Εικόνες σελίδας
PDF
Ηλεκτρ. έκδοση
[ocr errors]

PAGE

013

[ocr errors][ocr errors]
[ocr errors]

677, 691

[ocr errors]

LESSONS IN MORAL SCIENCE.

LESSONS IN READING AND ELOCUTION.
I. Conscience, or the Moral Faculty; The Moral
Faculty, Original and Universal; A Moral

XXIII. Religion the Guardian of the Soul; Study of
Faculty being supposed, whether its Dictates

Human Nature essential to a Teacher; The
are Uniform ? How far all Men are agreed in

Stage; Education their Moral Judgments

414 XXIV. The Press; Greece in 1820; Trying to Please; II. Whether Conscienc is the same as the Under,

The Wild Boy; The Mocking Bird

591 standing, or a Faculty different from and

XXV. Character of Julius Cæsar; Scrooge and independent of it ; Moral Sense compared

Marley ... with the Taste; Moral Obligation; Supre

XXVI, Our Control over our Physical Well-being; macy of Conscience

429

Classical Learning ; Dame Nature's Charms 195
III. Whether we always do right by obeying the XXVII. The Lyre ; Edmund Burke; Truth

711
Dictates of Conscience ? Whether there is XXVIII. God, the Creator; The Ursa Major

791 in the mind a Law or Rule, by which Man

XXIX. Excellence of the Holy Scriptures: Crescentius;
judges of the Morality of particular Actions ?

Rectitude of Character; Address to the
The Moral Feeling which accompanies every

Ocean; the Bible; the Downfall of Poland;
Moral Judgment; Belief in God, as con-

the Love of Truth

808
nected with the Operation of Conscience . 444 XXX. The Scholar's Mission; the Treasure that
IV. Moral Agency, and what is necessary to it;

waxeth not old; the Young Mariner's Dream;
Man a Moral Agent; Man not under a Fatal

the Victor Angels ......... Necessity

460
V. Man's Direction and Government of his Actions,

LESSONS IN SPANISH.
and his consequent Responsibility; Objec-
tions to the Uniform Influence of Motives;

1. Orthography and Pronunciation ; Different
Summary View of Liberty

476

Methods of Spelling; Sound of Diphthongs and
VI. The kind of Indifference which has been con-

Triphthongs; Syllabication ; Accent; Punc.
sidered essential to Free Agency; Whether

tuarion

469 Men are Accountable for their Motives, or

II. Of the Article and the Noun

484 whether Desires and Affections which pre

III. Or the Adjective .....

503
cede Volition have a Moral Character? The

IV. Degrees of Comparison of the Pronoun.. 5:7
Division of Motives into Rational and Animal;

V. Possessive Pronouns .....

632 Whether Morality belongs to Principles as

VI. Relative Pronours; Interrogative Pronouns.. 54) well as Acts, or is copfin d to Acts alone ?.. 491 VII. Demonstrative Pronouns; Indefinite Pronouns 5:33 VII. dioral II abits; Nature of Virtue 593 VIII. The Verb

573
VIII. Different Hypotheses,

541
IX., X., XI., XII, Conjugation

596, 611, 629, 614 IX. Whether Virtue and Vice belong only to

XIII. Reflective Verbs; l'assive Verbs

El Actions ?

572 XIV., XV. Irregular Verbs
X. Author of our Being, considered in Relation to

XVI. List of Irregular, Defective, and Impersonal
Moral Science

603

Verbs.....
XI. Phenomena of the Universe

035 XVII. List of Verbs with Irregular Pist-Participles ;
XII. Duties of Man to the Creator as thus manifested 663

of the Adverb, the Conjunction, the PrepcsiLESSONS IN PHYSICS, OR NATURAL PHILOSOPHY.

11 n, the Interjection, the Article, the Youn, LIII. The Eye considered as an Optical Instrument;

the A ljective
Sources of Light, and the Action of Lght on

XVIII. List of Numerals, of Pronouns, o Verbe
Planits; Double Refraction; Polarisa'ion

XIX. Use of the Moods and Tenses of Virbs
402

XX. Of the Passive Verb, the Regina of Verbs,
LIV. Circular Polarisatior

425
LV, Magnetism; Prozerties of the Magnet; Terres-

Verts followed by coriain Prepositions, ibe
Use of the Verbs Ser and Estir

773 trial Magnetisin; thi Cumpass

411

XXI. Idiomatic ['se of certain Verbs; of the Adverb 783
LVI. Magnetisation and Laws of Marne ic Action .. 4.57

XXII. Of the Conjunction
LVII. Electricity; Mcare if blectric Forces

473

XXIII. Of the Picposition and Interjection
LVIII. Action of Electrised B. dies on Budies in their
Natural State ; Electrical Machines

489
LIX. Efec's produced by the Accumulation of both

THEORY AND PRACTICE OF TEACHING.
Electricities

523
LX. Various Effects of Statical Electricity ; Dyna-

1. Spirit of the Teacher; Responsibility of the mical Liectricity; Voltaic Pile

621

Teacher...
LXI. Dynamic Electricity; Clicmical Theory of the

II, Personal Habits of the Tcacher
Pile : Constant Current Piles

537

III. Literary Qualifications of the Teacher
LXII. Constant Current Piles.....

533

IV. Right Views of Education; Right Modes of
LXIII. Physiological, l'hysical, Vag? etic and Chemical

Teaching; Pouring-in Process
Eficts of the Galvario Pile or Battery... 509

V. Drawing.out Process; the more Excellent Way;
LXIV. Magnetic Efiec's; Galvanometer

555

Waking-up Nind; Conducting Recitati ns.. 773
LXV. Chemical Effects of the Galvanic Pile or

VI. Exciting Interes in Study; Incentives to Study;
Da'tery .....

601

Lmulation ; Prizes ........
LXVI. Electro-Dynamics; Electro-Magnetism

620

VII. Proper Incentives; School Government
LXVII., LXVIII.

033, 613

VIII. Requisites in the Teacher for Good Government $12
LXIX 'Dynamical Pico'rivity; l'henomena of inüuc-
tion; Apparatus founded upon Currin sif

LESSONS IN TRIGONOMETRY.
Induction

665
LXX. Phenomena of Luduction; l'ractical Applica-
tions of the Galvanic Baitery

I. Plane Trigonometry; Solutions of night-Angled
681

Triangles
LXXI, Dynamical Electricity; Practical Application

II. Solutions of Oblique-Angled Triangles
of the Galvanic Battery....

697

III. Trigonometrical l'ormulæ.....
LXXII. Tiermo-Electrical Currents.

713

IV. Spherical Trigonometry; Right-Angled Sphe-
LXXIII. General Laws and Velocity of Electrical Cur-

rical Triang es....
rents ; Animal Electricity...

729

V. Oblique-Angled Spheriral Triangles ....... **
UXXIV. Application of Liecriciiy t) Medical Purposes 705
XV. Decrology; Airid Metene, Aquests dos 761

VI. Trigonometrical kommu.....................
VI. LXVII. Lumunun Muieuis

777, 793

MISCELLANEA. 111.

809 POLTRY.

Address to the Readers of the Popular Educater we Mn's Bon and the Poor Blu's & in

406 Crespondence. wa Interview

711 Answeis to Correspondents. I the Battle...

714 Literary Notices, etc, etc.

725

[ocr errors]

751

813 .......... $15

[ocr errors]

710 731

769

753

814

ܪ

761 771

[ocr errors]
[ocr errors]

Irradiation is a phenomenon in which white objects, or those ON PHYSICS, OR NATURAL PHILOSOPHY.

of a bright colour, when seen on a dark ground, appear larger

than they really are. The reverse takes place with a black No. LIII.

object on a white ground. It is thought that irradiation arises

from the circumstance that the impression on the retina extends (Continued from page 396.)

more or less beyond the outline of the image. The effect of

irradiation upon the apparent magnitude of the stars is very THE EYE CONSIDERED AS AN OPTICAL perceptible, and they may thus appear several times larger INSTRUMENT.

ihan they really are.

According to the researches of M. Plateau, irradiation varies Insensible part of the Retina.-The retina is not equally sensi considerably in different persons, and even in the same person tive in every part, as is proved by the following experiment of on different days. This philosopher has also shown that Mariotte. Let two black spots be made on white paper, at a irradiation increases with the brightness of the object and the distance of from half an inch to an inch from each other. Then, length of time it is observed. It is perceptible at all distances, when the paper is brought very near the eye, let the right eye is increased by divergent lenses and diminished by convergent be fixed upon the left spot without preventing it from seeing ones. the other. If the paper be now slowly withdrawn, the right Accidental Halo. Contrast of Colours.-Colours which instead spot will disappear for a time, but reappear soon afterwards if of following the impression of an object like accidental colours, the paper is still further removed. The same thing will hap- appear round the object itself when attentively looked at for pen if the right spot is looked at with the left eye. Mariotte some time, are called accidental halos. The impression of the has remarked that at the moment when the spot ceases to be halo is the reverse of that of the object; that is to say, if the visible

, its image is projected upon the insertion of the optic object is distinct, the halo is obscure, and vice versa. nerve in the interior and lower part of the eye. This insensible Contrast of colours is a reciprocal action which takes place part of the eye is called punctum cæcum, or the blind point. between two colours nearly allied, and by virtue of which

Continuance of the Impression on ihé Retina.On whirling each of them assumes the complementary colour of the other. round a lighted coal with rapidity, we perceive a sort of band This contrast was observed by M. Chevreul, who profoundly of continuous fire. Similarly, the rain which falls in drops, investigated the subject, with a view to ascertain the laws of appears like liquid threads in the air. These appearances are the phenomenon. It is attributable to the reciprocal action of owing to the fact that the impression produced by objects the accidental halos above mentioned. M. Chevreul found on the retina remains after the object is removed or replaced that on red and orange being placed side by side, the rel by another. The duration of this continuance varies accord- inclined to violet and the orange to yellow. If the experiment ing to the sensibility of the retina and the intensity of the be made upon red and blue, the red inclines to yellow and the light. M. Plateau of Brussels has discovered, by various blue to green. With yellow and blue, the yellow passes into methods, that it is on the average about half a second. orange and the blue to indigo, and similarly with many other

The impressions of colours as well as forms remain after the combinations. It is needless to remark how important is the removal of the objects that produce them, for if we divide a bearing of this subject upon the manufacture of cloth, carpets circle into sectors and paint them different colours, on turning and other coloured articles. Those who would wish to be it round, the colours mix and produce the sensation of the successful in combining colours must understand the principles colour which would be formed by their mixture. Thus blue of the effect of contrast. and green produce the sensation of green; yellow and red The Eye not Achromatic.--It was long the custom of philo. that of orange, blue and red that of violet; and the seven sophers to attribute to the human eye the property of perfect colours of the spectrum that of white, as is shown by Newton's achromatism, but this notion cannot be admitted without disc. There are several curious apparatus, the effects of which qualification after the various experiments of Wollaston, are explained by the continuance of the impressions upon the Young, Fraunhofer and Muller. Fraunhofer observed that in retina. Such are the thaumatrope, the phenakisticope, the a telescope with two glasses a very fine thread placed inside kaleidophone, and Farraday's wheel.

the instrument is distinctly seen through the eye-piece when Accidental Images.-If a coloured object be placed upon a the telescope is illuminated with red light only, but ceases to dark ground and looked at attentively for some time, the eye be visible, if, without altering the position of the eye-piece, soon becomes wearied and the intensity of the colour grows the telescope is illuminated with light of a violet colour. To feeble. On directing the cyes to a white piece of paper or on see the thread again, it is necessary to diminish the distance the ground, we perceive an image of the same form as the between the two glasses, much more than is required by the object

, but of a complementary colour; that is to say, a colour refrangibility of violet light. Hence it is evident that part which would form white if it were combined with that of the of the effect is due to the aberration caused by the refrangiobject. In the case of a green object, the image is red, and bility of the eye. rice versa; if the object is yellow, the image is violet. These Muller found that, on looking with a single eye at a white disc coloured appearances were remarked by Buffon, who gave on a black ground, the image is clear when the eye is adapted them the name of accidental images or colours. Accidental to the distance of the disc, that is to say, when the image is colours continue for a length of time, proportioned to that formed on the retina. But he observed, that if the eye is not during which the object was observed, and to the intensity of adapted to this distance, that is to say, if the image is formed the light upon it. Generally speaking, they do not disappear at a distance either in front or at the back of the retina, the gradually and without interruption,' but present alternate disc appears to be surrounded with a very narrow blue band. disappearances and reappearances. It is well known also that He concluded from this and other experiments that the eye is if, after having looked attentively at a coloured object, we achromatic as long as the image is received from the focal close the eyes rapidly, and as firmly as possible, so as to distance, or as long as the eye is adapted to the distance of exclude the light, and even screen them from the light by the object. It is not yet known what is the precise cause of means of a thick piece of cloth over them, the accidental images this apparent achromatism of the eye, but it is generally

attributed to the delicacy of the pencils of light which pass Various theories have been proposed to account for the through the aperture of the pupil, and to the fact that the rays phenomenon of accidental colours. That of Darwin is deser- being of various refrangibility, and meeting the media of the ving of mention. He thinks that the part of the retina wbich eye almost perpendicularly, are very little refracted, and hence is wearied by one colour, becomes insensible to the rays of the dispersion is not perceptible. As to spherical aberration, that colour, and is only capable of impressions of the com- we have already seen how that is corrected by the iris, plementary colour; also, that this part of the retina spon- which is a real partition, arresting the marginal rays that taneously assumes an opposite mode of action, which produces have a tendency to go beyond the crystalline, and only sufferthe sensation of the complementary colour. The first part of ing those to pass which are nearest the axis. this theory does not explain the appeara..ce of accidental Short Sighi and Long Sight. The usual cause of short-sightcolours even in darkness, and the second part is merely a edness is a too great convexity of the cornea or crystalline. statement of the phenomenon of accidental images,

The eye being then too convergent, the focus instead of being VOL. V.

131

still appear.

PAGE

711

[ocr errors]

791

LESSONS IN READING AND ELOCUTION,
XXIII, Religion the Guardian of the Soul; Study of

Human Nature essential to a Teacher; The

Stage; Education ...
XXIV. The Press; Greece in 1820; Trying to Please;
The Wild Boy, The Mocking Bird

581 XXV. Character of Julius Cæsar; Scrooge and Marley .......

613 XXVI. Our Control over our Physical Well-being;

Classical Learning : Dame Nature's Charms 1,95
XXVII. The Lyre ; Edmund Burke; Truth ........
XXVIII. God, the Creator ; The Ursa Major
XXIX. Excellence of the Holy Scriptures; Crescentius;

Rectitude of Character; Address to the
Ocean; the Bible; the Downfall of Poland
the Love of Truth

$CY
XXX. The Scholar's Mission; the Treasure that

waxeth notOld; the Young Mariner's Dream;
the Victor Angels ...

LESSONS IN SPANISH.
I. Orthography and Pronunciation ; Different

Methods of Spelling; Sound of Diphthongs and
Triphthongs; Syllabication ; Accent; Patio

tuation ...
II. Of the Article and the Noun
III. Of the Adjective ....
IV. Degrees of Comparison of the Pronoun.
V. Possessive Pronouns
VI. Relative Pronouns; Interrogative Pronouns
VII. Demonstrative Pronouns; Indefinite Prono
VIII. The Verb

IX., X., XI., XII. Conjugation 590, 611.)
XIII. Reflective Verbs; Passive Verbs
XIV., XV, Irregular Verbs
XVI. List of Irregular, Defective, and Imper

Verbs....
XVII. List of Verbs with Irregular Past Part

or the Adverb, the Conjunction. The
tion, the Interjection, the Articles

the Adjective
XVIII. List of Numerals, of Pronouns, or
XIX. Use of the Moods and Tenses of a
XX. Of the Passive Verb, the Regime

Verbs followed by certain Pro

Use of the Verbs Ser and Estar
XXI. Idiomatic Use of certain Verbas
XXII. of the Conjunction
XXIII. Of the Preposition and Internal

[ocr errors]

PAGE
LESSONS IN MORAL SCIENCE.
I. Conscience, or the Moral Faculty; The Moral

Faculty, Original and Universal; A Moral
Faculty being supposed, whether its Dictates
are Uniform ? How far all Men are agreed in
their Moral Judgments ...,

414
II. Whether Conscience is the same as the Under,

standing, or a Faculty different from and
independent of it ; Moral Sense compared
with the Taste; Moral Obligation; Supre-
macy of Conscience

429
III. Whether we always do right by obeying the

Dictates of Conscience? Whether there is
in the mind a Law or Rule, by which Man
judges of the Morality of particular Actions ?
'The Moral Feeling which accompanies every
Moral Judgment; Belief in God, as con-

nected with the Operation of Conscience.... 444
IV. Moral Agency, and what is necessary to it;

Man a Moral Agent; Man not under a Fatal
Necessity ...

460
V. Man's Direction and Government of his Actions,

and his consequent Responsibility; Objec-
tions to the Uniform Influence of Motives ;
Summary View of Liberty

476
VI. The kind of Indifference which has been con-

sidered essential to Free Agency; Whether
Men are Accountable for their Motives, or
whether Desires and Affections which pre-
cede Volition have a Moral Character? The
Division of Motives into Rational and Animal;
Whether Morality belongs to Principles as

well as Acts, or is confined to Acts alone ?.. 494
VII. Moral Habits; Nature of Virtue ...... 509
VIII. Different Hypotheses......

641
IX. Whether Virtue and Vice belong only to
Actions ?

572
X. Author of our Being, considered in Relation to
Moral Science

603
XI. Phenomena of the Universe

635
XII. Duties of Man to the Creator as thus manifested 668
LESSONS IN PHYSICS, OR NATURAL PHILOSOPHY.
LIII. The Eye considered as an Optical Instrument;

Sources of Light, and the Action of Light on

Plants; Double Refraction; Polarisation .. 409
LIV. Circular Polarisation.....

425
LV. Magnetism; Properties of the Magnet; Terres-
trial Magnetism; the Compass

441
LVI. Magnetisation and Laws of Magnetic Action 4.57
LVII. Llectricity; Measure of Electric Forces ..... 473
LVIII. Action of Electrised Bodies on Bodies in their

Natural State; Electrical Machines .... 489
LIX. Effects produced by the Accumulation of both
Electricities ....

505
LX. Various Effects of Statical Electricity ; Dyna-
mical Electricity; Voltaic Pile

521
LXI. Dynamic Electricity; Chemical Theory of the
Pile: Constant Current Piles

537
LXII. Constant Current Piles.....

553
LXIII. Physiological, Physical, Magnetic and Chemical

Effects of the Galvanic Pile or Battery...... 569
LXIV. Magnetic Galvanometer

555
LXV. Chemical of the Galvanic Pile or
Batter

601
LXVI. Electr
Blectro-Magnetism

620
LXVII., LXVII

...... 633, 649 LXIX Dynam

Phenomena of Indue-
tion

Counded upon Currents of
Indu
LXX. Phenom

Action; Practical Applica-
tio
Battery

681
LXXI. Dyna

Practical Application
oft

Lery..
LXXII. Thern

rents......

clocity of Electrical Cur LXXIII. Gener

cricity.
LXXIV. Appli

LXXV. Met
LXXVI. LXX

[graphic]
[ocr errors]
[ocr errors]
[ocr errors]
[ocr errors]

LXXVIII.

The Rich Man's
Elijah's Intervies
After the Battle

[merged small][merged small][ocr errors][merged small]

ssion of an empirical formula given ether the velocities of the two rays. lie, to which Fresnel was conducted widerations, which have this remark- ot's formula may be deduced from was the first to give a complete theory unded on the system of undulations, rkable geometrical construction, by the determine the position of the refracted situations with regard to the axis, on P; but his theory was not admitted by lus established its accuracy by numerous fraction in Crystals with two Axes.-Crystals very numerous, of this class are the sul. magnesia, barites, potash, and iron, with The topaz of Brazil, In these different es of the two axes assume very different

from three to ninety degrees. Fresnel distheory and demonstrated by experiment, that in lih two axes, neither of the refracted rays follows of simple refraction, but calling the line which bisects

between the two axes the middle line, and that which the supplement of this angle the supplementary line, he · mnat in every section perpendicular to the middle line, "I the refracted rays follows the ordinary laws of refrac

and in every section perpendicular to the supplementary , it is the other ray which follows these laws.

POLARISATION. Polarisation by Reflection..-Polarisation is a particular modi. fication of the luminous rays, by virtue of which, when once they have been reflected or refracted, they become incapable of further reflection or refraction in certain directions. Polarisation was first discovered in 1810 by Malus, a French philosopher, who died only a few years since. Light is polarised by reflection or refraction. If reflected on a surface of black glass, light is polarised when the reflection takes place at an angle of 35° 25' with the glass. The following are some of the properties of the polarised ray.

1. This ray undergoes no reflection on falling upon a second plate of glass at the same angle of 35° 25', if the plane of incidence on this second plate is perpendicular to the plane of incidence on the former, but it is more or less reflected if

incident at other angles. . a principal section of a

2. When transmitted through a double refracting prism it wish being placed upon a sheet only gives one image, if the principal section is parallel or permot at at a black point o, on the pendicular to the plane of incidence, while in every other

is out from the point o, li vides position with respect to this plane, it gives two images more ich being unequally refractes, on or less bright,

S, Ó' and o", to the eye. If the 3. It cannot be transmitted through a plate of turmalin wholt on ore of its angular points with whose axis of crystallisation is parallel to the plane of inci

paper, the ordinary image will remain dence, but on the contrary is more and more easily transury image will turn about the other, mitted, as the axis of the turmalin becomes more and more De plane of refraction is not in the perpendicular to that plane.

[graphic]
[ocr errors][ocr errors]

on.

[merged small][ocr errors][ocr errors]
[ocr errors]
[ocr errors]
[ocr errors]
[ocr errors]
[ocr errors]

e

14 ( but the power of puuria..g light by of the language to be learnt must be exhibited, examinte, ani

* kalle con pattuk, wor at the XAKTLEED.

Wix, dur l'istance, completely 2. An Alphabet is a collection of different characters
Chu' ws.de s stallone #10 Un tika ut,iy polarise letters, each of which represer is its own pecuiar kuuut.
• pieli na Wanita *** LANE W Balent planning These lervers differ from each other in tiani, forn, so si

sound. Used as vehicles of though, they must nur on 1
Autost well Puik va post sout 1916.-14, a.yle of polarization of farul iar to the eye, but thiest ust, buth singly and consul,

SA i think * WI ke ti me deut ray must make must be understood.

two gourmet BW x of the substance, in order 3. Two objects are to be before the student whilst per
*iu* tad Kummy disky kyk gerund ** con.plowly as these lessons book, viz. :-
sme

** A s Yuas hate 3715, for gi*, 339 25,
La sed non x 12 comma 22*, and 3% 30% 19% obwicis, various sounds of the letters of the French Alphabet

First. The acquisition of the correct pronunciation of
* stali tratti ***, *** pris* dighe very weil.
corte trees tou p'a 4. in vari ue tuwwisk remarkably in order to read the French Language easily, in iedlig.es, a

Secondly.-To learn how to combine and use these sound,
to the west 4 till not primarution : "The angle of
as buence for which the reflected

profitably.
en fotode you too olio bi tudi Uc remind ray." But this definition

4. The first object will be accomplished by the aid of arus y wynte raud by double retracting English sounds; that is, every sound represented by a les

s vlasti bry tha a kirst, the plane of reflection combination of letters of the French Alphabet, www be
4.65.ht

, wo quiniend ** called the plane of pulæri. unfolded, analyzed and defined, as far as possible, by means
11 set and was with the pinne of incidence, and of anal gous sounds of a letter or continuation of leilers of the
and ? Yasmi wake na mbyla spelariation. It is in this English Alphabet.
Loodud Where the ti ne reflected cannot be

6. The second object will be accomplished by learning a few
ore than any one that this way of Blueation, in a plane per. brief and simple Rules, illustrated and enforced' by appropriate

is tone, It was ales in this plane that it is not examples.
mon dpt 14.1 1. wwwm wbude mi to parallel to that 6. Diligent attention, patient labour, and A DETEEMONITION
Wendy vay, havet, that is polarised by refraction TO SUCCEED, will enable the learner to orercome every
AMI , w d l way, a plane in which it obstacle, and thus make him master of a Language not only

exceedingly difficult for foreigners to acquire, but beautiful in
Ann gebiteu bey Broorple lujuutiom, When a ray of light which itself, and coexistent with the triumphs of civilisation,
* ********* ****1,4 kuude u rannalin upon a place

7. The student's attention is next directed to an inspection
1 *** W * $** viia*, it is only reflected in pari, the of the French Alphabet,

* * * * * thich the plates and is refructed, and the rond 1944. in 1414 pilially polarised in a plane perpen.

Capitale. Bmall Letters.

Capitals. Small Letters. miest Willi, fil 1, of watertion, and consequently to the

A in till bostawo of the light which has been polarised by

b

B

b Ai olene ved, alwo), that the reflected and the

с Intall til contained an equal quantity of polarised

d

D

d liene, mind that the reunion of these two pencils produces

Compare tne A.. E mulutad light. We may therefore regard ordinary light as

f

F

f firmat of twopal pencils, polarised at righe angles. As a

8 phabet at the left G Angeles place of never completely polarises light, we

b

н any employ nevenal, one upon the other, and their successive

i of this page, with setter dine and retrations will give a more complete result.

J # no placed are called piles, and are often omployed to

the one on the K obituin a funcil of polarised light,

. t'olor doutronhy Dohto Retraction. - Light is polarised by double

right, which is the M yefraction when Denon through a cryatal of Iceland spar or

N any other double refracting mubatance,

The two pencils,

English Alphabet, whitebs are intinet on emerging, are both polarised completely,

р

P but in dillerent planes, which are perfectly or nearly perpen

Q

9 and carefully note dugulur to onch other. To prove this, we look through a

R

R parallelopiped of lovland spar at a black spt on a sheet of

the difference be- S white paper. To the naked wj e there appear two imnges with

T

T the same brightness, but if we interpose a pluto of urmalin and

tween them.

I
turn it about in its own plane, each image will disappear and

V
ronppour twice for encli revolution of the turmalin, which
whose that the two emerging rays aro polarised in pinnes
perpendicular to ench other. Tho ordinary imnge vanishes at

Y
у

Y
The moment when the axis of the turmalin is parallel to the

Z

z
principal section of the surface of incidence, and the extra-
Priory image at the moment when this axis is perpen- it has no letter which corresponds to the Englise

In the French Alphabet there are only twenty-are si Tre to the same section; whence we inter that the ordinary it is occasionally found in French books. 1 s ! potarined in the plano of the principal section, and foreign words, and

then pronounced like the East
the extraordinary pencil in a plane perpendicular to that
cot1on1,

8. The French Alphabet is divided in to vorsi: si cosa SOXANTS.

9. VOWELS.
LESSONS IN FRENCH PRONUNCIATION.-Xo. I. These siz letters are called Vowels, rik:

ALMILAUET OF TIIE FRENCH LANGUAGE.
A Vowler Ne Punwariation of any spoken language may be

10. COXSOXASTS.
indred by inniving sons of Thailand, as uttered by
# din ng teacher,
Nut the RsADING and WRITIN3 of any

These sinteza letters are called Coasces:
In cannot thus be learns The pu; il n. ust bring into
requisition on ething else besiues his iniatury pomirt, ir te
Windd the deadly com rebaud ny language. The alphabet

[ocr errors]

1

[ocr errors]

<==============~====~==N.

n

[ocr errors]
[ocr errors]

u

X

« ΠροηγούμενηΣυνέχεια »