« PreviousContinue »
both a battery and a needle apparatus to be established at each place, and each in connection with tho other, it will be at once Eeen that the operators at both towns may signal to each other.
1 CODE 0? SIONALS.
Although the later improvements in electro-telegraphic science have led to the invention and adoption of new and more serviceable codes, tho one shown in the
/ // '// ff/1
R S T
J' V/ J//
/ *// ^
accompanying diagram, and which was employed in Wheatstone's first single needlo telegraph, may be used with success in "amusement" telegraphy. The alphabet is situated both on the right and tho left hand side of the needle; some letters require four movements of the needle, but the last motion which completes the indication of a letter situated on the right hand side is always a movement to the right; in like manner the last motion which completes the indication of a letter on the left side is always a movement to the Iqft. For example, the letter W is indicated by four motions ot the needle, three to the left and one to the right. Tho operator must bear in mi ml that the deflections of the symbols for each letter commence in the direction of tho short marks, and end with tho long ones; the deflections of a single needle may thus be made to denote all tho letters of the alphabet. The letters are indicated by the movement of tho upper half of tho needle, the numerals by those of tho l"n\r half: for example, the figure 4 is designated by the motion of the lower extremity once to the right and once to the left; the figure 9 by a movement once to the left and once to the right, and so on. The coil with its enclosed needle i s shown in the marginal cut.
Or apparatus for stopping or reversing tho direction of the galvanic current.— In making electro-magnetic experiments, and especially for electro-telegraphing, an apparatus for quickly shutting on, shutting off, and changing the direction of the current, so as to vary the motions of tho needle, is absolutely indispensable. Numerous contrivances of great ingenuity have been invented, but the one shown in the figure will serve very well for private experimenting. On a squared block of wood ore fixed tho two brass bands, B B, C C, terminated at their extremities by square blocks of brass with binding screws, and cup-shaped holes. D D, two fiat pieces of brass connected and insulated by the glass rod, E. These are the break pieces, and move on joints, F F, where they are connected by the wires, P N, with the battery. The other binding screws at the terminations of the brass bands servo to connect the arrangements through which the currents are to pass. A coil enclosing a light magnetic needle, representing a telegraphic signalling apparatus, may be purchased at a trifling cost, with two or throe hundred feet of insulated wire.
Some of our young readers may have commenced the prudent habit of leaving their surplus gold, silver, or even copper, to accumulate in the hands of the banker. Those who have taken to practising the useful art of electrotyping will scarcely need to be reminded that there is another way of causing the accumulation of these metals, and may frequently find themselves concentrating their
"I'liey play such merry pranks, thai some wmilii think
REMISTRY has been called, by its votaries, a fascinating science, and with some truth, for it certainly affords more recreation than any other. That it is the most useful of all sciences cannot be denied, nor can there be a doubt that it has a tendency almost to enchant those who devote their attention _? to it. Its powers are almost infinite, and, in some instances, produce effects which appear magical; a great number of those conjuring tricks which have astonished our contemporaries as much as our forefathers, have been effected solely by its agency. It is not, of course, our intention to teach our readers chemistry in all its branches, but merely to direct the inquiring mind of youth to skim lightly and agreeably over its surface; for which purpose we have selected a series of experiments for their amusement. For those who wish to be instructed as well as amused, we have added some explanations of the decompositions, or chemical changes, which take place, in order to show that, although almost magical in appearance, they are dependent upon some fixed and unerring law of Nature. Without any further prefatory observations, we shall now commence our chemical recreations.
1.—Dissolve one ounce of sulphate of soda (Glauber's salts) in two ounces of boning water; pour it, while hot, into a phial, and cork it close. In this state, it will not tryatallize when cold; but if the cork be removed, the crystallization will commence and proceed rapidly.
The experiment will occasionally fail under unfavourable circumstances. Should this be the caso, drop into the fluid a crystal of Glauber's salt, and the whole will immediately commence shooting into beautiful crystals.
2.—Repeat the above experiment with a small thermometer immersed in the solution, and corked up with it. When cold, remove the cork, and the thermometer will be seen to rise. This experiment shows that heat is given out in the act of crystallization.
3.—Take half an ounce of common soda and dissolve it in about its own weight of water; then pour into the solution half an ounce of sulphuric acid (oil of vitriol). When the mixture is cold, crystals of sulphate of soda will be found in the liquor.
4.—Take common soda, and pour upon it muriatic acid; this will produce muriate of soda, our common table salt.
6.—Take carbonate of ammonia (the common volatile smelling salts), and pour upon it muriatic acid until the effervescence ceases. The produce' will be a solid salt, viz., nmrintc of ammonia, or crude sal ammoniac.
0.—Mix two ounces of oxide of lead (litharge) with three drachms of muriate of ammonia, find submit the whole to a strong heat in a crucible. The heat will drive off the ammonia, and the muriatic acid will combine with the load, forming a muriate of lead. When the operation is complete, pour the ingredients into a metal vessel to cool and crystallize. This is the patent yellow used by painters.
In this experiment the lead is dissolved by the muriatic acid, which has been disengaged by the heat driving off the ammonia with which it was previously combined.
Allan Baskets.—Make a small basket, about the size of the hand, of iron wire or split willow; then take some lamp-cotton, untwist it, and wind it round every portion of the basket. Then mix alum, in the proportion of one pound with a quart of water, and boil it until the alum is dissolved. Pour the solution into a deep pan, and in the liquor suspend the basket, so that no part of it touch the vessel, or be exposed to the air. Let the whole remain perfectly at rest for twenty-four hours; when, if you take out the basket, the alum will be found prettily crystallized over all the limbs of the cottoned frame. In like manner, a cinder, a piece of coke, the sprig of a plant, or any other object, suspended in the solution by a thread, will become covered with beautiful crystals. If powdered turmeric be added to the hot solution the crystals will be of a bright yellow ; if litmus bo used instead, they will be of a bright red ; logwood will yield them of a purple, and common writing ink of a black tint; or, if sulphate of copper be used instead of alum, the crystals will be of fine blue. But the coloured alum-crystals are much more brittle than those of pure alum, and the colours fly; the best way of preserving them is to place them under a glass shade, with a saucer containing water; this keeps the atmosphere constantly saturated with moisture, the crystals never become too dry, and their texture and colour undergo but little change.
A Group of various Coloured Crystals.—Take half an ounce each of the sulphates of iron (groon vitriol), copper (blue vitriol), zinc (white vitriol), soda, alumine (alum), magnesia (Epsom salts), and potash; dissolve these salts in separate vessels, and afterwards pour them altogether into a large vessel and allow them to remain at rest until by the evaporation of the water the different salts again begin to crystallize; and when the water has evaporated, and the crystals are dry, the appearance will be extremely beautiful, in consequence of the various colours which will be found intermingled.
Beautiful Crystals of Bismuth.—Having melted a quantity of the metal bismuth in an iron ladle, remove, by means of knife or otherwise, the dross or scum that floats on the top, then allow it to rest until a crust of hard metal is formed on the surface; as soon as that is the case, make a hole in the edge of this crust, and pour off the metal that still remains fluid in the centre of the mass; when it is entirely cold, remove the upper crust by means of a file, and if the experiment has been properly performed, the inside of the mass will be found covered with a beautiful group of crystals of bismuth, sufficiently curious and pleasing to form an interesting mantel-piece ornament.
1.—Write with a diluted solution of muriate or nitrate of cobalt, and the writing will be invisible; but, upon being held to the fire, it will appear perfectly distinct, and of a blue colour: if the cobalt be adulterated with iron, the writing will appear of a green colour. When taken from the fire, the writing will again disappear. If a landscape be drawn, and all finished with common colours except the leaves of the trees, the grass, and the sky, and the latter be finished with this sympathetic ink, and the two former with the adulterated solution just mentioned, the drawing will seem to be uifc finished, and have a wintry appearance; but, upon being held to the fire, the grass an( the trees will become green, the sky blue, and the whole warm and beautiful.
2.—Write with a diluted solution of muriate of copper, and the writing will be invisible when cold; but upon being held to the fire it will appear of a yellow colour. A landscape may be drawn and finished, as in the hut experiment, and, in addition tu the sympathetic inks there used, corn-fields may be painted or finished with the above ink. The whole will have a very drear and bleak aspect till held before a fire, when it will instantly assume a cheerful and lively appearance, as if by magic.
3.—Write with a weak solution of alum in lemon-juice, and the characters will remain invisible until wetted with water, which will render them of a greyish colour, and quite transparent. A letter written with a solution of rock-alum alone, being dried, and having a small quantity of water poured over it-, the writing will appear of a whiter colour than the paper.
4.—Write with a weak solution of sulphate of iron (green vitriol); when dry it will be invisible i but if wetted over with a brush, dipped in tincture of galls, or a strong decoction of oak-bark, the writing will appear black.