To give in this book an outline of what history they should learn, would be also out of the question; we would only say, that if the boys be natives of England, the historical facts connected with their country should be taught, with a distinct outline of the sister countries, and the other nations of Europe. If of Scotland, the history of Scotland; if Ireland, the history of that country; especial care being used to divest this branch of instruction from every thing which would encourage national prejudices, or inflame party feelings, pointing out to the pupils, at every opportunity, the evils of warfare, the disasters arising from rebellion, and the bloodshed and misery springing from religious differences and party influences; shewing them the absurdity of the unchristian-like prejudices we have for various nations, and always endeavouring to impress on their minds that all mankind belong to one common family; and point out to them that if selfishness was at an end, the world would be really happy, and misery, and vice, and unhappiness would be no more. Nothing is capable of more improvement than our method of giving instruction on this subject. Boys were allowed to read through the whole history of mankind, without a single moral lessson having ever been drawn from any part of it; they were allowed to form their opinions and prejudices, without a single effort to direct them in a proper manner; while to teach boys of the poorer classes one single event in the history of their country, would have been considered ridiculous and absurd, or perhaps highly improper. But they did learn something of their own country's history in defiance of those opinions; and what they did learn, from ignorance and prejudice, became a source of evil, instead of what it would have been if given in a judicious and proper manner. We, therefore, think a knowledge of this branch of education given with judicious care highly important.

ASTRONOMY.*

In attempting to give some general notions on astronomy, we will select, as a beginning, the portion most interesting to us-the Earth; and when we have formed a distinct idea of the part which it performs in the general system, we shall be able to form some notion of the grandeur and immensity of the universe. Let us suppose the earth, at its creation, to have been projected forwards. We know, from the laws

The black board is indispensable for illustrating this branch of science.

of motion, that if no obstacle impeded its course, it would proceed for ever, in the same direction and with the same velocity.

Let A represent the earth, and S the sun.

We shall suppose the earth arrived at the point in which it is represented in the figure, having a velocity which would carry it on to B in the space of one month; whilst the sun's attraction would bring it to C in the same space of time. Reasoning upon the laws of uniform motion, we might hastily conclude, that the earth would move in the diagonal, A D, of the parallelogram, A B C D, as a ball struck by two forces will do; but the force of attraction is continually acting upon our terrestrial ball, and producing a continual deviation from a course in a straight line, and thus converts it into a course in a curve line.

Let us detain the earth a moment at the point D, and consider how it will be affected by the combined action of the two forces in its new situation. It still retains its tendency to fly off in a straight line, but a straight line would now carry it away to F; whilst the sun would attract it to the direction D S. In order to know exactly what course the earth will follow, another parallelogram must be drawn in the same manner as the first; the line, D F, describing the force of projection, and the line, DS, that of attraction; and it will be found that the earth will proceed in a curve line, D G, drawn in the parallelogram, D F GE; and if we go on throughout the whole of the circle, drawing a line from the earth to the sun, to represent the force of attraction, and another at a right angle to it, to describe that of projection, we shall find that the earth will proceed in a curve line, passing through similar parallelograms, till it has completed the

A

whole of the circle. The attraction of the sun is the centripetal force which confines the earth to a centre, and the impulse of projection, or the force which impels the earth to fly off, and quit the sun, is the centrifugal force.

We have described the earth as moving in a circle, merely to render the explanation more simple; for, in reality, the centripetal and centrifugal forces are not so proportioned as to produce circular motion; and the earth's orbit, or path, round the sun, is not circular, but elliptical, or oval.

Let us suppose that when the earth is at A, its projectile force does not give it a velocity sufficient to counterbalance that of gravity, so as to enable those powers conjointly to carry it round the sun in a circle; the earth, instead of describing the line A C, as in the former figures, will approach nearer the sun in the line A B. Under these circumstances it will be asked, what is to prevent us from approaching nearer and nearer the sun, until we fall into it, for its attraction increases as we advance towards it? There also seems to be another danger: as the earth approaches the sun, the direction of its motion is no longer perpendicular to that of attraction, but inclines more nearly to it. When the earth reaches that part of its orbit at B, the force of projection would carry it to D, which brings it nearer the sun, instead of bearing it away from it; so that being driven by one power, and drawn by the other towards this centre of destruction, it would seem impossible for us to escape. But `with God, nothing is impossible. The earth continues approaching the sun with an accelerated motion,

till it reaches the point E, when the projectile force impels it in the direction E F. There, then, the two forces act perpendicularly to each other, and the earth is situated as in the preceding figure; yet it will not revolve round the sun, for the following reasons: the centrifugal force increases with the velocity of the body, or in other words, the quicker it moves the stronger its tendency is to fly off in a direct line. When the earth arrives at E, its accelerated motion will have so far increased its velocity, and, consequently, its centrifugal force, that the latter will prevail over the force of attraction, and drag the earth away from the sun, till it reaches G. It is thus that we escape from the dangerous vicinity of the sun; and as we recede from it, both the force of its attraction and the velocity of the earth's motion diminish. From G, the direction of projection is towards H, that of attraction towards S, and the earth proceeds between them with a retarded motion, till it has completed its revolution. Thus the earth travels round the sun, not in a circle, but in an ellipsis, of which the sun occupies one of the foci, and in its course the earth alternately approaches and recedes from it, so that what at first appeared a dangerous irregularity, is the means by which the most perfect harmony and order are produced. The earth then travels on at a very unequal rate; its velocity being accelerated as it approaches the sun, and retarded as it recedes from it.

That part of the e's orbit nearest the sun is called its perihelion, that part most distant from the sun its aphelion. The earth is about three millions of miles nearer the sun at its perihelion than at its aphelion. Some are surprised to learn that during the height of our summer, the earth is in that part of its orbit which is most distant from the sun, and that it is during the severity of winter we are nearest to it. The difference, however, of the earth's distance from the sun in summer and winter, when compared with its total distance from the sun, is but inconsiderable; for three millions of miles sink into insignificance in comparison of ninety-five millions of miles, which is our mean distance from the sun. The change of temperature arising from this difference, would, in itself, scarcely be sensible, and it is completely overpowered by other causes, which produce the variations of the seasons; but the explanation of these must be deferred, till we have made some further observations on the heavenly bodies.

Incidental Conversation.

Q. When the earth at its creation was projected forward, would not

the laws of motion lead us to suppose, that, if the obstacle impeded its
course, it would continue to proceed for ever in the same direction?
A. Yes. Q. What do we see by the lesson we have just read?
A.
That the combined action of two forces prevents this. Q. What are
these forces called? A. The attraction of the sun is the centripetal
force which confines the earth to a centre, and the other is called the
centrifugal force, which impels the earth to quit the sun and fly
off.
Q. How does the earth move round the sun? A. In an oval
or elliptical course. Q. What is this called? A. The earth's
orbit. Q. What is that part of the earth's orbit nearest the sun
called? A. Its perihelion. Q. What is that part most distant
from the sun called? A. Its aphelion. Q. In that part of the year
called summer is the earth nearer the sun than in winter? A. No;
it is more distant. Q. How long does the earth take to perform
its revolution round the sun?
A. One year.

motion called? A. Its annual motion.
real motion of the earth first discovered?

Q. What is this Q. By whom was the

A. By Sir Isaac New

ton. Q. What simple cause led to some of his greatest discoveries? A. Seeing an apple fall from a tree. Q. Was there any thing very wonderful in an apple falling from a tree? A. No; but Sir Isaac began to think why the apple fell. Q. Was it not because the stalk gave way, and there was nothing to support it? A. Yes; but he wanted to know why the apple fell when the stalk gave way. Q. What did he think strange in its doing so? Q. He thought that as an apple is an inanimate thing, it could not move of itself. Q. What did this lead him to think? A. That some force, out of itself, must act upon it, otherwise it would remain for ever in its place, although it was not attached to the tree. Q. Do you think it would but for something acting upon it? A. Certainly; for there are but two ways in which it could be moved. Q. What are they? A. By its own power of motion, or the power of something else moving it. Q. Which power acted upon the apple? A. It having no power of its own, undoubtedly some other power must act upon it-what that power is was the subject of the philosopher's inquiry. Q. But every thing falls on the ground as well as an apple, when there is nothing to keep it up? A. Therefore there must be a universal cause of this tendency to fall. Q. And what is it? A. If things out of the earth cannot move themselves to it, there can be no other cause of their coming together than that the earth pulls them. Q. But as the earth is no more animate than they, how can it pull? A. This brings us to the point: