This house, which belongs to Mr J. N. D'Andrea, is built on the Basque principle, under one roof, with covered balconies on the south side, the northside being kept low to give the sun an opportunity of shining in winter on the house and greenhouse adjacent, as well as to assist in the more picturesque grouping of the two. On this side is placed, approached by porch and lobby, the hall with a fireplace of the "olden time," lavatory, etc., butler's pantry, w. c., staircase, larder, kitchen, scullery, stores, etc.
On the south side are two sitting rooms, opening into a conservatory. There are six bedrooms, a dining-room, bath room, and housemaid's sink.
The walls are built of colored wall stones known as "insides," and half-timbered brickwork covered with the Portland cement stucco, finished Panan, and painted a cream-color.
All the interior woodwork is of selected pitch pine, the hall being boarded throughout. Colored lead light glass is introduced in the upper parts of the windows in every room, etc.
The architect is Mr. W. A. Herbert Martin, of Bradford.--Architect
HOUSE AT HEATON, BRADFORD.
HOUSE AT HEATON, BRADFORD.
The principal floor of this design is elevated three feet above the surface of the ground, and is approached by the front steps leading to the platform. The height of the first floor is eleven feet, the second ten feet, and the cellar six feet six inches in the clear. The porch is so constructed that it can be put on either the front or side of the house, as it may suit the owner. The rooms, eight in number, are airy and of convenient size. The kitchen has a range, sink, and boiler, and a large closet, to be used as a pantry. The windows leading out to the porch will run to the floor, with heads running into the walls. In the attic the chambers are 10x10 feet, 13x14 feet, 12x13 feet, 10x10½ feet, and a hall 6 feet wide, with large closets and cupboards for each chamber. The building is so constructed that an addition can be made to the rear any time by using the present kitchen as a dining room and building a new kitchen.
A MANSARD ROOF DWELLING. First Floor.
A MANSARD ROOF DWELLING. First Floor.
A MANSARD ROOF DWELLING. Second Floor.
A MANSARD ROOF DWELLING. Second Floor.
These plans will prove suggestive to those contemplating the building of a new house, even if radical changes are made in the accompanying designs.--American Cultivator.
A MANSARD ROOF DWELLING. Front Elevation.
A MANSARD ROOF DWELLING. Front Elevation.
[Footnote: Aug. Guerout inLa Lurmière Electrique.]
An endeavor has often been made to carry the origin of the electric telegraph back to a very remote epoch by a reliance on those more or less fanciful descriptions of modes of communication based upon the properties of the magnet.
It will prove not without interest before entering into the real history of the telegraph to pass in review the various documents that relate to the subject.
In continuation of the 21st chapter of hisMagia naturalis, published in 1553, J. B. Porta cites an experiment that had been made with the magnet as a means of telegraphing. In 1616, Famiano Strada, in hisProlusiones Academicæ, takes up this idea, and speaks of the possibility of two persons communicating by the aid of two magnetized needles influenced by each other at a distance. Galileo, inDialogo intorno, written between 1621 and 1632 and Nicolas Caboeus, of Ferrara, in hisPhilosophia magnetica, both reproduce analogous descriptions, not however without raising doubts as to the possibility of such a system.
A document of the same kind, to which great importance has been attached is found in theRecreations mathematiquespublished at Rouen in 1628, under the pseudonym of Van Elten, and reprinted several times since, with the annotations and additions of Mydorge and Hamion and which must, it appears, be attributed to the Jesuit Leurechon. In his chapter on the magnet and the needles that are rubbed therewith, we find the following passage.
"Some have pretended that, by means of a magnet or other like stone, absent persons might speak with one another. For example, Claude being at Paris, and John at Rome, if each had a needle that had been rubbed with some stone, and whose virtue was such that in measure as one needle moved at Paris the other would move just the same at Rome, and if Claude and John each had an alphabet, and had agreed that they would converse with each other every afternoon at 6 o'clock, and the needle having made three and a half revolutions as a signal that Claude, and no other, wished to speak to John, then Claude wishing to say to him that the king is at Paris would cause his needle to move, and stop at T, then at H, then at E, then at K, I, N, G and so on. Now, at the same time, John's needle, according with Claude's, would begin to move and then stop at the same letters, and consequently it would be easily able to write or understand what the other desired to signify to it. The invention is beautiful, but I do not think there can be found in the world a magnet that has such a virtue. Neither is the thing expedient, for treason would be too frequent and too covert."
The same idea was also indicated by Joseph Glanville in hisScepsis scientifica, which appeared in 1665, by Father Le Brun, in hisHistoire critique des pratiques superstitieuses, and finally by the Abbé Barthelemy in 1788.
The suggestion offered by Father Kircher, in hisMagnes sive de arte magnetica, is a little different from the preceding. The celebrated Jesuit father seeks however, to do nothing more than to effect a communication of thoughts between two rooms in the same building. He places, at short distances from each other, two spherical vessels carrying on their circumference the letters of the alphabet, and each having suspended within it, from a vertical wire a magnetized figure. If one of these latter he moved, all the others must follow its motions, one after the other, and transmission will thus be effected from the first vessel to the last. Father Kircher observes that it is necessary that all the magnets shall be of the same strength, and that there shall be a large number of them, which is something not within the reach of everybody. This is why he points out another mode of transmitting thought, and one which consists in supporting the figures upon vertical revolving cylinders set in motion by one and the same cord hidden with in the walls.
There is no need of very thoroughly examining all such systems of magnetic telegraphy to understand that it was never possible for them to have a practical reality, and that they were pure speculations which it is erroneous to consider as the first ideas of the electric telegraph.
We shall make a like reserve with regard to certain apparatus that have really existed, but that have been wrongly viewed as electric telegraphs. Such are those of Comus and of Alexandre. The first of these is indicated in a letter from Diderot to Mlle. Voland, dated July 12, 1762. It consisted of two dials whose hands followed each other at a distance, without the apparent aid of any external agent. The fact that Comus published some interesting researches on electricity in theJournal de Physiquehas been taken as a basis for the assertion that his apparatus was a sort of electrical discharge telegraph in which the communication between the two dials was made by insulated wires hidden in the walls. But, if it be reflected how difficult it would have been at that epoch to realize an apparatus of this kind, if it be remembered that Comus, despite his researches on electricity, was in reality only a professor of physics to amuse, and if the fact be recalled that cabinets of physics in those days were filled with ingenious apparatus in which the surprising effects were produced by skillfully concealed magnets, we shall rather be led to class among such apparatus the so-called "Comus electric telegraph."
We find, moreover, in Guyot'sRecreations physiques et mathematiques--a work whose first edition dates back to the time at which Comus was exhibiting his apparatus--a description of certain communicating dials that seem to be no other than those of the celebrated physicist, and which at all events enables us to understand how they worked.
Let one imagine to himself two contiguous chambers behind which ran one and the same corridor. In each chamber, against the partition that separated it from the corridor, there was a small bracket, and upon the latter, and very near the wall, there was a wooden dial supported on a standard, but in no wise permanently fixed upon the bracket. Each dial carried a needle, and each circumference was inscribed with twenty-five letters of the alphabet. The experiment that was performed with these dials consisted in placing the needle upon a letter in one of the chambers, when the needle of the other dial stopped at the same letter, thus making it possible to transmit words and even sentences. As for the means of communication between the two apparatus, that was very simple: One of the two dials always served as a transmitter, and the other as a receiver. The needle of the transmitter carried along in its motion a pretty powerful magnet, which was concealed in the dial, and which reacted through the partition upon a very light magnetized needle that followed its motions, and indicated upon an auxiliary dial, to a person hidden in the corridor, the letter on which the first needle had been placed. This person at once stepped over to the partition corresponding to the receiver, where another auxiliary dial permitted him to properly direct at a distance the very movable needle of the receiver. Everything depended, as will be seen, upon the use of the magnet, and upon a deceit that perfectly accorded with Comus' profession. There is, then, little thought in our opinion that if the latter's apparatus was not exactly the one Guyot describes, it was based upon some analogous artifice.
Jean Alexandre's telegraph appears to have borne much analogy with Comus'. Its inventor operated it in 1802 before the prefect of Indre-et-Loire. As a consequence of a report addressed by the prefect of Vienne to Chaptal, and in which, moreover, the apparatus in question was compared to Comus', Alexandre was ordered to Paris. There he refused to explain upon what principle his invention was based, and declared that he would confide his secret only to the First Consul. But Bonaparte, little disposed to occupy himself with such an affair, charged Delambre to examine it and address a report to him. The illustrious astronomer, despite the persistence with which Alexandre refused to give up his secret to him, drew a report, the few following extracts from which will, we think, suffice to edify the reader:
"The pieces that the First Consul charged me to examine did not contain enough of detail to justify an opinion. Citizen Beauvais (friend and associate of Alexandre) knows the inventor's secret, but has promised him to communicate it to no one except the First Consul. This circumstance might enable me to dispense with any report; for how judge of a machine that one has not seen and does not know the agent of? All that is known is that thetelegraphe intimeconsists of two like boxes, each carrying a dial on whose circumference are marked the letters of the alphabet. By means of a winch, the needle of one dial is carried to all the letters that one has need to use, and at the same instant the needle of the second box repeats, in the same order, all the motions and indications of the first.
"When these two boxes are placed in two separate apartments, two persons can write to and answer one another, without seeing or being seen by one another, and without any one suspecting their correspondence. Neither night nor fog can prevent the transmission of a dispatch.... The inventor has made two experiments--one at Portiers and the other at Tours--in the presence of the prefects and mayors, and the record shows that they were fully successful. To-day, the inventor and his associate ask that the First Consul be pleased to permit one of the boxes to be placed in his apartment and the other at the house of Consul Cambaceres in order to give the experiment all theéclatand authenticity possible; or that the First Consul accord a ten minutes' interview to citizen Beauvais, who will communicate to him the secret, which is so easy that the simpleexposeof it would be equivalent to a demonstration, and would take the place of an experiment.... If, as one might be tempted to believe from a comparison with a bell arrangement, the means adopted by the inventor consisted in wheels, movements, and transmitting pieces, the invention would be none the less astonishing.... If, on the contrary, as the Portier's account seems to prove, the means of communication is a fluid, there would be the more merit in his having mastered it to such a point as to produce so regular and so infallible effects at such distances.... But citizen Beauvais ... desires principally to have the First Consul as a witness and appreciator.... It is to be desired, then, that the First Consul shall consent to hear him, and that he may find in the communication that will be made to him reasons for giving the invention a good reception and for properly rewarding the inventor."
But Bonaparte remained deaf, and Alexandre persisted in his silence, and died at Angers, in 1832, in great poverty, without having revealed his secret.
As, in 1802, Volta's pile was already invented, several authors have supposed an application of it in Alexandre's apparatus. "Is it not allowable to believe," exclaims one of these, "that the electric telegraph was at that time discovered?" We do not hesitate to respond in the negative. The pile had been invented for too short a time, and too little was then known of the properties of the current, to allow a man so destitute of scientific knowledge to so quickly invent all the electrical parts necessary for the synchronic operation of the two needles. In thistelegraphe intimewe can only see an apparatus analogous to the one described by Guyot, or rather a synchronism obtained by means of cords, as in Kircher's arrangement. The fact that Alexandre's two dials were placed on two different stories, and distant, horizontally, fifteen meters, in nowise excludes this latter mode of transmission. On another hand, the mystery in which Alexandre was shrouded, his declaration relative to the use of a fluid, and the assurance with which he promised to reveal his secret to the First Consul, prove absolutely nothing, for too often have the most profoundly ignorant people--the electric girl, for example--befooled learned bodies by the aid of the grossest frauds. From the standpoint of the history of the electric telegraph, there is no value, then, to be attributed to this apparatus of Alexandre, any more than there is to that of Comus or toanyof the dreams based upon the properties of the magnet.
The history of the electric telegraph really begins with 1753, the date at which is found the first indication of a telegraph truly based upon the use of electricity. This telegraph is described in a letter written by Renfrew, dated Feb. 1, 1753, and signed with the initials "C.M.," which, in all probability, were those of a savant of the time--Charles Marshall. A few extracts from this letter will give an idea of the precision with which the author described his invention:
"Let us suppose a bundle of wires, in number equal to that of the letters of the alphabet, stretched horizontally between two given places, parallel with each other and distant from each other one inch.
"Let us admit that after every twenty yards the wires are connected to a solid body by a juncture of glass or jeweler's cement, so as to prevent their coming in contact with the earth or any conducting body, and so as to help them to carry their own weight. The electric battery will be placed at right angles to one of the extremities of the wires, and the bundle of wires at each extremity will be carried by a solid piece of glass. The portions of the wires that run from the glass support to the machine have sufficient elasticity and stiffness to return to their primitive position after having been brought into contact with the battery. Very near to this same glass support, on the opposite side, there descends a ball suspended from each wire, and at a sixth or a tenth of an inch beneath each ball there is placed one of the letters of the alphabet written upon small pieces of paper or other substance light enough to be attracted and raised by the electrified ball. Besides this, all necessary arrangements are taken so that each of these little papers shall resume its place when the ball ceases to attract.
FIG. 1.--LESAGE'S TELEGRAPH.
FIG. 1.--LESAGE'S TELEGRAPH.
"All being arranged as above, and the minute at which the correspondence is to begin having been fixed upon beforehand, I begin the conversation with my friend at a distance in this way: I set the electric machine in motion, and, if the word that I wish to transcribe is 'Sir,' for example, I take, with a glass rod, or with any other body electric through itself or insulating, the different ends of the wires corresponding to the three letters that compose the word. Then I press them in such a way as to put them in contact with the battery. At the same instant, my correspondent sees these different letters carried in the same order toward the electrified balls at the other extremity of the wires. I continue to thus spell the words as long as I judge proper, and my correspondent, that he may not forget them, writes down the letters in measure as they rise. He then unites them and reads the dispatch as often as he pleases. At a given signal, or when I desire it, I stop the machine, and, taking a pen, write down what my friend sends me from the other end of the line."
The author of this letter points out, besides, the possibility of keeping, in the first place, all the springs in contact with the battery, and, consequently, all the letters attracted, and of indicating each letter by removing its wire from the battery, and consequently making it fall. He even proposed to substitute bells of different sounds for the balls, and to produce electric sparks upon them. The sound produced by the spark would vary according to the bell, and the letters might thus be heard.
Nothing, however, in this document authorizes the belief that Charles Marshall ever realized his idea, so we must proceed to 1774 to find Lesage, of Geneva, constructing a telegraph that was based upon the principle indicated twenty years before in the letter of Renfrew.
The apparatus that Lesage devised (Fig. 1) was composed of 24 wires insulated from one another by a non conducting material. Each of these wires corresponded to a small pith ball suspended by a thread. On putting an electric machine in communication with such or such a one of these wires, the ball of the corresponding electrometer was repelled, and the motion signaled the letter that it was desired to transmit. Not content with having realized an electric telegraph upon a small scale, Lesage thought of applying it to longer distances.
"Let us conceive," said he in a letter written June 22, 1782, to Mr. Prevost, of Geneva, "a subterranean pipe of enameled clay, whose cavity at about every six feet is separated by partitions of the same material, or of glass, containing twenty-four apertures in order to give passage to as many brass wires as these diaphragms are to sustain and keep separated. At each extremity of this pipe are twenty-four wires that deviate from one another horizontally, and that are arranged like the keys of a clavichord; and, above this row of wire ends, are distinctly traced the twenty-four letters of the alphabet, while beneath there is a table covered with twenty-four small pieces of gold-leaf or other easily attractable and quite visible bodies."
Lesage had thought of offering his secret to Frederick the Great; but he did not do so, however, and his telegraph remained in the state of a curious cabinet experiment. He had, nevertheless, opened the way, and, dating from that epoch, we meet with a certain number of attempts at electrostatic telegraphy. [1]
[Footnote 1: Advantage has been taken of a letter from Alexander Volta to Prof. Barletti (dated 1777), indicating the possibility of firing his electric pistol from a great distance, to attribute to him a part in the invention of the telegraph. We have not shared in this opinion, which appears to us erroneous, since Volta, while indicating the possibility above stated, does not speak of applying such a fact to telegraphy.]
The first in date is that of Lemond, which is spoken of by Arthur Young (October 16, 1787), in hisVoyage Agronomique en France:
"In the evening," says he, "we are going to Mr. Lemond's, a very ingenious mechanician, and one who has a genius for invention.... He has made a remarkable discovery in electricity. You write two or three words upon paper; he takes them with him into a room and revolves a machine within a sheath at the top of which there is an electrometer--a pretty little ball of feather pith. A brass wire is joined to a similar cylinder, and electrified in a distant apartment, and his wife on remarking the motions of the ball that corresponds, writes down the words that they indicate; from whence it appears that he has formed an alphabet of motions. As the length of the wire makes no difference in the effect, a correspondence might be kept up from very far off, for example with a besieged city, or for objects much more worthy of attention. Whatever be the use that shall be made of it, the discovery is an admirable one."
And, in fact, Lemond's telegraph was of the most interesting character, for it was a single wire one, and we already find here an alphabet based upon the combination of a few elementary signals.
The apparatus that next succeeds is the electric telegraph that Reveroni Saint Cyr proposed in 1790, to announce lottery numbers, but as to the construction of which we have no details. In 1794 Reusser, a German, made a proposition a little different from the preceding systems, and which is contained in theMagazin für das Neueste aus der Physik und Naturgeschichte, published by Henri Voigt.
"I am at home," says Reusser, "before my electric machine, and I am dictating to some one on the other side of the street a complete letter that he is writing himself. On an ordinary table there is fixed vertically a square board in which is inserted a pane of glass. To this glass are glued strips of tinfoil cut out in such a way that the spark shall be visible. Each strip is designated by a letter of the alphabet, and from each of them starts a long wire. These wires are inclosed in glass tubes which pass underground and run to the place whither the dispatch is to be transmitted. The extremities of the wires reach a similar plate of glass, which is likewise affixed to a table and carries strips of tinfoil similar to the others. These strips are also designated, by the same letters, and are connected by a return wire with the table of him who wishes to dictate the message. If, now, he who is dictating puts the external armature of a Leyden jar in contact with the return wire, and the ball of this jar in contact with a metallic rod touching that of the tinfoil strip which corresponds with the letter which he wishes to dictate to the other, sparks will be produced upon the nearest as well as upon the remotest strips, and the distant correspondent, seeing such sparks, may immediately write down the letter marked. Will an extended application of this system ever be made? That is not the question; it is possible. It will be very expensive; but the post hordes from Saint Petersburg to Lisbon are also very expensive, and if any one should apply the idea on a large scale, I shall claim a recompense."
Every letter, then, was signaled by one or several sparks that started forth on the breaking of the strip; but we see nothing in this document to authorize the opinion which has existed, that every tinfoil strip was a sort of magic tablet upon which the sparks traced the very form of the letter to be transmitted.
Voigt, the editor of theMagazin, adds, in continuation of Reusser's communication: "Mr. Reusser should have proposed the addition to this arrangement of a vessel filled with detonating gas which could be exploded in the first place, by means of the electric spark, in order to notify the one to whom something was to be dictated that he should direct his attention to the strips of tinfoil."
This passage gives the first indication of the use of a special call for the telegraph. The same year (1794), in a work entitledVersuch über Telegraphie und Telegraphen, Boeckmann likewise proposed the use of the pistol as a call signal, in conjunction with the use of a line composed of two wires only, and of discharges in the air or a vacuum, grouped in such a way as to form an alphabet.
Experiments like those indicated by Boeckmann, however, seem to have been made previous to 1794, or at that epoch, at least, by Cavallo, since the latter describes them in aTreatise on Electricitywritten in English, and a French translation of which was published in 1795. In these experiments the length of the wires reached 250 English feet. Cavallo likewise proposed to use as signals combustible or detonating materials, and to employ as a call the noise made by the discharge of a Leyden jar.
In 1796 occurred the experiments of Dr. Francisco Salva and of the Infante D. Antonio. The following is what we may read on this subject in theJournal des Sciences:
"Prince de la Paix, having learned that Dr. Francisco Salva had read before the Royal Academy of Sciences of Barcelona a memoir on the application of electricity to telegraphy, and that he had presented at the same time an electric telegraph of his own invention, desired to examine this machine in person. Satisfied as to the accuracy and celerity with which we can converse with another by means of it, he obtained for the inventor the honor of appearing before the king. Prince de la Paix, in the presence of their majesties and of several lords, caused the telegraph to converse to the satisfaction of the whole court. The telegraph conversed some days afterward at the residence of the Infante D. Antonio.
"His Highness expressed a desire to have a much completer one that should have sufficient electrical power to communicate at great distances on land and sea. The Infante therefore ordered the construction of an electric machine whose plate should be more than forty inches in diameter. With the aid of this machine His Highness intends to undertake a series of useful and curious experiments that he has proposed to Dr. D. Salva."
In 1797 or '98 (some authors say 1787), the Frenchman, Betancourt, put up a line between Aranjuez and Madrid, and telegraphed through the medium of discharges from a Leyden jar.
But the most interesting of the telegraphs based upon the use of static electricity is without doubt that of Francis Ronalds, described by the latter, in 1823, in a pamphlet entitledDescriptions of an Electrical Telegraph and of some other Electrical Apparatus, but the construction of which dates back to 1816.
What is peculiarly interesting in Ronalds' apparatus is that it presents for the first time the use of two synchronous movements at the two stations in correspondence.
The apparatus is represented in Fig. 2. It is based upon the simultaneous working of two pith-ball electrometers, combined with the synchronous running of two clock-work movements. At the two stations there were identical clocks for whose second hand there had been substituted a cardboard disk (Fig. 3), divided into twenty sectors. Each of these latter contained one figure, one letter, and a conventional word. Before each movable disk there was a screen, A (Fig. 2), containing an aperture through which only one sector could, be seen at a time. Finally, before each screen there was a pith-ball electrometer. The two electrometers were connected together by means of a conductor (C) passing under the earth, and which at either of its extremities could be put in communication with either an electric machine or the ground. A lever handle, J, interposed into the circuit a Volta's pistol, F, that served as a call.
When one of the operators desired to send a dispatch to the other he connected the conductor with the machine, and, setting the latter in operation, discharged his correspondent's pistol as a signal. The call effected, the first operator continued to revolve the machine so that the balls of pith should diverge in the two electrometers. At the same time the two clocks were set running. When the sender saw the word "attention" pass before the slit in the screen he quickly discharged the line, the balls of the two electrometers approached each other, and, if the two clocks agreed perfectly, the correspondent necessarily saw in the aperture in his screen the same word, "attention." If not, he moved the screen in consequence, and the operation was performed over until he could send, in his turn, the word "ready." Afterward, the sender transmitted in the same way one of the three words, "letters," "figures," "dictionary," in order to indicate whether he wished to transmit letters or figures, or whether the letters received, instead of being taken in their true sense, were to be referred to a conventional vocabulary got up in advance. It was after such preliminaries that the actual transmission of the dispatch was begun. The pith balls, which were kept constantly apart, approached each other at the moment the letter to be transmitted passed before the aperture in the screen.
Ronalds, in his researches, busied himself most with the construction of lines. He put up on the grounds near his dwelling an air line 8 miles long; and, to do so, stretched fine iron wire in zigzag fashion between two frames 18 meters apart. Each of these frames carried thirty-seven hooks, to which the wire was attached through the intermedium of silk cords. He laid, besides, a subterranean line of 525 feet at a depth of 4 feet. The wire was inclosed within thick glass tubes which were placed in a trough of dry wood, of 2 inch section, coated internally and externally with pitch. This trough was, moreover, filled full of pitch and closed with a cover of wood. Ronalds preferred these subterranean conductors to air lines. A portion of one of them that was laid by him at Hammersmith figured at the Exhibition of 1881, and is shown in Fig. 4.
Nearly at the epoch at which Ronalds was experimenting in England, a certain Harrisson Gray Dyar was also occupying himself with electrostatic telegraphy in America. According to letters published only in 1872 by American journals, Dyar constructed the first telegraph in America. This line, which was put up on Long Island, was of iron wire strung on poles carrying glass insulators, and, upon it, Dyar operated with static electricity. Causing the spark to act upon a movable disk covered with litmus paper, he produced by the discoloration of the latter dots and dashes that formed an alphabet.
FIG. 2.
FIG. 2.
These experiments, it seems, were so successful that Dyar and his relatives resolved to construct a line from New York to Philadelphia; but quarrels with his copartners, lawsuits, and other causes obliged him to leave for Rhode Island, and finally for France in 1831. He did not return to America till 1858.
Dyar, then, would seem to have been the first who combined an alphabet composed of dots and dashes. On this point, priority has been claimed by Swaim in a book that appeared at Philadelphia in 1829 under the title ofThe Mural Diagraph, and in a communication inserted in theComptes Rendusof the Academic des Sciences for Nov. 27, 1865.
FIG. 3.
FIG. 3.
In 1828, likewise, Victor Triboaillet de Saint Amand proposed to construct a telegraph line between Paris and Brussels. This line was to be a subterranean one, the wire being covered with gum shellac, then with silk, and finally with resin, and being last of all placed in glass tubes. A strong battery was to act at a distance upon an electroscope, and the dispatches were to be transmitted by the aid of a conventional vocabulary based upon the number of the electroscope's motions.
Finally, in 1844, Henry Highton took out a patent in England for a telegraph working through electricity of high tension, with the use of a single line wire. A paper unrolled regularly between two points, and each discharge made a small hole in it, But this hole was near one or the other of the points according as the line was positively or negatively charged. The combination of the holes thus traced upon two parallel lines permitted of the formation of an alphabet. This telegraph was tried successfully over a line ten miles long, on the London and Northwestern Railway.
FIG. 4.
FIG. 4.
We have followed electrostatic telegraphs up to an epoch at which telegraphy had already entered upon a more practical road, and it now remains for us to retrace our steps toward those apparatus that are based upon the use of the voltaic current.
Prof. Dolbear observes that if a galvanometer is placed between the terminals of a circuit of homogeneous iron wire and heat is applied, no electric effect will be observed; but if the structure of the wire is altered by alternate bending or twisting into a helix, then the galvanometer will indicate a current. The professor employs a helix connected with a battery, and surrounding a portion of the wire in circuit with the galvanometer. The current in the helix magnetizes the circuit wire inclosed, and the galvanometer exhibits the presence of electricity. The experiment helps to prove that magnetism is connected with some molecular change of the magnetized metal.
[Footnote: From a recent lecture in London before the Institute of Civil Engineers.]
Dr. Siemens, in opening the discourse, adverted to the object the Council had in view in organizing these occasional lectures, which were not to be lectures upon general topics, but the outcome of such special study and practical experience as members of the Institution had exceptional opportunities of acquiring in the course of their professional occupation. The subject to be dealt with during the present session was that of electricity. Already telegraphy had been brought forward by Mr. W. H. Preece, and telephonic communication by Sir Frederick Bramwell.
Thus far electricity had been introduced as the swift and subtile agency by which signals were produced either by mechanical means or by the human voice, and flashed almost instantaneously to distances which were limited, with regard to the former, by restrictions imposed by the globe. To the speaker had been assigned the task of introducing to their notice electric energy in a different aspect. Although still giving evidence of swiftness and precision, the effects he should dwell upon were no longer such as could be perceived only through the most delicate instruments human ingenuity could contrive, but were capable of rivaling the steam engine, compressed air, and the hydraulic accumulator in the accomplishment of actual work.
In the early attempts at magneto electric machines, it was shown that, so long as their effect depended upon the oxidation of zinc in a battery, no commercially useful results could have been anticipated. The thermo-battery, the discovery of Seebeck in 1822, was alluded to as a means of converting heat into electric energy in the most direct manner; but this conversion could not be an entire one, because the second law of thermo-dynamics, which prevented the realization as mechanical force of more than one seventh part of the heat energy produced in combustion under the boiler, applied equally to the thermo-electric battery, in which the heat, conducted from the hot points of juncture to the cold, constituted a formidable loss. The electromotive force of each thermo-electric element did not exceed 0.036 of a volt, and 1,800 elements were therefore necessary to work an incandescence lamp.
A most useful application of the thermo-electric battery for measuring radiant heat, the thermo pile, was exhibited. By means of an ingenious modification of the electrical pyrometer, named the bolometer, valuable researches in measuring solar radiations had been made by Professor Langley.
Faraday's great discovery of magneto-induction was next noticed, and the original instrument by which he had elicited the first electric spark before the members of the Royal Institution in 1831, was shown in operation. It was proved that although the individual current produced by magnetoinduction was exceedingly small and momentary in action, it was capable of unlimited multiplication by mechanical arrangements of a simple kind, and that by such multiplication the powerful effects of the dynamo machine of the present day were built up. One of the means for accomplishing such multiplication was the Siemens armature of 1856. Another step of importance was that involved in the Pacinotti ring, known in its practical application as the machine of Gramme. A third step, that of the self exciting principle, was first communicated by Dr. Werner Siemens to the Berlin Academy, on the 17th of January, 1867, and by the lecturer to the Royal Society, on the 4th of the following month. This was read on the 14th of February, when the late Sir Charles Wheatstone also brought forward a paper embodying the same principle. The lecturer's machine, which was then exhibited, and which might be looked upon as the first of its kind, was shown in operation; it had done useful work for many years as a means of exciting steel magnets. A suggestion contained in Sir Charles Wheatstone's paper, that "a very remarkable increase of all the effects, accompanied by a diminution in the resistance of the machine, is observed when a cross wire is placed so as to divert a great portion of the current from the electro-magnet," had led the lecturer to an investigation read before the Royal Society on the 4th of March, 1880, in which it was shown that by augmenting the resistance upon the electro-magnets 100 fold, valuable effects could be realized, as illustrated graphically by means of a diagram. The most important of these results consisted in this, that the electromotive force produced in a "shunt-wound machine," as it was called, increased with the external resistance, whereby the great fluctuations formerly inseparable from electric arc lighting could be obviated, and thus, by the double means of exciting the electro-magnets, still greater uniformity of current was attainable.
The conditions upon which the working of a well conceived dynamo machine must depend were next alluded to, and it was demonstrated that when losses by unnecessary wire resistance, by Foucault currents, and by induced currents in the rotating armature were avoided, as much as 90 per cent., or even more, of the power communicated to the machine was realized in the form of electric energy, and thatvice versathe reconversion of electric into mechanical energy could be accomplished with similarly small loss. Thus, by means of two machines at a moderate distance apart, nearly 80 per cent, of the power imparted to one machine could be again yielded in the mechanical form by the second, leaving out of consideration frictional losses, which latter need not be great, considering that a dynamo machine had only one moving part well balanced, and was acted upon along its entire circumference by propelling force. Jacobi had proved, many years ago, that the maximum efficiency of a magneto-electric engine was obtained when
e / E = w / W = ½
which law had been frequently construed, by Verdet (Theorie Mecanique de la Chaleur) and others, to mean that one-half was the maximum theoretical efficiency obtainable in electric transmission of power, and that one half of the current must be necessarily wasted or turned into heat. The lecturer could never be reconciled to a law necessitating such a waste of energy, and had maintained, without disputing the accuracy of Jacobi's law, that it had reference really to the condition of maximum work accomplished with a given machine, whereas its efficiency must be governed by the equation:
e / E = w / W = nearly 1
From this it followed that the maximum yield was obtained when two dynamo machines (of similar construction) rotated nearly at the same speed, but that under these conditions the amount of force transmitted was a minimum. Practically the best condition of working consisted in giving to the primary machine such proportions as to produce a current of the same magnitude, but of 50 per cent, greater electromotive force than the secondary; by adopting such an arrangement, as much as 50 per cent, of the power imparted to the primary could be practically received from the secondary machine at a distance of several miles. Professor Silvanus Thompson, in his recent Cantor Lectures, had shown an ingenious graphical method of proving these important fundamental laws.
The possibility of transmitting power electrically was so obvious that suggestions to that effect had been frequently made since the days of Volta, by Ritchie, Jacobi, Henry, Page, Hjorth, and others; but it was only in recent years that such transmission had been rendered practically feasible.
Just six years ago, when delivering his presidential address to the Iron and Steel Institute, the lecturer had ventured to suggest that "time will probably reveal to us effectual means of carrying power to great distances, but I cannot refrain from alluding to one which is, in my opinion, worthy of consideration, namely, the electrical conductor. Suppose water power to be employed to give motion to a dynamo-electrical machine, a very powerful electrical current will be the result, which may be carried to a great distance, through a large metallic conductor, and then be made to impart motion to electromagnetic engines, to ignite the carbon points of electric lamps, or to effect the separation of metals from their combinations. A copper rod 3 in. in diameter would be capable of transmitting 1,000 horse power a distance of say thirty miles, an amount sufficient to supply one-quarter of a million candle power, which would suffice to illuminate a moderately-sized town." This suggestion had been much criticised at the time, when it was still thought that electricity was incapable of being massed so as to deal with many horse power of effect, and the size of conductor he had proposed was also considered wholly inadequate. It would be interesting to test this early calculation by recent experience. Mr. Marcel Deprez had, it was well known, lately succeeded in transmitting as much as three horse power to a distance of 40 kilometers (25 miles) through a pair of ordinary telegraph wires of 4 millimeters in diameter. The results so obtained had been carefully noted by Mr. Tresca, and had been communicated a fortnight ago to the French Academy of Sciences. Taking the relative conductivity of iron wire employed by Deprez, and the 3 in. rod proposed by the lecturer, the amount of power that could be transmitted through the latter would be about 4,000 horse power. But Deprez had employed a motor-dynamo of 2,000 volts, and was contented with a yield of 32 per cent. only of the energy imparted to the primary machine, whereas he had calculated at the time upon an electromotive force of 200 volts, and upon a return of at least 40 per cent. of the energy imparted. In March, 1878, when delivering one of the Science Lectures at Glasgow, he said that a 2 in. rod could be made to accomplish the object proposed, because he had by that time conceived the possibility of employing a current of at least 500 volts. Sir William Thomson had at once accepted these views, and with the conceptive ingenuity peculiar to himself, had gone far beyond him, in showing before the Parliamentary Electric Light Committee of 1879, that through a copper wire of only ½ in. diameter, 21,000 horse power might be conveyed to a distance of 300 miles with a current of an intensity of 80,000 volts. The time might come when such a current could be dealt with, having a striking distance of about 12 ft. in air, but then, probably, a very practical law enunciated by Sir William Thomson would be infringed. This was to the effect that electricity was conveyed at the cheapest rate through a conductor, the cost of which was such that the annual interest upon the money expended equaled the annual expenditure for lost effect in the conductor in producing the power to be conveyed. It appeared that Mr. Deprez had not followed this law in making his recent installations.
Sir William Armstrong was probably first to take practical, advantage of these suggestions in lighting his house at Cragside during night time, and working his lathe and saw bench during the day, by power transmitted through a wire from a waterfall nearly a mile distant from his mansion. The lecturer had also accomplished the several objects of pumping water, cutting wood, hay, and swedes, of lighting his house, and of carrying on experiments in electro-horticulture from a common center of steam power. The results had been most satisfactory; the whole of the management had been in the hands of a gardener and of laborers, who were without previous knowledge of electricity, and the only repairs that had been found necessary were one renewal of the commutators and an occasional change of metallic contact brushes.
An interesting application of electric transmission to cranes, by Dr. Hopkinson, was shown in operation.
Among the numerous other applications of the electrical transmission of power, that to electrical railways, first exhibited by Dr. Werner Siemens, at the Berlin Exhibition of 1879, had created more than ordinary public attention. In it the current produced by the dynamo machine, fixed at a convenient station and driven by a steam engine or other motor, was conveyed to a dynamo placed upon the moving car, through a central rail supported upon insulating blocks of wood, the two working rails serving to convey the return current. The line was 900 yards long, of 2 ft gauge, and the moving car served its purpose of carrying twenty visitors through the exhibition each trip. The success of this experiment soon led to the laying of the Lichterfelde line, in which both rails were placed upon insulating sleepers, so that the one served for the conveyance of the current from the power station to the moving car, and the other for completing the return circuit. This line had a gauge of 3 ft. 3 in., was 2,500 yards in length, and was worked by two dynamo machines, developing an aggregate current of 9,000 watts, equal to 12 horse power. It had now been in constant operation since May 16, 1881, and had never failed in accomplishing its daily traffic. A line half a kilometer in length, but of 4 ft. 8½ in. gauge was established by the lecturer at Paris in connection with the Electric Exhibition of 1881. In this case, two suspended conductors in the form of hollow tubes with a longitudinal slit were adopted, the contact being made by metallic bolts drawn through these slit tubes, and connected with the dynamo machine on the moving car by copper ropes passing through the roof. On this line 95,000 passengers were conveyed within the short period of seven weeks.
An electric tramway, six miles in length, had just been completed, connecting Portrush with Bush Mills, in the north of Ireland, in the installation of which the lecturer was aided by Mr. Traill, as engineer of the company by Mr. Alexander Siemens, and by Dr. E. Hopkinson, representing his firm. In this instance the two rails, 3 ft. apart, were not insulated from the ground, but were joined electrically by means of copper staples and formed the return circuit, the current being conveyed to the car through a T iron placed upon short standards, and insulated by means of insulate caps. For the present the power was produced by a steam engine at Portrush, giving motion to a shunt-wound dynamo of 15,000 watts=20 horse power, but arrangements were in progress to utilize a waterfall of ample power near Bush Mills, by means of three turbines of 40 horse power each, now in course of erection. The working speed of this line was restricted by the Board of Trade to ten miles an hour, which was readily obtained, although the gradients of the line were decidedly unfavorable, including an incline of two miles in length at a gradient of 1 in 38. It was intended to extend the line six miles beyond Bush Mills, in order to join it at Dervock station with the north of Ireland narrow gauge railway system.
The electric system of propulsion was, in the lecturer's opinion, sufficiently advanced to assure practical success under suitable circumstances--such as for suburban tramways, elevated lines, and above all lines through tunnels; such as the Metropolitan and District Railways. The advantages were that the weight, of the engine, so destructive of power and of the plant itself in starting and stopping, would be saved, and that perfect immunity from products of combustion would be insured The experience at Lichterfelde, at Paris, and another electric line of 765 yards in length, and 2 ft. 2 in. gauge, worked in connection with the Zaukerode Colliery since October, 1882, were extremely favorable to this mode of propulsion. The lecturer however did not advocate its prospective application in competition with the locomotive engine for main lines of railway. For tramways within populous districts, the insulated conductor involved a serious difficulty. It would be more advantageous under these circumstances to resort to secondary batteries, forming a store of electrical energy carried under the seats of the car itself, and working a dynamo machine connected with the moving wheels by means of belts and chains.
The secondary battery was the only available means of propelling vessels by electrical power, and considering that these batteries might be made to serve the purpose of keel ballast, their weight, which was still considerable, would not be objectionable. The secondary battery was not an entirely new conception. The hydrogen gas battery suggested by Sir Wm. Grove in 1841, and which was shown in operation, realized in the most perfect manner the conception of storage, only that the power obtained from it was exceedingly slight. The lecturer, in working upon Sir Wm. Grove's conception, had twenty-five years ago constructed a battery of considerable power in substituting porous carbon for platinum, impregnating the same with a precipitate of lead peroxidized by a charging current. At that time little practical importance attached however to the object, and even when Plante, in 1860, produced his secondary battery, composed of lead plates peroxidized by a charging current, little more than scientific curiosity was excited. It was only since the dynamo machine had become an accomplished fact that the importance of this mode of storing energy had become of practical importance, and great credit was due to Faure, to Sellon, and to Volckmar for putting this valuable addition to practical science into available forms. A question of great interest in connection with the secondary battery had reference to its permanence. A fear had been expressed by many that local action would soon destroy the fabric of which it was composed, and that the active surfaces would become coated with sulphate of lead, preventing further action. It had, however, lately been proved in a paper read by Dr. Frankland before the Royal Society, corroborated by simultaneous investigations by Dr. Gladstone and Mr. Tribe, that the action of the secondary battery depended essentially upon the alternative composition and decomposition of sulphate of lead, which was therefore not an enemy, but the best friend to its continued action.
In conclusion, the lecturer referred to electric nomenclature, and to the means for measuring and recording the passage of electric energy. When he addressed the British Association at Southampton, he had ventured to suggest two electrical units additional to those established at the Electrical Congress in 1881, viz.: the watt and the joule, in order to complete the chain of units connecting electrical with mechanical energy and with the unit quantity of heat. He was glad to find that this suggestion had met with a favorable reception, especially that of the watt, which was convenient for expressing in an intelligible manner the effective power of a dynamo machine, and for giving a precise idea of the number of lights or effective power to be realized by its current, as well as of the engine power necessary to drive it; 746 watts represented 1 horse-power.
Finally, the watt meter, an instrument recently developed by his firm, was shown in operation. This consisted simply of a coil of thick conductor suspended by a torsion wire, and opposed laterally to a fixed coil of wire of high resistance. The current to be measured flowed through both coils in parallel circuit, the one representing its quantity expressible in amperes, and the other its potential expressible in volts. Their joint attractive action expressed therefore volt-amperes or watts, which were read off upon a scale of equal divisions.
The lecture was illustrated by experiments, and by numerous diagrams and tables of results. Measuring instruments by Professors Ayrton and Perry, by Mr. Edison and by Mr. Boys, were also exhibited.
[Footnote: Being an abstract of the introductory lecture to a course on photography at the Polytechnic Institute, November 11.]
Since the first announcement of these lectures, our Secretary has asked me to give a free introductory lecture, so that all who are interested in the subject may come and gather a better idea as to them than they can possibly do by simply leading a prospectus. This evening, therefore, I propose to give first a typical lecture of the course, and secondly, at its conclusion, to say a few words as to our principal object. As the subject for this evening's lecture I have chosen, "The Preparation of Gelatine Plates," as it is probably one of very general interest to photographers.
Before preparing our emulsion, we must first decide upon the particular materials we are going to use, and of these the first requisite is nitrate of silver. Nitrate of silver is supplied by chemists in three principal conditions:
1. The ordinary crystallized salt, prepared by dissolving silver in nitric acid, and evaporating the solution until the salt crystallizes out. This sample usually presents the appearance of imperfect crystals, having a faint yellowish tinge, and a strong odor of nitrous fumes, and contains, as might be expected, a considerable amount of free acid.
2. Fused nitrate, or "lunar caustic," prepared by fusing the crystallized salt and casting it into sticks. Lunar caustic is usually alkaline to test paper.
3. Recrystallized silver nitrate, prepared by redissolving the ordinary salt in distilled water, and again evaporating to the crystallizing point. By this means the impurities and free acid are removed.
I have a specimen of this on the table, and it consists, as you observe, of fine crystals which are perfectly colorless and transparent; it is also perfectly neutral to test paper. No doubt either of these samples can be used with success in preparing emulsions, but to those who are inexperienced, I recommend that the recrystallized salt be employed. We make, then, a solution of recrystallized silver nitrate in distilled water, containing in every 12 ounces of solution 1¼ ounces of the salt.
The next material we require is a soluble bromide. I have here specimens of various bromides which can be employed, such as ammonium, potassium, barium, and zinc bromides; as a rule, however, either the ammonium or potassium salt is used, and I should like to say a few words respecting the relative efficiency of these two salts.
1. As to ammonium bromide. This substance is a highly unstable salt. A sample of ammonium bromide which is perfectly neutral when first prepared will, on keeping, be found to become decidedly acid in character. Moreover, during this decomposition, the percentage of bromine does not remain constant; as a rule, it will be found to contain more than the theoretical amount of bromine. Finally, all ammonium salts have a most destructive action on gelatine; if gelatine, which has been boiled for a short time with either ammonium bromide or ammonium nitrate, be added to an emulsion, it will be found to produce pink fog--and probably frilling--on plates prepared with the emulsion. For these reasons, I venture to say that ammonium bromide, which figures so largely in formulæ for gelatine emulsions, is one of the worst bromides that can be employed for that purpose, and is, indeed, a frequent source of pink fog and frilling.
2. As to potassium bromide. This is a perfectly stable substance, can be readily obtained pure, and is constant in composition; neither has it (nor the nitrate) any appreciable destructive action on gelatine. We prepare, then, a solution of potassium bromide in water containing in every 12 ounces of solution 1 ounce of the salt. On testing it with litmus paper, the solution may be either slightly alkaline or neutral; in either case, it should be faintly acidified with hydrochloric acid.
The last material we require is the gelatine, one of the most important, and at the same time the most difficult substance to obtain of good quality. I have various samples here--notably Nelson's No. 1 and "X opaque;" Coignet's gold medal; Heinrich's; the Autotype Company's; and Russian isinglass.
The only method I know of securing a uniform quality of gelatine is to purchase several small samples, make a trial emulsion with each, and buy a stock of the sample which gives the best results. To those who do not care to go to this trouble, equal quantities of Nelson's No. 1 and X opaque, as recommended by Captain Abney, can be employed. Having selected the gelatine, 1¼ ounces should be allowed to soak in water, and then melted, when it will be found to have a bulk of about 6 ounces.
In order to prepare our emulsion, I take equal bulks of the silver nitrate and potassium bromide solutions in beakers, and place them in the water bath to get hot. I also take an equal bulk of hot water in a large beaker, and add to it one-half an ounce of the gelatine solution to every 12 ounces of water. Having raised all these to about 180° F., I add (as you observe) to the large beaker containing the dilute gelatine a little of the bromide, then, through a funnel having a fine orifice, a little of the silver, swirling the liquid round during the operation; then again some bromide and silver, and so on until all is added.
When this is completed, a little of the emulsion is poured on a glass plate, and examined by transmitted light; if the mixing be efficient, the light will appear--as it does here--of an orange or orange red color.
It will be observed that we keep the bromide in excess while mixing. I must not forget to mention that to those experienced in mixing, by far the best method is that described by Captain Abney in his Cantor lectures, of keeping the silver in excess.
The emulsion, being properly mixed, has now to be placed in the water bath, and kept at the boiling point for forty-five minutes. As, obviously, I cannot keep you waiting while this is done, I propose to divide our emulsion into two portions, allowing one portion to stew, and to proceed with the next operation with the remainder.
Supposing, then, this emulsion has been boiled, it is placed in cold water to cool. While it is cooling, let us consider for a moment what takes place during the boiling. It is found that during this time the emulsion undergoes two remarkable changes:
1. The molecules of silver bromide gradually aggregate together, forming larger and larger particles.
2. The emulsion increases rapidly in sensitiveness. Now what is the cause, in the first place, of this aggregation of molecules: and, in the second place, of the increase of sensitiveness? We know that the two invariably go together, so that we are right in concluding that the same cause produces both.
It might be thought that heat is the cause, but the same changes take place more slowly in the cold, so we can only say that heat accelerates the action, and hence must conclude that the prime cause is one of the materials in the emulsion itself.
Now, besides the silver bromide, we have in the emulsion water, gelatine, potassium nitrate, and a small excess of potassium bromide; and in order to find which of these is the cause, we must make different emulsions, omitting in succession each of these materials. Suppose we take an emulsion which has just been mixed, and, instead of boiling it, we precipitate the gelatine and silver bromide with alcohol; on redissolving the pellicle in the same quantity of water, we have an emulsion the same as previously, with the exception that the niter and excess of potassium bromide are absent. If such an emulsion be boiled, we shall find the remarkable fact that, however long it be boiled, the silver bromide undergoes no change, neither does the emulsion become any more sensitive. We therefore conclude, that either the niter or the small excess of potassium bromide, or both together, produce the change.
Now take portions of a similarly washed emulsion, and add to one portion some niter, and to another some potassium bromide; on boiling these we find that the one containing niter does not change, while that containing the potassium bromide rapidly undergoes the changes mentioned.
Here, then, by a direct appeal to experiment, we prove that to all appearance comparatively useless excess of potassium bromide is really one of the most important constituents of the emulsion.
The following table gives some interesting results respecting this action of potassium bromide: