Chapter 9

By placing one end of the bar magnetized by the solenoid near the compass contained by the cabinet (Fig. 7) it will be seen that one end of the compass needle is attracted. When the opposite end of the bar is presented to the same end of the needle, that end of the needle will be repelled and the opposite one attracted, showing that like poles repel each other while unlike poles attract.

GALVANOMETER.

By placing one of the coils, A, in the block, D, then placing in the cavity in the top of the block the compass, with the line marked N S arranged at right angles to the axis of the coil, a serviceable galvanometer will be formed (Fig. 8). By turning the galvanometer so that the needle will point north and south without the current passing, with N underneath one end of the needle, and then connecting the poles of the battery with the terminals of this galvanometer, a deflection of the compass needle will be produced, the direction of which depends upon the direction of the current.

EXPERIMENTS SHOWING THE EFFECTS OF RESISTANCE.

By placing the galvanometer in the circuit of the battery, as shown in Fig. 9, and noting the deflection of the needle, it will be ascertained that a certain amount of current is flowing. Now, by placing in the circuit, in addition to the galvanometer, the remaining coil of the magnet, thus introducing considerable resistance, the current will be diminished, as shown by a smaller deflection of the needle.

RESISTANCE OF A FLUID CHANGED BY THE ADDITION OF ANOTHER FLUID.

A very pretty and instructive experiment may be performed by arranging the apparatus as shown in Fig. 10, with the copper strips, H H, inserted in clean water and the galvanometer placed in the circuit. The deflection of the galvanometer needle will be very slight, showing that the resistance of clean water is considerable. A few drops of sulphuric acid or even vinegar will increase the conductivity of the water so as to produce a marked deflection of the galvanometer needle.

Common salt added to the water will produce the same effect.

MAGNETIC ELECTRIC INDUCTION.

By placing one of the coils, A, on the magnet frame, B, and connecting it by the wires with the galvanometer, arranged as before described, and bringing the permanent magnet, F, suddenly against the poles of the magnet, as shown in Fig. 11, a current will be induced in the coil, which, in passing through the galvanometer, causes the needle to be deflected in one direction, and when the permanent magnet is suddenly removed from the electro-magnet, a current will be set up in the opposite direction, which will cause a deflection of the needle of the galvanometer in the opposite direction.

INDUCTION COIL.

By placing both coils, A, upon the bundle of soft iron wires, G, connecting one of them with the terminals of the battery, as shown in Fig. 12, and holding the terminals of the other coil in the moistened thumb and fingers of the two hands, when the battery circuit is opened and closed by touching one of the wires to the battery, and removing it, a slight shock will be felt from the coil which is disconnected from the battery. By placing a coarse file in the circuit and drawing one of the terminals along the file the circuit will be rapidly interrupted. This shock is due to the current induced in the detached coil by the magnetism of the bundle of wires.

EXTRA CURRENT.

An experiment showing the extra or self-induced current consists in arranging the motor as shown in Fig. 6, and connecting wire with each conductor leading from the battery to the motor, as shown in Fig. 13. If these wires are grasped one in each hand while the motors is in motion, a slight shock will be felt, providing the hands are moistened.

TELEGRAPH SOUNDERS AND KEYS.

The cabinet contains material for two telegraph sounders and keys which will enable the user to establish a short telegraph line with a single cell of battery. The armature, m, may be lifted from its pivot so as to permit of slipping one of the coils, A, on to the round magnetic core of the sounder. The armature is then replaced, as shown in Fig. 14, and the small retractile spring at the rear of the instrument is arranged to draw down the shorter arm of the armature lever. One of the terminals of the coil, A, is connected with the turned up pivoted end of the telegraph key, o, on the same base. The other terminal is connected with one pole of the battery and the contact point of the key is connected with the other pole of the battery, as shown. By swinging the key laterally, so as to remove it from the contact point, it will be found that every touch of the key produces a movement of the sounder lever. To connect the two instruments together upon a line, it is only necessary to connect the two keys with one wire and the terminals of the two coils with another wire, cutting one of these wires and inserting the battery.

As soon as the operator ceases to work his instrument he should place the key in contact with the contact point, and cause it to remain there by slipping the end of the key under the head of the screw provided for that purpose. The other operator can then proceed to send his message.

Those who desire to practice telegraphy should learn the Morse telegraphic code.

MAGNETIC FIGURES.

By arranging the coil so as to form an electro-magnet, as before described, and holding the magnet under a plate of glass sprinkled with fine iron filings, as shown in Fig. 15, and then sending a current through the magnet, at the same time jarring the glass by striking it with a lead pencil, a magnetic figure will be formed which is sometimes called the magnetic spectrum. By connecting the terminals of the coils diagonally with each other, and connecting the remaining terminals with the battery, two like poles will be formed, and the magnetic figures will have an entirely different appearance, owing to the repulsion between the two like polarities. Different figures may be produced by using the solenoids without the iron cores.

EXPERIMENT SHOWING THE CURRENT.

By removing the coil, A, from beneath the compass, E, and connecting the ends of the transverse wire, a' a', with the battery Fig. 16, then lifting the plates of the battery out of the solution and allowing the needle to come to rest, it will be found upon inserting the plates of the battery in the solution, very gradually, that the deflection of the needle will increase with the increase of plate surface submitted to the action of the battery fluid; and if, when the greatest deflection is reached, the coils or solenoids are introduced into the circuit, one after the other, it, will be found that each added coil diminishes the current, as will be shown by the diminished deflection of the needle.

MICROPHONE AND TELEPHONE.

Take two small carbon rods, p p, if procurable, if not, use two ordinary nails, and connect them up in the circuit of the battery; lay them upon a thin box so that the rods or nails cross each other, as in Fig. 17; insert the electromagnet in the circuit; move the coils out a little beyond the ends of the cores, lay a thin iron plate over the ends of the coils, then jar the box upon which the bars, p p, are laid, or drop a pin upon it, or scratch it with a piece of paper, and the sound will be heard by placing the ear against the iron plate resting upon the coils of the magnet.

ELECTRO METALLURGY.

Dissolve an ounce of sulphate of copper in a half pint of water; add a few drops of sulphuric acid; connect with the zinc pole of the battery the object to be coppered. To the wire connected with the carbon attach a small plate of copper. Hang the object and the copper plate in the solution a short distance apart. A deposit of copper will be quickly formed.

THE HEATING EFFECT OF THE CURRENT.

With a piece of very fine platinum wire (No. 36 or 40), placed in the circuit of the battery, the heating effect of the current may be shown. A half inch of No. 36 platinum wire will serve for the experiment. If the battery is in good condition it will heat from 1/8 to 1/4 inch of the wire red hot. This is sufficient to light gas or an alcohol lamp, also to ignite powder or gun cotton.

A short piece of a watch hair spring, or a piece of very fine iron wire, if placed in the circuit will be made very hot.

DUPLICATION OF BATTERIES.

Should the experimenter desire to go more deeply into the effects of the current, he will need a more powerful battery. The battery described has been made on a very simple plan, to enable the amateur to copy it without difficulty or great expense. There is no mystery about the battery. Any one can make it. All that is required is a plate of zinc, two plates of carbon, some strips of wood and copper, and two common wood screws for each cell. The tumblers may be had anywhere.

Although it is advisable to use insulated wire for making the electrical connections, bare wires may be used if care is taken in arranging them, so that they will not touch each other or other metallic objects which would complete the circuit.

It will be found convenient if the elements of the battery are arranged upon a frame of some sort, by means of which they may be raised or lowered all together, and supported at any desired height.

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THE ACTION OF THE SILENT DISCHARGE ON CHLORINE.

Arguing from the fact that oxygen gas, when subjected to the silent discharge, partially undergoes condensation into ozone, it seemed possible, says Mr. H.M. Vernon, in the _Chemical News_, that other elementary gases, as chlorine and bromine vapor, might undergo an analogous change when subjected to the same treatment. A glass tube, with a U-shaped index of fine bore glass tubing, was filled with purified and dried chlorine. After passing a current of the gas through the tube for some time, the end was sealed in the blowpipe flame. The tube was then warmed slightly, and a few bubbles of gas thus driven out. The end of the index tube dipped under strong sulphuric acid saturated with chlorine gas, so that, on cooling, a short column of the acid was drawn up. This served as an index for any changes of volume which might take place in the chlorine in the tube. A silent discharge of electricity was then passed. The volume of the gas was observed to increase slightly, but afterward it remained quite constant, even after the discharge had been passed for several hours. We may therefore conclude that no allotropic change takes place when chlorine gas is subjected to the silent discharge of electricity, the initial increase of volume being merely due to the heating effect the discharge has upon the gas. Into another similar tube, filled with chlorine, was introduced a small quantity of liquid bromine.

The tube thus contained chlorine saturated with bromine vapor. The silent discharge on being passed through this tube did not produce any different effect than for chlorine alone. So we may conclude that bromine vapor also does not undergo any allotropic condensation when subjected to the influence of a silent discharge of electricity. The fact that oxygen gas is capable of undergoing condensation while chlorine and bromine are not is easily explained. The oxygen atom, being divalent, is capable of uniting itself to two other atoms of oxygen or other elements, and thus with oxygen forming ozone. The atoms of chlorine and bromine, however, being only monovalent, have all their affinity satisfied when they are united to a single other atom of chlorine and bromine. It is not possible, therefore, that condensation can take place if the atoms remain monovalent. Hydrogen gas and iodine vapor are in a similar manner debarred from undergoing condensation. Mr. Vernon, therefore, comes to the conclusion that it is most improbable that any other element but oxygen will be found capable of undergoing molecular condensation when in the gaseous state and subjected to the silent discharge.

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ESTIMATING CARBON IN ORGANIC SUBSTANCES.

BY J. MESSINGER.

This is an improvement on the author's method of two years ago. The method is now applicable to compounds with which previously low results were obtained.

The substance is weighed into a small tube 24 mm. long and 11 mm. wide, and is then introduced into the decomposition flask, which contains 6 to 8 grms. of chromic acid, care being taken that the chromic acid does not come into contact with the substance under analysis. The decomposition flask is fitted with a thistle funnel, and is connected to the reversed condenser and apparatus shown in the figure. Fifty c.c. of concentrated sulphuric acid are run into the flask. During the whole of the operation a gentle current of air (free from carbon dioxide) is passed through the apparatus. The asbestos plate underneath the flask is then warmed, and thus the flask and contents are warmed by radiant heat from the plate alone until the sulphuric acid darkens. At this point, where decomposition of the organic substance begins, the flame is entirely removed. The carbon dioxide (with some carbon monoxide) passes through the condenser and then over a heated mixture of copper oxide and lead chromate contained in a tube 15 cm. long. The gas (CO2) then passes through a U-tube, in one limb of which is sulphuric acid, in the other glacial phosphoric acid.

Thus dried it passes through weighed potash bulbs, after which is placed for safety a small tube containing soda lime and phosphoric acid. After the lapse of about twenty minutes, warming may be once more proceeded with in the same manner as before, and after about two and one-half hours the asbestos plate may be placed directly below the flask, and more strongly heated. The whole operation is very easily carried out, and needs no watching.

With substances containing halogens, it is advisable to place, after the copper oxide tube, a small washing flask containing potassium iodide solution.

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NEW RACE OF DWARF DAHLIAS.

The dahlia has held a prominent place among garden flowers for many years, and it has received new life in the acquisition of a section little expected by cultivators, but peculiarly welcome. This class is the outcome of much patient work on the part of Mr. T.W. Girdlestone, the well known secretary of the National Dahlia Society, who has for some time past devoted much time to the improvement of the single varieties. We had the pleasure a short time since of receiving a photograph of this dwarf section of dahlias from Messrs. J. Cheal & Sons, of Crawley, who have purchased the stock, and this we have had engraved, as it conveys an excellent idea of the height of the plant and the profusion with which the flowers are produced. The photograph was also of interest as containing a portrait of Mr. Girdlestone, which we are sure will be welcome to many of our readers. The plants of this race are very dwarf, not exceeding twelve inches in height, bushy, spreading and exceedingly free in flowering, the range of varieties being at present limited to twelve. The blooms are of medium size, and the colors are distinct and rich, more particularly the scarlet and crimson shades, which can be employed to immense advantage in the flower garden. The heavy formal show varieties are of little value for planting in trim beds and borders. Many of the decorative or cactus varieties are too coarse in growth to be of much value in the flower garden. Therefore, this Liliputian race should find favor with those who wish for showy and novel effects in the garden during the summer months.

There are no peculiarities of culture to contend with, and the unusually dwarf habit of the plants specially fits them for comparative small beds and borders. One good way would be to fill a single bed with one or more decided colors, as is now done with the tuberous begonia, for the reason that these dahlias have flowers similar in size to those of the tall-growing single varieties, and bear them on stiff stalks well above the stems. A mass of the crimson variety would produce a rich glow of color infinitely finer than a mixture of undecided hues. We anticipate a high degree of popularity for these dwarf single or Tom Thumb dahlias, and there is a possibility of double varieties equally dwarf which would be also welcome. The great fault of the majority of dahlias already in cultivation is the tall habit of the plants, but here we have dwarfness, a profusion of finely formed flowers, and varied and attractive colors.--_The Gardeners' Magazine_.

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SOME WINNEBAGO ARTS.

In the Proceedings of the New York Academy of Sciences an abstract is given of a paper on the above, read by Dr. Frederick Starr:

It is well known that a tribe may have peculiarities in speech, in manners, in arts, that distinguish it at once from its neighbors. The Haida carves slate as no other tribe does. The elegant blankets of mountain sheep wool from Chilcat are characteristic. The Hebrews tested the enemy with the word _shibboleth_, and found that he could only say _sibboleth_. A twist of the tongue in pronouncing a word is a small matter, but, small as it is, it may be perpetuated for ages.

Such a perpetuation of a tribal peculiarity has been aptly called an ethnic survival. Some of the advanced linguists of the present day are beginning to query whether the group of modern languages of the Aryan family are not examples of such ethnic survival; whether the differences between French and Italian and Spanish, Latin, Greek and Slavonic, are not due to the difficulty various ancient tribes found in learning to speak the same new and foreign language. To draw an example of ethnic survival from another field of science, consider the art of the French cave men. The archæologist finds in the caverns bones of various mammals, teeth of cave bear, and antlers of reindeer carved with animal figures. The art is _good_ for a barbarous people, but it is certainly barbarian art. The range of designs is quite great: horses, bears, mammoths, reindeer, are among the figures. The people who did this work were an artistic people. To carve and represent animal forms was almost a mania with them. An ethnic impulse seems to have driven them on to such work, just as a similar impulse drives the Haida slate carver to-day; just as a similar impulse has driven the Bushman to cover the walls of his caves in South Africa with pictures whose boldness and fidelity are the amazement of all who see them.

We have, then, in the French cave dwellers a people who had a well defined art, and who, as art workers, were isolated and unlike all neighbors. An eminent English scientist believes that neither they nor their art are gone. There is a people who to-day lives much as a cave man of France lived so long ago, who hunts and fishes as he did, who dresses as he did, who builds houses in whose architecture some think they can see evidence of a cavern original, who above all still carves batons from ivory, and implements from bone, adorning them with skillfully cut figures of animals and scenes from the chase. This people is the Eskimo. If Dawkins' view is true, we have in the Eskimo carvings of to-day a true ethnic survival--an outcropping of the same passion which displayed itself in the mammoth carving of La Madelaine.

Scarcely anything in the range of American antiquities has caused more wonder and led to more discussion than the animal mounds of Wisconsin. We do not pretend to explain their purpose. Perhaps they were village guardians; perhaps tribal totems marking territorial limits; some may have been of use as game drives; some may even have served as fetich helpers in the hunt, like the prey gods of Zuñi. We may never know their full meaning. It is sufficient here for me to remind you what they are and where. They are nearly confined to a belt of moderate width stretching through Wisconsin and overlapping into Minnesota and Iowa. Within this area they occur by hundreds. Dr. Lapham published a great work on the effigy mounds in 1855, in which he gave the results of many accurate surveys and described many interesting localities. Since his time no one has paid so much attention to the effigies as Stephen D. Peet, editor of the _American Antiquarian_, whose articles have during this year been presented in book form. Mr. Peet has paid much attention to the kind of animals represented, and has, it seems to us, more nearly solved the question than any one else. He recognizes four classes of animals--land animals or quadruped mammals, always shown in profile; amphibians, always shown as sprawling, with all four feet represented; birds, recognized by their wings; and fishes, characterized by the absence of limbs of any kind. The land animals are subdivided into horned grazers and fur bearers. Of the many species he claims to find, it seems to us the most satisfactorily identified are the buffalo, moose, deer, or elk; the panther, bear, fox, wolf and squirrel; the lizard and turtle; the eagle, hawk, owl, goose and crane; and fishes. One or two man mounds are known, although most of those so-called are bird mounds--either the hawk or the owl. Sometimes, too, "composite mounds" are found. Nor are these mounds all that are found. Occasionally the same forms are found _in intaglio_, cut into the ground instead of being built above it, but just as carefully and artistically made. Notice, in addition to the form of these strange earth works, that they are so skillfully done that the attitude frequently suggests action or mood. Nor are they placed at random, but are more or less in harmony with their surroundings. Remember, too, their great number and their large size--a man 214 feet long, a beast 160 feet long, with a tail measuring 320 feet, a hawk 240 feet in expanse of wing.

They are _unique_. To be sure, there are in Ohio three effigies, in Georgia two, and in Dakota some bowlder mosaics in animal form. None of these, however, are like the Wisconsin type. The alligator and serpent of Ohio are different in location and structure from the Wisconsin mounds, and are of designs peculiar. The bird mound in the Newark circle is more like a Wisconsin effigy, but is associated with a type of works not found in the effigy region. The birds of Georgia are different in conception, in material, and in build. The mosaics of Dakota are simply outlines of loose bowlders.

It seems to us that the effigy builders of Wisconsin were a peculiar tribe, unlike their mound-building neighbors in Ohio or the South; that they were a people with a passion for representing animal figures. This passion worked itself out in these earth structures. That a single tribe should be thus isolated in so remarkable a custom is no more strange than that the Haida should carve slate or the Bushman draw his pictures on his cavern walls.

Who were the effigy builders? This is a question often asked and variously answered. Some writers would refer them to the Winnebagoes, or, if not to them directly, to some Dakota stock from which the Winnebagoes have descended.