Chapter 7

Time in Acquired Squares Total Ratio of Descent in Thousandths Velocity, of the Descent, Spaces, Each Successive of an Hour. Cubits. Time. Cubits. Interval of Intervals, Time. Cubits.

1 200 1 100 1 100 2 400 4 400 3 300 3 600 9 900 5 500 4 800 16 1,600 7 700 5 1,000 25 2,500 9 900 6 1,200 36 3,600 11 1,100 7 1,400 49 4,900 13 1,300 8 1,600 64 6,400 15 1,500 9 1,800 81 8,100 17 1,700 10 2,000 100 10,000 19 1,900

So that-- Cubits. Acre Sides. In 1/10,000 of an hour, the total descent = 1 = 1/100

In 1/1000 of an hour, the total descent = 100 = 1

In 1/100 of an hour, the total descent = 10,000 = 100

And so on, in strict _decimal_ relation with the earth's semi-polar axis.

A two-fold reason why the constant for latitude 45° is vastly better than any other, is in its having this simple relation with the semi-axis, and at the same time a less complex way of applying the correction for latitude.

JACOB M. CLARK.

New York, February, 1885.

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ORIGIN OF THUNDERSTORMS.

At the recent congress of German medical men and physicists, Dr. S. Hoppe, of Hamburg, read a paper in which he sought to show that the electricity of thunderstorms is generated by the friction of vapor particles generated by the evaporation of water. This opinion was strengthened by several experiments in which compressed cold air was allowed to rush into a copper vessel containing warm moist air, thus generating a large amount of electricity. He concludes that the rise of a column of warm moist air into the colder atmosphere above will be followed by a thunderstorm if it acquires sufficient velocity to prevent neutralization of the electricity generated by the friction of the air. Hence, in his opinion, open districts denuded of forests are more liable to thunderstorms than wooded regions, where the trees forbid the rise of humid air currents.

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IMPROVISED TOYS.

Do our readers remember all those ingenious toys which our mothers and sisters improvised in order to amuse us? We took a walk into the country, and our eldest sister or our mother picked a wild poppy, turned its red petals back and encircled them with a thread, and stuck a sprig of grass into the seed vessel to represent a headdress of feathers. Here was a fresh and pretty doll (Fig. 1). Another day it was the season of lilacs. The children gathered branches by the armful, and from these the mother picked off the flowers and strung them one by one with a needle. Here was a bracelet or a necklace. An acorn was picked up in the woods, the mother carved it with a pen-knife, and behold a basket. From a nutshell she made a boat, and from a green almond a rabbit. Sometimes she carved the rabbit's ears out of the almond itself, but in most cases they were made from a pretty rose-colored radish.

Do you remember the cork from which, by the aid of a few long needles for bars, an ingenious fly-cage was formed? And the castle of cards, four, five, and eight stories high? And then those famous card tents in a row, that fell one after another when the first one in the line was overturned?

How we passed the evenings with our eyes fixed upon our mothers, who patiently, with their skillful scissors, cut horses and dogs out of old white, red, and blue cards! And how many plays, without costing a cent, served to amuse the children by exercising their ingenuity! The mother marked at hazard five dots upon a sheet of paper. The question was to draw a man, one of the dots showing the place of the head and the other four the feet and hands.

When the dessert was brought upon the table, it became a question of manufacturing a head out of an orange. That is not very difficult; two holes for the eyes, a large slit for the mouth, and nothing easier than to simulate the teeth and nose. The head was placed upon a napkin stretched over the top of a champagne glass. This was one of our great amusements. The napkin was drawn ultimately to the right and left, and this moved the head and caused it to assume most comical positions. But what caused irresistible laughter was when a sly hand pressed the head and made it open its mouth wide. And then what pigs we manufactured with a lemon perched upon four matches!

Without mentioning Chinese shadows, how many cheap amusements there are that can be varied to infinity merely by various combinations of the fingers interlocked in diverse manners!

All such amusements were much in vogue in former times, but we are assured that to-day mothers are less conversant with these curious and droll inventions, which were once transmitted like the tales of Mother Goose. They buy playthings for their children at great expense, and allow the latter to amuse themselves all by themselves. The toy paid for and given, the child is no longer in their mind. Those mothers who have preserved the traditions of these little pastimes, and know how to skillfully vary them, find therein so many resources for amusing their children. Then it is so pleasant to see the eyes of the latter eagerly fixed upon the scissors, and to hear their exclamations of pleasure and their fresh laughter when the paper is transformed under expert fingers into a boat, house, or what not!

It has required millions of mothers and nurses to put their wits to work to amuse their children in order to form that collection of charming combinations that at present constitutes a sort of science. Mr. Gaston Tissandier not long ago conceived the happy idea of bringing together in an illustrated volume a description of some of these improvised toys and amusing plays, and it is from this that the accompanying illustrations (which sufficiently explain themselves) are taken.

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THE ÆOLIAN HARP.

The Æolian harp is a musical instrument which is set in action by the wind. The instrument, which is not very well known, is yet very curious, and at the request of some of our readers we shall herewith give a description of it.

According to a generally credited opinion, it is to Father Kircher, who devised so many ingenious machines in the seventeenth century, that we owe the first systematically constructed model of an Æolian harp. We must add, however, that the fact of the spontaneous resonance of certain musical instruments when exposed to a current of air had struck the observers of nature in times of remotest antiquity.

Without dwelling upon the history of the Æolian harp, we may say that in modern times this instrument has been especially constructed in England, Scotland, Germany, and Alsace. The Æolian harp of the Castle of Baden Baden, and those of the four turrets of Strassburg Cathedral are celebrated.

We shall first describe Kircher's harp, which this Jesuit savant constructed according to an observation made by Porta in 1558. The instrument consists of a rectangular box (Fig. 1), the sounding board of which, containing rose-shaped apertures, is provided with a certain number of strings stretched over two bridges and fastened to pegs at the extremities. This box carries a ring that serves for suspending it. Kircher recommends that the box be made of very sonorous fir wood, like that employed in the construction of stringed instruments. He would have it 1.085 meters in length, 0.434 meter in width, and 0.217 meter in height, and would provide it with fifteen catgut strings, tuned, not like those of other instruments to the third, fourth, or fifth, but all in unison or to the octave, in order, says he, that its sound shall be very harmonious. The experiments of Kircher showed him the necessity of employing a sort of concentrator in order to increase the force of the wind, and to obtain all the advantage possible from the current of air that was directed against the strings. The place where the instrument is located should not, according to him, be exposed to the open air, but must be a closed one. The air, nevertheless, must have free access to it on both sides of the harp. The force of the wind may be concentrated upon such a point in different ways; either, for example, by means of conical channels, or spiral ones like those used for causing sounds to reach the interior of a house from a more elevated place, or by means of a sort of doors. These latter, two in number, are adapted to a kind of receptacle made of boards and presenting the appearance of a small closet. In the back part of this receptacle there is a slit, and in front of this the harp is hung in a slightly oblique position. The whole posterior portion of the apparatus must be situated in the apartment, while the doors must remain outside the window (Fig. I). In later times the Æolian harp has been improved by Messrs. Frost and Kastner, whose apparatus is represented in Fig. 2. It consists of a rectangular box with two sounding boards, each provided with eight catgut strings. In order to limit the current of air and to bring it with more force against the strings, two wings are adapted near the thin surfaces opposed to the wind, so that the current may reach each group of cords on passing through the narrow aperture between the obliquely inclined wing and the body of the instrument. The dimensions of the resonant box are as follows: height, 1.28 meters; width, 0.27 meter; and thickness, 0.075 meter. Distance between the two bridges, or length of the sonorous portion of the cords, about 1 meter; width of the wings, 0.14 meter. Distance between the sounding board and the wings, 0.42 meter. Inclination of the wings, 50 degrees.

The celebrated Æolian harps of the old castle of Baden Baden are entirely different, and merit description. One of them (Fig. 3) is formed of a resonant box, the construction of which differs from that of Æolian harps with a rectangular box, in that it is prolonged beyond the place occupied by the strings, and is rounded off behind. In the opposite side there are two long and narrow apertures. To prevent the apparatus from being injured by the weather, it is inclosed in a sort of case occupying the recess of the window in the old ruined castle in which it is exposed. Behind the harp there is a wire lattice door, the purpose of which seems to be to protect the instrument against the attempts of robbers or the indiscreet contact of tourists. We annex to the general view of the instrument a front and profile plan (Fig. 4). The Æolian harp has often inspired both writers of prose and poetry. Chateaubriand, in _Les Natchez_, compares its sounds to the magic concerts that the celestial vaults resound. Without attributing such effects to the instrument, it must be admitted that it possesses remarkable properties, which act upon the nervous system and cause very different impressions, according to the temperament of those who listen to its accords.

Hector Berlioz, in his _Voyage Musicale en Italie_, has given as follows the curious effects that an Æolian harp produced upon his lively and impassioned imagination: "On one of those gloomy days that sadden the end of the year, listen, while reading Ossian, to the fantastic harmony of an Æolian harp swinging at the top of a tree deprived of verdure, and I defy you not to experience a profound feeling of sadness and of _abandon_, and a vague and infinite desire for another existence."

An English physician, Dr. J.M. Cox, in his practical _Observations_ upon dementia, asserts that unfortunate lunatics have been seen whose sensitiveness was such that ordinary means of cure had to be given up with them, but who were instantly calmed by the sweet and varied accords of an Æolian harp. Other observers narrate that they have heard the efficacy of Aeolian sounds spoken of in Scotland for producing sleep.

Telegraph wires are often, under the influence of the winds, submitted to vibrations which reproduce the phenomena of the Aeolian harp. The electric telegraph, which, before the construction of the Kehl bridge, directly traversed the Rhine, very frequently resounded, and the observer who placed his ear against the poles on the bank of the river was enabled to hear something like a far-off sound of bells.--_La Nature_.

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PHYSICS WITHOUT APPARATUS.

MANUFACTURE OF ILLUMINATING GAS.

Burn a piece of paper of about the size of the hand upon a clean porcelain plate, and this will serve to show the phenomena of carbonization and the formation of empyreumatic products under the action of heat. Under the burned paper there will be found a yellowish deposit which sticks to the fingers, and which consists of oil of paper produced by distillation. An idea of the production of illuminating gas through the distillation of coal may be easily given by means a single clay pipe. Upon filling the bowl of this with fragments of coal, closing the opening with clay, and, after the latter is dry, placing the bowl in a coal fire so that the stem shall project, gas will soon be observed issuing from, the latter, and, when lighted, will give a very bright flame. If the pipe seems to be a little too costly, recourse maybe had to a large piece of wrapping paper rolled into the form of a cornucopia, and held in the left hand by means of the pointed end. If, after an aperture has been made in this near the point, the base be lighted, the heat developed by the flame will produce a sort of distillation of the organic matter of the paper, and the empyreumatic and gaseous products will rise in the cone, and make their exit through the orifice, where they may be lighted with a match (Fig. 1). It goes without saying that this experiment lasts but a few seconds; but, as short as this period is, it is sufficient to give a demonstration of the production of illuminating gas through the distillation of organic matters. Care should be taken not to set anything on fire while performing it, and it is well to operate over a pavement, and far from any inflammable materials.

ELASTICITY OF BODIES.

Mould a piece of fresh bread with the fingers so as to give it the size and shape shown in Fig. 2. If this object be placed upon a wooden table, and a hard blow be given it with the fist, it will be found impossible to put it permanently out of shape. However hard be the blow, the elastic material, although flattened for an instant, will always resume its original form. If the object be thrown on the floor with all one's might, the result will be the same; its elasticity will always cause it to spring back to its original form. The experiment will only succeed when the bread that is used is very fresh and soft.

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SCIENTIFIC AMUSEMENTS.

_The Dance of the Electrified Puppets_.--We have already pointed out a means of obtaining electrical manifestations without recourse to a machine, and shall now describe a very easily performed experiment--the dance of the electrified puppets.

Procure a pane of glass about 10 inches in width and 14 in length, and support it between two large books, as shown in Fig. 1. The glass must be inserted in the books in such a way that it shall be an inch and a fraction above the surface of the table. Then, with a pair of scissors, cut out of a piece of tissue-paper a number of figures, such as men, women, clowns, frogs, etc. These little figures must not exceed three-quarters of an inch in length. We show some of actual size in Fig. 1. They may be cut out of papers of different colors, so as to give variety to the scene. After they are prepared they are to be placed in the ball-room, that is to say, in the space between the books, glass, and table. They should be laid flat upon the table, and alongside of one another. Now rub the upper surface of the glass vigorously with a piece of silk or woolen, and, in a few instants, the figures will be attracted by the electricity, and suddenly stand up straight and jump up to the transparent ceiling of their ball-room. Then they will be repelled, and again attracted, and thus keep up a lively dance. When the rubbing is stopped, the dance continues spontaneously for some little time, and even the contact of the hand suffices to animate the figures. In order that this experiment shall prove a success, the glass used must be very dry, as well as the fabric with which it is rubbed. If the latter be warmed, the manifestation will be more rapid and energetic. Silk answers better than woolen.

_Silhouette Portraits_.--Take a large sheet of paper, black on one side and white on the other, and affix it to the wall, white surface outward, by means of pins or tacks. Place a very bright light upon the table, at a proper distance, and allow the person whose portrait it is desired to form to stand between it and the wall (Fig. 2). Then, with a pencil, draw the outlines of the shadow projected. While this is being done, it is very necessary that the subject shall keep perfectly immovable. When the outlines are sketched, remove the paper from the wall and cut out the portrait. After this, all that remains to be done is to turn the portrait over and paste it to a sheet of white paper. The silhouette is profiled in black, and if the operation be skillfully performed, the resemblance will be perfect.--_La Nature_.

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HOW TO BREAK A CORD WITH THE HANDS.

Our readers have often seen grocers' clerks or employes of business houses break the string with which they had tied up a package, by seizing it with the hands, bringing the latter close together, and then suddenly separating them with a quick movement. If it be thought that this quick motion is sufficient, let any one try it, and he will merely cut his hands without breaking the string, provided the latter has some little strength. In order to succeed, the cord must be arranged in a certain manner, as we shall explain.

The cord to be broken is placed upon the left hand, and one of its ends is passed over the other in such a way as to form a cross, and the end forming the shorter part of the cross is wound around the fingers (it should be left long enough to make several turns). The other end is then turned back and wound around the right hand, so as to leave a space of about eighteen inches between the latter and the left hand. If these directions are properly followed, the string should have the form of a Y in the middle of the hand, as shown in the lower figure of the accompanying engraving.

It is only necessary after this to close the hand, after seeing that the Y is very taut, and to seize the cord with the other hand, as shown in the upper figure. This done, the two hands are brought together and then suddenly separated so as to give a quick pull on the point of junction of the Y-shaped branches, which form a true knife. It will be readily seen that as the cord is broken suddenly the shock does not have time to transmit itself to the hands. This is an interesting demonstration of the principle of inertia.

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AN AQUATIC VELOCIPEDE FOR DUCK HUNTING.

The curious apparatus that we represent in Fig. 1, from an old English engraving of 1823, is an aquatic velocipede which was utilized with success during the entire winter of 1822. An amateur employed it for hunting ducks upon the numerous streams of Lincolnshire, and, as it appears, obtained very good results from it. The device is very ingenious. It consists of three floats of from 1,800 to 2,000 cubic inches capacity, made of copper or tin plate. These are full of air, and must be perfectly tight. They are held together by arched iron rods, as shown in the cut, so as to form the three angles of an isosceles triangle. These rods are provided in the center with a saddle for the velocipedist to sit upon. The apparatus floats upon the water and sustains the hunter, whose feet are provided with quite short paddles, by means of which he navigates, and steers himself.

The amusing engraving of this velocipede, which is mentioned under the name of the _aquatic tripod_, puts us in mind of another document of the same kind that we have seen in the gallery of prints of the National Library. It is a naively drawn lithograph representing a trial of velocipedes in the Luxembourg Garden, at Paris, in 1818. In Fig. 2 we give a reduced copy of it. It will be seen that in 1818 velocipedes were made of wood and were provided with two wheels--one in front, and the other behind. The propelling was done by alternately placing the feet on the ground.

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A SUNSHINE RECORDER.

The apparatus is of simple construction. It consists of a glass sphere silvered inside and placed before the lens of a camera, the axis of the instrument being placed parallel to the polar axis of the earth. The whole arrangement will be readily understood by an inspection of Fig. 1. The light from the sun is reflected from the globe, and some of it, passing through the lens, forms an image on a piece of prepared paper within the camera. In consequence of the rotation of the earth, the image describes an arc of a circle on the paper, and when the sun is obscured, this arc is necessarily discontinuous. The image is not a point, but a line, and in certain relative positions of the sphere, lens, and paper, the line is radial and very thin, so that the obscuration of the sun for only one minute is indicated by a weakening of the image.