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would be a great mistake not to be especially careful in their forms and outlines. These lines must not be strong, but firm and decisive, and the more simple the better; all darker lines must be reserved for the foreground. The method of securing the lights upon trees, which we have shown in Fig. 109, will explain to the pupil the manner of proceeding more clearly than words can do. In his practice we recommend him first to copy parts of the example, and make separate and repeated studies of those portions which, as he proceeds, he will find to be most

with it cover down the whole of the part intended to be white; when dry, proceed to the completion of the drawing. It will not in the least matter if the lead pencil should pass over the part gummed, it will not have any effect upon it. When the drawing is finished, pin it down at the corners on a board, let it be held in an inclined position, and pour some hot water over it; the gum immediately dissolves, leaving the parts which were covered by it perfectly white. Broad spaces in light, upon which are to be drawn minute and sharply-cut details, may be preserved in this

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difficult. He will be better able to decide for himself than we can for him as to which of those parts may require more frequent repetition; and it is almost needless to say, that by frequent repetition only can he hope to succeed. There is a very easy and legitimate way of preserving in pencil drawings the sharp touches of light which are seen upon polished surfaces, streaks in water, blades of grass, the bright parts of clouds, small objects of a naturally light colour on a dark background, or any effect where brilliancy is requisite, and where a sharp, clear, and distinct outline of the form must be preserved. It is this: After the outline of the object, or part to be preserved, has been made, dip a fine hair-pencil into tolerably strong gum-water, and

way, and, after the gum is washed off, the details may be made out upon them. This leads to the use of gum-water in another way, and that is, as a means of fixing the drawing. If a drawing is worth anything, it surely is worth setting, that is, fixing the lead or chalk with which it is drawn, so that, under moderate treatment, it cannot injure by rubbing. For highly-finished drawings, or where the chalk or pencil has been very liberally applied, it will be better to proceed in this way:--Nearly fill a shallow dish or tray, somewhat larger than the drawing, with a weak solution of gum-water, or-which may sometimes be more convenient-a mixture of milk and water, half of each; pass the drawing carefully through the mixture (face uppermost)

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backwards and forwards; then fix it up on the wall by a corner
to drip and dry; or the drawing may be pinned down to a
board, held on an incline over a dish, and the milk and water
poured over it with a spoon, beginning at the top; it is necessary
to see that all parts of the drawing have been passed over.
the drawings are merely outlines, or have very little shading
upon them, then the fixing medium may be passed over the whole
paper with a broad, flat camel-hair brush. With careful treat-
ment, this method of preserving drawings will be found to be
quite satisfactory.

LESSONS IN FRENCH.-XXIX.

SECTION LII.—THE IMPERFECT TENSE [§ 119].

1. THE imperfect, or simultaneous past tense, may be called the descriptive tense of the French. The action which it represents, or the situation which it describes, is imperfect of itself. This tense leaves the beginning, duration, and end of an action undetermined. It may often be rendered in English by the auxiliary was, etc., and the participle present of the verb [§ 119, § 120].

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L'année dernière j'allais tous les

jours à l'école, Quand nous demeurions à la campagne, nous nous couchions ordinairement à neuf heures,

Last year I went (used to go) every
day to school.

When we were (used to be) in the
country, we used to go to bed at
nine o'clock.

3. The imperfect can seldom be rendered in English by the past tense which takes did* as an auxiliary. The past definite never corresponds in meaning to the English imperfect, composed of the auxiliary was and the participle present. It cannot be rendered by the verb preceded by used to.

J'allais à la chasse hier matin quand nous nous rencontrâmes, J'allai à la chasse hier matin,

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1. De qui parliez-vous ce matin quand je suis venu vous trouver? 2. Ma cousine parlait de son frère et je parlais du mien. 3. N'aimiez-vous pas mieux le boeuf que le mouton autrefois ? 4. J'aimais le bœuf, mais je n'ai jamais aimé le mouton. 5. Ne vendiez-vous pas beaucoup de livres lorsque vous demeuriez à Paris? 6. J'en vendais beaucoup, parceque

j'étais libraire. 7. Le libraire a-t-il vendu beaucoup de crayons ce matin? 8. Il a vendu beaucoup de crayons aujourd'hui. 9. Vendiez-vous beaucoup de parchemin lorsque vous étiez libraire ? 10. Je n'en vendais presque pas. 11. Votre frère portait-il un habit vert lorsqu'il demeurait à Londres? 12. Il portait un habit brun et des pantoufles noires. 18. Que cher chiez-vous ? 14. Je cherchais mon livre. 15. Depuis quand l'aviez-vous perdu? 16. Je l'avais perdu depuis hier. 17. L'avez-vous retrouvé ? 18. Je l'avais retrouvé, mais je l'ai perdu de nouveau. 19. Ce boulanger vous fournissait-il de bon pain? 20. Il nous en fournissait d'excellent. 21. Punis siez-vous souvent vos écoliers ? 22. Je les punissais quand ils le méritaient, 23. Où étiez-vous ce matin quand je vous cherchais ? 24. J'étais dans ma chambre. 25. Je finissais mon thème.

EXERCISE 100.

1. Who was at your house this morning? 2. My friend G. was there, and was looking for you. 3. Did you speak to my father yesterday? 4. I was speaking to him when they brought me your letter. 5. Did your father (use to) wear a white hat when he lived in London? 6. He used to wear a black hat, and my brother wore a black coat. 7. Were you singing when my father came? 8. No, Sir, I was finishing my exercise. 9. Had you lost your pencil this morning? 10. I had lost it, and was looking for it when you spoke to me. 11. You used to like reading (la lecture); did your sister (use to) like it also? 12. She liked it also. 13. What song were you singing this morning? 14. I was singing an Italian song. 15. Have you been I went (did go) a hunting yesterday afraid to speak to me? 16. I have never been afraid to speak 17. Have you brought my book? 18. I have not

I was going a hunting yesterday morn-
ing when we met (did meet).

morning.

4. The imperfect is formed from the participle present, by changing ant into ais, etc. [§ 61]. It may also be formed by adding ais, etc., to the stem of the verb for the first and fourth conjugations; issais, etc., for the second; and evais, etc., for the third.

to you.
brought it.

SECTION LIII.—THE IMPERFECT TENSE (continued).' 1. The imperfect of the indicative of every French verb, regular or irregular, ends in ais, ais, ait, ions, iez, aient. 2. No verb of the first conjugation, er, is irregular in this

5. TERMINATIONS OF THE IMPERFECT TENSE OF THE FOUR tense. CONJUGATIONS.

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3. The only irregularity found in the irregular verbs of the second conjugation, ir, is that, to form the imperfect, the stem of these verbs takes ais, etc., instead of issais; as, ven-ir, je ven-ais; "cour-ir, je cour-ais; cueill-ir, je cueill-ais. Exception: Fuir, to flee-je fuyais.

4. The irregular verbs of the third conjugation, oir, change that termination (oir) into ais, etc., like the irregular verbs of the same; as, sav-oir, je sav-ais; av-oir, j'av-ais. Exceptions: se-oir, to become; voir, to see; and their compounds, and déchoir [see § 63].

5. The changes which the stem of the irregular verbs of the fourth conjugation undergoes, in this tense, are toe various to admit of a complete classification. We, however, offer the following:PRENDRE, to take. Je pren -ais, etc. CONNAÎTRE, to know. Connaiss -ais, etc.

ÉCRIRE, to write.

écriv

CRAINDRE, to fear. craign -ais, etc.

-ais, etc.
CONDUIRE, to conduct.
Conduis -ais, etc.

Like

6. Like prendre and écrire are conjugated, in this tense, those verbs in which prendre and crire appear in composition; as, comprendre, je comprenais; souscrire, je souscrivais. craindre and connaître, those ending in indre and aître-teindre, je teignais; paraître, je paraissais. Like conduire, those ending in ire; as, lire, je lisais; faire, je faisais; luire, je luisais; dire, pounds.

Except when, in interrogative sentences, did is used as an auxiliary je disais, etc. Exceptions: rire, traire, écrire, and their com to used to expressed or understood.

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Il en avait grand besoin.

Quelle voiture conduisiez-vous ?

Pour qui me preniez-vous ?

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He had great need of it.

What carriage were you driving?
For whom were you taking me?

Je venais vous trouver quand je I was coming to you when I met you. vous rencontrai.

À qui écriviez-vous ce matin ?

J'écrivais à ma sœur et à mon frère.

Autrement, otherwise.
Cass-er, 1, to break.

Chasse, f., hunting.
Dire, 4, ir., to say.
Montre, f., watch.
Moins (au), at least.
Mort, -e, dead.
Offens-er, to offend.

sommeil, mais j'a faim, 3. Avez-vous du poivre ou du sel? 4. Je n'ai ni poivre ni sel, j'ai du fromage. 5, Votre frère a-t-il soif ou faim? 6. Mon frère n'a ni soif ni faim. 7. Votre sœur a-t-elle raison ou tort? 8. Elle n'a pas tort, elle a raison. 9. Le bon menuisier a-t-il peur? 10. Il n'a pas peur, mais honte. 11. Avez-vous du lait ou du fromage? 12. Je n'ai ni lait ni fromage, j'ai du beurre. 13. Avez-vous lo beau drap ou le bon thé ? 14. Jen’ai ni le benu drap ni le bon thế. 15. Avez-vous quelque chose, mon bon ami? 16. Je n'ai rien, mon bon Monsieur. 17. N'avez-vous pas de pain? 18. Oui, Madame, j'ai de bon pain, de bon beurre, et de bon fromage. 19. Le charpentier a-t-il scmmeil ? 20. Le charpentier n'a pas sommeil, mais le ferblantier a faim. 21. Avez-vous le marteau de bois du ferblantier ? 22. Je n'ai pas son marteau de bois, 23. Quel marteau avez-vous ? 24. J'ai le marteau d'acier. 25. Avez-vous un bon habit de drap? 26. Non, Monsieur, mais j'ai une robe de soie. 27. Le tailleur a-t-il le bon bouton d'or? 28. Oui, Monsieur, il a le bon bouton d'or.

EXERCISE 11 (Vol. I., page 43).

1. Have you the silver fork? 2. Yes, Sir, I have it. 3. Has the cook the beef? 4. No, Sir, he has it not. 5. What mutton have you? 6. I have the butcher's good mutton and good veal. 7. Has your relation the chest of drawers? 8. No, Sir, he has it not. 9. Has he my fish? 10. Who has all the baker's biscuit? 11. The sailor has I was writing to my sister and to my neither his bread nor his biscuit. 12. Has he his knife and his fork? brother.

To whom were you writing this morn
ing?

VOCABULARY.
Oubli-er, 1, to forget.
Pêche, f., fishing.
Peind-re, 4, ir., to paint.
Reven-ir, 2, ir., to re-
turn.

Sav-oir, 3, ir., to know.
Se tromp-er, 1, to be
mistaken.

EXERCISE 101.

Teind-re, 4, ir., to dye.
Teinturier, m., dyer.
Toile, f., linen cloth.
Rencontr-er, 1, to meet.
Val-oir, 3, ir.,to be worth.
Ven-ir, 2, ir., to come, to
have just.
Vite, quickly.

1. Pourquoi n'écriviez-vous pas plus vite ce matin ? 2. Parceque j'avais peur de me tromper. 3. Ne craigniez-vous pas d'offenser cette dame? 4. Je craignais de l'offenser, mais je ne pouvais faire autrement. 5. Que peigniez-vous ce matin? 6. Je peignais un tableau d'histoire. 7. Votre teinturier que teignait-il? 8. Il teignait du drap, de la soie et de la toile. 9. De quelle couleur les teignait-il? 10. Il teignait le drap en noir, et la soie et la toile en vert. 11. Conduisiez-vous le jeune Polonais à l'école lorsque je vous ai rencontré ? 12. Je conduisais mon fils aîné à l'église. 13. Que lisiez-vous ? 14. Je lisais des livres que je venais d'acheter. 15. Ne saviez-vous pas que ce monsieur est mort ? 16. Je l'avais oublié. 17. Combien la montre que vous avez cassée valait-elle ? 18. Elle valait au moins deux cents francs. 19. Ne valait-il pas mieux rester ici que d'aller à la chasse? 20. Il valait beaucoup mieux aller à l'école. 21. Votre ami que vous disait-il? 22. Il me disait que son frère est revenu d'Espagne. 23. N'alliez-vous pas à la chasse tous les jours lorsque vous demeuriez à la campagne 24. J'allais souvent à la pêche. 25. Mon frère allait tous les jours à l'école quand il était ici.

EXERCISE 102.

?

1. Were you afraid this morning when you came to our house? 2. I was afraid. 3. Of what were you afraid? 4. I was afraid of the horse. 5. Was not your friend afraid of falling (de tomber)? [See Sect. XX. 2, 4.] 6. He was not afraid of falling, but he was afraid of making a mistake (de se tromper). [See 2, in exercise above.] 7. Were you taking your son to school? 8. I was conducting him to school. 9. What colour was the dyer dyeing the silk? 10. He was dyeing some red and some green. 11. Was he dyeing his cloth black or green? 12. He was neither dyeing it black nor green, he was dyeing it pink (rose). 13. What was the gentleman reading? 14. He was reading a letter which he had just received. 15. Were you cold when you came here ? 16. I was cold, hungry, and thirsty. 17. Were you not ashamed of your conduct (conduite) ? ashamed of it. 19. Whither were you going when I met you? 20. I was going to your house. 21. Were you driving your brother's carriage? 22. I was driving my own (la mienne). 23. Were you writing to me or to my father? 24. I was writing to your friend's cousin.

13. He has neither his knife nor his fork; he has his plate. 14. What
dish has he? 15. He has the pretty china dish. 16. Have you mine
or his ?
17. I have neither yours nor his; I have ours,
18. Are you
afraid, Sir? 19. No, Madam, I am not afraid, I am hungry. 20, Has
any one my gold watch? 21. No, Sir, no one has it. 22. What is the
matter with you, Sir? 23. Nothing is the matter with me.

EXERCISE 12 (Vol. I., page 43).

1. Avez-vous le porte-crayon d'argent? 2. Non, Monsieur, je ne l'ai pas. 3. Avez-vous l'assiette de mon frère ? 4. Oui, Madame, je l'ai. 5. Le boucher a-t-il le bon biscuit ? 6. Il ne l'a pas; il a le bon bœuf, le bon mouton, et le bon veau. 7. Avez-vous mon couteau et ma fourchette ? 8. Je n'ai ni votre couteau ni votre fourchette. 9. Qui a le biscuit du bon matelot ? 10. Le boulanger l'a, et j'ai le mien. 11. Avez-vous le mien aussi ? 12. Je n'ai ni le vôtre ni le sien. 13. Avez15. N'avezvous faim ? 14. Je n'ai pas faim, j'ai soif et j'ai sommeil. vous pas honte ? 16. Non, Monsieur, je n'ai pas honte, mais j'ai froid. 17. Votre parent a-t-il raison ou tort? 18. Mon parent a raison, Monsieur. 19. A-t-il mon plat de porcelaine ou mon couteau d'argent? 20. Il n'a ni votre plat de porcelaine ni votre couteau d'argent; il a votre assiette de porcelaine. 21. Quelqu'un a-t-il mon porte-crayon d'argent ? 22. Personne ne l'a, mais votre frère a votre habit de drap. 23. Avez-vous le mien ou le sien ? 24. J'ai le vôtre.

EXERCISE 13 (Vol. I., page 59).

1. Has your brother his silver inkstand? 2. He has it no longer, he has a lead inkstand. 3. Have we the stranger's letter? 4. Yes, Sir, we have the stranger's. 5. Your sister has not her slate, but she 6. Has the joiner your wood or his? 7. He has her satin bonnet. has neither mine nor his, he has the gardener's. 8. Have you my good silk umbrella? 9. I have your silk umbrella and your satin parasol. 10. Have you my bottle? 11. I have not your bottle, I have your sister's trunk. 12. Has the servant this salt-cellar? 13. He has not this salt-cellar, he has that. 14. Have you the good or the bad chicken ? 15. I have neither this nor that. 16. Which chicken have you? 17. I have the cook's. 18. Has the baker poultry? 19. The baker has no poultry, he has milk. 20. Have you your cheese or mine? 21. I have neither yours nor mine, I have the sailor's. 22. Is any one hungry? 23. No one is hungry. 24. Is anything the matter with you? 25. No, Sir, nothing is the matter with me. 26. Have you my joiner's mahogany sofa? 27. No, Sir, I have it not. 28. I have his pretty looking-glass and his good pencil.

EXERCISE 14 (Vol. I., page 59).

1. Votre frère a-t-il le parapluie de cette dame? 2. Mon frère a le parapluie de cette dame. 3. Avez-vous ce parasol-ci ou celui-là ? 4.

Je n'ai ni celui-ci ni celui-là. 5. Avez-vous la montre d'or de l'étranger ?

6. Non, Monsieur, j'ai celle du boulanger. 7. Qui a mon ardoise? 8.

J'ai votre ardoise et celle de votre frère. 9. Le cuisinier a-t-il une salière d'argent ? 10. Le cuisinier a une salière d'argent, et un plat d'argent. 11. Le cuisinier a-t-il cette volaille-ci ou celle-là ? 12. I 18. I was n'a ni celle-ci ni celle-là. 13. A-t-il ce pain-ci ou celui-là ? 14. Il n'a ni celui-ci ni celui-là, il a le bon pain du boulanger. 15. Avez-vous mon parasol de coton? 16. Je n'ai pas votre parasol de coton, j'ai 18. votre parasol de soie. 17. Le jardinier a-t-il une malle de cuir ? Le jardinier a une malle de cuir. 19. Qui a mon bon fromage ? 20. Personne n'a votre fromage, mais quelqu'un a celui de votre frère. 21. Avez-vous le mien ou le sien ? 22. Je n'ai ni le vôtre ni le sien, j'ai celui de l'étranger. 23. Le cuisinier a-t-il cette bouteille-ci ou ce balai-là P 24. Il a cette bouteille-ci, 25. Avez-vous un encrier de plomb ? 26. Non, Monsieur, j'ai un encrier de porcelaine, 27, L'étranger a-t-il de la volaille ? 28. L'étranger n'a pas de volaille, mais

KEY TO EXERCISES IN LESSONS IN FRENCH.
EXERCISE 10 (Vol. I., page 43).

1. Avez-vous sommeil, Monsieur? 2. Non, Monsieur, je n'ai pas il a de l'argent. 29, Votre frère a faim et soif, peur et sommeil, 30.

Quelqu'un a-t-il honte ? 31. Non, Monsieur, personne n'a honte. 32.
Votre frère a-t-il raison ou tort? 33. Mon frère a raison, et le vôtre
& tort.
34. Votre sœur n'a ni son chapeau de satin, ni son chapeau de
velours. 35. Le boulanger a-t-il la commode d'acajou ? 36. Il ne l'a
pas, il a le sofa d'acajou. 37. Le ferblantier a-t-il mon assiette? 38.
Il n'a pas votre assiette, il a la mienne.

EXERCISE 15 (Vol. I., page 59).

1. Have you the carpenter's hammers? 2. We have the black

smith's hammers. 3. Have the blacksmiths two wooden hammers?

4. They have two iron hammers. 5. Have the generals the silk hats of the child? 6. They have the child's jewels and playthings. 7. Have the children the birds of your wood? 8. They have not the birds of my wood, but they have the horses of my general. 9. Has the black

smith a pair of woollen stockings ? 10. The blacksmith has two pairs of woollen stockings. 11. Sir, are you not cold? 12. No, Sir, I am warm. 13. Have you coffee or chocolate ? 14. I have neither coffee nor chocolate. 15. Have you not the cabbages of my large garden? 16. I have the vegetables of your small garden. 17. What is the

matter with your son? 18. My son has nothing. 19. Have you two pieces of bread? 20. The miller has a piece of bread and two barrels of flour. 21. Has the grocer coffee, tea, chocolate, and pepper? 22. He has tea and coffee, and your merchant's chocolate and pepper. 23. Who has money? 24. I have no money, but I have paper. 25. Have you good paper? 26. I have bad paper.

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through the gramme, which is the weight of 1 cubic centimètre of pure water, taken at the maximum density of water, a temperature of 4° Centigrade, and weighed at Paris.

THERMOMETRY.

Heat is "that which produces in us the sensation of warmth." Temperature is-"that energy with which one body seeks to impart its heat to another."

Thus the temperature of a body is no indication of the real quantity of heat in the body. Equal weights of mercury and water may have the same temperature, and yet the water will contain really thirty times more heat or caloric than the metal. Thermometers are measurers of "temperature," not of heat. High temperatures are measured by pyrometers; extremely low temperatures by alcohol thermometers; while mercurial thermometers are used for the intermediate ordinary temperatures. These instruments depend for their action upon the fact that all bodies, with the rise and fall of their temperatures, expand and contract. In pyrometers (Fig. 1), a small bar of platinum, s, which can only be melted by the intense heat of the flame of the oxyhydrogen blowpipe, is placed in a hole, b b, drilled in a piece of graphite, o, a form of carbon which is capable of supporting any heat. The bar projects above the hole, and is bound to the graphite-a piece of which has been sliced away to expose the hole-by a platinum strap, a. The position of the top of the bar is carefully noted. It is now introduced into the furnace whose temperature is required. The bar expands, and when it is removed, the strap prevents it from resuming its former position. Thus the expansion of the platinum is found, and from experiment we have learnt that for every 100° Cent. platinum expands of its length, and therefore we Fig. 1. can calculate the heat of the furnace.

N

Mercury is chiefly used for thermometers for five reasons:1. It is easily got pure, for mercury can be distilled like water.

2. It does not stick to the glass.

3. It has a long range, freezing at - 40° Cent., and boiling at 350° Cent.

4. It expands uniformly-that is, it increases as much in bulk if heated from 50° to 60°, as it will from 150° to 160°.

[graphic]

Fig. 2.

5. Having a low "capacity for heat," its temperature soon changes; it is, therefore, very sensitive.

TO MAKE A MERCURIAL THER
MOMETER.

1. Take a glass tube with a ca pillary bore (fine, "like a hair"), as represented at A in Fig. 2; make about half an inch of mer cury run down it, and measure it at different points in its descent. If it retain its length, the bore is uniform.

2. Blow the bulb, B, not with the mouth, lest moisture be introduced, but by connecting the tube, by an india-rubber pipe, with a bag of the same material, and then pressing the bag while the end of the tube is held in a gas flame, as hereafter to be described.

3. Fasten a funnel of paper, C, to the top of the tube, and put into it some purified mercury; now heat the bulb, and the air expanding will bubble through it. Upon removing the lamp, the air will contract, and the mercury will be forced into the bulb. Repeating this process a few times, the bulb and tube will be filled. The lamp flame is again applied to the bulb, and while the mercury is oozing out, the tube is hermetically sealed, by bringing a blowpipe flame to play upon its open end.

4. Thermometers are graduated according to three scales.

Fahrenheit's Scale, which is best known in England, divides the space between the two fixed points-the freezing and boiling points of water-into 180°. Fahrenheit fixed as his zero (0°) | the temperature which had been observed at Dantzic in 1709, and which he found could always be reproduced by mixing salt and snow together. He therefore, though erroneously, concluded that this was nature's zero-the absolute zero. He compated that his instrument contained at 0°, 11,124 parts of mercury, and at the freezing point 11,156 parts; hence he divided the space between zero and the freezing point of water into 32 parts (11,156 — 11,124 = 32). From this point to boiling point contained 180 of these degrees, therefore 212° indicates the boiling point of water.

It was Fahrenheit who first used mercury for purposes of thermometry.

The Centigrade Scale was introduced by the Swedish philosopher, Celsius, who was a professor at Upsal. In it the freezing

point is the zero, and the boiling
This scale is the one
point 100°.
generally in use in the scientific world.
Reaumur's Scale was proposed by
a French philosopher of that name
in 1731. His thermometers were
constructed with alcohol of such a
strength, that 1,000 parts at the
freezing point of water became 1,080
at its boiling point. Hence the in-
terval between the two fixed points
was divided into 80°.

It is evident that these scales are quite arbitrary, and that we have only two fixed points. It is necessary, therefore, to determine these before the instrument can be graduated.

TO FIND THE FREEZING POINT OF
WATER.

Fig. 3. Water does not always freeze at the same temperature. If water be gradually reduced in temperature, and be kept perfectly still, 3 or 4 degrees below 0° Cent. may be reached before the ice will begin to form; but ice invariably melts at a fixed temperature. Therefore immerse the thermometer in melting ice, and mark the point to which the mercury falls.

TO FIX THE BOILING POINT.

F.

C.

R.

Place the thermometer in a vessel such as is represented in Fig. 3, in which water is boiling, and the steam generated passes round the walls, cc, of the partition to make its escape at B. Thus the compartment D in which the instrument is placed, being enclosed 2/2 by steam, cannot be affected by the temperature of the air.

A is a bent tube of glass, open at each end, in which is a little mercury. So long as the exit of the steam from B is not impeded, the steam will be of a uniform temperature. If the steam could not escape at B, it would be indicated by A, for if the pressure of the steam increase, the mercury will not remain level. The point at which the mercury in the thermometer stands, is marked as the "boiling point."

32°

120°

Boillag

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Freezing

Point

80°

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Fig. 4.

The tube is then mounted on a piece of board, upon which is marked the scale. If Fahrenheit's (Fig. 4a), the space between the two fixed points is divided into 180 equal parts, which are produced above and below 32° and 2120 (which indicate the freezing and boiling points), as far as is required. For Centigrade (Fig. 4b), the division is into 100°, the freezing point being 0°; for Reaumur (Fig. 4 c), into 80°. Fig. 4 compares at a glance these scales.

TO CONVERT DEGREES OF ONE SCALE INTO ANOTHER.
Since 180° Fahr. = 100° Cent. = 80° Reau.
Therefore 1° Fahr. = 4° Cent. =

Beau.

The reason of the following rules will be at once evident:To transfer Fahrenheit degrees to the other scales, subtract 32?, in order that the number of degrees from the freezing point may be ascertained. These multiplied by will give the equivalent number of Centigrade, and by the required Reaumur degrees.

To reduce Centigrade and Reaumur degrees to the Fahrenheit scale, multiply by and respectively, and add 32o.

If the temperature be below the zero in any of the scales, a minus (-) is placed before the number, thus: -5° Fahrenheit means 37° below freezing.

In verifying the following, the student will become expert in these conversions :

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In a good thermometer, the mercury ought to run to the end of the tube with a "click" when it is inverted, proving the absence of air, and completely fill the tube; and when placed in melting ice, the mercury ought to stand at 0°. It frequently happens that the mercury stands above the freezing point. This error is called "the displacement of zero," and is caused by the curious fact that sometimes the bulb does not perfectly contract for two or three years after it was blown; so that for the best instruments the bulbs are kept for more than that time unfilled. If the bulb be made of thick glass, it is less likely to change. It is plain that in a thermometer we are not given the absolute expansion of the mercury, but the difference between the expansion of the mercury and that of the glass. Mercury expands about seven times more than glass.

ESSAYS ON LIFE AND DUTY.-VI.

PATIENCE.

IT is easier to work than to wait. The Italians say, Il mondo è, di chi ha pazienza, or, "The world is his who has patience;" and of all difficult exercises in the science of morals the application of this principle is perhaps the most so. Not only may men overshoot their mark by too much eagerness, but they may neglect that personal fitness by which they may best succeed. It is self-evident that he who rows against a strong tide, exhausting thereby his strength and energy in the tussle with its forces, is not so wise as he who husbands his strength, and patiently waits the turn of the tide. Patience, however, does not imply idleness, for in most matters of earthly duty we may best employ our energies in preparation before we enter upon the strife. It is wiser far for the student to complete his long curriculum at college, than for him to rush into the discharge of duties for which he is only half prepared; and in the long run the measure of a man's preparation is the measure of his duration-that is to say, he has less exhaustible forces than the man who has stocked his vessel with too small stores for a long life-voyage! How many lives have miscarried in their highest ends for want of patience! There are not many like Columbus, ready to hold out to the last; nor, like Palissy, steadily bent, through long seasons of misfortune, on the attainment of his end. As a rule, men like quick investments and quick returns, both in mental and material things; but those are both wiser and nobler who with patient persistency are ready to wait for the issue which, though long delayed, may be well worth having when it comes. Patience should characterise our dealings with each other. Much petulance, irritability, and anger come from want of patience. Especially should we remember, in our dealings with the ignorant, that it becomes us to bear with the faults of native temperament and the mistakes of untrained judgment. Hastiness irritates others and harms ourselves, for no man can be said to be master of himself who permits a spirit of impatience to make him nervous and pettish.

Patience, however, suggests the value of prior preparation. It may be true enough that the occasion will come for future success, but then we must have fitted ourselves for the occasion, or it will be like a high tide rising to fill the creek, and finding us without a vessel ready to launch. Of the many

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