« ΠροηγούμενηΣυνέχεια »
apparatus consists of a wooden stand, from the top of which the angle of torsion is inversely proportional to the fourth are suspended the rods or wires on which the experiments are powers of the diameters. made. “At their lower extremity is fixed a scale-pan for hold- Elasticity of Flexure.--All solids cut into thin laminæ or ing the weights used in determining the force of traction, and plates, and fixed at one of their extremities, when more or less two points A, B, are marked, between which the exact distance bent from their natural position, return to that position as soon is measured, by means of a cathetometer, before the scale-pan as the force which bent them is removed. This property is very
evident in tempered steel, caoutchouc, wood, and paper. Ceris loaded.
tain bodies can be bent only at a very small angle, unless they A cathetometer or vertical measurer, as the derivation from the be extended to a very great length, or be made extremely Greek implies, is a brass scale divided into inches and fractions thin. For example, glass cannot be bent unless it be formed of an inch, placed upon a stand which is brought exactly into of very thin laminæ about a foot in length, or be reduced to a the vertical position by adjusting screws at the bottom. On this very fire thread. In the latter state it becomes so flexible, scale there is placed a sliding telescope sight, exactly at right that it can be formed into waving plumes, or woven into angles to the vertical, which carries a vernier capable of cloth. measuring to fractions of an inch, each one hundredth part of the former. By fixing this telescope sight successively at the Numerous applications of the elasticity of torsion are to be points A and B, as seen in the figure, we obtain by means of seen in the construction of bows, cross-bows, watch-springs, the graduated scale the exact distance between these two carriage-springs, spring-balances, and dynamometers, or instrupoints. Now by loading the scale-pan with weights, and ments for measuring the intensity of forces, chiefly of animal again measuring the distance between the points A and B, we power. The elasticity of hair, wool, and feathers is employed ascertain the amount of elongation or extension arising from in the construction of mattresses, cushions, and other pieces of
domestic furniture. the traction of the weights.
By experiments conducted in this manner, it has been found Whatever may be the species of elasticity under consideraso long as the limit of elasticity has not been exceeded, that tion, as we have formerly remarked, there is always a limit to the traction or extension of rods and wires is regulated by the its action; that is, a degree of molecular displacement beyond three following laws :
which the elastic bodies are fractured, or rendered incapable Ist. Metal rods and wires have their elasticity of extension of reassuming their original form. Owing to several causes, perfect; that is, they resume exactly their original length as this limit is variable. For instance, the elasticity of several soon as the force of traction ceases.
metals is increased by hardening them; that is, by bringing 2nd. In the same substance, and having the same diameter, their particles more closely together, as in wire-àraving, the extension or elongation is proportional to the force of plate-rolling, or hammering. Some substances, as steel, traction and to the length.
cast iron, glass, &c., become more elastic and at the same time 3rd. In rods or wires of the same length and of the same harder by the process of tempering, which consists in cooling material, but of unequal diameter, the extensions or elonga- a metal suddenly after it has been raised to a high temperations are in the inverse ratio of the squares of the diameters.
Both calculation and experiment prove, that when bodies Elasticity, on the contrary, is diminished by the process of are extended by traction, their volume or bulk is increased. annealing, which consists in bringing bodies to a lower tempera
Elasticity of Torsion.--The laws of the torsion of metal wires ture than that required for tempering, and then slowly cooling und threads of various substances were first ascertained by them. It is by this process that the elasticity of springs is M. Coulomb, a French philosopher, who died in 1806. In his graduated at pleasure. researches on this subject he employed an apparatus called the In the operation of tempering, steel and cast iron acquire a balance of torsion; this is composed of a fine metallic wire or great degree of hardness, and it is chiefly for this purpose that thread, fastened to a stand at its upper extremity, and tempering is employed. All cutting instruments are made of stretched vertically by a weight, to the centre of which is tempered steel." But there are some bodies upon which temattached a horizontal pointer or index, Below this is placed pering produces an entirely opposite effect. Thus the combia graduated circle or dial-plate, attached to the stand by a nation of metals called tam-tan, which is composed of one part sliding piece and tangent-screw; the centre of this circle, which of tin to four parts of copper, becomes ductile and malleable is exactly under the centre of the index, is so adjusted as to when it is suddenly cooled ; on the contrary it becomes hard be exactly under the direction of the wire or thread produced and brittle like glass when slowly cooled. Salphur exhibits when it is in the vertical position. Now, if the index be the same phenomenon; when cooled slowly, it is hard and turned round, out of its position of equilibrium, by the amount brittle; but when cooled suddenly, it becomes soft and ductile of a certain angle, which is called the angle of torsion, the force like wax; but it does not continue in this state, necessary to put the index in this new position is called the
Glass presents a curious phenomenon of tempering in what force of torsion. When this turning round of the index takes are called Dutch tears or Prince Rupert's drops, names given to place, the particles of the wire or thread which were before small globules of glass, in the shape of tears, which in a state situated in the straight line parallel to its length or axis, are of fusion are dropped into cold water. Glass being a bad now situated in a spiral round it. If the limit of elasticity conductor of heat, the central parts of these globules are still has not been exceeded, the particles have a tendency to return in a state of fusion when the parts in contact with the water to their original position, and this tendency is verified by their have become solid. From this, it follows that their molecular actual return to it, as soon as the force of torsion is removed; forces being unable to resume the state of stable equilibrium, but they do not remain in this position. For, in consequence the globules become so brittle chat fracture at a single point of of their acquired velocity, they pass this position, and produce their surface is sufficient to make them burst in pieces with a torsion in a contrary direction; thus the equilibrium is again loud noise, and at once fall into powder. As glass undergoes disturbed, and the wire revolving now on itself, the index does the real process of tempering when too suddenly cooled, the not point to zero on the dial-plate until after a certain num- brittleness of newly-made articles is diminished by annealing ber of oscillations on both sides of this point.
them over a fire, from which they are very slowly withdrawn. By means of this apparatus Coulomb proved that when the
Tenacity is the resistance which bodies oppose to their amplitudes of the oscillations do not exceed a certain number extension by traction. In order to determine the amount of of degrees, these oscillations are regulated by the following this force in different bodies, they are formed into vylindric laws:
or prismatic rods, and subjected, in the direction of their Ist. They are very sensibly isochronous, that is, performed length, to the traction of a weight of so many pounds as are in equal times.
sufficient to determine the force of rupture or separation of 2nd. In the same wire the angle of torsion is proportional
their particles. to the force of torsion,
Tenacity is directly proportional to the force which produces i 3rd. In wires of the same diameter, and with the same force transverse section of the rods or prisms employed in resisting
the rupture, and inrersely proportional to the area of the of torsion, the angle of torsion is proportional to their length.
the strain. According to numerous experiments upon metals, , 4th. In wires of the same length, and with the same force, the force necessary to produce rupture is nearly triple of that
which corresponds to the limit of elasticity. Tenacity
Woods, * diminishes with the duration of traction. It is found that, Box,.. after a certain period, metallic and other rods give way under Ash.. smaller loads than those which would produce immediate Teak
7 rupture; and in all cases, the resistance of bodies to traction Beech
5 is less than their resistance to pressure.
Fir Tenacity varies not only in different bodies, but also in those
5 which are composed of the same matter, and in equal quantity
Pear according to their difference in form. In rods of equal sec
3 tional area, the prismatic form possesses less power of resistance
Elm than the cylindric. In a given quantity of matter, the hollow
White Deal cylinder possesses a greater power of resistance than the solid cylinder, and the maximum of tenacity in the former takes Ductility. This is a property which-many bodies possess, and place when the outer diameter is to the inner one in the ratio it consists in their power to change their form under various of 11 to
degrees of pressure or traction. In some bodies, as clay and In the same body, the form has the same influence on the wax, a very slight force is sufficient to produce a change in their resistance to pressure that it has on the resistance to traction. form; in others, as glass and rosin, it is necessary to add heat; Hence, a hollow cylinder, of equal matter and altitude, has a drawing, and laminating or reducing to plates. Ductility is
, as , greater power of resistance to pressure than a solid one; denominated malleability when it is produced by the operation whence it follows that the bones of animals, the feathers of of the hammer. The most malleable metal is lead; the most birds, the stalks of grass and of a great number of plants, being ductile in laminating is gold; and in wire-drawing, is platior traction than if they were solid, the mass of matter being produce wires of this metal not exceeding the thirty-thou
The great ductility of platinum enabled Wallaston to the same.
sandth part of an inch in diameter. This was effected by cover. Tenacity, as well as elasticity, varies in the same body ing a platinum wire of about one-hundredth of an inch in according to the direction in which force is applied. In wood, diameter with a coating of silver until the diameter of the for example, the tenacity and elasticity are greater in the compound wire was about of an inch in thickness ; then by direction of the fibres than in any crossing direction. This drawing this wire until its diameter was as fine as possible, the difference is, in general, manifested in all bodies whose contex- two metals were equally extended by the process; and lastly, ture is not the same in all directions. Yet M. Savart dis- by dipping the wire in nitric acid, the silver was dissolved corered, by means of ingenious experiments on the sonorous and the platinum wire remained, exhibiting the extraordivibrations of bodies, that in difference in this respect existed in nary degree of fineness above mentioned. A thousand yards of a number of bodies whose contexture was completely homo. this wire would weigh only about three-quarters of a grain; geneous; such as zinc, lead, brass, glass, resinous bodies, &c. and a quantity equal in bulk to a common die would reach He also discovered this difference in certain directions perpen- from London to Vienna. dicular to each other, which he called axes of stronger and Hardness.—This property of matter is the resistance which weaker elasticity. M. Sarart attributed this modification of bodies present to "scratching or abrasion by other bodies. these properties to a symmetrical arrangement which the This property is only relative, that is, a substance may be particles of bodies tend always to assume when they are slowly hard with reference to one body and soft with regard to cooled. It is of the greatest importance, in the arts of con- another. The relative hardness then consists in this, that one struction, to take into consideration the limits of the tenacity body can be made to scratch or abrade another without being and compressibility of materials. In suspension-bridges, for itself capable of being scratched or abraded by the other. The instance, the stability of the structure chiefly depends on the hardest of all bodies is the diamond, for it will scratch all tenacity of the reis which support the road-way. The follow. bodies, but cannot be scratched by any. After the diamond iny table exhibits the weights in tons on the square inch in hardness follow the sapphire, the ruby, the rock-crystal, which certain bodies can support in vertical traction before the flint, the stone, &c. Metals in a state of purity are generupiure, ur in other words, the limit of direct cohesion or rally soft. Lead can be scratched with the nail. The processes tenacity.
which increase their elasticity also increase their hardness; such
as tempering, annealing, &c. Alloys or mixtures are harder Metals,
W cights. than metals. Thus in jewellery and in coining, the hardness Jūrought iron wire, from it to go from 60 to 91 tons.
of gold and silver is increased by alloying them with copper. inch diameter
The hardness of bodies does not increase in proportion to Ditio, io inch diameter
their resistance to pressure. Glass and the diamond are much Wrought iron bars
harder than wood, but they present less resistance to the blow Ditto, haramered
of a hammer. The hardness of bodies is usefully employed in Wrought iron, rolled
from 14 to 18
polishing-powders, such as emery, pumice-stone, and tripoli. Wrought iron chains
The diamond, which is the hardest of all bodies, can only be Cast iron
ground or polished by means of a powder which is merely Cast steel
pulverized diamond. Iitto, tilted
CAS-HARDENING is a process by which the surface of artiSreel blistered and hammered
cles made of wrought iron is converted into steel. The articles Shar steel.....
to be case-hardened having been prepared in wrought iron, Pass steel
they are placed in an iron box in layers, in order to receive Damarcus steel.....
from 31 to 44
that degree of hardening on the surface which will prepare Coppei cast
them for receiving a final polish. A layer of animal carbon Copper hammered
(horns, hools, skins, or leather), at first so burned as to be Sheet copper
capable of reduction to powder, is spread over each; the box, Copper wire
then carefully covered and luted with an equal mixture of Platinum vire
clay a:id sand, is kept at a slight heat for half an hour, and its Silver wire
contents are then emptied into water. By this means, a surface Cast silver
of hardened steel is obtained over the whole of the article, of Gold wire
a thickness depending on the duration of the time in which Cast Gold
heat has been applied. This process is particularly applicable Brass
to articles wanting external hardness and polish, as fire-irons ; Gun metal...
6 44 60
but it is not applicable to cutting instruments, Tin wire..... Sheet lead, milled
* In the direction of their obres.
LESSONS IN ITALIAN GRAMMAR.NO. VII.
4. Cia, Cie, Cii, Cio, Ciu, Gia, Gie, Gii, Gio, Giu.
Blue bottle (plant)
The look, face
A mean fellow
Cup or glass
Ice, frost, cold
To kiss, salute
aht-tchóo-gahg Anchovy Cheto
Belly, paunch, body rah-kế-lai Rachele
lerr-tcho Archimede ahrr-kee-me-dai
I catch or snap
Royal palace fo-kai Foche
A Roman coin, July
jóo-leeo Fichi fée-kee
5. Gua, Gue, Gui, Guo, Qua, Que, Qui, Quo.
A Guelph, an ancient
coi . of Florence
I follow or pursue
Almost, as if
The Fowel i before e, when both follow the consonant c, are
pronounced as though the i was not there, and the whole combinaSucchio soók-keeo Auger, juice
tion only ce. The same remark, however, made with regard to Schiuma skeebo-mala Froth, scum
the combinations cia, cio, 'and ci-that in a more measured
enunciation the votel i in these cases is slightly touched3. Ga, Gle, Gio.f
holds good here also.
| The observation just made in the foregoing note with respect to Italian, Pronounced. English.
cie" is strictly applicable to the syllable gie. It is always pronounced Ghiaja gheeah-yah Gravel, sand
as though the i was not there; unless slightly touched in measured Ghiera gheeê-rah A ferrule
pronunciation. Ghiova gheeô-vah Clod, turf
$ No observation has yet been made in reference to the proRinghiare rin-gheekh-rai
nunciation of the double c (cc). This depends, as well as the Preghiera prai-gheeê-rali Prayer, desire
pronunciation of double g (99), on the vowel that follows the
latter c. If that vowel is a, 0, or u, the cc is sounded like a double Singhiozzo sin-gheeb-tso I Sob, sigh, hiccough
k (kk) or ck. For example, bocca (bók-kah), mouth; becco (bêk-ko), Cinghia
beak i accusare (ahli-koo-záh-rai), 10 accuse. If, howerer, that Unghie Oón-gheeai Nails, hoofs
vowel which follows the latter c is e ori, the double c (cc) is sounded Ringhio rín-gheeo Igrin, grinding the teeth something like tch in the English word match, only perhaps
stronger, and with vibration. On that account, I have tried to
imitate the stronger sound of the oc by the letters ttch, placing the * I have explained the combination chi to be soundeå like kee. first t in the first syllable, and tch at the beginning of the second, When one of the five vowels follows this syllable, it is so just as I have attempted to imitate the sound of the gg by placing intimately blended with the following vowel, 'that a kind of d in one syllable, and .j at the teginning of the next, in such words squeezed sound of chi is the result, the voice sliding, as it were, as paggi (páhd-jee), pages, attendants. The remark with respect from chi to the next vowel with great rapidity.
to the pronunciation of the gg, however, holds good of oc; the * The ,
voice must not pause too long on the t of the syllable where the lowed by any of the five vowels, is equally applicable to the first c occurs, and glide as quickly as possible to the pronunciation
of the second c, which must be very much vibrated. syllable ghi followed by a vowel : here, likewise, the syllable ghi is, a more equal distribution of the sound tch between the two sylla. as it were, squeezed, and the voice must slide into the pronuncia- üles will be effected, which will produce the correct sound of tion of the vowels that follow ghi with great rapidity.
the oc; and my imitation of that sound by ttch has no oiher object | The double zz, as well as the single %, may have the mild than to indicate to the reader the necessity of giving a stronger sound of the word adze (with which, by-che-bye, the ds in the word vibration to the cc. It is obvious that when cc is followed by conWindsor corresponds), or the hard sound of ts in Switzerland. sonants, it must be pronounced like ki, just as the single c in the According to modern orthography, the letter z is generally doubled like case must be so pronounced. For example, acclamare (ahkin the middle of words between tiro vowels, and the pronunciation klah-máh-rai), to elecí by acclamation, to applaud; accrescere (ahkof this zx scarcely differs from that of the single %. However, krái-shai-rai), to increase, &c. When between the cc and the before diphthongs, -as, for example, ia, ie, and i0,- must remain vowels e or i the letier h is interposed, the cc is also sounded like k, single, and has always, in such a case, the sharp sound. For as well as the single c in such cases and for the same reasons, the example, ringraziare (rin-grah-iseeá h-rai), to thank; pigrizia (nee- being a mere auxiliary letter to indicate that a before cand i is grée-tseeah), idleness; inezie (ee-ne-tseeni), follies; Bonifuzio (Bo- not to have the sound of itch, but of kk, as in chicchera (kík-kai-rah), nee-sáh-tseeo), Boniface.
a tea-cup; chiacchiera (keeáhk-keeai-rab), chit-chat.
In this way
ANSWERS TO CORRESPONDENTS.
CIVIS (Dublin): We recommend him to take up Part I. of the French
Lossons from the P, E. to follow the Lessons from the W. M. F. Part II. Segu(cz
sai-gwah-tchai Follower, disciple of the former will be ready in about three weeks. - AMBITION (CopthallInsegue in-sê-gwai
court) will see the studies that it will be necessary for him to take up Inguine in-gwee-nai Groin
if he wishes to matriculate at the University of London, in vol. ii. of the
P, E., p. 137.
EIPSELLIG (Leicester): Right-CARMONEY (Belfast) will see by the solu
tion we have inserted that his is wrong. Thanks for his other communicaLoquela lo-kwê-lah
Tongue, language tions.-SPEUDE BRADLOS (Fetter-lane): His conjecture about the Greek Aquila áh-qwee-lah Eagle
extract is right; but that about the Greek lesson is wrong. There is a very Aquoso
considerable difference between the ancient and the modern Greek. We beah-qwó-so Aqueous, watery
lieve that old Homer would not be understood in his own country.-.J. MILLS Lingua lín-gwah Tongue, language
(Tewkesbury): His poetry is good, but not -sufficiently measured ; that is, Sangue sáhn-gwai Blood
put into the proper number of syllables in each line; some lines have ten Pingui pín-gwee Fat, plump
syllables, some twelve, and so on. Vere we to correct it, we would begin
thus : Pasqua páh-skwah
“Ah, dost thou gaze upon that little child,
And smile with admiration at its form?
Scarcely as yet untolded, helpless thing,
What is there in its features so divine,
With which earth teems throughout her wide domain, 6. Cla, Cle, Cli, Clo, Clu, Gla, Gle, Gli, Glo, Glit.
Behold the sinallest insects far surpass,
Their microscopic organs how minute,
Their mechanique, how wonderfully fine!
But ah, within that infant form there lies
A soul divine ; a young immortal soul!
A soul of worth so infinitely great,
That all the powers 01 Mathematic lore
Its value cannot calculate or weigh. Cloto klô-to
Clotho, one of the Fates Clusio
A. RICHARDSON (Newcastle) and E, EVANS (Ashby-de-la-Zouch): We klor-zero Clusium, a town
regret that we cannot give them the information they require.-W. X. Gladio gláh-deeo* Knife, poniard
(Manchester) and PARALLAX: We advise them to write to Messrs. Watkins Glebar glê-bah Clod of earth
and Hill, 5, Charing-cross, London, who will furnish them with a catalogue Grifo Glyph (in architecture) of their telescopes, achromatic and
reflecting, with their sizes, porvers, Globo
and prices. They can also have information from the same tirm about magic glô-bo Globe
lanterns, sliders, and diagrams or atlases of the heavens. Gluina gloó-mah Chaff
C. B. C. (Hull) must study our Lessons in Penmanship, vol. ii., P. E.Reclamo tai-klah-mo Reclamation
T. MUXLOW (Sheffield): Get an old copy of Barrow's Euclid (which you may at any old book-stall for Is.), and you will see all the books of Euclid from the Ist to the 15th inclusive.-W. HADFIELD (Hayfield): We know of no paper in which excise vacancies are advertised.-W.J. OSBORNE (Soho): ive
think that the courtesy is due to any clergyman who does not wish his * This is the first occurrence in these lessons of the important sermon taken down in short-hand, to refrain froin so doing; he is the best combination gl. It has two different sounds. When it is not fol- judge of the value of his own productions.-J. ADDER (Grandtully): The lowed by the letter i it has the sound of gl in gland, glebe, glory, rule for finding the index of the quotient is this: Subtract the index of the
dividend from that of the divisor, and the reinainder is the index of the glue ; and this sound can offer no difficulty. But when the combination gl is followed by the letter i and one of the vowels a, e, o, quotient; now this being done for the first term in every step of the opera.
tion for finding the greatest common measure, there can be no difficulty at it is pronounced precisely as the double ? (11) in the French the end, for the remainder will take the indices of its terms from those words bouilli, fille, gresiller, grenouille, bouillon, billard, billet, brouillon, which correspond to them in the dividend, supposing them, of course, to be feuillu, and, generally speaking, in all those words where the ll has in arithmetical progression proceeding from that of the first term. after the vowel i a squeezed sound in the French language. They T. TAIT (Glasgow) should attend to the directions given in No.36, rol; who are unacquainted with French may form a notion of this ii.-N. P. P. should apply to the superintendent of the docks where he sound by separating and inverting the gl in the enunciation, i.t., by wishes to he admitted. W. R. E. (Gray's-inn-road) and A SUBSCRIBER pronouncing u before the g, and changing the latter into y. Only are informed that Mr. Cassell has published the very book they want, " The the first I must go to one syllable, and the second lalong with the People's Biographical Dictionary," compiled by Dr. Beard, and that it may
ve had at this office for 2s. 4d. in paper covers. The Atlas is progressing in y, and with a squeezed sound to the beginning of the next, while the P. E. Lord Byron swam the Hellespont. Don't bind the Magazine of care must be taken that the voice should glide rapidly from one Art," or any other periodical, too soon; sell your copy and buy another, syllable to the other, by which means a more equal distribution of taking more care next time.-J. BEWLEY (Langrigg): His verses are very the squeezed sound Uy will be produced, and a correct pronunciation good, but not up to our mark.A TROUBLESOME SUBSCRIBER will find an
"Latin wards," col. 2, p. 288, vol. ii., of the gl effected. An approximation to this sound may be found article on shell-cleaning in the P. E. in the English words million, miliary, biliury, billiards, seraglio, in should be " Latin words" certainly:-STUDENT OF ANGLESEA : In the pas:
“si cupis placere magistro," the "si" means only if;" cupis" means taglio, and oglio. The letter i, between the combination gl and the you desire, as shown by the termination“ is ; placere,” to please, accordvowels a, e, o, and u,
is (as well as in the combinations cia, cio, ciu, ing to the Latin idiom, requires the dative "magistro," to the master, to and gia, gro, giu) a mere auxiliary letter, i.e., a mere soundless, follow it; but we cannot literally say in English, to please to the master; written sigu, to indicate that.gl before a, e, o, and 2 is not to have yet, as to please means to give pleasure, we can say to give pleasure to the the sound of gl in gland, glebe, glory, and glue, but that squeezed master. Death would be the consequence of the stopping up the pores of sound, the imitation and description of which I have here besides being a great evil, is compensated for, in strong and healthy persons
great sin, attempted.
by copious and heavy perspiration, which literally washes the body itself,
and clears the pores for a time. Still this is an unhealthy state, and canno: For example : raglio (ráhl-lyo), a sieve ; meglio (mêl-lyo), better; be long continued with impunity.-CHEMICUS (Falkirk): Blr. Cassell is figlio (píl-lyo), I take, seize; miscuglio (mis-kool-lyo), mixture; about to publish a work on Botany. svegliare (zvel-lyáh-rai), to awake; togliere (tôl-lyai-rai), to také away; scegliere (shél-lyai-rai), to choose ; doglia (dol.lyah), sorrows bigliardo (čil-lyáhır-do), billiards; biglietto (bil-lyér-to), 'note, bill;
LITERARY NOTICES. imbroglione (im-brol-lyó-nai), a meddling fellow; fogliuto (fol-lyoóto), full of ieaves. Egli, he, egiino, they, quegli, that one, gli (the
GERJAY. plural of the article or the pronoun), with its numerous composi.
CASSELL'S GENDIAN PRONOUNCING DICTIONARY, in Nurnbers, 3d. each, tions, and gli, the final inflexion or terminational syllable of nouns
or Paris, ls, each. The entire work will be issued at 8s. 6d. in strong und verbs, hare always the squeezed sound llyee; while the mere atllablegi, at the commencement and in the middle of words, always CASSELL'S LESSONS IN GERMAN. Part I., price 25. in paper covers, or has the sound of gl in gland, glebe, &c. The only exception is 28. od neat cloth.
The only exception is 28. bd neat cloth. Part II. will shortly appear. Angli, Englishmen, pronounced áhn-glee. For example : figli
CASSELL'S LESSONS IN GERMAX PROXUNCIATION. Price Is. 6, in
paper (fil-lyee), sons; Jogli (fộl-lyee), leaves of paper; gigli (jí:-1pée), covers, or 23. neat cloth, will shortly be issued.
Cassell's ECLECTIC GERMAN READER, prices. in paper covers, of lilies; nogligerc (nai-gleé-jai-rai), to neglect; negligente (nai- 23. Ga. neat cloth. glee-jén-te), negligent; nejligenza (nai-glee-jên-tsah), negligenre; CASSELL'S ELEMENTS OF ARITHMETIC (uniform with Cassell's EUCLID) cegligentare (nai-glee-jeri-táh-rai), to neglect.
is now ready, price is, in stits covers, or Is. Gil, ncal clutuler, 3d,
ON PHYSICS OR NATURAL PHILOSOPHY
This plate is furnished with a funnel-pipe at R, by which the
water is admitted into the cylinder, and with an air-tight: No. VIII.
pump-body and piston, the latter being moved up or down by
means of a screw P. In the interior of the apparatus is con. HYDROSTATICS.
tained a glass reservoir A, filled with the liquid whose comThe Science of Liquids at Rest.-Hydrostatics is that part of pressibility is to be ascertained. This reservoir terminates in natural philosophy which has for its object the investigation
a bent capillary tube, the lower end of which is immersed in a of the conditions of equilibrium in liquids, and of the pressures mercurial bath at o. This tube is previously divided into which they produce, either in mass, or on the sides of the parts of equal capacity, it having been ascertained how many vessels which contain them. The science which treats of the of these parts the reservoir a contains ; this is found by deter: motion of liquids is called Hydrodynamics ; and the application mining the weight p of the mercury contained in the reserof its principles to the art of conveying and raising water is voir a, and the weight p of the mercury contained in a certain particularly denominated Hydraulics.
number n of the divisions of the capillary tube; then, denotGeneral Chrracter of Liquids.-It has been already stated the reservoir by n, we have the following proportion : P ::
ing the number of the divisions of the small tube contained in that liquids are bodies of which the particles, in consequence : N; whence, the value of N can be easily deduced. of their extreme mobility, yield to the slightest effort made to displace them. Their fluidity, however, is not perfect; for
In the interior of the cylinder is contained a Manometer among their particles there always exists an adherence which (rarity measurer) of compressed air. This is a glass tube B, constitutes a greater or less degree of viscosity (stickiness). closed at the upper extremity, and open at the lower extrethe gases; the distinction between liquids and gases being, the tube B is completely full of air; but when pressure is The fluidity of liquids is manifest
, but in a higher degree, in mity, which is also immersed in the mercurial bath 0. When
no pressure is applied to the water which fills the cylinder, that the former possess the property of compressibility in a very slight degree, whereas the latter are highly compressible and applied to the water in the cylinder, by means of the screw P elastic.
and the piston to which it is attached, this pressure is com: The fluidity of liquids is shown by the facility with which compressing the air contained in it.
municated to the mercury, which then rises in the tube B by
A graduated scale c, they take all kinds of shapes; their small compressibility is placed alongside of the tube, indicates the quantity by which proved by the following experiment.
the volume of air is diminished; it is by means of the quantity Compressibility of Liquids.-Subsequently to the experiment of diminution in the volume of air that the pressure on the of the academicians of Florence formerly mentioned, liquids liquid contained in the cylinder is determined, as will be were for a long time considered to be incompressible. After afterwards shown. wards, experiments were made on this subject, in England by Canton in 1761, and ly Perkins in 1819; at Copenhagen, by is first filled with the liquid wbose compressibility is to be
In making experiments with this apparatus, the reservoir A @rsted in 1823, and again by Colladon and Sturm in 1827. found; the cylinder is then filled with water by means of From these various experiments, it has been concluded as a the funnel-pipe R. The screw p is then turned so as to make fact that liquids are really compressible.
the piston descend and produce a pressure on the water and The apparatus empioyed in measuring the compressibility of the mercury contained in the cylinder ; this pressure not only liquids are called Piesoneters, that is (from the Greek), Pres. raises the mercury in the tube B, but also in the capillary tube sure-measurer's. The following is a description of that of Ersted, fastened to the reservoir A, as shown in the figure. The rise with the improvements of M. Dusprerz. This piesometer, fig. of the mercury in the capillary tube shows that the liquid con19, is composed of a very strong glass cylinder, about 35 inches tained in the reservoir has diminished in volume the measure
of its diminution being indicated on the tube itself, as above Fig. 19.
In his experiments, Ersted supposed that the capacity of the reservoir remained in variable, and that the sides of it were equally acted upon by the liquid both in the interior and on the exterior. Mathematical investigation has proved that this capacity is diminished by both pressures. In their experimenis, Colladon and Sturm took this change of capacity into account; and they have proved that for a pressure equal to that of the atmosphere, and at the temperature of 32° Fahrenheit, the parts of the original volume by which certain liquids were contracted, are as follows:Mercury..
.....000005 = vuoo Distilled water..
•000049 —9otos Ditto, freed from air
·000054 =13313 Sulphuric ether ......
000133 =265 They also observed that in the case of water and mercury, within certain limits, the diminution of volume is proportional to the pressure.
Principle of Equality of Pressure.- On the supposition that liquids are incompressible and possess perfect fluidity, and are freed from the action of gravity, the following principle, called the principle of equality of pressure in every direction, universally holds good : liquids communicate in all directions, with the same intensity, the pressures applied to any point of their
This principle was örst announced to the world by the celebrated Pascal, who died in 1662, and is sometimes called the principle of Pascal,
In order to have a proper idea of this principle, suppose a vessel, fig. 20, of any shape whatever, to be filled with water,
aud that in iis sides at different places cylindrical openings in diameter. This cylinder, which is completely filled with A, B, C, D, and E are made, to which there are applied moreable water, is terminated at the bottom by a wooden stand, in which pistons exactly fitting them. If to any, piston A, an external it is firmly cemented; and at the top a copper cylinder is fixed pressure be applied, say of 20 pounds this pressure is instar to it, by means of a p.ate, which can be unscrewed at pleasure. I taneously communicated to the internal surfaces of the pistons