The words being thus transcribed on the dials, the hands of both of them are to be placed to the corresponding divisions; for example, when the index of the dial, A, is placed to the word are, that of the dial, B, must direct to the division which contains 1 love; and so on of the rest. You must then write on five cards the five foregoing questions; that is, one of them on each card.

Matters being thus prepared, you present the five cards to any person, and desire him to choose one of them, and then let him direct the index of the first dial successively to each of the five words which compose that question; while another person, placed by the dial to which the touched needle is placed, writes down the words it successively points to, and they will be found to form the answer. The most remarkable circumstance in this recreation is, that the fifteen words on the dial, B, give proper answers to the five questions on the other dial, which contains thirty words; and that every answer consists of the same number of words with the question. These dials, by means of pullies, may communicate when placed on the opposite sides of a room.

THE OBEDIENT WATCH.

Borrow a watch from any person in company, and request the whole to stand round you. Hold the watch up to the ear of the first in the circle, and command it to go; then demand his testimony to the fact. Remove it to the ear of the next, and enjoin it to stop; make the same request to that person, and so on throughout the entire party.

Explanation.-You must take care, in borrowing the watch, that it be a good one, and goes well. Conceal in your hand a piece of loadstone, which, so soon as you apply it to the watch, will occasion a suspension of the movements, which a subsequent shaking and withdrawing of the magnet will restore. For this purpose, keep the magnet in one hand, and shift the watch alternately from one hand to the other.

EXAGGERATED MAGNETISM.

Our readers will, doubtless, recollect several stories, in which the powers of the magnet are greatly exaggerated. Other accounts of its virtues, though true in fact, yet really appear, without some consideration, to be fictitious. There are few readers, who are not acquainted with the story of that mariner, who, as it is gravely related, by approaching too near a rock which contained an immense quantity of loadstone, had his ship forcibly attracted to, and wrecked on, the rock.

In a German collection of fairy tales, In which the ancient chivalry of the court of the famous Charlemagne, the faithful squires who attended on his heroic knights; the damsels in distress, whom they relieved; the dwarfs who were their friends, and the giants and magicians who "worked their

earthly woe," are the principal characters, we remember a passage to the effect following:-" The knight, who volunteered to adventure forward from the body of chivalry, that were bent on this exploit, to reconnoitre the position of this gigantic enchanter's castle, had scarcely approached within sight of it, when he beheld the enormous bulk of the giant himself leaning against the outward wall. Pursuant to the instructions he had received, the knight, forthwith, turned his gallant steed's head toward his companion in arms, and, at a swift pace, came pricking o'er the plain. He now heard the giant in pursuit, and struck his spurs into his good steed's flank; but, alas! he had scarcely approached within view of the chivalric troop, when the mighty hand of the giant magician was stretched forth, armed only with one of his horse's shoes, which was made of loadstone, and, by its attractive powers on his steel armour, his grieved associates had the mortification of seeing

What wonders may be brought to pass,
By the optician's magic glass!
A barley-corn of painted paper,
Illumin'd by a farthing taper,
Into a spacious plain extendeth,

Whereon Dan Sol his hot glance bendeth
The leech's paltry, dark green potion
Is magnified into an ocean:

His little, crabb'd, prescriptive scrawl,
Into th' hand-writing on the wall:
Look one way, and a blow-fly's nose

To elephant's proboscis grows;

Turn t'other end, hippopotamus

Becomes a gnat compared with a mouse.

THE Science of optics affords an infinite variety of amusements, which cannot fail to instruct the mind as well as delight the eye. By the aid of optical instruments we are enabled to lessen the distance to our visual organs between the globe we inhabit and "the wonders of the heavens above us;" to observe the exquisite finish, and propriety of construction, which are to be found in the most minute productions of the earth;to trace the path of the planet in its course round the magnificent orb of day, and to detect the pulsation of the blood, as it flows through the

veins of an insect. These are but a small portion of the powers which this science offers to man; to enumerate them all would require a space equal to the body of our work: neither do we propose to notice, in the following pages, the various instruments and experiments which are devoted solely, or rather, chiefly, to purposes merely scientific; it being our intention merely to call the attention of our juvenile readers to such things as combine a vast deal of amusement with much instruction; to inform them as to the construction of the various popular instruments; to shew the manner of using them, and to explain some of the most attractive experiments which the science affords. By doing thus much, we hope to offer a sufficient inducement to push inquiry much further than the information which a work of this nature will enable us to afford.

THE CAMERA OBSCURA.

We give our young friends a brief description of this optical invention; though very common, it is extremely amusing; almost every one has seen

B

D

M

it, but few persons know how to construct it. A C represents a box of about a foot and a half square, shut on every side except at D C; O P is a smaller box, placed on the top of the greater; M N is a double convex lens, whose axis makes an angle of forty-five degrees with B L, a plane mirror, fixed in the box, OP; the focal length of the lens is nearly equal to CS+S T, i. e. to the sum of the distances of the lens from the middle of the mirror, and of the middle of the mirror from the bottom of the large box. The lens being turned toward the prospect, would form a picture of it, nearly at its focus; but the rays, being intercepted by the mirror, will form the picture as far before the surface as the focus is behind it, that is, at the bottom of the larger box; a communication being made between the boxes by the vacant space, Q O. This instrument is frequently used for the delineation of landscapes; for which purpose, the draughtsman, putting his head and hand into the box, through the open side, D C, and

drawing a curtain round to prevent the admission of the light, which would disturb the operation, can trace a distinct outline of the picture that appears at the bottom of the box.

There is another kind of camera obscura, for the purposes of drawing, constructed thus: in the extremity of the arm, P Q, that extends from the side of a small square box, B L, is placed a double convex lens, whose axis is inclined in an angle of forty-five degrees, to a plane mirror, B O; the focal length of the lens is equal to its distance from the side of the box, OT; therefore, when the lens is turned toward the illuminated prospect, it would project the image on the side, O T, if the mirror were removed;

but this will reflect the image to the side, M L, which is as far distant from the middle of the mirror as this is from the side, O T. It is there received on a piece of glass, rough at the upper side, and smooth at the lower, and appears in its proper colours on the upper side of the plate. It is evident that in each of these instruments the image is inverted with respect to the object. M S is a lid to prevent the admission of light during the delineation of the picture; and others, for the same purpose, are applied to the sides, M R and NL.

You may also construct the camera obscura in a room, thus:-you first darken the room, by closing the shutters, and every place where the external light can be admitted. You then cut a circular hole in the shutter, or a board placed against the window, in which you place a lens, or convex-glass, the focus of which is at the distance of not less than four, nor more than fifteen or twenty feet: from six to twelve feet is the best distance. At this distance, also, place a pasteboard, covered with the whitest paper, with a black border, to prevent any of the side rays from disturbing the picture; let it be two feet and a half long, and eighteen or twenty inches high; bend the length of it inward, to the form of part of a circle, the diameter of which is equal to double the focal distance of the glass: then fix it on a frame of the same figure, and place it upon a moveable foot, that it may be easily fixed at that exact distance from the glass where the objects paint themselves to the greatest perfection. When it is thus