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ascend, because the density of the water is greater than that of the cork, and therefore buoys it up. The ascent of smoke and vapours depends on the air. Blow out a candle and place it under the glass receiver of an air pump, the smoke rises to the top; but if the air is exhausted to a certain degree by the action of the pump, the smoke descends, like all other heavy bodies. At all times the smoke can ascend no higher than where it meets with air of a density equal to itself, and there it will spread about like a cloud.

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When the Almanack states that the clock is either fast or slow so many minutes and seconds, it means that the time shown by watches and clocks differs from the time shown by the sun, or by a sun-dial. Clocks are made to keep time uniformly during the entire year; and the twenty-four hours by a clock make a day of average length. Now the sun (as a sun-dial shows) in the course of the year makes the days of unequal length, some being rather longer than the average, and others shorter. For astronomical purposes it is necessary to know the exact difference, and this is stated in the almanacks by describing the clock as so much faster or slower than the

sun.

But what occasions the difference? The unequal motion of the sun, or rather the unequal motion of the earth in its journey round the sun; the motion being sometimes faster, and at other times slower, than the average. One of the almanacks thus describes the variation: The sun is south, or shows noon, so many minutes before (or after) 12, by the clock.

ANSWER BY E. L. E.

The earth, in revolving round the sun, moves in an orbit which is elliptical or oval; so that at one time she approaches nearer to that luminary than at another. It is a law of nature, that the nearer a body is to the centre of gravity, the swifter will be its motion. When the earth

is in that part of her orbit nearest to the sun, her revolution on her axis is performed in less than twentyfour hours; consequently, the clock is slower than the sun-dial. On the contrary, when she is farthest from the sun, her revolution occupies more than twenty-four hours; and then the clock is faster than the sun-dial. From the last week in December to the middle of April, and from the middle of June to the end of August, the clock is faster than the sun-dial; whilst in the intermediate months, the clock is slower than the sun-dial; but both agree only on four days in the year.

THIRD QUERY.

"An inquiring boy, nine years of age, asked, Why his hoop did not fall while it was turning round, but would not stand upon its edge when still?"

ANSWER BY "PERSEVERANCE." The first query of a "Bible Class Teacher" divides itself into the two following:-Why a hoop does not fall while turning round? and, Why it will not stand on its edge when still? The last of these questions is theoretically incorrect; for were the hoop standing in such a position that a line drawn from the point of support through the centre of gravity of the hoop, would be perpendicular to the plane on which the hoop stood, then the hoop would stand, which contradicts the question; but as this is almost impracti

cable, the hoop, in nine hundred and ninety-nine cases out of one thousand, will fall to the ground, and even if the thousandth attempt suc

ceeds, it stands in "unstable equilibrium," and the slightest movement will cause it to fall.

We now come to the first portion of the question, viz., Why a hoop does not fall while turning round?

In turning round, the point of support, or rather of contact, of the hoop with the ground is continually changing; and the cause of the hoop not falling rests in the propulsive movement, for before gravity has time to cause the hoop to fall while in any one position, that position is changed, so that gravity must, as it were, exert itself anew to cause the fall. This is evident, because if the hoop is suddenly stopped, so that its point of contact with the ground remains for a short time the same, then gravity has time to act, and the hoop falls.

FOURTH QUERY. "When a tumbler is struck so as

to raise a ringing sound, why does placing the finger upon the rim stop the sound?"

ANSWER BY G. W.

On striking a tumbler or other sonorous body, it vibrates, and by that means agitates and compresses a certain quantity of air, which again expands, and in so doing repeats the pressure on the air next in contact with it, and thus each stroke of the vibrating glass sends out a number of waves of compressed air, which, thus set in motion, finally reach the ear, where, giving a similar impulse to the tympanum, or

drum of the ear, produce that impression which we call sound.

But on touching the glass with the finger the vibration is destroyed, and the sound consequently ceases.

ANSWER BY "PERSEVERANCE."

With reference to the second question. When a tumbler is struck so as to cause a ringing sound, a vibratory motion is given to the tumbler; placing the finger on the rim stops the vibrations, and consequently the sound.

The following proves that a vibratory motion is given to the tumbler by striking. Tie a button to a piece of thread, and suspend it by the finger and thumb over a tumbler, in such a way that the button shall rest against the side of the tumbler; strike the tumbler, and the button will be forcibly driven away from the side of the tumbler, and on falling back to it will be again driven away, and will continue to be driven away till the vibrations cease.

FRESH THOUGHTS FOR YOUNG | poured into a glass cracks it, but

THINKERS.

1. Why does the sun, shining on the fire, very often put it out?

2. What is the reason that when it lightens, milk and beer are frequently turned sour?

3. How is it that boiling water

if held over the steam previously, the hot water does not affect it?

4. Explain why a new sheet of tin, held before the fire, is so long in becoming hot; but if painted, the surface quickly becomes unbearably

hot?

Reviews.

a Memoir of Edward Thomas, Thirty-one Years Superintendent of the Silver-street Girls' Sunday School, London. With Selections from his Journal and Correspondence. London: Peter Jackson, and the Sunday School Union.

J. P.

THE ZEALOUS SUPERINTENDENT: | ignorant beyond the reach of Sunday schools, here was his proper place, and here he won his chiefest honours. Few, perhaps none, ever pursued a more steady and truly useful course in this particular department; and certainly none ever won to himself more of the love and gratitude of scholars and of teachers, or was more signally crowned with acceptance and success. His journal abounds with indications that all this was the delightful fact. Again and again do we meet with notices of scholars brought to Christ, and of previous fruit from his labours coming forth to light; while the affectionate estimation in which he was held by all who knew him, meets us at every turn.

One of the most delightful sights on earth is the sight of one, whose youth, manhood, and declining years have all been devoted to his God, coming to a good old age like a full shock of corn, ripe and ready for the Master's garner; and giving up his labours only with his life, in order to receive his crown.

Such was Edward Thomas, whose brief memoir is here presented for our notice. Converted to God in youth, he at once and for a long succession of years devoted all his powers to His service; till at last, at the goodly age of "three score years and ten," he went to receive his reward, and enter on his Master's joy. His grand sphere of action was the Sunday school, and though he laboured in other ways for Christ, visiting the sick, and instructing the

A few extracts will bring out these facts:

"March 9, 1818.-At our monthly meeting of teachers, a young man was admitted a teacher, named J. B., who had grown out of my knowledge; but I had the satisfaction to learn that, about ten years ago, he was a scholar in my class; the Lord having since been merciful to him, and from

a sense of gratitude for early instruction, he has become a teacher."

"As an inducement to the teachers to attend the early prayer-meeting on the Sunday mornings, Mr. J. said, 'If any of you wish to hear a Sundayschool boy pray, you must come to the early prayer-meeting. Oh, how earnestly he prays for the success of Sunday schools!' I asked Mr. J. his name, and he said it was T. H.; І could scarcely suppress a tear to think that this young man was also in my class about nine years ago."

"March 23, 1818.-Easter Monday. The annual rewards were distributed. On this occasion, also, six of the elder scholars were added to the list of teachers; four of them from the girls' school, and the other two, youths who had been in my class, and making four who have be

come teachers."

His annual meetings with the older scholars brought out many other instances of good. Here he is sitting down with "five" of his old scholars; there finding several who had become heads of families, and were decided Christians; and there learning of others who were actively engaged as teachers.

The book altogether presents a fine pattern of what an affectionate and faithful teacher ought to be; gives a model to all our junior teachers to imitate; and affords delightful encouragement to all now labouring for Christ. As such it should be in the hands of all our teachers, and find a place in all our Sunday school libraries.

One only fault with the book is its brevity. There was, we believe, am

ple material to have formed a much larger volume; and we are sure that none will read what is gathered here without wishing that much more had been furnished to their hands.

GEORGIE AND LIZZIE. By COUSIN KATE, Author of "Set about it at Once," &c. Edinburgh: W. P. Kennedy.

A charming book for little people, in Cousin Kate's best style. A pretty story in itself, and with other stories interweaved. We cordially commend it to mothers as a very good book for their children to possess.

CONGRATULATIONS AND COUNSELS; a Book for Birth-days. By JOHN Cox, Author of the "Great High Priest," &c.

CHRISTIAN EXPERIENCE, its Counterfeits, Helps, and Hindrances. A Dialogue. By Ditto. CONVERSE WITH CONSCIENCE; a Few Words to Members of Christian Churches. By Ditto. ENCOURAGEMENT TO INQUIRERS; a Few Words to Anxious Souls. By Ditto.

London: Ward and Co.

All these books are of more or less good tendency, but all are not suited for our youth; indeed the only one that is so is the first, and this is by far the best in the list. Our author seems to have been gradually feeling his way for some time past to enlightened and scriptural views on the plan of salvation, and the mode of presenting the gospel to sinners; and we hail the light that has so far led him right. We could mention points still further on to be attained,

and to which we believe he will ultimately come, as he investigates the truth and seeks divine illumination.

The Birth-day Book is very much calculated for usefulness, and may be put with confidence into young people's hands. There are better tracts for inquirers abroad than the one above, and the other two works are scarcely fitted for our general readers.

A GEOGRAPHICAL CLASS BOOK
OF PALESTINE, for the Use of
Sabbath and Day Schools. By

WILLIAM LUNDY. London: A. Hall and Co., Paternoster Row

This is a really excellent, cheap, and useful work for Bible classes, containing in small compass a great deal of valuable and interesting information. The arrangement is very good, and the descriptions short and full, with ample reference to scripture scenes and facts connected with the places spoken of. We would introduce the work to the notice of senior classes, as one of the best and cheapest of the kind we yet have seen.

Chapter of Varieties.

THE TALEBEARER.

"The words of a talebearer are as wounds."-Prov. xviii. 8.

The word properly signifies a pedlar, who buys goods (stolen ones it may be) at one place, and sells them at another, taking care to make his own market of them. So a talebearer makes his own visits, to pick up at one place, and utter at another, that which he thinks will lessen his neighbour's reputation, that he may build his own upon it. - M. Henry's Sermon on Friendly Visits.

"I AM A CHRISTIAN."

the purse which you have lost," said the Christian. The officer, on seeing his purse, was much surprised and pleased: but he could not help inquiring why the poor man had brought it to him, the custom of that country allowing people to keep what they found. "I am a Christian," said the poor man, "and my religion obliges me to do it."

THE BIBLE.

The Scriptures contain, independently of a divine origin, more true sublimity, more exquisite beauty, purer morality, more important history, and finer strains, both of poetry and eloquence, than could be collected, within the same compass, from all other books that were ever composed in any age, or in any idiom. The two parts of which the Scriptures consist are connected by a chain of compositions, which bears no

An officer riding in the streets of Pekin (in China) dropped his purse. A poor man, who was a Christian, saw it fall, took it up, and ran after the officer to give it to kim, but did not overtake him till he had reached his house. The officer, who was a heathen, asked him rather rudely what he wanted. "To restore | resemblance, in form or style, to any

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