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London.

Lodgate-hill

rrited and poblished 6 JONN CARRIL

bon which is converted directly into carbonic acid, disengages ON PHYSICS, OR NATURAL PHILOSOPHY. the same quantity of heat as if it were first converted into No. XLIII.

carbonic oxide, and then the latter into carbonic acid.

The heat produced by a burning body is distributed in two (Continued from page 242.)

ways; first, by the calorific rays which proceed directly from SOURCES OF HEA T.

the body; secondly, by the heat which the particles, after

being converted into carbonic acid, carry along with them, CHEMICAL SOURCES.

when drawn up by a current of air. By the latter way, a very Chemical Combinations.-Chemical combinations are gene ascertained by any one by means of a very simple experiment,

considerable proportion of the heat escapes, as may be easily
rally accompanied by a development of heat more or less abund- shown in fig. 229. Thus, we find that we can hold the finger
ant according to the nature of the substances. When these
combinations operate slowly, as when iron is oxidised in the

Fig. 229.
air, the heat developed is insensible; but when they are pro.
duced rapidly, as in the mixture of anhydrous sulphuric acid
with water, the disengagement is very intense. In most
cases, this disengagement of heat is accompanied with com-
bustion,

Combustion. Every chemical combination which is accom-
panied with the development of light and heat, is called com-
bustion. In the combustions presented to us by wood-fires,
oil-lamps, and wax-candles, it is the carbon and the hydrogen
of the wood, the oil, and the wax, which are combined with
the oxygen of the air. But there are combustions in which
oxygen plays no part. For example, if into a vessel full of or thumb at a small distance from the side of the flame of a
chlorine, we throw some powder of antimony, or, pieces of lighted candle, without feeling the heat too intense to bear its
phosphorus, these bodies will combine with the chlorine and action ; but when we hold the finger abore the tlame, in the
produce a powerful development of light and heat. Several direction of its axis, we are forced, by the greater heat evolved
combustibles burn with a Hame. A flame is, in fact, only a in this direction, to remove it to a much greater distance.
gas or a vapour carried to a high temperature by the effect of
combustion. Its illuminating power varies with the products

ILLUMINATION.
which are formed during combustion. The presence of a solid Modes of Lighting.--As the method of producing an artificial
body in a flame increases its illuminating power. The flames light for the purpose of supplying the want of the light of the
of hydrogen, carbonic oxide, and alcohol, are pale, because sun, is more connected with the principles of flame, combus-
they only give out gaseous products. But the flames of wax- tion, and heat, than with light considered by itself, we shall
candles, oil-lamps, and carburetted hydrogen gas, have a great treat here shortly on this subject. The light of a common fire
power of illumination, because they contain an excess of car-

was naturally the first step in the art of illumination. The bon, which, undergoing only an incomplete combustion, property which resinous woods possess of giving out a flame become incandescent in the flame. Much greater intensity is not only continued difficult to estinguish, but soon led to given to a fame, by placing in it platinum wire or amianthus their use in the form of torches. Virgil speaks of them in the The temperature of a fame has no specific ratio to its illumi- 2nd book of the Georgics, and in the 7th book of the Eneid. nating power. The flame of hydrogen, which is the palest, is

“ Ipsa inter medias fagrantem fervida pinum
that which developes the greatest heat.

Sustinet."
Heat of Combustion.-Several philosophers, among whom
may be mentioned Lavoisier, Rumford, Dulong, MM. Despretz

This mode of lighting is still used in some countries to this and Hess, have been engaged with researches relating to the day, as in Corsica and in China ; but on account of the synoke quantity of heat developed by different bodies during com- it can only be employed in the open air. The inflammability bustion and combination. In these researches, the calorimeter of oily bodies, and especially of animal fat, must have been of Rumford was employed. It consists of a rectangular copper discovered in the practice of the most simple culinary preparathrough the bottom of the vessel and terminating below in an resinous matter for the branches which contain it, the extracbodies on which the experiments are made. The products of progress of the art of illumination. Resinous matter, solid combustion, by being

disengaged in the worm, heat the water grease and wax fixed round a wick composed of fibrous matter, in the vessel, and after the elevation

of its temperature, the gave rise successively to the torch, the candle, and the wax: quantity of caloric developed may be determined. Assuming light. Oil

, extracted either from animal or vegetable matter, as the unit of heat, the quantity of caloric necessary to raise was burned in lamps, which were at first small vessels fur: one kilogramme of water by 1. Centigrade, Dulong found nished with a hollow beak or spout, in which the wick was that a kilogramme of the substances in the following table placed. In all these cases, whether lamp, candle, or torch, disengaged in their combustion the number of units placed

in the combustible matter melted by the heat, rose in the wick in a line with their names :

consequence of capillary action, as formerly explained. Small

resinous torches, manufactured from the products of the pinus Substances.

Units.

maritima, on a large scale in the moors of Gascony, are still, in

34600 many parts of France, the only mode of lighting employed Protocarburetted hydrogen

13205

during the long nights of winter. The gaseous protlucts of the Bicarburetted hydrogen

12032

combustion are carried off by the chimney, under the mantel. 10836

piece of which the torches are placed. The unhealthy candle,

9862 compared with this imperfect light, was a vast improvement. Sulphuric ether

9430

But the candle is beginning io disappear in our towns, in order 7295

to give place to the stearic wax-lights, which are only half Alcohol

6855

the price of the real wax-lights, and have an equally pure Sulphur

2601

smeli. The modern lamp, successively modified by Argand, Carbonic oxide

2488

Carcel, and others, has only a very distant resemblance to the

lamps of antiquity. Whatever be the substance used in the The experiments of Dulong, M. Despretz, and M. Hess, production of the light, the flame, which is the illuminating always the same quantity of heat in order to arrive at the charged with solid particles. This will be explained by tig. iamme degree of oxidation, whether this degree be reached 230, in which a A is a vertical section of a candle through the immediately or by degrees. For example, a quantity of car-uniddle. BB, is the cotton wick which is set on fire." The

121

Hydrogen

Oil of turpentine
Olive oil

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...

Pure carbon

...

[ocr errors]

VOL. Y.

about painting fans to procure a morsel to maintain his mother this subject, I can be seen at any time after six o'clock, evening. and the rest of the family, He afterwards went to Italy and I take in the three Educators (Popular, Biblical, and Historical), Athens, where he became truly celebrated; and was subsequently because I think it better to take them in as they come out; for it appointed Surveyor of Greenwich Hospital. He is, by way of I let them pass, they would amount to more money than I could eminence, called the Athenian Stuart.

afford to raise at once, I give you my name to use as you choose, Terence, the poor African slave, became a famous dramatic as I hope you will oblige your humble servant, writer; and is as remarkable for his spirit of gratitude towards his

DAVID KNIGHT. generous liberator as for his shining talents. See, young reader, June 19th, 1854. No. 3, Nelson-square, what even barbarous Africa can produce.

Monkwearmouth, Sunderland. Nicholas Reymanus, the great Dutch mathematician, was, in

[We have inserted the above letter as a fair specimen of many early life, a swineherd, and was eighteen years of age before he that we have received since we commenced our labours; and these learned to read; but so incessant was his labour, and so rapid his labours have been nobly appreciated, and wisely appropriated, by progress, that he afterwards taught mathematics at Strasburg; many thousands of our working population-our country's wealth, obtained a professorship at Prague, and became such a master of stability, and pride. We hope that our correspondent will meet science as to dispute with the famous astronomer Tycho Brahe, with many in the town and suburbs of Sunderland who will answer concerning the right to some astronomical discovery.

his invitation. Such a man, by simple means such as he has proCervantes, the celebrated Spanish writer, and author of " Don posed, may do a vast amount of good in his day and generation. Quixote," a powerful satire on the books and the profession of -ED.) knight-erraniry, was a common soldier, and lost his arm at the battle of Leputa. Here I pause; and, reader, talk as you will about the force of genius in those men, you may rest assured that the spirit of indomitable perseverance led them on through every

ANSWERS TO CORRESPONDENTS. difficulty. An eminent writer, giving advice to a young student, says : -"Live like a hermit, work like a slave, learn everything, 1. D. (Brighton? Yes.-M. E. L. (Borougb: Tour hand-writing is good,

1. O. U. (Liverpool) has not seen the 2nd and 3rd vols. of the P. E,and shun popular pleasure.

"If one hour you dedicate to reading, give two to reflection, and and well adapted for an amanuensis. Good spelling and composition are three to observation. Deem no art or science useless. Accustom you if an opportunity should occur ; but opportunities are rare.-A. HARDyourselves to act as well as to think.

ASAN (Manchester) is right.-W. MARTIN (New Swindon); D. H. S. (Liu“Confirm reading by practice, and improve practice by reading. colashire); W. A. (Woolwich); F. 1. B. (Halifax); A.'BOYD (Glasgow); Store your mind with all sorts of knowledge ; you never know !:,!., Snowdon (Odley); MARIA M. LEATH (Otley); and J. RUSSELL when it will be required; even that which is most useless will Chislehurst): All right about the Plac-tree and the Lady's age.-L. R. J. always prove ornamental. For methods, make your own,

adapt those cost 45, Gd. each, or two vols. in one, 8.. 6d. The English and French are which you find most apt; experience in this will be the best the most useful languages in a place of business like Manchester. Righe in teacher, your own habits the best adviser. There is no royal the Lady's age.-A. GEARING (Leamington): His expression for the circumroad to knowledge, and but one golden rule, and that is mental terence of the circle is pretty fair, but it is correct

orly to the figures 3:1 415, labour, work, work, work."

the next figure being zero instead of 9.-J. F. ATKINSON (Birkby): We Here, readers, is an extract worthy of your attention, for before shall be glad to see his solutions, believing them to be done bona fide.the powers of application every thing must bend. You have -J. LONBY (Armagh) : See the scholastic advertiseinents in the Times" difficulties to contend with, so has every one; but the giant might newspaper.-E. SUTTON (Retford) had better call when in town.-N. M. L. of rational resolve scarcely admits of any.

(Torienham-court-road): None at present.-BLANDUS: Right in the Lady's Chevenix, on National Character, says ;-" The most advanta. age. The Hebrew may be the oldest, but it is not the easiest language. geous situations in which human beings can be placed is, that in You

cannot learn or understand the Hebrew without the points;

there is which they are surrounded by superable obstacles.'

no fashion in the matter; it is a question of pure necessity.- J. JONES

(Woolwich): Kis solution of the Pino-tree question is good.-UNE AMIE AU And now, fellow-studenis, I'must bid you good-bye for the present, P. E. (Leicester): Many thanks for her communication and kind wishes.hoping soon to meet you again on the educational arena of the Joux Pouson (slossley):

His solutions received. Poprian EDUCATOR; and, my boys, let those who will take volo non voleo for their motto; ours must undoubtedly be Ne cede malis sed contra audentior ito, shining in relievo on our escutcheons.

LITERARY NOTICES. I am, Mr. Editor, with the warmest feelings of respect and gratitude, one of your humble students,

H. H. ULIDIA.

Now Ready, Katesbridge, June 15th, 1854. [There is so much of good feeling and good sense, as well as of

CASSELL'S FRENCH AND ENGLISH DICTIONARY: the perfervidum ingenium Scotorum, in this letter, that we could not composed from the French Dictionaries of the French Academy, Bescherelle, resuse it a place; especially as it urges our students to persever. Landais, etc.; from the English Dictionaries of Ogilvie, Johnson, Webster, ance in a more lively strain than we are likely to do, were we to etc.; and from the Technological and Scientific Dictionaries of both Lantake up the pen. At the same time, coming from a fellow-student guages: (who has given us his name and address), it is more likely to have a

The following are the distinctive features which render this work superior good effect on some of our undecided readers. Ed.]

to any of the same class now extant. It has been compiled with yousual care from the very best authorities. It contains correct renderings of all the

most modern words and phrases—including those of science, art, manufacSELF-EDUCATION AND MUTUAL INSTRUCTION. ture, commerce, law, politica, etc., as weli as familiar conversation-which

are indispensable to a knowledge of language, but yet are rarely, if ever, lo SIR, -About the time you commenced your laborious work, it be found properly translated in any Dictionary. I'Le idiomatic usages of happened, by chance, that I was passing a booksellers's shop win the two languages-the constructions of verbs, the force of prepositions, and dow, and saw there the third number of the Popular EDUCATOR. the changes of meaning caused by different combinations of words-are I read all that I could see,—“On the Influence of Morality and limits. The meanings are also classified and arranged in such a manner as

more copiously and carefully illustrated than elsewhere within the same Immorality on the Countenance.". I looked to see the price of it, to prevent the

possibility of mlstake. To crown all the work is as moderate and found that it was a penny; that sum being all I had in my in price as it is comprehensive in aim, accurate in detail, and superior in pocket, I purchased it. I then took out my pen-knife and cut arrangement. Price 98.6d. strongly bound. open the leaves, in order to finish what I had read through the CASSELL'S LESSONS IN FRENCH. Parts I. and 11.-By Professor Fase windows. To my great surprise, I found Dr. Beard's Lessons in

Quelle. Price 2s. each in paper covers, or 22.6d, bound in cloth. The Larin. I then turned over another leaf, and found Lessons in Two Parts bound in One Volume, price 13. 6. Arithmetic; and then next, I found Lessons in English; the Exercises. Price 1s. paper covers, or Is. 6d. cloth.

A key to CASSELL'S LESSONS IN FRENCH, containing Translations of all and it gave me great pleasure to think that such a work

A COMPLETE MANUAL OF THE FRENCH LANGUAGE.-By Professor DE was to be had at so low a price. I have continued to take it in LOLMg. Price 3s. neatly bound. ever since, up to the present time. I then commenced the study Reprinted in a revised fo rm irom The Working Man's Friend." Price 6d.,

A SKIES OF LESSONS IN FRENCH, on an entirely Novel and Simple Plan. of the Lessons given in Arithmetic, which has improved me so much, that I have got as far as Simple Interest with wonderful by post 74. Above 30.000 copies of this work have been sold.

CASSELL'S LATIN DICTIONARY. Buccess. Before I saw the POPULAR EDUCATOR, I knew nothing | 2. English and Latin. By J. R. BEARD, D.D., and C. Beard, B.A. To

In Two Parts:-1. Latin and English, about arithmetic; I had got so far as Compound Proportion, but Weekly Numbers, 3d. each, and Monthly Parts, 1s.

The First Four in such a wretched state, that I could not master it. Now, bir, Monthly Parts are now reads, as also the First Sixteen Numbers. there is no Co-instruction Society at Sunderland, as yet, that i The Latin-English Division is now ready, price 18. in paper covers, 68. knoň of; but there are a great many who take in the POPULAR in cloth. EDUCATOR, and a great many more who would like to do so, and

Now Ready, to have a good education. If you can do anything to draw us CASSELL'S GERMAN PRONOUNCING DICTIONARY. together, I will give you my address, and will do all that I can In Two Parts :-). German and English ; 2. English and German. la for any one that calls on me; if there be any wishful to see me on one large handsome Octavo Volume, price 98. strongly bound.

Printed and published & Jown CARIRLL. Ludgato-bill London,

bon which is converted directly into carbonic acid, disengages ON PHYSICS, OR NATURAL PHILOSOPHY. the same quantity of heat as if it were first converted into No. XLIII.

carbonic oxide, and then the latter into carbonic acid.

The heat produced by a burning body is distributed in two (Continued from page 242.)

ways ; first, by the calorific rays which proceed directly from SOURCES OF HE A T.

the body; secondly, by the heat which the particles, after

being converted into carbonic acid, carry along with them, CHEMICAL SOURCES.

when drawn up by a current of air. By the latter way, a very Chemical Combinations.-Chemical combinations are gene- ascertained by any one by means of a very simple experiment,

considerable proportion of the heat escapes, as may be easily
rally accompanied by a development of heat more or less abund-
ant according to the nature of the substances. When these shown in fig. 229. Thus, we find that we can hold the finger
combinations operate slowly, as when iron is oxidised in the

Fig. 229.
air, the heat developed is insensible; but when they are pro-
duced rapidly, as in the mixture of anhydrous sulphuric acid
with water, the disengagement is very intense.

In most
cases, this disengagement of heat is accompanied with com-
bustion.

Combustion.—Every chemical combination which is accompanied with the development of light and heat, is called combustion. In the combustions presented to us by wood-fires, oil-lamps, and wax-candles, it is the carbon and the hydrogen of the wood, the oil, and the wax, which are combined with the oxygen of the air, But there are combustions in which oxygen plays no part. For example, if into a vessel full of

or thumb at small distance from the side of the flame of a
chlorine, we throw some powder of antimony, or pieces of lighted candle, without feeling the heat too intense to bear its
phosphorus, these bodies will combine Mith the chlorine and action ; but when we hold the finger abore the tame, in the
produce a powerful development of light and heat. Several direction of its axis, we are forced, by the greater heat evolved
combustibles burn with a Hame. A flame is, in fact, only a in this direction, to remove it to a much greater distance.
gas or a vapour carried a high temperature by the effect of

ILLUMINATION.
combustion. Its illuminating power varies with the products
which are formed during combustion. The presence of a solid

Modes of Lighting.--As the method of producing an artificial body in a flame increases its illuminating power. The flames light for the purpose of supplying the want of the light of the of hydrogen, carbonic oxide, and alcohol, are pale, because sun, is more connected with the principles of tame, combus. they only give out gaseous products. But the fames of wax. tion, and heat, than with light considered by itself, we shall candles, oil-lamps, and carburetted hydrogen gas, have a great treat here shortly on this subject. The light of a common fire power of illumination, because they contain an excess of car

was naturally the first step in the art of illumination. The bon, which, undergoing only an incomplete combustion, property which resinous woods possess of giving out a flame become incandescent in the flame. Much greater intensity is not only continued difficult to extinguish, but soon led to giren to a fame, by placing in it platinum wire or amianthus their use in the form of torches. Virgil speaks of them in the The temperature of a flame has no specific ratio to its illumi- 2nd book of the Georgics, and in the 7th book of the Eneid. nating power. The Aame of hydrogen, which is the palest, is

“ Ipsa inter medias flagrantem fervida pinum
that which developes the greatest heat.

Sustinet."
Heat of Combustion --Several philosophers, among whom
may be mentioned Lavoisier, Rumford, Dulong, MM. Despretz

This mode of lighting is still used in some countries to this and Hess, have been engaged with researches relating to the day, as in Corsica

and in China ; but on account of the sinoke quantity of heat developed by different bodies during com- it can only be employed in the open air. The inflammability bustion and combination. In these researches, the calorimeter of oily bodies, and especially of animal fat, must have been of Rumford was employed. It consists of a rectangular copper tions in the remotest times. The substitution of the pure

discovered in the practice of the most simple culinary preparathrough the bottom of the vessel and terminating below in an resinous matter for the branches which contain it, the extracinverted funnel. Under this funnel are placed the burning tion of animal fat and vegetable oil, were grand steps in the bodies on which the experiments are made. The products of progress of the art of illumination. Resinous matter, solid combustion, by being

disengaged in the worm, heat the water grease and wax fixed round a wick composed of fibrous matter, in the vessel, and after the elevation of its temperature, the gave rise successively to the torch, the candle, and the wax: quantity of caloric developed may be determined. Assuming light,

Oil, extracted either from animal or vegetable matter, as the unit of heat, the quantity of caloric necessary to raise was burned in lamps, which were at first small vessels fur: one kilogramme of water by 1° Centigrade, Dulong

found nished with a hollow beak or spout, in which the wick was that a kilogramme of the substances in the following table placed. In all these cases, whether lamp, candle, or torch, disengaged in their combustion the number of units placed

in the combustible matter melted by the heat, rose in the wick in a line with their names:

consequence of capillary action, as formerly explained. Small

resinous torches, manufactured from the products of the pinus Substances.

Units.

maritima, on a large scale in the moors of Gascony, are still, in Hydrogen

34600 many parts of France, the only mode of lighting employed Protocarburetted hydrogen

13205 during the long nights of winter. The gaseous protlucts of the Bicarburetted hydrogen

12032 combustion are carried off by the chimney, under the mantel

10836 piece of which the torches are placed. The unhealthy candle, Olive oil

9862

compared with this imperfect light, was a vast improvement, Sulphuric ether

9430

But the candle is beginning to disappear in our towns, in order Pure carbon

7295 to give place to the stearic wax-lights, which are only half Alcohol

6856

the price of the real wax-lights, and have an equally pure 2601

smeli. The modern lamp, successively modified by Argand, Carbonic oxide

2488

Carcel, and others, has only a very distant resemblance to the

lamps of antiquity. Whatever be the substance used in the The experiments of Dulong, M. Despretz, and M. Hess, production of the light, the flame, which is the illuminating always the same quantity of heat in order to urrive at the charged with solid particles. This will be explained by tig. same degree of oxidation, whether this degree be reached 230, in wbich a A is a vertical section of a candle through the

or by degrees. For example, a quantity of car-widdle. BB, is the cotton wick which is set on fire. The VOL. Y.

121

...

Oil of turpentine

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Sulphur

...

[ocr errors]

...

immediately

width of the cylindric rail oftalw? been called in such! The srt trarsrerse or horizontal marks, represent the a proportion to that uit he wiss, this is not mel, pita cheuped by the particles of oxygen; the round points but torm a wall with hinders te mirnater frou guzter in the near y rerical les, represent the place occupied by ing. Thus the nucited grease is endas di were in a smui che parties of hydrogen. It is quite evident that the most cup, represented at ce, and turns a bath of a sutient depth active combination takes place in the exterior part, where the

parteles ot boca gases are in immediate contact; and that it gees oa diminishing from the border to the centre of the flame, where there is none. What the candle, the wax-light, and the lamp realise on the small scale, and simultaneously with the process of combustion, has been effected on the great scale, and previous y to combustion itself; in other words, we extract the carburetted hydrogen gas from the bodies which coutain is, and we burn it by means of gas-burners properly surpleri with it. This invention is entirely a modern one. Vtwiths anling the ultimate resemblance which exists in all Shese varui modes of illumination, there are particulars belonging to each worthy of notice.

Camille Imits. In the manufacture of candles, a mixture of beet and mutton tallow is preferred. The former alone is too soft and too easily melted; while the latter gives less light, as being tuo difficult to melt. The raw tallow, separated as much *s possible from foreign matter, such as blood, etc., is first chopped small, and then melted in cast-iron or copper vessels. It is then passed through a strainer in order to purify it, sometimes more than once, if necessary. The wicks are made of cotton; they mustbe free from knots, slightly twisted, and perledly dry. The proper lengths are cut by the hand. Taere are diferent processes for sing the candle round the wick. The oldest and simplest consists in dipping the wick, for some instants, in the purified tailov, strecesing it and

rolling it in the hands or on a table. The victs thus preA

pared, are suspended round a circular frame, ta anced by a counter-weight, by means of a pulley fixed to tże celing. By pressing slightly on the frame, the wicks are dipped in the melted tallow at as low a temperature as possible. When they are covered with a layer of sufficient thickness, the frame

is permitted to ascend by the action of the counter-weight, alloond tho wick 1 B, of which the fibres are similar in effect to cool in the air, until they are ready for a new cip in the

and the candles, or rather partially coated wicks, are allowed W. Holion of small tubes. The hot liquid is imbibed by the melted tallow, by which they are covered with a 27 as wille and rises in it in consequence of capillary action. But before; this process is continued until they have writhe u il rien, the heat increases, it is then reduced to vapour, is necessary thickness. Thus are the ordinary dig-candis maie. decomposed, and is finally converted into carburetted hydro- Mould-candles are made in the following manner :-The moulds

The 'extremity of every thread of cotton, therefore, are composed of a mixture of 1 part of tin and 2 parts of Cecomes a small gas-burner, or rather a collection of small lead, well polished in the inside, and formed in the shape Kne-burners. The flame of a wax-light, or a candle, is al ways of a candle. These moulds having been fixed in a vertical composed of three distinct parts. The first oo, the interior, is position, the wick is passed through them, stretched, and that where the gas is disengaged before there is any combus- centrally fixed in that position. The tallow is then poured tion. It is quite dark. In the second IL, surrounding the into them at a very gentle heat ; for if too hot they would stick former, the combination of the hydrogen gas proceeding from to the moulds. As candles grow old, they whiten and become the candle, and the oxygen gas proceeding from the air, com- of a better quality. Prolonged exposure to the air or to the mence, In the third, the exterior part, FF, is shown the dew hastens the whitening process. zone in which this combination is completed. In fig. 231, is roughly represented a more distinct account of this process.

Wax-lights. In the same manner as candles are moulded,

so are wax-lights, only they are more apt to adhere to the Fig. 231,

sides of the mould, which renders the operation more difficult. The mode of their manufacture differs very little from that of candles. By means of a spoon or ladle, the melted wax is poured successively over the top of the wick, along which it cools and solidifies. When they have reached the proper thickness, they are lifted and rolled on a table to give them the proper regularity of form ; a process which is aided by the use of a polished board instead of the hands. Spermaceti candles have long been in great demand on account of their transparency and whiteness. They are moulded, and in their manufacture a solid substance called spermaceti, espressed from the brain of the whale, and purified, is employed, but it is mixed with about 3 per cent. of very white wax. Sometimes a small quantity of colouring matter is introduced into wax-lights, but this has no influence

on the brightness or the colour of the light.

Stearic-lights. The manufacture of stearic candles originated with MM. Gay-Lussac and Chevreul, who took out a patent for them in France, in 1825. They are made of solid and inodorous substances called stearic acid and margaric acid, which are chemically extracted from tallow or fat, the residue yielding glycerin and oleic acid. Stearic is prepared by saponifying beef or mutton tallow by lime ; 1000 lbs. of tallow and 176 gallons of water are placed in a wooden vat, capable of holding 440 gallons, lined with lead, and heated by steam, the periodical action of the compression, the proper level of which is conveyed directly into the vat by means of a circular the oil is constantly restored. An apparatus, long known tube pierced with holes; when the tallow is melted, about 132 under the name of Mariotte's vessel, at last furnished the gallons of a solution of lime, containing about 120 lbs. of means of keeping the level of a running liquid at a constant quicklime, is added, and the mixture is continually stirred. After six or seven hours, the saponification is terminated, and

[graphic]

Fig. 232. the soap of lime has formed a consistent mass, which becomes very hard on cooling. It is next reduced to a very fine powder, and decomposed by sulphuric acid, diluted with water, in vats similar to the first, and heated by steam; when the fatty acids being set free, form an oily stratum on the surface of the acid liquids. The melted fat is decanted, and washed several times, while hot, with water charged with sulphuric acid, and then with fresh water; it is finally run into tin moulds forming cakes of 6 or 8 lbs. in weight. This mass, which is still a mixture of stearic, margaric, and oleic acids, is first powerfully compressed when cold by the hydraulic press, in order to express the greater part of the oleic acid, and then compressed, when at a temperature of 90° or 100°, in order to drive out the height. The chemist Proust appears to have been the first remainder. The oleic acid thus expressed is of a deep brown who, towards the end of the last century, applied the idea of colour, and contains nearly all the margaric acid, with a certain Mariotte's vessel to the reservoir of a lamp with a constant quantity of the stearic acid. The cakes remaining after this level. Fig. 234 represents one of the forms which has been compression are again melted, in contact with a dilute solution of sulphuric acid, which removes the last traces of lime from

Fig. 334. the fatty substance; after which it is freed from the adhering acid by washing it in boiling water. It is then poured into moulds, where it becomes solid, and it is thus brought into commerce,as refined stearic acid, used for the manufacture of stearic lights. In the first process of making stearic lights, the wicks, twisted like those of the common wax-lights, became charred in the same manner as the wick of a candle, and required to be snuffed every minute. M. Jules Cambacérès substituted plaited wicks for twisted ones, and this fortunate invention was completely successful. In consequence of the plaiting, the wick in proportion as the light burned was turned and slightly bent downwards, so that the extremity was made to given to this reservoir. The stop-cock at the bottom being consume itself in the flame.

shut, the cork at the top is removed and the reservoir filled; Dil-lights. Among the ancients, lamps were yaried in form then the cork is replaced. When the lamp is to be lighted, and matter. They were made of terra-cotta, bronze, silver, the stop-cock below is opened, the oil rises in the shorter and even of gold. They had one or more wicks; and Suidas branch io the left, and supplies the wick; but it does not rise gave to a lamp the name of icosymica, because that it had in this branch above the lower level of the open tube immersed twenty wicks. Still they were all constructed on the same in the reservoir. In proportion as the oil is consumed, the plan. They were vessels' in the form generally of an oblong level sinks in the reservoir, and the vacuum thus formed is eup, furnished with a gutter or spout, over the lip of which filled with the air which enters at the bottom of the open tube, projected the extremity of a round wick placed in the vessel and rises in bubbles through the liquid, but the level in the and lying soaked in the oil. These lamps were smoky and shorter branch remains constantly the same. spread a disagreeable smell around them. It was by the light The lamp furnished with the side reservoir furnished with of such a lamp that Demosthenes composed those sublime a flat wick, where the combustion operated in a much better orations which his enemies said smelt of the oil. The wick manner than in the thick irregular wicks of the ancient lainps, was regularly charred after a certain time, and it was necessary was a very great improvement, especially when the wick was to trim it, because the level of the oil in the vessel was con- surrounded with a glass chimney. By means of the latter tinually lowered by the combustion. Fig. 232 represents a addition, a current of air was established which continually

kept up the flame and guarded it from the wavering motions Fig. 232.

produced by the exterior air. Thus surrounded, the flame gave out a much more vivid light, and was prevented from smoking. It was reserved, however, for Argand to carry this arrangement to the highest degree of perfection, by inventing a burner with a cylindrical wick and a double current of air. The new current of air is produced in the centre or axis of the wick, and rises from the bottom of the wick-case. "The invention of this burner, called the Argand burner, was first

announced in February, 1784. It is the union of the constant specimen of an antique lamp. The ancients found that this level of Proust with the burner of Argand which forms the mode of lighting was susceptible of improvement, and they wall lamps manufactured on the great scale by Quinquet

, and description has been transmitted to us in the writings of the suspensory lamps in general, the lateral reservoir was celebrated Hero, of Alexandria, who flourished at the end of sightly and inconvenient by reason of the shadow which it

Cardan, who died in 1575, gives a projected. To remedy this inconvenience, shadowless lamps description of a mechanical lamp analogous to that of Hero. were invented, having the reservoir in a circular form round in use, since the authors referred to only speak of them as bular shape, which, by its effect, completely neutralised the

shadow of the reservoir and conduits. If we substitute, for Towards the end of the last century, the pump or spring- the unpolished lamp-glass, & metal reflector, we shall have the lamp ; see fig. 233. The upper part of this lamp is moveable, lamps the constancy of the level is not perfect, and the intens and can be made to descend into the reservoir by compressing sity of the light always decreases in proportion as the level of e spring; it is sufficient to exert this compression to make the the oil is lowered. Lamps also have been invented hay oil rise in the reservoir from above and soak the wick. By the reservoir situated above the burner, and furnishing

un

the second century B.C:

objects of curiosity;

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