a little, by making them almost parallel to one another now look into them, and say what you

see.

James. There are more half-crowns now than there were before.

Tutor. It is evident, then, that by reflection only, a single object, for I have made use of but one half-crown, will give you the idea of a vast number.

Charles. If a little contrivance had been used to conceal the method of making the experiment, I should not have believed but that there had been several half-crowns instead of one.

Tutor. Bring me your multiplying glass; look through it at the candle: how many do you see? or rather how many candles should you suppose there were, did you not know that there was but one on the table?

James. A great many, and a pretty sight

it is.

Charles. Let me see; yes, there are: but I can easily count them; there are sixteen.

Tutor. There will be just as many images of the candle, or any other object at which you look, as there are different surfaces on your glass. For by the principle of refraction, the image of the candle is seen in as many different places as the glass has surfaces; consequently, if instead of 16 there had been 60, or, if they could have been cut and polished so small, 600, then the single candle would have given you the idea

VOL. I.-L

of 60, or 600. What think you now about the stars?

James. Since I have seen that reflection and refraction will each, singly, afford such optical deceptions, I can no longer doubt, but that, if both these causes are combined as you say they are with respect to the rays of light coming from the fixed stars, a thousand real luminaries may have the power of exciting in my mind the idea of millions.

Tutor. I will mention another experiment, for which you may be prepared against the next clear star-light night. Get a long narrow tube, the longer and narrower the better, provided its weight does not render it unmanageable: examine through it any one of the largest fixed stars; which are called stars of the first magnitude, and you will find that though the tube takes in as much sky as would contain many such stars, yet that the single one at which you are looking, is scarcely visible, by the few rays which come, directly from it: this is another proof that the brilliancy of the heavens is much more owing to reflected and refracted light, than to the direct rays flowing from the stars.

CONVERSATION XXIII.

Of the Fixed Stars.

Charles. Another beautiful evening presents itself; shall we take the advantage which it offers of going on with our astronomical lectures?

Tutor. I have no objection, for we do not always enjoy such opportunities as the brightness of the present evening affords.

James. I wish very much to know how to distinguish the stars, and to be able to call them by their proper names.

Tutor. This you may very soon learn ; a few evenings, well improved, will enable you to distinguish all the stars of the first magnitude which are visible, and all the relative positions of the different constellations.

James. What are constellations, sir?

Tutor. The ancients, that they might the better distinguish and describe the stars, with regard to their situation in the heavens, divided them into constellations, that is, systems consisting of such stars as were near to each other, giving them the names of such men or things, as they fancied the space which they occupied in the heavens represented.

Charles. Is it then perfectly arbitrary, that

one collection is called the great bear, another the dragon; a third Hercules, and so on?

Tutor. It is; and though there have been additions to the number of stars in each constellation, and various new constellations invented by modern astronomers, yet the original division of the stars into these collections, was one of those few arbitrary inventions which has descended without alteration, otherwise than by addition, from the days of Ptolemy down to the present time. Do you know how to find the four Cardinal points, as they are usually called, the North, South, West, and East?

James. O yes, I know that if I look at the sun at twelve o'clock at noon, I am also looking to the south where he then is; my back is towards the north; the west is on my right hand, and the east on my left.

Tutor. But you must learn to find these points without the assistance of the sun, if you wish to be a young astronomer.

Charles. I have often heard of the north pole star; that will perhaps answer the purpose of the sun, when he has left us.

Tutor. You are right; do you see those seven stars which are in the constellation of the Great Bear? some people have supposed their position will aptly represent a plough; others say, that they are more like a wagon and horses ;-the four stars representing the body of the wagon, and the other three the horses, and hence they

are called by some the plough, and by others they are called Charles's wain or wagon. Here is a drawing of it: (Plate v. Fig. 1.) a b d g represents the four stars, ez в the other three. Charles. What is the star P?

Tutor. That represents the polar star to which you just now alluded; and you observe, that if a line were drawn through the stars b and a, and produced far enough, it would nearly touch it.

James. Let me look in the heavens for it by this guide. There it is, I suppose; it shines with a steady, and rather dead kind of light, and it appears to me, that it would be a little to the right of the line passing through the stars b and a.

Tutor. It would, and these stars are generally known by the name of the pointers, because they point to p, the north pole, which is situated a little more than two degrees from the star P.

Charles. Is that star always in the same part of the heavens?

Tutor. It may be considered as uniformly maintaining its position, while the other stars seem to move round it as a centre. We shall have occasion to refer to this star again; at present, I have directed your attention to it, as a proper method of finding the Cardinal points by star-light.

James. Yes, I understand now, that if I look to the north, by standing with my face to that