room1 and a snapping noise almost like that which was made when the finger was held near the tube1 but not quite so loud1 and of a more flat sound4 ,upon this1 says he1 immediately the mountain1 if ,i may so call it1 falls into the rest of the water1 and puts it into a tremulous and waving motion4 ,this experiment he repeated in the sun-shine1 when he perceived small particles of water thrown from the top of the mountain2 and sometimes a fine stream of water would arise from the vertex of the cone1 in the manner of a fountain1 from which issued a fine stream or vapour1 whose particles were so small as not to be seen4 ,this last circumstance he inferred1 from the under side of the tube being wet4 ,and by after experiments1 he found that though the cylinder of water does not always rise1 yet that there is always a stream of particles thrown on the tube1 and sometimes to such a degree as to become visible4 ,in ,april #agcj1 ,mr4 ,grey suspended a boy on hair lines1 in a horizontal position1 just as all electricians had before been used to suspend their hempen lines of communication1 and their wooden rods2 then bringing the excited tube near his feet1 he found that leaf brass was attracted by his head1 with a vigour sufficient to raise it to the height of eight1 and sometimes of ten inches4 ,when the leaf brass was put under his feet1 and the tube brought near his head1 the attraction was small2 and when the leaf brass was brought under his head1 there was no attraction at all4 ,while the boy was thus suspended1 ,mr4 ,grey amused himself with making the electricity operate on several parts of his body at the same time1 and at the ends of long rods1 which he made him hold in his hands1 and in diversifying the experiments several other ways4 ,mr4 ,grey continued to study electricity as long as he lived2 and besides giving a set of fanciful experiments1 by which he supposed he had discovered a perpetual attractive power in electrics1 he1 a little while before his death1 entered on another course by which he hoped he should be able to astonish the world with a new sort of planetarium4 8,i have lately made 7says he7 several new experiments upon the projectile and pendulous motions of small bodies by electricity2 by which small bodies may be made to move about large ones1 either in circles or ellipses1 and those either concentric or excentric to the centre of the large body about which they move1 so as to make many revolutions about them4 ,and this motion will constantly be the same way that the planets move round the sun1 viz4 from the right hand to the left1 or from west to east4 ,but these little planets1 if ,i may so call them1 move much faster in their apogean1 than in the perigean part of their orbits2 which is directly contrary to the motion of the planets round the sun40 ,the manner in which these experiments were made1 as delivered by him on his death-bed to ,dr4 ,mortimer1 was as follows3 8,place a small iron globe 7said he7 of an inch or an inch and a half in diameter1 on the middle of a circular cake of rosin1 seven or eight inches in diameter1 greatly excited2 and then a light body1 suspended by a very fine thread1 five or six inches long1 held in the hand over the centre of the cake1 will1 of itself1 begin to move in a circle round the iron globe1 and constantly from west to east4 ,if the globe is placed at any distance from the centre of the circular cake1 it will describe an ellipse1 which will have the same excentricity as the distance of the globe from the centre of the cake4 ,if the cake of rosin be of an elliptical form1 and the iron globe be placed in the centre of it1 the light body will describe an elliptical orbit1 of the same excentricity with the form of the cake4 ,if the globe be placed in or near one of the foci of the elliptical cake1 the light body will move much swifter in the apogee1 than in the perigee of its orbit4 ,if the iron globe is fixed on a pedestal an inch from the table1 and a glass hoop1 or a portion of a hollow glass cylinder excited1 be placed round it1 the light body will move as in the circumstance mentioned above1 and with the same varieties40 ,he said1 moreover1 that the light body would make the same revolutions1 only smaller1 round the iron globe placed on the bare table1 without any electrical substance to support it3 but he acknowledged that he had not found the experiment succeed if the thread was supported by any thing but the human hand2 though he imagined any other animal substance would have answered the purpose4 ,these experiments occasioned a great deal of speculation4 ,dr4 ,mortimer was the only person who was able to repeat them with success1 and he only when nobody but himself was the witness4 ,it was therefore generally supposed that both he and ,mr4 ,grey had been deceived3 but from some experiments to be related hereafter1 it seems probable that the success of ,mr4 ,grey and ,dr4 ,mortimer was owing to their having performed their experiments with candle-light2 and the failure of the others to their having attempted them by day light4 ,notwithstanding which1 it is more than probable that ,mr4 ,grey has been deceived in a number of particulars2 for no motion can be performed by an artificial excitation of the electric fluid1 but what is attended with much irregularity4 ,not long after the discovery of ,mr4 ,grey of the difference between conductors and non-conductors1 ,mr4 ,du ,fay1 a ,french philosopher1 7for the 8spirit of electricity0 had passed from ,england to ,france17 discovered1 what was afterwards called positive and negative electricity2 or as he denominated them the vitreous and resinous electricities4 8,chance 7says he7 has thrown in my way a principle1 which casts a new light on the subject of electricity4 ,the principle is1 that there are two distinct kinds of electricity1 very different from one another1 one of which ,i call vitreous1 and the other resinous electricity4 ,the first is that of glass1 rock crystal1 precious stones1 hair of animals1 wool and many other bodies4 ,the second is that of amber1 copal1 gum lac1 silk thread1 paper1 and a vast number of other substances4 ,the characteristics of these two electricities is1 that they repel themselves and attract each other4 ,thus a body of the vitreous electricity repels the vitreous1 and on the contrary attracts all those of the resinous4 ,the resinous also repels the resinous and attracts the vitreous4 ,this discovery of ,mr4 ,du ,fay was made in consequence of his casually observing1 that a piece of leaf gold1 repelled by an excited glass tube1 and which he meant to chace about the room with a piece of excited gum copal1 instead of being repelled by it1 as it was by the glass tube1 was eagerly attracted4 ,this doctrine of two different electricities1 produced by exciting different substances1 was dropped after ,mr4 ,du ,fay2 and even this philosopher himself adopted at last the opinion of ,dr4 ,franklin that the two electricities differ only in degree1 and that the stronger attracts the weaker4 ,although many of the experiments of ,mr4 ,grey led directly to it1 yet to the ,french philosopher just mentioned1 belongs the merit of first drawing the electrical spark from the human body4--,and we cannot forbear remarking1 in this place on the regular and progressive advances which the human mind makes in the investigation of science4 ,electrical attraction was1 for a long period1 the single phenomenon known to philosophers4--,repulsion was then observed to be also a property of electrics4--,in the investigation of these we read of the accidental discovery of the electric light4--,to this naturally succeeded1 ,mr4 ,grey's distinction between conductors and non-conductors2 and then the difference between vitreous and resinous electricities by ,mr4 ,du ,fay4 ,we shall have to remark in the sequel of this history1 how each succeeding fact and invention grew out of that which immediately preceded it4 ,the knowledge of electricity did not stop in ,france4 ,the ,germans began to labour in the same field2 and with laudable success4 ,their success arose chiefly from the improvements they made in the electrical apparatus4 ,the simple experiments of ,gilbert1 and the early electricians1 were made by exciting a piece of amber or sulphur4 ,mr4 ,boyle found the electric power increased by smoothing the surface of bodies4 ,otto ,guericke made his experiment with a globe of sulphur1 formed by melting that substance in a hollow globe of glass1 and afterwards breaking the glass from off it1 little supposing that the glass itself would better have answered his intention4 ,in #agji ,mr4 ,hawksbee first observed the great electric power of glass4 ,he used a glass globe1 which he mounted upon an axis1 whirling it round1 and at the same time applying his hand to it4 ,he also1 to increase the power1 inclosed an exhausted cylinder within another1 exciting the outermost4 ,after ,mr4 ,hawksbee's death1 the glass globe was laid aside1 and his successors confined themselves to the use of tubes4 ,mr4 ,boze1 professor of philosophy at ,wittemburgh1 in #agdb returned to the use of the globe4 ,he also added a prime-conductor of tin or iron1 supported1 at first1 by a man standing on cakes of rosin1 but afterwards by silken lines extended horizontally1 under the conductor4 ,mr4 ,winckler1 of ,leipsic1 to excite the globe1 substituted a cushion1 instead of the hand4 ,the electrical star and the electrical bells were also the invention of the ,german philosophers4 ,dr4 ,desagulier1 likewise1 assisted electricians by some electrical terms4 ,he first gave to bodies conveying electricity the name of conductors2 and those in which electricity may be excited by heating and rubbing he calls electrics per se4 ,in #agde1 the attention of ,dr4 ,watson being attracted by the account of the ,germans having fired spirits of wine1 he applied himself to electricity with much assiduity1 and made many valuable and curious discoveries4 ,but though his improvements were considerable1 and such as at another time would have excited interest1 they were now lost amid the surprise occasioned by the most remarkable discovery that had yet been made in the whole science4 ,this was the accumulation of the electric matter in glass bottles1 and the method of giving the electric shock4 ,the merit of this discovery belongs to ,mr4 ,cuneus1 a native of ,leyden1 from whence it derives its name of the ,leyden phial4#g 8,m4 ,muschenbroeck1 professor in the university in that city1 observing with his friends1 that electrified bodies1 exposed to the common atmosphere1 which is always replete with conducting particles of various kinds1 soon lost their electricity1 and were capable of retaining but a small quantity of it1 imagined1 that were the electrified bodies terminated on all sides by original electrics1 they might be capable of receiving a stronger power1 and retaining it a longer time4 ,glass being the most convenient electric for this purpose1 and water the most convenient non-electric1 they first made their experiments with water in glass bottles2 but no considerable discovery was made1 till the professor1 or ,mr4 ,cuneus1 happening to hold his glass vessel in one hand1 containing water1 which had a communication with the prime-conductor by means of a wire1 and with the other hand disengaging it from the conductor 7when he imagined the water had received as much electricity as the machine could give7 was surprised by a sudden shock in his arms and breast1 which he had not in the least expected from the experiment40 ,wonder is the effect of ignorance1 and ignorance begets credulity2 but when wonder and credulity are coupled with terror and surprise1 we must look for a strange and mishapen progeny4 ,the exaggerated accounts of those who first experienced the electric shock cannot but raise a smile2 especially as we may ascertain their real sensations by like experiments upon ourselves4 ,mr4 ,muschenbroeck1 in a letter to ,mr4 ,reaumur1 written soon after the ,leyden discovery1 says2 that he felt himself struck in his arms1 shoulders1 and breast1 so that he lost his breath2 and was two days before he recovered from the effects of the blow and the terror4 ,he adds1 he would not take a second shock for the kingdom of ,france4 ,mr4 ,allamand who tried the experiment with a common beer glass1 affirmed1 that he lost the use of his breath for some moments2 and then felt so intense a pain along his right arm1 that he at first apprehended ill consequences from it1 though it soon after went off without any inconvenience4 ,but the terror of ,mr4 ,winckler of ,leipsic exceeded that of all the rest4 ,the first time he tried the ,leyden experiment1 he says1 he found great convulsions by it in his whole body3 and that it put his blood into great agitation2 so that he was afraid of an ardent fever1 and was obliged to use refrigerating medicines4 ,he also felt a heaviness in his head1 as if a stone lay upon it4 ,twice1 he says1 it gave him a bleeding at the nose1 to which he was not inclined2 and that his wife 7whose curiosity1 it seems1 was greater than her fears7 received the shock only twice1 and found herself so weak1 that she could hardly walk2 and that a week after1 upon recovering courage to receive another shock1 she bled at the nose after taking it only once4 ,mr4 ,boze1 with other philosophers were1 however1 far from participating in the cowardice of the professor of ,leipsic4 ,they gathered resolution to receive a number of electric shocks1 as strong as they could be given4 ,mr4 ,boze1 indeed1 as ,dr4 ,priestley remarks1 8with a heroism worthy of ,empedocles1 wished he might die by the electric shock1 that the account of his death might furnish an article for the memoirs of the ,french academy of sciences4 ,but1 adds the same author1 it is not given to every electrician to die the death of the justly envied ,richman40 ,this experiment1 calculated1 not only to engage the investigation of the philosopher1 but to raise the vulgar amazement1 brought electricity into general notice4--,from this time every body was eager to see and to feel this prodigy of nature2 and numbers of persons1 travelling over ,europe1 gained a livelihood by exhibiting its appearances and effects4 ,at the same time1 all the electricians were zealous to search into the nature of this extraordinary phenomenon4 ,dr4 ,watson prosecuted experiments to ascertain how best to succeed with the ,leyden phial4 ,he observed that the force of the shock was not increased by the size or number of the globes employed in filling it2 nor by increasing the quantity of water in the vessel2 but that the power was greatest when the glass was thinnest1 and the water warmer than the ambient air4 ,he was proceeding with these discoveries1 when ,mr4 ,bevis informed him that he found the electric explosion as great from covering the sides of a pane of glass1 as it could have been from a half pint phial of water4 ,the ,doctor upon this coated large jars with leaf silver1 both inside and outside1 within an inch of the top1 and from the greatest explosion he produced from them1 drew the conclusion that the effect of the ,leyden bottle was owing1 not so much to the quantities of non-electric matter contained in the glass1 as to the number of points of non-electric contact within the glass1 and the density of matter of which these points consisted4 ,in ,france1 the ,abb ,nollet attempted to measure the distance to which the electric shock might be carried1 and the velocity with which it passes4 ,at one time he electrified #ahj of the guards in the king's presence2 and at another the whole community of the grand convent of the ,carthusians at ,paris1 forming a line of #ijj toises1 by means of iron wires between every two persons2 when the whole company1 upon the discharge of the phial1 gave a sudden spring at the same instant of time1 and all felt the shock equally4 ,but these attempts of the ,french philosophers to measure the electric circuit were insignificant1 in comparison with the extended and numerous experiments of ,dr4 ,watson1 accompanied by a number of ,english gentlemen of eminence4 ,those gentlemen1 in their first attempt1 conveyed the electric shock across the river ,thames2 making use of the water of the river as a part of the chain of communication4 ,this was accomplished by fastening a wire all along the ,westminster bridge1 at a considerable height above the water4 ,one end of this wire communicated with the coating of a charged phial1 the other being held by an observer1 who1 in his other hand1 held an iron rod which he dipped into the river4 ,on the opposite side of the river stood a gentleman1 who likewise dipped an iron rod into the river with one hand1 and in the other held a wire the extremity of which might be brought into contact with the wire of the phial4 ,upon making the discharge1 the shock was felt by the observers on both sides of the river1 but more sensibly by those who were stationed on the same side with the machine2 part of the electric fluid having gone from the wire down the moist stones of the bridge1 thereby making several shorter circuits to the phial2 but still all passing through the gentlemen who were stationed on the same side with the machine4--,this was1 in a manner demonstrated1 by some persons feeling a sensible shock in their arms and feet1 who only happened to touch the wire at the time of one of the discharges1 when they were standing upon the wet steps which led to the river4 ,in one of the discharges made upon this occasion1 spirits of wine were kindled by the fire which had gone through the river4 ,they afterwards undertook to determine whether the electric virtue could be conveyed along dry ground1 and to distinguish1 if possible1 the respective velocity of electricity and sound4 ,for this purpose1 they fixed upon a hill1 and made their first experiment on the #adth of ,august #agdg2 a time1 when1 as it happened1 but one shower of rain had fallen during five preceding weeks4 ,the wire communicating with the iron rod which made this discharge1 was supported all the way upon baked sticks2 as was also the wire which communicated with the coating of the phial1 and the observers were distant from each other two miles4 ,the result of the explosion demonstrated to the gentlemen present1 that the circuit performed by the electric matter was four miles1 viz4 two miles of wire1 and two of dry ground1 the space between the extremities of the wires4--,a distance which1 without trial1 as they justly observed1 was too great to be credited4 ,a gun was discharged at the instant of the explosion1 and the observers had stop watches in their hands1 to note the moment when they felt the shock2 but1 as far as they could distinguish1 the time in which the electric matter performed that vast circuit might have been instantaneous4 ,travellers through a new region of science1 like travellers through an unexplored country1 too often think themselves absolved from the strict obligations of truth1 and at liberty to amuse the public with romantic accounts of what they have heard and seen4 ,about the time these experiments were going forward in ,england1 the passion for the marvellous strongly discovered itself in relating some effects of electricity1 pretended to be found out in ,italy and ,germany4 ,it was asserted by ,signor ,privati of ,venice1 and after him by ,verati at ,bologna1 ,mr4 ,blanchi at ,turin1 and ,mr4 ,winckler at ,leipsic1 that if odoriferous substances were confined in glass vessels1 and the vessels excited1 the odours and other medical virtues would transpire through the glass1 infest the atmosphere of the conductor1 and communicate their virtue to all persons in contact with it2 also1 that those substances1 held in the hands of persons electrified1 would communicate their virtues to them1 so that the medicines might be made to operate without being taken into the stomach4 ,they even pretended to have wrought many cures by the help of electricity applied in this way4 ,it was affirmed that a man who1 having a pain in his side had applied hyssop to it by the advice of a physician1 approached a cylinder in which was concealed some balsam of ,peru1 and was electrified by it4 ,the consequence was that when he went home and fell asleep he sweated1 and the power of the balsam was so dispersed that even his clothes1 the bed and chamber1 all smelled of it4 ,when he had refreshed himself by this sleep1 he combed his head1 and found that the very comb was perfumed4 ,to see the wonderful effects of these medicated tubes1 as they were called1 ,mr4 ,nollet travelled into ,italy1 where he visited all the gentlemen who had published an account of these alledged facts4 ,but though he engaged them to repeat their experiments in his presence and upon himself1 and though he made it his business to get all the information he could concerning them1 he returned fully convinced1 that in no instance had odour been found to transpire through the pores of excited glass1 and that no drugs had ever communicated their virtues to people who had only held them in their hands while they were electrified4 ,he was convinced1 however1 that by continued electrification1 without drugs1 several persons found considerable relief in various disorders2 particularly1 that a paralytic person had been cured at ,geneva1 and that one who was deaf of an ear1 another who had a violent pain in his head1 and a woman with a disorder in her eyes1 had been cured at ,bologna3 so that from this time we may date the introduction of electricity into the medical art4 ,another wonderful experiment was the beatification of ,mr4 ,boze2 which other electricians1 for a long time1 endeavoured to repeat after him1 but to no purpose4 ,his description of this remarkable experiment was1 that if1 in electrifying1 large globes were employed1 and the electrified person stood upon large cakes of pitch1 a lambent flame would by degrees arise from the pitch1 and spread itself around his feet2 that from thence it would be propagated to his knees and body1 till at last it ascended to his head2 that then1 by continuing the electrification1 the person's head would be surrounded by a glory1 such as is in some measure represented by painters in ornamenting the heads of saints4 ,dr4 ,watson took the utmost pains to repeat this experiment4 ,he underwent the operation several times1 and was supported during the time of it by solid electrics three feet high4 ,being electrified very strongly1 he felt a kind of tingling on the skin of his head1 and many other parts of his body4 ,the sensation resembled what would arise from a vast number of insects crawling over him at the same time4 ,he constantly observed the sensation to be the greatest in those parts of his body which were nearest to any non-electric2 but no light appeared upon his head1 though the experiment was several times made in the dark1 and with some continuance4 ,at last the ,doctor wrote to ,mr4 ,boze himself1 and his answer showed that the whole had been a trick4 ,mr4 ,boze acknowledged that he had made use of a suit of armour1 which was decked with many pieces of steel1 some pointed like nails1 others like wedges1 and some pyramidal2 and that when the electrization was very vigorous1 the edges of the helmet would dart forth rays1 something like those which are painted on the heads of saints4 ,the identity of electricity and lightning was the next discovery that engaged the attention of philosophers2 and it is a discovery of the first practical importance4 ,we have already noticed the conjectures hazarded by the ancients1 on this identity1 and we may remember that ,dr4 ,wall1 in his experiments on electric light and the crackling with which electricity is emitted1 notices the similarity between it1 and the phenomenon of thunder and lightning4 ,but when the experiment of the ,leyden phial was known to philosophers1 this analogy became much more obvious4 ,the ,abb ,nollet1 after suggesting that thunder is in the hands of nature what electricity is in ours1 enumerates many points of resemblance between these two powers1 and then says1 that meditating on these points1 he concludes 8that one might1 by taking electricity for the model1 form to ones self1 in relation to thunder and lightning1 more perfect and more probable ideas than what have been offered hitherto40 ,but though these philosophers1 and many others1 were struck with this similarity between the electric fluid and lightning1 they did not think of any method by which their suspicions might be brought to the test of experiment4--,this was first proposed by ,dr4 ,franklin in #agej4 ,he had before discovered the effects of pointed bodies in drawing off the electric matter more powerfully than others4 ,this was suggested to him by one ,mr4 ,thomas ,hopkinson1 who electrified an iron ball of three or four inches diameter1 with a needle fastened to it1 expecting to draw a stronger spark from the point of it2 but was surprised to find little or none4 ,dr4 ,franklin1 improving on this hint1 supposed that pointed rods of iron1 fixed in the air when the atmosphere was loaded with lightning1 might draw from it the matter of the thunder-bolt1 without noise or danger1 into the body of the earth4 ,his account of this supposition is given by himself in the following words4 8,the electric fluid is attracted by points4 ,we do not know whether this property be in lightning2 but since they agree in all the particulars in which we can already compare them1 it is not improbable that they agree likewise in this2 let the experiment be made40 ,this suspicion of ,dr4 ,franklin was verified in #ageb4 ,the most active persons in making the experiments by which it was confirmed1 were two ,french gentlemen1 ,messrs4 ,dalibard and ,delor4 ,the former prepared his apparatus at ,marly la ,ville1 situated five or six leagues from ,paris2 the other at his own house1 on some of the highest ground in that capital4 ,mr4 ,dalibard's machine consisted of an iron rod forty feet long1 the lower extremity of which was brought into a centry-box1 where the rain could not come2 while on the outside it was fastened to three wooden posts1 by long silken strings1 defended from the rain4 ,this machine happened to be the first that was favoured with a visit of the etherial fire4 ,mr4 ,dalibard himself was not at home2 but1 in his absence1 he had entrusted the care of his apparatus to one ,coissier a joiner1 who had served fourteen years among the dragoons1 and on whose courage and understanding he could depend4 ,this artisan had all the necessary instructions given him2 and was desired to call some of his neighbours1 particularly the curate of the parish1 whenever there should be any appearance of a thunder storm4 ,at length the long expected event arrived4 ,on ,wednesday the #ajth of ,may #ageb1 between two and three in the afternoon1 ,coissier heard a pretty loud clap of thunder4 ,immediately he ran to the machine1 taking with him a phial furnished with a brass wire2 and presenting the wire to the end of the rod1 a small spark issued from it1 with a snap like that which attends a spark from an electrified conductor4 ,stronger sparks were afterwards drawn1 in the presence of the curate and a number of other people4 ,the curate's account of them was1 that they were of a blue colour1 an inch and a half in length1 and smelled strongly of sulphur4 ,in making them1 he received a stroke on his arm a little below the elbow2 but he could not tell whether it came from the brass wire inserted into the phial1 or from the bar4 ,he did not attend to it at the time2 but the pain continuing1 he uncovered his arm when he went home1 in the presence of ,coissier4 ,a mark was perceived round it1 such as might have been made by a blow with the wire on his naked skin4 ,although it appears from the foregoing statement1 that the directions of ,dr4 ,franklin began to be put in execution in ,france1 he himself completed the demonstration of his own problem1 before he heard of what was done elsewhere4 ,an account of these experiments will be found in the scientific part of this work4 ,since the time of ,franklin1 there has been no capital discovery in electricity3--at least1 no discovery of such a nature as to demand a detailed account in this portion of our work4 ,experiments and improvements have been made2 and numerous electricians have evinced a very commendable diligence in the cultivation of this department of knowledge4 ,but their exertions have been directed to the reason and philosophy of the phenomena already known1 to the classification of the facts1 and to the improvement of the apparatus4 ,thus ,mr4 ,canton has given a very curious set of experiments upon the conducting power of air1 to ascertain wherein consists the distinction between the bodies which are conductors1 and those which are not4 ,signor ,beccaria1 also1 with the same view1 experimented upon water and smoke4 ,but what more properly belongs to history1 is to mention the view1 which ,mr4 pinus1 of the ,imperial ,academy of ,st4 ,petersburgh1 in the year #agei1 took of the science of electricity4 ,this gentleman1 struck with the resemblance of the electrical properties of the tourmaline to the properties of a magnet1 which have always been considered as the subject of mathematical discussion1 fortunately remarked a wonderful similarity in the whole series of electrical and magnetical attractions and repulsions1 and set himself seriously to the classification of them4 ,having done this with great success1 and having maturely reflected on ,dr4 ,franklin's happy thought of plus and minus electricity1 and his consequent theory of the ,leyden phial1 he at last hit on a mode of considering the whole subject of magnetism and electricity1 which bids fair for leading to a full explanation of all the phenomena2 at least1 as far as to enable us to class them with precision1 and to predict what will be the result of any proposed treatment4 ,the work containing this hypothesis1 was published at ,petersburgh1 under the title of ,theoria ,electritatis et ,magnetismi1 and is pronounced to be 8one of the most ingenious and brilliant performances of the last century40 ,a summary view of this theory1 and the principles on which it is formed1 will be seen in the course of the ensuing work4 ,great improvements in the electrical apparatus have likewise been made since the time of ,franklin2 particularly in devising methods to increase the power of electricity1 and to render sensible the slightest accumulation or deficiency of the electric fluid4 ,we shall1 however1 content ourselves1 in the conclusion1 with only mentioning the electrophorus and condenser1 invented by ,mr4 ,alexander ,volta1 ,professor of ,experimental ,philosophy at ,como1 c4 ,this last instrument is honorable to its inventor1 not only on account of the extensively useful purposes to which it has been and may be applied2 but1 likewise1 because it was discovered1 not casually1 like most of the electrical apparatus1 but in consequence of scientific deduction and reasoning4 99 99 99 99 99 ,the origin of ,galvanism is so recent1 that we think it unnecessary to give any other history of it1 than that which will be found connected with the article in the body of our work4 ,,contents ,,of ,,the ,,epitome ,,of ,,electricity4 ,,division ,i4 ,chap4 ,page4 ,i4 ,explanation of terms2 with some general remarks4 #a ,,ii4 ,electric substances2 with some of the phenomena attending their excitation4 #c ,,iii4 ,of electrics and conductors4 #f ,,iv4 ,of the electrical machine4 #i ,v4 ,of communicated electricity4 #ae ,,vi4 ,of the electric spark4 #af ,,vii4 ,of the influence of pointed bodies on electricity1 and some phenomena attending their operation4 #ag ,,viii4 ,of electric attraction and repulsion4 #ba ,,ix4 ,of the ,leyden phial4 #bf ,x4 ,of the electrical battery1 and experiments performed with it4 #bh ,,xi4 ,of the electrophorus1 and some of its phenomena accounted for4 #cc ,,xii4 ,of electrometers4 #cf ,,xiii4 ,the identity of electricity with lightning4 #dj ,,xiv4 ,of the structure and use of the electrical kite4 #da ,,xv4 ,the structure and use of lightning rods4 #dh ,,xvi4 ,of animal electricity4 #ee ,,xvii4 ,the influence of electricity on vegetables4 #fa ,,xviii4 ,medical electricity4 #fc ,,xix4 ,directions concerning the use of the electrical apparatus1 with some practical rules for performing experiments with it1 to the best advantage4 #fh ,,division ,,ii4 ,i4 ,entertaining experiments made by electrical attraction and repulsion4 #gc ,,ii4 ,experiments with electric light4 #gi ,,iii4 ,experiments with charged electrics4 #hf ,,iv4 ,experiments relating to the influence of pointed bodies on electricity4 #ib ,v4 ,promiscuous experiments4 #id ,,division ,,iii4 ,i4 ,introductory observations to the theory of electricity4 #aje ,,ii4 ,theories of electricity1 exclusively of that of ,franklin4 #ajh ,,iii4 ,the ,franklinian theory of electricity4 #aaf ,,appendix4 ,no4 ,i4 ,a description of the cement used for electrical purposes4 #abe ,,ii4 ,a composition for coating cylinders or globes4 #abe ,,iii4 ,to make the best kind of amalgam for exciting electrics4 #abf ,,iv4 ,the preparation of electrical paint4 #abf ,v4 ,to make the artificial bolognian stone4 #abg ,,contents ,,of ,,the ,,epitome ,,of ,,galvanism4 ,chap4 ,page4 ,i4 ,a short account of the discovery of ,galvanism4 #abi ,,ii4 ,of the animals best fitted for ,galvanic experiments2 of the metals best calculated for making these experiments2 and of conductors4 #aca ,,iii4 ,a description of the ,galvanic trough and pile4 #acd ,,iv4 ,the method of performing ,galvanic experiments with frogs2 with some conclusions drawn from them4 #ach ,v4 ,various experiments with the ,galvanic pile4 #adj ,,vi4 ,experiments on the deflagration of metals by the ,galvanic pile4 #adc ,,vii4 ,further ,galvanic experiments on metals1 and on other substances4 #ade ,,viii4 ,experiments which may be performed without the assistance of the battery4 #adh ,,ix4 ,some common effects which are supposed to be occasioned by ,galvanism4 #aej ,x4 ,the effects of ,galvanism on vegetables4 #aeb ,,xi4 ,of medical ,galvanism4 #aed ,,xii4 ,the identity of ,galvanism with electricity considered4 #aeg ,,epitome ,,of ,,electricity4 ,,division ,i4 ,,chap4 ,i4 ,explanation of ,terms2 with some general ,remarks4 ,if a glass tube be rubbed in the dark with a dry hand or piece of buckskin1 upon applying the knuckle to it a luminous stream or spark will appear1 passing from the glass to the knuckle1 attended with a crackling noise3 this luminous spark or stream is called electricity4#h ,it is produced by the friction of several other substances1 and was first observed on amber4--,hence its name1 from the greek term for amber4 ,it is a fluid extremely subtle1 abounding in all nature1 and is one of her principal agents2 which1 though generally imperceptible1 sometimes becomes the object of our sight and other senses4 ,a glass tube1 having been rubbed and producing the appearances above described1 is said to be excited4 ,the hand or buckskin1 by which this is effected1 is called the rubber4 ,electrics are all substances which can be made to produce the same appearances2 the most perfect are glass1 amber1 sealing-wax1 sulphur1 gum lac1 rosin c4 ,these are also called non-conductors1 from their inability to conduct the electric fluid4 ,conductors or non-electrics are those bodies which cannot be excited1 but have the power of transmitting electricity2 such are metals1 water1 the bodies of animals1 an imperfect vacuum1 heat c4 ,but strictly speaking1 there are no perfect conductors or non-conductors4 ,a body is said to be in its natural state1 when it is in the same state1 with respect to electricity1 as the mass of the earth4 ,when a body has more of the electric fluid than its natural quantity1 it is said to be electrified positively1 when less1 negatively2 but neither of these cases can occur in a conductor1 unless the communication between it and the earth be cut off by the intervention of an electric or non-conductor4 ,when this happens1 the conductor is said to be insulated4 ,it may not be amiss here to mention1 that the terms electric or an electric per se1 and non-electric1 were at first made use of from an erroneous idea that only those called electrics1 contained the electric matter in their substance1 which was capable of being excited by friction1 and communicated by them to those called non-electrics1 and supposed to be destitute of it3 for glass and other electrics1 being rubbed1 discovered signs of having it1 by snapping on the approach of a finger or other conductor1 and by attracting and repelling light bodies2 while other substances could not be made to produce any such effect4 ,it has however since been proved by experiments1 that both electrics and non-electrics contain this matter in their substance2 but that non-electrics cannot be excited1 owing to the fluid diffusing itself through them as soon as collected4 ,these terms are therefore improper1 and as the only difference is that some bodies will conduct electricity and others will not1 the terms non-conductor and conductor are those which might generally be used with the most propriety in speaking on this subject2 though1 in conformity with custom1 we shall often use non-conductor and electric as synonymous4 ,,chap4 ,,ii4 ,electric substances2 with some of the phenomena attending their excitation4 ,those substances by which electrical phenomena may be produced1 form the subject which next demands our attention2 but these are so numerous that it would be vain to attempt to specify them all4 ,perhaps it may be doubted1 whether every material substance1 with the exception only of metals1 water1 and charcoal1 may not be considered as an electric4 ,some however exhibit particular phenomena more obviously than others2 and hence a number of catalogues have been formed1 for shewing the effects which arise when electrics are excited with different rubbers4 ,the specification which we esteem the most complete1 was formed by the ingenious ,mr4 ,cavallo1 and we shall give it in his own words4 8,in the following table 7says he7 may be seen what electricity will be excited in different bodies1 when rubbed with different substances4 ,smooth glass1 for instance1 will be found by this table to acquire a positive electricity1 when rubbed with any substance hitherto tried1 except the back of a cat3 7by which ,i mean the skin of a cat while on the animal alive37 rough glass1 7viz4 glass1 the polish of which has been destroyed by emery or otherwise7 will be found to acquire the positive electricity1 when rubbed with dry oiled silk1 sulphur c4 and the negative when rubbed with woolen cloth1 the hand c4 and so of the rest40 ,electrics4 ,qualities4 ,rubbers4 ,every substance with 8,the back of a cat ,positive which it has hitherto been tried4 ,every substance ,smooth ,glass ,positive hitherto tried1 except the back of a cat4 ,rough ,glass ,positive ,dry oiled silk1 sulphur1 metals4 ,woolen cloth1 quills1 ,negative wood1 paper1 sealing wax1 white wax1 the human hand4 ,tourmaline ,positive ,amber1 or air blown upon it4 ,negative ,diamond and the human hand4 ,white silk ,positive ,black silk1 metals and black cloth4 ,negative ,paper1 hand1 hare's weasel's skin4 ,black silk ,positive ,sealing wax4 ,hare's1 weasel's and ,negative ferret's skin1 load-stone1 brass1 iron1 silver1 hand4 ,metals1 silk1 ,weasel's skin ,positive load-stone1 leather1 hand1 paper1 baked wood4 ,negative ,other fine furs4 ,sealing wax ,positive ,metals4 ,hare's1 ferret's and ,negative weasel's skin1 hand1 leather1 woolen cloth1 paper4 ,baked wood ,positive ,silk4 ,negative ,flannel40 ,from the above table it appears1 that the powers of electric substances vary prodigiously from one another2 and that1 according to the different rubbers made use of1 we may sometimes produce one phenomenon and sometimes another4 ,hence we have a foundation for classing electric substances according to the various powers they occasionally exhibit2 which may be done in the following manner4 ,first4 ,those which exhibit a strong and permanent attractive and repulsive power1 of which the most remarkable is silk4 ,second4 ,those which exhibit the electric light1 attraction1 repulsion1 and all the other phenomena of electricity in a very vigorous1 though not durable manner2 of these glass is eminently preferable to all others4 ,third4 ,those which exhibit electric appearances for any length of time1 and which communicate to conducting bodies1 the greatest electric power4--,of these1 the substances called negative electrics1 such as sealing-wax1 resinous substances1 and resinous compounds1 are the best4 ,fourth4 ,those which readily exhibit electrical phenomena by heating and cooling4--,of these1 the tourmaline#i is the principal4 ,the best method of disturbing the electric fluid1 that is of making it pass from one body to another1 is friction4 ,this may be done either by rubbing one electric with another1 or with a conductor2 but the electricity is generally stronger in the latter case4 ,other methods for causing electrics to shew electric appearances1 are1 melting1 or pouring a melted electric on another substance1 heating and cooling1 evaporating or effervescing4 ,,chap4 ,,iii4 ,of ,electrics and ,conductors4 ,all bodies in nature are1 with reference to this subject1 divided into two classes1 electrics and conductors4 ,it has been fully demonstrated by experiment1 that no substance which is a conductor can be excited so as to exhibit electrical phenomena3 and in the same manner it has been found1 that no substance which can be excited1 is a conductor4 ,but as we have already hinted1 there is1 strictly speaking1 no substance which is a perfect conductor or non-conductor2 because1 on the one hand1 the electric fluid meets with some resistance in its passage through the best conductors2 and on the other1 it is in part transmitted through1 or passes over the surface of1 most if not all electrics4 ,the two following lists contain as complete an enumeration of electrics and conductors as the present state of knowledge1 in regard to electricity1 permits us to make4 ,the substances are disposed in the order of their perfection2 that is1 the best conductors and the best electrics are placed at the head of their respective lists1 and those of an inferior kind follow1 somewhat in the manner of a scale graduated downward4 ,perfect exactness however is not to be here expected1 because the subject forbids it1 and some of the specified articles are of classes of substances among which there may be a sensible difference4 ,conductors or non-electrics4 ,gold1 ,silver1 ,copper1 ,platina1 ,brass1 ,iron1 ,tin1 ,mercury1 ,lead1 ,semi-metals4 ,metallic ores4--,of which those are the best which contain the greatest number of metallic parts and are nearest to a reguline state4 ,charcoal1 either of animal or vegetable substances-- ,animal fluids1 ,acids1 ,saline substances1 ,hot water1 ,cold water1 ,salt water1 ,all other liquids except oils1 ,red hot glass1 ,melted rosin1 ,flame and the effluvia of flaming bodies1#aj ,ice and snow--but not below the temperature of #ac ,fahrenheit4 ,earthy and stony substances1 of which the hardest are the worst4 ,glass filled with boiling water1 ,vapour or steam of boiling water1 ,smoke4 ,all compounds which contain the above substances in different proportions1 are conductors in different degrees4 ,non-conductors or electrics4 ,glass and all vitrifications2 even those of metals4 ,all gems1 of which the most transparent are generally the best4 ,all resinous substances and resinous compounds1 ,amber1 ,sulphur1 ,baked wood--if not suffered to imbibe moisture4 ,all bituminous substances1 ,wax1 ,silk1 ,cotton4 ,all dry animal excrescences2 as feathers1 hair1 wool1 horn1 c4 ,paper1 ,white sugar and sugar candy1 ,atmospheric air and other gasses1 ,oils1 ,dry and complete metallic oxyds1 ,the ashes of animal and vegetable substances1 ,all hard stones2 of which the hardest are the best1 ,powders not metallic4 ,ice at and below the temperature of #ac of ,fahrenheit's thermometer4 ,according to ,mr4 ,walsh's and ,mr4 ,morgan's experiments1 the ,torricellian vacuum ought to be placed at the head of this list2 but the singular nature of a vacuum1 though a non-conductor1 will hardly entitle it to the name of an electric4 ,,chap4 ,,iv4 ,of the electrical machine4 ,having now explained the terms made use of in the study of electricity1 and noted some of the phenomena of different electric substances1 and the difference between electrics and conductors2 we shall proceed to describe the electrical machine made use of for shewing experiments1 and for exhibiting other electric phenomena to the best advantage4 ,the principal parts of the machine are1 the electric1 the rubber1 the moving engine1 and the prime conductor4 ,we shall take notice of each of these parts separately and then describe the whole machine together4 ,formerly different kinds of electrics were used2 at present smooth glass is preferred before all others1 as most convenient1 and because it will1 by itself1 answer the purposes of several others4 ,for when the machine has an insulated rubber1 which is easily prepared1 the operator may produce positive or negative electricity#aa at pleasure1 without changing the electric4 ,with respect to the forms of the glass1 those commonly used are globes1 cylinders and plates4 ,the most convenient size for a globe is from ten to twelve inches in diameter4 ,it should have two necks1 centrally opposite1 which must be cemented#ab to strong caps1 in order to adapt them to a proper frame4 ,cylinders are also made with two necks4 ,their common size is from six to seven inches in diameter1 and from ten to twelve inches in length2 the glass generally used is the best flint4 ,it has long been questioned whether a coating#ac of some electric substance1 has any effect in increasing the power of an electric2 but now it seems pretty well determined1 that if it does not increase the power of a good one1 it at least considerably improves a bad one4 ,the next thing to be considered is the rubber which is to excite the electric4 ,this1 as it is now made1 consists of a cushion of buckskin1 stuffed with hair or flannel1 and fastened to a piece of wood well rounded at the edges2 to this is glued a flap of ,persian black silk1 which goes over nearly one half of the cylinder or globe4 ,the rubber should be supported by a small iron or brass spring1 placed inside of it1 as is represented edgewise by ,r1 figure #b1 in the frontispiece4 ,this acts in a much more uniform and parallel manner than if it were placed under the cylinder4 ,it suits any inequalities that may be on the surface of the glass1 and by means of a screw may be made to press against the cylinder as occasion requires4 ,it should likewise be insulated in the most perfect manner by glass1 or by baked wood well varnished4 ,but when experiments are to be made which do not require or admit of insulation1 a communication must be made between the rubber and the earth1 by a chain or conductor4 ,to increase the effect of the rubber several substances have been used with success1 particularly whiting and pulverised chalk4 ,but the best of all is an amalgam of zinc and mercury4#ad ,this amalgam is to be used by first applying a moderate quantity to the cushion2 and afterwards by spreading it on a separate piece of leather1 and applying it occasionally to the under part of the cylinder while turning4 ,in this method of using it1 only a small quantity of amalgam is consumed1 while the glass is very strongly excited2 and by degrees the whole rubber contiguous to the cylinder is covered with amalgam1 in the form of a concave cake4 ,it is with such a rubber that the cylinder is most powerfully excited4 ,an ingenious friend has favoured us with the following explanation of the manner in which electrics are excited1 which to us is more satisfactory than any other we have seen4 8,in order that electricity may be accumulated in greater quantity in one body than in the surrounding ones1 it must be set in motion4 ,this may be effected by the rubbing of electrics2 the juxta-position of non-electrics of different conducting powers2 and by the chemical action of many1 if not all bodies on each other4 ,the rubber will act on the first principle1 and the more perfect the contact between it and the electric the greater will be the effect4 ,the chalk1 whiting1 amalgam c4 while they will1 if properly prepared1 make the contact more perfect1 will also be of service on the second principle2 and the amalgam will besides be of use on the third4 ,mercury and zinc may be exposed separately to the air without any alteration2 but when combined they readily unite with the oxygen of the atmosphere2 especially when the surface of contact is frequently renewed1 and the temperature increased by friction4 8,the glass1 acquiring a different state of electricity from the rubber1 will1 as each portion passes from under it1 carry away and impart to the prime conductor the excess which it has obtained2 and this the more certainly if the dissipation of the electricity be prevented1 or the accumulation increased1 by a piece of silk connected with the rubber4--,the chain making the communication between the rubber and the adjoining non-electrics will enable this process to go on2 and perhaps may also assist on the second principle40 ,with respect to the engine which is to give motion to the electric1 it has been customary1 simply to turn the globe or cylinder with a winch2 but this will not produce the greatest power of which the glass is capable4 ,to effect this it should be made to turn six or seven times in a second1 which is more than can conveniently be done with the winch only2 and therefore multiplying wheels are used with advantage4 ,the prime or first conductor is an insulated non-electric substance1 furnished with a number of points on the end towards the electric1 in order to collect the electricity from it4 ,it is usually made cylindrical1 but whatever be its form it should always be perfectly free from points or sharp edges1 except the points toward the electric already mentioned2 and if holes are made in it1 which on many accounts are very convenient1 they should be well rounded and perfectly smooth4--,the larger this conductor is1 if not disproportionate to the cylinder or globe1 the stronger and more dense will be the electric spark1 which will proceed from it when touched by a blunt conductor4 ,there must however always be a certain proportion between the cylinder or globe and the prime conductor1 for if the former be small and the latter large1 the electricity will not be collected fast enough1 to preserve an accumulation of it in the prime conductor1 because a portion is always taken off by the air1 in proportion to the surface presented to it by the conductor4 ,we shall now give a short connected explanation of the whole machine1 a draft of which is exhibited in the frontispiece4 ,,ab and ,,cd are two pillars of baked wood well varnished1 perpendicularly raised from the top of the table ,,efgh--these serve to support the cylinder ,i1 by the axles of the caps ,,kk2 from one of these proceeds the long axle ,l1 which passes through a hole in the pillar ,,cd1 having the pulley ,m1 fixed on its square end4 ,n is a multiplying wheel1 around which the band or strap ,o passes1 and likewise around the pulley ,m4--,the wheel ,n should be made moveable with respect to the pulley ,m1 to accommodate the stretching of the band1 or else the pulley should have a number of grooves of different radii in its circumference4 ,the rubber ,r1 is fastened to a pillar of glass1 or baked wood ,p4 ,the pressure of the rubber may be augmented at pleasure1 by means of a sliding board and tightening screw4 ,the prime conductor is represented by ,q4 ,it is insulated by the glass pillars ,,ss1 which support it4 ,t represents the points which collect the electricity from the cylinder4 ,cylinders and globes made for electrical machines are not always to be procured4 ,their place however1 may be very well supplied by the large show bottles of the apothecaries4 ,when these are used1 one of the caps1 instead of being concave 7to receive the neck of the cylinder7 must be made convex--so as to fit the hollow in the bottom of the bottle4--,it is to be fastened with the cement used in the other machine4 ,the most powerful electrical machine ever constructed1 was at ,teyler's museum at ,haarlem4 ,it had1 instead of the cylinder or globe as in the common machines1 two circular plates of glass1 which were made to turn upon the same horizontal axis4 ,these plates were excited by eight rubbers1 which acted on their surfaces4 ,in this machine the prime conductor had branches which collected the electricity from between the plates4 ,it is not necessary however in this form of the machine to have two plates1 the second being added only to increase the power4 ,the plate must be firmly fastened by its centre to an axis--so as to turn vertically between two uprights of baked wood1 as in the construction of the cylindric machines2 but in this case the uprights must be so close together1 as barely to leave room for a rubber on each side of the plate4 ,the rubbers may be made of the same form with that in the cylindric machine--except that they must have a projection at the back1 to fit a niche cut in the uprights which support the plate4 ,the power of the machine will be increased by having four rubbers2 two above and two below the axis of the plate4 ,the prime conductor is placed opposite one of the ends of the axis1 and is divided at the end towards the electric into two branches or arms1 which extend horizontally to the circumference of the plate1 each of which is furnished with points to collect the electricity4 ,as plates are not always to be procured1 a good substitute may be found in a thick pane of glass or a piece of an old looking-glass4 ,mark with a diamond or file a circle on the glass1 of the size you intend for your plate4 ,then putting the plate into warm water1 after some time cut the glass with a diamond in tangents4 ,the more numerous the cuts1 the nearer the plate will be to a circle4 ,a hole may be made in the centre for the axis1 by scratching with a diamond1 and grinding with a rod of iron 7held between the hands7 and emery4 ,,chap4 ,v4 ,of communicated electricity4 ,having described the electrical machine1 we are now to consider some of the phenomena attending its operation4 ,when the prime conductor receives electricity from the cylinder1 it is said to be electrified by communication1 and it then acts in every respect like the cylinder itself1 except that the latter1 when touched by a conductor communicating with the earth1 gives a considerable number of sparks before it is discharged2 whereas the conductor discharges itself by a single spark4 ,the cause of this difference is that the cylinder1 being an electric1 cannot convey the electricity of all its surface to that part1 to which the conducting substance is applied2 but the fluid accumulated in the whole conductor1 passing easily through its substance1 is transmitted at once to the point from which the discharge is made4 ,hence it appears that the electricity discharged from an electrified conductor is more powerful than that discharged from an electric--the conductor acquiring a large quantity of electricity from an electric1 by receiving it gradually1 spark after spark1 and afterwards1 when touched1 discharging it all at once4 ,the velocity of electricity is almost beyond conception4 ,it is1 notwithstanding1 in a small degree relative to the quantity put in motion1 and to the goodness of the conductor by which it is transmitted4 ,a large quantity of electricity passes through a good conductor with such rapidity1 that there is no perceptible difference in the time which it takes to go one foot1 or one thousand feet4 ,a small quantity however has been found to take a time barely perceptible1 in passing through a long and imperfect conductor4 ,experiments relative to this point will be related hereafter4 ,,chap4 ,,vi4 ,of the electric spark4 ,if a piece of metal be presented to an over-charged prime conductor1 the fluid passes with violence from the one to the other2 an electric spark1 having the appearance of fire1 is seen flashing between them1 and a snapping noise1 like the cracking of a whip1 is heard4 ,if this piece of metal be insulated1 the prime conductor will be only partially discharged1 that is1 the redundant electricity will be divided between it and the piece of metal1 nearly in proportion to their surfaces4 ,this electric spark has not only the appearance of fire1 but1 when large1 will actually set fire to a variety of easily inflammable substances2 such as cotton sprinkled with rosin1 spirits of wine c4 ,this power of exciting flame is not commonly believed to arise from any culinary heat in the electric spark1 because if the spark be small it will not excite flame in substances the most inflammable4 ,it acts probably by friction on the same principle as the rubbing of sticks against each other produces fire4 ,the electric spark1 taken upon any part of a living animal1 causes an unpleasant sensation1 which is more or less pungent and disagreeable1 as the spark is stronger or weaker1 and the part more or less delicate4 ,there is a slight difference between the appearance of a spark taken from a body positively electrified1 and that from one negatively electrified4 ,the former1 if not very long1 appears straight and sharp2 the latter is generally ramified1 or appears in a zig-zag line4 ,the noise which attends the spark1 is caused by the sudden agitation into which the air is thrown1 by its passage through it4 ,,chap4 ,,vii4 ,of the influence of pointed bodies on electricity1 and some phenomena attending their operation4 ,if an uninsulated conductor1 which is broad1 round and polished at the end1 be presented to the prime conductor1 a short and dense spark1 accompanied with some noise1 will be perceived2 if the conductor be less broad1 the spark will be longer1 less dense1 and attended with less noise2 if the breadth be still more diminished1 so that the conductor may come under the denomination of a point1 the electric matter will pass to it1 from the prime conductor1 and through a greater space1 with a hissing noise1 and in a continual stream2 a still greater sharpness will enable the electricity to pass over a yet more extended space1 but unaccompanied by noise1 and only a small light will be seen upon the point4 ,the same result will arise if points of different acuteness be affixed to the prime conductor1 instead of the uninsulated one3 but if both be pointed1 the electricity will be more readily discharged4 ,in all the above cases1 the appearance of the electric matter at the point1 will indicate the kind of electricity from which it proceeds4 ,a large divergent cone indicates positive electricity2 a small globular light1 that which is negative4 ,hence it is always easy to ascertain whether an insulated conductor be electrified positively or negatively1 by presenting a point to it1 as the light at the point is always definitive of the contrary electricity in the conductor4 ,if a pointed conductor be electrified1 either positively or negatively1 and the face be brought near the point during the electrization1 a wind will be felt blowing from the point1 accompanied with a peculiar sensation1 commonly called the spider's web4 ,it is remarkable that the current of air is always in the same direction1 whether the point throws off or receives electricity4 ,the re-action of the force1 by which the air is put in motion1 is exerted upon the pointed body4 ,this is shewn by a very pleasing experiment called the electric fly4 ,this fly is composed of four small wires1 fastened into a metallic cap1 similar to those used in sea-compasses1 so that the wires may easily move upon a point1 in a horizontal direction4 ,they should be exactly balanced1 and have their ends1 which must be very sharp1 all bent in the same direction4 ,now if this fly be placed on an insulated point and electrified1 its sharp ends will become luminous in the dark1 and it will revolve in a direction contrary to that in which the ends are bent2 or if it be placed on an uninsulated point and brought near the electrified prime conductor1 the same effect will follow4 ,it is to be observed1 that the fly will move round in the same direction1 whether electrified positively or negatively4 ,the cause of this seeming contradiction depends upon the repulsive power existing between bodies possessed of the same electricity2 for the air opposite to the points acquires a strong electricity1 analogous to that of the points1 it is therefore repelled1 and replaced by other air1 which is also electrified and repelled4 ,hence a continual stream is produced1 blowing from the points1 and that equally1 whether the electrization be positive or negative2 and as action and re-action are equal and in contrary directions1 the points1 repelling the air1 must themselves be repelled1 and in the opposite direction2 which causes the fly to be always turned one way1 that is1 in a direction contrary to that in which the air is moved4 ,in vacuo no motion is produced1 because there is no air on which the electric matter can act when it issues from the points4 ,in like manner1 if air be confined in a receiver1 the motion of the fly soon ceases1 because the fluid cannot pass through the air and the glass4 ,but on applying the end of a finger to the outside of the receiver1 opposite one of the points of the fly1 the motion will begin again1 and by moving the finger occasionally round the glass1 it may be continued till most of the glass is charged4 ,the cause of this motion is1 that when the finger is applied to the outside of the receiver1 the glass1 loosing part of its natural quantity of electricity from that side1 7i4 e4 when the fly is electrified positively1 and vice versa if negatively7 takes up the fluid from the air on its inner surface4 ,hence the air becomes capable of being again electrified by the point and this renews the motion4 ,we have already stated that if a pointed wire be presented to a conductor positively charged1 it will be illuminated with a star or globe2 and if the conductor be negatively charged1 the illumination will have the form of a pencil or divergent cone4 ,f4 ,beccaria explains this in the following manner4 ,i suppose1 says he1 that the star is occasioned by the difficulty with which the electric fluid is extricated from the air1 which is an electric2 suppose for instance that a pointed wire is presented to a body positively electrified2 the electric fluid is first communicated from that body1 to the air between it and the pointed wire1 and then the wire must extricate it from the air4 ,the pencil is occasioned by the force with which the fluid1 issuing from the point1 passes through the contiguous air to that which is more remote1 i4 e4 by dividing the contiguous air1 and not by affixing itself to it4 ,beccaria likewise remarks1 that if two equally sharp pointed bodies are brought near the prime conductor1 they will appear luminous at only half the distance that one of them would4 ,they will also discharge it in half the time4 ,it will not be improper to remark here1 that when a point not electrified is opposed to one electrified positively1 both points will have small globular lights upon them2 but if a positive one be opposed to one negatively electrified1 they both preserve their own characteristic properties4 ,from the above the following conclusions may be drawn4 ,first1 ,that pointed bodies attract the electric matter more or less easily1 and at a greater or less distance1 according to their acuteness4 ,second1 ,that pointed bodies have the power of attracting electricity as well as of repelling it1 in a greater degree than conductors of any other form4 ,we shall treat farther of pointed conductors under the article ,thunder-house4 ,,chap4 ,,viii4 ,of electric attraction and repulsion4 ,no satisfactory theory of electric attraction and repulsion has1 so far as our knowledge extends1 ever yet been given4 ,the phenomena have been differently accounted for1 as the writers have embraced different opinions in regard to positive and negative electricity4 ,one mode of explanation has been adopted by those who believe1 with ,franklin1 that positive electricity is only an accumulation of the electric fluid in a body beyond its natural state2 and that negative electricity is nothing more than a deficiency of this fluid in a body4 ,another mode of explanation is given by those who maintain1 in opposition to ,franklin1 that positive and negative electricity are either two distinct fluids1 or else vibrations of the same fluid--the positive electricity always rushing out of a body1 and the negative always rushing in4 ,those who maintain this hypothesis endeavour to support it by the easy solution which they affirm it gives to the phenomena of electric attraction and repulsion4 ,but after a careful examination of this theory1 we think that1 so far from being satisfactory1 it is scarcely intelligible4 ,we therefore do not choose to introduce it into our epitome1 as affording any solution of the difficulties that occur on this part of our subject4 ,we are besides of opinion that the evidence in favour of a single fluid is conclusive1 as we shall show when we come to discuss the theory of electricity4 ,yet we confess that we cannot1 on this theory1 offer a rationale of electric attraction and repulsion1 that satisfies ourselves4 ,it is therefore the demand of candour1 and in the spirit of the ,newtonian philosophy1 to avow explicitly that this part of our subject is yet involved in much obscurity4 ,in the mean time we are acquainted with certain facts1 and with the clear explanation which they give of certain phenomena4 #a4 ,that bodies positively electrified1 repel each other4 #b4 ,that bodies negatively electrified1 also1 repel each other4 #c4 ,that bodies positively electrified1 attract those which are negatively electrified4 #d4 ,that bodies either positively or negatively electrified1 induce a contrary electricity in bodies in their natural state1 brought within the sphere of their action4 ,this statement is easily verified by experiment1 in the following manner4--,by flaxen or hempen threads1 suspend1 from the prime conductor1 two balls made of cork or elder-pith1 so that they touch each other4 ,on charging the conductor1 these balls1 being both electrified positively1 will immediately repel each other1 and be separated to a considerable distance4--,remove one of the balls1 take it in your fingers1 and bring it near to the one which remains positively electrified1 and the two will immediately rush together2 because there are now two substances of which one is electrified positively1 and the other negatively4--,again4 ,suspend two balls1 of the kind just mentioned1 from an insulated cushion of an electric machine1 and let them touch each other4 ,put the machine in motion and the balls1 which are now both electrified negatively1 will repel each other and separate1 as in the case first described4 ,in attempting to explain the first of these phenomena ,dr4 ,franklin once supposed that there was an electric atmosphere round each of the balls positively electrified1 the particles of which atmosphere1 by mutually repelling each other1 separated the balls4 ,he also supposed that as bodies negatively electrified1 or not having their proportional quantity of the electric fluid1 are always strongly disposed to receive it1 this would account for the fact that when one of these bodies was brought near to one that had more than its proportional quantity1 the two would naturally rush together2 the one to impart1 and the other to receive the fluid4 ,but at this time he was not acquainted with the fact1 that two bodies negatively electrified would repel each other4 ,when this was discovered he candidly acknowledged the utter deficiency of his theory1 in regard to electric attraction and repulsion4 ,some of his friends and followers1 however1 have endeavoured still to maintain it4 ,but we think that though their zeal has been greater1 their success has not exceeded that of the ,doctor himself3 and we have already stated that other theories are equally1 if not more defective1 than that of ,franklin4 ,let us then leave the explanation of electric attraction and repulsion to be made when future and fortunate discoveries shall have furnished the means of making it1 and let us proceed with the application of known facts and principles4 ,a pleasing exhibition of the phenomena of electric attraction and repulsion1 may be made in the following manner4 ,take a glass tube1 and after having rubbed it1 let a small light feather fall from your fingers1 at the distance of eight or nine inches from it4--,the feather will be immediately attracted by the tube and stick very close to its surface for some seconds1 after which it will be repelled1 and if the tube be kept under it1 the feather will continue floating in the air1 at a considerable distance from the tube1 without coming near it again1 except it touch some conducting substance2 and if you manage the tube dexterously1 you may drive the feather through the air of the room at pleasure4 ,the cause of this phenomenon is obvious4 ,the feather1 at first1 not being electrified1 rushes to the excited tube4 ,there it becomes electrified and is then repelled1 and cannot approach the tube again1 unless it first touch some conducting substance2 because it cannot part with its electricity while floating in the air1 and therefore cannot acquire a contrary electricity2 consequently it must remain in a state incapable of being again attracted by the excited tube4 ,there is a remarkable circumstance attending this experiment1 which is1 that if the feather be kept at a distance from the tube by the force of electric repulsion it always presents the same part towards the tube4 ,the reason of this phenomenon is1 that the equilibrium of the fluid in the different parts of the feather being once disturbed cannot easily be restored2 the feather being an electric1 or at least a very bad conductor4 ,when the feather has acquired a quantity of electricity from the tube it is plain that1 by the action of the excited tube1 that superinduced electricity will1 for the most part be forced to that side of the feather which1 at first1 happened to be farthest from the tube2 hence that part will always afterwards be repelled the farthest4 ,this experiment may be agreeably varied in the following manner4--,a person may hold an excited tube of glass1 within a foot and a half of a stick of sealing-wax1 or any other electric negatively electrified1 held by another person2 a feather let fall between these differently excited electrics will leap from one to the other alternately1 and the two persons will seem to drive a shuttlecock by the force of electricity4 ,another experiment calculated to shew the phenomena of electric attraction and repulsion is the electric spider4 ,cut a piece of cork in the shape of a spider1 and run a few short threads through it1 to represent the legs2 this done1 suspend it by a silk thread from the ceiling of the room1 or any other support1 so that the spider may hang mid-way between the knob of a jar and the knob of a wire fastened to the table1 or to the outside coating of the jar when not charged2 let the place where the jar stands be marked2 then charge and replace it4 ,the spider will now begin to move from knob to knob1 and continue this motion for a considerable time4 ,in this case1 the knob of the jar is charged positively1 and the spider1 being in its natural state1 is attracted by it2 the knob then communicates to it some of its electricity1 and the spider becoming possessed of the same electricity with the knob1 is repelled by it1 and immediately runs to the other knob1 which communicates with the negative coating1 or with the table1 where it discharges its electricity and is again attracted by the knob of the jar4 ,this attraction and repulsion continue till the jar is discharged1 when the spider finishes its motion and seemingly expires4 ,,chap4 ,,ix4 ,of the ,leyden phial4 ,this consists of a glass phial1 jar1 or bottle1 coated on the outside and inside with tin-foil1 rendered adhesive by paste or gum water4 ,about two inches of the glass at the top are left without any metallic covering1 to prevent a communication between the outside and inside coatings1 while the electricity is collecting4--,the mouth of the phial or jar is furnished with a cork which receives a wire1 ending in several ramifications which touch the inside coating4 ,the upper end of this wire1 which should extend a convenient distance above the mouth of the jar1 is furnished with a metallic ball4 ,when the phial or jar is to be charged1 it may be held in the hand or placed on an uninsulated table1 with the knob of the wire touching the prime conductor4 ,the inner surface of the glass now acquires the same electricity with the prime conductor1 and the external one acquires a contrary electricity by means of its uninsulated coating4 ,when a phial similar to the one above described is highly charged1 a spontaneous discharge will usually take place over the uncoated surface1 and seldom through the glass4 ,but if the uncoated surface be left larger than from two to three inches1 the phial is more apt to crack and become useless1 by the charge passing through the glass4 ,there is not however an absolute certainty that a jar which has once discharged itself over its surface will not1 at another time1 break by a discharge through the glass4 ,it was long disputed whether the discharge of the ,leyden phial resided in the coating or in the electric4 ,the following experiment clearly decides1 that its residence is in the electric4 ,upon an uninsulated plate of metal1 lay a plate of glass considerably larger1 so that there may be a rim of three or four inches projecting beyond the metal4 ,upon the glass lay another piece of metal1 of the same size with the first1 and so as precisely to cover it4 ,let this instrument be charged1 by connecting the upper metallic plate with the prime conductor4 ,then separate the metallic plates from the glass2 and upon examination the glass will be found to possess the contrary electricities on its opposite sides2 that side which during the electrization communicated with the prime conductor will have a like electricity with it1 and the other the contrary4 ,discharge the electricity of the metallic plates1 and replace the whole apparatus in its former situation4--,take a discharging rod1 formed by a piece of bent wire with a metallic ball at each end2 touch the under plate and bring the other end of the wire near the upper plate4 ,the consequence will be1 that a strong and loud spark will pass between the upper plate and the discharging rod2 the electricity of the glass will be discharged1 and there will afterwards remain no signs of electricity1 either in the glass1 or the metallic plates4--,hence it appears that the electricity resides in the glass1 and that the coatings1 whether in a plane or spherical form1 are of no other use than to convey the electric fluid to the glass2 to keep it equably distributed over the surface2 and to form a communication between the different parts of the electrified glass1 so that the discharge from them may be simultaneous4 ,when the discharge of a coated electric is made through the body of a living animal1 it occasions a sudden motion1 by contracting the muscles through which it passes1 and gives a disagreeable sensation commonly called the electric shock4 ,,chap4 ,x4 ,the electrical battery--and experiments performed with it4 ,when a greater degree of electric force is required than a single jar is capable of giving1 the electrical battery is made use of as part of the apparatus1 which takes its name from the formidable effects it produces4 ,this battery consists of a number of coated jars1 placed in such a manner that they may all be charged at the same time1 and discharged in an instant2 so that the whole force of electricity accumulated in them1 may at once be exerted on the substance exposed to the shock4 ,in discharging electrical jars1 the electricity goes in the greatest quantity through the best conductors1 and by the shortest passage4 ,thus if a chain and a wire be made to communicate at the same time with the outer coating of a jar1 and be both presented to the knob of that jar1 the greater part of the charge will pass by the wire1 and very little by the chain1 because the latter is a worse conductor than the former1 on account of its discontinuation at every link4 ,when the discharge is made by the chain only1 sparks are seen at every link1 which is a proof they are not in contact4 ,the force of an electric shock is not affected by the inflections of a conductor through which it passes1 though it is sensibly weakened by its length4 ,hence1 when the circuit or communication between the two sides of a ,leyden phial is formed by one person applying his hands to the different sides1 the shock is stronger than when it is formed by many persons joining hands4 ,yet a considerable shock was given by the ,abb ,nollet1 in the presence of the king of ,france1 to one hundred and eighty men2 who formed an electrical circuit4--,they were all shocked in the same instant4 ,doctor ,watson and many other gentlemen of eminence in science1 were at the pains of making experiments of the same kind4 ,they found1 by means of a wire insulated on baked wood1 that the electric shock was transmitted instantaneously through the length of #ab1bgf feet4 ,electricity transmitted in large quantities through living vegetables1 destroys their vegetable life4 ,when transmitted1 in the same form1 through animals1 it generally puts an end to animal life2 though it is said that there are individuals who are not affected by it4 ,possibly the reason why some persons are not killed by very large electric shocks is1 that their muscular system1 or bodily organization1 has something peculiar which protects them4 ,if an electrical circuit be made by means of imperfect conductors1 as a slender piece of wood1 a wet pack-thread1 the discharge will be made silently4 ,if a small interruption of an electrical circuit be made in water1 on making the discharge1 a spark will be seen in the water1 which never fails to agitate it and sometimes breaks the vessel in which it is contained4 ,a strong shock from a battery1 sent through a slender piece of metal1 instantly makes it red hot4 ,usually it is melted in whole or in part4 ,if the fusion be perfect it is reduced into globules of different magnitudes4 ,in this experiment it is a little remarkable that the parts of the metal at which the fluid enters and issues1 are most likely to be melted4 ,if the metal be enclosed between pieces of glass1 the shock will force the melted metal into the substance of the glass1 so that it cannot afterwards be removed1 without scraping off part of the glass with it4 ,in this experiment the glasses which enclose metal are commonly broken to pieces4--,it is seldom that they resist the force of a strong shock4 ,if the glasses enclosing metal be pressed by a heavy weight1 a small shock is often sufficient not only to raise the weight1 but to break glasses of considerable thickness4 ,when the pieces of glass are not broken1 they are marked by the explosion with the most lively prismatic colours1 which lie sometimes irregularly1 and sometimes in their prismatic order4 ,gun-powder may be fired by a charge from three square feet of coated glass4 ,the powder is to be put into a quill1 and then a wire is to be thrust into each end so as nearly to meet1 and afterwards these wires are to be made a part of an electrical circuit4--,a less charge of electricity will be sufficient if iron filings be mixed with the gun-powder4 ,when a shock somewhat less than is sufficient to melt a piece of metal is sent through a chain1 a black dust1 in the form of smoke1 is seen to proceed from the chain4 ,this dust is probably some of the metal itself1 partly calcined1 and by the violence of the explosion forced from it4 ,if the chain be laid upon a piece of paper1 glass1 or other electric1 this1 after the explosion1 will be found stained with some indelible marks1 and often shew evident signs of having been burnt4 ,what is more remarkable in considering the effects of electricity on metals is1 that it often1 in a considerable degree1 revivifies their calces or oxyds4 ,in making experiments of this kind1 the metallic calx or oxyd is to be made a part of an electrical circuit1 through which a strong shock is to be sent3 when the calx or oxyd will be found in a measure restored to its metallic state3 the electric shock having1 as it appears1 taken away from the oxyd a portion of its oxygen4 ,the electric shock when passed through the magnetic needle1 sometimes destroys its magnetic virtue1 and sometimes reverses its poles4 ,it is affirmed that two ships sailing together on the same voyage1 were led1 from the effect of lightning on their needles1 to steer exactly opposite courses1 after the storm in which they were exposed to the lightning had subsided4 ,when the charge of ten1 eight1 or even a less number of square feet of coated glass1 is sent through a sewing needle1 it will often give it polarity1 so that it will traverse when laid upon water4 ,in this experiment it is remarkable that if the needle be lying east and west1 that end of it which communicated with the positive coating will point towards the north2 but if the needle be struck while lying north and south1 that end of it which lay towards the north1 will1 in any case1 point north2 and the needle will acquire a stronger virtue in this than in the former case4 ,but if the needle be placed perpendicular to the horizon1 and the electric shock be given to either point of it1 the lower extremity will afterwards point north4 ,the electric explosion taken upon the leaves of certain flowers changes their colour4 ,if the ball of a thermometer be placed in a strong current of electricity1 the mercury or spirit will rise several degrees4 ,if a thin bottle be exhausted of air by means of an air pump1 it will receive a considerable charge of electricity1 by applying its bottom to an electrified prime conductor4 ,in performing this experiment the bottle is to be held by the neck or near the mouth1 and the electric matter will pass through the vacuum1 and along the inner surface of the bottle1 to the hand1 from that end of it which is nearest to the prime conductor4 ,the luminous appearance exhibited by this experiment is exceedingly beautiful in the dark1 especially if the bottle be of any considerable length4 ,it exactly resembles those lights which appear in the northern sky1 and which are called streamers or the aurora borealis4 ,if one hand be applied to the part of the bottle which was before presented to the prime conductor1 while the other remains at the neck1 a shock will be felt1 at which instant the natural state of the inner surface is restored by a flash1 which is seen pervading the vacuum between the two hands4--,the principle on which this experiment depends will be explained hereafter4 ,,chap4 ,,xi4 ,a description of the electrophorus1 and some of its phenomena accounted for4 ,the electrophorus is a machine1 consisting of two plates1 usually of a circular form4 ,at first the under plate was of glass covered with sealing wax2 but there is little occasion to be particular1 with regard1 either to the substance of the lower plate1 or to the electric with which it is covered2 a metallic plate however is preferable to a wooden one1 though the latter will answer very well4 ,this plate must be covered with an electric3 pure sulphur answers nearly as well as the dearer electrics gum lac1 sealing wax c4 ,the upper plate is made of brass1 or a piece of paste-board covered with tin foil or silvered paper1 which must be nearly of the same dimensions as the electric plate3 this plate must be furnished with an electric handle1 which1 by means of a metallic or wooden socket is fastened to its centre4 ,this instrument was invented by ,mr4 ,volta1 an ,italian philosopher4 ,the manner of using it is as follows4 ,first1 ,the under plate is excited1 by rubbing its coated surface with a piece of new white flannel1 or a fox's tail4 ,a hard shoe brush1 having the bristles a little greased1 will also excite sulphur very well4 ,when this plate is excited as much as possible1 it is placed on a table with the electric side uppermost2 the metallic plate is then laid on the excited electric2 then the metallic plate is touched with the finger1 or with any other conducting substance1 which receives a spark from it2 finally the metallic plate being held by the extremity of its electric handle1 is separated from the electric and after it is raised some distance1 it is1 on examination1 found strongly electrified1 with an electricity contrary to that of the electric1 and will give a strong spark to a conductor brought near it4 ,by placing the metallic plate upon the electric1 touching it with the finger and separating them successively1 a great number of sparks may be obtained1 apparently of the same strength1 and without exciting the electric again4--,if these sparks be repeatedly given to the knob of a coated jar1 it will become charged4 ,the action of these plates depends upon the principle already laid down 7page #bb17 that an excited electric has the power of inducing a contrary electricity in a body brought within its sphere of action4 ,the metal plate therefore1 when set upon the excited electric1 acquires a contrary electricity1 by giving its electric fluid to the hand or other conductor which touches it1 when the electric is positively electrified2 or by acquiring an additional quantity from the hand c4 when the electric is negatively electrified4 ,more fully to explain the principle here considered let the following easy experiment be made-- ,electrify any insulated conductor positively4 ,then if an electrometer#ae of cork balls be held at some distance from it1 the balls will diverge with negative electricity4 ,this may be proved by bringing a piece of excited glass near them1 as the balls will be attracted by it4 ,but if you present to them a piece of excited sealing wax1 they will immediately avoid it--that is1 supposing the glass to be excited always positively1 and the sealing wax always negatively4 ,again4 ,insulate1 in a horizontal position1 a metallic rod with blunt terminations1 and about two feet long4 ,we shall designate the ends of this rod by ,a and ,b4 ,let a cork ball electrometer be affixed to the extremity ,a2 then bring an excited glass tube within eight or ten inches of the other end ,b--the balls will immediately diverge with positive electricity4 ,if the tube be removed the balls will immediately collapse1 and no electricity will remain in them1 or in the rod4--,but if1 while the tube is near one end ,b of the rod1 and the balls diverge with positive electricity1 the other end ,a be touched with a finger or other uninsulated conductor1 the cork balls will immediately come together1 as if the rod were in its natural state3 but if1 in this state of things1 the excited tube be removed1 the balls will again diverge1 but with negative electricity1 shewing that the whole rod ,,ab is now under-charged4 ,this last experiment is thus explained4--,when the rod is in its natural state1 the electric fluid proper to it is equably distributed throughout the rod2 but when the excited glass tube is brought near one of its ends as ,b1 the fluid belonging to that end will be driven towards ,a2 which extremity becomes over-charged1 and the other extremity ,b under-charged2 yet the rod has no more electricity now than it had before1 and when the tube is removed beyond the sphere of its action1 the redundant fluid of ,a returns to its former place ,b1 and the equilibrium is restored4 ,but if the extremity ,a be touched1 while it is over-charged1 by a conductor1 this will carry off its superfluous fluid1 and leave the extremity ,a in its natural state1 the extremity ,b being at the same time negatively electrified3 and when the tube is removed1 part of the fluid naturally belonging to ,a goes towards ,b1 and the whole rod remains under-charged4 ,,chap4 ,,xii4 ,of electrometers4 ,we have already seen that it is a general law of electricity1 that similar electricities repel1 and that dissimilar electricities attract each other4--,on this law all electrometers are constructed4 ,in fact the cork balls1 which have been mentioned are electrometers1 and exhibit at once the most important phenomena for the explanation or ascertaining of which the instruments which bear this name are constructed4 ,still it is of use to see the application which may be made of this general principle4 ,it is applied to ascertain the quantity of the electric fluid collected either in a prime conductor or a coated jar2 and also the state of the atmosphere in regard to electricity1 and the character of that electricity at any particular time and place4 ,the instruments by which these purposes are effected we shall now shortly describe4 ,to ascertain the quantity of electricity in a prime conductor or jar1 an electrometer the most easily constructed and of the most general use has been invented by ,mr4 ,henley--called the quadrant electrometer4--,of this we have given a representation in the frontispiece1 7letter ,x47 ,it consists of a perpendicular stem formed at the top like a ball1 and at the lower end with a screw1 by which it is fastened to the prime conductor4 ,a graduated semicircle of ivory1 horn or stiff paper1 is fixed near the uppermost end of the stem4 ,a moveable index1 made of a slender piece of hickory1 extends from the centre of the graduated semicircle a little distance beyond its circumference1 having a small ball of cork or pith at its lower extremity4 ,when the conductor or jar is not electrified1 the index is parallel to the stem1 but when it is electrified the index recedes more or less1 according to the degree of the electrization1 which is marked on the graduated circle4 ,a simple atmospheric electrometer was constructed by ,mr4 ,cavallo in the following manner4-- ,to the end of a common fishing rod1 he affixed a slender glass tube covered with sealing wax1 and having a cork at its end1 from which two cork or pith balls were suspended by hempen strings4 ,from the other end of the rod proceeded a flaxen or hempen twine a little longer than the whole rod and tube1 with a pin attached to it1 which was stuck into the cork at the extremity of the glass tube1 for the purpose of taking off the insulation4 ,the twine1 to prevent its falling when the pin was pulled out of the cork1 was attached to the rod1 by a small string1 running from it and meeting the rod at a little distance from the glass tube4 ,to use this instrument1 let the pin be pushed into the cork4 ,then1 holding the rod by the extremity farthest from the cork balls1 project it out1 from a window in the upper part of the house1 into the air1 raising the end of the rod to which the balls are appended1 so as to make an angle of #ej or #fj1 with the horizon4--,after having kept it in this situation a few seconds1 by pulling the twine1 detach the pin from the cork4--,this leaves the electrometer insulated1 and electrified with an electricity contrary to that of the atmosphere4 ,now draw the instrument into the room and you may examine the quality of the electricity1 by applying the knob of a phial positively charged to one of the balls2 if the ball is attracted by the knob it is negatively electrified--if repelled1 positively electrified4 ,the satisfaction arising from these experiments is sometimes abated1 from the circumstance that the quantity of electricity obtained in this way1 is so small that its quality cannot be ascertained4 ,to remedy this inconvenience ,cavallo and ,nicholson1 have invented machines which they denominate doublers or multipliers of electricity4 ,but the structure of these machines is complex and delicate1 and the explanation of them is long1 and not easily understood without the aid of plates4 ,our epitome therefore does not admit of inserting them4 ,those who may choose to pursue the subject we refer to the writers above mentioned4 ,to prevent the inconvenience arising from wind and rain in the use of the atmospheric electrometer1 the following device has been used by ,mr4 ,cavallo4--,take a glass vessel open at top and bottom--cement it at bottom to a convenient piece of wood--let the upper part be tapering like the neck of a phial1 and cement into it a glass tube1 extending a little above and a little below the neck of the larger vessel4 ,cover the tube with sealing wax1 both within and without the neck of the vessel1 so as to give it the appearance of one body4 ,into this tube cement a brass wire extending a very little below the bottom of the tube1 and flattened at the lower end so as to be perforated with two small holes4 ,through these holes insert two flaxen threads1 or two very fine silver wires1 with small balls of cork or pith at the end of them1 and touching each other3--if wires are used they should be suspended by small rings at the top1 that they may act more easily4 ,let the top of the brass wire screw into a brass cover on the top of the whole vessel1 which cover will not only secure the vessel against rain1 but serve as a conductor to a very slightly electrified atmosphere--conveying the fluid1 first to the wire1 and by means of that to the balls1 which will exhibit1 within the vessel1 the state of electricity collected from the atmosphere4 ,there should be two narrow slips of tin foil stuck to the inside of the glass vessel1 and communicating with the wooden bottom1 which will serve to carry off that electricity which1 when the corks touch the glass is communicated to it1 and which1 if accumulated1 would disturb the free motion of the corks4 ,an useful alteration of this electrometer was made by ,mr4 ,bennet4 ,it consists of slips of gold leaf or silver leaf1 instead of the corks suspended by threads or wires4 ,these slips of leaf are to be suspended from the cover of a cylindrical vessel1 and hanging within it4 ,the slips of leaf are to be about two and an half inches long4 ,this electrometer is the most sensible instrument of the kind1 manifesting in an unequivocal manner very small quantities of electricity4 ,but this instrument is not as portable and easily managed as the other4--,if very fine threads1 stiffened with glue1 be used without any balls1 they will be found nearly as sensible as the gold leaf4 ,,chap4 ,,xiii4 ,the identity of electricity with lightning4 ,the identity of the electric matter with lightning is a discovery1 which has been of more use than any other in electricity4 ,that the effects of this fluid bore a great resemblance to those of lightning1 had been several times remarked by philosophers and especially by the ,abb ,nollet2 but that they should be found to be effects of the same cause1 and that the phenomena of electricity could be imitated by lightning1 or those of lightning by electricity1 was not suspected1 till our countryman ,dr4 ,franklin made the assertion in #agej1 and afterwards demonstrated its truth by undeniable experiment in #ageb4 ,this discovery is almost the only one in the whole science which has not been the result of accident4 ,the ,doctor had for a long time observed the effects of pointed bodies in drawing off the electric matter more powerfully than could be done by others4--,improving upon this1 he supposed that pointed iron rods1 raised to a considerable height in the air1 when the atmosphere was loaded with lightning1 might 8draw off the matter of the thunder-bolt1 without noise or danger40 ,as he was waiting for the erection of a spire in ,philadelphia1 that he might have an opportunity of ascertaining the correctness of his hypothesis1 it occurred to him1 that1 by means of a common kite1 he could have a readier access to the higher regions of the atmosphere than in any other way4 ,preparing therefore a large silk handkerchief1 and two cross sticks upon which he might easily extend it1 he took the opportunity of the first approaching thunder storm to walk into a field1 where there was a shed convenient for his purpose2 but1 dreading the ridicule which too commonly attends unsuccessful attempts in science1 he communicated his design to no one but his son1 who assisted him in preparing and raising the kite4 ,a considerable time elapsed before there was any appearance of success3 one very considerable cloud had passed over the kite without any effect2 when1 just as he was beginning to despair1 he observed some loose threads of the hempen string to stand erect1 and avoid one another just as if they had been suspended from the prime conductor of an electrical machine4 ,on this he presented his knuckle to a key which was fastened to the string1 and received a spark4 ,others succeeded even before the string was wet2 but when the rain began to fall he collected the electrical fire very copiously4 ,he afterwards had an insulated iron rod1 to draw lightning into his house1 and performed almost every experiment with real lightning1 that he had before made with electricity collected by a machine4 ,thus a new field was opened for the philosophy of electricity4 ,,chap4 ,,xiv4 ,of the structure and use of the electrical kite4 ,in the structure of an electrical kite1 the circumstances to be principally attended to are those near1 and on the ground4 ,silk being a non-conductor1 the end of the string which is held in the hand is to be of that substance--a silk handkerchief tied to the hempen twine of the kite will answer very well4 ,an iron key is to be tied on the hempen string1 an inch or two above its junction with the silk1 and from this key1 when the kite is electrified1 the sparks are to be received into a ,leyden phial1 to be used in the same manner as if it had been charged from the electrical machine4 ,as curiosity may prompt many to repeat the experiments made with this kite1 and as no experiments with atmospheric electricity can be made without some danger1#af we shall give the substance of ,mr4 ,cavallo's directions 7the best we are acquainted with7 relative to the forming and using of this instrument4--,he observes that the whole power of the machine lies in the string3 and that in other respects a common school boy's kite1 will answer the purpose as well as any other4 ,the string is made by twisting two threads of twine with one of brass wire or copper1 such as is commonly used for trimmings4 ,when a kite constructed in this manner was raised1 the string always gave signs of electricity except once1 when the weather was warm1 and the wind so weak that the kite could not be kept up for a few minutes2 afterwards1 however1 when the wind increased1 he obtained as usual a considerable quantity of electricity4 ,concerning the management of this kite he gives the following directions4-- ,in raising the kite when the weather is very cloudy and rainy1 at which time there is much danger of meeting a great quantity of electricity1 ,i usually hang upon the string a chain with one extremity touching the ground2 and sometimes ,i use another caution besides1 which is1 to stand upon an insulated stool2 in which situation1 ,i think that if any quantity of electricity1 suddenly discharged by the clouds1 strikes the kite1 it cannot much affect my person4 ,although ,i have raised my electrical kite a hundred times without any caution whatever1 ,i have very seldom received a few exceedingly slight shocks in my arms4 ,in time of a thunder storm1 if the kite has not been raised before1 ,i would not advise a person to attempt it while the stormy clouds are over head1 the danger at such time being very great1 even when every caution is used4 ,at that time the electricity of the clouds may be observed by means of a cork ball electrometer1 placed in an open situation4 ,but ,mr4 ,cavallo with all his caution could not avoid danger in making experiments on atmospheric electricity1 as appears from the following account of his observations on the #acth of ,october #aggc4 8,after having rained a great deal in the morning and the night before1 the weather became a little clear in the afternoon1 the clouds appearing separated and pretty well defined2 the wind was west and pretty strong2 the atmosphere was in a temperate degree of heat4 ,in these circumstances1 at three o'clock ,p4 ,m4 ,i raised my electrical kite1 with #cfj feet of string4 ,after the end of the string was insulated1 and a leather ball coated with tin foil1 hung to it1 ,i tried the power and quality of the electricity1 which appeared to be positive and pretty strong2 in a short time a small cloud passing over1 the electricity increased a little2 but the cloud being gone it returned pretty soon to its former degree4 ,the string of the kite was now fastened by a silk string to a post in the yard of the house2 ,i was repeatedly charging two phials1 and giving shocks with them3 while ,i was so doing1 the electricity1 which was still positive1 began to decrease1 and in two or three minutes it became so weak1 that it could hardly be perceived1 with a very sensible cork ball electrometer4--,observing at the same time that a large black cloud approaching the zenith1 7which no doubt caused the decrease of electricity7 indicated rain1 ,i introduced the end of the string through the window on the first floor1 where ,i fastened it by the silk to an old chair4--,the quadrant electrometer was set upon the same window1 and was1 by means of a wire1 connected to the string of the kite4 ,being now three quarters of an hour after three1 the electricity was actually imperceptible1 however in about three minutes it returned1 but now upon examination1 it was found to be negative1 which was evidently occasioned by the approach of the cloud1 which by this time had reached the zenith of the kite2 the rain also began to fall in large drops4 ,the cloud came farther on1 the rain increased and the electricity keeping pace with it1 the electrometer soon arrived at #ae4 ,seeing now that the electricity was strong1 ,i began again to charge the phials and to give shocks with them2 but the phials had not been charged more than three or four times1 before ,i perceived that the index of the electrometer was arrived at #ce1 and was still rising4 ,the shocks now being very smart1 ,i desisted from charging the phials1 and considering the rapid advance of the electricity1 thought to take off the insulation of the string1 that if it should farther increase it might be conducted silently to the earth1 without occasioning any bad accident4 ,to effect this1 as ,i had no proper apparatus near me1 ,i thought to remove the silk string1 and to fasten the twine itself to the chair4 ,i disengaged the wire which connected the electrometer with the string2 untied it from the silk1 and fastened it to the chair3 but while ,i was effecting this1 which took up less than half a minute1 ,i received twelve or fifteen very strong shocks1 which ,i felt all along my arms1 in my breast1 and legs1 shaking me in such a manner that ,i had hardly power to effect my purpose1 or to warn the people of the room to keep their distance4 ,as soon as ,i took my hands from the string1 the electricity 7in consequence of the chair being a bad conductor7 began to snap between the string and the window shutter1 which was the nearest conductor4 ,the cloud was now just over the kite2 it was black1 well defined1 and nearly of a circular form1 its diameter appearing to be about #dj2 the rain was copious but not remarkably heavy4 ,as the cloud was going off1 ,i went near the string1 and finding the electricity weak1 but still negative1 ,i insulated it again1 thinking to keep it up some time longer2 but observing that a larger and denser cloud was approaching1 ,i resolved to pull the kite in2 accordingly a gentleman1 who was near me1 began pulling it while ,i was winding up the string1 he told me he had received two or three slight shocks in his arms1 and if he should feel one more1 he would let the string go2 upon which1 ,i pulled the kite in as fast as ,i could myself1 without any further observation1 being ten minutes after four o'clock4 ,n4 ,b4 ,there was no thunder or lightning perceived that day1 nor for some days before1 nor afterwards4 ,the general laws which ,mr4 ,cavallo deduced from a variety of experiments made by means of electrical kites1 are the following3 #ast4 ,the air appears to be electrified at all times2 its electricity is always positive and much stronger in frosty than in warm weather2 it is by no means less in the night than in the day time4 #b;d4 ,the presence of the clouds generally lessens the electricity of the kite1 sometimes it has no effect upon it1 and it sometimes1 though rarely1 increases it a little4 ,to this the above mentioned instance is a remarkable exception4 #c;d4 ,when it rains1 the electricity of the kite is generally negative1 and very seldom positive4 #dth4 ,the aurora borealis seems not to affect the electricity of the kite4 #eth4 ,the electrical spark taken from the string of the kite1 or from an insulated conductor connected with it1 especially when it does not rain1 is seldom longer than the quarter of an inch2 but it is exceedingly pungent4 ,when the index of the electrometer is not higher than #bj the person who takes the spark will feel it in his legs2 it appearing more like the discharge of an electrical jar1 than the spark taken from the prime conductor of an electrical machine4 #fth4 ,the electricity of the kite is generally stronger or weaker1 according as the string is longer or shorter2 but it does not keep any exact proportion to it2 the electricity1 for instance1 brought down from a string of an hundred yards1 may raise the index of an electrometer to #bj1 when with double the length of string1 the index of an electrometer will not go higher than #be4 #gth4 ,when the weather is damp1 and the electricity pretty strong1 the index of an electrometer1 after taking a spark from the string1 or being presented to the knob of a coated phial1 rises surprisingly quick to its former place2 but in dry and warm weather it rises exceedingly slowly4 ,,chap4 ,,xv4 ,the structure and use of lightning rods4 ,since the discovery of the identity of lightning and the electric matter1 long rods of iron1 or other metals1 have been made use of1 with a view to protect buildings from the effects of lightning4 ,this is the most practical and important part of our whole subject1 and deserves to be treated with the utmost attention4 ,iron and copper are the metals which1 on account of their conducting power1 their cheapness1 and the quantity required for a lightning rod1 are principally used4 ,copper is preferable to iron4 ,care should be taken that the rod be not less than half an inch in diameter4 ,it is best to have it1 if possible1 of one continued piece4 ,if this be not practicable1 the pieces should be screwed into each other2 or at least so constructed that the rust will not separate the perfect metal of one piece from that of another2 because metallic rust is almost a non-conductor of electricity4 ,the rod should be fastened to the house by wooden cramps or staples1 rather than by those of metals of any kind2 because wood is neither so good a conductor of electricity1 nor so likely to promote the rust of the metal which it touches4 ,the rod should be raised above the top of the building or chimney to which it is attached1 at least five or six feet4 ,the point or points should be made very sharp1 and for a few inches should taper off in the form of a pyramid1 having all the corners or edges sharp4 ,it is not of much importance whether there be1 or be not1 more points than one4 ,if the means afterwards to be mentioned be not used to preserve the points from rust1 it may be of use to gild them2 and the gilding should extend downwards a foot or more4 ,it is better to paint the point of a rod1 than to leave it wholly unprotected against rust4 ,the lower end of the rod should be driven or sunk at least five or six feet into the ground1 and in a direction from the building4 ,if it can be connected with the water of a spring1 a well1 or a cistern1 it will be so much the better4 ,at powder-mills1 arsenals1 and all depots of inflammable materials1 it is better to attach the rod to a post1 raised for the purpose1 a foot or two from the building1 than to the building itself4 ,if the building be large1 there should be a rod at each end2 and it is an additional security1 if these rods be connected by a piece of metal1 running from the one to the other1 on the roof of the house4 ,if there be but one rod1 it should1 in this country1 be put on the western end of the house2 because thunder storms oftenest arise from that quarter4 ,if the position of the house affords but little choice in this respect1 the rod should be placed either on the kitchen chimney1 or as near to it as possible2 because smoke and heat are conductors1 and in the summer1 smoke and heat seldom ascend from any other chimney than that of the kitchen4 ,when there is a copper spout to a house1 the rod1 if convenient1 may be connected with it as a part of the conductor4 ,in this case however1 care should be taken to make the connexion complete1 both at top and bottom4 ,large barns and barracks1 have even more need of a rod to preserve them from lightning than a dwelling house1 because the vapour which ascends from them when filled with vegetable substances1 imperfectly dried1 is a powerful conductor4 ,ships1 and all vessels which have high masts1 have as much need of conductors as houses on the land4 ,copper conductors are in every view the best for ships1 as they will not contract rust from sea water4 ,a conductor1 of this metal1 should be attached to the highest mast of the vessel1 and extend three or four feet above its top4 ,it should be inserted into the side of the mast1 so as to leave the surface smooth1 be carried across the deck and over the side of the ship to the keel2 so that it may terminate where the lower extremity may be always under the water4 ,chains are often used as conductors to ships1 but they are far inferior to a piece of metal1 whose parts are not separated4 ,in the above directions it has been our aim to show in what manner structures may be best and most effectually protected against danger from lightning1 and whenever it is practicable the best means ought certainly to be used4 ,but it is to be remembered that where means the most effectual cannot be applied1 those of an inferior kind are not to be neglected4 ,a small rod1 however pointed or fastened to a house1 is unspeakably better than none1 and a chain should always be used in a ship1 if a rod cannot be obtained4 ,in ninety nine cases out of a hundred1 any metallic conductor1 reaching from the top to the bottom of a structure1 will preserve it from destruction by lightning1 and save the lives or property of the inhabitants1 when the whole might otherwise have been destroyed4 ,the points of rods have often been found melted by lightning1 and both they and the lower extremities are often injured by rust4 ,for an effectual method of preventing both these inconveniencies1 the public are indebted to ,robert ,patterson ,esq4 professor of mathematics in the ,university of ,pennsylvania1 and director of the ,mint of the ,united ,states4--,his memoir on the subject is as follows3-- 8,from the instances which now and then occur of houses being struck with lightning1 that are furnished with metallic conductors1 and the frequent instances of these conductors having their tops melted off by a stroke of lightning1 it appears that this admirable contrivance for guarding houses against the dangerous effects of lightning is1 in some degree1 still imperfect4 ,some improvement seems yet to be wanting at both extremities of the rod--at the upper extremity1 to secure it against the accident of being melted1 which renders it afterwards unfit to answer its original intention1 viz4 drawing off the electricity1 or lightning1 from the passing cloud1 in a silent imperceptible manner1 for it is only pointed conductors that possess this property--and at the lower extremity1 to afford a more ready passage for the fluid into the surrounding earth4 ,the first of these intentions1 would ,i am persuaded1 be effectually answered by inserting in the top of the rod a piece of black lead1 of about two inches long1 taken out of a good pencil1 and terminating in a fine point1 projecting but a very little above its metallic socket2 so that if the black lead point should happen to be broken off by any accident1 of which however ,i think there can be but little danger1 still the point of the rod would be left sharp enough to answer the purpose of a metallic conductor4 ,this substance is well known to be infusible1 by the greatest heat1 and hence its use in making crucibles2 nor is it evaporable as remarked by ,cronstedt1 in his mineralogy1 ,sect4 #bca1 except in a slow calcining heat1 to which it could never be exposed at the top of a lightning rod4 ,at the same time its power as a conductor of electricity is perhaps equal1 or but little inferior1 to that of any of the metals4 ,a line drawn on a piece of paper by a black lead pencil1 will as ,i have often experienced1 conduct an electric explosion seemingly as well as a similar line of gilding would do1 and that without ever loosing its conducting power1 which is not the case with gilding4 ,the second intention is1 to facilitate the escape of the electric fluid from the lower part of the rod into the surrounding earth4 ,it is in many cases impracticable1 from the interruption of rocks or other obstacles1 to sink the rod so deep as to reach moist earth1 or any other substance which is a tolerably good conductor of electricity4 ,nor1 even if this were practicable1 would it1 ,i presume1 be alone sufficient to answer the desired intention4 ,iron1 buried in the earth1 and especially in moist earth1 will presently contract a coat of rust1 which will continually increase till the whole is converted into rust1 but rust of iron1 and indeed the calx of all metals is a non-conductor1 or at most but a very imperfect conductor of the electric fluid4 ,hence it is easy to see1 that in a few years after a lightning rod has been erected1 that part of it which is under ground will contribute little or nothing towards the safety of the building4 ,besides1 the surface of this part of the rod is too small to afford an easy and copious discharge of the electric fluid into the surrounding earth1 when this is but an imperfect conductor4 ,as a remedy for these defects ,i would propose1 that the parts of the rod under ground be made of tin1 or copper1 which are far less liable to corrosion or rust1 by lying under ground than iron4--,or1 which perhaps would answer the purpose better1 let this end of the rod1 of whatever metal it be made1 be coated over with a thick crust of black lead1 previously formed into the consistence of paste1 by being pulverised and mixed with sulphur 7as in the manufactory of the ordinary kind of black lead pencils7 and then applied to the rod while hot4 ,by this means1 the lower part of the rod would1 ,i apprehend1 retain its conducting power for ages1 without any diminution4 ,in order to increase the surface of the lower part of the conductor1 let a hole or pit1 of sufficient extent1 be dug as deep as convenient2 and into this pit let there be put a quantity of charcoal1 round the lower extremity of the rod4 ,charcoal possesses two properties1 which1 in a peculiar manner1 fit it for answering the purpose here in view4--7#ast47 ,it is a very good conductor of electricity and1 7#b;d47 ,it will undergo little or no change of property by lying ever so long in the earth4 ,thus might the surface of that part of the conductor1 in contact with the earth1 be increased1 with little trouble or expense to any extent at pleasure2 a circumstance which every one acquainted with electrical experiments1 must acknowledge to be of great importance to the end here proposed40 ,the following experiments with a thunder-house1 shew the utility of lightning rods1 and ascertain what termination of the rod best answers the end proposed4 ,to shew the effect of lightning on a house not furnished with a conductor1 or when the conductor is discontinued4 ,provide yourself with the model of a house made of tin1 four inches in breadth1 six long1 and about five in height4 ,let there be a chimney placed in the roof equidistant from both ends1 and let a glass tube pass through it1 the upper extremity of which must reach a little above the chimney1 and the lower one come within an inch of the floor of the house4--,let a small wire pass through the bore of the glass tube1 the upper end of which must extend a small distance above the orifice of the tube1 having its extremity1 which must be pointed1 furnished with a screw1 on which a metallic ball is to be fastened4 ,the other end must likewise have a ball fixed upon it4--,the instrument being thus prepared1 fill the house with cotton1 and sprinkle a little powdered rosin on that part of it1 which is immediately between the lower knob of the wire1 and the floor of the house4 ,then connect the lower part of the instrument with the outside coating of a pretty large jar4--,from the prime conductor1 in order to represent the clouds1 suspend a small scale beam1 having two balls of metal or wood coated with tin foil1 in the place of the scale dishes1 nicely balanced4 ,the knob of the jar being connected with the prime conductor2 bring the ball on the wire extending through the glass tube1 under one of the balls representing a cloud4--,now charge the jar4 ,the cloud will be attracted by the ball on the wire--the electricity of the cloud will be discharged--and if the experiment succeeds1 the contents of the house will be set on fire4 ,the effects of lightning1 when a house is furnished with a pointed conductor4 ,repeat the above experiment with this variation3 unscrew the ball from the upper extremity of the wire of the house1 so that it may remain pointed4 ,place the house under the cloud as in the former experiment4--,you will now find it impossible to charge the jar3 or if you charge the jar before the house is placed under the cloud2 the cloud1 instead of being attracted by it1 will be repelled1 and the jar will be discharged without any explosion1 and without firing the cotton4 ,these two experiments evince that pointed conductors are more proper to secure houses from the effects of lightning that those terminating with a ball or knob1 and that if the pointed conductors fairly act on the cloud the security is complete4 ,,chap4 ,,xvi4 ,of animal electricity4 ,the electric power1 observed by the ancients only in amber1 and perhaps the tourmaline1 was in process of time found to be in glass1 rosin1 silk1 and several other substances4 ,by degrees it was discovered1 that very strong signs of electricity were exhibited by a number of animals4 ,the experiment of producing sparks of electrical fire1 by rubbing the back of a cat in frosty weather1 proved that electricity might exist in a very active state in the bodies of animals1 without injuring their functions4 ,from animals of an inferior kind a transition was made to the human species4 ,some people were observed to have a remarkably bright lustre of their eyes1 others were found to be so strongly electrified naturally1 that a very sensible electrometer was perceptibly affected1 when brought near them4--,others1 it is affirmed1 were found so sensible to the presence of electricity1 as to be affected by a flash of lightning1 though so distant that the thunder could not be heard4 ,but what principally claims our attention in regard to this part of our subject is1 that there are unquestionably certain animals which can at pleasure give an electric shock1 of sufficient force to kill other small animals1 and that in fact they often do it4 ,we shall describe only three of the most remarkable of these electric animals--the ,gymnotus electricus1 the ,torpedo1 and the ,silurus electricus4 ,the ,gymnotus is a genus of fishes1 belonging to the order of apodes4 ,they have two tentacula at the upper lip2 the eyes are covered with the common skin4--,there are five rays in the membrane of the gills2 the body is compressed1 and carinated on the belly with a fin4 ,there are five species2 the most remarkable is the electricus1 commonly called the electric eel4 ,this species is peculiar to the ,surrinam river1 and they inhabit the most rocky parts of it1 at a considerable distance from the sea4--,the most accurate description of this fish1 is in the ,philosophical ,transactions1 for #agge1 where ,alexander ,garden ,m4 ,d4 gives an account of three of them brought to ,charleston in ,south ,carolina4 ,the largest was about three feet eight inches long1 and from ten to fourteen inches in circumference1 about the thickest part of the body4 ,the head was large1 broad1 flat1 and smooth1 impressed here and there with holes1 as if perforated with a blunt needle1 especially towards the sides1 where they are more regular4 ,there are two nostrils on each side2 one is large1 tubular1 and elevated above the surface2 the other small and level with the skin4 ,the mouth is large1 but the jaws have no teeth1 so that the animal lives by suction1 or by swallowing its food entire4 ,the eyes are small1 flat1 and of a blueish colour1 placed a little behind the nostrils4 ,the whole body from a few inches below the head1 was distinguished into four longitudinal parts1 clearly divided from each other by lines4 ,the carina begins a few inches below the head1 and widening as it proceeds1 reaches as far as the tail1 where it is thinnest4 ,the situation of the anus is very remarkable1 being an inch more forward than the pectoral fins4 ,across the body1 there are a number of small bands1 annular divisions1 or rather rug of the skin2 by means of which the fish seems to partake of the vermicular nature1 having the power of lengthening and shortening its body like a worm1 and by means of which it can swim backwards as well as forwards4--,for an anatomical description of this fish1 see the appendix to the #b;d4 vol4 of ,mr4 ,cavallo's 8,complete treatise0 page #cjc4 ,the ,gymnotus has the astonishing property of giving the electric shock to any person or number of persons1 either by the immediate touch of the hand or by the mediation of any metallic conductor4 ,the shock is interrupted by the intervention of a non-conducting substance4 ,if the animal be touched only with one hand1 a kind of tremor is felt in that hand only4 ,the power of giving shocks depends entirely on the will of the animal4 ,as nature is ever provident for her creatures1 both with regard to their preservation and support1 she has endowed the ,gymnotus with a peculiar instinctive faculty1 so that if it be pursued by an enemy1 it never fails to communicate a shock1 in consequence of which it eventually makes its escape4 ,in obtaining food it likewise makes use of its electrical property by which it kills small fish1 and afterwards devours them4 ,but the most remarkable instinct of this fish is1 that when any substance approaches it1 it is sensible whether it be a conductor or non-conductor4 ,in order to exhibit this wonderful phenomenon1 a variety of methods were contrived1 the easiest and most satisfactory one was the following4 ,the extremities of two wires were dipped into the water of the vessel1 in which the animal was kept1 after which they were extended to a considerable distance1 where they terminated in two separate glasses full of water4 ,these wires being supported by silk at some distance from each other1 the circuit was1 of course1 incomplete4 ,in these circumstances if a person completed the circuit1 by placing one hand in one of the glasses and the other in the other1 the fish which never went purposely towards the wires1 while the circuit was interrupted1 would now go immediately towards them and give the shock1 and this though the completion of the circuit was made out of his sight4 ,the next electrical fish we are to mention is the ,torpedo2 a genus of fishes belonging to the order of ,chondropterygia2 the species of this genus are remarkable and numerous2 but we must content ourselves with the sixth species1 called the electrical ray1 or cramp fish1 or ,torpedo4 ,the head and body1 which are indistinct1 are nearly round1 the ventral fins form on each side the quarter of a circle1 the two dorsal fins are placed on a trunk of the tail1 which is round1 the caudal fin is broad and abrupt4 ,the eyes are small1 and placed near each other2 behind each is a round spiracle with six small cutaneous rags on their inner circumference4--,the mouth is small1 and the teeth are minute and spicular4 ,these fish have been taken in ,torbay1 off ,pembroke1 near ,waterford in ,ireland1 and many other parts of ,europe1 with a trawl1 and sometimes with a bait2 they commonly lie about forty fathoms deep4 ,the food of the ,torpedo is fish4--,for an anatomical description we refer the curious reader to one given by ,mr4 ,hunter1 in the ,philosophical ,transactions1 vol4 #fc4 ,the electrical properties of this fish are remarkable2 for a long time they were considered as fabulous2 but the fact having been ascertained beyond the possibility of doubt1 it was endeavoured to be accounted for1 by a variety of ingenious though unsatisfactory arguments4 ,but when the phenomena of electricity began to be better understood1 considerable light was thrown upon the subject2 and ,mr4 ,walsh at last1 not only explained the phenomena which generally attend it1 on the known principles of electricity1 but actually contrived an artificial fish1 by which a shock very similar to that of the natural one can be given4 ,the electrical power of the ,torpedo is conducted by the same substances as conduct common electric matter1 and is interrupted also by the same non-conductors3 but its shock will not pass over the least interception of the circuit1 not even if a chain be used4 ,this singular fact was also imitated by ,mr4 ,walsh with his artificial ,torpedo4 ,it has not been in our power to obtain a particular account of this artificial ,torpedo of ,mr4 ,walsh4--,but we know that one may be formed in the following manner4 ,let a number of small thin lamin of talc1 commonly called isinglass1 or thin sash glass1 coated in the usual way1 be joined together in the same manner as in the battery4 ,let these be placed in the body of an artificial fish resembling the ,torpedo4--,let them then be charged1 and on being touched1 the same phenomena which accompany the real ,torpedo will ensue2 except that the shock of this will not be impeded by a small interruption in the circuit4 ,similar effects may also be produced1 by means of a large battery weakly charged and furnished with ,lane's electrometer4 ,the third and last fish that we shall mention1 is the ,silurus or ,silurus electricus1 a genus in ,ichthyology belonging to the order of ,pisces ,abdominales4--,the body of this is long1 smooth1 and without scales1 being rather large and flattened towards the lower part4 ,the eyes are of the middle size and covered by the skin which envelopes all the head4 ,each of the jaws is furnished with a great number of small teeth4 ,about the mouth it has six filamentous appendices1 two from the upper1 and four from the under lip4 ,the colour of the body is greyish1 with a few dark spots towards the tail4 ,with regard to its electrical properties very little is known1 enough however to entitle it to the name of electricus4 ,,chap4 ,,xvii4 ,the influence of electricity on vegetables4 ,with regard to this part of our subject there has been considerable controversy between philosophers1 some of them asserting that electricity is unfavourable1 and others that it is advantageous to vegetation4 ,it was asserted by the ,abb ,bertholon1 in his book entitled ,electricit des meteores1 that plants situated near a metallic conductor increased considerably in consequence of their situation4 ,and1 on the other hand1 ,giardini says that plants growing near such conductors are generally unhealthy1 and produce very little fruit1 but upon removing the conductor the plants become luxuriant and fruitful4 ,the ,abb ,bertholon in endeavouring to establish his opinion1 constructed what he called an electro vegetometer by means of which the electricity of the atmosphere may be collected in abundance4 8,this apparatus 7says he7 having been raised with care in the midst of a garden1 the happiest effects were perceived1 viz4 different plants1 herbs and fruits1 in greater forwardness than usual1 more multiplied and of better quality40 ,these facts are analogous to an observation that ,i have often made1 viz4 that plants grow best1 and are more vigorous near thunder rods1 where their situation favours their developement4 ,they likewise serve to explain why vegetation is so vigorous in lofty forests1 and where the trees raise their heads far from the surface of the earth1 so that they seek as it were the electric fluid at a far greater height than plants less elevated3 while the sharp extremity of their leaves1 boughs and branches serve as so may points granted them1 by the munificent hand of nature1 to draw down from the atmosphere that electric fluid which is so powerful an agent in forwarding vegetation1 and in promoting the different functions of plants4--,such are the theory and experiments of the ,abb1 but ,doctor ,ingenhaus1 in two letters to ,mr4 ,molitor1 published in the journal de physique for #aghf-hh has shewn the fallacy of the theory1 by exposing the insufficiency of the experiments upon which it was established4 ,we shall translate a few passages from the ,doctor's letter1 which will shew us his opinion and the result of his experiments4 ,i have frequently made experiments of this kind by exposing plants to a weak degree of electricity1 and at other times to a considerable quantity1 without ever being able to observe that plants under its influence prospered more than those which were not electrified at all4 ,it even appeared to me more than once1 that those which had been electrified were a little less thrifty than those which were not electrified4 ,in another place he says1 ,not being content with these experiments1 ,i have made others infinitely more conclusive1 by strewing seeds of mustard and cresses1 over the largest plates of delf that ,i could procure1 covering them with brown paper1 and sprinkling them continually with a sufficiency of water4 ,each of these plates was covered with more than a thousand seeds2 ,i kept them electrified night and day1 according to the method which ,mr4 ,schewankhard directed1 in a letter quoted by ,mr4 ,elermann1 but which ,i shall not repeat in this place1 lest ,i should swell this memoir3 the vegetation of these little shrubberies was always more or less precarious1 in proportion to the greater or less quantity of light that they received2 the electricity really contributing nothing to advance the growth3 thus the controversy stands1 we leave the reader to form his own opinion4 ,that some plants are more affected than others by electricity is an unquestionable fact4 ,it is however not true as some have affirmed1 that the contractions of the mimosa or sensitive plant1 are attributable to this cause4 ,the plant is equally affected when touched either by a conductor or an electric4 ,,chap4 ,,xviii4 ,medical electricity4 ,electricity has one advantage over other medical applications1 in as much as it may be applied to the healthy1 as well as the diseased part of the body1 without proving prejudicial1 and because it requires rather a nice application1 than a perfect knowledge of the complaint4 ,in a number of cases it has unquestionably proved salutary4 ,when electricity was first used in removing bodily complaints1 it was done only by means of the ,leyden phial pretty highly charged2 but this mode of administering it1 was strenuously opposed by ,mr4 ,lovet1 who was a celebrated electrical practitioner1 and in an essay called ,subtil medium proved1 asserts that electricity should be used in small sparks1 by which mode of treatment he affirms he scarcely ever failed curing or at least relieving his patients4 ,the apparatus for medical electricity in addition to the machine described in chapter ,,iv1 is an insulating stool4 ,this stool is made in the common way1 only that the feet must be of glass1 the upper or wooden part1 should be about three feet square1 so that a chair or bench may conveniently stand upon it2 care must be taken to leave no sharp edges about the stool4 ,for a representation of one1 see plate letter ,w4 ,the next instrument necessary for the electrical physician is a coated jar1 furnished with ,mr4 ,lane's electrometer4 ,this instrument is made in the following manner4 ,from the wire extending beyond the mouth of the jar1 at about four inches from the upper extremity1 let a piece of glass or baked wood three inches long1 project at right angles4 ,at the outer extremity of this stem let another piece of baked wood three inches long1 be fixed parallel to the rod of the jar2 the upper end of the parallel stem must be furnished with a brass socket1 through which a graduated wire may easily pass4 ,this wire must be furnished with a knob upon the end which is next the jar1 and a hook or ring at its other extremity1 to which a chain connected with the outer coating of the jar must be attached4 ,from this construction it is readily perceived that the force of the discharge or shock1 will be proportioned to the distance of the ball of the electrometer1 and the usual ball of the jar2 i4 e4 when the shock is large it will pass from one knob to the other at a larger distance1 and when small at a smaller distance1 and thus the distance will be the measure of the shock4--,the next thing to be provided is a ball1 either of metal1 or of wood covered with tin foil2 this must have a metallic handle1 which may be separated from the ball at pleasure1 having at one of its extremities a sharp point to receive a stream of electric fire2 small pointed pieces of wood made in a conical shape1 may be fixed on this point1 when the patient requires a degree of electricity between a spark and a stream4 ,the bottle director is the next instrument to be described4 ,it is exactly the same with the common ,leyden phial1 with the addition only of a hook cemented to the bottom4 ,to use this director 7suppose for instance you wished to pass a shock through the arm7 let a communication be made between its inner coating and the prime-conductor1 by which means it will be charged2 then let a chain be fastened1 by one end1 to the hook which is at the bottom2 then by applying the other end of the chain 7which may be furnished with a ball7 to one side of the arm1 and the knob of the jar to the other1 a shock will be given4 ,these are the instruments for the electrical physician4 ,we are now to describe the manner in which electricity may be applied to the best advantage4 #ast4 ,by simply placing the patient upon the electrical stool4 ,while the machine is in action the patient constantly emits the overplus of the electric fluid that he receives1 which continually passes off from every part of his body1 and produces a salutary effect4 ,it may be suspected that so gentle a treatment could have but little influence4 ,it is however upon good authority we assert1 that nervous and sedentary persons have derived considerable advantage from this mode of application4 #b;d4 ,by electric friction4 ,let the part affected be covered with a piece of flannel or woollen cloth1 and place the patient upon the insulated chair1 and connect him with the prime-conductor2 then take a metallic ball1 communicating with the earth1 and rub it over the flannel or woollen cloth4 ,electricity thus applied has often removed violent spasms1 and many other afflicting complaints4 #c;d4 ,by drawing sparks4 ,let the patient1 as in the last instance1 be placed upon the insulated stool1 and connected with the prime-conductor2 then bring the metallic ball1 communicating with the ground1 within about half an inch of the part affected1 and sparks will pass from it to the ball4 ,cutaneous eruptions1 scrophulous tumours and deafness1 are frequently benefitted1 and sometimes removed1 by this method of application4 ,deafness1 in particular1 has been entirely cured by the electric spark1 when every other remedy has proved ineffectual4 ,one of these cases came under our own observation4 ,a gentleman who was affected with an almost total loss of hearing for more than six months1 was advised by his physician to make a trial of electricity as a remedy4 ,he applied to us1 and was under our care about four or five weeks1 when he left us almost entirely recovered4 ,this gentleman was treated in the following manner4 ,we placed him on an insulated chair communicating with the prime-conductor4 ,then1 with a blunt pointed wire inserted into a glass tube1 we drew sparks from the meatus auditorius4 ,this operation was continued for eight or ten minutes1 at every visit4 ,he commonly attended us twice or thrice a week4 ,we were fully persuaded that the cure would have been more speedy1 if he had received the electricity more frequently4 #dth4 ,by the stream4 ,place the patient as in the two last instances2 then bring the point1 instead of the ball1 near the part affected4 ,when the electrical stream is to be applied the wooden point is preferable to the metallic one4 ,inflammations and other diseases of the eyes1 and several other disorders1 have been thus removed4 #eth4 ,by the director4 ,place the patient on a chair--insulation in this case being unnecessary4 ,then lay the ball1 which communicates with the outside coating of the director1 upon the affected part2 after which1 bring the director1 which must have been previously charged1 near any other part of the body1 and the intended operation will be performed4 ,it is impossible to tell the precise quantity of electricity which ought to be administered in every complaint1 because persons who are affected with the same disease will sometimes require very different degrees of electrization1 which must be judged of by the nature of their constitution1 their habits of body1 and other circumstances4 ,small sparks will sometimes have more effect upon a delicate and irritable constitution1 than pretty powerful shocks upon others4 ,the ,leyden phial1 with ,mr4 ,lane's electrometer1 is the most convenient instrument for sending shocks of different powers through particular parts of the body4--,to use this4--,let the wire of the electrometer be placed at the proper distance for the required shock2 connect a chain or wire1 communicating with this1 with the part affected--and let a communication be made between any other part of the body and the outside coating of the phial4 ,now turn the cylinder1 and the phial1 when it has received the proper charge1 will discharge itself through the circuit formed by the chains or wires1 and the part of the patient which was to be subjected to the shock4 ,,chap4 ,,xix4 ,directions concerning the use of the electrical apparatus1 with some practical rules for performing experiments with it to the best advantage4 ,the machine described in ,chapter ,,iv1 or one similar to it1 is capable of exhibiting the principal electrical phenomena1 provided it be skilfully managed2 but without such management it will constantly disappoint the electrician1 and prove of little use4 ,let the following directions and observations1 then1 be attentively regarded4 #a4 ,keep all the instruments as free as possible from dust and moisture4 #b4 ,when the weather is clear1 the air dry and a little cold1 the electric fire may be easily and copiously collected4 ,but when the weather is hot or damp1 the electrical machine is much less powerful4 #c4 ,before the machine is used1 the cylinder should be wiped clean1 with a linen cloth that is soft1 dry1 and warm2 after which a clean hot piece of flannel1 or old silk handkerchief1 may be applied with advantage4--,this done1 if the cylinder be turned pretty fast1 when the prime conductor and other instruments are removed1 the electricity1 upon applying the knuckle or other conductor1 will issue from the glass with a crackling noise1 accompanied with sparks2 this indicates the machine to be in good order1 so that the electrician may proceed to perform his experiments4 ,but if1 when the cylinder is turned and the knuckle applied1 no sparks be perceived1 then the fault is most probably in the rubber4 ,if so1 it must be removed and held to a fire1 so that its silk part may be dried4 ,then take a little tallow from a candle and just pass it over the leather of the cushion1 after which spread upon it1 a little amalgam1 and force it as much as possible into the leather4 ,replace it1 and let the cylinder be again wiped2 the machine is fit for use4 #d4 ,sometimes the electric matter will not be well collected1 because the machine is not sufficiently supplied with it from the earth2 which happens1 when the table upon which the electrical machine is placed and to which the chain or wire of the rubber is connected1 is very dry1 and consequently a bad conductor4 ,in this case1 the best method is to connect the chain or wire of the rubber with some moist ground1 or with the iron-work of a water-pump1 if convenient4 ,thus the rubber will be supplied with as much of the electric fluid as is required4 #e4 ,when the cylinder is very hot 7say above #aaj of ,fahrenheit's thermometer17 it will not collect the electric fluid well4 #f4 ,when a sufficient quantity of amalgam has been accumulated upon the leather of the rubber1 and the machine does not work well1 then1 instead of putting more upon it1 a small quantity of that which is already on the leather must be taken off4 #g4 ,after the cylinder has been used for some time it will contract black streaks1 which continually increase1 and greatly obstruct its electric power4--,these streaks must be taken off1 and the glass frequently wiped to prevent their being again formed4 #h4 ,coated jars1 before they are used1 ought to be made a little warm4 ,if this be done1 they will receive and retain the charge much better4 #i4 ,if one of the jars of a battery1 as is sometimes the case1 make a spontaneous discharge prematurely1 it will of course discharge the whole battery2 and in such case the faulty jar should be exchanged for one which is free from this defect4 #aj4 ,in making the discharge of an electrical battery1 or of a single jar1 the electrician must be careful not to place the discharging-rod upon the thinnest part of the glass1 as that may cause the bursting of the jar4 #aa4 ,in large batteries1 some of the jars frequently burst in the discharge4 ,to remedy this inconvenience1 ,mr4 ,nairne says that the discharging-rod should never be made of a good conducting substance1 except the circuit be at least five feet long4 ,but here it may be remarked1 that the length of the circuit weakens the force of the shock proportionably2 the highest degree of which is in many instances required4 ,when a coated phial is cracked1 either by a spontaneous discharge or otherwise1 the outside coating must be removed from the fractured part2 then make it moderately hot by holding it near the fire2 in this situation apply burning sealing-wax to the part1 so as to cover the fracture completely1 taking care that the thickness of the wax be rather more than the thickness of the glass2 lastly1 cover all the sealing-wax1 and part of the glass beyond it1 with a composition made of four parts of bee's-wax1 one of rosin1 one of turpentine1 and a little oil of olives3 which composition must be spread upon a piece of oiled silk1 and applied in the form of a plaister4 ,in this manner jars which have been broken may be repaired effectually4 #ab4 ,when a jar1 and especially a battery1 has been discharged1 the wires ought not to be touched with the hand before the discharging-rod has been applied a second1 and even a third time2 as there generally remains a residuum of the charge1 which is sometimes very powerful4 ,this residuum is in a great measure occasioned by the electricity1 which1 when the jar is charging1 spreads itself over the uncoated part of the glass1 and which is not discharged at first1 but gradually returns to the coating after the first discharge is made4 #ac4 ,when an experiment is to be performed which requires only a small part of the apparatus1 the remaining part should be removed from the table4--,candles should never be placed near the prime-conductor2 for the effluvia of their flames carry off much of the electric matter4 #ad4 ,one or two inches of the lower part of a ,leyden phial should be coated with some thick paint1 in order to prevent the amalgam1 which is often scattered upon the table1 from corroding the tin-foil1 and thereby diminishing the charge4 #ae4 ,when a prime-conductor is used1 those sparks are strongest which are taken from the extremity farthest from the cylinder4 #af4 ,the longest sparks are drawn from any conductor along an electric substance4 ,thus1 if the conductor be supported by pillars of glass or baked wood1 the longest sparks may be taken close to the pillar4 ,if the conductor be bent a little inward1 so as to make the surface concave1 a particularly large and undivided spark may be drawn from that place3 but where the surface is convex1 the spark is more apt to be divided and weakened4 #ag4 ,it sometimes happens that cylindric or globe machines do not work well1 owing to the air within them being too much rarefied by the heat of the cement1 when the caps are fixed on4 ,to remedy this1 a small hole may be bored through one of the caps1 so as to admit air into the cylinder or globe4 #ah4 ,if the electric by any means become scratched1 the working of the machine will be greatly impeded1 if not altogether prevented4 ,this is accounted for upon the principle that smooth and rough glass electrify differently when excited by the same rubber1 and the two different states destroy one another4 ,this may be remedied by filling up the scratches with a little tallow4 ,,epitome ,,of ,,electricity4 ,,division ,,ii4 ,,chap4 ,i4 ,entertaining ,experiments1 made by electrical ,attraction and ,repulsion4 ,electric attraction and repulsion1 observed in excited amber1 was1 as we have already had occasion to remark1 the first phenomenon which was noticed in the science of which we treat4 ,we have also hinted that1 to the present time1 no explanation of this attraction and repulsion which is entirely satisfactory1 has been given4 ,facts1 however1 are known in abundance2 and certain principles1 relative to this part of our subject1 are clearly ascertained4 ,to exhibit and illustrate these has been our object in selecting the following experiments2 some of which may be considered as intended chiefly for amusement1 but all of which1 if thoroughly comprehended1 will serve to fix the principles of the science more deeply in the mind of a learner4 ,,experiments4 ,the self-moving ,wheel4 ,this machine was invented by ,dr4 ,franklin4 ,it is made of a thin round plate of window-glass1 #ag inches in diameter1 covered on both sides with tin-foil1 except about two inches next the edge4 ,two small hemispheres of wood are cemented to the two sides centrally opposite1 and in each of these a strong thick wire eight or ten inches long is placed2 and these form the hub and axis of the wheel4 ,it turns horizontally on a point at the lower end of its axis1 which must be insulated4 ,the upper end of the axis1 passes through a hole in a thin plate of brass1 cemented to a strong piece of glass or baked wood1 which keeps it six or eight inches distant from any non-electric1 and is furnished with a ball of wax or metal on the top1 to keep in the fire4 ,in a circle on the table which supports the wheel1 are fixed twelve small pillars of glass about four inches apart1 with a thimble or metallic ball on the top of each4 ,on the edge of the wheel is a small metallic bullet1 communicating by a wire with the upper coating of the wheel2 and about six inches from it1 is another bullet communicating1 in like manner1 with the lower coating4 ,when the wheel is to be charged by the upper coating1 a communication must be made from the under one to the table4 ,when it is well charged it begins to move2 the bullet nearest to a pillar is attracted by the thimble or bullet on that pillar and passing by1 electrifies it1 and is immediately repelled from it2 the succeeding bullet1 which communicates with the other coating of the glass1 more strongly attracts that thimble1 on account of its being previously electrified by the other bullet2 and thus the wheel increases its motion1 till its velocity is regulated by the resistance of the atmosphere4--,the wheel will turn half an hour1 and make1 one minute with another1 #bj turns in a minute1 which is #fjj turns in the whole2 the bullet of the upper coating giving1 in each turn1 #ab sparks to the thimbles or balls1 which make #gbjj sparks2 and the bullet of the under coating receiving as many from the thimbles2 those bullets moving in the time near #bejj feet4 ,the thimbles are well fixed1 and in so exact a circle1 that the bullets may pass within a very small distance of each of them4 ,if1 instead of two bullets1 there be eight1 four communicating with the upper1 and four with the under coating1 placed alternately1 the motion will be considerably increased1 but then it will not continue so long4 ,these wheels may be applied to the ringing of chimes1 and the moving of light-made orreries4 ,the electrical ,dance4 ,suspend from the prime-conductor1 by means of a hook1 a metallic plate1 six inches in diameter4 ,about three or four inches from this1 and directly under it1 place another plate of the same kind1 communicating with the earth4 ,upon the lower plate1 throw small painted figures of men and women1 cut in paper1 or made of the pith of elder4 ,now1 if the cylinder be turned1 the figures will begin to move between the plates1 leaping from one to the other1 with surprising velocity1 exhibiting many curious and ludicrous attitudes and motions4 ,the electrified ,bells4 ,the phenomena of attraction and repulsion may be very satisfactorily shown with the electrified bells4 ,in order to make this experiment1 provide yourself with a piece of wire1 furnished with a hook equidistant from both ends1 and by which it may be suspended from the prime-conductor4 ,at each end of this wire suspend a small bell by a chain or wire2 and from the middle point between these two bells1 suspend a third1 by a silk thread2 let a clapper be hung between each of the bells1 also by silk threads4 ,from the concave or under side of the middle bell let a chain proceed1 communicating with the table1 and having a silk thread at its extremity4 ,now if the cylinder of the machine be turned1 the clappers will fly from bell to bell with a very quick motion1 and the bells will ring as long as the electrization continues4 ,the two outer bells1 being suspended by chains or wires1 are electrified first2 hence they attract the clappers2 and having communicated to them part of their electricity1 repel them4 ,the middle bell1 which is in its natural state1 now attracts them1 and deprives them of their acquired electricity2 after which they are again attracted by the outer bells1 and again repelled4 ,if1 by holding the silk thread1 the chain of the middle bell be raised from the table1 the bells1 after ringing a short time1 will stop2 because the middle one1 being insulated1 will soon become as strongly electrified as the other two2 in which case1 the clappers being equally attracted by both bells1 must discontinue their motion towards either4 ,if the experiment be made in a darkened room1 a spark will be seen between the clapper and bells1 at every stroke4 ,this experiment will have a better effect1 if1 instead of keeping the machine in motion1 a charged jar be placed in contact with the prime-conductor2 and when joined with the preceding experiment1 the whole will have the appearance of an electrical ball4 ,the inflammable air ,balloons4 ,the following experiment may serve to illustrate some of the phenomena observed in thunder storms4 ,provide two balloons1 made of the allantoides of a calf1 containing about two cubic feet1 and fill them with inflammable air4 ,to each of these attach1 by a silk thread about eight feet long1 a weight sufficient to prevent their rising higher than the above distance in the air4 ,then connect one of them with the positive1 and the other with the negative conductor1 or insulated rubber of the machine1 by very thin wires1 thirty feet long3 keep them a considerable distance asunder1 and as far from the machine as the wires will admit4 ,on being electrified1 the balloons will rise as high in the air as the silk thread will allow them1 then attract each other1 and uniting as it were in one cloud1 will gradually descend4 ,the rising of these balloons is attributed to the expansion of the air contained in them1 in consequence of the repulsive power communicated to its particles by the action of the electric matter upon them4--,when in contact1 their opposite electrical powers destroy one another1 and they descend in consequence of the condensation of the internal air4 ,dr4 ,franklin's ,experiment for illustrating his ,theory of ,thunder ,storms4 ,take two round pieces of paste-board1 two inches in diameter2 from the centre and circumference of each of them suspend1 by fine silk threads eighteen inches long1 seven small balls of wood1 or seven peas1 equal in size1 so that the balls appended to each paste-board will form equilateral triangles1 one ball being in the centre and six at equal distances from that1 and from each other1 around the circumference4 ,thus they represent particles of air4 ,dip both setts in water2 and some of it adhering to each ball1 they will represent air loaded with moisture4 ,electrify one sett1 and its balls will repel each other to a greater distance1 enlarging the triangles4 ,could the water1 supported by the seven balls1 come in contact1 it would form a drop or drops1 so heavy as to break the cohesion it had with the other balls1 and so fall4 ,let the two setts then represent two clouds1 the one a sea-cloud electrified1 and the other a land-cloud4 ,bring them within the sphere of attraction1 and they will instantly draw towards each other4 ,now you will see the separated clouds close thus--the first electrified ball that comes near an unelectrified one1 by attraction joins it1 and gives it fire2 instantly they separate1 and each flies to another of its own party1 one to give and the other to receive fire2 and so they proceed through both setts1 but so quick as to be in a manner instantaneous4 ,in the collision they shake off and drop their water1 which represents rain4 ,,chap4 ,,ii4 ,experiments with electric ,light4 ,these experiments should be made in a darkened room1 for though the electric light is visible frequently in day light1 yet the appearance of it is very often confused1 so that a distinct idea of it cannot be formed4 ,before we proceed to describe the experiments under this head1 it will be necessary to inform the reader that by the term vacuum which he will frequently meet with in this chapter1 we mean such an one as is formed by the action of an air pump1 which is a good conductor of electricity4 ,,experiments4 ,the ,aurora ,borealis4 ,take a phial nearly of the shape and size of a ,florence flask2 fix a stopcock or valve to its neck1 and exhaust it of air4--,if this phial be rubbed in the usual way to excite electrics1 it will appear luminous within1 being full of a flashing light1 very much resembling the northern lights or aurora borealis4 ,this phial may also be made luminous by presenting one end of it to the prime-conductor1 while the other is held in the hand4 ,in this case1 the whole cavity of the glass will instantly appear full of a flashing light1 which remains in it for some time after the glass has been removed from the prime-conductor4 ,a glass tube exhausted of air in the same manner1 and hermetically sealed1 may be used instead of this phial1 and perhaps with more advantage4 ,the most remarkable circumstance attending this experiment is1 that after the phial or tube has been removed from the prime-conductor1 and even several hours after the flashing light has ceased1 strong flashes will be again visible upon applying the hand4 ,the causes of this phenomenon are two2 first1 the conducting nature of the vacuum2 and second1 the charging of the glass2 for when one side of the phial is touched with the prime-conductor1 the electric fluid communicated to that part on the outside1 occasions the natural fluid of the inside surface1 to leave its place and pass to the opposite side of the phial1 which does not communicate with the electrified conductor2 this passing of the fluid through the vacuum occasions the light within1 which is more or less subdivided as the vacuum is more or less perfect4 ,that part of the phial which has touched the prime-conductor is actually charged1 for its outer surface has acquired an additional quantity of the electric fluid1 and the inside has lost part of its natural quantity2 but as the outside of the glass has no coating1 when it is removed from the prime-conductor and is not in contact with the hand or other conductor1 the charged part will be discharged gradually1 that is1 while its outside surface is communicating its redundant quantity to the contiguous air1 the inner surface acquires the electric fluid from the other parts of the phial or tube1 and this fluid passing through the vacuum1 causes the light which is observed for so long a time4 ,if the phial or tube be grasped with the hand1 the discharge will be accelerated1 yet it cannot be effected in this way immediately1 because the hand cannot touch every part of the glass at once4 ,the ,leyden ,vacuum4 ,take a small phial and coat it1 about three inches up the outside1 with tin-foil4 ,at the mouth of this phial cement a metallic cap1 having a hole with a valve2 and from this cap let a wire proceed a few inches within the phial1 terminating in a blunt point4 ,when this phial is exhausted of air1 a metallic ball must be screwed upon the cap1 so as to defend the valve1 and prevent the air from getting into the phial4 ,the reason why this phial requires no inside coating1 is1 because the electric fluid pervades a vacuum1 so that it can pass very easily from the wire to the surface of the exhausted glass1 without the assistance of a non-electric coating4 ,this phial exhibits very plainly the direction of the electric matter1 both in charging and discharging1 for if it be held by its bottom1 and the ball be presented to the prime-conductor1 positively electrified1 you will perceive that the pencil of rays 7which always appears when the body is positively electrified1 or is giving out the electric matter7 will proceed from the wire within the phial1 and when it is discharged1 the star1 7which always indicates that the body is negatively electrified1 or is receiving the electric fluid7 will be seen on the point instead of the pencil1 but if the phial be held by the ball1 and its bottom be presented to the prime-conductor1 the contrary will take place4 ,the luminous ,conductor4 ,this instrument1 as well as the preceding1 is an invention of ,mr4 ,henley's and also shows the direction of the electric fluid passing through it4 ,the description of it is as follows4 ,to each end of a glass tube1 about eight inches long and three or four inches in diameter1 is cemented a metallic cap1 so as to be perfectly air tight4 ,a point projects from one of the caps1 by which it is to receive the electricity from an excited cylinder1 and from the other proceeds a wire1 terminated by a ball1 from which sparks may be taken4 ,each cap is furnished on the inside with a knobbed wire1 which extends some distance into the tube4 ,a stopcock or valve must be adapted to one of the caps1 by which the tube may be exhausted of air4 ,the supporters of the instrument are two glass pillars1 fastened to a bottom board4 ,when the tube is exhausted of air1 and its pointed end placed near the excited cylinder of an electrical machine1 the point will appear illuminated with a star1 and a weak light will be seen pervading the whole tube2 but from the knobbed end of the wire1 within the tube1 a lucid pencil will issue1 and the opposite knob will be illuminated with a star or round body of light1 which1 as well as the pencil of rays from the other knob1 will be discernible among the other light which occupies the cavity of the tube4 ,if the point1 instead of being presented to the cylinder1 be connected with the rubber1 the appearance will be reversed--the reason is too obvious to mention4 ,if the wires within the tube be pointed1 the illumination will be the same2 but it seems not so strong in this as in the other case4 ,the electric ,light flashing between two metallic ,plates4 ,let two persons 7one standing upon an insulated stool communicating with the prime-conductor1 and the other upon the floor17 each hold in his hand a polished metallic plate1 in such a manner that their surfaces may be parallel1 and about two inches asunder4 ,upon turning the cylinder1 you will see the flashes of light between the two plates1 so dense and frequent1 that you can easily perceive any thing in the room4 ,by this experiment the electric light is exhibited in a very copious and beautiful manner1 and bears a strong resemblance to lightning4 ,the spiral ,tube4 ,this instrument is composed of two glass tubes1 one within the other1 and furnished with a metallic ball at each end4 ,the innermost tube has a spiral row of small round pieces of tin-foil1 stuck upon its outside surface1 and lying at the distance of one thirteenth of an inch apart4 ,now if the tube be held by one of its extremities1 while the other is presented to the prime-conductor1 every spark that is received from the conductor1 will cause small sparks to appear between all the round pieces of tin-foil upon the inner tube1 which in the dark appears encompassed by a spiral line of sparkling fire4 ,small pieces of tin-foil are sometimes stuck upon pieces of glass1 so as to represent various fanciful figures1 and upon the same principle is the luminous word produced4 ,to make an electric ,spark visible in ,water1 and to render various other ,substances luminous4 ,fill a glass tube1 about an inch in diameter and six inches long1 with water1 and to each extremity adapt a cork to confine the water2 through the corks let two blunt wires pass1 so as nearly to touch one another within the tube3 connect the outside coating of a small charged phial with one of these wires1 and touch the knob to the other1 which will cause a vivid spark to appear between their extremities within the tube4 ,it is necessary in this experiment that the charge of the phial should be exceedingly slight1 otherwise the tube would burst4 ,if you place in a common drinking glass almost full of water1 two knobbed wires1 so that their knobs may be within a little distance of one another in the water1 and make the charge of a large jar pass through the wires1 the explosion will disperse the water and break the glass with surprising violence4--,this experiment is very dangerous if not made with great caution4 ,water may be made luminous thus4 ,connect one end of a chain with the outside coating of a charged jar1 and let the other lie on the table2 place the end of another chain at about one fourth of an inch from the former2 then set a decanter of water on these separated ends1 and on making a discharge of the jar through the chains1 the water will appear beautifully luminous4 ,to render ivory or box wood luminous4--,place an ivory ball on the prime-conductor of the machine1 and take a spark or send the charge of a phial through its center1 the ball will appear perfectly luminous2 but if the charge be not taken through the center1 it will pass off the surface and corrode it4 ,a spark taken through a ball of box wood1 not only illuminates it1 but makes it appear of a beautiful crimson1 or rather scarlet colour4 ,an egg may also be illuminated in the same way4 ,but the most curious experiment to shew the electric light is made with the real1 or more easily with the artificial ,bolognian stone1 invented by the ingenious ,mr4 ,j4 ,canton4 ,this phosphorus is a calcareous substance 7generally used in the form of powder7 which has the property of absorbing light when exposed to it1 and afterwards appearing lucid in the dark4 ,to make the experiment1 take some of this powder1 and by means of spirits of wine or ether1 stick it all over the inside of a clear glass phial1 and stop it with a good cork and sealing wax4 ,if this phial be kept in a darkened room1 7which for this experiment must be very dark17 it will give out no light2 but let two or three strong sparks be drawn from the prime-conductor1 while the phial is kept about two inches distant from the sparks1 so that it may be exposed to their light1 and the phial will afterwards appear luminous for some time4 ,the powder may be stuck on a board by means of the white of an egg1 so as to represent figures of planets1 letters c4 at the operator's pleasure1 and these figures may be illuminated in the dark in the same manner as the phial1 for the method of making this phosphorus1 see appendix1 ,no4 #e4 ,,chap4 ,,iii4 ,experiments with ,charged ,electrics4 ,experiments with charged electrics should always be made with caution1 for though the discharge of a small phial through the body is seldom attended with bad consequences1 yet that of a battery is always dangerous1 and sometimes mortal4 ,the operator should therefore be attentive1 not only to the experiments he is about to perform1 but also to the persons who may happen to be with him1 forbidding them to come near any part of the apparatus4 ,,experiments4 ,the ,magic ,picture4 ,this experiment was contrived by ,mr4 ,kinnersley1 and is thus described by ,dr4 ,franklin4 ,having a large mezzotinto with a frame and glass1 7suppose of the king7 take out the print and cut out a pannel of it1 near two inches distant from the frame1 all round4 ,if the cut is through the picture it is not the worse4 ,with thin paste or gum water fix the border that is cut off on the inside of the glass1 pressing it smooth and close4 ,then fill up the vacancy1 by gilding the glass well with leaf gold or brass4 ,gild likewise the inner edge of the back of the frame all round1 except the top part4 ,make a communication between that gilding1 and the gilding behind the glass2 then put in the board1 and that side is finished4 ,turn up the glass and gild the foreside exactly over the back gilding1 and when it is dry paste on the pannel of the picture which has been cut out1 observing to bring the corresponding parts of the picture and border together1 by which it will appear of a piece1 as at first 7only part of it is behind the glass1 and part before it47 ,hold the picture horizontally by the top1 and place a little moveable gilt crown upon the king's head4 ,if now the picture be moderately electrified1 and another person take hold of the frame with one hand1 so that the fingers may touch the inside gilding1 and with the other hand endeavour to take off the crown1 he will receive a terrible blow4 ,if the picture were highly charged the consequences might be as fatal as those of high treason2 for when the spark is taken through a quire of paper1 and the discharge of the picture is made through it1 a fair hole will be perceived in every sheet1 7though a quire of paper1 is thought a good armour against the push of a sword1 or even against a pistol bullet17 and the crack exceedingly loud4 ,the operator who holds the picture by the upper end1 7where the inside of the picture is not gilt17 to prevent its falling1 feels nothing of the shock1 and may touch the face of the picture without danger1 which he pretends is a test of his loyalty4 ,if a ring of persons take the shock among them1 the experiment is called 8the conspirators40 ,colours changed by the ,electric shock4 ,mr4 ,cavallo accidentally observing that an electric spark1 passing over the surface of a card painted red1 marked it with a black stroke1 was induced to try what would be the effect of sending shocks over cards painted with different colours2 accordingly he painted several cards with different colours1 and passed the discharge of a jar1 containing about one foot of coated surface over them1 the result of his experiments are the following-- ,vermilion was marked with a strong black track1 about one tenth of an inch wide4 ,the streak was generally single1 but sometimes divided in the middle4 ,carmine received a faint and slender impression1 of a purple colour4 ,verdigris was shook off from the surface of the card1 except when it was mixed with a strong gum water1 in which case it received a very faint impression4 ,white lead was marked with a strong black track1 but not so broad as that on the vermilion4 ,on the red lead there appeared only a slight mark1 much like that on the carmine4 ,the other colours he tried were orpiment1 gambooge1 sap green1 red ink1 ,persian blue1 and some others which were compounds of the first1 but they received no impression4 ,it has frequently been observed that1 when a flash of lightning strikes the mast of a ship1 it passes over those parts of the mast1 which are covered with lampblack and tar1 or painted with lampblack and oil1 without the least injury2 when at the same time it shatters the uncoated part so as to render the mast entirely useless4--,this singular fact induced ,cavallo to carry his investigations on the subject still farther1 particularly with a view to determine something relative to the properties of lampblack and oil4 ,but it will not be necessary here to enumerate all his experiments upon this subject4 ,it is sufficient to state that the two following propositions are the result of his observations4 8,first--,that a coat of oil paint over any substance defends it from the effects of an electric shock1 that would otherwise injure it2 but that it would by no means defend it from any shock whatever4#ag 8,second--,one colour does not seem preferable to another1 if it is equal in substance and equally well mixed with oil--but that a thick coating affords a better defence than a thin one40 ,to fire ,spirit of wine4 ,hang to the prime-conductor a short metallic rod1 having a small ball at the end--then pour some spirit of wine1 a little warmed1 into a metallic spoon4 ,hold the spoon by the handle1 in such a manner that the knob of the rod may be about an inch above the surface of the spirit4--,in this situation1 if by turning the cylinder a spark be made to pass to the spoon through the spirit1 it will be set on fire4 ,it will generally be found more advantageous to fix a metallic dish1 containing the spirit1 upon the prime-conductor4 ,this experiment may be varied different ways1 so as to render it very agreeable to a company of spectators4 ,a person1 for instance1 standing upon an insulating stool1 connected with the prime-conductor1 may hold the spoon with the spirit1 in his hand--another person1 standing on the floor1 may fire the spirit by bringing his finger within a small distance of it--or1 instead of his finger he may use a piece of ice1 which will make the experiment still more surprising4 ,to swell ,clay1 and break small ,tubes4 ,roll up a piece of soft clay in a small cylinder1 and insert two wires1 so that their ends within the tube may be about one fifth of an inch apart4--,if a shock be sent through this clay1 by connecting the wires with the coatings of a pretty large jar which has previously been charged1 the clay will be inflated1 by swelling in the middle4--,if the clay be not very moist1 it will be broken by the explosion1 and the fragments thrown about the room4 ,to make this experiment with a little variation1 take a piece of the stem of a tobacco pipe1 or a glass tube 7which will answer equally well17 and fill the bore with moist clay2 then insert wires as in the preceding experiment1 and send the shock through it4 ,this tube will not fail to be broken1 and the pieces thrown to a considerable distance4 ,to pierce ,cards c4 with the electric ,explosion4 ,hold a card or the cover of a book1 close to the outside coating of a jar1 then by applying one end of the discharging rod to the card1 discharge the jar2 the electricity rushing through the circuit from the positive to the negative coating1 will pierce a hole through the card1 or book-cover4 ,this hole will be larger or smaller as the card is more or less moist4 ,the card1 upon examination1 will be found to have a sulphureous or rather phosphoreal smell4 ,it is remarkable in this experiment that there is a burr raised on both sides of the card4 ,insects may be killed in this manner4 ,if they are quite small the shock of a common phial will be found sufficient to deprive them of life3 but if they are large1 they will1 upon receiving the shock1 appear dead1 but after a short time recover4--,this however depends upon the quantity of the charge sent through them4 ,the shock of a jar1 sent through a lump of white sugar1 if strong enough to break it1 will illuminate every part of the sugar1 and this illumination will continue a short time after making the experiment4 ,to light a ,candle by the discharge of a ,jar4 ,take a wire about the size of a common knitting needle1 and by means of a small flexible chain1 let one end communicate with the outside coating of a jar1 containing at least ten inches of coated surface4 ,to the other end of the wire some cotton must be twisted very loosely1 so as to cover the extremity of the wire completely4 ,the cotton must be rolled or sprinkled with powdered rosin4 ,now let the jar be charged and bring the cotton to its knob pretty quickly1 so that the discharge may pass through the rosin on it2 the cotton will instantly inflame1 and will last long enough to light a candle4 ,paper1 dipped in a solution of nitre and water1 and previously dried1 may be fired in the same manner1 and by this a brimstone match may be lighted4 ,the same effect will follow1 if you grease the cotton with a little sweet-oil1 or moisten it with turpentine4--,flame may be again excited in a candle recently blown out1 by simply passing the discharge of a jar through the wick and smoke4 ,,chap4 ,,iv4 ,experiments relating to the influence of pointed ,bodies on ,electricity4 ,these experiments1 though not the most entertaining are certainly among the most important in electricity4 ,by the knowledge of them1 mankind have received the greatest practical advantage4 ,but as we have already treated of this subject1 we shall1 in this chapter1 describe only two experiments which may serve to set it in a clearer light1 and which may1 in a more particular manner1 demonstrate the utility of affixing pointed conductors to buildings1 in order to preserve them from the dreadful effects of lightning4 ,,experiments4 ,the electrified ,cotton4 ,take a small lock of cotton1 extended in every direction as much as can conveniently be done1 and by a linen thread about five or six inches long1 fasten it to the prime-conductor2 then let the cylinder of the machine be turned--the lock of cotton1 by the repellency of its filaments1 will immediately swell and stretch itself towards the nearest uninsulated conductor4 ,in this situation1 if you present your knuckle or a knobbed wire towards the cotton1 it will immediately move towards it1 and endeavour to touch it2 now with the other hand present a pointed wire to it3--the cotton will immediately shrink up1 and fly towards the prime-conductor4 ,remove the point1 and the cotton will again approach the knuckle or knobbed wire--present the point1 and it will again recede4 ,this experiment shows that a point is the proper termination for a lightning rod4 ,for the cotton will represent the cloud1 and the two wires1 the lightning rods with different terminations4 ,the cotton is attracted by the knuckle or knobbed wire1 in order to part with its electricity1 this however cannot be effected unless they come so near as to touch one another1 and then the discharge is effected at once4 ,but the point is capable of drawing off the electricity when at a distance1 and it does this gradually2 at the same time that it causes a current of air which repels the cotton2 the cotton being deprived of its electricity is again attracted by the prime-conductor4 ,the electrified ,bladder4 ,coat a bladder that is well blown1 with gold1 silver1 or brass leaf1 which may be fastened on with gum water4--,suspend this bladder at the end of a silk thread1 six or seven feet long1 from the ceiling of the room4 ,electrify the bladder by giving it a few sparks from a charged jar1 and hold towards it1 at some distance1 a knobbed wire2 you will perceive that the bladder approaches the knob1 and when it comes within striking distance1 gives it the electricity it received from the charged jar1 and thus becomes discharged4 ,touch it again with the charged phial1 and instead of the knobbed wire1 present the point of a needle towards it1 the bladder will now be rather repelled than attracted1 especially if the point be very suddenly presented to it4 ,,chap4 ,v4 ,promiscuous ,experiments4 ,we shall in this chapter1 describe a variety of experiments1 which are easily made1 and which may serve to illustrate the principles of electricity in general4 ,,experiments4 ,the electrical ,jack4 ,this is an invention of ,dr4 ,franklin1 and turns with considerable force1 so that it may sometimes be used for the purposes of a common jack4 ,the construction of it is as follows4--,a slender shaft of wood passes1 at right angles1 through the centre of a thin1 round board1 about twelve inches in diameter1 and turns upon a sharp point of iron1 fixed in the lower end2 while a strong wire in the upper end passes through a hole in a brass plate1 which keeps the shaft truly vertical4 ,about thirty radii1 of equal length1 made of sash glass1 cut into narrow slips1 issue horizontally from the circumference of the round board1 the ends farthest from the centre1 being about four inches apart1 and each furnished with a metallic ball or thimble4 ,if the wire of a jar1 electrified in the common way1 be brought near the circumference of the wheel1 it will attract the nearest ball or thimble1 and put the wheel in motion4 ,that ball or thimble1 passing by the knob of the jar1 receives a spark from it1 and being thereby electrified1 is repelled1 and driven forward2 while the second1 being attracted1 approaches the knob1 receives a spark from it1 and is driven after the first4 ,this process is repeated till the wheel has made one revolution2 when the thimbles1 before electrified1 approaching the wire1 instead of being attracted are repelled1 and the motion presently ceases4--,but if another jar1 charged through the coating1 or otherwise electrified negatively1 be placed near the same wheel1 its wire will attract the thimble or ball1 repelled by the first jar1 and thereby double the force which carries round the wheel4 ,the self-charging ,tube4 ,take a glass tube1 about eighteen inches long1 and an inch1 or an inch and a half1 in diameter2 coat the inside with tin-foil1 from one extremity of it as far as the middle2 then fix a cork to the aperture of the coated end1 and let a knobbed wire pass through it1 and come in contact with the coating4 ,the instrument being thus prepared1 hold it in one hand by the uncoated part1 and with the hand clean and dry1 or with a piece of buckskin1 which has had some amalgam spread upon it1 rub the outside of the coated part2 after every two or three strokes1 you must remove the rubbing hand1 and by applying it to the knobbed wire1 you will receive sparks from it4 ,by this means the coated end will gradually acquire a charge1 which may be increased to a considerable degree4 ,now1 if you grasp the outside of the coated end with one hand1 and touch the knobbed wire with the other1 you will receive a shock4 ,in this experiment1 the coated part of the tube answers the double purpose of the electrical machine and ,leyden phial2 the uncoated part serving as a handle1 to hold the instrument by4 ,the friction on the outside accumulates a quantity of positive electricity upon it1 and this electricity1 in virtue of its sphere of action1 forces out a quantity from the inside4 ,then1 by taking the sparks from the knobbed wire1 this inside electricity is removed1 and it consequently remains under-charged1 or negatively electrified2 and it also follows1 that the positive electricity of the outside1 comes closer to the surface of the glass1 and begins to form the charge4 ,a small phial may be charged by giving the sparks from the knobbed wire of the tube to that of the phial2 but the phial will be charged negatively1 whereas the tube is charged positively4 ,to fire the electrical ,cannon by inflammable ,air4 ,this instrument consists of a metallic barrel1 made in the shape of a common cannon1--a glass tube is cemented into the top of the barrel1 in the place of a touch-hole1 and through this tube a wire passes1 which is bent so as to come within an eighth of an inch of the inner surface of the cannon1--on the outer end of this wire1 a ball is fixed1 which serves to receive a spark from a charged jar1 or from the prime-conductor4 ,the inflammable air with which this cannon is to be fired1 may be prepared in a common porter bottle1 by mixing a handful of iron filings with two wine-glassfuls of water1 and an ounce of sulphuric acid1 commonly called oil of vitriol4 ,the air when thus made should be kept in a bottle closely stopped4 ,to use the instrument1 have ready a cork1 fitted to the mouth of the cannon1--uncork the bottle containing the air1 and immediately apply the cannon to the mouth of the bottle2 a sufficient quantity of the gas will rise into the cannon1 in the course of a few seconds1 when both the cannon and bottle must be corked4 ,now1 if the knob of the wire passing through the tube be applied to the prime-conductor1 so that a spark may pass through it to the inner surface of the cannon1 the gas will be inflamed with a loud report1 and the cork will be forced out with considerable violence4 ,curious ,figures made upon ,glass1 ,paper1 and other ,substances1 by means of ,electricity4 ,professor ,lichtenburg first observed some curious figures made with pulverized rosin1 on a large electrophorus2 but since this original discovery1 a variety of other methods have been contrived1 for making them upon glass1 paper1 resinous substances and many others4 ,the ingenious electrician may derive considerable information from these figures2 their various appearances1 in many instances1 showing him the direction and quality of the electric fluid4 ,the principal method of making these impressions is to electrify a perfect or imperfect electric1 and then to throw certain powders upon the electrified substance1 which will be arranged in different forms4 ,the most convenient method of projecting these powders is to put them into a small bottle of ,india-rubber1 and then fasten a tube of glass or metal to the neck of the bottle2 the orifice of this tube must be covered with a piece of flannel when used4 ,as to the nature of the powders1 almost every substance which can be pulverized will do4--,thus chalk1 rosin1 sulphur1 rose-pink1 dragon's blood1 gum-arabic1 lake1 and evaporated decoctions of colouring woods1 may be used with advantage1 either singly or mixed4 ,take a clean pane of glass1 fourteen or fifteen inches square1 and after drying it thoroughly1 hold it by one corner1 and pass over its surface the knob of a jar1 moderately charged with positive electricity--then1 keeping it suspended1 project upon it1 by means of the bottle above described1 a mixed powder of dragon's blood and gum-arabic1 in equal parts4 ,if you examine the glass1 you will find that the two powders will be separated upon it1 the red powder of dragon's blood falling on certain places1 and the white powder of gum-arabic falling upon certain other places1 so as to form a track upon the parts which were touched with the charged jar1 consisting of two colours disposed in a thousand different ways4 ,if1 instead of drawing the knob of the jar over the surface of the glass1 you only touch it here and there with it1 and then throw on the mixed powders as before1 separate star-shaped figures will be formed about these places4 ,the stars will be better defined when a single powder is used2 their rays are sometimes few and strong2 at others1 many and slight1 and frequently they do not go entirely round the parts which have been touched by the phial4 ,these different effects depend chiefly upon the quantity of the charge in the jar4 ,if the jar be charged negatively1 the appearances will be very different1 from those occasioned by positive electricity4 ,very few rays will now be observed1 the powders for the most part disposing themselves in round figures1 and generally a central spot of one powder will be surrounded by another of a different colour4 ,some powders adhere but slightly to the glass1 so as not to bear being touched2 but if a piece of paper be laid upon the painted side1 without disturbing the figures1 and the edge of it be fastened all round to the edge of the glass1 the figure may be preserved without injury4 ,but a better method is to lay another pane of glass over the one with the figures upon it1 and then to fasten them together with sealing-wax1 or a piece of paper pasted over the edges4 ,if the powders of such colours as are used for enamel-painting be projected upon glass or porcelain1 and these substances be afterwards exposed to a proper degree of heat1 as that of an enameller's furnace1 the figures will be rendered indelible4 ,take a piece of common writing paper1 and hold it near the fire1 so as to make it quite dry and very hot--lay it upon a dry table and pass the knob of a charged jar over it--then take up the paper by one corner1 and holding it suspended1 throw upon it a mixed powder of dragon's blood and gum-arabic1 in the way above mentioned4--,the figures in this instance will be very beautiful1 and may be made in various shapes1 as letters1 stars1 or stripes4 ,if the paper thus painted be held near the fire for a few seconds1 the powder of dragon's blood1 being a resinous substance1 will be melted and fastened to the paper1 after which the gum-arabic may be taken off4 ,powders of different colours may be projected upon the paper after the same manner1 but unless they be of a resinous nature1 so as to be easily melted by heat1 it is very difficult to fasten them to the paper4 ,a little experience will enable the operator to make them in a neat and handsome manner4 ,it will however be necessary to observe a few precautions4--,the charge of the jar should not be too great or too small2 for in the former case the figures will be confused and irregular2 and in the latter they will be too faint4--,these experiments should be performed as quickly as possible1 for if the paper be suffered to cool too much1 or the communicated electricity be dissipated1 the desired effect will not be produced4 ,the ,electrified ,capillary ,syphon4 ,let a small bucket of metal be suspended from the prime-conductor1 and put into it a syphon of glass or metal1 so narrow at the outer extremity that the water may just drop from it4--,now1 if the cylinder be turned1 the water1 which when not electrified came over only in drops1 will run in a stream1 or even be subdivided into a number of smaller ones4--,if the experiment be made in the dark1 the streams appear luminous4 ,the same phenomenon may be exhibited by a small bucket1 with a jet pipe fixed in the bottom4 ,this must be hung on the prime-conductor1 as in the last experiment3 or the experiment may be agreeably varied1 by hanging one bucket from a positively1 and another from a negatively electrified conductor3 so that the two jets may be about three inches from each other4--,the stream issuing from the one will be attracted by that issuing from the other1 and both will unite into one3 but1 though both are luminous in the dark1 before meeting1 after this has taken place they will not be so1 unless one of them was more powerfully electrified than the other4 ,the ,lateral ,explosion4 ,if a jar be discharged with a rod which has no electric handle1 the hand which holds the rod1 on making the discharge1 frequently feels something similar to a shock1 especially when the charge is considerable4--,this shock1 or lateral explosion1 as it has been called1 may be rendered visible in the following manner4--,connect a chain with the outside coating of a charged jar--then discharge the jar through another circuit2 for instance1 a discharging rod--,the chain which is connected with the outside coating1 but which forms no part of the circuit1 will appear lucid in the dark2 that is1 sparks will be seen at every link4 ,this chain will also appear lucid1 if it be only put close to the jar1 without touching it2 and on making the discharge a spark will be seen between the coating and the end of the chain4 ,this luminous appearance is what has been denominated the ,lateral explosion4 ,to represent the ,constellations4 ,provide yourself with a piece of paste-board1 of the size you intend the figure of the constellation1 7four or five inches square will be found convenient7 and cover one side with tin-foil or silvered paper4 ,let needles1 or any other small metallic points1 project from the other side of the paste-board1 from the places where you intend stars to appear1 taking care to form a communication between each of the points1 or needles1 and the tin-foil on the other side4 ,if the instrument thus prepared be fixed upon the prime-conductor1 negatively electrified1 all the points will be illuminated at once4--,the experiment may be performed with the prime-conductor positively electrified2 but in this case1 the light at the points1 being in the shape of a divergent cone1 does not appear so proper to represent stars1 as the round globular lights1 which are characteristic of points negatively electrified4--,it is scarcely necessary to remark that this experiment should be performed in a darkened room4 ,the ,electrical ,snake4 ,cut a circular piece of silvered paper into a spiral form4 ,the outer end must be shaped like a serpent's head1 with the mouth open and the tongue protruded4 ,then provide an upright shaft of wood or metal1 terminating upward in a point1 and having the lower extremity fastened in a foot or bottom-board4 ,the snake1 being put spirally round the shaft1 with its tail on the point1 and then placed under a metallic point suspended from the prime-conductor1 will turn round1 and in a darkened room will appear to spit fire4 ,the luminous ,shower4 ,electrify a common tumbler1 by passing a chain1 communicating with the prime-conductor1 over its inner surface4 ,place a small heap of steel or brass-filings on an uninsulated conductor1 and invert the electrified tumbler over it3 the filings will be attracted up the sides of the tumbler1 and then thrown off4 ,this1 at night1 forms a very beautiful experiment1 as the filings become luminous1 and appear like a shower of fire4 ,if a tumbler1 electrified in this way1 be inverted over pith balls1 instead of brass-filings1 the balls will leap with surprising velocity up the sides of it4 ,the luminous ,discharging-rod4 ,provide a glass tube in the shape of a common discharging-rod1 about ten inches in length1 and let the bore of the tube be nearly the eighth of an inch in diameter2 upon one end fasten with cement1 or otherwise1 a brass knob1 so as to be perfectly air tight4 ,now expel the air from the tube1 by heat or the air pump1 and then fix another knob upon the open end1 in a way similar to the former4 ,if the instrument be used as the common discharging-rod1 it will be found to answer its purposes equally well2 while at the same time all the inner surface of the tube1 during the discharge of a jar with it1 is beautifully luminous4 ,mr4 ,nairne also contrived a luminous discharging-rod4 ,it consisted of an arched glass tube1 with a metallic ball at each end1 and a communication from one ball to the other was made by a brass chain1 which passed through the bore of the tube4--,in the discharge of a jar with it1 small sparks are seen between the links of the chain within the tube4--,both these dischargers should have handles fastened to them4 ,to decompose ,water by ,electricity4 ,let a glass tube1 having a small bore1 be filled with water2 then close each end of the tube with a piece of cork1 and let two wires pass through the corks1 so that their extremities may come pretty near each other within the tube4 ,if sparks of electricity be made to pass between the ends of the wires1 within the tube1 the water will be converted into oxygen and hydrogen gases4 ,if this process be continued till the extremities of the wires become immersed in the two gases1 they will explode and again form water4 ,the ,electrified ,fountain4 ,insulate a small fountain made of metal1 7one on the construction of ,hiero's will be found most convenient17 and connect it with the prime-conductor--put it in operation--the jet will be undivided1 except at the top--now turn the cylinder1 and you will immediately perceive the jet divided much lower than at first2 the drops1 which before fell nearly perpendicularly1 will now be thrown off in elliptical lines1 and attracted by any conductor brought near them4 ,a small ,leyden phial may be charged at the top of the jet1 which will present the curious spectacle of fire coming out of water4 ,,epitome ,,of ,,electricity4 ,,division ,,iii4 ,,chap4 ,i4 ,introductory ,observations to the theory of ,electricity4 ,there is scarcely any thing to which an inquisitive mind1 such as a philosopher possesses1 submits with more reluctance1 than to the inability of assigning the causes of the most interesting appearances or phenomena of nature4 ,that every effect has a cause1 is a first or self evident principle1 and the mind is not easily brought to acquiesce in its utter ignorance of the cause1 when the effect is visible and striking4--,from this circumstance proceeded the numerous wild1 fanciful1 and delusive systems of natural philosophy1 which existed before the time of the great ,lord ,bacon4--,his penetrating and discriminating mind saw that nothing solid could ever be achieved in that noble science1 unless such a procedure were relinquished2--unless men would consent to confess their ignorance of causes which were actually unknown2--unless they would cease to rely on hypotheses1 however plausible1 until they were verified by experiment2--consent to take facts as they are found1 and by experiments alone endeavour to ascend to their causes4 ,on this immoveable base the ,newtonian philosophy is founded1 and it will of course prove as durable as nature herself4 ,two things1 however1 in regard to this subject1 are of some importance to be remarked4--,the first is1 that experiments may sometimes be supposed to ascertain causes which will afterwards be found not to exist1 or to be wrongly assigned2 because the experiments had not been accurately or extensively made4 ,the second remark is1 that though hypotheses are not to be taken for philosophy1 till they have stood the test of experiment2 yet in the process of the mind in making discoveries1 hypothesis is perhaps always used1 where the discovery is not merely accidental4 ,no man can rationally make experiments till he has conceived a notion1 supposition1 or hypothesis in his mind1 which he imagines experiment may serve to verify4--,it is this which prompts him to his researches and guides him in conducting them4 ,in regard to electricity1 it is remarked by ,dr4 ,priestley1 that 8no other part of the whole compass of philosophy affords so fine a scene for ingenious speculation4 ,here the imagination may have full play1 in conceiving of the manner in which an invisible agent produces an almost infinite variety of visible effects4 ,as the agent is invisible every philosopher is at liberty to make it whatever he pleases1 and ascribe to it such properties and powers as are convenient for his purpose4 ,and1 indeed1 if he can frame his theory so as really to suit all the facts1 it has all the evidence of truth1 that the nature of things can admit40 ,for ourselves we are by no means satisfied that there is yet any theory of electricity which will 8suit all the facts20 and therefore if this be requisite to entitle a theory philosophy1 as contra-distinguished from hypothesis1 we must think that the best theory of electricity is yet hypothesis1 and not philosophy4 ,we believe that the ,franklinian theory accounts for more facts1 and is far more plausible1 than any other4 ,but1 as we have already had occasion to remark in a former chapter1 it does not appear to us fully and satisfactorily to account for all the phenomena of electric attraction and repulsion4 ,dr4 ,franklin always spoke with great diffidence of his own theory1 and always denominated it an hypothesis4 8,every appearance1 says he1 which ,i have seen1 in which glass and electricity are concerned1 are1 ,i think explained with ease by this hypothesis4 ,yet1 perhaps1 it may not be a true one1 and ,i shall be obliged to him who affords me a better40 ,in like manner pinus1 who adopted the theory of ,franklin1 and who has illustrated its leading principles in a far more masterly and scientific manner than any other writer1 still denominates the theory which he maintains an hypothesis4 ,why should pupils affect to go farther than their masters8 ,we think that the theory of electricity is still an hypothesis4 ,we are however clearly of opinion that the hypothesis of ,franklin is preferable to every other4 ,we have therefore adopted it in the whole of our system1 and mean to close this division of our subject by giving it1 somewhat in detail1 with the leading facts and considerations by which its claim to superiority appears to us to be supported4 ,in the mean time1 as every student of electricity may wish to know1 and ought to know1 what other theories have been adopted1 we shall fill the following chapter with a brief and compendious recital of some of the principal of them4--,it would be endless to recite them all4 ,we shall1 however1 enter into no extensive argument to prove their fallacy1 as this would be inconsistent with our plan1 as well as unprofitable in itself4 ,we shall afterwards say what we can to confirm the theory of ,franklin1 and if we succeed1 every thing opposed to it1 must1 of course1 appear to be unsupported4 ,,chap4 ,,ii4 ,theories of ,electricity1 exclusive of that of ,franklin4 ,the first electricians supposed that the attraction of electric substances1 was caused by certain unctuous effluvia1 emitted from these substances when they were excited4 ,such effluvia were supposed to fasten upon all bodies which fell in their way1 and if not too heavy1 to carry them back to the emitting substances4 ,for at that time1 all effluvia were supposed to return to the bodies whence they had been emitted2 because they could not otherwise account for the fact1 that such substances were not sensibly wasted by emitting effluvia4 ,but when the subtilty of light was demonstrated by ,newton1 and that of the effluvia of many bodies was better understood1 philosophers gave up the doctrine of the return of effluvia1 both with regard to electricity and other subjects4 #b4 ,they applied to electricity the general1 but unknown principles of attraction and repulsion--properties which they supposed to be immediately communicated by the ,creator to certain bodies4 ,but the laws of this attraction and repulsion1 in regard to electricity1 we do not know that they attempted to explain4 #c4 ,mr4 ,du ,faye discovered the two opposite species of electricity1 which he termed the vitreous and the resinous1 because one was found in glass and the other in rosin1 sealing-wax1 c4 ,he immediately adopted the theory of two distinct electric fluids1 repulsive with respect to themselves1 and attractive of one another4 ,but he did not know at this time1 that both these species were concerned in every electrical operation1 and that glass or rosin alone always produces both of them4 ,when he found that electric appearances took place at an insulated rubber1 and it was demonstrated that the action of the rubber did not produce1 but only collect the electric fluid1 he perceived that both electricities1 as they had heretofore been called1 were produced at the same time1 by one and the same electric2 and with a candour that does him honour1 he gave up his theory1 and embraced that of ,franklin1 which was first suggested about this time4 #d4 ,with some1 and particularly ,mr4 ,wilson1 the chief agent in all electrical operations is ,sir ,isaac ,newton's ether2 which is supposed to be more or less dense in all bodies1 in proportion to the smallness of their pores1 except that it is much denser in sulphureous and unctuous bodies4 ,to this ether are ascribed the principal phenomena of attraction and repulsion4 8,on this theory1 7says ,dr4 ,priestley7 ,i shall make no particular remarks1 because ,i cannot say that ,i clearly comprehend it40 #e4 ,the ingenious ,abb ,nollet1 whose theory has been more the subject of debate than all the others1 before ,dr4 ,franklin's1 supposes that in all electrical operations the fluid1 7of which he admits there is but one7 is thrown into two opposite motions2 that the affluence of this matter drives all light bodies before it1 by impulse1 upon the electrified body2 and that its effluence carries them back again4 ,but he seems very much embarrassed in accounting for facts where both these currents must be considered as taking place at the same time1 and in finding out expedients to prevent their impeding and interrupting the effects of each other4 ,to obviate this great difficulty1 he supposes that every excited electric1 and likewise every body to which electricity is communicated1 has two orders or kinds of pores1 one for the emission of the effluvia1 and the other for the reception of them4 ,the ,abb maintained this hypothesis with a zeal and ingenuity worthy of a better cause4 ,for it is manifest at once1 that the existence of such kinds of different pores in bodies1 is a mere gratuitous assumption4 ,our senses do not inform us of the existence of any such pores1 nor have we evidence of any kind that they even exist at all1 unless we consider it as evidence of their existence1 that they are necessary to account for the appearances on which the ,abb grounds his theory4 ,yet this theory1 with some modification1 has been strenuously maintained1 and has its advocates to the present day4 ,they say that 8in bodies positively electrified1 there is a flux of electric matter1 from their surface all round2 that is1 the fluid contained in their pores pushes out on every side1 and communicates a similar motion to the electric fluid contained in the adjacent atmosphere4 ,this must of necessity very soon exhaust the body of its electric matter altogether1 if it was not instantaneously supplied after every emission4 ,but this supply is immediately procured from the surrounding atmosphere4 ,the quantity sent off is instantaneously returned from the air1 and a vibratory motion or struggle between the air and electric fluid1 immediately takes place4 ,the positive electricity therefore consists in a vibratory motion in the air and electric fluid2 and the force of the vibration is directed outwards from the electrified body4 ,in bodies negatively electrified1 the fluid contained in the neighbouring atmosphere is directed towards the body so electrified4 ,but it is certain1 that this motion inwards cannot be continued unless there is also a motion of the fluid outwards from the body4 ,in this case also1 there is a vibratory motion1 but the force of it is directed inwards1 and as the source of it lies not in the body1 but in the surrounding atmosphere1 it manifests itself somewhat less vigorously40 ,we have taken this account of the modification of the ,abb ,nollet's theory from one who firmly believed it4 ,but we cannot pretend to controvert it1 because1 7as ,dr4 ,priestley says17 8we cannot say that we clearly comprehend it40 #f4 ,there are some who explain the phenomena of electricity upon chemical principles4 ,they also believe in the existence of two distinct and positive fluids2 but instead of a mechanical operation1 they consider all their sensible effects as arising from chemical affinity and union4 ,the following may serve as a specimen of chemical electricity4 ,it is said-- 7#a47 8,there are two kinds of electric ether1 which exist either separately or in combination4 ,that which is accumulated on the surface of smooth glass1 when rubbed with a cushion1 is here termed vitreous ether2 and that which is accumulated on the surface of resin1 or sealing-wax1 when rubbed in like manner1 is here termed resinous ether2 and a combination of them1 as in their usual state1 may be termed neutral electric ethers4 7#b47 ,atmospheres of vitreous1 or of resinous1 or of neutral electricity1 surround all separate bodies1 are attracted by them and permeate those which are called conductors1 as metallic1 aqueous1 and carbonic substances2 but will not permeate those which are called non-conductors1 as air1 glass1 silk1 resin1 sulphur4 7#c47 ,the particles of vitreous ether1 strongly repel each other1 but attract the particles of resinous ether and vice versa4 ,when the two electric ethers unite1 a chemical explosion occurs1 in some respects like that of gun-powder1 light and heat are liberated1 and rend or fuse the bodies which they occupy4 7#d47 ,glass holds within it1 in combination1 much resinous electric ether1 which constitutes a part of it1 and which more forcibly attracts vitreous electric ether1 from surrounding bodies which stand on it1 mixed with a less proportion of resinous ether1 like an atmosphere1 but cannot unite with the resinous ether1 which is combined with the glass4 ,and resin1 on the contrary1 holds within it1 in combination1 much vitreous electric ether1 which constitutes a part of it1 and which more forcibly attracts resinous electric ether from surrounding bodies1 which stand on it1 mixed with a less proportion of vitreous ether1 like an atmosphere1 but cannot unite with the vitreous ether which is combined with the resin4 7#e47 ,hence the non-conductors of electricity are of two kinds1 and opposite to each other2 the one class of the vitreous1 and the other of the resinous4 ,but the most perfect conductor1 such as metal1 water and charcoal1 having neither kind of electric ether1 combined with them1 though surrounded with both1 suffer both kinds to pass through them easily4 7#f47 ,great accumulation or condensation of the separate electric ethers1 attract each other so strongly that they will break a passage through non-conducting bodies4 ,hence trees and stone walls are rent by lightning4 7#g47 ,when artificial or natural accumulations of these separate ethers are in a very small quantity or intensity1 they pass slowly and with difficulty from one body to another1 and require the best conductors for this purpose4 ,whence many of the phenomena of the ,torpedo1 the ,gymnotus1 and of ,galvanism4 7#h47 ,the electric ethers may be separately accumulated1 by the contact of conductors with non-conductors--by vicinity of the two ethers--by heat--and by decomposition4 7#i47 ,when these two ethers unite suddenly and with explosion1 a liberation of light and heat takes place1 as in all chemical explosions4 ,accordingly it is said that a smell is perceptible from electric sparks1 and even a taste1 which must be supposed to arise from new combinations or decompositions40 ,the theory founded on the principles above stated is supposed1 by those who adopt it1 to solve many difficulties which can scarcely be accounted for on the theory of ,franklin4 ,dr4 ,gibbes also adopts a chemical theory of electricity4 ,he supposes that oxygen gas is produced by the union of positive electricity with water2 and hydrogen gas by the union of negative electricity with water3 and that water1 uniting in different proportions with the two electricities1 is the ponderable part of all the elastic fluids4 ,he asserts that by the positive electricity metals are oxydated1 and blue vegetable colours reddened2 and also that the acidifying effect of electric commotions in the atmosphere1 on weak fermented liquors1 is unquestionable4--,on the other hand1 according to this writer1 by negative electricity the vegetable blue is restored1 and the oxydated metal revived4 ,these circumstances1 among others1 led ,dr4 ,gibbes to conclude that when hydrogen gas is produced by the affusion of water on red-hot metal1 and the metal is at the same time oxydated1 a decomposition of fire rather than of water has taken place2 that the hot metal has parted with negative electricity1 which1 uniting with a small proportion of the water1 has formed hydrogen gas2 that a greater proportion of the water has united with the positive electricity1 and entered1 as oxygen gas1 into combination with the metal4 ,when the two gases are inflamed together1 the spark attracts to itself1 in due proportions1 the two electricities contained in the two gases1 which unite with explosion1 and produce fire4 ,the water with which they were before combined is of course deposited4 ,the reason why inflammable substances burn in oxygen gas1 and not in hydrogen1 ,dr4 ,gibbes supposes to be1 that negative electricity greatly prevails in all inflammable substances4 ,neither of the gases can be inflamed separately1 because fire depends on the union of the two electricities2 and such union cannot be effected unless both are present in due proportion4 ,dr4 ,gibbes supposes that the further illustration of the effects of the two electricities1 as chemical agents1 will set aside some of the leading doctrines of the ,lavoisierian theory1 and afford an easy solution of certain phenomena which that theory cannot explain4 pinus' ,theory of ,electricity4 ,mr4 pinus1 of the imperial academy of ,petersburgh1 has attempted to class the phenomena of electricity and magnetism in a mathematical method4 ,in the course of his works he gives some views of the subject which are new and highly ingenious1 and as some good judges suppose1 calculated to surmount many difficulties1 and to answer many questions1 which occur in considering the ,franklinian theory4 ,the leading principles of his plan are comprehended in the following propositions4 #a4 ,its particles repel each other1 with a force decreasing as the squares of the distances increase4 #b4 ,its particles attract the particles of some ingredients in all other bodies1 with a force decreasing according to the same law1 with an increase of distance2 and that this attraction is mutual4 #c4 ,the electric fluid is dispersed in the pores of other bodies1 and moves with various degrees of facility through the pores of different kinds of matter4 ,in those bodies which we call non-electrics1 such as water or metals1 it moves without any perceivable obstruction2 but in glass1 resin1 and all bodies called electrics1 it moves with very great difficulty1 or is altogether immoveable4 #d4 ,the phenomena of electricity are of two kinds3 #a4 ,such as arise from the actual motion of the fluid1 from a body containing more1 to one containing less of it4 #b4 ,such as do not immediately arise from this transference1 but are instances of its attraction and repulsion4-- ,these principles are applied at great length1 and with a pleasing degree of precision1 by the ingenious theorist1 to the ,leyden phial1 and to the various phenomena of electric attraction and repulsion4 ,it will be readily seen that pinus adopts1 in substance1 the theory of ,franklin1 of which1 in some particulars1 he presents new and more satisfactory views than the ,american philosopher4 ,in the sixty first volume of the ,philosophical ,transactions1 there is a dissertation by the ,hon4 ,mr4 ,cavendish on this subject1 which he considers as an extension and more accurate application of pinus's theory4 ,,chap4 ,,iii4 ,the ,franklinian ,theory of ,electricity4 ,we are now to give ,dr4 ,franklin's theory of plus and minus1 or positive and negative electricity1 and adduce facts1 to shew how far this theory will go to explain the different phenomena4 ,the ,doctor supposed that all the operations in electricity1 depended upon one fluid1 sui generis1 extremely subtile and elastic4--,that there subsists a very strong repulsion between the particles of this fluid1 in regard to one another1 and as strong an attraction1 with regard to other matter4--,thus one quantity of electric matter will repel another quantity of the same1 but will attract1 and be attracted by1 any terrestrial matter that happens to be near it4 ,the pores of all bodies are supposed to be full of this subtile fluid2 and when its equilibrium is not disturbed1 that is1 when there is neither more nor less of it in a body than its natural share1 or than it is capable of retaining by its own attraction1 the fluid does not manifest itself to our senses4 ,the action of the rubber upon an electric disturbs this equilibrium1 occasioning a redundancy of the fluid in one place1 and a deficiency of it in another4 ,this equilibrium being forcibly disturbed1 the mutual repulsion of the particles of the fluid is necessarily exerted to restore it4 ,if two bodies be both of them over-charged1 the electric atmospheres repel one another1 and both the bodies recede from each other1 to places where the fluid is less dense4--,for as there is supposed to be a mutual attraction between all bodies and the electric matter1 such bodies as are electrified must go along with their atmospheres4 ,if both bodies are exhausted of their natural share of this fluid1 they are both attracted by the denser fluid1 existing either in the atmosphere contiguous to them1 or in other neighbouring bodies2 which occasions them still to recede from one another1 as if they were over-charged4 ,dr4 ,franklin's theory has gained the greatest reputation1 from the easy solution it affords of all the phenomena of the ,leyden phial4 ,the fluid is supposed to move with the greatest ease in bodies which are conductors2 but with extreme difficulty in electrics per se2 in so much that glass is absolutely impermeable to it4 ,it is also supposed that all electrics1 and particularly glass1 on account of the smallness of their pores1 do at all times contain an exceedingly great1 and always an equal quantity of this fluid2 so that no more can be thrown into any one part of any electric substance1 except the same quantity go out at another1 and the gain be exactly equal to the loss4 ,these things being premised1 the phenomena of charging and discharging a plate of glass1 or a ,leyden phial1 may be easily solved4 ,in the usual manner of electrifying by a smooth glass globe or cylinder1 all the electric matter is supplied by the rubber1 from all the bodies which communicate with it4 ,if it be made to communicate with nothing but one of the coatings of a glass plate1 while the prime-conductor is connected with the other1 that side of the glass which communicates with the rubber1 must necessarily be exhausted in order to supply the conductor1 which must convey the whole of it to the coating with which it is connected4 ,by this operation1 therefore1 the electric fluid becomes almost entirely exhausted from one side of the plate1 while it is as much accumulated on the other2 and the discharge is made by the electric fluid rushing1 as soon as an opportunity is given it by means of proper conductors1 from the side which was overloaded to that which was exhausted4 ,it is not however necessary to this theory1 that the same individual particles of electric matter which were thrown upon one side of the plate1 should make the whole circuit of the intervening conductors1 especially in very great distances1 so as actually to arrive at the exhausted side4 ,it may be sufficient to suppose1 that the additional quantity of fluid displaces and occupies the place of an equal portion of the natural quantity of fluid1 belonging to those conductors in the circuit which lay contiguous to the charged side of the glass4 ,this displaced fluid may drive forwards an equal quantity of the same matter in the next conductor2 and thus the progress may continue1 till the exhausted side of the glass is supplied by the fluid naturally existing in the conductors contiguous to it4 ,to account for the velocity with which electricity passes through good conductors1 ,dr4 ,franklin compares the electricity in the conductors1 to a wire in the bore of a tube1 which it exactly fills4--,if one end of this wire be moved forward1 every other part of it will move in the same direction1 and at the same instant4 ,dr4 ,priestley says1 it may be thought a difficulty upon this hypothesis1 that one of the sides of a glass plate cannot be exhausted1 without the other receiving more than its natural share2 particularly as the particles of this fluid are supposed to be repulsive of one another4 ,but it must be considered1 that the attraction of the glass is sufficient to retain even the large quantity of electric fluid which is natural to it1 against all attempts to withdraw it1 unless that eager attraction can be satisfied by the admission of an equal quantity from some other quarter4 ,when this opportunity of a supply is given by connecting one of the coatings with the rubber and the other with the conductor1 the two attempts1 to introduce more of the fluid into one of the sides1 and to subtract some from the other1 are made1 in a manner1 at the same instant4 ,the action of the rubber tends to disturb the equilibrium of the fluid in the glass2 and no sooner has a spark quitted one of the sides to go to the rubber1 than it is supplied by the conductor on the other2 and the difficulty with which these additional particles move in the substance of the glass1 effectually prevents its reaching the opposite exhausted side4 ,it is not said1 however1 but that either side of the glass may give or receive a small quantity of the electric fluid1 without altering the quantity on the opposite side4 ,it is only a very considerable part of the charge that is meant1 when one side is said to be filled while the other is exhausted4 ,the above is the substance of the theory most generally received4 ,it depends upon the following principles4 #a4 ,all terrestrial substances1 as well as the atmosphere which surrounds the earth1 are full of electric matter4 #b4 ,glass1 and other electric substances1 though they contain a great deal of electric matter1 are nevertheless impermeable by it4 #c4 ,this electric matter violently repels itself1 and attracts all other matter4 #d4 ,by the excitation of an electric1 the equilibrium of the fluid contained in it is disturbed1 and one part of it is overloaded with electricity1 while the other contains too little4 #e4 ,conducting substances are permeable to the electric matter through their whole substance1 and do not conduct it merely over their surface4 #f4 ,positive electricity is when a body has too much of the electric fluid1 and negative electricity1 when it has too little4 ,of these positions we shall now adduce those proofs1 drawn from different facts1 which seem in the strongest manner to confirm them4 ,i4 8,all terrestrial substances1 as well as the atmosphere which surrounds the earth1 are full of electric matter40 ,the proofs of this are very easy4 ,there is no place of the earth or sea where the electric fire may not be collected1 by making a communication between it and the rubber of an electric machine4 ,therefore1 considering that the whole earth is moist1 and that moisture is a conductor of electricity1 and that every part of the earth must thus communicate with another1 it is certain that the electric matter must diffuse itself as far as the moisture of the earth reaches2 and this may reasonably be supposed to be to the very centre4 ,the case is equally clear with regard to the atmosphere4 ,the extract from ,mr4 ,cavallo's journal1 given in the chapter upon atmospheric electricity1 is a sufficient proof that the atmosphere is full of electric matter4 ,,ii4 8,glass1 and other electric substances1 though they contain a great deal of electric matter1 are nevertheless impermeable by it40 ,the principal arguments for the impermeability of glass by the electric fluid are drawn from the phenomena of the ,leyden phial4 ,it is very plain that there is1 in charging this phial1 an expulsion of fire from the outside1 at the same time that it is thrown upon the inside4 ,this appears from numberless experiments1 but is most readily observable in the following4 ,let a coated phial be set upon an insulating stand1 and the knob of another phial brought near its coating4 ,as soon as sparks are discharged from the prime-conductor to the knob of the first1 an equal number will be observed to proceed from its coating to the knob of the second4 ,this is very remarkable1 and an unphilosophical observer will scarce ever fail to conclude1 that the fire runs directly through the substance of the glass4 ,dr4 ,franklin however concludes that it does not1 because there is a very great accumulation of electricity on the inside of the glass1 which discovers itself by a violent flash and explosion1 when a communication is made between the outside and inside coatings4 ,but it must be confessed1 there is here no other reason for concluding the glass to be impermeable1 than the probability that the electric matter is accumulated on one side of the glass and deficient on the other4 ,another argument against the permeability of glass and other electrics is1 that coated phials can receive but a very slight charge when their outside coating is insulated1 and this can be effected only with a very powerful machine4 ,,iii4 8,the electric fluid violently repels itself1 and attracts all other matter40 ,the proofs of this position have been so abundantly given in the course of this work1 particularly in the chapter on electric attraction and repulsion1 that we think it entirely superfluous to repeat them here4 ,,iv4 8,by the excitation of an electric1 the equilibrium of the fluid is disturbed1 and one part of it is overloaded with electricity1 while the other contains too little40 ,this position must be considered as entirely hypothetical1 as the manner in which the electric fluid is collected by the excitation of glass1 or any other electric substance1 has not yet been satisfactorily explained4 ,v4 8,conducting bodies are permeable by the electric fluid1 through the whole of their substance1 and do not conduct it merely over their surface40 ,take a wire of any kind of metal1 and cover part of it with some electric substance1 as rosin1 sealing-wax1 c4 then discharge a jar through it1 and it will be found that it conducts as well as without the electric coating4 ,this1 says ,mr4 ,cavallo1 proves that the electric matter passes through the substance of the metal1 and not over the surface4 ,a wire1 adds he1 continued through a vacuum is also a convincing proof of this assertion4 ,,vi4 8,positive electricity is an accumulation1 or too great a quantity of the electric matter contained in a body2 and negative electricity is when there is too little40 ,this position1 like the fourth1 must be considered as hypothetical--the peculiar nature of the electric fluid not admitting of experiments to prove1 or to disprove it4 ,,appendix4 ,,number ,i4 ,a description of the ,cement used for electrical purposes4 ,the best cement for electrical purposes is made by melting two parts of rosin1 two of bee's-wax1 and one of brick-dust1 or red ochre1 together4 ,this method of making cement is much preferable to that of rosin alone1 as it is not so brittle1 and at the same time it insulates equally well4 ,,number ,,ii4 ,a ,composition for ,coating ,cylinders or ,globes4 ,the most approved composition for lining glass cylinders or globes1 is made with four parts of ,venice turpentine1 one part of rosin1 and one of bee's-wax4--,they must be boiled together for about two hours over a slow fire1 and stirred very frequently2 afterwards the composition is left to cool1 when it is fit for use4 ,if a cylinder or globe is to be lined with this mixture1 a sufficient quantity must be pulverised1 and introduced into the glass2 then by holding the glass near the fire1 the composition is melted1 and by a little skill may be spread over all its internal surface1 to about the thickness of a wafer4--,the glass1 however1 must be heated very gradually1 otherwise1 there is danger of its breaking in the operation4 ,,number ,,iii4 ,to make the best kind of ,amalgam for exciting ,electrics4-- ,any metal dissolved in mercury or quick-silver will answer the purpose very well1 thus two parts of quick-silver with one of tin-foil1 or ,aurum ,mosaicum1 have been used to advantage4 ,but the most powerful composition for an amalgam1 is zinc and mercury1 in the proportion of one part of the latter1 with five of the former1 to which may be added a little bee's-wax or tallow1 the proper way of preparing this amalgam is the following4--,let the quick-silver be heated1 to about the degree of boiling water1 and let the zinc also be melted in an iron ladle4 ,pour the heated quick-silver into a wooden box1 and immediately afterwards pour the melted zinc into it likewise4 ,then shut the box1 and shake it about for some time4 ,you must now wait till the amalgam is cool1 or nearly so1 and then mix a little bee's-wax1 or mutton-suet with it1 by trituration4 ,,number ,,iv4 ,the preparation of electrical ,paint4 ,the electrician will very frequently have occasion to make use of paint1 both for ornament1 and convenience4 ,we shall therefore describe a pigment1 which1 while it looks very well1 insulates the instrument1 and answers a variety of other purposes4--,if a red colour is wished1 let a piece of red sealing-wax be dissolved in a sufficient quantity of highly rectified spirits of wine1 then let the substance which you intend to colour be warmed1 after which the paint may be laid on by means of a hair pencil4 ,care should be taken to render the instrument clean and dry1 especially if it be a glass one4--,two or three coats of this paint1 will generally answer every purpose4 ,if a black colour is preferred1 black sealing-wax may be used4 ,if the outside coating of a jar is desired to be coloured1 common oil paint will do much better than that above described1 for here insulation is not required2 a covering of some paint or other is always necessary1 in order to prevent the amalgam1 which is often scattered about the table where the apparatus is placed1 from corroding the tin-foil with which the jar is covered4 ,,number ,v4 ,to make the ,artificial ,bolognian ,stone4 8,calcine some common oyster-shells1 by keeping them in a good coal fire1 for half an hour2 let the purest part of the calx be pulverised and sifted4 ,mix with three parts of this powder1 one part of flowers of sulphur4 ,let this mixture be rammed into a crucible of about an inch and a half in depth1 till it be almost full2 and let it be placed in the middle of the fire1 where it must be kept red hot for an hour at least1 and then set it by to cool3 when cold turn it out of the crucible2 and cutting or breaking it to pieces1 scrape off1 upon trial1 the brightest parts2 which1 if good phosphorus1 will be a white powder40 ,,epitome ,,of ,,galvanism4 ,,chap4 ,i4 ,a ,short account of the discovery of ,galvanism4 ,this part of our subject has been called animal electricity1 by the greater part of those persons who have written upon it2--but this name seems to be improper2 for1 as an author of reputation on the subject1 remarks1 8it has by no means been proved that these phenomena depend either upon electricity or animal life40 ,while this is the case1 it is certainly best to distinguish this science by the name of its inventor ,louis ,galvani4 ,he was an ,italian1 and professor of anatomy at ,bologna1 when he made the discovery of ,galvanism1 which was entirely accidental1 as will appear in the following account4 ,whilst ,galvani was one day employed in dissecting a frog1 in a room where some of his friends were amusing themselves with electrical experiments1 one of them happened to draw a spark from the conductor1 at the same time that the professor touched one of the nerves of the animal4 ,the consequence was1 that the animal's whole body was instantly shaken by a violent convulsion4 ,astonished at the phenomenon1 and at first imagining that it might be owing to his having wounded the nerve1 the professor pricked it with the point of his knife1 to assure himself whether or not this was the case2 but no motion of the frog's body was produced4 ,he now touched the nerve with the instrument as at first1 and directed a spark to be taken at the same time from the machine1 on which the contractions were renewed4 ,upon a third trial the animal remained motionless2 but observing that he held his knife by the handle1 which was made of ivory1 he changed it for a metallic one1 and immediately the movements took place1 which never was the case when he used an electric1 or non-conducting substance4 ,after having made a great many similar experiments with the electrical machine1 he resolved to prosecute the subject with atmospheric electricity4 ,with this view he raised a conductor on the roof of his house1 from which he brought an iron wire into his room4--,to this he attached metal conductors1 connected with the nerves of the animals1 destined to be the subjects of his experiments3 and to their legs he fastened wires which reached the floor4 ,these experiments were not confined to frogs alone4 ,different animals1 both of cold and warm blood1 were subjected to them2 and in all of them considerable movements were excited whenever it lightened4 ,these movements preceded thunder1 and corresponded with its intensity and repetition2 and even when no lightning appeared1 the movements took place when any strong cloud passed over the apparatus4--,that all these appearances were produced by the electric fluid was obvious4 ,having soon after this suspended some frogs1 from the iron palisades which surrounded his garden1 by means of metallic hooks fixed in the spines of their backs1 he observed that their muscles contracted frequently and involuntarily1 as if from a shock of electricity4 ,not doubting that the contractions depended on the electric fluid1 he at first suspected that they were connected with changes in the state of the atmosphere4 ,he soon found1 however1 that this was not the case2 and having varied1 in many different ways1 the circumstances in which the frogs were placed1 he at length discovered that he could produce the movements at pleasure1 by touching the animals with two different metals1 which at the same time touched one another1 either immediately1 or by the intervention of some other substance capable of conducting electricity4 ,,chap4 ,,ii4 ,of the ,animals best fitted for ,galvanic ,experiments1 of the ,metals best calculated for making these ,experiments1 and of ,conductors4 ,almost every animal can be made to produce these muscular contractions by the ,galvanic power1 but those called cold blooded are the best4 ,thus frogs have been found the most convenient1 both on account of their size and abundance4 ,they also retain their muscular irritability to the ,galvanic influence longer than most other animals1 and it is asserted that strong convulsions can be produced in them many hours after the brain and spinal marrow have been destroyed2 and also that when pretty far advanced in the process of putrefaction they are capable of ,galvanic excitement4 ,no contractions have been produced in animals killed by corrosive sublimate1 nor in those which have been starved to death3 but a very slight motion can be made to appear in those killed by opium1 the electric shock1 or azotic gas4 ,with regard to the metals used to effect these motions1 almost any two will answer the purpose2 but the most powerful are the following1 viz4 ,gold4 ,zinc ,silver4 ,tin in conjunction with,molybdena4 ,lead ,steel4 ,copper4 ,those which have the most power are placed first2 that is zinc and gold1 will produce greater muscular contractions than tin and silver1 or tin and gold1 and so of the rest4 ,the process by which these wonderful appearances are produced consists in effecting1 by means of the ,galvanic apparatus1 a communication between a nerve and a muscle1 in any part of an animal body4 ,the part of the animal upon which the experiment is to be performed is denominated the animal arc3 and the ,galvanic instruments which form the communication between the muscle and the nerve1 are called the excitatory arc4 ,this latter generally consists of three pieces2 one fixed to the muscle1 another to the nerve1 and a third forming a communication between both4 ,this last1 called the communicator1 may be made of the same metal with either of the others1 or be different from both4 ,the best communicators or conductors1 are the following4--,the list begins with the most perfect4 ,malleable platina4 ,silver4 ,gold4 ,quicksilver4 ,copper4 ,brass4 ,tin4 ,lead4 ,iron4 ,the human body4 ,salt water4 ,fresh water4 ,the metallic ores are not so good conductors as the purified metals1 and their conducting power varies1 according to the nature of the ores4 ,the metallic salts are tolerably good conductors4 ,dr4 ,valli observed that human bodies are not all equally good conductors4 ,out of four persons in a company1 he found that when two of them formed the circuit of communication between the nerve and muscles of a frog1 the motions took place very readily4 ,when the third person formed the circuit1 the motions were very weak2 but that1 when the fourth person formed the communication1 no motion took place4 ,this experiment1 he adds1 was often repeated with the same success4 ,the effect however may be owing to the different dryness of the skin4 ,vitriolic acid1 and even alcohol1 appear to conduct the ,galvanic influence rather better than water4 ,the veins and arteries are not so good conductors as the nerves2 for when a blood-vessel forms part of the circuit of communication1 the contractions will take place only when ramifications of the nerves are adhering to it1 and if these be carefully separated1 the motion will not take place4 ,the same thing may be said of the tendons1 the bones1 and the membranes2 for when either of those parts is separated from the body1 and is introduced into the circle of communication between the muscles and nerves of a prepared frog1 no motion will ensue2 excepting1 indeed1 when those parts are full of moisture and in immediate contact with the nerve4 ,,chap4 ,,iii4 ,a ,description of the ,galvanic ,trough and ,pile4 ,professor ,volta's first contrivance for manifesting ,galvanism in a more vigorous manner than had hitherto been done1 was what he called a couronne de tasses4 ,this consisted of tumblers of glass1 half filled with water1 or salt and water4 ,these glasses or tumblers1 were so placed that a metallic arc1 in form of a ,c1 could be fixed with one leg in one glass1 and the other in the next glass4 ,on one end of each arc1 was fastened a small plate of silver or copper1 and on the other end1 a similar plate of zinc or tin4 ,these plates were immersed in the fluid contained in the tumblers4--,thus in the water of every glass there was a plate of silver or copper1 and another plate of zinc or tin4 ,the metallic arcs were formed of any good conductor4 ,when thirty or forty of these glasses were prepared1 the experimenter put one of his hands into the fluid contained in the first glass1 and the other hand into that in the last3 when this was done a shock1 something like the electrical one1 was experienced1 and would recur as often as the circuit was interrupted and completed4 ,mr4 ,volta remarks1 that alkaline solutions are used to the most advantage when one of the metals is tin and the other silver or copper2 but that where zinc is substituted for tin1 salt water is preferable4 ,after this discovery1 ,volta invented a much more convenient instrument1 which1 besides other advantages over the former1 was more powerful and less expensive4 ,the instrument is called the ,galvanic pile1 and very often the ,voltaic pile1 from its inventor4 ,it is made in the following manner--,take a number of circular plates of copper1 or silver and an equal number of tin or zinc of the same dimensions4 ,next provide a like number of round pieces of paste-board1 leather1 or any other substance capable of retaining moisture for a considerable time4 ,this leather1 cloth or other substance1 must be rather smaller than the metal plates and1 when used1 well moistened with salt and water4 ,now form a pile1 by laying alternately the zinc over the silver1 and1 the cloth or other moistened substance1 over the zinc2 and so on successively4--,by thus continuing the series to forty or fifty plates1 a ,galvanic pile will be constructed4 ,if the pile is intended to be of any considerable height1 it ought to be secured by pillars of varnished baked wood2 or strong glass tubes4 ,to get the shock1 one hand must touch the bottom1 and the other the top plate4--,the hands should be wet1 as the cuticle or external part of the skin is a bad conductor4 ,shocks may be received by applying the hands in this manner1 as long as the leather1 or other substance interposed between the zinc and silver1 continues moist2 but as soon as it becomes dry the operation closes4 ,the drying of the substance was a great inconvenience in the ,voltaic pile1 and the inventor proposed1 as a remedy for this1 to station the metallic plates at a greater distance from one another1 and to fill up the cells or intervals between them with a saline solution4 ,mr4 ,cruickshank1 an ,english chemist at ,woolwich1 improved this construction4--,his trough as it is called1 is made thus4-- ,get a wooden trough1 made of hard baked mahogany1 about thirty inches long1 and four or five wide and deep4--,on the inside let there be cut in the sides and bottom1 and at equal distances from one another1 as many grooves1 as the number of plates required to be put into the trough2--the grooves of a size to admit the plates4 ,the plates are to be cemented#ah separately to each of the grooves1 so that no fluid can pass from one cell to another4 ,in this instrument the plates are constructed by soldering a plate of zinc to one of copper4 ,the zinc1 or which is the same thing1 the spelter of the shops1 should be melted in a vessel which exposes but a small surface to the action of the air1 otherwise it would absorb oxygen so rapidly as to be converted into the flowers of zinc4--,the melted metal should be poured as soon as possible into a mould of the proper size1 made of stone or brass4--,it is not necessary that the plates of copper should be more than one tenth of the thickness of those of zinc4 ,the two plates are commonly soldered1 not through their whole extent1 but about one fourth of an inch from the edge2 so that at the edge their union may be complete4 ,care must be taken that all the plates be cemented to the trough in the same direction2 so as to have the copper side of every plate opposite to the zinc side of the next4 ,the liquid employed to fill up the cells between the plates1 is formed by diluting muriatic acid with water1 in the proportion of one ounce of the former to a pint of the latter4 ,when the trough is not in use1 it should be emptied of this solution 7which may be preserved for subsequent experiments1 unless saturated with the metals7 and then rinsed clean with fresh water4 ,this construction is preferable to the ,voltaic pile1 for experiments in which it is necessary to have the ,galvanic action for a length of time4 ,but for occasional experiments the pile is more convenient2 as the trough1 if suffered to remain long without the fluid1 is apt to crack and separate the cement from the plates1 which renders it necessary to cement them again4 ,when several batteries are required1 they should be disposed in the same order as if they all constituted one trough1 7observing through the whole series to keep the zinc surfaces constantly opposed to the copper ones17 and connected together by some metallic substance1 such as a piece of sheet lead1 or tin-foil1 about half the width of the trough4 ,batteries combined in this way should all be1 as nearly as possible1 of the same power4 ,for if a bad battery be united to five good ones1 each of the same number of plates1 the effect of the whole will be equal only to six times that of the bad one--as in electrical batteries1 if three jars of different sizes be charged together1 the whole charge will be equal to only three times that of the smallest jar4 ,,chap4 ,,iv4 ,the ,method of performing ,galvanic ,experiments with ,frogs2 with some conclusions drawn from them4 ,every sensible heart must be shocked with the idea of torturing defenceless animals1 merely to gratify an idle curiosity4 ,the chapter which we shall now lay before the reader is founded entirely on the assertions of other writers upon this subject2 to which1 however1 we have not the least doubt that the fullest credit is due4 ,but we have not chosen to prove the veracity of their statements by our own experiments1 believing that any small additional knowledge we might possibly have obtained in this way1 would have been purchased at too great a price--the sacrifice of feeling and humanity4 ,take a living frog1 and after amputating the hind legs1 7for they are the best1 on account of the number of joints7 let the largest nerve1 called the crural nerve1 be laid bare1 and surrounded with a slip of tin-foil1 or a piece of sheet lead--then lay a piece of zinc1 or other metal different from that on the nerve1 in contact with the neighbouring muscles2 form a communication by another piece of zinc1 or other good conductor1 between the metal in contact with the muscle and the armed part of the nerve1 and violent contractions will be produced in the limb4 ,there is another method of producing these convulsions1 which has been preferred on account of its simplicity4--,it is by forming a communication between a nerve1 armed as above1 and an adjoining muscle1 by a piece of zinc1 without the assistance of a communicator4--,this was one of the first methods of ,galvanizing frogs1 before the invention of the pile and trough4 ,but since these discoveries1 frogs have been made to show more violent convulsions4 ,we now proceed to relate some of the conclusions which have been drawn from the experiments on frogs4 #a4 ,the contractions produced in the limb of a frog are stronger the farther the metal is placed from the origin of the nerve4 #b4 ,when the metal has remained for some time on a particular part of the nerve the motion will cease2 but it may be renewed by changing the position of the metal1 and carrying it lower on the nerve4 #c4 ,contractions may be produced in the prepared limb of a frog1 by putting it in water1 and then bringing two metals in contact with each other1 at a short distance from the limb4 #d4 ,only those muscles to which the nerves lead suffer contraction from the ,galvanic influence4 #e4 ,when a contraction has taken place in any muscle1 no other will follow while the metals remain in contact4--,in order to renew the motions1 therefore1 the metals must be separated and joined again4 #f4 ,galvanic excitement1 instead of destroying the irritability of a muscle1 gives it an additional support4 ,dr4 ,valli1 an ,italian physician1 has fully confirmed this principle by the following experiment4 8,having prepared the wing of a fowl1 or the paw of a cat or dog1 ,i subjected it to the customary trial4 ,at the expiration of half an hour1 ,i armed the other wing of the fowl1 or the other paw of the cat or dog1 and had recourse to my exciting arc4--,the latter wing or paw1 however1 did not give any sign of electricity1 7for he conceived the motion to be occasioned by electricity17 while the parts which had been subjected in the first instance to the experiment1 still continued in a convulsed and agitated state40 #g4 ,galvanic experiments do not succeed so well in a room crowded with persons1 as when only two or three individuals are present4 #h4 ,galvanic contractions are more powerful the instant the animal is deprived of life1 than some time after2 and therefore more violent agitations can be produced in the living animal4 #i4 ,volta concluded that ,galvanism was generated by the metal1 and not by the animal upon which he operated4 ,these are the principal remarks which we think worth noticing4 ,if they do not content the reader1 we must refer him to ,wilkinson on ,galvanism2 where he will find a detail of almost every thing that happened in the ,galvanic world till the time he wrote4 ,,chap4 ,v4 ,various ,experiments with the ,galvanic ,pile4 ,the first experiments which we shall mention were performed by ,mr4 ,cruickshank1 with the ,galvanic pile4 ,he employed plates of zinc and silver1 #a4f inches square1 and the number of plates of both metals varied from forty to a hundred1 according to the power required4 ,the lower end of the pile we shall denominate the silver end1 because the plate at the bottom is of silver1 and the upper end the zinc end1 because the uppermost plate is of zinc4 ,the first experiment of ,mr4 ,cruickshank with the ,galvanic pile1 was upon water and silver wires4 ,these wires were passed through corks1 fitted into a glass tube filled with water1 and projected about one third of the way1 on both sides1 into the tube2 so that the space between the inner ends of the wires was one third of the length of the tube4 ,one of the corks was made perfectly tight by cement4 ,the tube was then placed upright in a tumbler of water1 with the uncemented end downwards4 ,as soon as a communication was made between the extremities of the pile by the wires1 small air bubbles began to ascend from the wire connected with the silver end1 and a white cloud made its appearance at the wire proceeding from the zinc end4--,the cloud gradually increased1 assuming a darker colour1 and at last it became purple1 and even black4 ,a few air bubbles were likewise observed upon this wire1 which ascended from it2 but when the pile acted well1 a considerable stream of air could be perceived4--,when this gas was examined1 it was found to be a mixture of hydrogen and oxygen1 in the proportion of three parts of the former to one of the latter4 ,no great reliance1 however1 can be placed on the accuracy of this analysis4 ,the wire proceeding from the zinc end1 was found much corroded1 and looked as if a portion of it had been dissolved4 ,mr4 ,cruickshank supposed the cloud formed round the wire of the zinc end to be the muriate of silver1 proceeding from the silver wire which had been somehow dissolved1 and afterwards precipitated in this state1 by the muriatic salts contained in the common water4 ,the next experiment was with distilled water1 a tincture of litmus1 and silver wires1 as before4 ,the apparatus being adjusted in the manner above described1 and one wire connected with one end of the pile1 while the other touched the other end1 gas immediately arose from both wires1 but in greater quantity from the one connected with the silver plate4 ,in a short time the whole fluid below the point of the wire from the zinc plate1 became red1 and the fluid below the wire from the silver plate1 looked of a deeper blue4 ,distilled water tinged with ,brazil wood1 soon became of as deep a purple as could be produced by ammonia4--,from the two last experiments1 ,mr4 ,cruickshank was led to suppose1 that an acid1 probably the nitrous1 is produced at the wire connected with the zinc plate1 and an alkali1 probably ammonia1 at the one connected with the silver end of the pile4 ,as hydrogen gas1 whether heated or in its natural state1 reduces metallic oxyds1 ,mr4 ,cruickshank resolved to subject solutions of metallic oxyds to the hydrogen gas which was produced by the pile4--,the result answered his expectation1 for in a minute or two after the communication was formed1 fine metallic needles or crystals1 something resembling a feather1 were perceived round the wire connected with the silver plate4--,the oxygen too which escaped from the metal1 and that generated from the fluid used in the solution1 was commonly pure1 when an excess of acid was added to take up the alkali4--,the acetite of lead and the sulphate of copper1 were among the oxyds experimented upon1 but whatever the metal was1 the results coincided4 ,these experiments were made in a tube like the preceding ones4--,a number of experiments were made by the same gentleman upon the earths1 but we shall not detail them2 we must content ourselves with some conclusions drawn from his observations4 #a4 ,hydrogen gas1 mixed with a small portion of oxygen and ammonia1 is somehow disengaged at the wire communicating with the silver extremity of the pile2 and this effect is equally produced1 whatever the nature of the metallic wire may be1 provided the fluid operated upon be water4 #b4 ,when metallic solutions are used1 the same wire which separates the hydrogen gas1 revives the metallic calx1 and deposits it at its extremity1 in its pure metallic state2 in this case no hydrogen is disengaged4 ,the wire employed for this purpose may be of any metal4 #c4 ,of the earthy solutions1 only those of magnesia and argill are decomposed by the wire3 a circumstance which strongly favours the production of ammonia4 ,,chap4 ,,vi4 ,experiments on the deflagration of ,metals by the ,galvanic ,pile4 ,the pile with which these experiments were made consisted of thirty-six plates of silver1 and an equal number of zinc ones1 between which were interposed disks of flannel1 moistened with a solution of the muriate of ammonia4--,each plate had a diameter of ten inches1 or contained #gh4eh square inches2--consequently the whole surface of silver in the pile1 reckoning only one side1 was #bhbh4eg square inches1 and that of zinc the same4 ,with this instrument1 in ,december #ahja1 gold1 silver1 copper1 tin1 lead and zinc were deflagrated with surprising facility4 ,the gold burned with a vivid white light1 inclining a little to blue1 and deposited an oxyd of a deep purplish-brown colour4--,the silver gave a vivid flame of a greenish hue1 and extremely brilliant4 ,its oxyd was of a blackish colour4 ,the copper presented phenomena similar to those which attended the gold4--,lead gave a very vivid light1 of a dilute bluish purple4--,the tin afforded a light similar to that of the gold1 but burnt with much less energy2 probably because the leaves were thicker4 ,the zinc gave a blueish white flame1 which was edged1 at the moment of contact1 with red4 ,it was more difficult to inflame than any of the preceding metals1 but the leaves were likewise much thicker4 ,the oxyds of the four last metals were not examined4 ,water was poured upon the upper plate of the pile1 so as to form a standing pool2 and several pieces of the same kind of metals with those before experimented upon1 were presented to the plate through this aqueous medium1 and were deflagrated4 ,they afforded a flame of the same colour as when they were brought to the bare plate4--,a vapour was sometimes perceptible immediately after the deflagration1 and was supposed to arise from a portion of water converted into steam by the intense heat4 ,it is very remarkable that the shocks taken from this pile1 which produced such astonishing effects upon metals1 could be received with but very trifling inconvenience1 through the human body4 ,besides these experiments1 which were made by a society of gentlemen1 a variety of others were performed1 from which nearly the same conclusions were deduced4--,two other facts1 however1 deserve notice4 #a4 ,when metallic leaves are deflagrated in carbonic-acid gas1 the flame is weak3 but when in oxygen gas1 the communication between the upper and under plates of the pile is no sooner formed1 than the metallic leaves are destroyed with one sudden flash4 #b4 ,when metals are subjected to ,galvanism in an exhausted receiver1 they emit light but are not oxydated4 ,,chap4 ,,vii4 ,further ,galvanic ,experiments on ,metals1 and on other ,substances4 ,it is hardly necessary to mention1 that every experiment made by means of the ,galvanic pile may be performed1 with equal success1 with the trough4 ,the experiments related in this chapter may be effected by the pile1 but they cannot be done with the same convenience as when troughs are used4 ,the battery#ai employed in these experiments consisted of sixty pieces of silver1 and a like number of zinc1 each two and a quarter inches square4 ,the shock produced by this trough1 by means of two metallic conductors1 was distinctly felt in the shoulders1 and the contraction or spasm was so violent1 as to render the operator unable to hold the conductors1 when in contact with the plates by which the trough terminated each way4--,a sensation resembling that produced by hot water1 was at the same time felt in the wrists and fore-arm4 ,a small steel wire1 which was used for the conductor to form the communication1 upon its contact with the plates1 produced a vivid spark and bright scintillations4--,when a piece of phosphorus was placed upon the end of this wire1 and made a part of the circuit1 it was instantly inflamed4 ,another battery of the same size being connected with the one above described1 gun-powder was fired1 and gold leaf deflagrated without any perceptible residuum--being probably volatilised by the heat occasioned by the experiment4 ,mr4 ,davy1 secretary of the ,royal ,society1 placed a small piece of pure potash 7which had previously been exposed to the atmosphere1 so as to render it a conductor of the ,galvanic fluid17 upon an insulated plate of platina1 connected with the negative#bj end of a battery1 of the power of two hundred and fifty plates1 six inches by four1 in a state of intense activity4--,a wire communicating with the positive end1 was brought in contact with the upper surface of the alkali4 ,the whole apparatus was in the open air4 ,under these circumstances a vivid action was soon perceived4--,the potash began to fuse at both points where the fluid acted upon it4--,there was a violent effervescence at the upper surface3--at the lower or negative surface there was no liberation of elastic fluid1 but there appeared small metallic globules1 very much resembling quick-silver4 ,some of these globules burned with an explosion and a bright flame1 as soon as they were formed1 while others remained which were merely tarnished2 and finally a white film was formed over their surfaces1 which was afterwards found to be pure potash4 ,soda was acted upon in the same manner as potash1 and exhibited the same results2 but its decomposition required a stronger action of the battery1 or it was necessary that the soda should be in smaller pieces than the potash4 ,the metallic globules produced from the potash remained fluids in the open air1 at the time of their production2 but those from soda1 though fluid at the time of their formation1 upon cooling1 became solid1 having much the lustre of silver4 ,the alkalies could be made to produce metallic results in vacuo4 ,since ,mr4 ,davy's first experiments on this subject1 several others have been made1 much in the same manner1 upon the earths4 ,messrs4 ,pontin and ,berzelius1 two ,swedish chemists1 have succeeded in obtaining metallic amalgams from lime1 magnesia1 strontites and barytes2 but they could produce no such effect on alumine and silex4 ,mr4 ,davy however effected this1 by a battery of #cfjjj square inches4--,he also improved upon their other discoveries4 ,he1 by distillation1 drove off the mercury from the amalgamated metals which they obtained from the earths1 and procured a pure metal4 ,ammonia was also found to contain a metal4 ,this discovery inclines one to believe1 that the air we breathe contains metal in a gaseous state1 as azote1 which is a component part of ammonia1 forms a large portion of our atmosphere4 ,when compounds1 soluble in water1 were put into water contained in agate cups1 and subjected to the action of ,galvanism1 their decomposition was rapid4--,a solution of the sulphate of potash1 being put into two cups and ,galvanised by fifty pair of plates1 for four hours1 the acid was found by itself in the cup connected with the positive end of the battery1 and the alkaline basis in the cup communicating with the negative end4 ,similar phenomena took place in solutions of sulphate of soda1 nitrate of potash1 nitrate of barytes1 phosphate of soda1 sulphate1 succinates1 oxalate and benzoate of ammonia2 also with alum4 ,when muriatic salts were used1 they afforded oxymuriatic acid4 ,when metallic solutions were employed1 metallic crystals and an oxyd were deposited on the negative wire1 and a great excess of acid was found in the positive cup4--,strong solutions afforded signs of decomposition quicker than weaker ones4 ,we could enumerate a variety of similar experiments1 but the limits of our work forbid it4 ,,chap4 ,,viii4 ,experiments which may be performed without the assistance of the ,battery4 ,to shew the ,galvanic light4 ,place a piece of zinc upon your tongue1 and a piece of silver between your cheek and upper jaw2 then move your tongue so as to bring the two metals in contact with each other1 and you will perceive a very curious sensation upon your tongue1 accompanied by a cool sub-acid taste1#ba and at the same time you will see a flash of light1 whether your eyes be open or closed4 ,the sub-acid taste resembles1 in a degree1 that produced by electricity4#bb ,to affect the ,taste by means of ,water4 ,place a tin or pewter bason filled with clean water upon a silver mug3 with both your hands1 which must previously be wet with a solution of salt in water1 grasp the silver vessel1 and put your tongue into the water1 taking care not to touch the tin or pewter vessel with any part of your body2 you will now perceive an acid taste2 which will be more sensible1 if you withdraw your hands from the silver vessel while your tongue remains in the water1 and then replace them4 ,to prove that ,earth-,worms have a nervous system4 ,place an earth-worm upon a plate of zinc1 resting on a larger plate of silver4--,the animal1 as soon as it approaches the silver1 seems to be repulsed by a painful sensation1 and at last becomes fatigued by its repeated and fruitless exertions to make its escape1 which nothing apparently prevents4 ,this evidently proves that the animal is provided with a nervous system1 as experiments have proved that ,galvanic irritation is excited only in the nerves4 ,,chap4 ,,ix4 ,some common ,effects which are supposed to be occasioned by ,galvanism4 ,we have already remarked1 that a sub-acid taste is perceptible when two different metals are applied to the tongue and fauces3 it has also been found that ,galvanism affects the taste1 when two different fluids and a single metal are in contact with the tongue4 ,upon this principle a variety of known facts have been accounted for4--,for example--,it has long been observed that beer1 cyder1 c4 when drunk from a tin or silver vessel1 were more palatable than when received from a vessel of glass1 or any other substance not metallic4 ,the supposed explanation of this1 is as follows4--,when the outer extremity of the vessel is applied to the under lip1 rendered moist by the saliva1 and the tongue is extended so as to be in contact with the liquid contained in the vessel1 a ,galvanic arc is formed1 which produces the brisk and lively taste4 ,it has been supposed1 by persons fond of this theory1 that snuff1 when taken from a metallic box1 excites a more agreeable sensation than when taken from a box of tortoise shell1 or leather4 ,the fact that a silver spoon becomes discoloured by being used for eating eggs1 is familiar to every one4 ,this1 also1 is attributed to the ,galvanic action4 ,by experiment1 sulphur has been discovered in both the albumen and yolk of an egg4--,the ,galvanic combination is between the sulphur of the egg1 the silver spoon1 and the saliva2 for no tarnish is produced on the spoon when it is immersed in either the albumen or yolk2 and that part of the spoon which enters the mouth is most discoloured4 ,in every ,galvanic experiment1 water is decomposed into its constituent parts1 hydrogen and oxygen gases4 ,these things being premised1 the fact is easily accounted for4--,the hydrogen1 which before the operation is nascent in the water1 7which holds the sulphur in solution7 now readily unites with the sulphur1 and forms sulphurated hydrogen gas1 which produces the tarnish on the silver4#bc ,we shall mention a few other common appearances1 and leave the solution to the ingenuity of the reader4 ,when copper sheathing is fastened on a ship with iron nails1 the nails1 and particularly the copper1 are found to be corroded about the places of contact4 ,works of metal1 the parts of which are joined by a solder of a different metal1 are observed to tarnish about the places where the different metals meet4 ,a seam which has been soldered so accurately that it cannot be perceived by the eye1 may be discovered by passing the tongue over it4 ,,chap4 ,x4 ,the ,effects of ,galvanism on ,vegetables4 ,this part of ,galvanism has been particularly attended to by ,humboldt1 a ,german4 ,he first observed the irritability of the vegetable fibre4 ,remarking the great similarity of appearance between the substance of mushrooms and the muscular fibre1 he wished to ascertain whether they possessed a similar power of contraction4 ,he accordingly made a considerable number of experiments1 from which he concluded that the different kinds of mushrooms1 which in becoming putrid emit an animal insipid cadaverous smell1 are as perfect conductors in the ,galvanic chain as the organs of animals4 ,his experiments likewise proved that they possessed irritability4 ,mr4 ,humboldt afterwards directed his inquiries to the manner in which ,galvanism acted upon the irritable fibre1 which1 as we have already mentioned1 he first observed4 ,these experiments1 however1 were unsuccessful4 ,we shall not therefore relate them4 ,the effects of ,galvanism on vegetation are supposed to be deleterious1 as will appear from the following extract from the 8,monthly ,magazine40 8,it often happens1 that some of the limbs of fruit trees1 trained against a wall1 are blighted and die2 while others remain in a healthy and flourishing state4 ,this evil is1 by gardeners1 generally attributed to the effects of lightning4 ,but1 if this were the case1 would not the violent action of the electric fluid produce a laceration of the branch and stalk of the tree8 ,no such effect is to be perceived4 ,it therefore appears to me1 that we must seek some other cause for this evil1 and ,i flatter myself that ,i have discovered the real one4 ,a few years since1 when ,galvanism was first introduced to public notice1 ,i constructed a pile1 consisting of about one hundred plates of copper and as many of zinc1 each about two inches square4 ,among other experiments1 ,i applied it to the branch of a tender plant1 7a species of the ficoides47 ,having left it for about an hour1 on my return ,i found the branch withered1 and hanging close to the stalk4 ,it immediately occurred to me1 that ,galvanism might be the cause of the above mentioned defect in wall fruit trees1 occasioned by the oxydation of the nails1 by which they are oftentimes fastened 7for ,i conceive ,galvanism to be produced1 in a greater or less degree1 by every metal passing into a state of oxydation47 ,recollecting that the limb of a cherry tree in my garden had1 nearly a year before1 been fastened to the wall with an iron cramp1 ,i instantly examined it1 and found it dead2 though1 when fastened1 it was a flourishing1 healthy limb1 at least an inch in diameter1 and nine feet in length4 ,i have since examined several peach and nectarine trees2 and wherever ,i discovered a limb dead1 ,i invariably found that one or more of the nails which fastened it were in contact with the bark4 ,a limb of a peach tree puzzled me for some time4 ,it was dead1 but ,i could not perceive that any of the nails were in contact with it1 7the scraps of cloth being left pretty long47 ,after a narrow search1 however1 ,i found the mud1 of which the wall was built1 considerably stained with rust1 immediately under the branch3 and on digging into the wall with my knife1 ,i brought the hidden mischief to light4--,it was part of a very large spike nail1 and which lay about an inch below the surface4 ,on mentioning some of those circumstances to a friend1 he observed1 that about a year before1 he had fastened some currant trees to a wall1 with iron hooks4 ,on examination1 almost every limb so fastened1 was dead4 ,the effect of the ,galvanism in these cases will probably be found to be greater in rainy seasons1 as the oxydation then goes on more rapidly than it does at other times4 ,hence it appears that1 in training fruit trees1 wooden pegs or cramps1 should be used instead of iron2 or else1 that care should be taken that the iron do not touch or come near to a limb4 ,,chap4 ,,xi4 ,of medical ,galvanism4 ,galvanism1 like electricity1 has been applied to the human body1 for the purpose of removing complaints1 and apparently with equal success4 ,the ingenious ,galvani1 immediately after his discovery of ,galvanism1 7or as he called it1 animal electricity17 attempted to explain the causes of several diseases by it4 ,thus in a complaint where there was a total loss of contractile power1 as the paralysis1 he ascribed the cause to the interposition of a non-conducting substance1 which prevented the passage of the ,galvanic fluid from the nerve to the muscle1 and from the muscle to the nerve4 8,if artificial electricity 7says he17 be conveyed to the head1 the nerves or spinal marrow1 by means of the conductor of the ,leyden phial1 paralysis1 apoplexy1 and even death1 will be induced1 according as the phial is charged with a greater or less quantity of the electric fluid4--,if such effects result from common electricity1 may it not be presumed that a sudden afflux of animal electricity towards the brain1 may be productive of the most fatal consequences40 ,but omitting1 as wholly conjectural and unsatisfactory1 all theories relating to the effect which ,galvanism has upon the animal conomy1 we shall proceed to relate known facts1 and the method of applying ,galvanism for the relief of certain morbid affections of the human body4 ,the general mode of operating with ,galvanism1 is to apply small portions of it at first1 and gradually to increase the shock1 as circumstances may dictate4 ,it has been customary to remove the cuticle 7by means of a blister or otherwise17 from the parts of the body to which the wires1 communicating with the two extremities of the battery1 are to be applied4 ,this method1 which was adopted because the cuticle is a very bad conductor1 gave excruciating pain to the patient4 ,mr4 ,wilkinson has found it unnecessary1 as by moistening the parts1 and applying pieces of gold leaf or ,dutch-metal1 he has succeeded in producing the desired effect4 ,during an operation1 one of the conducting wires should be kept in contact with one of the metallic leaves1 while the other conductor is to be removed1 immediately after it has been brought in contact with the other metallic-leaf--and then replaced and removed successively4 ,the negative wire of a battery is the most powerful1 and it is necessary in some cases to attend to this fact4 ,in a short time after ,galvanism has been applied to a part of the body1 a redness becomes perceptible about the part2 and if the application be continued too long1 vesications and ulcerations will be produced4 ,these symptoms are a little troublesome at first1 but do not require any particular treatment for their cure4 ,galvanism should be applied twice in twenty four hours1 otherwise it is supposed the intervals would be so long1 as to prevent any good effects which might arise from it4 ,we shall now enumerate some disorders in which ,galvanism has proved beneficial4 ,in paralytic affections it has afforded considerable relief4--,two instances of mental derangement are recorded by professor ,aldini1 nephew to ,galvani1 in which its effects were truly surprising4--,one of them afforded an instance of a gradual diminution of the mental energies1 which ultimately sunk into stupidity4 ,the other was of an opposite nature3--the system was in a state of violent excitement1 and the patient raving and unmanageable4 ,in rheumatism1 spasmodic affections1 and deafness1 where it does not arise from a natural defect in the organ1 ,galvanism has been applied generally with advantage4 ,but the most astonishing effects of this wonderful principle have been displayed in cases of suspended animation4 ,mr4 ,humboldt made the first experiments relative to this part of our subject1 on apparently dead linnets4 ,he put a piece of zinc into the bill1 and thrust a sharp piece of silver into the bird1 near the other extremity of the body--he then formed a communication between the two1 by an iron wire4 8,what 7exclaims he7 was my surprise1 when ,i perceived1 the moment the contact took place1 the linnet open its eyes1 stand erect on its feet1 and flutter its wings2 it again breathed during six or eight minutes1 and then expired tranquilly40 ,galvanism is now applied to persons apparently dead1 from drowning1 hanging1 or exposure to noxious gases4 ,in such cases1 the body should be divested of its clothing1 and placed in a warm bed nearly approaching the natural temperature1 and at the same time slight ,galvanic shocks should be passed through the body1 in such a direction as to affect the heart4--,thus by combining this1 with the usual means1 the most advantageous consequences may be expected4 ,it may be laid down as a principle1 that1 in all cases where animation is suspended1 and the principle of irritability not destroyed1 the stimulus of ,galvanism and electricity1 if prudently employed1 may rouse the dormant energies of vitality1 and restore the system to its natural state of activity4 ,,chap4 ,,xii4 ,the ,identity of ,galvanism with ,electricity considered4 ,it has been supposed by many1 that the phenomena of ,galvanism and electricity depend upon the same cause4 ,others1 however1 controvert this opinion1 and affirm that ,galvanism is a fluid sui generis4 ,that there is a great similarity between some of the phenomena of ,galvanism and those of the electric fluid1 is evident2 but this analogy cannot be traced in every instance4 ,it is not our province to enter into this controversy2 we shall only relate a few facts upon which it is founded1 and leave the speculative reader to draw from them his own conclusions4 ,facts which seem to indicate that ,galvanism and ,electricity are the same ,fluid4 ,both ,galvanism and electricity exhibit light1 in their passage from one conductor to another1 through an intervening space of air4 ,both affect an electrometer4 ,the deflagration of metals may be produced by either4 ,electricity1 as well as ,galvanism1 produces muscular contractions in animals1 a short time after death4 ,facts in which ,galvanism and ,electricity differ from each other4 ,some good conductors of electricity are not good conductors of ,galvanism2 as was shewn by ,dr4 ,fowler4 ,the manner of exciting ,galvanism is different from that of exciting electricity2--the former being collected most copiously from conductors1 and the latter from non-conductors4 ,the electric fluid affects the sense of smelling--but no smell has ever been observed from ,galvanism4 ,the electric shock operates on the body by a sudden and percussive effect--while the one which follows the ,galvanic process seems to arise from a constant current1 attended by a jarring and tremulous sensation4 ,in the decomposition of water by ,galvanism1 hydrogen gas is formed at one of the wires1 and oxygen at the other4 ,in that by electricity1 both gases arise from the same wire4 ,,finis4 ,,index ,,to ,,the ,,epitome ,,of ,,electricity4 ,a pinus's theory of electricity1 #aae ,amalgam1 directions for making the best kind of1 #abf ,apparatus1 electrical1 directions for using the1 #fh ,attraction1 electrical1 #ba ,aurora ,borealis1 how to imitate the1 #gi ,b ,balloons1 inflammable air1 #gg ,battery electrical1 and experiments with it1 #bh ,bells1 electrified1 #gf ,black lead1 useful for points to lightning rods1 #ea ,bladder1 electrified1 #ic ,bolognian stone1 artificial1 to make1 #abg ,bottle director described1 #fe ,c ,candle1 to light a1 #ia ,cannon1 the electrical1 #if ,cards pierced by electricity1 #ij ,cavallo1 general laws deduced by him from experiments made with electrical kites1 #df ,cement1 how to make1 #abe ,charcoal useful at the lower extremity of lightning rods1 #ec ,chemical theory of electricity1 #aaa ,clay swollen by the electrical shock1 #ij ,colours changed by the electrical shock1 #hg ---- experiments on1 #hg1 #hh ,communication1 electrifying by1 #ae ,conductors1 of1 #f ---- luminous1 #hb ,constellations1 to represent the1 #aja ,cotton1 electrified1 #ib ,cylinders1 of1 #i ---- composition for lining1 #abe ---- plates may be substituted for1 #ad ,d ,dance1 electrical1 #ge ,decomposition of water by electricity1 #ajc ,director1 bottle1 description of1 #fe ---- use of1 #fg ,discharging electrometer1 description and use of1 #fg ---- rod1 luminous1 #ajc ,du ,fay's theory of electricity1 #aji ,e ,electric attraction and repulsion1 #ba ---- ---- ---- ---- exemplified1 #bb1 #bd ---- battery and experiments with it1 #bh ---- eel1 an account of the1 #ef ---- fly1 described1 #ah ---- light1 experiments with1 #gi ---- spark1 #af ,electric spider1 #be ----s1 and phenomena produced by them1 #b1 #c1 #f1 #h ---- experiments with charged1 #hf ,electrical machine described1 #i1 #ac ,electricity1 the identity of with lightning1 #dj ---- how it may be applied to the best advantage1 #fe ---- animal1 #ee ---- apparatus necessary for1 #fd ---- atmospheric1 danger of making experiments with1 #db1 #dd ---- medical1 #fc ---- positive and negative1 #b ---- various theories of1 #ajh ,electrometer described1 #cf1 #fd ---- instructions for using1 #cg ,electrophorus described1 #cc ---- experiments with the1 #cd ,excited1 what is intended by1 #a ,experiments1 practical rules for making1 to the best advantage1 #fh ---- promiscuous1 #id ,explosion1 the lateral1 #aja ,f ,figures made upon glass c4 by means of electricity1 #ig ,fountain1 the electrified1 #ajd ,fractured jar1 how repaired1 #gj ,franklin1 ,dr4 his experiment with a kite1 #dj ---- ---- ---- ---- for illustrating his theory of thunder storms1 #gh ---- his theory of electricity1 #aaf ,friction1 electric1 #fe ,g ,gibbes ,dr4 his theory of electricity1 #aac ,glass1 metals forced into1 by an electric explosion1 #cj ,gun-powder fired by an electric explosion1 #cj ,i ,jack1 the electrical1 #id ,jar1 electrical1 fractured1 how repaired1 #gj ,k ,kite1 ,dr4 ,franklin's experiment with a1 #dj ---- electrical1 structure and use of the1 #da ---- ---- ,cavallo's directions for using the1 #dc ,l ,lane's discharging electrometer1 #fg ,leyden phial described1 #bf ---- ---- experiments with the1 #bg ---- vacuum1 #ha ,light1 electric1 experiment with1 #gi ---- ---- flashing between two metallic plates1 #hc ,lightning1 the identity of with electricity1 #dj ---- rods1 the structure and use of1 #dh1 #ed ---- ---- improved by professor ,patterson1 #ea ,luminous conductor1 #hb ---- to render various substances1 #hd ---- shower1 #ajb ,m ,machine1 electrical1 described1 #i ,magic picture1 #hf ,magnetic needle1 effect of electricity on the1 #ca ,medical electricity1 #fc ,metallic oxyds revivified1 #ca ,metals forced into glass by an electric explosion1 #cj ,n ,natural state1 meaning of1 #b ,nollet's ,abb1 theory of electricity1 #aaj ,non-electrics1 #b1 #g ,o ,oxyds1 metallic1 revivified1 #ca ,p ,paint1 for electrical purposes1 preparation of1 #abf ,paper stained by an electric explosion1 #ca ,picture1 magic1 #hf ,pointed bodies1 their influence on electricity1 #ag1 #ib ---- ---- phenomena attending1 #ag ---- ---- conclusions respecting1 #ba ,powder1 gun1 fired by electricity1 #cj ,prime-conductor1 #ab ,r ,repulsion1 electrical1 #ba ,richman1 ,professor1 killed by atmospheric electricity1 while making experiments with it1 #db ,rubber1 defined1 #b ---- described1 and directions respecting it1 #aj ,s ,shower1 luminous1 #ajb ,snake1 electrical1 #ajb ,spark1 electric1 #af ---- ---- applied for curing deafness c41 #ff ---- ---- to render the1 visible in water1 #hd ,stream ---- useful in curing diseases of the eye1 #fg ,syphon1 the capillary1 electrified1 #ajj ,t ,terms1 explanation of1 #a ,thermometer1 effect of electricity on the1 #cb ,thunder-house1 experiments with the1 #ed ,torpedo1 an account of the1 #eh ---- artificial1 to make1 #fj ,tube1 spiral1 #hc ---- the self-charging1 #ie ,v ,vacuum1 what is meant by the term1 #gi ---- ,leyden1 #ha ,vegetables1 effect of electricity on1 #fa ,velocity of electricity1 #ae1 #bi ,w ,water decomposed by electricity1 #ajc ,wheels1 multiplying1 may be added1 with advantage1 to an electrical machine1 #ab ---- self-moving1 described1 #gd ,wilson's theory of electricity1 #aji ,wine1 spirit of1 fired by electricity1 #hi ,,index ,,to ,,the ,,epitome ,,of ,,galvanism4 ,a ,animals1 cold blooded1 best for ,galvanic experiments1 #aca ,arc1 animal1 and excitatory1 #acb ,b ,berzelius1 his experiments1 #adg ,c ,conclusions1 #aci1 #adc ,conductors1 ,galvanic1 #acc ,cruickshank's1 ,mr4 experiments1 #adj ,d ,davy ,mr4 his experiments1 #adf ,diseases in which ,galvanism has afforded relief1 #aef ,e ,effects1 common1 supposed to be occasioned by ,galvanism1 #aej ,f ,frogs1 ,galvanic experiments upon1 #ach ---- ---- ---- ---- conclusions drawn from1 #aci ,g ,galvanism1 a short account of1 #abi ---- medical1 #aed ---- identity of1 with electricity1 considered1 #aeg ,l ,light1 ,galvanic1 to exhibit1 #adh ,m ,metals1 most suitable for ,galvanic experiments1 #acb ---- on the deflagration of1 by the ,galvanic pile1 #adc ,p ,pile1 ,galvanic1 description of the1 #acd ---- ---- experiments with the1 #adj1 #adc ---- ---- its two extremities in opposite states1 #adf ,pontin ,mr4 his experiments1 #adg ,t ,trough1 ,galvanic1 description of1 #acf ---- ---- experiments with the1 #adf ,v ,vegetables1 effects of ,galvanism on1 #aeb ,w ,water1 the taste of1 affected by the ,galvanic influence1 #adi ----- ,footnote #a3 ,apuleius1 ,floridor1 page #cfa4 ,footnote #b3 ,theophrast4 4 ,footnote #c3 ,dr4 ,falconer1 in a paper inserted in the 8,memoirs of the ,manchester ,society10 has endeavoured to prove by quotations from the writings of antiquity1 and by much ingenious reasoning1 that the ancients were not only acquainted with the electrical shock1 but that it is probable even the method of drawing down lightning from the clouds1 was known in very early times1 and particularly to ,numa ,pompilius1 the second king of ,rome2 and that his successor ,tullius ,hostilius perished1 by his unskilful management of so dangerous a process4 ,those who wish to pursue this subject1 we refer to the above mentioned paper in #c vol4 ,memoirs of the ,literary and ,philosophical ,society of ,manchester1 page #cgh4 ,the same opinion is ingeniously defended1 in a work of ,m4 ,dutens1 entitled1 8,origine des ,decouvertes atribuees aux ,modernes40 ,some curious quotations from the ancients1 on electricity1 are likewise contained in the ,gentleman's ,magazine for ,july #aghe1 page #ebb4 8,to these may be added a curious passage in ,signor ,boccalini's advertisement from ,parnassus 7century #a4 chap4 #df17 published more than a hundred years before the date of ,franklin's discovery1 and in which the identity of the electric fluid and lightning is said to be revealed40 ,miller's ,retrospect1 #a vol4 page #bd4 ,but after attentively considering all these discoveries1 we cannot help acceding to the opinion of the learned ,president ,gouget1 a man who had most thoroughly investigated the origin of science among the ancients1 and we are fully persuaded that what he says of several other subjects is precisely the truth in regard to electricity4--8,all 7says he7 which we read on this subject in the writings of the ancients1 ought to be regarded as mere ideas advanced at random1 without knowledge1 without principles1 and without any kind of foundation4 ,if some of the ancients1 for example1 have said1 that the earth was a spheroid1 flattened at the poles2 that it revolved round the sun2 that the comets were planets1 whose periodical revolutions were completed in a certain number of ages2 that the moon might be habitable2 that that planet was the occasional cause of the flux and reflux of the sea1 c42 we ought not to regard these propositions in their mouth1 as the effect and the result of the knowledge which these philosophers had acquired4 ,on the contrary1 we ought to place them on the footing of those hypotheses which an uncertain and ill-regulated imagination daily produces4 ,i say so1 because none of the ancient philosophers have been able to give reasons for what they delivered2 which we may be easily convinced of1 by reading the manner in which the writers of antiquity relate the opinions of their learned4 ,there we see1 that the ancients had no reasons preponderating to adopt one system rather than another2 neither were they ever able to give any of them the slightest demonstration4 ,for the rest1 ,i do not pretend to make this a matter of reproach to the ancients4 ,they were destitute of all helps proper to acquire these branches of knowledge4 ,if1 nevertheless1 they have sometimes hit upon the truth1 we ought to attribute it to pure chance2 and be sensible1 that1 as they wavered in uncertainty1 and ran through all possible combinations1 it is not astonishing that they should hit upon the true one1 because the number of these sorts of combinations is not infinite4 ,in this respect consists the characteristical difference between the astronomical learning of the ancients and that of the moderns4 ,what at this time we affirm of the figure of the earth1 of the system of the heavens1 of the cause of the flux and reflux of the sea1 c4 is not the effect of chance and imagination2 it is the result of much observation1 experience1 and reflection1 and every astronomer is able to support by reasons the system which he has thought fit to embrace40 ,origin of ,laws1 ,arts1 and ,sciences1 ,vol4 ,,iii1 ,book ,,iii1 ,chap4 ,,ii1 ,article ,,iv4 ,footnote #d3 ,bayle in ,vita ,aristot4 ,footnote #e3 ,gilbert1 ,de ,magnete4 ,lib4 #b1 ,cap4 #b4 ,footnote #f3 ,philos4 ,trans4 abridged1 ,vol4 #g1 page #ah4 ,footnote #g3 ,the author of the article ,electricity in the ,encyclopdia1 ascribes the merit of this discovery 7if any merit can arise from a discovery made by accident7 to ,mr4 ,van ,kleist1 dean of the cathedral of ,camin4 ,on what authority he does this1 we are unable to state4 ,the following 7he says7 is the account of it1 which the dean1 on the #dth of ,november #agde1 sent to ,dr4 ,leiberkulm at ,berlin1 8,when a nail1 or a piece of thick brass wire1 c4 is put into a small apothecary's phial1 and electrified1 remarkable effects follow3 but the phial must be very dry1 or warm4 ,i commonly rub it over before-hand with a finger1 on which ,i put some pounded chalk4--,if a little mercury or a few drops of spirit of wine are put into it1 the experiment succeeds the better4 ,as soon as this phial and nail are removed from the electrifying glass1 or the prime-conductor to which it hath been exposed is taken away1 it throws out a pencil of flame so long1 that with this burning machine in my hand1 ,i have taken above sixty steps in walking about my room4 ,when it is electrified strongly1 ,i can take it into another room1 and there fire spirits of wine with it4 ,if while it is electrifying ,i put my finger1 or a piece of gold which ,i hold in my hand1 to the nail1 ,i receive a shock which stuns my arms and shoulders40 8,a tin tube1 or a man1 placed upon electrics1 is electrified much stronger by this means1 than in the common way4--,when ,i present this phial and nail to a tin tube1 which ,i have1 fifteen inches long1 nothing but experience can make a person believe how strongly it is electrified4 ,two thin glasses have been broken by the shock of it40 ,footnote #h3 ,such is the statement usually given4 ,it may perhaps deserve consideration whether the cause of this luminous spark or stream1 should not1 strictly speaking1 be considered as the true electricity4 ,footnote #i3 ,tourmaline is a species of silicious earth4 ,its colour is generally a blackish brown1 though the tourmaline of ,brazil is blue1 green1 red1 or yellow4 ,it is a compound substance1 consisting of argill1 silex1 calcareous earth1 and iron in different proportions2 but argill and silex are always the chief ingredients4 ,it is found in ,ceylon1 ,brazil1 and ,tyrol2 and it is also found in large quantities in the neighbourhood of ,philadelphia1 attached to masses of quartz4 ,footnote #aj3 ,it is very remarkable that the focus of a burning glass is not a conductor of electricity4 ,footnote #aa3 ,we do not wish to be understood that two different fluids may be produced1 but merely1 that the prime conductor may be electrified positively or negatively4 ,footnote #ab3 ,for the proper cement1 see appendix ,,no4 ,i4 ,footnote #ac3 ,see appendix ,,no4 ,,ii4 ,footnote #ad3 ,see appendix ,,no4 ,,iii4 ,footnote #ae3 ,this consists of two small balls of cork or pith1 fastened to the ends of a thread or piece of silk4 ,when it is to be used the thread or silk must be held by the middle so that the balls may hang close to one another4 ,footnote #af3 ,mr4 ,richman1 professor at ,petersburg1 was killed on the #fth of ,august1 #agec1 by the lightning which he had drawn into his room1 for the purpose of making experiments4 ,the circumstances of this interesting and instructive occurrence were the following4 ,he had provided himself with an instrument for measuring the quantity of electricity communicated to his apparatus1 and as he stood with his head inclined towards it1 ,mr4 ,solokow1 an engraver1 who was near him1 observed a globe of blue fire as large as his fist1 jump from the instrument1 which was about a foot distant1 to ,mr4 ,richman's head4 ,the professor was instantly dead1 and ,mr4 ,solokow much hurt4 ,the latter however could not give any particular account of the way in which he was affected2 for at the time when he was struck1 there arose a sort of steam or vapour1 which entirely benumbed him1 and made him sink to the floor2 he did not even remember to have heard the clap of thunder1 which was very loud4--,the globe of fire was attended with an explosion like that of a pistol2 the instrument for measuring the electricity 7called by the professor the electrical gnomon7 was broken to pieces1 and the fragments scattered about the room4 ,upon examining the effects of the lightning in the chamber1 the door-case was split half through1 and the door torn off the hinges1 and thrown into the room4 ,they opened a vein in the body twice1 but no blood followed2 after which they endeavoured to recover life by violent friction1 but in vain3 upon turning the corpse with the face downwards1 during the friction1 a quantity of blood ran from the mouth4 ,there appeared a red spot upon the forehead1 from which spirted a few drops of blood from the pores1 without wounding the skin2 the shoe of the left foot was torn open1 and upon uncovering the part1 a blue mark was found2 from which it was concluded1 that the electric matter having entered at the head1 made its way out again at the foot4 ,upon the body1 particularly on the left side1 were several red and blue spots1 resembling leather shrunk by being burnt4 ,many more also became visible over the whole body1 and especially over the back4--,that on the forehead changed to a brownish red1 but the hair of the head was not singed4 ,in the place where the shoe was unripped1 the stocking was entire1 as was the coat every where2 the waistcoat being only singed at the fore flap where it joined the hinder2 but on ,mr4 ,solokow's coat there appeared long narrow stripes1 as if the nap had been burnt off by red hot wires4 ,these could not be accounted for4 ,footnote #ag3 ,this looks something like a contradiction3 but we suppose ,mr4 ,cavallo intended to say1 that though the coat of paint does not prevent the shock from passing down the mast1 it prevented the mast from being injured by the shock4 ,footnote #ah3 ,for proper cement1 see ,appendix to electricity1 ,no4 ,i4 ,footnote #ai3 ,the pile and trough1 are both sometimes denominated ,batteries4 ,footnote #bj3 ,volta by the aid of his condenser of electricity1 discovered that the two extremities of his pile were in opposite states2 the zinc end was always plus or positive1 and the silver end1 minus or negative4 ,footnote #ba3 ,this sub-acid taste1 is rendered much more distinct by an instrument invented by ,professor ,robinson1 and described by him in a letter to ,dr4 ,fowler1 dated #bhth ,may1 #agic4 ,it is made by placing alternately a number of small circular pieces of zinc1 with as many pieces of silver of the same size1 in the form of a rouleau4 ,it is to be used by placing it laterally upon the tongue4 ,footnote #bb3 ,with regard to the similarity between the taste of ,galvanism and that of electricity1 ,dr4 ,fowler observes that he found considerable difference between them--4 8,both 7says he7 are sub-acid1 but as unlike each other1 as the taste of vinegar is to that of diluted vitriolic acid40 ,this sensation1 produced upon the tongue by ,galvanism1 is most distinct when the tongue is of its usual temperature1 and the metals of the same temperature with it4 ,when either the tongue1 the metals1 or both1 are heated or cooled1 as far as can be borne without inconvenience1 scarcely any taste is produced4 ,footnote #bc3 ,this is the explanation given by ,mr4 ,wilkinson1 but we think it probable that this effect is altogether chemical4 ---------------------------------------- -------------------------------- ,,transcriber',s ,,notes ,typos fixed2 non-standard spelling and dialect retained4 ,used numbers for footnotes1 placing them all at the end of the last chapter4 ,enclosed italics font in underscores4