The first word which can be classed as above is slave, you may thus be certain that the card touched is in class A, a slave being a biped. The next word you can fix upon is chains, which being commonly made of some metal, you rank in the mineral class, and know that card No. 4 was the one touched, it being the mineral of the biped class.

Supposing the trick to be repeated, as is very likely, and that a volume of Byron is given to your confederate, who selects the passage commencing—

you know, "cypress" being the first word that can be classed, the card touched must be in class C (vegetable), and the next word "myrtle" being also a vegetable, the card touched must have been No. 11, which is the vegetable of the vegetable class. Many appropriate passages may be easily selected, and your confederate should select a long passage to be read, as it gives greater scope, and helps to mislead the rest of the company; for should they imagine that the card is discovered by the number of lines read, and they touch the same card again, he can select another passage, desiring them to read only as many lines as they choose.

29. "HOLD IT FAST."

You commence by asking the most athletic person in company whether he is nervous; he will most probably answer in the negative; you then ask whether he thinks he can hold a card tightly. If he answers, No, ask the question of some one else, till you obtain an answer in the affirmative. You then desire the party to stand in the middle of the room, and holding up the pack of cards, you show him the bottom card, and request him to proclaim what card it is; he will say it is the knave of hearts; you then tell him to hold the card tightly at the bottom, and look to the ceiling. While he is looking up, you ask him if he recollects his card; if he says, Yes, desire him to draw it away, and ask him what it is; he will, of course, answer, the knave of hearts; tell him he has made a mistake, for if he look at his card, he will find it to be the knave of spades, which will be the case. You then give him the remainder of the pack, telling him that if he looks over it, he will find the knave of hearts in quite a different situation.

This feat, though it excites much admiration, is very simple. You procure an extra knave of hearts, and cut it in half, keeping the upper part, and throwing away the lower. When commencing your feat, get the knave of spades to the bottom of the pack, and lay over the upper part of it, unperceived, your half knave of hearts; and, under pretence of holding the pack very tight, throw your thumb across the middle of the knave, so that the joining may not be perceived, for the legs of those two knaves are so much alike that there is no danger of detection. You, of course, give him the legs of the knave of spades to hold, and when he has drawn the card away, hold your hand so that the faces of the cards will be turned towards the floor, and take an opportunity of removing the half-knave: you may vary the feat by having a half-knave of spades.

30. THE CHARMED TWELVE.

Let any one take a pack of cards, shuffle, take off the upper card, and, having noticed it, lay it on the table, with its face downward, and put so many cards upon it as will make up twelve with the number of spots on the noted card. For instance: if the card which the person drew was king, queen knave, or ten, bid him lay that card, with its face downward, calling it ten; upon that card let him lay another, calling it eleven, and upon that card, another, calling it twelve; then bid him take off the next uppermost card: suppose it to be nine, let him lay it down on another part of the table, calling it nine, upon it let him lay another, calling it ten, upon the latter another, calling it eleven, and upon that another, calling it twelve; then let him go to the next uppermost card, and so proceed to lay out in heaps, as before, until he has gone through with the whole pack.

If there be any cards at the last, that is, if there be not enough to make up the last noted card, the number twelve, bid him give them to you; then, in order to tell all the number of spots contained in all the bottom cards of the heaps, do thus: from the number of heaps subtract four, multiply the remainder by thirteen, and, to the product, add the number of remaining cards, which he gave you; but if there were but four heaps, then those remaining cards alone will show the number of spots on the four bottom cards. You need not see the cards laid out, nor know the number of cards in each heap, it being sufficient to know the number of heaps, and the number of remaining cards, if there be any, and therefore you may perform this feat as well standing in another room, as if you were present.

31. THE TRICK OF THIRTY-ONE.

A trick often introduced by "sporting men," for the purpose of deceiving and making money by it. It is called "thirty-one." I caution all not to play or bet with a man who introduces it: for, most probably, if he does not propose betting on it at first, he will after he gets you interested, and pretend to teach you all the secrets of it, so that you can play it with him; and perhaps he will let you beat him if you should play in fun; but if you bet, he will surely beat you. It is played with the first six of each suit—the aces in one row, the deuces in another, the threes in another; then the fours, fives and sixes—all laid in rows. The object now will be to turn down cards alternately, and endeavor to make thirty-one points by so turning, or as near to it as possible, without overrunning it; and the man who turns down a card, the spots of which make him thirty-one, or so near it that the other cannot turn down one without overrunning it, wins. This trick is very deceiving, as all other tricks are, and requires much practice to be well understood. The persons using it I have known to attach great importance to it, and say that Mr. Fox, of England, was the first to introduce it; and that it was a favorite amusement of his. The chief point of this celebrated trick is to count so as to end with the following numbers, viz., 3, 10, 17 or 24. For example, we will suppose it your privilege to commence the count: you would commence with 3, and your adversary would add 6, which would make 9; it would then be your policy to add 1, and make 10; then, no matter what number he adds, he cannot prevent you counting 17, which number gives you the command of the trick. We will suppose he add 6, and make 16; then, you add 1, and make 17, then he to add 6, and make 23, you add 1, and make 24, then he cannot possibly add any number to count 31: as the highest number he can add is 6, which would only count 30, so that you can easily add the remaining 1, or ace, and make 31. There are, however, many variations to the trick.

32. TO TELL THE NAMES OF THE CARD BY THE WEIGHT.

You desire any person to cut a pack of cards as often as he pleases, and undertake, by weighing each card for a moment on your finger, not only to tell the color, but the suit and number of spots, and, if a court-card, whether it be king, queen, or knave.

You must have two packs of cards exactly alike: one pack to be constantly in use during the evening in performing your other tricks; the second, or prepared pack, in your pocket, which take an opportunity of exchanging, so that it may be believed that the pack of cards of which you tell the names is the same as that you have been using with your other tricks, and which they must know have been well shuffled.

The manner of preparing your pack (which must be done previously) is by the following line, which you commit to memory, the words in italics forming the key:

You will perceive that this is a kind of artificial memory, formed by the circumstances of the initial letter of the words in the line and the names of the cards being identical, as well as the near resemblance of some of the words. The word "threatened" is divided into two words, in order that it may answer for the three and ten; you should pay attention to this, or you will be very likely to forget the ten altogether, which would set you entirely wrong; you should likewise commit to memory the order in which the suits come viz.: hearts—spades—diamonds—clubs.

You should now separate the different suits, and lay them on the table, face upwards, placing heart first, spades next, diamonds next, and clubs last. Having done so, begin to sort (to yourself), according to your key: take up the eight of hearts, placing it in the left hand with its back to the palm; then the king of spades, which you lay over it, next the three of diamonds, next the ten of clubs, then the two of hearts, and so on, until you finish your line, which will terminate with the knave of hearts. You then take up the eight of spades, and go on in the same way till you come to the knave of spades, when you begin again with the eight of diamonds, and go on until you come to the knave of diamonds, and beginning again with the eight of clubs, you go on until you come to the knave of clubs, which finishes the pack, and which is now ready for use; when you have made your exchange, and brought forward your prepared pack, hand it round to be cut.

You now want to know the first card, as a clue to the rest; and therefore take off the top card, and holding it up between you and the light, you see what the card is, saying at the same time, that the old way of performing the trick was by doing so, but that this was very easily detected.

Having thus obtained a knowledge of the first card, which we will suppose to be the ten of diamonds, you then take the next card on your finger, and while pretending to weigh it, you have time to recollect what is the next word in your key, to ten'd, which is to—you consequently know that this card is a two; you must then recollect what suit comes after diamonds, which is clubs; you, therefore, declare the card you are now weighing on your finger to be the two of clubs; the next will of course be the seven of hearts, the next to that the nine of spades, and so on as long as you please.

TRICKS WITH CARDS, THAT REQUIRE APPARATUS.

I shall only give one or two of these tricks, because, in general, the apparatus required for cards is exceedingly expensive. Those that I shall give require but little apparatus, and any boy with the use of his hands can make it.

33. THE CARDS IN THE VASE.

Make a vase with five divisions, two of which hold an entire pack of cards, and the remaining three are only large enough just to admit one card each, as in the figure. A strong silk thread is fastened at A, passes over the three little compartments, through the bottom of the vase, and running over two pulleys, terminates in the weight at B.

Take three cards, say the ace of spades, the ten of diamonds, and the king of hearts, out of a pack of cards, and put one into each of the little divisions pressing the thread down into the bottom of each division. If the cards are left, the weight will descend, and the string being tightened, will push the cards upwards. So a kind of trigger shelf is made, on which the weight rests. The remainder of the pack you put into division 2.

When you show the trick, you take another pack of cards exactly like that which is already in the vase, and handing it to three persons successively, compel them to choose the ace of spades, the ten of diamonds, and the king of hearts.[3] Let some one shuffle the cards, and when this is done, put the pack into division 1. Tell the spectators that when you have struck three times on the table, the cards will come out of the vase. At the third stroke, loosen the catch on which the weight stands, by means of the string that communicates with your table, and the three cards will rise slowly up. In order to show that the cards have really vanished from the pack, take the pack out of division 2 and let any one examine it.

If you prefer, you can draw the thread yourself, by having a kind of a pedal under your table, to which the other end of the string is attached, instead of being fastened to the weight B. If you prefer the weight, you must have a small shelf for the weight to rest upon, when it has descended sufficiently low, or the cards will be forced entirely out by the thread. C is a representation of one of the divisions, showing the semi-circular cut that is made in them for the convenience of taking out the cards.

34. THE METAMORPHOSIS.

In this most excellent trick you choose from the pack the four eights and the two of diamonds; you put the four eights in your left hand and the two on the table; you take in the two, placing an eight on the table, and they are all twos. You exchange the two for the eight, and they all become black cards; you again exchange the eight for the two, and they all turn red; and after again exchanging, you have, as before, the four eights and the two of diamonds.

The method of accomplishing this trick is as follows: Get three plain white cards, exactly like playing cards, and paint them as in the engraving. Mix them with an ordinary pack, and when you are searching for the four eights, with which you say you are going to perform a trick, take them from the pack, and with them an ordinary eight of clubs and a two of diamonds.

Show the cards as in fig. 2, making the spectators observe that there are the four eights. Put the two of diamonds behind the eight of clubs, and lay the eight on the table. The two must be inserted before the eight is removed, or the mystery of the marking will be apparent. Close the cards, turn them over, and spread them out, when they will appear as in Fig. 3. Take in the eight and lay the two on the table; close the cards, and while shuffling them, turn card No. 2 the other way upwards. The cards will then all appear black, as in Fig. 4. Take in the two and remove the eight, turn them over, and spread them out, when they will appear all red, as in Fig. 5. Finally, take the eight, replacing the two on the table, reverse No. 2, and you will have the four eights and the two of diamonds, just as they were at first. You must invent plenty of talk during your changes. If the spectators say that the cards are double, spread them out, and hold them up to the light, (for the light cannot penetrate through the places where the cards are placed over each other,) and if they are still skeptical, hand them the two of diamonds to look at, and in a moment or two hand them the eight of clubs, asking them whether they would like to examine a black card also. This will effectually disarm suspicion.

35. TO HOLD FOUR KINGS OR FOUR KNAVES IN YOUR HAND, AND TO CHANGE THEM SUDDENLY INTO BLANK CARDS, AND THEN TO FOUR ACES.

It is necessary to have cards made on purpose for this trick; half cards, as they may be properly termed, that is, one half kings or knaves, and the other half aces. When you lay the aces one over the other, of course nothing but the kings or knaves can be seen; and on turning the kings or knaves downward, the four aces will make their appearance. You must have two perfect cards, one a king or knave, to put over one of the aces, else it will be seen; and the other an ace, to lay over the kings or knaves. When you wish to make them all appear blank, lay the cards a little lower, and by hiding the aces, they will appear white on both sides; you may then ask which they wish to have, and may show kings, aces, or knaves, as they are called for.

36. TO CHANGE A CARD IN A PERSON'S HAND.

Cut very neatly the spots from a three of spades. Lay the pierced card on an ace of diamonds, and rub pomatum on the ace of diamonds through the places which the spades occupied. Remove the pierced card, and sprinkle the ace of diamonds with jet powder, which adhering to the pomatum, will transform the card into a three of spades.

Place the transformed card at the bottom of the pack, and show a person what card it is. Make him declare it that every one may hear, then place it on the table, face downwards, and push it over the cloth to the spectator, which action will rub off all the jet powder. Tell him to place his hand on the card. Let a three of spades be at the top of the pack, and an ace of diamonds the second from the bottom. Show another person the ace of diamonds, and ask him to tell the name of the card openly. Put the pack down, face downwards, and in so doing make the pass, and bring the three of spades to the bottom.

Tap the hand of the person who is guarding the card, and then tell him to take up the card and show it to the spectators, when it will be seen to be the ace of diamonds. Simultaneously, you take up the pack, and show the three of spades at the bottom.

37. THE CARD IN THE EGG.

To perform this feat, provide a round hollow stick, about ten inches long and three quarters of an inch in diameter, the hollow being three eighths of an inch in diameter. Also, have another round stick to fit this hollow, and slide in it easily, with a knob to prevent its coming through. Our young readers will clearly understand our meaning, when we say, that in all respects it must resemble a pop-gun, with the single exception that the stick which fits the tube, must be of the full length of the tube exclusively of the knob.

Next steep a card in water for a quarter of an hour, peel off the face of it, and double it twice across, till it becomes one fourth of the length of a card, then roll it up tightly, and thrust it up the tube till it becomes even with the bottom. You then thrust in the stick at the other end of the tube till it just touches the card.

Having thus provided your magic wand, let it lie on the table until you have occasion to make use of it, but be careful not to allow any person handle it.

Now take a pack of cards, and let any person draw one; but be sure to let it be a similar card to the one which you have in the hollow stick. This must be done by forcing. The person who has chosen it will put it into the pack again, and, while you are shuffling, you let it fall into your lap. Then, calling for some eggs, desire the person who drew the card, or any other person in the company, to choose any one of the eggs. When he has done so, ask if there be anything in it? He will answer there is not. Place the egg in a saucer; break it with the wand, and pressing the knob with the palm of your right hand, the card will be driven into the egg. Then show it to the spectators.

A great improvement may be made in this feat, by presenting the person who draws the card with a saucer and a pair of forceps, and instead of his returning the card to the pack, desire him to take it by the corner with the forceps and burn it, but to take care and preserve the ashes; for this purpose you present him with a piece of paper (prepared as hereafter described), which he lights at the candle; but a few seconds after, and before he can set the card on fire, it will suddenly divide in the middle and spring back, burning his fingers if he do not drop it quickly. Have another paper ready and desire him to try that; when he will most likely beg to be excused, and will prefer lighting it with the candle.

When the card is consumed, say that you do not wish to fix upon any particular person in company to choose an egg, lest it might be suspected he was a confederate; therefore, request any two ladies in company to choose each an egg, and having done so, to decide between themselves which shall contain the card; when this is done, take a second saucer, and in it receive the rejected egg, break it with your wand, and show the egg round to the company; at the same time drawing their attention to the fact of those two eggs having been chosen from among a number of others, and of its not being possible for you to have told which of them would be the chosen one.

You now receive the chosen egg in the saucer containing the ashes, and having rolled it about until you have blacked it a little, blow the ashes from around it into the grate; you then break the egg with the same wand, when, on touching the spring, the card will be found in the egg.

The method of preparing the paper mentioned in the above feat is as follows: Take a piece of letter paper, about six inches in length and three quarters of an inch in breadth, fold it longitudinally, and with a knife cut it in the crease about five inches down; then take one of the sides which are still connected at the bottom, and with the back of the knife under it, and the thumb of the right hand over it, curl it outwards as a boy would the tassels of his kite; repeat the same process with the other side, and lay them by for use. When about using them, (but not till then, as the papers will soon lose their curl if stretched,) draw them up so as to make them their original length, and turn the ends over a little, in order that they may remain so; when set on fire, they will burn for a minute or two, until the turn-over is burnt out, when the lighted ends will turn over quickly, burning the fingers of the holder: this part of the trick never fails to excite the greatest merriment.

38. THE FIFTEEN THOUSAND LIVRES.

For this trick, prepare two cards like the accompanying engraving; and have a common ace and five of diamonds. Hold down the five of diamonds and the two prepared cards, as shown in the next engraving; and say, "A certain Frenchman left fifteen thousand livres, which are represented by these three cards, to his three sons; the two youngest agreed to leave their five thousand, each of them, in the hands of the elder, that he might improve it." While you are telling this story lay the five on the table, and put the ace in its place; at the same time artfully change the position of the other two cards, so that the three cards appear as in this engraving. Then, resuming the tale, relate that "The eldest brother, instead of improving the money, lost it all by gaming, except three thousand livres, as you here see (laying the ace on the table, and taking up the five). Sorry for having lost the money, he went to the East Indies with these three thousand, and brought back fifteen thousand." Then show the cards in the same position as at first. To render this deception agreeable, it must be performed with dexterity, and should not be repeated, but the cards immediately put in the packet; and you should have five common cards ready to show, if any one desire to see them.

HINTS TO AMATEURS.

The following hints are of considerable importance to the amateur exhibitor.

1. Never acquaint the company beforehand with the particulars of the feat you are about to perform, as it will give them time to discover your mode of operation.

2. Endeavor, as much as possible, to acquire various methods of performing the same feat, in order that if you should be likely to fail in one, or have reason to believe that your operations are suspected, you may be prepared with another.

3. Never yield to the request of any one to repeat the same feat, as you thereby hazard the detection of your mode of operation; but do not absolutely refuse, as that would appear ungracious. Promise to perform it in a different way, and then exhibit another which somewhat resembles it. This maneuver seldom fails to answer the purpose.

4. Never venture on a feat requiring manual dexterity, till you have previously practiced it so often, as to acquire the necessary expertness.

5. As diverting the attention of the company from too closely inspecting your maneuvers is a most important object, you should manage to talk to them during the whole course of your proceedings. It is the plan of vulgar operators to gabble unintelligible jargon, and attribute their feats to some extraordinary and mysterious influence. There are few persons at the present day credulous enough to believe such trash, even among the rustic and most ignorant; but, as the youth of maturer years might inadvertently be tempted to pursue this method, while exhibiting his skill before his younger companions, it may not be deemed superfluous to caution him against such a procedure. He may state, and truly, that everything he exhibits can be accounted for on rational principles, and is only in obedience to the unerring laws of Nature; and although we have just cautioned him against enabling the company themselves to detect his operations, there can be no objection (particularly when the party comprises many younger than himself) to occasionally show by what simple means the most apparently marvelous feats are accomplished.

CURE FOR TROUBLESOME SPECTATORS.

It will sometimes happen at an early stage of the performance, that the ultimate success of the whole is likely to be endangered by a troublesome person, (generally a naughty boy,) who will persist in crying out, "I know how it is done!"—at the same time continually advancing to the table, from which it is, of course, the business of the conjurer to keep his youthful admirers. Should this be the case, the magic whistles may be produced, and the remark made, that now the troublesome boy shall show the company a trick. Having taken up one of the whistles, which has previously been filled with flour or magnesia, dust or soot, proceed to give a few directions, particularly impressing on him the necessity of blowing hard, because the whistle you place in his hand is perforated with a number of holes. The would-be magician is, therefore, excessively mortified, on applying his mouth and blowing hard, to receive the powder in his face. Any turner will make such a whistle, it being nothing more than the usual shaped toy perforated at the top with a number of holes.

THE SECRET OF VENTRILOQUISM.

The main secret of this surprising art simply consists in first making a strong, deep inspiration, by which a considerable quantity of air is introduced into the lungs, to be afterwards acted upon by the flexible powers of the larynx, or cavity situated behind the tongue, and the trachea, or windpipe; thus prepared, the expiration should be slow and gradual. Any person, by practice, can, therefore, obtain more or less expertness in this exercise; in which, though not apparently, the voice is still modified by the mouth and tongue; and it is in the concealment of this aid, that much of the perfection of ventriloquism lies.

But the distinctive character of ventriloquism consists in its imitations being performed by the voice seeming to come from the stomach: hence its name, from venter, the stomach, and loquor, to speak. Although the voice does not actually come from that region, in order to enable the ventriloquist to utter sounds from the larynx without moving the muscles of his face, he strengthens them by a powerful action of the abdominal muscles. Hence, he speaks by means of his stomach; although the throat is the real source from whence the sound proceeds. It should, however, be added, that this speaking distinctly, without any movement of the lips at all, is the highest perfection of ventriloquism, and has but rarely been obtained. Thus, MM. St. Gille and Louis Brabant, two celebrated French ventriloquists, appeared to be absolutely mute while exercising their art, and no change in their countenances could be discovered.

It has lately been shown, that some ventriloquists have acquired by practice the power of exercising the veil of the palate in such a manner, that, by raising or depressing it, they dilate or contract the inner nostrils. If they are closely contracted, the sound produced is weak, dull, and seems to be more or less distant; if, on the contrary, these cavities are widely dilated, the sound will be strengthened, the voice become loud, and apparently close to us.

Another of the secrets of ventriloquism, is the uncertainty with respect to the direction of sounds. Thus, if we place a man and a child in the same angle of uncertainty, and the man speaks with the accent of a child, without any corresponding motion in his mouth or face, we shall necessarily believe that the voice comes from the child. In this case, the belief is strengthened by the imagination; for if we were directed to a statue, as the source from which we were to expect sounds to issue, we should still be deceived, and refer the sounds to the lifeless stone or marble. This illusion will be greatly assisted by the voice being totally different in tone and character from that of the man from whom it really comes. Thus, we see how easy is the deception when the sounds are required to proceed from any given objects, and are such as they actually yield.

The ventriloquists of our time have carried their art still further. They have not only spoken by the muscles of the throat and the abdomen, without moving those of the face, but have so far overcome the uncertainty of sound, as to become acquainted with modifications of distance, obstruction, and other causes, so as to imitate them with the greatest accuracy. Thus, each of these artists has succeeded in carrying on a dialogue; and each, in his own single person and with his own single voice, has represented a scene apparently with several actors. These ventriloquists have likewise possessed such power over their faces and figures that, aided by rapid changes of dress, their personal identity has scarcely been recognized among the range of personations.

Vocal imitations are much less striking and ingenious than the feats of ventriloquism. Extraordinary varieties of voice may be produced, by speaking with a more acute or grave pitch than usual, and by different contractions of the mouth. Thus may be imitated the grinding of cutlery on a wheel, the sawing of wood, the frying of a pancake, the uncorking of a bottle, and the gurgling noise in emptying its contents.

THE MAGIC OF CHEMISTRY.

It is by the action of this same principle, "chemical affinity," that we produce the curious experiments with SYMPATHETIC INKS. By means of these, we may carry on a correspondence which is beyond the discovery of all not in the secret. With one class of these inks, the writing becomes visible only when moistened with a particular solution. Thus, if we write to you with a solution of sulphate of iron, the letters are invisible. On the receipt of our letter, you rub over the sheet a feather or sponge, wet with a solution of nut-galls, and the letters burst forth into sensible being at once, and are permanent.

2. If we write with a solution of sugar of lead, and you moisten with a sponge or pencil dipped in water impregnated with sulphuretted hydrogen, the letters will appear with metallic brilliancy.

3. If we write with a weak solution of sulphate of copper, and you apply ammonia, the letters assume a beautiful blue. When the ammonia evaporates, as it does on exposure to the sun or fire, the writing disappears, but may be revived again as before.

4. If you write with oil of vitriol very much diluted, so as to prevent its destroying the paper, the manuscript will be invisible except when held to the fire, when the letters will appear black.

5. Write with cobalt dissolved in diluted muriatic acid; the letters will be invisible when cold, but when warmed they will appear a bluish green.

We are almost sure that our secrets thus written will not be brought to the knowledge of a stranger, because he does not know the solution which was used in writing, and therefore knows not what to apply to bring out the letters.

Other forms of elective affinity produce equally novel results. Thus, two invisible gases, when combined, form sometimes a visible solid. Muriatic acid and ammonia are examples, also ammonia and carbonic acid.

On the other hand, if a solution of sulphate of soda be mixed with a solution of muriate of lime, the whole becomes solid.

Some gases when united form liquids, as oxygen and hydrogen, which unite and form water. Some solids, when combined, form liquids.

Chemical affinity is sometimes called elective, or the effect of choice, as if one substance exerted a kind of preference for another, and chose to be united to it rather than to that with which it was previously combined; thus, if you pour some vinegar, which is a weak acetic acid, upon some pearlash, (a combination of potassa and carbonic acid,) or some carbonate of soda, (a combination of the same acid with soda,) a violent effervescence will take place, occasioned by the escape of the carbonic acid, displaced in consequence of the potash or soda preferring the acetic acid, and forming a compound called an acetate. Then, if some sulphuric acid be poured on this new compound, the acetic acid will in its turn be displaced by the greater attachment of either of the bases, as they are termed, for the sulphuric acid. Again, if into a solution of blue vitriol, (a combination of sulphuric acid with oxide of copper,) the bright blade of a knife be introduced, the knife will speedily be covered with a coat of copper, deposited in consequence of the acid preferring the iron of which the knife is made, a quantity of it being dissolved in exact proportion to the quantity of copper deposited.

It is on the same principle that a very beautiful preparation, called a silver-tree, or a lead-tree, may be formed, thus: Fill a wide bottle, capable of holding from half a pint to a pint, with a tolerably strong solution of nitrate of silver, (lunar caustic,) or acetate of lead, in pure distilled water; then attach a small piece of zinc by a string to the cork or stopper of the bottle, so that the zinc shall hang about the middle of the bottle, and set it by where it may be quite undisturbed; in a short time, brilliant plates of silver or lead, as the case may be, will be seen to collect around the piece of zinc, assuming more or less of the crystalline form. This is a case of elective affinity; the acid with which the silver or lead was united prefers the zinc to either of those metals, and in consequence discards them in order to attach the zinc to itself; and this process will continue until the whole of the zinc is taken up, or the whole of the silver or lead deposited.

Again, many animal and vegetable substances consist for the most part of carbon or charcoal, united with oxygen and hydrogen in the proportion which forms water. Now oil of vitriol (strong sulphuric acid) has so powerful an affinity, or so great a thirst for water, that it will abstract it from almost any body in which it exists; if you then pour some of this acid on a lump of sugar, or place a chip of wood in it, the sugar or wood will speedily become quite black, or be charred, as it is called, in consequence of the oxygen and hydrogen being removed by the sulphuric acid, and only the carbon, or charcoal, left.

When Cleopatra dissolved pearls of wondrous value in vinegar, she was exhibiting unwittingly an instance of chemical elective affinity; the pearl being simply carbonate of lime, which was decomposed by the greater affinity or fondness of lime for its new acquaintance, (the acetic acid of the vinegar,) than for the carbonic acid, with which it had been united all its life; an example of inconstancy in strong contrast with the conduct of its owner, who chose death rather than become the mistress of her lover's conqueror.

EXPERIMENTS ON COMBUSTION.

Into an ordinary wine bottle put some pieces of granulated zinc, and pour on them a mixture of sulphuric acid and water, in the proportion of about one part of acid to four of water, then close the bottle with a cork having a hole bored through the middle, in which a piece of glass tube is inserted; wait some minutes that the atmospheric air in the bottle may be expelled by the hydrogen gas set free by the decomposition of the water, then apply a lighted taper to the end of the tube, when the gas will inflame, giving out so little light as to be barely visible by daylight, but producing so intense a heat that a piece of platinum wire instantly becomes white hot when held in the flame. If you hold a glass tumbler inverted over the flame, it becomes covered with minute drops of water, the result of the union of the hydrogen with the oxygen of the air, and in this case water is the only product.

If a piece of charcoal, which is pure carbon or nearly so, be ignited, and introduced into a jar, containing oxygen or common atmospheric air, the product will be carbonic acid gas only. As most combustible bodies contain both carbon and hydrogen, the result of their combination is carbonic acid and water. This is the case with the gas used for illumination; and in order to prevent the water so produced from spoiling goods in shops, various plans have been devised for carrying off the water when in the state of steam. This is generally accomplished by suspending over the burners glass bells, communicating with tubes opening into the chimney, or passing outside the house.

To show that oxygen, or some equivalent, is necessary for the support of combustion, fix two or three pieces of wax taper on flat pieces of cork, and set them floating on water in a soup-plate, light them, and invert over them a glass jar; as they burn, the heat produced may perhaps at first expand the air so as to force a small quantity out of the jar, but the water will soon rise in the jar, and continue to do so until the tapers expire, when you will find that a considerable portion of the air has disappeared, and what remains will no longer support flame; that is, the oxygen has been converted partly into water, and partly into carbonic acid gas, by uniting with the carbon and hydrogen of which the taper consists, and the remaining air is principally nitrogen, with some carbonic acid: the presence of the latter may be proved by decanting some of the remaining air into a bottle, and then shaking some lime-water with it, which will absorb the carbonic acid and form chalk.

Into an ale-glass, two thirds full of water at about 140°, drop one or two pieces of phosphorus about the size of peas, and they will remain unaltered. Then take a bladder containing oxygen gas, to which is attached a stop-cock and a long fine tube; pass the end of the tube to the bottom of the water, turn the stop-cock, and press the bladder gently; as the gas reaches the phosphorus it will take fire, and burn under the water with a brilliant flame, filling the glass with brilliant flashes of light dashing through the water.

Into another glass put some cold water; introduce carefully some of the salt called chlorate of potassa, upon that drop a piece of phosphorus; then let some strong sulphuric acid (oil of vitriol) trickle slowly down the side of the glass, or introduce it by means of a dropping bottle. As soon as it touches the salt it decomposes it, and liberates a gas which ignites the phosphorus, producing much the same appearance as in the last experiment.

Into the half of a broken phial put some chlorate of potassa, and pour in some oil of vitriol. The phial will soon be filled with a heavy gas of a deep yellow color. Tie a small test tube at right angles to the end of a stick not less than a yard long, put a little ether into the tube, and pour it gently into the phial of gas, when an instantaneous explosion will take place, and the ether will be set on fire. This experiment should be performed in a place where there are no articles of furniture to be damaged, as the ingredients are often scattered by the explosion, and the oil of vitriol destroys all animal and vegetable substances.

Into a jar containing oxygen gas, introduce a coil of soft iron wire, suspended to a cork that fits the neck of the jar, and having attached a small piece of charcoal to the lower part of the wire, ignite the charcoal. The iron will take fire and burn with a brilliant light, throwing out bright scintillations, which are oxide of iron, formed by the union of the gas with the iron; and they are so intensely hot, that some of them will probably melt their way into the sides of the jar, if not through them.

But by far the most intense heat, and most brilliant light, may be produced by introducing a piece of phosphorus into a jar of oxygen. The phosphorus may be placed in a small copper cup, with a long handle of thick wire passing through a hole in a cork that fits the jar. The phosphorus must first be ignited; and as soon as it is introduced into the oxygen, it gives out a light so brilliant that no eye can bear it, and the whole jar appears filled with an intensely luminous atmosphere. It is well to dilute the oxygen with about one fourth part of common air, to moderate the intense heat, which is nearly certain to break the jar, if pure oxygen is used.

The following experiment shows the production of heat by chemical action alone. Bruise some fresh prepared crystals of nitrate of copper, spread them over a piece of tin foil, sprinkle them with a little water; then fold up the foil tightly, as rapidly as possible, and in a minute or two it will become red hot, the tin apparently burning away. This heat is produced by the energetic action of the tin on the nitrate of copper, taking away its oxygen in order to unite with the nitric acid, for which, as well as for the oxygen, the tin has a much greater affinity than the copper has.