In the first period of the siege of a stronghold it is of very great importance for the besieged to embarrass the first progress of the attack, in order to complete their own armament, and to perform certain operations which are of absolute necessity for the safety of the place, but which are only then possible. In order to retard the completion of the first parallel, and the opening of the fire, it is necessary to try to discover the location of such parallel, as well as that of the artillery, and to ply them with projectiles. But, on their side, the besiegers will do all in their power to hide their works, and those that they are unable to begin behind natural coverts they will execute at night. It will be seen from this how important it is for the besieged to possess at this stage of events an effective means of lighting up the external country. Later on, such means will be of utility to them in the night-firing of long-range rifled guns, as well as for preventing surprises, and also for illuminating the breach and the ditches at the time of an assault, and the entire field of battle at the time of a sortie.
ELECTRIC LIGHT APPARATUS FOR ARMY USE.
On a campaign it will prove none the less useful to be provided with movable apparatus that follow the army. A few years ago. Lieut. A. Cuvelier, in a very remarkable article in theRevue Militaire Belge, pointed out the large number of night operations of the war of 1877, and predicted the frequent use of such apparatus in future wars.
The accompanying engraving represents a very fine electric light apparatus, especially designed for military use in mountainous countries. It consists of a two-wheeled carriage, drawn by one horse and carrying all the apparatus necessary for illuminating the works of the enemy. The machine consists of the following parts: (1) A field boiler. (2) A Gramme electric machine, type M, actuated directly by a Brotherhood 3-cylinder motor. (3) A Mangin projector, 12 inches in diameter, suspended for carriage from a movable support. This latter, when the place is reached where the apparatus is to operate, may be removed from the carriage and placed on the ground at a distance of about a hundred yards from the machine, and be connected therewith by a conductor. Col. Mangin's projector consists of a glass mirror with double curvature, silvered upon its convex face. It possesses so remarkable optical properties that it has been adopted by nearly all powers. The fascicle of light that it emits has a perfect concentration. In front of the projector there are two doors. The first of these, which is plane and simple, is used when it is desired to give the fascicle all the concentration possible; the other, which consists of cylindrical lenses, spreads the fascicle horizontally, so as to make it cover a wider space.
The range of the concentrated fascicle is about 86,000 feet. The projector may be pointed in all directions, so as to bring it to bear in succession upon all the points that it is desired to illuminate. The 12-inch projector is the smallest size made for this purpose. The constructors, Messrs. Sautter, Lemonnier & Co., are making more powerful ones, up to 36 inches in diameter, with a corresponding increase in the size of the electric machines, motors, and boilers.
The various powers make use of these apparatus for the defense of fortresses and coasts, for campaign service, etc.
The various parts of the apparatus can be easily taken apart and loaded upon the backs of mules. The only really heavy piece is the boiler, which weighs about 990 pounds.
It was known six hundred years before Christ that when amber is rubbed it acquires the power of attracting light bodies. The Greek name for amber,elektron, was afterward applied to the phenomenon. It was also known to the ancients that a certain kind of iron ore, first found at Magnesia, in Asia Minor, had the property of attracting iron. This phenomenon was called magnetism. This is the history of electricity and magnetism for two thousand years, during which these facts stood alone, like isolated mountain peaks, with summits touched and made visible by the morning sun, while the region surrounding and connecting them lay hidden and unexplored.
In fact, it is only in more recent times that men could be found possessing the necessary mental qualities to insure success in physical investigation. Some of the ancients were acute observers, and made valuable observations in descriptive natural history. They also observed and described phenomena which they saw around them, although often in vague and mystical terms.
They, however, were greatly lacking in power to discriminate between the possible and the absurd, and so old wives' tales, acute speculations, and truthful observations are strangely jumbled together. With rare exceptions they did not contrive new conditions to bring about phenomena which Nature did not spontaneously exhibit—they did not experiment. They attempted to solve the universe in their heads, and made little progress.
In mediæval times intellectual men were busy in trying to set each other right, and in disputing and arguing with those who believed themselves to be right. It was an era of intellectual pugilism, and nothing was done in physics. In fact, this frame of mind is incompatible with any marked success in scientific work.
The physical investigator cannot take up his work in the spirit of controversy; for the phenomena and laws of Nature will not argue with him. He must come as a learner, and the true man of science is content to learn, is content to lay his results before his fellows, and is willing to profit by their criticisms. In so far as he permits himself to assume the mental attitude of one who defends a position, in so far does he reveal a grave disqualification for the most useful scientific work. Scientific truth needs no man's defense, but our individual statements of what we believe to be truth frequently need criticism. It is hardly necessary to remark, also, that critics are of various degrees of excellence, and it seems that those in whom the habit of criticism has become chronic are of comparatively little service to the world.
The great harbinger of the new era was Galileo. There had been prophets before him, and after him came a greater one—Newton. They did nothing of note in electricity and magnetism, but they were filled with the true spirit of science, they introduced proper and reasonable methods of investigation, and by their great ability and distinguished success they have produced a revolution in the intellectual world. Other great men had also appeared, such as Leibnitz and Huyghens; and it became very clear that the methods of investigation which had borne such fruit in the days of Galileo were not disposed of completely by his unwilling recantation; it became very clear that the new civilization which was dawning upon Europe was not destined to the rude fate which had overwhelmed the brilliant scientific achievements of the Spanish Moors of a half century before.
Already in 1580, about the time when Galileo entered Pisa as a student, Borroughs had determined the variation of the magnetic needle at London, and we have upon the screen a view of his instrument, which seems rude enough, in comparison with the elaborate apparatus of our times. The first great work on electricity and magnetism was the "De Magnete" of Gilbert, physician of Queen Elizabeth, published in 1600. Galileo, already famous in Europe, recognized in the methods of investigation used by Gilbert the ones which he had found so fruitful, and wrote of him, "I extremely praise, admire, and envy this author."
Gilbert made many interesting contributions to magnetism, which we shall notice in another lecture, and he also found that sulphur, glass, wax, and other bodies share with amber the property of being electrified by friction. He concluded that many bodies could not be thus electrified. Gray, however, found in 1729 that these bodies were conductors of electricity, and his discoveries and experiments were explained and described to the president of the Royal Society while on his death bed, and only a few hours before his death. If precautions are taken to properly insulate conductors, all bodies which differ in any way, either in structure, in smoothness of surface, or even in temperature, are apparently electrified by friction. In all cases the friction also produces heat, and if the bodies rubbed are exactly alike, heat only is produced.
An electrified body will attract all light bodies. This gutta percha when rubbed with a cat's skin attracts these bits of paper, and this pith ball, and this copper ball; it moves this long lath balanced on its center, and deflects this vertical jet of water into a beautiful curve.
If a conductor is to be electrified, it must be supported by bad conductors. This brass cylinder standing on a glass column has become electrified by friction with cat's-skin. My assistant will stand upon this insulating stool, and by stroking his hand you will observe that with his other hand he can attract this suspended rod of wood, and you will hear a feeble spark when I apply my knuckle to his.
Du Fay, of Paris, discovered what he called two kinds of electricity. He found that a glass rod rubbed with silk will repel another glass rod similarly rubbed, but that the silk would attract a rubbed glass rod. We express the facts in the well-known law that like electricities repel each other, and unlike attract. For a long time the nature of the distinctions between the two electricities was not understood. It was found later that when the two bodies are rubbed together they become oppositely electrified, and that the two electricities are always generated in equal quantity; so that if the two bodies are held in contact after the rubbing has ceased the two electricities come together again and the electrical phenomena disappear. They have been added together, and the result is zero. Franklin proposed to call these electricities positive and negative. These names are well chosen, but we do not know any reason why one should be called positive rather than the other. The electricity generated on glass when rubbed with silk is called positive.
Let us now examine the distinction between positive and negative electricities somewhat more closely, aiding ourselves by two cases which are somewhat analogous.
Two air-tight cylinders, A and B, contain air at ordinary pressure. The cylinders are connected by a tube containing an air-pump in such a way that, when the pump is worked, air is taken from A and forced into B. To use the language of the electricians, we at once generate two kinds of pressure. The vessels have acquired new properties. If we open a cock in the side of either vessel, we hear a hissing sound, if a light body is placed before the opening in A it would be attracted, and before the opening in B it would be repelled. Now this is only roughly analogous to the case of the electrified bodies, but the analogy will nevertheless aid us in our study. If the two vessels are first connected with the air, and then closed up and the pump is set to work, we increase the pressure in B and diminish the pressure in A. To do this requires the expenditure of a quantity of work. If the cylinders are connected by an open tube—a conductor—the difference in pressure disappears by reason of a flow of gas from one vessel to the other.
If we had a pump by means of which we could pump heat from one body into another, starting with two bodies at the same temperature, the temperature of one body would increase and that of the other would diminish. If we knew less than we do of heat, we might well discuss whether the plus sign should be applied to the heat or to the cold, because these names were coined by people who knew very little about the subject except that these bodies produce different sensations when they come in contact with the human body.
Furthermore, we find that whether the hand is applied to a very hot body or to a very cold body, the physiological effect is the same. In each case the tissue is destroyed and a burn is produced. Shall we now say that this burn is produced by an unusual flow of heat from the hot body to the hand, or from the hand to the cold body, or shall we say that it is due to an unusual flow of cold from the cold body to the hand, or from the hand to the hot body?
Logically these expressions are identical; still we have come to prefer one of them. It is because we have learned that in those bodies which our fathers called hot, the particles are vibrating with greater energy than in cold bodies, that we prefer to say that heat is added and not cold subtracted, when a cold body becomes less cold.
Now to come back to our electrified bodies. Let us suppose that this gutta percha, and this cat's-skin are not electrified. That means that their electrical condition is the same as that of surrounding bodies. Let us also suppose that their thermal condition is the same as surrounding bodies, ourselves included—that is, they are neither hot nor cold. We express these conditions in other words by saying that the bodies have the same electricalpotentialand the same temperature.
Temperature in heat is analogous to potential in electricity. As soon as adjacent bodies are at different temperatures, we have the phenomena which reveal to us the existence of heat. As soon as adjacent bodies have different electrical potentials, we have the phenomena which reveal the existence of electricity. As soon as adjacent regions in the air are at different pressures, we have phenomena which reveal the existence of air.
Bodies all tend to preserve the same temperature and also the same electrical potential. Any disturbances in electrical equilibrium are much more quickly obliterated than in case of thermal equilibrium, and we therefore see less of electrical phenomena than of thermal. In thunder storms we see such disturbances, and with delicate instruments we find them going on continuously.Changes in temperature occurring on a large scale in our atmosphere, occurring in these gas jets, in our fires, in the axles of machinery, and in thousands of other places, are so familiar that we have ceased to wonder at them.
If we rub these two bodies together, the potential of the two is no longer the same. We do not know which one has become greater, and in this respect our knowledge of electricity is less complete than of heat. We assume that the gutta percha has become negative. If we now leave these bodies in contact, the potential of the cat's skin will diminish and that of the gutta percha will increase until they have again reached a common potential—that of the earth. As in the case of heat and cold, we may say either that this has come about by a flow of positive electricity from the cat's skin to the gutta percha, or by a flow of negative electricity in the opposite direction, for these statements are identical.
In case of our gas cylinders, the gas tends to leak out of the vessel where the pressure is great into the vessel where it is small. The heat tends to leak out of a body of high temperature into the colder one, or the cold tends to go in the opposite direction. Similarly, the plus electricity tends to flow from the body having a high potential, to the body having a low potential, or the minus electricity tends to go in the opposite direction.
[1]Introductory to the course of Lectures on Physics at Washington University, St. Louis, Missouri—Kansas City Review.
[1]Introductory to the course of Lectures on Physics at Washington University, St. Louis, Missouri—Kansas City Review.
[ENGINEERING.]
We have in former articles described the highly interesting series of experimental researches of Dr. C. A. Bjerknes, Professor of Mathematics in the University of Christiania, which formed so attractive a feature in the Electrical Exhibition of Paris in 1881, and which constituted the practical development of a theoretical research which had extended over a previous period of more than twenty years. The experiments which we described in those articles were, as our readers will remember, upon the influence of pulsating and rectilinear vibrating bodies upon one another and upon bodies in their neighborhood, as well as upon the medium in which they are immersed. This medium, in the majority of Professor Bjerknes earlier experiments, was water, although he demonstrated mathematically, and to a small extent experimentally, that the phenomena, which bear so striking an analogy to those of magnetism, may be produced in air.
Our readers will recollect that in the spring of 1882 Mr. Stroh, by means of some very delicate and beautifully designed apparatus, was able to demonstrate a large number of the same phenomena in atmospheric air of the ordinary density; and about the same time Professor Bjerknes, in Christiania, was extending his researches to phenomena produced by a different class of vibrations, namely, those of bodies moving in oscillations of a circular character, such, for example, as a cylinder vibrating about its own axis or a sphere around one of its diameters; some of these experiments were brought by Professor Bjerknes before the Physical Society of London in the following June. Since that time, however, Professor Bjerknes, with the very important assistance of his son, Mr. Vilhelm Bjerknes, has been extending these experimental researches in the same direction, and with the results which it is the object of the present series of articles to describe.
The especial feature of interest in all Professor Bjerknes experiments has been the remarkably close analogy which exists between the phenomena exhibited in his mechanical experiments in water and other media and those of magnetism and of electricity, and it may be of some interest if we here recapitulate some of the more striking of these analogies.
(1.) In the first place, the vibrating or pulsating bodies, by setting the water or other medium in which they are immersed into vibration, set up in their immediate neighborhood a field of mechanical force very closely analogous to the field of magnetic force with which magnetized bodies are surrounded. The lines of vibration have precisely the same directions and form the same figures, while at the same time the decrease of the intensity of vibration by an increase of distance obeys precisely the same law as does that of magnetic intensity at increasing distances from a magnetic body.
(2.) When two or more vibrating bodies are immersed in a fluid, they set up around them fields of vibration, and act and react upon one another in a manner closely analogous to the action and reaction of magnets upon one another, producing the phenomena of attraction and repulsion. In this respect, however, the analogy appears to be inverse, repulsion being produced where, from the magnetic analogy, one would expect to find attraction, andvice versa.
(3.) If a neutral body, that is to say a body having no vibration of its own, be immersed in the fluid and within the field of vibration, phenomena are produced exactly analogous to the magnetic and diamagnetic phenomena produced by the action of a magnet upon soft iron or bismuth, its apparently magnetic or diamagnetic properties being determined by the specific gravity of the neutral body as compared to that of the medium in which it is immersed. If the neutral body be lighter than the medium, it exhibits the magnetic induction of iron with respect to polarity, but is nevertheless repelled; while if it be heavier than the medium, its direction is similar to that of diamagnetic bodies such as bismuth, but on the other hand exhibits the phenomena of attraction.
In this way Professor Bjerknes has been able to reproduce analogues of all the phenomena of magnetism and diamagnetism, those phenomena which may be classed as effects of induction being directly reproduced, while those which may be classed as effects of mechanical action, and resulting in change of place, are analogous inversely. This fact has been so much misunderstood both in this country and on the Continent that it will be well, before describing the experiments, to enter more fully into an explanation of these most interesting and instructive phenomena.
For the sake of clearness we will speak of magnetic induction as that property of a magnet by which it is surrounded by a field of force, and by which pieces of iron, within that field, are converted into magnets, and pieces of bismuth into diamagnets, and we will speak of magnetic action as the property of a magnet by which it attracts or repels another magnet, or by which it attacks or repels a piece of iron or bismuth magnetized by magnetic induction.
The corresponding hydrodynamic phenomena may be regarded in a similar manner; thus, when a vibrating or pulsating body immersed in a liquid surrounds itself with a field of vibrations, or communicates vibrations to other immersed bodies within that vibratory field, the phenomena so produced may be looked upon as phenomena of hydrodynamic induction, while on the other hand, when a vibrating or pulsating body attracts or repels another pulsating or vibratory body (whether such vibrations be produced by outside mechanical agency or by hydrodynamical induction), then the phenomena so produced are those of hydrodynamical action, and it is in this way that we shall treat the phenomena throughout this article, using the wordsinductionanddirect actionin these somewhat restricted meanings.
In the hydrodynamical experiments of Professor Bjerknes all the phenomena of magnetic induction can be reproduced directly and perfectly, but the phenomena of magnetic action are not so exactly reproduced, that is to say, they are subject to a sort of inversion. Thus when two bodies are pulsating together and in the same phase (i.e., both expanding and both contracting at the same time), they mutually attract each other: but if they are pulsating in opposite phases, repulsion is the result. From this one experiment taken by itself we might be led to infer that bodies pulsating in similar phases are the hydrodynamic analogues of magnets having their opposite poles presented to one another, and that bodies pulsating in opposite phases are analogous to a presentation of similar magnetic poles; but it will be seen at once that this cannot be the case if three magnetic poles or three pulsating bodies be considered instead of only two. It is clear,on the one hand, that three similar magnet poles will all repel one another, while, on the other, of three pulsating bodies, two of them must always attract one another, while a third would be repelled; and, moreover, two similarly pulsating bodies set up around them the same lines of force as two similar magnetic poles, and two oppositely pulsating bodies produce lines of force identically the same as those set up by two magnets of opposite polarity. Thus it will be seen that there is a break in the analogy between the hydrodynamical and the magnetic phenomena (if a uniform inversion of the effects can be called a break, for it is, as far as Professor Bjerknes' experiments go, without an exception); and if by any means this inversion could be reinverted, all the phenomena of magnetism and diamagnetism could be exactly reproduced by hydrodynamical analogues; there would thus be grounds for forming a theory of magnetism on the basis of mechanical phenomena, and a very important link in the chain of the correlation of the physical forces would be supplied.
While the experiments of Professor Bjerknes upon pulsating and rectilinearly vibrating bodies and their influence upon one another illustrate by very close analogies the phenomena of magnetism, those upon circularly vibrating bodies and their mutual influences bear a remarkable analogy to electrical phenomena; and it is a significant fact that exactly as in the case of magnetic illustration, the analogies are direct as regards the phenomena of induction, and inverse in their illustration of direct electrical action.
Fig.1.
Fig.2.
If we examine the figure produced by the field of force surrounding a conductor through which a current of electricity is being transmitted (see Fig. 1), we see that iron filings within that field arrange themselves in more or less concentric circles around the conductor conveying the current. From this fact Professor Bjerknes and his son, reasoning that, to produce a similar field of energy around a vibrating body, the vibrations of that body must partake of a circular or rotary character, constructed apparatus for producing the hydrodynamic analogue of electric currents, in which a conductor transmitting a current of electricity is represented by a cylinder to which oscillations in circles around its axis are given by suitable mechanical means, so as to cause the enveloping medium to follow its motion and make similar rotative vibrations. In some of the earlier experiments in this direction, cylinders carrying radial veins (A, Fig. 2) or fluted longitudinally around their surfaces (B, Fig. 2) were employed with the object of giving the vibrating cylinder a greater hold of the liquid in which they were immersed; but it was found that these vanes or flutings had but little or no effect upon water or liquids of similar viscosity, and Professor Bjerkes was led to adopt highly viscous fluids, such as Glycerin or maize sirup, both of which substances are well adapted for the experiments, being at the same time both highly viscous and perfectly transparent and colorless. In seeking, for the purpose of this research, a fluid medium which shall possess analogous properties to the luminiferous ether, or whatever may be the medium whose vibrations render manifest certain physical phenomena, it might be considered at first sight that substances so dense as glycerin and sirup could have but little in common with the ether, and that an analogy between experiments made within it and phenomena associated with ethereal vibrations would be of a very feeble description: but Professor Bjerknes has shown that the chief requisite in such a medium is that its viscosity should be great, not absolutely, but large only in proportion to its density, and if the density be small, the necessary viscosity may be small also. Neither is it necessary for the fluid medium to possess great internal friction, but what is necessary to the experiments is that the medium shall be one which is readily set into vibration by the action of the circularly vibrating cylinder; this property appears to be possessed exclusively by the more viscous fluids, and is, moreover, in complete accord with what is known of the luminiferous ether according to the theory of light.
The property is rather a kind of elasticity, which ordinary fluids do not possess, but which facilitates the propagation of transverse vibrations.
Fig.3.
One form of apparatus for the propagation of rotative oscillations is shown to the left of Fig. 3, and consists of a cylinder, A, mounted on a tubular spindle, and which is set into circular oscillations around its axis by the little vibrating membrane, C, which is attached to the axis of the cylinder by a little crank and connecting rod shown in detail in Fig. 4. This membrane is set into vibration by a rapidly pulsating column of air contained in a flexible tube M. by which apparatus is connected to the pulsation pump which was employed by Professor Bjerknes in his earlier experiments. In Fig. 5, a somewhat similar apparatus for producing horizontal vibrations is shown, and marked N H C, the only difference between them being one of mechanical detail necessitated by the change in the position of axis of vibration from the vertical to the horizontal.
Fig.4.
If circularly vibrating cylinders, such as we have described, be immersed in a viscous fluid and set into action, the following phenomena may be observed: 1. The effect upon the fluid itself, setting up therein a field of vibration, and corresponding by analogy with the production of a field of force around a wire conveying an electric current. 2. The effect upon other circularly vibrating bodies within that field of force corresponding to the action and reaction of electric currents upon one another. 3. The effect on pulsating and oscillating bodies similarly immersed, illustrating the mutual effects upon one another of magnets and electric currents. The first of these effects is one of induction, and, from what has been said from an earlier part of this article, it will be understood that the analogy between the hydrodynamic and the electric phenomena is direct and complete. The effects classified under the second and third heads, being phenomena of direct action (in the restricted use of the word), are uniformly analogous to the magnetic and electric phenomena which they illustrate.
Fig.5.
(To be continued.)
Like most musical instruments, the xylophone, had its origin in very remote times. The Hebrews and Greeks had instruments from which the one of to-day was derived, although the latter has naturally undergone many transformations. Along about 1742 we find it widely in use in Sicily under the name ofXylonganum. The Russians, Cossacks, and Tartars, and especially the mountain population of the Carpathians and Ural, played much upon an instrument of the same nature that they calledDierevaandSaloma.
Fig. 1.—METHOD OF PLAYING UPON THE XYLOPHONE.
It appears that the xylophone was played in Germany as early as the beginning of the 16th century. After this epoch it was in use for quite a long period, but gradually fell into oblivion until the beginning of the present century. It was toward 1830 that the celebrated Russian Gussikow undertook a grand artistic voyage through Europe, and gained a certain renown and received many honors due to his truly original productions. Gussikow possessed a remarkabletechniquethat permitted the musical instrument which he brought into fashion to be appreciated for all its worth.
Fig. 2.—PLAN VIEW OF THE XYLOPHONE.
As the name, "instrument of wood and straw," indicates, the xylophone (which Fig. 1 shows the mode of using) consists of small pieces of wood of varying length, and narrow or wide according to the tone that it is desired to get from them. These pieces of wood are connected with each other by cords so as to form a triangular figure (Fig. 2) that may be managed without fear of displacing the parts. The whole is laid upon bands of straw designed to bring out the sounds and render them stronger and purer. The sounds are produced by striking the pieces of wood with a couple of small hammers. They are short and jerky, and, as they cannot be prolonged, nothing but pieces possessing a quick rhythm can be executed upon the instrument. Dances, marches, variations, etc., are played upon it by preference, and with the best effect.
The popularity of this instrument is making rapid progress, and it is beginning to be played in orchestras in France [as it has been in America for many years]. A method of using it has just been published, as well as pieces of music adapted to it, with piano, violin, orchestra, etc., accompaniment.
This eminently useful application of the art of electrotyping originated with Volta, Cruickshank, and Wollaston about 1800 or 1801. In 1838, Spencer, of London, made casts of coins, and cast in intaglio from the matrices thus formed; in the same year Jacobi, of Dorpat, in Russia, made casts by electro deposit, which caused him to be put in charge of the work of gilding the dome of St. Isaac at St. Petersburg.
Electrotyping for the purposes of printing originated with Mr. Joseph A. Adams, a wood-engraver of New York, who made casts (1839-41) from wood-cuts, some engravings being printed from electrotype plates in the latter year. Many improvements in detail have been added since, in the processes as well as the appliances. Robert Murray introduced graphite as a coating for the form moulds. He first communicated his discovery to the Royal Institution of London, and afterward received a silver medal from the Society of Arts.
The process of electrotyping is as follows: The form is locked up very tightly, and is then coated with a surface of graphite, commonly known as blacklead, but it is a misnomer. This is put on with a brush, and may be done very evenly and speedily by a machine in which the brush is reciprocated over the type by hand-wheel, crank, and pitman. A soft brush and very finely powdered graphite are used; the superfluous powder being removed, and the face of the type cleaned by the palm of the hand.
A shallow pan, known as a moulding pan, is then filled with melted yellow wax, making a smooth, even surface, which is blackleaded. The pan is then secured to the head of the press, and the form placed on the bed, which is then raised, delivering an impression of the type upon the wax.
The pan is removed from the head of the press, placed on a table, and then built up, as it is termed. This consists in running wax upon the portions where large spaces occur between type, in order that corresponding portions in the electrotype may not be touched by the inking roller, or touched by the sagging down of the paper in printing.
The wax mould being built, is ready for blackleading, to give it a conducting surface upon which the metal may be deposited in the bath, superfluous blacklead being removed with a bellows. Blacklead, being nearly pure carbon, is a poor conductor, and a part of the metal of the pan is scraped clean, to form a place for the commencement of the deposit. The back of the moulding is waxed, to prevent deposit of copper thereon, and the face of the matrix is wetted to drive away all films or bubbles of air which may otherwise he attached to the blackleaded surface of the type.
The mould is then placed in the bath, containing a solution of sulphate of copper, and is made a part of an electric circuit, in which is also included the zinc element in the sulphuric-acid solution in the other bath. A film of copper is deposited on the blacklead surface of the mould; and when this shell is sufficiently thick, it is taken from the bath, the wax removed, the shell trimmed, the back tinned, straightened, backed with an alloy of type-metal, then shaved to a thickness, and mounted on a block to make it type-high.
has been introduced in which there is added finely pulverized tin to the graphite for facing the wax mould; the effect in the sulphate of copper bath is to cause a rapid deposition of copper by the substitution of copper for the tin, the latter being seized by the oxygen, while the copper is deposited upon the graphite. The film is after increased by the usual means. Knight's expeditious process consists in dusting fine iron filings on the wet graphite surface of the wax mould, and then pouring upon it a solution of sulphate of copper. Stirring with a brush expedites the contact, and a decomposition takes place; the acid leaves the copper and forms with the iron sulphate a solution which floats off, while the copper is freed and deposited in a pure metallic form upon the graphite. The black surface takes on a muddy tinge with marvelous rapidity. The electric-connection gripper is designed to hold and sustain the moulding pan and make an electric connection with the prepared conducting pan of the mould only, while the metallic pan itself is out of the current of electricity, and receives no deposit.
The thin copper-plate, when removed from the wax mould, is just as minutely correct in the lines and points as was the wax mould, and the original page of type. But it is obvious that the copper sheet is no use to get a print from. You must have something as solid as the type itself before it can be reproduced on paper. So a basis of metal is affixed to the copper film, and this again is backed up with wood thick enough to make the whole type-high. To get this, a man melts some tinfoil in a shallow iron tray, which he places on the surface of molten lead, kept to that heat in square tanks over ordinary fires. The tinfoil sticks to the back of the copper, and on the back of this is poured melted type-metal, until a solid plate has been formed, the surface of which is the copper facsimile and the body white metal. The electro metal plate, copper colored and bright on its surface, has now to go to the
Here are two departments. In one the plates are shaved and trimmed down to fit the wood blocks, which are made in the other department. Some of these operations are done by hand, but it is very interesting to see self-working machines planing the sheets of metal to precisely the required thinness with mathematical exactness. A pointed tool is set to a certain pitch, and the plate of metal is made to revolve in such a way that one continuous curl shaving falls until the whole surface (back) has been planed perfectly true. The wood blocks are treated in the same way, after being sawn into the required sizes by a number of circular saws. Another set of workmen fit and join the metal to the wood, trim the edges, and turn the blocks out type-high and ready for working on the printing press.
In Messrs. Harper's establishment in New York, an improved wet process of blackleading is adopted. The wax mould is laid face upward on the floor of an inclosed box, and a torrent of finely pulverized graphite suspended in water is poured upon it by means of a rotary pump, a hose, and a distributing nozzle which dashes the liquid equally over the whole surface of the mould. Superfluous graphite is then removed by copious washing, an extremely fine film of graphite adhering to the wax. This answers a triple purpose; it coats the mould with graphite, wets it ready for the bath, and expels air bubbles from the letters. This process prevents entirely the circulation of blacklead in the air, which has heretofore been so objectionable in the process of electrotyping.
The galvanoplastic process of M. Coblence for obtaining electrotypes of wood-engravings is as follows: A frame is laid upon a marble block, and then covered with a solution of wax, colophane, and turpentine. This mixture on the frame, after cooling, becomes hard, and presents a smooth, even surface. An engraved wooden block is then placed upon the surface of the frame, and subjected to a strong pressure. The imprint on matrix in cameo, having been coated with graphite, is then placed vertically in a galvanoplastic bath, and a cast, an exact reproduction of the wood-engraving, is obtained. The shell is then backed with type metal and finished in the usual way.—Printer and Stationer.
All the seismographs that have hitherto been employed have two grave disadvantages: they are either too simple, so that their indications are valueless, or too complicated, so that their high cost and delicacy, and the difficulty of mounting them and keeping them in order, tend to prevent them from being generally used.
Seismology will not be able to make any serious progress until it has at its disposal very certain and very numerous data as to telluric movements registered at a large number of points at once by accurate instruments. I have endeavored to construct a simple apparatus capable of automatically registering such facts as it is most necessary to know in scientific researches on the movements of the earth. After numerous experiments I believe that I have succeeded in solving this delicate problem, since my apparatus, put to the test of experience, has given me satisfactory results. I have consequently decided to submit it to the approval of men of science.
My seismograph is capable of registering (1) vertical shocks, (2) horizontal ones, (3) the order in which all the shocks manifest themselves, (4) their direction, and (5) the hour of the first movement.
CORDENONS' SEISMOGRAPH.
The apparatus is represented in the accompanying cut. The horizontal shocks are indicated by the front portion of the system, and the vertical ones by the back portion. The hour of the first shock is indicated as follows: The elastic strip of steel, C, is fixed by one of its extremities to a stationary support,d. When, as a consequence of a vertical motion, the free extremity of this strip oscillates, the leaden ball,x, drops into the tube,c, and, on reaching the bottom of this, acts by its shock upon a cord,i, which actuates the pendulum of a clock that has previously been stopped at 12. The other strip, B, is very similar to the one just described, but, instead of carrying a ball, it holds a small metallic cylinder,u, so balanced that a vertical shock in an upward direction causes it to drop forward into the anterior half of the tube to the left. A second vertical shock in a downward direction causes it to drop into the other half. The cylinder,u, and the ball,x, are regulated in their positions by means of screws affixed to a stationary support.
The portion of the apparatus designed to register horizontal (undulatory) motions consists of four vertical pendulums,z z z z, each of which is capable of moving in but one direction, since, in the other, it rests against a fixed column.
Telluric waves, according to modern observations, almost invariably in every region follow two directions that cross each other at right angles. When the seismograph has been arranged according to such directions, no matter from what part the first horizontal shock comes, one of the four pendulums will be set in motion. If, after the first undulation in one direction, another occurs in the opposite, the pendulum facing the first will in its turn begin to move; and if other undulations make themselves felt in diametrically opposite directions, the other pendulums will begin to act. These pendulums, in their motion, carry along the appendages,e e e e, which are so arranged as to fall in the center of the marble or iron table, one upon another, and thus show the order according to which the telluric waves manifested themselves. The part of the apparatus that records vertical shocks has a winch,r, which falls at the same place when the lead ball drops.
The apparatus as a whole may be inclosed in a case. When it is desired to employ it, it should be mounted in a cellar, while the clock that is connected with it can be located in one of the upper stories of the house.—F. Cordenons, in La Nature.
The three oils that form the subject of the examination detailed in this paper were consigned to a London broker, with a view to their being regularly exported from China if a market could be found for them here: it was, therefore, necessary to ascertain what commercial oils they resembled in character, so as to estimate to what uses they might be applied.
In color, transparency, and mobility, this oil considerably resembles olive oil. The odor and taste, though characteristic, are not easy to describe.
(1.)Specific Gravity.—The specific gravity at 60° F. is 917.5), water at 60° F. being taken as 1,000.
(2.)Action of Cold.—On subjecting to the cold produced by a mixture of pounded ice and salt, some solid fatty matter, probably stearine, separates, adhering to the side of the tube. It takes a longer exposure and a lower temperature than is necessary with olive oil. I did not succeed in solidifying it, but only in causing some deposit. Olive oil became solid, while almond and castor oil on the other hand did not deposit at all under similar circumstances. The lowest temperature observed was -13.3° C. (8° F.), the thermometer bulb being immersed in the oil.
A few qualitative tests, viz., the action of sulphuric acid, nitric acid (sp. gr. 1.42), and digestion, with more dilute nitric acid (1.2 sp. gr.) and a globule of mercury, were first tried.
When one drop of sulphuric acid is added to eight or ten drops of tea oil on a white plate, the change of color observed is more like that when almond oil is similarly treated than with any other oil, olive oil coming next in order of similarity.
When a few drops of tea oil are boiled with thirty drops or so of nitric acid in a small tube, the layer of oily matter, when the brisk action has moderated, is of a light yellow color, similar in tint to that produced from almond and olive oil under similar circumstances. When the oil is digested with an equal volume of nitric acid (1.2 sp. gr.), and a globule of mercury added, the whole becomes converted into a mass of elaidin in about two hours, of the same tint as that produced from almond oil when similarly treated.
These tests point to the fact that the oil may be considered as resembling almond or olive oil in composition, a conclusion which is borne out by the subsequent experiments.
(3.)Free Acidity of Oil.—The oil was found to contain free acid in small quantity, which was estimated by agitating a weighed quantity with alcohol, in which the free acid dissolves while the neutral fat does not, and titrating the alcoholic liquid with decinormal alkali, using solution of phenol-phthalein as an indicator.
It was thus found that 100 grammes of the oil require 0.34 gramme of caustic potash to neutralize the free acid. Mr. W. H. Deering (Journ. Soc. of Chem. Industry, Nov., 1884) states that in seven samples of olive oil examined by him, the minimum number for acidity was 0.86 per cent., and the maximum 1.64 per cent., the mean being 1.28 per cent. Tea oil compares favorably with olive oil, therefore, in respect of acidity, a quality of which note has to be taken when considering the employment of oil as a lubricating agent.
(4.)Saponification of the Oil.—Considerable light is thrown on the composition of a fixed oil by ascertaining how much alkali is required to saponify it. In order to estimate this, a known excess of alcoholic solution of potash is added to a weighed quantity of the oil, contained in a stout, well-closed bottle (an India-rubber stopper is the most convenient), which is then heated in a water oven until the liquid is clear, no oil bubbles being visible. Phenol-phthalein solution being added, the excess of potash is estimated by carefully titrating with standard hydrochloric acid solution.
It was thus found that 1,000 grammes of oil would require 195.5 grammes of caustic potash to convert it entirely into potash soap.
Koettstorfer, to whom this method of analysis is due, gives 191.8, and Messrs. F.W. and A.F. Stoddart the numbers 191 to 196, as the amounts of caustic potash required by 1,000 parts of olive oil. The numbers given by niger seed, cotton seed, and linseed oils are very similar to these. These oils differ from olive and tea oil, however, in having a higher specific gravity, and in the property they possess of drying to a greater or less extent on exposure to air.
(5.)The Fatty Acids Produced.—A solution of the potash soap was treated with excess of hydrochloric acid, and after being well washed with hot water, the cake of fatty acids was dried thoroughly and weighed. These, insoluble in water, amounted to 93.94 per cent, of the fat taken. The proportion dissolved in the water used for washing was estimated by titration with alkali; the quantity of KOH required was insignificant, equaling O.71 per cent, of the fat originally used. This portion was not further examined.
The insoluble fatty acids amounted, as last stated, to 93.94 per cent. Pure olein, supposing none of the liberated acid to be dissolved in water, would yield 95.7 per cent. of fatty acid.
The acid was evidently a mixture, and had no definite melting point. It was solid at 9° C., and sufficiently soft to flow at 12° C., but did not entirely liquefy under 22° C. To test its neutralizing power, 0.9575 gramme dissolved in alcohol was titrated with decinormal alkali; it required 34.05 c.c. This amount of pure oleic acid would require 33.95 c.c.; of pure stearic acid, which has almost the same molecular weight as oleic acid, 33.71 c.c.; or of pure palmitic acid, 37.4 c.c. This, taken in conjunction with the way in which the acid melted, makes it extremely probable that it is a mixture of oleic and stearic acids.
Additional evidence of the large proportion of oleic acid was furnished by forming the lead salt, and treating with ether, in which lead oleate is soluble, the stearate and palmitate being insoluble. In this way it was found that the oleic acid obtained from the ethereal solution of the lead salt amounted to 83.15 per cent. of the oil.
This acid was proved to be oleic, by its saturating power and its melting point, which were fairly concordant with those of the pure acid.
Appearance, etc.—The sample was of a deep brown color, of a fluidity intermediate between olive and castor oil, and possessed a strong, rather disagreeable odor.
The Specific Gravity at 60° Fahr., 914.0.—The specific gravity of rape oil and colza oil, both of which are obtained from species of the geniusBrassica, varies from 913.6 to 916.
Exposure to Cold.—This oil by exposure to a temperature of -12° C. (10° F.) becomes solidified in course of an hour, a bright orange-yellow mass resulting.
Qualitative Examination.—The three reagents before indicated were applied to this oil.
(a.) Sulphuric Acid.—The color produced was very marked and characteristic; it differed considerably from any of the others simultaneously tested, the nearest to it being olive end rape oil.
(b.) Strong Nitric Acid.—The reaction was more violent than before, the stratum of oil after cooling being darker in color than in the three cases before mentioned. The reaction with rape oil was similar in all respects.
(c.) Elaidin Test.—The solid mass of elaidin formed was of a darker color than that from olive, almond, and tea oil, but closely resembled that from rape oil.
Free Acidity.—This was estimated as above described. 100 grammes of oil would require 0.125 gramme caustic potash. The samples of rape oil examined by Deering (loc. cit.) were found to require from 0.21 to 0.78 KOH per 100 grammes oil.
Saponification of the Oil.—Upon saponifying with alcoholic potash, it was found that 1,000 grammes of oil required 175.2 grammes of potash for complete saponification.
The number obtained by Koettstorfer for colza was 178.7, by Messrs. Stoddart for rape oil, 175-179, and by Deering for rape oil, 170.8-175.5. The only other oil of which I can find figures resembling these is castor oil, which requires 176-178 grammes per kilo (Messrs. Stoddart). The difference in specific gravity between this (cabbage) oil and castor oil and the solubility of the latter in alcohol point to a wide distinction between them. Hence I think the numbers above given conclusively demonstrate the resemblance between this oil and rape oil in composition.
The Fatty Acids.—The acids produced by adding HCl to the potash soap were almost entirely insoluble in water. The actual amount of potash required to neutralize the acid in the wash water equaled 0.20 per cent. of the oil originally taken.
The insoluble fatty acid amounted to 95.315 per cent. of the oil taken. It was evidently a mixture of two or more fatty acids. On trying to take its melting point, I found that it commenced to soften at 17° C., was distinctly liquid at 19°, but not completely melted until 22° C.
According to O. Bach (Year Book Pharm., 1884, p. 250), the fatty acids from rape seed oil melt at 20.7° C., which is fairly concordant with the result obtained for cabbage oil acids.
The neutralizing power of these acids was then tested. 0.698 gramme dissolved in alcohol required 20.52 c.c. decinormal alkali. It is a singular coincidence that brassic acid (C22H42O2), which is a characteristic acid of colza and rape oils, would have required almost exactly this quantity of alkali for neutralization, O.698 brassic acid theoretically saturating 20.69 c.c. of decinormal alkali. I am disposed to regard this as a coincidence, since a subsequent experiment showed that the leadsalts formed were partially soluble in ether, whereas the lead salt of brassic acid is said to be insoluble in this liquid.
Appearance, etc.—This oil has a decided brown color and a persistent and disagreeable odor. It is rather more fluid than castor oil. Glass vessels containing it soon show a film of apparently resinous material, which forms whenever a portion of the oil flows from the lip or edge down the outside of the vessel, and is thus exposed to the air in a thin stream. This drying power is one of its most prominent characters. If a few drops be exposed in a flat dish, in the water oven, the oil dries rapidly, so that in two hours the gain in weight will be appreciable, and in four hours the whole will have become solid.
The Specific Gravity at 60° Fahr., 940.15.—This is an unusually high gravity for a fixed oil. The only two which exceed it are castor oil, which is 960, about, and croton oil, which is very similar to this, 942 to 943 (A. H. Allen). It is interesting to note that both these oils are yielded by plants of the natural orderEuphorbiaceæ, to which the plant yielding so-called wood oil belongs.
Exposure to Cold.—This oil is apparently unaffected by exposure to a temperature of -13.3° C. (8° F).
Qualitative Examination.—The action of sulphuric acid is remarkable. When a drop comes in contact with the oil, the latter apparently solidifies round the drop of acid, forming a black envelope which grows in size and gradually absorbs and acts upon so much of the surrounding oil as to assume the appearance of a large dried currant of somewhat irregular shape.
When a drop of the oil is added to nitric acid, it solidifies, and on heating very readily changes into an orange yellow solid, which appears to soften, though not to liquefy, at the temperature of boiling water. This substance is readily soluble in hot solution of potash or soda, producing a deep brown liquid, from which it is again deposited in flocks on acidifying. I have not yet found any solvent for it. The action of nitric acid with linseed oil is more similar to this than that with any other oil I have tried, but the nitro products of the two, if I may so call them, are quite different from one another. That from linseed oil produced as indicated remains liquid at ordinary temperatures, as does the oil upon its addition to the acid.
Elaidin Test.—By the action of nitric acid in presence of mercury, a semi-solid mass is produced of a much deeper color than in the preceding cases. A portion of the oil remains in the liquid state, as is usually the case with drying oils.
Free Acidity.—By the method indicated, it was found that 100 grammes of oil required 0.39 grammes caustic potash to neutralize the acid occurring in a free state.
Saponification of the Oil.—The oil saponifies readily on being heated with potash in presence of alcohol, and the amount required to convert it entirely into potash soap was 211 grammes of caustic potash per thousand grammes of oil. There are no saponification numbers for oils that can be considered close to this. I can find no record of any having been obtained between 197 and 221, so that the further examination on which I am now engaged may show this unusual number to be due to this oil containing some new fatty acid in combination.
The Fatty Acid.—The acids produced by adding acid to the potash soap formed in this case a cake on cooling, of a much deeper color than I have before obtained. After washing well they amounted to 94.10 per cent. of the oil. The amount dissolved by the water in washing was in this case also very small, the potash required for neutralizing equaling 1.02 per cent. of the weight of oil.
I found that the cakes of acids were solid at 36° C., and were completely melted at 39°.
On solution in alcohol, and digestion for two days with animal charcoal, the color was much diminished, and on the liquid being filtered and cooled to 0° C., an abundance of small white crystalline plates separated out, which, when dried, melted at 67° C.
The crude fatty acids turn black with sulphuric acid, as the oil does, and yield a similar substance with nitric acid. It is similar in appearance, but differs in that it melts at about 50° C., and is soluble in glacial acetic acid, which is not the case with the substance from the oil.
These fatty acids crystallize on cooling, in a most characteristic and beautiful way, forming wavy circular plates totally unlike any that I have seen before.
The above experiments may, I think, be taken as conclusive as to the nature of tea oil and cabbage oil. The former may certainly be considered a useful lubricating agent for the finer kinds of machinery. The work upon wood oil is not yet sufficiently complete to show us the nature of its proximate constituents. I am continuing the examination of this oil. Perhaps I need scarcely add that there is no connection between this "wood oil" and the Gurgun balsam, the product ofDipterocarpus turbinatus, which is also known as "wood oil."