SCIENTIFIC AMERICAN SUPPLEMENT NO. 385



NEW YORK, MAY 19, 1883

Scientific American Supplement. Vol. XV., No. 385.

Scientific American established 1845

Scientific American Supplement, $5 a year.

Scientific American and Supplement, $7 a year.

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TABLE OF CONTENTS.

I. NATURAL HISTORY.—Fishes of Cuban Waters.

Panax Victori.—1 Illustration.

A Note on Sap. By Prof. ATTFIELD.

The Crow.—Illustration.

The Praying Mantis and its Allies.—Illustration.

May Flies.—2 illustrations.

II. TECHNOLOGY.—A Quick Way to Ascertain the Focus of a Lens.—1 diagram.

The History of the Pianoforte. By A.J. HIPKINS.—Different parts of a pianoforte and their uses.—Inventor of the instrument and his "action."—First German piano-maker.—Square pianos.—Pianos of Broadwood, Backers, Stodart, and Erard.—Introduction of metal tubes, plates, bars, and frames.—Improvements of Meyer, the Steinways, Chickerings, and others.—Upright pianos.—Several figures.

III. MEDICINE AND HYGIENE.—The Poisonous Properties of Nitrate of Silver and a Recent Case of Poisoning with the Same. By H. A. MOTT, Jr.

Tubercle Bacilli in Sputa.

Malaria. By Dr. JAMES H. SALISBURY.—VIII. Local observations.—Effect of the sun on ague plants.—Investigations into the cause of ague.—Notes on marsh miasm.—Analysis of malari a plant.—Numerous figures.

IV. ENGINEERING.—Torpedo Boats.—Full page illustration.

Pictet's High Speed Boat.—Several figures and diagrams.

Initial Stability Indicator for Ships.—4 figures.

V. ELECTRICITY, LIGHT, AND HEAT.—Scrivanow's Chloride of Silver Pile.—2 figures.

On the Luminosity of Flame.

VI. CHEMISTRY.—New Bleaching Process, with Regeneration of the Baths Used. By M. BONNEVILLE.

Detection of Magenta, Archil, and Cudbear in Wine.

VII. ARCHITECTURE.—The Pantheon at Rome.

VIII. MISCELLANEOUS.—The Raphael Celebration at Rome.—3 Illustrations.

Great International Fisheries Exhibition.—1 figure.

Puppet Shows among the Greeks.—3 illustrations.

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THE RAPHAEL CELEBRATION AT ROME.

The most famous of Italian painters, Raffaele Sanzio, whom the world commonly calls Raphael, was born at Urbino, in Umbria, part of the Papal States, four hundred years ago. The anniversary was celebrated, on March 28, 1883, both in that town and in Rome, where he lived and worked, and where he died in 1520, with processions, orations, poetical recitations, performances of music, exhibitions of pictures, statues, and busts, visits to the tomb of the great artist in the Pantheon, and with banquets and other festivities. The King and Queen of Italy were present at the Capitol of Rome (the Palace of the City Municipality) where one part of these proceedings took place.



At ten o'clock in the morning a procession set forth from the Capitol to the Pantheon, to render homage at the tomb of Raphael. It was arranged in the following order: Two Fedeli, or municipal ushers, in picturesque costumes of the sixteenth century, headed the procession, carrying two laurel wreaths fastened with ribbons representing the colors of Rome, red and dark yellow; a company of Vigili, the Roman firemen; the municipal band; the standard of Rome, carried by an officer of the Vigili; and the banners of the fourteen quarters of the city. Then came the Minister of Public Instruction and the Minister of Public Works; the Syndic of Rome, Duke Leopoldo Torlonia; and the Prefect of Rome, the Marquis Gravina. The members of the communal giunta, the provincial deputation, and the communal and provincial council followed the principal authorities. Next in order came the presidents of Italian and foreign academies and art institutions, the president of the academy of the Licei, the representatives of all the foreign academies, the members of the academy of St. Luke, the general direction of antiquities, the members of the Permanent Commission of Fine Arts, the members of the Communal Archological Commission, the guardians of the Pantheon, the members of the International Artistic Club, presided over by Prince Odescalchi; the members of the art schools, the pupils of the San Michele and Termini schools with their bands, the pupils of the elementary and female art schools. The procession was rendered more interesting by the presence of many Italian and foreign artists. Having arrived at the Pantheon, the chief personages took their place in front of Raphael's tomb. Every visitor to Rome knows this tomb, which is situated behind the third chapel on the left of the visitor entering the Pantheon. The altar was endowed by Raphael, and behind it is a picture of the Virgin and Child, known as the Madonna del Sasso, which was executed at his request and was produced by Lorenzo Lotto, a friend and pupil of the great painter. Above the inscription usually hang a few small pictures, which were presented by very poor artists who thought themselves cured by prayers at the shrine. This is confirmed by a crutch hanging up close to the pilaster. The bones of Raphael are laid in this tomb since 1520, with an epitaph recording the esteem in which he was held by Popes Julius II. and Leo X.; but they have not always been allowed to lie undisturbed. On Sept. 14, 1833, the tomb was opened to inspect the mouldering skeleton, of which drawings were made, and are reproduced in two of our illustrations. The proceedings at the tomb in the recent anniversary visit were brief and simple; a number of laurel or floral wreaths were suspended there, one sent by the president and members of the Royal Academy of London; and the Syndic of Rome unveiled a bronze bust of Raphael, which had been placed in a niche at the side.



This ceremony at the Pantheon was concluded by all visitors writing their names on two albums which had been placed near Victor Emmanuel's tomb and Raphael's tomb. The commemoration in the hall of the Horatii and Curiatii in the Capitol was a great success, their Majesties, the Ministers, the members of the diplomatic body, and a distinguished assembly being present. Signor Quirino Leoni read an admirable discourse on Raphael and his times.

The ancient city of Urbino, Raphael's birthplace, has fallen into decay, but has remembered its historic renown upon this occasion. The representatives of the Government and municipal authorities, and delegates of the leading Italian cities went in procession to visit the house where Raphael was born. Commemoration speeches were pronounced in the great hall of the ducal palace by Signor Minghetti and Senator Massarani. The commemoration ended with a cantata composed by Signor Rossi. The Via Raffaelle was illuminated in the evening, and a gala spectacle was given at the Sanzio Theater. Next day the exhibition of designs for a monument to Raphael was inaugurated at Urbino, and at night a great torchlight procession took place.—Illustrated London News.



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THE PANTHEON AT ROME.

The edifice known as the Pantheon, in Rome, is one of the best preserved specimens of Roman architecture. It was erected in the year 26 B.C., and is therefore now about one thousand nine hundred years old. It was consecrated as a Christian church in the year 608. Its rotunda is 143 ft. in diameter and also 143 ft. high. Its portico is remarkable for the elegance and number of its Corinthian columns.

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Seor Felipe Poey, a famous ichthyologist of Cuba, has recently brought out an exhaustive work upon the fishes of Cuban waters, in which he describes and depicts no fewer than 782 distinct varieties, although he admits some doubts about 105 kinds, concerning which he has yet to get more exact information. There can be no question, however, he claims, about the 677 species remaining, more than half of which he first described in previous works upon this subject, which has been the study of his life.

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THE GREAT INTERNATIONAL FISHERIES EXHIBITION.

Her Majesty the Queen has appointed the 12th of May for the opening of the International Fisheries Exhibition, which an influential and energetic committee, under the active presidency of the Prince of Wales, had developed to a magnitude undreamt of by those concerned in its early beginnings.

The idea of an international Fisheries Exhibition arose out of the success of the show of British fishery held at Norwich a short time ago; and the president and executive of the latter formed the nucleus of the far more powerful body by whom the present enterprise has been brought about.

The plan of the buildings embraces the whole of the twenty-two acres of the Horticultural Gardens; the upper half, left in its usual state of cultivation, will form a pleasant lounge and resting place for visitors in the intervals of their study of the collections. This element of garden accommodation was one of the most attractive features at the Paris Exhibition of 1878.

As the plan of the buildings is straggling and extended, and widely separates the classes, the most convenient mode of seeing the show will probably be found by going through the surrounding buildings first, and then taking the annexes as they occur.



On entering the main doors in the Exhibition Road, we pass through the Vestibule to the Council Room of the Royal Horticultural Society, which has been decorated for the reception of marine paintings, river subjects, and fish pictures of all sorts, by modern artists.

Leaving the Fine Arts behind, the principal building of the Exhibition is before us—that devoted to the deep sea fisheries of Great Britain. It is a handsome wooden structure, 750 feet in length, 50 feet wide, and 30 feet at its greatest height. The model of this, as well as of the other temporary wooden buildings, is the same as that of the annexes of the great Exhibition of 1862.

On our left are the Dining Rooms with the kitchens in the rear. The third room, set apart for cheap fish dinners (one of the features of the Exhibition), is to be decorated at the expense of the Baroness Burdett Coutts, and its walls are to be hung with pictures lent by the Fishmongers' Company, who have also furnished the requisite chairs and tables, and have made arrangements for a daily supply of cheap fish, while almost everything necessary to its maintenance (forks, spoons, table-linen, etc.) will be lent by various firms.

The apsidal building attached is to be devoted to lectures on the cooking of fish.

Having crossed the British Section, and turning to the right and passing by another entrance, we come upon what will be to all one of the most interesting features of the Exhibition, and to the scientific student of ichthyology a collection of paramount importance. We allude to the Western Arcade, in which are placed the Aquaria, which have in their construction given rise to more thoughtful care and deliberation than any other part of the works. On the right, in the bays, are the twenty large asphalt tanks, about 12 feet long, 3 feet wide, and 3 feet deep. These are the largest dimensions that the space at command will allow, but it is feared by some that it will be found somewhat confined for fast going fish. Along the wall on the left are ranged twenty smaller or table tanks of slate, which vary somewhat in size; the ten largest are about 5 feet 8 inches long, 2 feet 9 inches wide, and 1 foot 9 inches deep.

In this Western Arcade will be found all the new inventions in fish culture—models of hatching, breeding, and rearing establishments, apparatus for the transporting of fish, ova, models and drawings of fish-passes and ladders, and representations of the development and growth of fish. The chief exhibitors are specialists, and are already well known to our readers. Sir James Gibson Maitland has taken an active part in the arrangement of this branch, and is himself one of the principal contributors.

In the north of the Arcade, where it curves toward the Conservatory, will be shown an enormous collection of examples of stuffed fish, contributed by many prominent angling societies. In front of these on the counter will be ranged microscopic preparations of parasites, etc., and a stand from the Norwich Exhibition of a fauna of fish and fish-eating birds.

Passing behind the Conservatory and down the Eastern Arcade—in which will be arranged alg, sponges, mollusca, star-fish, worms used for bait, insects which destroy spawn or which serve as food for fish, etc.—on turning to the left, we find ourselves in the fish market, which will probably vie with the aquaria on the other side in attracting popular attention. This model Billingsgate is to be divided into two parts, the one for the sale of fresh, the other of dried and cured fish.

Next in order come the two long iron sheds appropriated respectively to life-boats and machinery in motion. Then past the Royal pavilion (the idea of which was doubtless taken from its prototype at the Paris Exhibition) to the southern end of the central block, which is shared by the Netherlands and Newfoundland; just to the north of the former Belgium has a place.

While the Committee of the Netherlands was one of the earliest formed, Belgium only came in at the eleventh hour; she will, however, owing to the zealous activity of Mr. Lenders, the consul in London, send an important contribution worthy of her interest in the North Sea fisheries. We ought also to mention that Newfoundland is among those colonies which have shown great energy, and she may be expected to send a large collection.

Passing northward we come to Sweden and Norway, with Chili between them. These two countries were, like the Netherlands, early in preparing to participate in the Exhibition. Each has had its own committee, which has been working hard since early in 1882.

Parallel to the Scandinavian section is that devoted to Canada and the United States, and each will occupy an equal space—ten thousand square feet.

In the northern Transept will be placed the inland fisheries of the United Kingdom. At each end of the building is aptly inclosed a basin formerly standing in the gardens: and over the eastern one will be erected the dais from which the Queen will formally declare the Exhibition open.

Shooting out at right angles are the Spanish annex, and the building shared by India and Ceylon. China and Japan and New South Wales; while corresponding to those at the western end are the Russian annex, and a shed allotted to several countries and colonies. The Isle of Man, the Bahamas, Switzerland, Germany, Hawaii, Italy, and Greece—all find their space under its roof.

After all the buildings were planned, the Governments of Russia and Spain declared their intention of participating; and accordingly for each of these countries a commodious iron building has been specially erected.

The Spanish collection will be of peculiar interest; it has been gathered together by a Government vessel ordered round the coast for the purpose, and taking up contributions at all the seaports as it passed.

Of the countries whose Governments for inscrutable reasons of state show disfavor and lack of sympathy, Germany is prominent; although by the active initiative of the London Committee some important contributions have been secured from private individuals; among them, we are happy to say, is Mr. Max von dem Borne, who will send his celebrated incubators, which the English Committee have arranged to exhibit in operation at their own expense.

Although the Italian Government, like that of Germany, holds aloof, individuals, especially Dr. Dohrn, of the Naples Zoological Station, will send contributions of great scientific value.

In the Chinese and Japanese annex, on the east, will be seen a large collection of specimens (including the gigantic crabs), which have been collected, to great extent, at the suggestion of Dr. Gnther, of the British Museum.

It is at the same time fortunate and unfortunate that a similar Fisheries Exhibition is now being held at Yokohama, as many specimens which have been collected specially for their own use would otherwise be wanting; and on the other hand, many are held back for their own show.

China, of all foreign countries, was the first to send her goods, which arrived at the building on the 30th of March, accompanied by native workmen who are preparing to erect over a basin contiguous to their annex models of the summer house and bridge with which the willow pattern plate has made us familiar; while on the basin will float models of Chinese junks.

Of British colonies, New South Wales will contribute a very interesting collection placed under the care of the Curator of the Sydney Museum; and from the Indian Empire will come a large gathering of specimens in spirits under the superintendence of Dr. Francis Day.

Of great scientific interest are the exhibits, to be placed in two neighboring sheds, of the Native Guano Company and the Millowners' Association. The former will show all the patents used for the purification of the rivers from sewage, and the latter will display in action their method of rendering innocuous the chemical pollutions which factories pour into the river.

In the large piece of water in the northern part of the gardens, which has been deepened on purpose, apparatus in connection with diving will be seen; and hard by, in a shed, Messrs. Siebe, Gorman & Co. will show a selection of beautiful minute shells dredged from the bottom of the Mediterranean.

In the open basins in the gardens will be seen beavers, seals, sea-lions, waders, and other aquatic birds.

From this preliminary walk round enough has, we think, been seen to show that the Great International Fisheries Exhibition will prove of interest alike to the ordinary visitor, to those anxious for the well-being of fishermen, to fishermen themselves of every degree, and to the scientific student of ichthyology in all its branches.—Nature.

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PUPPET SHOWS AMONG THE GREEKS.

The ancients, especially the Greeks, were very fond of theatrical representations; but, as Mr. Magnin has remarked in his Origines du Thtre Moderne, public representations were very expensive, and for that very reason very rare. Moreover, those who were not in a condition of freedom were excluded from them; and, finally, all cities could not have a large theater, and provide for the expenses that it carried with it. It became necessary, then, for every day needs, for all conditions and for all places, that there should be comedians of an inferior order, charged with the duty of offering continuously and inexpensively the emotions of the drama to all classes of inhabitants.

Formerly, as to-day, there were seen wandering from village to village menageries, puppet shows, fortune tellers, jugglers, and performers of tricks of all kinds. These prestidigitators even obtained at times such celebrity that history has preserved their names for us—at least of two of them, Euclides and Theodosius, to whom statues were erected by their contemporaries. One of these was put up at Athens in the Theater of Bacchus, alongside of that of the great writer of tragedy, schylus, and the other at the Theater of the Istiaians, holding in the hand a small ball. The grammarian Athenus, who reports these facts in his "Banquet of the Sages," profits by the occasion to deplore the taste of the Athenians, who preferred the inventions of mechanics to the culture of mind and histrions to philosophers. He adds with vexation that Diophites of Locris passed down to posterity simply because he came one day to Thebes wearing around his body bladders filled with wine and milk, and so arranged that he could spurt at will one of these liquids in apparently drawing it from his mouth. What would Athenus say if he knew that it was through him alone that the name of this histrion had come down to us?



Philo, of Byzantium, and Heron, of Alexandria, to whom we always have to have recourse when we desire accurate information as to the mechanic arts of antiquity, both composed treatises on puppet shows. That of Philo is lost, but Heron's treatise has been preserved to us, and has recently been translated in part by Mr. Victor Prou.

According to the Greek engineer, there were several kinds of puppet shows. The oldest and simplest consisted of a small stationary case, isolated on every side, in which the stage was closed by doors that opened automatically several times to exhibit the different tableaux. The programme of the representation was generally as follows: The first tableau showed a head, painted on the back of the stage, which moved its eyes, and lowered and raised them alternately. The door having been closed, and then opened again, there was seen, instead of the head, a group of persons. Finally, the stage opened a third time to show a new group, and this finished the representation. There were, then, only three movements to be made, that of the doors, that of the eyes, and that of the change of background.

As such representations were often given on the stages of large theaters, a method was devised later on of causing the case to start from the scenes behind which it was bidden from the spectators, and of moving automatically to the front of the stage, where it exhibited in succession the different tableaux; after which it returned automatically behind the scenes. Here is one of the scenes indicated by Heron, entitled the "Triumph of Bacchus":

The movable case shows, at its upper part, a platform from which arises a cylindrical temple, the roof of which, supported by six columns, is conical and surmounted by a figure of Victory with spread wings and holding a crown in her right hand. In the center of the temple Bacchus is seen standing, holding a thyrsus in his left hand, and a cup in his right. At his feet lies a panther. In front of and behind the god, on the platform of the stage, are two altars provided with combustible material. Very near the columns, but external to them, there are bacchantes placed in any posture that may be desired. All being thus prepared, says Heron, the automatic apparatus is set in motion. The theater then moves of itself to the spot selected, and there stops. Then the altar in front of Jupiter becomes lighted, and, at the same time, milk and water spurt from his thyrsus, while his cup pours wine over the panther. The four faces of the base become encircled with crowns, and, to the noise of drums and cymbals, the bacchantes dance round about the temple. Soon, the noise having ceased, Victory on the top of the temple, and Bacchus within it, face about. The altar that was behind the god is now in front of him, and becomes lighted in its turn. Then occurs another outflow from the thyrsus and cup, and another round of the bacchantes to the sound of drums and cymbals. The dance being finished, the theater returns to its former station. Thus ends the apotheosis.

I shall try to briefly indicate the processes which permitted of these different operations being performed, and which offer a much more general interest than one might at first sight be led to believe; for almost all of them had been employed in former times for producing the illusions to which ancient religions owed their power.

The automatic movement of the case was obtained by means of counterpoises and two cords wound about horizontal bobbins in such a way as to produce by their winding up a forward motion in a vertical plane, and subsequently a backward movement to the starting place. Supposing the motive cords properly wound around vertical bobbins, instead of a horizontal one, and we have the half revolution of Bacchus and Victory, as well as the complete revolution of the bacchantes.

The successive lighting of the two altars, the flow of milk and wine, and the noise of drums and cymbals were likewise obtained by the aid of cords moved by counterpoises, and the lengths of which were graduated in such a way as to open and close orifices, at the proper moment, by acting through traction on sliding valves which kept them closed.

Small pieces of combustible material were piled up beforehand on the two altars, the bodies of which were of metal, and in the interior of which were hidden small lamps that were separated from the combustible by a metal plate which was drawn aside at the proper moment by a small chain. The flame, on traversing the orifice, thus communicated with the combustible.

The milk and wine which flowed out at two different times through the thyrsus and cup of Bacchus came from a double reservoir hidden under the roof of the temple, over the orifices. The latter communicated, each of them, with one of the halves of the reservoir through two tubes inserted in the columns of the small edifice. These tubes were prolonged under the floor of the stage, and extended upward to the hands of Bacchus. A key, maneuvered by cords, alternately opened and closed the orifices which gave passage to the two liquids.

As for the noise of the drums and cymbals, that resulted from the falling of granules of lead, contained in an invisible box provided with an automatic sliding-valve, upon an inclined tambourine, whence they rebounded against little cymbals in the interior of the base of the car.



Finally, the crowns and garlands that suddenly made their appearance on the four faces of the base of the stage were hidden there in advance between the two walls surrounding the base. The space thus made for the crowns was closed beneath, along each face, by a horizontal trap moving on hinges that connected it with the inner wall of the base, but which was held temporarily stationary by means of a catch. The crowns were attached to the top of their compartment by cords that would have allowed them to fall to the level of the pedestal, had they not been supported by the traps.

At the desired moment, the catch, which was controlled by a special cord, ceased to hold the trap, and the latter, falling vertically, gave passage to the festoons and crowns that small leaden weights then drew along with all the quickness necessary.

Two points here are specially worthy of attracting our attention, and these are the flow of wine or milk from the statue of Bacchus, and the spontaneous lighting of the altar. These, in fact, were the two illusions that were most admired in ancient times, and there were several processes of performing them. Father Kircher possessed in his museum an apparatus which he describes in Oedipus Egyptiacus (t. ii., p. 333), and which probably came from some ancient Egyptian temple. (Fig. 1.)

It consisted of a hollow hemispherical dome, supported by four columns, and placed over the statue of the goddess of many breasts. To two of these columns were adapted movable brackets, at whose extremities there were fixed lamps. The hemisphere was hermetically closed underneath by a metal plate. The small altar which supported the statue, and which was filled with milk, communicated with the interior of the statue by a tube reaching nearly to the bottom. The altar likewise communicated with the hollow dome by a tube having a double bend. At the moment of the sacrifice the two lamps were lighted and the brackets turned so that the flames should come in contact with and heat the bottom of the dome. The air contained in the latter, being dilated, issued through the tube, X M, pressed on the milk contained in the altar, and caused it to rise through the straight tube into the interior of the statue as high as the breasts. A series of small conduits, into which the principal tube divided, carried the liquid to the breasts, whence it spurted out, to the great admiration of the spectators, who cried out at the miracle. The sacrifice being ended, the lamps were put out, and the milk ceased to flow.

Heron, of Alexandria, describes in his Pneumatics several analogous apparatus. Here is one of them. (We translate the Greek text literally.)



"To construct an altar in such a way that, when a fire is lighted thereon, the statues at the side of it shall make libations. (Fig. 2.)

"Let there be a pedestal. A B [Gamma] [Delta], on which are placed statues, and an altar, E Z H, closed on every side. The pedestal should also be hermetically closed, but is communicated with the altar through a central tube. It is traversed likewise by the tube, e [Lambda] (in the interior of the statue to the right), not far from the bottom which terminates in a cup held by the statue, e. Water is poured into the pedestal through a hole, M, which is afterward corked up.

"If, then, a fire be lighted on the altar, the internal air will be dilated and will enter the pedestal and drive out the water contained in it. But the latter, having no other exit than the tube, e [Lambda], will rise into the cup, and so the statue will make a libation. This will last as long as the fire does. On extinguishing the fire the libation ceases, and occurs anew as often as the fire is relighted.

"It is necessary that the tube through which the heat is to introduce itself shall be wider in the middle; and it is necessary, in fact, that the heat, or rather that the draught that it produces, shall accumulate in an inflation in order to have more effect."

According to Father Kircher (l. c.), an author whom he calls Bitho reports that there was at Sais a temple of Minerva in which there was an altar on which, when a fire was lighted, Dyonysos and Artemis (Bacchus and Diana) poured milk and wine, while a dragon hissed.

It is easy to conceive of the modification to be introduced into the apparatus above described by Heron, in order to cause the outflow of milk from one side and of wine from the other.

After having indicated it, Father Kircher adds: "It is thus that Bacchus and Diana appeared to pour, one of them wine, and the other milk, and that the dragon seemed to applaud their action by hisses. As the people who were present at the spectacle did not see what was going on within, it is not astonishing that they believed it due to divine intervention. We know, in fact, that Osiris or Bacchus was considered as the discoverer of the vine and of milk; that Iris was the genius of the waters of the Nile; and that the Serpent, or good genius, was the first cause of all these things. Since, moreover, sacrifices had to be made to the gods in order to obtain benefits, the flow of milk, wine, or water, as well as the hissing of the serpent, when the sacrificial flame was lighted, appeared to demonstrate clearly the existence of the gods."

In another analogous apparatus of Heron's, it is steam that performs the role that we have just seen played by dilated air. But the ancients do not appear to have perceived the essential difference, as regards motive power, that exists between these two agents; indeed, their preferences were wholly for air, although the effects produced were not very great. We might cite several small machines of this sort, but we shall confine ourselves to one example that has some relation to our subject. This also is borrowed from Heron's Pneumatics. (Fig. 3.)

"Fire being lighted on an altar, figures will appear to execute a round dance. The altars should be transparent, and of glass or horn. From the fire-place there starts a tube which runs to the base of the altar, where it revolves on a pivot, while its upper part revolves in a tube fixed to the fire-place. To the tube there should be adjusted other tubes (horizontal) in communication with it, which cross each other at right angles, and which are bent in opposite directions at their extremities. There is likewise fixed to it a disk upon which are attached figures which form a round. When the fire of the altar is lighted, the air, becoming heated, will pass into the tube; but being driven from the latter, it will pass through the small bent tubes and ... cause the tube as well as the figures to revolve."

Father Kircher, who had at his disposal either many documents that we are not acquainted with, or else a very lively imagination, alleges (Oedip. g., t. ii., p. 338) that King Menes took much delight in seeing such figures revolve.

Nor are the examples of holy fire-places that kindled spontaneously wanting in antiquity.

Pliny (Hist. Nat., ii., 7) and Horace (Serm., Sat. v.) tell us that this phenomenon occurred in the temple of Gnatia, and Solin (Ch. V.) says that it was observed likewise on an altar near Agrigentum. Athenus (Deipn. i., 15) says that the celebrated prestidigitator, Cratisthenes, of Phlius, pupil of another celebrated prestidigitator named Xenophon, knew the art of preparing a fire which lighted spontaneously.

Pausanias tells us that in a city of Lydia, whose inhabitants, having fallen under the yoke of the Persians, had embraced the religion of the Magi, "there exists an altar upon which there are ashes which, in color, resemble no other. The priest puts wood on the altar, and invokes I know not what god by harangues taken from a book written in a barbarous tongue unknown to the Greeks, when the wood soon lights of itself without fire, and the flame from it is very clear."

The secret, or rather one of the secrets of the Magi, has been revealed to us by one of the Fathers of the Church (Saint Hippolytus, it is thought), who has left, in a work entitled Philosophumena, which is designed to refute the doctrines of the pagans, a chapter on the illusions of their priests. According to him, the altars on which this miracle took place contained, instead of ashes, calcined lime and a large quantity of incense reduced to powder; and this would explain the unusual color of the ashes observed by Pausanias. The process, moreover, is excellent; for it is only necessary to throw a little water on the lime, with certain precautions, to develop a heat capable of setting on fire incense or any other material that is more readily combustible, such as sulphur and phosphorus. The same author points out still another means, and this consists in hiding firebrands in small bells that were afterward covered with shavings, the latter having previously been covered with a composition made of naphtha and bitumen (Greek fire). As may be seen, a very small movement sufficed to bring about combustion.—A. De Rochas, in La Nature.

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TORPEDO BOATS.

There are several kinds of torpedoes. The one which is most used in the French navy is called the "carried" torpedo (torpille porte), thus named because the torpedo boat literally carries it right under the sides of the enemy's ship. It consists of a cartridge of about 20 kilogrammes of gun cotton, placed at the extremity of an iron rod, 12 meters in length, projecting in a downward direction from the fore part of the boat. The charge is fired by an electric spark by means of an apparatus placed in the lookout compartment. Our engraving represents an attack on an ironclad by means of one of these torpedoes. Under cover of darkness, the torpedo boat has been enabled to approach without being disabled by the projectiles from the revolving guns of the man-of-war, and has stopped suddenly and ignited the torpedo as soon as the latter came in contact with the enemy's hull.

The water spout produced by the explosion sometimes completely covers the torpedo boat, and the latter would be sunk by it were not all apertures closed so as to make her a true buoy. What appears extraordinary is that the explosion does not prove as dangerous to the assailant as to the adversary. To understand this it must be remembered that, although the material with which the cartridges are filled is of an extreme shattering nature, and makes a breach in the most resistant armor plate, when in contact with it, yet, at a distance of a few meters, no other effect is felt from it than the disturbance caused by the water. This is why a space of 12 meters, represented by the length of the torpedo spar, is sufficient to protect the torpedo boat. The attack of an ironclad, however, under the conditions that we have just described, is, nevertheless, a perilous operation, and one that requires men of coolness, courage, and great experience.



There is another system which is likewise in use in the French navy, and that is the Whitehead torpedo. This consists of a metallic cylinder, tapering at each end, and containing not only a charge of gun cotton, but a compressed air engine which actuates two helices. It is, in fact, a small submarine vessel, which moves of itself in the direction toward which it has been launched, and at a depth that has been regulated beforehand by a special apparatus which is a secret with the inventor. The torpedo is placed in a tube situated in the fore part of the torpedo boat, and whence it is driven out by means of compressed air. Once fired, it makes its way under the surface to the spot where the shock of its point is to bring about an explosion, and the torpedo boat is thus enabled to operate at a distance and avoid the dangers of an immediate contact with the enemy. Unfortunately this advantage is offset by grave drawbacks; for, in the first place, each of the Whitehead torpedoes costs about ten thousand francs, without counting the expense of obtaining the right to use the patent, and, in the second place, its action is very uncertain, since currents very readily change its direction. However this may be, the inventor has realized a considerable sum by the sale of his secret to the different maritime powers, most of whom have adopted his system.

All our ports are provided with flotillas and torpedo boats, and with schools in which the officers and men charged with this service are trained by frequent exercises. It was near L'Orient, at Port Louis, that we were permitted to be witnesses of these maneuvers, and where we saw the torpedo boats that were lying in ambush behind Rohellan Isle glide between the rocks, all of which appeared familiar to them, and start out seaward at the first signal. It was here, too, that we were witnesses of the sham attack against a pleasure yacht, shown in one of our engravings. A torpedo boat, driven at full speed, stopped at one meter from the said yacht with a precision that denoted an oft-repeated study.



Before we close, we must mention some very recent experiments that have been made with a torpedo analogous to Whitehead's, that is to say, one that runs alone by means of helices actuated by compressed air, but having the great advantage that it can be steered at a distance from the very place whence it has been launched. This extraordinary result is obtained by the use of a rudder actuated by an electric current which is transmitted by a small metallic cable wound up in the interior of the torpedo, and paying out behind as the torpedo moves forward on its mission. The operator, stationed at the starting point, is obliged to follow the torpedo's course with his eyes in order to direct it during its submarine voyage. For this reason the torpedo carries a vertical mast, that projects above the surface, and at the top of which is placed a lantern, whose light is thrown astern but is invisible from the front, that is, from the direction of the enemy. A trial of this ingenious invention was made a few weeks ago on the Bosphorus, with complete success, as it appears. From the shore where the torpedo was put into the water, the weapon was steered with sufficient accuracy to cause it to pass, at a distance of two kilometers, between two vessels placed in observation at a distance apart of ten meters. After this, it was made to turn about so as to come back to its starting point. What makes this result the more remarkable is that the waters of the Bosphorus are disturbed by powerful currents that run in different directions, according to the place.—L'Illustration.

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PICTET'S HIGH SPEED BOAT.

It is now nearly a year ago since we announced to our readers the researches that had been undertaken by the learned physicist, Raoul Pictet, in order to demonstrate theoretically and practically the forms that are required for a fast-sailing vessel, and since we pointed out how great an interest is connected with the question, while at the same time promising to revert to the subject at some opportune moment. We shall now keep our promise by making known a work that Mr. Pictet has just published in the Archives Physiques et Naturelles, of Geneva, in which he gives the first results of his labors, and which we shall analyze rapidly, neglecting in doing so the somewhat dry mathematical part of the article.

For a given tonnage and identical tractive stresses, the greater or less sharpness of the fore and aft part of the keel allows boats to attain different speeds, the sharper lines corresponding to the highest speeds, but, in practice, considerably diminishing the weight of freight capable of being carried by the boat.



Mr. Pictet proposed the problem to himself in a different manner, and as follows:

Determine by analysis, and verify experimentally, what form of keel will allow of the quickest and most economical carriage of a given weight of merchandise on water.

We know that for a given transverse or midship section, the tractive stress necessary for the progression of the ship is proportional to the square of the velocity; and the motive power, as a consequence, to the cube of such velocity.



The friction of water against the polished surfaces of the vessel's sides has not as yet been directly measured, but some indirect experiments permit us to consider the resistances due thereto as small. The entire power expended for the progress of the vessel is, then, utilized solely in displacing certain masses of water and in giving them a certain amount of acceleration. The masses of water set in motion depend upon the surface submerged, and their acceleration depends upon the speed of the vessel. Mr. Pictet has studied a form of vessel in which the greatest part possible of the masses of water set in motion shall be given a vertical acceleration, and the smallest part possible a horizontal one; and this is the reason why: All those masses of water which shall receive a vertical acceleration from the keel will tend to move downward and produce a vertical reaction in an upward direction applied to the very surface that gives rise to the motion. Such reaction will have the effect of changing the level of the floating body; of lifting it while relieving it of a weight exactly equal to the value of the vertical thrust; and of diminishing the midship section, and, consequently, the motive power.



All those masses of water which receive a horizontal acceleration from the keel run counter, on the contrary, to the propulsive stress, and it becomes of interest, therefore, to bring them to a minimum. The vertical stress is limited by the weight of the boat, and, theoretically, with an infinite degree of speed, the boat would graze the water without being able to enter it.

The annexed diagram (Fig. 1) shows the form that calculation has led Mr. Pictet to. The sides of the boat are two planes parallel with its axis, and perfectly vertical. The keel (properly so called) is formed by the joining of the two vertical planes. The surface thus formed is a parabola whose apex is in front, the maximum ordinate behind, and the concavity directed toward the bottom of the water. The stern is a vertical plane intersecting at right angles the two lateral faces and the parabolic curve, which thus terminates in a sharp edge. The prow of the boat is connected with the apex of the parabola by a curve whose concavity is directed upward.



When we trace the curve of the tractive stresses in a boat thus constructed, by putting the speeds in abscisses and the tractive stresses in ordinates, we obtain a curve (Fig. 2) which shows that the same tractive stress applied to a boat may give it three different speeds, M, M', and M'', only two of which, M and M'', are stable.

Experimental verifications of this study have been partially realized (thanks to the financial aid of a number of persons who are interested in the question) through the construction of a boat (Fig. 1) by the Geneva Society for the Construction of Physical Instruments. The vessel is 20.25 m. in length at the water line, has an everywhere equal width of 3.9 m., and a length of 16 m. from the stern to the apex of the parabola of the keel. The bottom of the boat is nearly absolutely flat. The keel, which is 30 centimeters in width, contains the shaft of the screw. The boiler, which is designed for running at twelve atmospheres, furnishes steam to a two cylinder engine, which may be run at will, either the two cylinders separately, or as a compound engine. The bronze screw is 1.3 m. in diameter, and has a pitch of 2.5 m. The vessel has two rudders, one in front for slight speeds, and the other at the stern. At rest, the total displacement is 52,300 kilogrammes. This weight far exceeds what was first expected, by reason of the superthickness given the iron plates of the vertical sides, of the supplementary cross bracing, and of the superposition of the netting necessary to resist the flexion of the whole. On another hand, the tractive stress of the screw, which should reach about 4,000 kilogrammes, has never been able to exceed 1,800, because of the numerous imperfections in the engine. It became necessary, therefore, to steady the vessel by having her towed by the Winkelried, which was chartered for such a purpose, to the General Navigation Company. It became possible to thus carry on observations on speeds up to 27 kilometers per hour.

Fig. 3 shows how the tractive stress varies with each speed in a theoretic case (dotted curve) in which the stress is proportional to the square of the speed, in Madame Rothschild's boat, the Gitana (curve E), and in the Pictet high speed vessel (curve B).

The Gitana was tried with speeds varying between 0 and 4 kilometers. The corresponding tractive stresses have been reduced to the same transverse section as in the Pictet model in order to render the observations comparable. At slight speeds, and up to 19.5 kilometers per hour, the Gitana, which is the sharper, runs easier and requires a slighter tractive stress. At such a speed there is an equality; but, beyond this, the Pictet boat presents the greater advantages, and, at a speed of 27 kilometers, requires a stress about half less than does the Gitana. Such results explain themselves when we reflect that at these great speeds the Gitana sinks to such a degree that the afterside planks are at the level of the water, while the Pictet model rises simultaneously fore and aft, thus considerably diminishing the submerged section.

With low or moderate speeds there is a perceptible equality between the theoretic curve and the curve of the fast boat; but, starting from 16 kilometers, the stress diminishes. The greater does the speed become, the more considerable is the diminution in stress; and, starting from a certain speed, the rise of the boat is such as to diminish its absolute tractive stress—a fact of prime importance established by theory and confirmed by experiment.

The curves in Fig. 4 show the power in horses necessary to effect progression at different speeds. The curve, A, has reference to an ordinary boat that preserves its water lines constant, and the curve, B, to a swift boat of the same tonnage. Up to 16 kilometers, the swift vessel presents no advantage; but beyond that speed, the advantage becomes marked, and, at a speed of 27 kilometers, the power to be expended is no more than half that which corresponds to the same speed for an ordinary boat.

The water escapes in a thin and even sheet as soon as the tractive stress exceeds 2,000 kilogrammes; and the intensity and size of the eddies from the boat sensibly diminish in measure as the speed increases.

The interesting experiments made by Mr. Pictet seem, then to clearly establish the fact that the forms deduced by calculation are favorable to high speeds, and will permit of realizing, in the future, important saving in the power expended, and, consequently, in the fuel (much less of which will need to be carried), in order to perform a given passage within a given length of time. Thus is explained the great interest that attaches to Mr. Pictet's labors, and the desire that we have to soon be able to make known the results obtained with such great speeds, not when the boat is towed, but when its propulsion is effected through its own helix actuated by its own engine, which, up to the present, unfortunately, has through its defects been powerless to furnish the necessary amount of power for the purpose.—La Nature.

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INITIAL STABILITY INDICATOR FOR SHIPS.

For a vessel with a given displacement, the metacenter and center of gravity being known, it is easy to lay off in the form of a diagram its stability or power of righting for any given angle of heel. Such a diagram is shown in Fig. 3, in which the absciss are the angles of the heel, and the ordinates the various lengths of the levers, at the end of which the whole weight of the vessel is acting to right itself. The curve may be constructed in the following manner: Having found by calculation the position of the transverse metacenter, M, for a given displacement—Figs. 1 and 2—the metacentric height, G M, is then determined either by calculations, or more correctly by experiment, by varying the position of weights of known magnitude, or by the stability indicator itself. Suppose, now, the vessel to be listed over to various angles of heel—say 20 deg., 40 deg., 60 deg., and 80 deg.—the water lines will then be A C, D E, F K, and H J respectively, and the centers of buoyancy, which must be found by calculation, will be B1, B2, B3, and B4. If lines are drawn from these points at right angles to the water levels at the respective heels, the righting power of the vessel in each position is found by taking the perpendicular distances between these lines and the center of gravity, G. This method of construction is shown to an enlarged scale in Fig. 2, where G is the center of gravity, B1 Z1, B2 Z2, B3 Z3, and B4 Z4 the lines from centers of buoyancy to water levels; and G N, G O, and G P the distances showing the righting power at the angles of 20 deg., 40 deg., and 60 deg. respectively, and which to any convenient scale are set off as the ordinates in the stability curve shown in Fig 3.



Having obtained the curve, A, in this manner for a given metacentric height, we will suppose that on the next voyage, with the same displacement, it is found that, owing to some difference in stowage, the center of gravity is 6 in. higher than before. The ordinates of the curve will then be G N and G O—Fig.2—and the stability curve will be as at C—Fig. 3—showing that at about 47 deg. all righting power ceases. Similarly, if the center of gravity is lowered 6 in. on the same displacement, the curve, B, will be found, and in this manner comparative diagrams can be constructed giving at a glance the stability of a vessel for any given draught of water and metacentric height.



The object of Mr. Alexander Taylor's indicator is to measure and show by simple inspection the metacentric height under every condition of loading, and therefore to make known the stability of the vessel. It consists of a small reservoir, A, Fig. 4, placed at one side of the ship, in the cabin, or other convenient locality, communicating by a tube with the glass gauge, B, secured at the opposite side, the whole being half filled with glycerine, which is the fluid recommended by Mr. Wm. Denny, though water or any other liquid will answer the purpose. At one side of the gauge is the circular scale, C, capable of being revolved round its vertical axis, as well as adjusted up and down, so as to bring the zero pointer exactly to the top of the fluid when the vessel is without list. Round the top of the scale, at D, are engraved four different draughts, and under these are the metacentric heights. Test tanks of known capacity are placed at each side of the vessel, but in no way connected with the reservoir or gauge. The metacentric height is found as follows: The ship being freed from bilge water, the roller scale is turned round to bring to the front the mark corresponding with the mean draught of the vessel at the time, and the zero pointer is placed opposite the surface of the liquid in the gauge. One of the test tanks being filled with a known weight of water, the vessel is caused to list, and in consequence the liquid in the tube takes a new position corresponding with the degree of heel, the disturbance being greater according as the vessel has been more or less overbalanced. The scale having previously been properly graduated, the metacentric height for the draught and state of loading can be at once read off in inches, while as a check the water can be transferred from the one test tank to the other, and the metacentric height read off as before, but on the opposite side of the zero pointer. At the same time the angle of heel is shown on a second graduated scale, E. Having obtained the metacentric height, reference to a diagram will at once show the whole range of stability; and this being ascertained at each loading, the stowage of the cargo can be so adjusted as to avoid excessive stiffness in the one hand and dangerous tenderness on the other. It will thus be seen that Mr. Taylor's invention promises to be of great practical value both in the hands of the ship-builder and ship-owner, who have now an instrument placed before them, by the proper use of which all danger from unskillful loading can be entirely avoided.—The Engineer.



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SCRIVANOW'S CHLORIDE OF SILVER PILE.

Considerable attention has been attracted lately at Paris among those who are interested in electrical novelties to a chloride of silver pile invented by Mr. Scrivanow. The experiments to which it has been submitted are, in some respects, sufficiently extraordinary to cause us to make them known to our readers, along with the inventor's description of the apparatus.

Mr. Scrivanow's intention appears to be to apply this pile to the lighting of apartments, and even to the running of small motors, and, for the purpose of actuating sewing machines, he has already constructed a small model whose external dimensions are 160 x 100 x 90 millimeters.

"My invention," says the inventor, "is intended as an electric pile capable of regeneration. The annexed Fig. 1 shows a vertical arrangement of the apparatus, and Fig. 2 a horizontal one. In the latter, two elements are represented superposed.

"My pile consists of a prism of retort carbon (a) covered on every side with pure chloride of silver (b). The carbon thus prepared is immersed in a solution of hydrate of potassium (KHO) or of hydrate of sodium (NaHO), marking 1.30 to 1.45 by the Baum areometer, the solvent being water.

"In the vicinity of the carbon is arranged the plate to be attacked—a plate of zinc (c) of good quality. The surface of the electrodes, and their distance apart, depends upon the effects that it is desired to obtain, and is determined in accordance with the well known principles of electro-kinetics.

"The chemical reactions that take place in this couple are multiple. In contact with a sufficiently concentrated solution of hydrate of potassium or sodium, the chloride of silver, especially if it has been recently prepared, passes partially into the state of brown or black oxide, so that the carbon becomes covered, after remaining sufficiently long in the exciting liquid, with a mixture of chloride and oxide of silver. When the circuit is closed, the chloride becomes reduced to a spongy metallic state and adheres to the surface of the carbon. At the same time the zinc passes, in the alkaline solution, into a state of chloride and of soluble combination of zinc oxide and of alkali.

"To avoid all loss of silver I cover the carbon with asbestos paper, or with cloth of the same material, d. My piles are arranged in ebonite vessels, A, which are flat, as in Fig. 1, or round, as in Fig. 2.

"In Fig 1 there is seen, at e, gutta-percha separating the zinc from the carbon at the base.

"Under such conditions, we obtain a powerful couple that possesses an electro-motive power of 1.5 to 1.8 volts, according to the concentration of the exciting liquid. The internal resistance is extremely feeble. I have obtained with piles arranged like those shown in the figures nearly 0.06 ohm, the measurements having been taken from a newly charged pile.

"When the element is used up, and, notably, when all the chloride of silver is reduced, it is only necessary to plunge the carbon with its asbestos covering (after washing it in water) into a chloridizing bath, in order to bring back the metallic silver that invests the carbon to a state of chloride, and thus restore the pile to its primitive energy. After this the carbon is washed and put back into the exciting liquid.

"These reductions of the chloride of silver during the operation of the pile can be reproduced ad infinitum, since they are accompanied by no loss of metal. The alkaline liquid is sufficient in quantity for two successive charges of the couple.

"The chloridizing bath consists of 100 parts of acetic acid, 5 to 6 parts, by weight, of hydrochloric acid, and about 30 parts of water.



"Other acids may be employed equally as well. A bath composed of chlorochromate of potassium and nitric or sulphuric acid makes an excellent regenerator.

"To sum up, I claim as the distinctive characters of my pile:

"1. The use of the potassic or sodic alkaline liquid conjointly with chloride of silver, and the oxide of the same, that forms through the immersion of the carbon in a chloridizing bath.

"2. The use of retort or other carbon covered with the salt of silver above specified.

"3. The arrangement and construction of my pile as I have described."

In the experiments recently tried with Mr. Scrivanow's pile, a large sized battery was made use of, whose dimensions were 300 x 145 x 125 millimeters, and whose weight was from 5 to 6 kilogrammes. The results were: intensity, 1 ampere; electro-motive power, 25 volts, corresponding to an energy of 25 volt-amperes, or about 2.5 kilogrammeters per second. The pile was covered with a copper jacket whose upper parts supported two Swan lamps. Upon putting on the cover a contact was formed with the electrodes, and it was possible by means of a commutator key with three eccentrics to light or extinguish one of the lamps or both at once. A single element would have sufficed to keep one Swan lamp of feeble resistance lighted for 20 hours. Accepting the data given above and the 20 hours' uninterrupted duration of the pile's operation the power furnished by this large model is equal to 2.5 x 20 x 3,600 = 180,000 kilogrammeters.



In our opinion, Mr. Scrivanow's pile is not adapted for industrial use because of the expense of the silver and the frequent manipulations it requires, but it has the advantage, however, of possessing, along with its small size and little weight, a disposable energy of from 150,000 to 200,000 kilogrammeters utilizable at the will of the consumer and securing to him a certain number of applications, either for lighting or the production of power. It appears to us to be specially destined to become a rival to the bichromate of potash pile for actuating electric motors applied to the directing of balloons.—Revue Industrielle.

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ON THE LUMINOSITY OF FLAME.

The light emitted from burning gases which burn with bright flame is known to be a secondary phenomenon. It is the solid, or even liquid, constituents separated out by the high temperature of combustion, and rendered incandescent, that emit the light rays. Gases, on the other hand, which produce no glowing solid or liquid particles during combustion burn throughout with a weakly luminous flame of bluish or other color, according to the kind of gas. Now, it is common to say, merely, in explanation of this luminosity, that the gas highly heated in combustion is self-incandescent. This explanation, however, has not been experimentally confirmed. Dr Werner Siemens was, therefore, led recently to investigate whether highly-heated pure gases really emit light.

The temperature employed in such experiments should, to be decisive, be higher than those produced by luminous combustion. The author had recourse to the regenerative furnace used by his brother, Friedrich, in Dresden, in manufacture of hard glass. This stands in a separate room which at night can be made perfectly dark. The furnace has, in the middle of its longer sides, two opposite apertures, allowing free vision through. It can be easily heated to the melting temperature of steel, which is between 1,500 and 2,000 C. Before the furnace apertures were placed a series of smoke blackened screens with central openings, which enabled one to look through without receiving, on the eye, rays from the furnace walls. If, now, all air exchange was prevented in the furnace, and all light excluded from the room, it was found that not the least light came to the eye from the highly-heated air in the furnace. For success of the experiment, it was necessary to avoid any combustion in the furnace, and to wait until the furnace-air was as free from dust as possible. Any flame in the furnace (even when it did not reach into the line of sight), and the least quantity of dust in it, illuminated the field of vision.

As a result of these experiments, Dr. Siemens considers that the view hitherto held, that highly-heated gases are self-luminous, is not correct. In the furnace were the products of the previous combustion and atmospheric air: consequently oxygen, nitrogen, carbonic acid, and aqueous vapor. If even one of these gases was self-luminous, the field of vision must have been always illuminated. The weak light given by the flame of burning gases that separate out no solid nor liquid constituents cannot, therefore, be explained as a phenomenon of glow of the gaseous products.

It appealed to the author probable, that heated gases did not, either, emit heat rays; and he set himself to test this idea, experimenting, in company with Herr Frhlich, in Dresden. They first convinced themselves in this case that the light emission of pure heated gases sunk to zero, even when the field of vision was not always quite dark, and it was only possible to observe this a short time; but the repeatedly observed perfect darkness of the field of vision was demonstrative. On the other hand, experiments made with sensitive thermopiles, in order to settle the question of emission of heat-rays from highly-heated gases, failed.

Afterward, however, Dr. Siemens was convinced, by a quite simple experiment of a different kind, that his supposition was erroneous. An ordinary lamp, with circular wick, and short glass cylinder, was wholly screened with a board, and a thermopile was so placed that its axis lay somewhat higher than the edge of the board. As the room-walls had pretty much a uniform temperature, the deflection of the galvanometer was but slight, when the tube-axis of the thermopile was directed anywhere outside of the hot-air current rising from the flame. When, however, the axis was directed to this current, a deflection occurred, which was as great as that from the luminous flame itself. That the heat radiation from hot gases is but very small in comparison with that from equally hot solid bodies, was shown by the large deflection produced when a piece of fine wire was held in the hot-air current. On the other hand, however, it was far too considerable to admit of being attributed to dust particles suspended in the air current.

It must be conceded to be possible (the author says) that the light radiation of hot gases, as also the heat radiation, is only exceedingly weak, and therefore may escape observation. It is, therefore, much to be desired that the experiments should be repeated at still higher temperatures and with more exact instruments, in order to determine the limit of temperature at which heated gases undoubtedly become self-incandescent. The fact, however, that gases, at a temperature of more than 1,500 C, are not yet luminous, proves that the incandescence of the flame is not to be explained as a self-incandescence of the products of combustion. This is confirmed by the circumstance that, with rapid mixture of the burning gases, the flame becomes shorter because the combustion process goes on more quickly, and hotter because less cold air has access. Further, the flame also becomes shorter and hotter if the gases are strongly heated previous to combustion. As the rising products of combustion still retain for a time the temperature of the flame, the reverse must occur if the gases were self-luminous. The luminosity of the flame, however, ceases at a sharp line of demarkation, and evidently coincides with completion of the chemical action. The latter, itself, therefore, and not the heating of the combustion products, which is due to it, must be the cause of the luminosity. If we suppose that the gas-molecules are surrounded by an ether-envelope, then, in chemical combination of two or several such molecules, there must occur a changed position of the ether-envelopes. The motion of ether-particles thus caused may be represented by vibrations, which form the starting-point of light and heat-waves.

In quite a similar manner we may also, according to Dr. Siemens, represent the light-phenomenon occurring when an electric current is sent through gases, which always takes place when the maximum of polarization belonging to them is exceeded. As the passage of the current through the gas seems to be always connected with chemical action, the phenomenon of glow may be explained in the same way as in flame, by oscillating transposition of the ether envelopes, by which the passage of electricity is effected. In that case the light of flame may be called electric light by the same light as the light of the ozone tube or the Geissler tube, which is mainly to be distinguished from the former in that it contains a dielectric of an extremely small maximum of polarization. This correspondence in the causes of luminosity of flame, and of gases traversed by electric currents, is supported by the similarity of the flame-phenomena in strength and color of light.

[These researches were lately described by Dr. Werner Siemens to the Berlin Academy.]

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A QUICK WAY TO ASCERTAIN THE FOCUS OF A LENS.

It is well known that if the size of an object be ascertained, the distance of a lens from that object, and the size of the image depicted in a camera by that lens, a very simple calculation will give the focus of the lens. In compound lenses the matter is complicated by the relative foci of its constituents and their distance apart; but these items, in an ordinary photographic objective, would so slightly affect the result that for all practical purposes they may be ignored.

What we propose to do—what we have indeed done—is to make two of these terms constant in connection with a diagram, here given, so that a mere inspection may indicate, with its aid, the focus of a lens. All that is required in making use of it is to plant the camera perfectly upright, and place in front of it, at exactly fifteen feet from the center of the lens, a two foot rule, also perfectly upright and with its center the same height from the floor as the lens, and then, after focusing accurately with as large a diaphragm as will give sharpness, to note the size of the image and refer it to the diagram. The focus of the lens employed will be marked under the line corresponding to the size of the image of the rule on the ground glass.

As our object is to minimize time and trouble to the utmost, we may make a suggestion or two as to carrying out the measuring. It will be obvious that any object exactly two feet in length, rightly placed, will answer quite as well as a "two-foot," which we selected as being about as common a standard of length and as likely to be handy for use as any. The pattern in a wall paper, a mark in a brick wall, a studio background, or a couple of drawing pins pressed into a door, so long as two feet exactly are indicated, will answer equally well.

And, further, as to the actual mode of measuring the image on the ground glass (we may say that there is not the slightest need to take a negative), it will perhaps be found the readiest method to turn the glass the ground side outward, when two pencil marks may be made with complete accuracy to register the length of the image, which can then be compared with the diagram. Whatever plan is adopted, if the distance be measured exactly between lens and rule, the result will give the focus with exactitude sufficient for any practical purpose.—Br. Jour. of Photo.



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THE HISTORY OF THE PIANOFORTE.

[Footnote: A paper recently read before the Society of Arts, London.]

By A. J. HIPKINS.

As this paper is composed from a technical point of view, some elucidation of facts, forming the basis of it, is desirable before we proceed to the chronological statement of the subject. These facts are the strings, and their strain or tension; the sound-board, which is the resonance factor; and the bridge, connecting it with the strings. The strings, sound-board, and bridge are indispensable, and common to all stringed instruments. The special fact appertaining to keyboard instruments is the mechanical action interposed between the player and the instrument itself. The strings, owing to the slender surface they present to the air, are, however powerfully excited, scarcely audible. To make them sufficiently audible, their pulsations have to be communicated to a wider elastic surface, the sound-board, which, by accumulated energy and broader contact with the air, re-enforces the strings' feeble sound. The properties of a string set in periodic vibration are the best known of the phenomena appertaining to acoustics. The molecules composing the string are disturbed in the string's vibrating length by the means used to excite the sound, and run off into sections, the comparative length and number of which depend partly upon the place in the string the excitement starts from; partly upon the force and the form of force that is employed; and partly upon the length, thickness, weight, strain, and elasticity of the string, with some small allowance for gravitation. The vibrating sections are of wave-like contour; the nodes or points of apparent rest being really knots of the greatest pressure from crossing streams of molecules. Where the pressure slackens, the sections rise into loops, the curves of which show the points of least pressure. Now, if the string be struck upon a loop, less energy is communicated to the string, and the carrying power of the sound proportionately fails. If the string be struck upon a node, greater energy ensues, and the carrying power proportionately gains. By this we recognize the importance of the place of contact, or striking-place of the hammer against the string; and the necessity, in order to obtain good fundamental tone, which shall carry, of the note being started from a node.

If the hammer is hard, and impelled with force, the string breaks into shorter sections, and the discordant upper partials of the string, thus brought into prominence, make the tone harsh. If the hammer is soft, and the force employed is moderated, the harmonious partials of the longer sections strike the ear, and the tone is full and round. By the frequency of vibration, that is to say, the number of times a string runs through its complete changes one way and the other, say, for measurement, in a second of time, we determine the pitch, or relative acuteness of the tone as distinguished by the ear.

We know, with less exactness, that the sound-board follows similar laws. The formation of nodes is helped by the barring of the sound-board, a ribbing crosswise to the grain of the wood, which promotes the elasticity, and has been called the "soul" of stringed musical instruments. The sound-board itself is made of most carefully chosen pine; in Europe of the Abies excelsa, the spruce fir, which, when well grown, and of light, even grain, is the best of all woods for resonance. The pulsations of the strings are communicated to the sound-board by the bridge, a thick rail of close-grained beech, curved so as to determine their vibrating lengths, and attached to the sound-board by dowels. The bridge is doubly pinned, so as to cut off the vibration at the edge of the bearing the strings exert upon the bridge. The shock of each separate pulsation, in its complex form, is received by the bridge, and communicated to such undamped strings as may, by their lengths, be sensitive to them; thus producing the olian tone commonly known as sympathetic, an eminently attractive charm in the tone of a pianoforte.

We have here strings, bridge, and sound-board, or belly, as it is technically called, indispensable for the production of the tone, and indivisible in the general effect. The proportionate weight of stringing has to be met by a proportionate thickness and barring of the sound-board, and a proportionate thickness and elevation of the bridge.

The tension of the strings is met by a framing, which has become more rigid as the drawing power of the strings has been gradually increased. In the present concert grands of Messrs. Broadwood, that drawing power may be stated as starting from 150 lb. for each single string in the treble, and gradually increasing to about 300 lb. for each of the single strings in the bass. I will reserve for the historical description of my subject some notice of the different kinds of framing that have been introduced. It will suffice, at this stage, to say that it was at first of wood, and became, by degrees, of wood and iron; in the present day the iron very much preponderating. It will be at once evident that the object of the framing is to keep the ends of the strings apart. The near ends are wound round the wrest-pins, which are inserted in the wooden bed, called the wrest-plank, the strength and efficiency of which are most important for the tone and durability of the instrument. It is composed of layers of wainscot oak and beech, the direction of the grain being alternately longitudinal and lateral. Some makers cover the wrest-plank with a plate of brass; in Broadwood's grands, it is a plate of iron, into which, as well as the wood, the wrest-pins are screwed. The tuner's business is to regulate the tension, by turning the wrest-pins, in which he is chiefly guided by the beats which become audible from differing numbers of vibrations. The wrest-plank is bridged, and has its bearing like the soundboard; but the wrest-plank has no vibrations to transfer, and should, as far as possible, offer perfect insensibility to them.

I will close this introductory explanation with two remarks, made by the distinguished musician, mechanician, and inventor, Theobald Boehm, of Munich, whose inventions were not limited to the flute which bears his name, but include the initiation of an important change in the modern pianoforte, as made in America and Germany. Of priority of invention he says, in a letter to an English friend, "If it were desirable to analyze all the inventions which have been brought forward, we should find that in scarcely any instance were they the offspring of the brain of a single individual, but that all progress is gradual only; each worker follows in the track of his predecessor, and eventually, perhaps, advances a step beyond him." And concerning the relative value of inventions in musical instruments, it appears, from an essay of his which has been recently published, that he considers improvement in acoustical proportions the chief foundation of the higher or lower degree of perfection in all instruments, their mechanism being but of secondary value.

I will now proceed to recount briefly the history of the pianoforte from the earliest mention of that name, continuing it to our contemporary instruments, as far as they can be said to have entered into the historical domain. It has been my privilege to assist in proving that Bartolommeo Cristofori was, in the first years of the 18th century, the real inventor of the pianoforte, but with a wide knowledge and experience of how long it has taken to make any invention in keyed instruments practicable and successful, I cannot believe that Cristofori was the first to attempt to contrive one. I should rather accept his good and complete instrument as the sum of his own lifelong studies and experiments, added to those of generations before him, which have left no record for us as yet discovered.

The earliest mention of the name pianoforte (piano e forte), applied to a musical instrument, has been recently discovered by Count Valdrighi in documents preserved in the Estense Library, at Modena. It is dated A.D. 1598, and the reference is evidently to an instrument of the spinet or cembalo kind; but how the tone was produced there is no statement, no word to base an inference upon. The name has not been met with again between the Estense document and Scipione Maffei's well-known description, written in 1711, of Cristofori's "gravecembalo col piano e forte." My view of Cristofori's invention allows me to think that the Estense "piano e forte" may have been a hammer cembalo, a very imperfect one, of course. But I admit that the opposite view of forte and piano, contrived by registers of spinet-jacks, is equally tenable.

Bartolommeo Cristofori was a Paduan harpsichord maker, who was invited by Prince Ferdinand dei Medici to Florence, to take charge of the large collection of musical instruments the Prince possessed. At Florence he produced the invention of the pianoforte, in which he was assisted and encouraged by this high-minded, richly-cultivated, and very musical prince. Scipione Maffei tells us that in 1709 Cristofori had completed four of the new instruments, three of them being of the usual harpsichord form, and one of another form, which he leaves undescribed. It is interesting to suppose that Handel may have tried one or more of these four instruments during the stay he made at Florence in 1708. But it is not likely that he was at all impressed with the potentialities of the invention any more than John Sebastian Bach was in after years when he tried the pianofortes of Silbermann.

The sketch of Cristofori's action in Maffei's essay, from which I have had a working model accurately made, shows that in the first instruments the action was not complete, and it may not have been perfected when Prince Ferdinand died in 1713. But there are Cristofori grand pianos preserved at Florence, dated respectively 1720 and 1726, in which an improved construction of action is found, and of this I also exhibit a model. There is much difference between the two. In the second, Cristofori had obtained his escapement with an undivided key, reconciling his depth of touch, or keyfall, with that of the contemporary harpsichord, by driving the escapement lever through the key. He had contrived means for regulating the escapement distance, and had also invented the last essential of a good pianoforte action, the check. I will explain what is meant by escapement and check. When, by a key being put down, the hammer is impelled toward the strings, it is necessary for their sustained vibration that, after impact, the hammer should rebound or escape; or it would, as pianoforte makers say, "block," damping the strings at the moment they should sound.

A dulcimer player gains his elastic blow by the free movement of the wrist. To gain a similarly elastic blow mechanically in his first action, Cristofori cut a notch in the butt of his hammer from which the escapement lever, "linguetta mobile" as he called it—"hopper," as we call it—being centered at the base, moved forward, when the key was put down, to the extent of its radius, and after the delivery of the blow returned to its resting place by the pressure of a spring. The first action gave the blow with more direct force than the second, which had the notch upon what is called the underhammer, but was defective in the absence of any means to regulate the distance of the "go-off," or "escapement" from the string. In the second action, a small check before the hopper is intended to regulate it, but does so imperfectly. The pianoforte had to wait for fifty years for satisfactory regulation of the escapement.

In the first action, the hammer rests in a silken fork, dropping the whole distance of the rise of every blow. The check in the second action, the "paramartello," is next in importance to the escapement. It catches the back part of the hammer at different points of the radius, responding to the amount of force the player has used upon the key. So that in repeated blows, the rise of the hammer is modified, and the notch is nearer to the returning hopper in proportionate degree.

I have given the first place in description to Cristofori's actions, instead of to the "cembalo" or instrument to which they were applied, because piano and forte, from touch, became possible through them, and what else was accomplished by Cristofori was due, primarily, to the dynamic idea. He strengthened his harpsichord sound-board against a thicker stringing, renouncing the cherished sound-holes. Yet the sound-box notion clung to him, for he made openings in his sound-board rail for air to escape. He ran a string-block round the case, entirely independent of the sound-board, and his wrest-plank, which also became a separate structure, removed from the sound-board by the gap for the hammers, was now a stout oaken plank which, to gain an upward bearing for the strings, he inverted, driving his wrest-pins through in the manner of a harp, and turning them in like fashion to the harp. He had two strings to a note, but it did not occur to him to space them into pairs of unisons. He retained the equidistant harpsichord scale, and had, at first, under-dampers, later over-dampers, which fell between the unisons thus equally separated. Cristofori died in 1731. He had pupils, one of whom made, in 1730, the, "Rafael d'Urbino," the favorite instrument of the great singer Farinelli. The story of inventive Italian pianoforte making ends thus early, but to Italy the invention indisputably belongs.

The first to make pianofortes in Germany was the famous Freiberg organ-builder and clavichord maker, Gottfried Silbermann. He submitted two pianofortes to the judgment of John Sebastian Bach in 1726, which judgment was, however, unfavorable; the trebles being found too weak, and the touch too heavy. Silbermann, according to the account of Bach's pupil, Agricola, being much mortified, put them aside, resolving not to show them again unless he could improve them. We do not know what these instruments were, but it may be inferred that they were copies of Cristofori, or were made after the description of his invention by Maffei, which had already been translated from Italian into German, by Koenig, the court poet at Dresden, who was a personal friend of Silbermann. With the next anecdote, which narrates the purchase of all the pianofortes Silbermann had made, by Frederick the Great, we are upon surer ground. This well accredited occurrence took place in 1746. In the following year occurred Bach's celebrated visit to Potsdam, when he played upon one or more of these instruments. Burney saw and described one in 1772. I had this one, which was known to have remained in the new palace at Potsdam until the present time unaltered, examined, and, by a drawing of the action, found it was identical with Cristofori's. Not, however, being satisfied with one example, I resolved to go myself to Potsdam; and, being furnished with permission from H.R.H. the Crown Princess of Prussia, I was enabled in September, 1881, to set the question at rest of how many grand pianofortes by Gottfried Silbermann there were still in existence at Potsdam, and what they were like. At Berlin there are none, but at Potsdam, in the music-rooms of Frederick the Great, which are in the town palace, the new palace, and Sans Souci—left, it is understood, from the time of Frederick's death undisturbed—there are three of these Silbermann pianofortes. All three are with unimportant differences having nothing to do with structure, Cristofori instruments, wrest plank, sound-board, string-block, and action; the harpsichord scale of stringing being still retained. The work in them is undoubtedly good; the sound-boards have given in the trebles, as is usual with old instruments, from the strain; but I should say all three might be satisfactorily restored. Some other pianofortes seem to have been made in North Germany about this time, as our own poet Gray bought one in Hamburg in 1755, in the description of which we notice the desire to combine a hammer action with the harpsichord which so long exercised men's minds.

The Seven Years' War put an end to pianoforte making on the lines Silbermann had adopted in Saxony. A fresh start had to be made a few years later, and it took place contemporaneously in South Germany and England. The results have been so important that the grand pianofortes of the Augsburg Stein and the London Backers may be regarded, practically, as reinventions of the instrument. The decade 1770-80 marks the emancipation of the pianoforte from the harpsichord, of which before it had only been deemed a variety. Compositions appear written expressly for it, and a man of genius, Muzio Clementi, who subsequently became the head of the pianoforte business now conducted by Messrs. Collard, came forward to indicate the special character of the instrument, and found an independent technique for it.

A few years before, the familiar domestic square piano had been invented. I do not think clavichords could have been altered to square pianos, as they were wanting in sufficient depth of case; but that the suggestion was from the clavichord is certain, the same kind of case and key-board being used. German authorities attribute the invention to an organ builder, Friederici of Gera, and give the date about 1758 or 1760. I have advertised in public papers, and have had personal inquiry made for one of Friederici's "Fort Biens," as he is said to have called his instrument. I have only succeeded in learning this much—that Friederici is considered to have been of later date than has been asserted in the text-books. Until more conclusive information can be obtained, I must be permitted to regard a London maker, but a German by birth, Johannes Zumpe, as the inventor of the instrument. It is certain that he introduced that model of square piano which speedily became the fashion, and was chosen for general adoption everywhere. Zumpe began to make his instruments about 1765. His little square, at first of nearly five octaves, with the "old man's head" to raise the hammer, and "mopstick" damper, was in great vogue, with but little alteration, for forty years; and that in spite of the manifest improvements of John Broadwood's wrest-plank and John Geib's "grasshopper." After the beginning of this century, the square piano became much enlarged and improved by Collard and Broadwood, in London, and by Petzold, in Paris. It was overdone in the attempt to gain undue power for it, and, about twenty years ago, sank in the competition, with the later cottage pianoforte, which was always being improved.

To return to the grand pianoforte. The origin of the Viennese grand is rightly accredited to Stein, the organ builder, of Augsburg. I will call it the German grand, for I find it was as early made in Berlin as Vienna. According to Mozart's correspondence, Stein had made some grand pianos in 1777, with a special escapement, which did not "block" like the pianos he had played upon before. When I wrote the article "Pianoforte" in Dr. Grove's "Dictionary," no Stein instrument was forthcoming, but the result of the inquiries I had instituted at that time ultimately brought one forward, which has been secured by the curator of the Brussels Museum, M. Victor Mahillon. This instrument, with Stein's action and two unison scale, is dated 1780. Mozart's grand piano, preserved at Salzburg, made by Walther, is a nearly contemporary copy of Stein, and so also are the grands by Huhn, of Berlin, which I took notes of at Berlin and Potsdam; the latest of these is dated 1790.

An advance shown by these instruments of Stein and Stein's followers is in the spacing of the unisons; the Huhn grands having two strings to a note in the lower part of the scale, and three in the upper. The Cristofori Silbermann inverted wrest-plank has reverted to the usual form; the tuning pins and downward bearing being the same as in the harpsichord. There are no steel arches as yet between the wrest-plank and the belly-rail in these German instruments. As to Stein's escapement, his hopper was fixed behind the key; the axis of the hammer rising on a principle which I think is older than Stein, but have not been able to trace to its source, and the position of his hammer is reversed. Stein's light and facile movement with shallow key-fall, resembling Cristofori's in bearing little weight, was gratefully accepted by the German clavichord players, and, reacting, became one of the determining agents of the piano music and style of playing of the Vienna school. Thus arose a fluent execution of a rich figuration and brilliant passage playing, with but little inclination to sonorousness of effect, lasting from the time of Mozart's immediate followers to that of Henri Herz; a period of half a century. Knee-pedals, as we translate "geuouillres," were probably in vogue before Stein, and were levers pressed with the knees, to raise the dampers, and leave the pianoforte undamped, a register approved of by Carl Philip Emmanuel Bach, who regarded the undamped pianoforte as the more agreeable for improvising.. He appears, however, to have known but little of the capabilities of the instrument, which seemed to him coarse and inexpressive beside his favorite clavichord. Stein appears to have made use of the "una corda" shift. Probably by knee-pedals, subsequently by foot-pedals, the following effects were added to the Stein pianos.