Εικόνες σελίδας
PDF
Ηλεκτρ. έκδοση

over the u, is always sounded like the simple g hard, as in the English words guest, guilt; as, guela, guitar ; pronounced gay'-tah, gee-lah. When the diceresis is over the M it is not mute, but has its proper sound; as, agiieh; pronounced ah-goo-ait-o, or ah-gtcay-lo.

G, before t or »', has always the guttural sound of the Spanish /,

H is never pronounced, but is always a silent letter; as, hact, higo; pronounced ah'-thay, ed-go.

J has always a guttural sound, somewhat like the English h in alcohol, strongly aspirated. But this is not an exact equivalent to the Spanish sound, which is produced by breathing strongly (as when one would give additional force to the A in host), and, by an effort of the palate, making the air gently strike the roof of the mouth.

It is the guttural sound of the ch in the German words nocht and night, and of the eh in the Scotch words loch, cloeh, and can therefore be learnt from any German or Scotchman. If we bend the tongue so as to form an arch which presses against the roof of the mouth, and produce a sound by breathing and lowering the tongue, this sound will be that of hard g, as it is called in English. If, again, we press the tongue against the roof of the mouth in the same way, and breathe forcibly without changing its position, we produce the exact guttural sound of the Spanish/. The learner must bear in mind that the sound of the Spanish g before e or »is the same guttural sound.

K is not used in Spanish, being found only in foreign words, when it is sounded like the same letter in English.

LL sounds like li in pavilion, or in million; as, silla, lloro; pronounced secl'-yah, logo.

As this sound seldom occurs in English, and never at the beginning of words, it requires some practice, for one accustomed to speak English only, to pronounce it readily in such Spanish words as llaga, liana, lltno, lloro.

\ sounds like ni in the English words onion, pinion; as, itoAa, iiono; pronounced non'-yah, nyon'yo.

This sound requires considerable practice before an English learner can pronounce it readily at the beginning of Spanish words such as nodes, nofto.

Q, which is always immediately followed by u, is sounded as in English; as, quanta, quota; pronounced ktoan'tah, kwa-tah.

QTJ, in the syllables que and qui, is sounded like k (that is, the u silent); as, quite, quite ; pronounced kay, kee-so; but if a diaeresis is over the u, the u has its proper Spanish sound; as, quetta; pronounced koo-ais'-tah or kweis'-tah.

R is sometimes sounded smooth as in English, and sometimes rough or trilling as with natives of Ireland. The rough sound is heard in Spanish when r begins a word, when doubled, and when it comes after /, n, or *; as, rabo, carro, alrota; pronounced r-rah'-bo, kar-r'-ro, al-r-ro'-tah. In every other position it has the English smooth sound.

The rough sound of r is made by vibrating the end of the tongue !.gainst.the roof of the mouth near the fore-teeth; it is seldom heard in English, though very easily acquired. The smooth (common English) sound is caused by a vibration of the tongue near the root, against the inward part of the palate, near the entrance of the throat.

S is always sounded as in the English words soon, this; as,

scdes; pronounced say'~dace.

The 8 in Spanish never has the sound of z as in English, in the words /his, lays.

T has nearly the same sound as in English. The only difference between the two languages, in pronouncing the t, 13, that in English the end of the tongue touches the roof of the mouth, and in Spanish it touches the upper teeth. In Spanish, therefore, t has a somewhat softer sound than in English.

V is pronounced is in English, with the sole exception that the upper teeth are not, pressed so strongly to the lower lip in enouncing this letter in Spanish.

It is a great mistake, which some grammarians have made, to Buppose that the Spanish sounds otjb and v are alike.

X has the sound of the English .tin the word tax; as, ezito, extreme, exacto; pronounced aiks-ei-to, aiks-tray-mo, aiks-ae'-to.

X, in Spanish, had formerly two very different sounds: the one the same as above given; the other a guttural sound, the same exactly as the Spanish/. To distinguish these sounds, the vowel following the x, when not guttural, had a circumflex accent over it; as, exucto, cxito. The guttural sound of the x is not at present used, or at least very seldom, in Spanish, as the letters j (before any vowel) and g (before e and i) have the same sound, and are now employed instead of the guttural x. Thus the words Mexico, Mejico, or Mexico, would, in Spanish, all be pronounced alike; though Mqico is the common spelling. It is of course no longer necessary to put a circumflex accent over the vowel following the x, when the letter has the English sound of lis, as it now has nearly always in recent Spanish writings.

Y, when a consonant, has the same sound in Spanish that it has in English in such words as young, year.

Y, when it stands alone, used as a copulative (meaning and), is pronounced like (. in see.

Z has always the sound of th in the English word think; as, svso; pronounced thoo-tho.

Remark.—There will be no difficulty on the part of the learner, who is his own instructor, in acquiring the sounds of the Spanish vowels and consonants, except the guttural sound of the j (which is also the sound of g before t on); and this sound can be learnt from any German, by hearing him pronounce eh in the words nacht and nicht; from an Irishman, by noticing the sound he gives ch in the word each, from a Scotchman in the word loch, or from a Welshman in the words bach, chwi. t

DIFFERENT METHODS OF SPELLING.

By the best Spanish writers i is used instead of y when this last letter is a vowel, and not at the end of a word. Thus regno, reyna, arraygar, are now spelt reino, rtma, arraigar.

Q is now used, by the best writers, only in the syllables que aud qui; as, gueja, quince. The syllables qua, que, qvi, and quo, are spelt with c. Thus quanda, qitttto, quota, are now spelled cum do, cuesto, cuota.

X is, by many of the best writers, never used before a consonant, its place being supplied by the letter s. Thus extenso, experts, are now often found spelt estenso, esperto.

In addition to the above remarks, it is proper to state that, by the best writers, s is never employed before e or i, its place being supplied wih e; thus ctro and cmco, for zero and zinco. X, too, is, by some few writers, always changed into M, when it comes before a vowel; thus secso, for scxo. The guttural sound of x, as has been already mentioned, is now seldom used; g or j being substituted for it.

Remark.—It is necessary to remember tnat the above variations in spelling produce no variations in pronunciation, except only when x before a consonant is changed into s, in which case s has its own regular sound; thus, estenso is pronounced ais-ten'-so.

A very little attention to the above directions will remove every difficulty which might otherwise occur in reading Spanish authors who do not adopt the same method of spelling. Thus, if the learner meet with such words as eelo,je'neros, rejistro, cuando, jahon, esceso, ecsactor, rtina, buitre, etc., and cannot find them in his dictionary, he must look for them under the other forms: zelo, gtncros, registro, qtiando, xabon, cxceso, exactor, reyna, buytre.

SOUND OF DIPHTHONGS AND TRIPHTHONGS.

The diphthongs and triphthongs in Spanish never contain any vowel sound different from those we have already given. When two or three vowels come together, they may be pronounced by a single effort or emission of the voice; but each vowel in Spanish continues to retain always its own particular sound, though the sounds glide into each other by being pronounced in the time of a single vowel. In the word rejoice, in English, the diphthong oi contains the sound of each of the letters to like 0 in not, and i like t in miss), yet, these

[graphic]
[ocr errors]

being pronounced rapidly and with a single impulse of the voice, the two vowel sounds glide into each other. It is thus that the Spanish diphthongs and triphthongs are sounded. Two vowels are never mingled into one and made to represent a sound foreign to each of them, as ou in the English word fought; or a sound in which only one is heard, as oo in boat. The diphthong ua, in the English word suavity, retains the sound of both vowels, being pronounced as if written sooa-vi-ty. The learner can judge from this example and the last syllable of the word rejoice, what is meant by each vowel retaining its own particular sound in diphthongs and triphthongs, though such a combination forms, of course, but one syllable. Thus in the Spanish word causa, the letters cau compose but one syllable, and the diphthong au is pronounced like a in bar and u in rude (the regular Spanish sounds of and u); and being uttered quickly, by a single impulse of the voice, the sound of au is similar to that of ow in the English word how, though not exactly the same.

Remark.—In order that the learner who has no instructor to teach him the sounds of the Spanish diphthongs , may not fail to acquire the right pronunciation, we again state that ail the vowels of a diphthong or triphthong, in Spanish, must be pronounced icith the regular sound of each, without any perceptible space between the different sounds which compose such diphthong or triphthong. Thus, in the diphthong of ea, the learner has already been taught that the sound of < is like that of e in the English word they, and the sound of a like a in are; all, therefore, that he has to do to form the diphthongal sound, is to unite these two sounds into one breathing or emission of voice. This he can learn to do by pronouncing quickly the words tlwy-are so as to form only one syllable, and the ey-a will be the exact sound of the Spanish diphthong tra. The letters ai or ay are to be pronounced together, as a in far and ( in «*; that is, as ay in bay would sound if the a had the sound of a in bar, and the y the sound of y in toy (not the mute y as in hay). And so with all the diphthongs and triphthongs.

List Of Diphthongs.

[table]
[ocr errors]

TBirHTHOXOS.

Mi has the sound of ce in eel, a in bar, and « in he: iei ,, ,, ee in ecl, e in they, and e in lie:

uai ,, ,, oo in mood, a in bar, and t in he:

uei, or uey, oo in mood, e in they, and e in he:

Remark.—Some of the diphthongs ending in »', will be found in some Spanish writings ending in as rema, reyna; builre, bitytre. The pronunciation in both cases is the same, and we have not increased the list by distinguishing those ending in i from those ending in v.

The two vowels, when they come together, do not always form one syllable (a diphthong). Thus the word idea, in Spanish and English, forms three syllables. In Spanish it is pronounced ee-dtiy-ah.

[blocks in formation]

lated with the vowel which comes after it; as, fit-so, d-no, ntd-i/o, hu-md-no, si-llun; except x; as, cx-tm-plo.

When two consonants come between two vo wels, the former is spelt with the preceding voweL and the latter with the succeeding vowel; as, por-Uil, cuer-po, es-te, i/t-tier-no. This rule' is subject to the following exception:

If the first of two consonants coming between two vowels be /, or any one of the mutes, and the second I or r, then both consonants are joined to the vowel by which they are succeeded; as, si-glo, suc-gro, co-bre, tri-dric-ro.

When two vowels of the same name come together, or two which do not form a diphthong, they are to be divided; as, le-er, co-or-di-ndr, oa-nv-a.

Componnd words are to be divided into their derivatives; as, pre-po-ntr, ad-jiin-to, con-flic-to.

When any one of the letters 4, I, m, n, or r, is followed by s and another consonant, or when « is preceded by any consonant, and succeeded by one or more, in compound words, the s is to be connected with the consonant which comes before it; as, Cons-tdn-za, cons-tre-nir, ins-pi-ray.

In Spanish there are as many syllables in a word as there are vowels or diphthongs; as, quin-ce, nor-te, pa-rien-te.

In English, the word quince forms only one syllable; in Spanish it is pronounced keen'-thay. Som-bre is pronounced om'-brey, and not om-bur, as it would be in English. Every letter in Spanish is pronounced except the h, and the u in the syllables gue, gut, and que, qui. There are no silent vowels or consonants, as in the English words thumb, throne, psalm.

ACCENT.

In the Spanish the voice never rests or prolongs itself on any other letter of a syllable than a vowel. When we speak of an accented syliable, we always mean thereby the vowel-sound of that syllable. In the oase of diphthongs and triphthongs, when in accented syllables, the accent or stress of voice is generally placed on that vowel which we have marked in the list of diphthongs and triphthongs. Thus, tie-ue having the accent on the first syllable, has the stress of the voice on the e of the diphthong, though the accent is not written over the vowel.

In words ending in cion, the accent is on the o and not on the t of the diphthong, as marked in the list; as, re-sur-reccion.

The rules of the Spanish accentuation are few and simple, and as follow:—

Words that end in a consonant are accented on the last syllable, without any marked accent over it; as, cola, cup; capaz, able; virtud, virtue; jardin, garden; saber, to know; earner, to eat; amar, to love; rigor, rigor; facilidad, facility. These are accented as if written ca-llz, vir-tud, co-mer, fa-ci-lidad, etc.

Words that end in a vowel are accented on the syllable next to the last, without any marked accent over it; as, rastro, track; hoja, leaf; builre, vulture; temperamento, temperature; ente, being;—accented as if written rds-tro, bia-tre, tem-pe-ramin-to, e'n-te, etc ,

Remark.—Words that end in two vowels, whether their vowels form a diphthong or two separate syllables, come under the above rule; as, estttdio, study; odio, hatred; opulencia, opulence; canoa, canoe; idea, idea; accented as if written 6-dio, o-pu-len-cia, ca-ni-a, i-de-a.

Words that end in a consonant and are accented on any other syllable than the last, or that end in a vowel (or diphthong), and are accented on any other than the syllable next to the last, have the accent marked to show the exception from the general rules; as, cdrcel, prison; cardcter, character; t iernes, Friday; virgen, virgin; or cafe, coffee: Idslima, pity; s'ilido, solid: matemdtico, mathematician; clausula, clause; accented on the syllable marked.

Remark.—Words that end in two vowels, which are commonly known as diphthongs, usually have the accent marked if it falls on one of these vowels: as fantasia, poesia, sefiorio, minue'. Words which end with y have the accent on the last syllable, without being marked.

4

In compound words there are a few exceptions to the above general rules. In adverbs of quality or manner ending in mente, some follow the general rule, and others retain the accent on the first part of the word, on the same syllable on which it would be if mente were not affixed; as, su-cin-la-mtn-tt, succinctly; li-bc-ral-nu-n-lc, liberally; bat-tdn-le-men-te, sufficiently; eifr-ta-men-te, certainly.

The plurals of words retain the accent on the same syllable (whether marked or not^ as in the singular; as, jardin, jardinet; caiiz, calicet; virgm, vtrgenet; clausula, clausula*. There are two exceptions to this remark, eardcUr and rigimen; their plurals being accented caracteret and regiments.

The above rules are applicable to all parts of speech except the persons of verbs; these are accented according to the following rules:

The persons of verbs whether they end in a consonant or a vowel, whether they are singular or plural, or to whatever mood or tense they belong, are accented on the syllable next to the last, without being marked; as, hablo, I speak; beben, they drink; hicitra, he would make. Infinitives, having no person, are not included in this rule, but are always accented on the last syllable.

In the case of the persons of verbs, whenever the accent does not fall on the syllable next to die last (as mentioned in the preceding rule), it is marked; as, cstd, he is; hablari, I shall speak; hablarun, they will speak; ami, I loved; /tabidbamos, we were speaking; hablariamos, wc would speak. The only exception to this rule is the second person plural of the imperative mood, and words ending in ay or oy, which are always accented on the last syllable, without the accent in general being marked; as, hablad, speak ye; haced, make ye; cstoy, I am. Some writers, however, place the accent over the last syllable, as, habldd, haced.

The accent is by many writers marked on certain monosyllables, to distinguish them from others of similar orthography and pronunciation but of different meaning; as, el, the, and el, he; sc, himself, and ei, I know, and se, be thou; si, if, and ii, to himself. The letters d, to; e, and; A, .or; u, or; are also generally used with a marked accent, though some writers omit it.

Throughout these lessons, every word which does not come under the three general rules of accentuation, will have the accent marked over the vowel upon which the stress of voice is to be laid. The learner must therefore bear in mind that every word which has not a marked accent over some vowel in it, is to be accented in pronouncing it, if it end in a consonant, on the last syllable; if it end in a vowel, on the syllable next the last. If the word be a verb, it is to be accented on the syllable next to the last, whether it end in a consonant or a vowel, except when it has a written accent over it, is in the infinitive mood, or in the second person plural of the imperative, or ends in y.*

PUNCTUATION.

The comma, semicolon, colon, period, etc., are the same, and are employed in the same manner as those in English. The marks of interrogation and exclamation are placed in Spanish both before and after interrogative and ejaculatory phrases or sentences; f as, i Este canape no esnuevot Is not this sofa new? j Que ceguedad! / I'obrc EtpaHa! What blindness! Poor Spain'.

The diceresis " is used over the u in the syllables gue, gut, que and gut, when the u is to be sounded, as agiiero; and also over the last of two vowels, which usually form a diphthong to show that they are to be divided into two syllables; as herdicidad, pronouaced ai-ro-ee-thee-ddd.

The tilde" is used over the « when this letter has the sound of ni in onton; as, dano.

The acute accent' is placed over vowels, not to alter their sound, but to indicate the syllable on which the stress of voice is laid in pronouncing certain words; as, drden.

• Tin learner will now be able to pronounco the names of the Spanisn letter*, of the alphabet, jiving to each letter its true Rpanish lonnd, according to'he preceding direction!:—a, be, ce, che. de, e, eft. ge. ache, i.jota, Jo, ele, elle, erne, ene, eite, o, pe, cu, erre, etc, le, u, ve, cqi.is, tgnei>a, tela.

* The leterrogation or exclamation mark coming first, being inverted

The circumflex accent was formerly used over a vowei following x, when this letter had not its guttural sound; as, texo; and over a vowel following ch, when the latter was pronounced as*/ as, chilo. But the alterations in orthography no longer require this mark.

ANSWERS TO CORRESPONDENTS.

In consequence of the limited space now left for the completion of the numerous subjects on hand, we shall be compelled in future to omit our usual Notices to Correspondents.

W. T. Stohhagb may learn the subjects for examination in classical honours at matriculation in 1855, by applying to Mr. R. W. Rothman, Registrar of the University of London.

John A. Carsb has solved all the problems in the second portion of the Second Centenary except four. Our solution of No. 39 requires no more algebraical Knowledge than he possesses. We cannot imagine what part of It occasions any difficulty. Is it where we say—

a-b- ("-»)* = (—^l
a a

It so, let him work out the point thus. Reducing to a common denominator, we have—

(o — i)a _ (a —pit = ta — 6) (n b) _ (a ipa

a a a a

O. M. Y.: We cannot pretend to give a better definition of an angle than the great geometrician Euclid. It may be popularly defined as the opening or space between two lines, and a pair of coaipasses or scissors may afford a clear illustration of its variation in magnitude. As they open more and more, thetangle between the legs of the compasses and the blades of the scissors increases, and it diminishes as they close. In geometry no angle is considered greater than 180 degrees or two right angles; but In trigonometry, the angle being defined to be the space passed over by a line revolving about a fixed line, may be of any magnitude whatever.

G. 8. Kuthxbfoed: We believe the terms lor the two years are £21, but you had better apply to Mr. Atkinson, the Secretary of University College. One year, in addition to the two, is sometimes allowed between matriculation and the 13 A. degree.

Catyenchlamius: There are many manuscripts of the classical Latin authors, though not original manuscripts. The Latin authors did not mark the quantity or omit urn before a vowel. The Italian style of writing was the first step to the modern mode, and consisted principally in joining the letters together. The differences between the versions in the Bible and tha Prayer-book arise from the fact that the translations were executed at different periods by different persons and from different originals. The Latin words prefixed to the Psalms In the Prayer-book are the commencements of the Vulgate version of the Psalms. Lit Is allowable as the past tense and participle of to Itght. Donkey Is usually pronounced as if written tlung-key.

LITERARY NOTICES.

Now ready, price 9t. 6d. strongly bound.

CASSBLL'S FRENCH AND ENGLISH DICTIONARY:

Composed from the French Dictionaries of the French Academy, Bescherelle, Landais, etc.; from the English Dictionaries of Ogilvie, Johnson, Webster, etc.; and from the Technological and Scientific Dictionaries of both Languages. By Professor De Lolmb and Hi.hrv Bhidqeman, Esq.

The following are the distinctive features which render this Work superior to any of the same class now extant. It has been compiled with unusual care from the very best authorities. It contains oorrtct renderings of all the most modern words and phrases—including those of science, art, manufacture, commerce, law, politics, etc., as well as familiar conversation—which are indispensable to a knowledge of language, but yet are rarely, if ever, to be found properly translated in any Dictionary. The idiomatic usages of the two languages—the constructions of verbs, the force of prepositions, and the changes of meaning caused by different combinations of words—are more copiously and carefully illustrated than elsewhere within the same limits. The meanings are also classified and arranged in such a manner as to prevent the possibility of mistake. To crown all, the Work is as moderate In price as it is comprehensive In aim, accurate in detail, and superior in arrangement. The French-English Division, price 4s. paper covers, or ■">-. neat cloth; the English-French Division, price 4s. paper covers, or 0.-. strongly bound.

Now ready, in Two Volumes, bound in cloth, Cs. each. THE HISTORICAL EDUCATOR. Tnla curious and interesting work contains the Travels and Discoveries of Uerodotui, Fausanius, and others, in Egypt, the East, Sec.; thu History of America, by Mary Howitt; the History of Greece, by J. Godkin, Esq.. complete Chronological Tables, etc. etc.; with a profusion of curious aiU unique Engravings.

ON PHYSICS, OK NATURAL PHILOSOPHY.

No. LVII.

(Continued from page 460.)

ELECTRICITY.

Nature and History of Electricity.—Electricity is a powerful physical agent, the presence of which is manifested by attraction and repulsion, by luminous appearances, by violent commotions, by chemical decompositions, and many other phenomena. The causes which develop electricity are friction, pressure, chemical action, heat, magnetism, and electricity itself.

Six hundred years before the Christian era, Thales, the great Greek philosopher, already observed the property by which yellow amber on being subject to friction attracts light bodies. In speaking of this substance, Pliny says: "When friction has given it the warmth of life, it attracts pieces of straw as the magnet attracts iron." But beyond this, the knowledge of the ancients in relation to electricity did not extend. It was not till the close of the sixteenth century that Gilbert, the physician to Queen Elizabeth, again called the attention of philosophers to the properties of yellow amber, by showing that many other substances might, by friction, acquire the power of attraction. The philosophers who since the time of Gilbert have more particularly contributed to the advance of this science are, Otho de Guericke, Dufoy, (Epinus, Coulomb, Franklin, Volt a, Davy, yErsted, Ampere, Schweigger, Seebek, De la Rive, Faraday, and Becquerel, to the last of whom we are indebted for almost all we know of electrical chemistry.

In spite of the numerous works upon electricity, we do not know the nature or origin of this powerful sgent. As in the eases of heat, light, and magnetism, philosophers are compelled to resort to mere hypothesis. Newton thought the production of electricity was the result of an etherial principle put in motion by the vibration of the particles composing bodies. The abbe Nollet inferred from the luminous and calorific effects of electricity, that it is a particular modification of he.it and light. Sy inner acknowledged the existence of two electric fluids, Franklin of only one.

Statical and Dytiamical Electricity.—Leaving all hypothesis out of consideration, the study of electricity is divided into two parts, the one comprehending the phenomena presented by statical electricity, or electricity in connexion with a state of rest, and the other those of dynamical electricity, or electricity in connexion with a state of motion. In a state of rest, electricity is chiefly produced by friction. It then accumulates at the surface of bodies, and is kept in equilibrium in a state of tension, which is manifested by attraction and sparks. In the dynamical state, electricity results principally from chemical action, and penetrates bodies under the form of a current with a rapidity like that of light. It is distinguished from statical electricity by chemical phenomena, and by its relations with magnetism. We shall first treat of statical electricity, considering more particularly that which is developed by friction, and we shall call a body electrised, when it possesses the property of attracting light bodies or producing luminous effects.

Development of Electricity by Friction.—Many substances on being rubbed with a piece of cloth or cat's skin, immediately acquire the property of attracting light bodies, such as the feathers of a quill or bits of straw. This property is particularly observable in yellow amber, sealing-wax, resin, sulphur, glass, silk, and many other substances. We ascertain that a body is electrised by means of small instruments called electroscopes, the most simple of which is the electric pendulum, fig. 378. This apparatus consists of a small pith ball hung by a Bilk thread to a support with glass feet. When an electrised body is brought near the ball, the latter is at first attracted, and then repelled immediately contact has taken place.

A solid body may also be electrised by friction with a liquid or gas. Friction does not always appear to develop electricity immediately. Some substances, particularly metals, may be rubbed for some time without any very perceptible effect, but still all substances are really electrised to some extent when placed in suitable conditions. The cause of the development of electricity by friction is unknown, though various theories have been propounded.

TOI.. T.

Conductors and Non-conductors.—On presenting a stick of Bealing-wax which has been rubbed at one end to the electrie pendulum, we find that only the part that has been rubbed exhibits any signs of attraction. It is the same with a glass tube and a stick of sulphur. Hence we conclude that the electric properties do not extend from one part of these bodies to another, which we express by saying that they do not con' duct electricity, or are bad conductors of electricity. On the contrary, experience shows that directly a metallic body has acquired electric properties in one part it extends over the whole surface of the body, whatever may be its magnitude, that is to say, metals are good conductors of electricity. The best conductors are metals, anthracite or stone-coal, blackFig. 378.

[graphic]

lead, coke, charcoal from well calcined wood, pyrites, galenn, and saline solutions—the conducting power of which last is many thousand times greater than that of metals—water in a state of vapour or liquid, the human body, vegetables, and all moist substances. The bad conductors are sulphur, resin, gum-lac, silk, glass, precious stones, charcoal not calcined, oils, and dry gases.

Isolating Bodies; Common Reservoir.—Bad conductors have received the name of isolating bodies or isolators, because they are employed as supports when we wish to make a conductor retain its electricity. This condition is indispensable, for the earth being composed of substances which conduct electricity, as soon as an electrised conductor comes into communication with it by means of another conductor, the electricity disappears in the earth, which on this account is called a common reservoir. A body is isolated by placing it upon glass legs, hanging it by silk cords, or placing it upon cakes of resin. But the worst conductors never completely isolate, the consequence of which is, that every electrised body always loses its electricity more or less slowly through the supports on which it rests. There is also a loss through the vapour in the atmosphere, which is usually the most operative cause of the loss ot electricity.

It is owing to the great power of conduction possessed by metals, that electricity cannot be obtained from them by friction, unless care is taken to rub them with a non-conducting body, as silk, or taffeta. But if this precaution is attended to, the metals may be electrised very well by friction. To prove this, fasten a yellow copper tube into a glass handle, fig. 379,

Fig. 379.

and, holding this last in the hand, rub the metallic tube with a piece of silk or taffeta, and then, on bringing it near the electric pendulum, attraction will be observed, showing that the metal is electrised. If the metal is held in the hand, there will still be electricity, but it will be immediately lost in the earth.

Two kinds of Electricity.—We have Been that on putting a glass tube, which has been rubbed with a piece of cloth, near the electric pendulum, there is attraction at first, and after*

135

van's repulsion immediately upon contact. The same effects are produced with a stick of sealing-wax rubbed in the same way. Hence it seems at first sight that the electricity developed in glass is the »ame as that developed in resin, but on pushing our investigations further, we find this is not the ease. In fact, the glass tube and the stick of resin having been electrised as we have said, if, while the electric pendulum is rei elled by the glass, we bring the resin near, this latter stroi gly attracts the ball of pith. In the same way, if to the pendulum, which is repelled by the resin immediately after contact, we present the glass tube, a strong attraction will be observed; that is to say, a body repelled by the electricity of the glass is attracted by the electricity of the resin, and reciprocally, a body repelled by the electricity of the resin is attracted by that of the glass. Upon the ground of these facts XJufoy, a French philosopher, in 1734 first asserted the existence of two kinds of electricity of different character; the one that which is developed in glass on being rubbed with wool, the otiier in resin or sealing-wax on rubbing them with a piece of cloth or cat's skin. The former is called vitreous electricity, the latter resinous electricity.

Theories of Symner and Franklin.—To explain the contrary effects presented by these two kinds of electricity, Symner, an English philosopher, maintained the existence of two electric fluids, each repelling itself and attracting the other. According to this philosopher, these fluids exist in a state of combination in all bodies, and thus constitute what is called the neutral or natural fluid. Various causes, especially friction and chemical action, suffice to separate them, and then electric phenomena appear; but these fluids have a strong tendency to reunite and :orm neutral fluid again.

The two electric fluids are called the vitreous and the resinous fluid. They are also called the positive and negative fluid, expressions borrowed from Franklin's theory. This philosopher, who acknowledged only one fluid repelling its own molecules and attracting those of material substances, considered that all bodies contain a determinate quantity of this fluid in a latent state. When it increases, the bodies are electrised positively, and possess the properties of vitreous electricity; when it diminishes, the bodies are electrised negatively, and possess the properties of resinons electricity. The term positive electricity or positive fluid are consequently equivalent to vitreous electricity, and negative electricity or negative fluid is equivalent to resinous electricity. Positive electricity is represented by the sign -\- (plus), as in Algebra, and negative electricity by — (minus). Symner's theory affords a simple explanation of many phenomena, and is therefore generally admitted in schools of science, at least in France. But it should not be forgotten that it is after all only an hypothesis. Besides, there is some vagueness about the term fluid as appled to the causes of heat, light, magnetism, and electricity. In fact, we may ask what is a fluid? and what is its nature ?— questions which no philosopher has yet satisfactorily answered.

We can only regard the hypothesis of two electric fluids as expressing two states in which electricity presents itself, under the aspect of two equal and contrary forces tending to produce equilibrium. The German philosophers generally acknowledge only one electric fluid.

Action of Eieetriscd Bodies upon one another.—Admitting the hypothesis of two kinds of electricity, the effects of attraction and repulsion which electrised bodies present are comprised in the enunciation of the following principle, which serves as a basis fur the theory of all the phenomena presented by statical electricity:—

Two bodies charged with the same elctricity repel, and two bodies charged with contrary electricity attract each other.

Law of Electrisation by Friction.—When two bodies of whatever nature are rubbed together, the neutral fluid of each is decomposed, and in all cases one of the bodies takes the poeitimc, emd the other the negative fluid. To prove this, communicate to the electric pendulum a known electricity, and bring the two bodies near it one afier the other, taking care to isolate them if they are conductors. Then one of the two will attract and the other reuel the pith ball, which proves that they are charged with contrary electricity. Further, they are also eharged with an equal quantity of each, for if we bring them near the pendulum while they are in contact,

attraction nor repulsion, which shows that the two kinds of electricity are in equilibrium. These experiments are generally made with glass discs, which are rubbed together briskly and then suddenly separated.

The electricity developed in a body by friction varies with the nature of the body rubbed. Ground glass rubbed with wool is electrised positively; glass not ground, on the contrary, when rubbed in the same way, is electrised negatively. The species of electrity developed depends upon the nature of the substance used in rubbing. The following substances are electrised positively when rubbed by those which come after them, and negatively when rubbed by those that precede them: cat's skin, ground glass, wool, feather, wood, paper, silk, gum lac, unground glass. The kind of electricity developed by friction also depends upon the degree of polish, the direction of the friction, and the temperature. If we rub together two pieces of glass one of which is more ground than the other, the former acquires positive and the latter negative electricity. If a piece of white silk riband be rubbed crosswise against another, the former is electrised positively and the latter negatively. If two substances of the same kind but of different temperatures be rubbed together, that which has the higher temperature is electrised negatively. In general it is bodies whose particles arc easily moved that are most easily electrised negatively.

Development of Electricity by Pressure and Splitting.—Gvpinua first established the development of electricity by pressure. Libes afterwards showed that by lightly pressing a metal disc, isolated by a glass handle, upon a wooden disc covered with

?uinmed taffetas, the metal disc becomes electrised negatively, laving demonstrated that Iceland spar is electrised positively on being pressed for a short time between the lingers, and that this crystal retains the electricity for several days, he discovered the same property in several mineral species, but M. Becquerel found that it belonged to all bodies, even conductors, provided they be isolated. Cork and india-rubber pressed against each other acquire electricity, the first positive and the second negative. M. Becquerel also observed that splitting, or the natural division of crystallised substances, may be a source of electricity. On splitting a piece of mica quickly in the dark, a feeble phosphoric light is observed. To prove that this phenomenon arises from electricity, M. Becquerel fastened each piece to a glass handle before separating them. He then suddenly separated ihem. and presented them to the electric pendulum, and found they possessed contrary electricity, laic in plates, and all bad conductors, are thus electrified by splitting. In general, whenever two particles are separated, each acquires a contrary electricity, unless the body to which they belong be a good conductor, for in that case the separation cannot be rapid enough to prevent the reunion of the two electricities. It is to the phenomena we have just described that we must refer the light which sugar gives out when broken in the dark

MEASURE OF ELECTRIC FORCES.

bodies is subject to the

the quantity of

Law of Electric Attraction < that twites place between following two laws :—

1. The repulsion and attraction hetu inversely as the square of the distance.

2. These forces are directly in proportion to electricity in the two bodies.

First Law.—These two laws were demonstrated by Coulomb by means of the torsion balance, which, as we have seen, is employed to demonstrate the laws of magnetic attraction and. |repulsion. The only modification necessary to be made in the balance in this case is, that instead of the magnetised needle suspended by the metallic thread, a stick of gum lac, with a small tinsel disc n at the end, rig. 380, is used, and instead of the vertical magnetised needle, a glass tube > with a copper ball m at the end. Fig. 380 exhibits several other modifications of fig. 382, but they are not necessary. For instance, the box is cylindrical instead of rectangular, the graduations are made round the sides of the box instead of at the bottom, and the micrometer is composed of a graduated disc e, which is moveable independently of the tube d, and of an index a, which) is fixed and serves to indicate through how many degrees

« ΠροηγούμενηΣυνέχεια »