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tube be one with a stop-cock at both ends, they may be turned, and the liquid can thus be kept any length of time. Otherwise it will evaporate again into the gas. The evaporation of the liquid produces great cold, as will be f«en in the following experiments.

2 Put a little mercury in a watchglass or butter plate, pour liquid sulphur dioxide over it, and blow a current of air across it with a bellows. The mercury will be frozen.

3. Pour some liquid sulphur dioxide on the bulb of an alcohol thermometer wrapped in cotton. It will sink very low. A mercury thermometer will not do so, because the mercury would be frozen.

4. Pour a quantity of the liquid sulphur dioxide into ice-cold water. Some of it will sink to the bottom. Stir this with a glass rod and it will boil at once, while some of the water will freeze.

SULPHURETTED HYDROGEN, Experiments with. (Read the article Chemical Experiments.) Sulphuretted hydrogen, also called hydrogen sulphide, is a gas com

Fiosed of hydrogen and sulphur, t should be made out of doors or in an out-building, for it has a very bad odor, like that of rotten eggs. It can be made like Hydrogen, using, instead of zinc, lumps of iron sulphide as large as the tip of the little finger. The gas can be collected over hot water, or led into a bottle of cold water, in which it will dissolve.

EXPERIMENTS.

1. All the experiments given under Hydrogen can be repeated with sulphuretted hydrogen. When burned in a jar it will deposit a thin crust of sulphur on the inside.

2. Fill a bottle with chlorine and another with sulphuretted hydrogen and bring them mouth to mouth. Sulphur will be deposited. The same result will follow if chlorine

water and sulphuretted hydrogen water be mixed.

3. Hold a wet silver or copper coin in a stream of the gas or dip it in sulphuretted hydrogen water. The coin will be blackened.

4. Make a drawing or write a sentence on a piece of paper with sugar of lead dissolved in water. It will be invisible when dry. Dip it in sulphuretted hydrogen water, and the writing or drawing will show plainly in black. The reason is, that while sugar of lead is white, sulphide of lead (which is formed when it touches sulphuretted hydrogen) is black.

SULPHURIC ACID, Experiments with. Sulphuric acid is described in C. C. T. (Read also the article Chemical Experiments.) 1. Put a few teaspoonfuls of water into a glass, and on it slowly pour about twice as much sulphuric acid in a fine stream. Stir the liquid with a test-tube containing a little alcohol or ether. Enough heat will be developed to boil the liquid in the tube. Even water will boil in the tube, but not so readily.

2. Make a thick syrup by dissolving sugar in hot water. Put a few teaspoonfuls into a glass and pour sulphuric acid in it slowly, at the same time stirring it with a glass rod. The acid will turn the syrup into a mass of black spongy charcoal, as shown in the figure. If the

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ting it stay about a quarter of a minute. Rinse the paper in water, then in very weak ammonia, and then in water again. The paper will be much tougher than before, being changed to a substance called vegetable parchment. The time it should remain in the acid varies with the kind of paper used, but by trying several times very tough parchment can be made.

SULTAN, a Solitaire game of Cards, played with two full packs. One Ace of Hearts and the eight Kings are removed from the pack and arranged on the table as follows: One King of Hearts (called the Sultan) is placed in the centre, with the Ace of Hearts just above him, and below him the other King of Hearts. On each side of the Ace are laid the Kings of Clubs, just below them the Kings of Diamonds, and below these the Kings of Spades, representing respectively War, the Treasury, and Industry. The back is now shuffled, held back upward, and playing begins. The first four cards are laid in order on one side of the figure already formed, with their ends toward the figure, and the next four on the other side in like manner. These eight cards are called the Sultan's Divan. The piles of suits are now to be completed in order, by placing on the Kings the Aces, Twos, Threes, and so on up to Queens, using cards from the pack, any card from the Divan, or the top card of the Stock, which consists of the cards that cannot be used, piled on one side. The Ace of Hearts is also built upon in like manner. When a place in the Divan is empty it must be filled at once, either by the next card played, or the top card of the Stock, as the player chooses. When the game is ended, it shows the Sultan surrounded by his eight Queens.

SUN-DIALS. The use of sundials and the form of one kind are described in the article Clock in C. C. T. There are many other

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the best material for all the dials, as it does not rust and is easily marked and cut. In the centre is fixed a straight pin called a style, which must be exactly perpendicular to the disk. The accuracy of the dial depends on this, and on its being placed so that the style points in the same direction as the earth's axis. This may be brought about in two ways. In one, a little hole is made through the metal disk, close to the style, and then, on a clear night, the dial is so placed that by looking through this hole, the north star is brought into line with the style. In the other method a triangle is cut out of pasteboard (see Fig. 2) having the A angle C just equal to the latitude of the place. This can be done by finding the latitude on a C Fig. 2. B map, and then

making the angle with the aid of a

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piece of metal marked off in degrees, called a protractor, which can be bought of any dealer in drawing materials. Fix this triangle, with the aid of a compass, so that the end B points due north and the base BC is horizontal. Then fix the dial so that the style points along the line AC, the free end being toward A. The figure 12 must be exactly below the style.

Globe-dial. A dial can be made of an ordinary school globe, mounted on an axis which points toward the north pole (see Fig. 3). The globe

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F'g. 3

is divided into twenty-four parts by meridians of longitude, which are numbered from I to 12 twice over, one six o'clock meridian being exactly on top of the globe, and the other at the bottom. There is no style, the hour being pointed out by the line between the light and dark part of the globe. As this is rather blurred, the dial is not very exact.

Trough dial. This is formed of a semi-circular trough of tin or zinc closed at the end as shown in Fig. 4. Straight lines divide it lengthwise into twelve equal parts which are numbered from 6 A.m. to 6 P.m., the twelve o'clock line being at the bottom. Instead of a style a wire is stretched lengthwise across the

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hours. The trough must be placed in a north and south direction.

Horizontal Dial. This is more common than the others just described, but is harder to make because the dial is not divided into equal parts. To make one exactly requires the use of mathematics, but one can be made roughly as follows: Fix a disk or square plate of zinc on a post, so that it will be perfectly level, and in the middle drive a pin for a style, inclined as before in the direction of the north star. The triangle in Fig. 2 may be cut out of zinc and soldered to the dial, its edge AC answering as a style. Watch the shadow of the style, and mark each hour on the edge of the dial where the shadow falls at that hour. Only the time used must be sun time—not true time. The difference between these two sorts of time will now be explained.

Correction. If the earth moved around the sun at a uniform speed, the sun dial would always indicate the true time, but it moves faster at some times than at others, so that a correction must usually be added to or subtracted from the hour it points out, and the same correction must be used in marking the hours on the dial. A table of these corrections (expressed in minutes) is given below. All corrections marked + are to be added to the reading of the dial to get the true time, and all marked — are to be subtracted. In marking the dial, where it is necessary to get sun time from true time, the corrections marked — are added to the

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pieces of glass together, smoked side inward, by elastic bands, keeping them apart by slips of paper pasted at the ends, so that the smoked side will not rub. The pieces of glass can now be fastened over the eye-pieces of the operaglass by a large elastic band around the middle. The spots can now be seen easily. When a spot shaped so that it can be recognized is seen, it should be watched from day to day, and will be seen to change its place. The reason is that the sun is turning on its axis like the earth, carrying the spot around with it. The average number of sun-spots does not remain the same, but is greatest every eleven years. The last year when there was the largest number was 1881, and the next will therefore be in 1892. Until about that time there will be more and more of them, and then they will decrease in number till about 1897, when they will begin to increase again.

SWAYKA, a game played by any number of persons with an iron pin eight or nine inches long, and any number of iron rings varying in diameter from two inches to one foot. The pin, which is called the Swayka (its name in Russian), is so sharp that it will stick upright when thrown either at the ground or a board floor. The rings are placed in any order on the ground, and the players try to throw the Swayka so that it will stick upright within one of them. Their object is so to place it in each one of the rings in any order.

RULES,

1. The players take turns, each having only one throw in a turn.

2. A player may throw first at whichever ring he chooses, but he must announce beforehand which one it is, and if he throws the Swayka into any other it counts as a miss.

3. Whoever can place the Swayka in all the rings in regular order of size, beginning with the smallest and ending with the largest, receives the name of King, has general control of the game, acts as umpire, and has the right to order any one to pick up the Swayka for him. When he reaches the largest he must begin at the smallest again, otherwise he cannot remain King. He holds the title as long as he can throw successfully in that order. If two or more players earn the right to be King they must throw together, the other players omitting their turns till all but one have missed.

4. No player may throw a second time at the same ring till he has placed the Swayka in all the other rings.

5. When a player misses, all the rings he has thrown into count for nothing, and he must throw, at his next turn, into the next larger ring. If he miss that, he must take the next larger at his following turn, and so on till he is successful or misses the largest ring.

6. Whoever misses the largest ring is out of the game, and is obliged to pick up the Swayka for his companions till some one else misses that ring and takes his place.

7. The game may last as long as desired. If so agreed, he who has been King the greatest number of times during the play is victor.

Swayka is a Russian game, and is said to be very popular in that country.

SWEDISH WHIST. See PreferEnce.

swimming, the art of propelling one's self through the water by the arms and legs.

Learning to Swim. The learner should choose, if possible, a gradually sloping shore with gravelly or sandy bottom, where there is no current. If he is not used to the water, he must first accustom himself to being under it by lying down on the bottom, where it is only one or two feet deep. He

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open his eyes under water, and when he puts his head out he must remember to breathe outward before inhaling, thus expelling the water from his nostrils. After he has acquired confidence, he should wade out to a depth of about four feet, and try to swim to shore, using the simple chest stroke, or swimming "dog-fashion," as explained below. At first he will probably splash about rather aimlessly with hands and feet; but as soon as he sees that he can keep himself afloat, he will be able to follow directions more exactly. When he sinks he can sustain himself by pushing with one hand against the bottom—but this should be done as seldom as possible. When he can swim a few strokes without this aid, he should begin at a greater distance from shore, and so on, until he is perfectly at home in the water. This will probably be only after much patient practice, though some learners make faster progress than others.

This is not the only way of learning to swim. Some people advise the learner to jump at once into water over his depth, trusting to his instinct and to his natural struggles to get to shore; but this should never be tried unless some older person is near to rescue the swimmer in case of need. Timid people should never try it at all. Another

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