Chapter M: STRAVOS ZELLIS, of Alexandria in Egypt, recommends the following

process for marking or lettering on the sensitized paper such names as we wish to give the prints. He takes a piece of thin white paper and traces upon it the words which he wishes to have at the bottom of his negative, and oils it on both sides; having removed the excess of oil by rubbing it between two sheets of bibulous paper, he coats it with varnish on both sides and allows it to dry. On the other hand, he removes from the bottom of the negative a portion of the gelatine, equal to the size of the paper, and substitutes for it the paper, which he sticks by means of a solution of gum arabic and water. He removes then the air bubbles, which would prevent complete adherence, and this being done, waits for his work to dry. If, when printing on the sensitized paper, it is found that the letters do not show very white, the defective portions should be retouched on the back of the oiled paper. To write his name Mr. Zellis makes use of a mixture of gum arabic, lampblack, and water. This process is simple, cheap, and gives excellent results.--_Annals Photographique._

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At the meeting of the Photographic Society of Berlin, President Stolze exhibited the sketch of the Daguerre monument to be erected in Washington city, at the cost of six thousand dollars.

Dr. Julius Stinde declared never to have seen anything more disgusting (schauerlicheres) than this unhappy head of Daguerre, crushed under the weight of a large ball, and attributes the depravity of our taste to the high duty on articles of fine arts. He says that such monstrosities show that we Americans are yet in point of art barbarians of the purest water. Mr. E. Himly, as well as Dr. Stolze, takes our part, and shows that the American photographic journals have unanimously condemned and ridiculed Mr. H. McMichel’s scheme, and exonerate us as a body. Bravo!--_Photographische Nachrichten._

DAGUERRE.

On the twelfth of August, in front of the Smithsonian Institute, in Washington, dedicated to manifold arts and sciences, will be erected a lasting memorial to Daguerre, the author that we all know fixed the visible image on a given surface, which is photography, with all its varieties and names, and they are numerous.

Why should we Americans put up such a memorial? The inscription on the granite below the bronze portrait tells the story:

“To commemorate the first half century in photography, 1839–1889. Photography, the electric telegraph, and the steam engine are the three great discoveries of the age. No five centuries in human progress can show such strides as these. Erected by THE PHOTOGRAPHERS’ ASSOCIATION OF AMERICA, August, 1890.”

The monument, now almost complete, its bronze features being of a high order of art, will stand sixteen feet high, and will be the only international monument in the city of Washington, where Smithson himself dedicated his fortune for the advancement of science in the western world.

In connection with this celebration we present to our readers a portrait of Daguerre. Strange to say, there are but few authentic portraits of Daguerre in existence. In our search for such a portrait we discovered the one here reproduced; it was engraved by Orr from a photograph by Dr. Meade, of New York, for the International Magazine, of that city, and used to illustrate the obituary of the eminent Frenchman, September 1, 1851. As everything relating to Daguerre cannot but prove of interest at the present time, we republish the interesting article in full as it appeared at the time:

Lewis Jacques Mande Daguerre, whose name is forever associated with the photographic process, of which he was the discoverer, died on the tenth of July, in Paris, in the sixty-second year of his age. He was a man of extreme modesty and great personal worth, and was devoted to art.

He was favorably known to the world before the announcement of his discovery of the Daguerreotype. His attempts to improve panoramic painting, and the production of dioramic effects, were crowned with the most eminent success. Among his pictures, which attracted much attention at the time of their exhibition, were, “The Midnight Mass,” “Land-slip in the Valley of Goldan,” “The Temple of Solomon,” and “The Cathedral of Sainte Marie de Montreal.”

In these the alternate effects of night and day, and storm and sunshine, were beautifully produced. To these effects of light were added others, from the decomposition of form, by means of which, for example in “The Midnight Mass,” figures appeared where the spectators had just beheld seats, altars, etc.; and again, as in “The Valley of Goldan,” in which rocks tumbling from the mountains replaced the prospect of a smiling valley.

The methods adopted in these pictures were published at the same time with the process of Daguerreotype, by order of the French Government, who awarded an annual pension of ten thousand francs to Daguerre and M. Niepce, Jr., whose father had contributed towards the discovery of the Daguerreotype. Daguerre was led to experiments on chemical changes by solar radiations, with the hope of being able to apply the phenomena to the production of effects in his dioramic paintings. As the question of the part taken by him in the process to which he has given his name has been discussed sometimes to his advantage, it appears important that his position should be correctly determined. In 1802, Wedgwood, of Eturia, the celebrated potter, made the first recorded experiments in photography; and these, with some additional ones by Sir Humphrey Davy, were published in the journals of the royal institution. In 1814, Mr. Joseph Nicephore Niepce was engaged in experiments to determine the possibility of fixing the images obtained in the camera obscura; but there does not appear any evidence of publication of any kind previously in 1827, when Niepce was in England. He there wrote several letters to Mr. Bauer, the microscopic observer, which are preserved and printed in Hunt’s “Researches on Light.”

He also sent specimens of results obtained to the Royal Society, and furnished some to the cabinets of the curious, a few of which are yet in existence. These were pictures on metallic plates covered with film of resin.

In 1824 Daguerre commenced his researches, starting at that point at which Wedgwood left the process. He soon abandoned the employment of the nitrate and chloride of silver, and proceeded with his inquiry, using plates of metal and glass to receive his sensitive coating. In 1829 Mr. Vincent Chevalier brought Niepce and Daguerre together, when they entered into partnership to prosecute the subject in common. For a long time they appear to have used the resinous surface only, when the contrast between the resin and the metal plates not being sufficiently great to give a good picture, endeavors were made to blacken that part of the plate from which the resin was removed in the process of heliography (sun drawing), as it was most happily called. Amongst other materials, iodine was employed; and Daguerre certainly was the first to notice the property possessed by the iodine coating of changing under the influence of the sun’s rays. The following letter from Niepce to Daguerre is on this subject:

“81, LOUP DE VARVENNES, June 23, 1831.

“Sir and Dear Partner:--I had long expected to hear from you with
too much impatience not to receive and read with the greatest
pleasure your letters of the tenth and twenty-first of last May.

“I shall confine myself in this reply to yours of the twenty-first,
because, having been engaged ever since it reached me in your
experiments on iodine, I hasten to communicate to you the results
which I have obtained. I had given my attention to similar
researches previous to our connection, but without hope of success,
from the impossibility, or nearly so, in my opinion, of fixing in
any durable manner the image received on iodine, even supposing the
difficulty surmounted of replacing the lights and shadows in their
natural order. My results in this respect have been entirely similar
to those which the oxide of silver gave me; and promptitude of
operation was the sole advantage which these substances appeared to
offer. Nevertheless, last year, after you left this, I subjected
iodine to new trials, but by a different mode of application. I
informed you of the results, and your answer, not at all
encouraging, decided me to carry these experiments no farther. It
appears that you have since viewed the question under a less
desperate aspect, and I do not hesitate to reply to the appeal which
you have made.

“J. N. NIEPCE.”

From this and other letters it is evident that Niepce had used iodine, and abandoned it on account of the difficulty of reversing the lights and shadows. Daguerre employed it also, as it appears, with far more promise of success than any obtained by M. Niepce. On the fifth of July, 1833, Niepce died; in 1837 Daguerre and Isodore Niepce, the son and heir of Nicephore Neipce, entered into a definite agreement, and in a letter written on the first of November, 1837, to Daguerre, Isodore Niepce says, “What a difference, also, between the method which you employ and the one by which I toil on! While I require almost a whole day to make one design, you ask only four minutes! What an enormous advantage! It is so great, indeed, that no person knowing both methods would employ the old one.” From this time it is established that although both Niepce and Daguerre used iodine, the latter alone employed it with any degree of success, and the discovery of the use of mercurial vapor to produce the positive image clearly belongs to Daguerre. In January, 1839, Daguerreotype pictures were first shown to the scientific and artistic public of Paris.

The sensation they created was great, and the highest hopes of its utility were entertained. On the 15th of June M. Duchatel, Minister of the Interior, presented a bill to the Chamber of Deputies relative to the purchase of the process of M. Daguerre for fixing the images of the camera. A commission appointed by the Chamber, consisting of Arago, Etienne, Carl, Vatout, de Beaumont, Toursover, Delessert (Francois), Combarel de Leyral, and Vitet, made their report in July, and a special commission was appointed by the Chamber of Peers, composed of the following peers: Barons Athalin Besson, Gay Lussac, the Marquis de Laplace, Vicomte Simeon, Baron Thenard, and the Comte de Noe, who reported favorably on the 30th of July, 1839, and recommended unanimously that the “bill be adopted simply, and without alteration.” On the 19th of August the secret was for the first time publicly announced in the institution by M. Arago, the English patent having been completed a few days before, in open defiance and contradiction of the statement of M. Duchatel to the Chamber of Deputies, who used these words:

“Unfortunately for the authors of this beautiful discovery, it is impossible for them to bring their labor into the market, and thus indemnify themselves for the sacrifices incurred by so many attempts so long fruitless. This invention does not admit of being secured by patent.”

In conclusion, the Minister of the Interior said: “You will concur in a sentiment which has already awakened universal sympathy. You will never suffer us to leave to foreign nations the glory of endowing the world of science and of art with one of the most wonderful discoveries that honor our native land.” Daguerre never did much towards the improvement of his process. The high degree of sensibility which has been attained has been due to the experiments of others.

Daguerre is said to have been always averse to sitting for his own picture, and there are but few photographs of him in existence. The one from which our engraving is copied was taken by Mr. Meade of this city, and first appeared in the _Daguerrean Journal_, a monthly periodical conducted by S. D. Humphrey and L. L. Hill, who were distinguished for their improvements upon Daguerre’s process.

GELATINOGRAPHY.

A very rapid process to make newspaper illustrations, called gelatinography, is described in the following:

A black glass plate or a tin plate coated with black varnish, as used by sign-painters, is covered with plaster of Paris (gypsum) to a thickness of four-ply cardboard. The plaster of Paris must be of the best quality and reduced to a very fine powder. Add thereto some alum and some sulphate of barium, and in order to prevent the coating from being too brittle, add also a trifle of glycerine or of a gelatine solution.

This mixture must have the consistency of a thin pulp when applied to the glass or tin with a soft camel’s-hair brush.

When dry, the artist may engrave into this coat of plaster of Paris, by means of a lithographic engraving needle, any design or picture with the greatest ease; the plate or glass is thereby laid bare, and design or picture appears black through the plaster of Paris coating. Mistakes or errors are easily remedied by filling in the plaster of Paris preparation.

With the regular printers’ roller composition a stereotype is now made of the picture or design on the glass or plate, in the usual way; some bichromate of ammonia solution should be added to the roller composition, to make the stereotype hard enough for the type press, and it will be as durable as any electrotype, and answer the same purpose.--_Am. Lith. and Printer._

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STEREOSCOPIC PHOTOGRAPHY.--Of late, there is quite a revival in this branch of our art-science, several English and many foreign amateurs having been working with twin lenses during the last and present seasons. The Belgian _Bulletin_ has an article on the subject, and the last technical meeting of the Photographic Society was devoted to it. Although Wheatstone announced the instrument in 1838, it was not until photography had come to his aid by furnishing satisfactory diagrams, and Brewster had popularized the matter by the invention of the lenticular stereoscope, that much progress was made; then Wheatstone gave his Bakerian lecture on January 15th, 1852, to put the finishing touch to this important branch of scientific work. The earlier attempts failed by reason of employing too wide an angle.

ECLIPSE PHOTOGRAPHY.

Probably in no department of science, certainly in no branch of astronomical science, has photography been of such use as in the study of solar eclipses. It is only when the sun is obscured by the moon that we are able to see and properly photograph the corona or luminous atmosphere around the sun. This solar corona, as has been said by Young, “is visible only about eight days in the century in the aggregate, and then only over narrow strips of the earth’s surface, and but from one to five minutes at a time by any one observer.” Very little of the eight days, however, can be utilized; indeed, as has been pointed out by Miss Clerke in her admirable _History of Astronomy During the Nineteenth Century_, the corona has only been observed by scientific men during forty-five minutes in as many years. Opportunities of observing an eclipse occur therefore at such comparatively long intervals, the phenomena to be observed are so varied and extensive, and the time during which the observations must be made is so very limited, that any permanent records of the phenomena, such as photography enables us to obtain, cannot fail to be of the greatest value. The most careful drawings of the same eclipse by different observers at the same station are so very dissimilar that it is generally unsafe to base any conclusion on them; whereas in photographs we have truthful records of the actual phenomena without personal equation of any kind, and with the additional advantage that there is more detail in the photograph than it is possible to insert in any drawing made during an eclipse, or even at leisure after the three or four minutes’ observation of such an indefinite and irregular object as the corona. The history of the increase of our knowledge of the corona is practically the history of the improvement of our photographic methods of attacking the phenomena of an eclipse.

The first occasion on which photography was used at an eclipse of the sun was on July 8, 1842, when Professor Majocchi, at Milan, attempted to obtain Daguerreotype pictures of the corona. His account of the attempt informs us that “a few minutes before and after totality an iodised plate was exposed in a camera to the light of the thin crescent, and a distinct image was obtained; but another plate exposed to the light of the corona for two minutes during totality did not show the slightest trace of photographic action. No photographic alteration was caused by the light of the corona condensed by a lens for two minutes, during totality, on a sheet of paper prepared with bromide of silver.” No details are given of the apertures of the lenses employed, or of their focal lengths. At the outset, therefore, astronomers were met with failure, but the failure at Milan did not deter Dr. A. H. Busch and Herr Berkowski from a similar attempt at Konigsberg on July 28, 1851. The telescope used on this occasion had an aperture of 2.4 inches, and a focal length of 30 inches. Commencing immediately after the beginning of totality, a plate was exposed for 84 seconds in the focus of the telescope, and on development an image of the corona was obtained. A second plate exposed for from 40 to 45 seconds was fogged by the sudden breaking out of the sunlight. The picture thus obtained--the first photograph of the corona and prominences--is known as the Konigsberg Daguerreotype, and is still preserved at the Strasburg Observatory. It was lent by Professor Winnecke for the exhibition of scientific instruments at South Kensington in 1876. On it the prominences, and the lower portion of the corona extending about one-fourth of a solar diameter from the moon’s limb, are distinctly shown, the encroaching of the prominences on the dark disc of the moon, owing to irradiation, being particularly evident.

Daguerreotype was again used for the annual eclipse of May 26, 1854, by Mr. Campbell and Professor Loomis at New York; by Dr. Bartlett and Victor Prevost, who obtained nineteen photographs, at West Point; and by Professor Stephen Alexander and Mr. E. H. Old at Ogdensburg.

Liais in 1858 obtained photographs of the partial phases, using wet plates. On one of these the moon can be seen projected on the corona before totality. With the introduction of the collodion process more sensitive plates were obtained, and a great advance was anticipated. At the total eclipse of 1860, July 18, Mr. Warren de la Rue, at Rivabellosa, in Spain, used wet plates. His instrument was one specially devised by himself for photographing the sun’s disc for sun-spots, and is known as the Kew heliograph. It is an ordinary equatorial mounting with driving clock, carrying a photographic object-glass, 3.4 inches clear aperture, and 50 inches focal length. The primary image is .466 of an inch in diameter, but before the image falls on the plate it is enlarged by an ordinary Huyghenian eyepiece to 3.8 inches diameter. The exposing apparatus for the ordinary sun photographs is an instantaneous shutter; this, of course, had to be abandoned for the eclipse photographs. Two plates were exposed during totality, the exposure being 60 seconds in each case, but only slight traces of the corona were obtained. At the same eclipse Father Secchi and Professor Monserat, working at Desierto de las Palmas, obtained good photographs of the corona, using an object-glass of .15 metre diameter, and 2.5 metres focus, the primary image being 23 millimetres in diameter. The plates were placed in the primary focus and according to Secchi, “all the phases of the phenomena are represented on the photographs.” The original negatives obtained at Desierto de las Palmas of this eclipse have unfortunately been lost.

The next attempt at photographing the corona was on August 18, 1868, this being remarkable as the first attempt to use a reflector for the purpose. Colonel Tennant and Sergeant Phillips at Guntoor used a 9–inch silver-on-glass mirror, by With, of 6 feet focal length, mounted equatorially by Browning on the Newtonian plan.

Unfortunately the weather was unfavorable, but plates were exposed through light clouds, the longest exposure being 10 seconds. The photographs obtained show the prominences sharply defined, but only slight traces of corona are visible. Mr. Sutton, at Mautawali Kiki, and Drs. G. Fritsch, H. Vogel, and W. Zener, at Aden, were, from atmospheric and other causes, unsuccessful with refractors.

At the eclipse of August 7, 1869, many attempts were made to photograph the corona. In all cases where the image was enlarged before it fell on the plate, slight traces of the corona were obtained; while Professor Winlock and Mr. J. A. Whipple, at Shelbyville, with a 5½-inch lens of 7½ feet focal length, obtained seven pictures taken in the primary focus, one with 40 seconds’ exposure, showing more detail than had previously been photographed.

At this eclipse, Messrs. Hoover photographed the corona with a lens of 12 inches focus, and Professor Stephen Alexander also obtained photographs at Ottumwa some of which give good ideas of the coronal structure.

At the 1870 eclipse, December 22, a 4–inch Dallmeyer lens (rapid rectilinear), stopped down to three inches aperture, and with a focal length of thirty inches, was used by Mr. Brothers at Syracuse. Wet plates were used, and the photographs were taken through light clouds, the best of the pictures having had eight seconds’ exposure. Details in the corona are very well shown in these photographs. In discussing his results, Mr. Brothers says, “The photographs taken ... prove that the light of the corona is very actinic, and that several photographs of this beautiful phenomenon can be taken during the time of totality.” He further adds, “That it is impossible to obtain satisfactory photographs of the corona either with reflecting or refracting telescopes as ordinarily used is, I think, now conclusively proved.”

Professor Winlock, at Jerez, during the same eclipse, obtained two good photographs with ordinary telescopes; while Lord Lindsay, at Maria Louis Observatory, with a 12–inch mirror of 6 feet focus, obtained plates so much fogged as to be useless.

On December 21, 1871, splendid photographs were obtained at Baikul by Mr. Davis (Lord Lindsay’s observer), and by Colonel Tennant, J. B. Hennessey, Esq., and Captain Waterhouse, at Dodabetta. In each case Dallmeyer 4–inch rapid rectilinear lenses of thirty-three inches focus were used, the exposures varying from five to forty seconds. Herr Dietsch, in Java, also obtained two good photographs with a “lens of short focus,” with exposures of half and one-third second. Captain Hogg, at Jaffna, also got fair results with cameras 16 inches and 23 inches long. At the eclipse of April 6, 1875, Dr. Schuster, in Siam, obtained good photographs, although small, with an ordinary camera.

The eclipse of 1878 marked another departure in photography. Dr. Draper used wet plates, and got much detail in 165 seconds. Mr. Ranyard used Mawson & Swan’s extra sensitive dry plates, with a 13–inch lens of 6 feet 2 inches focus, and obtained photographs extending 6′ (one-fifth of a sun’s diameter) from the limb with exposures of one and three seconds. Professor Harkness, the director of the American operations, arranged two cameras, with 6–inch Dallmeyer lenses of 37.9–inch focus, and Mr. J. A. Rogers and Mr. Clark with these, using specially prepared dry plates made by Mr. Rogers, obtained two good series of photographs. In the report on the eclipse operations published from the United States Naval Observatory, Mr. J. A. Rogers not only discusses the value of photographs as compared with drawings, but enters fully into all the details of eclipse photography, concluding by strongly advocating the adoption of dry plates. Mr. O. L. Peers during this eclipse obtained a wet plate photograph showing greater extension of the corona than any of the dry plate ones, but there seems some doubt about the apparatus he used. He used either a 2⅛-inch or 3⅛-inch Voigtlander portrait lens, and exposed either for twelve or for twenty-three seconds. Mr. Peers says he used a 2⅛-inch lens, and twelve seconds’ exposure, while Voigtlander declares he makes only 3⅛-inch lenses of the focus 1:8 Mr. Peers used, and on examination of the photograph it is found that the trail of the moon on the plate indicates an exposure of twenty-three seconds. After the 1878 eclipse dry plates were universally adopted by eclipse observers.

The photographic arrangements of the expedition to Sohag, in Egypt, for the eclipse on May 17, 1882, were made by Captain Abney, the chief objects of the expedition being to photograph the spectra of the corona and prominences. Arrangements were also made by Captain Abney for corona photographs with a 4–inch lens of sixty inches focus belonging to him. The spectrum photographs taken show as many as thirty lines in the prominences, while the photographs of the corona obtained by Dr. Schuster with exposures of from three to thirty-two seconds show great extension of the corona with the most exquisite detail. These plates are also remarkable for the discovery of a comet in the photographs, although the comet was not seen by observers. Captain Abney and Mr. J. Norman Lockyer were responsible for the methods of photographic attack adopted by the English observers, Messrs. Lawrence and Woods, at the Caroline Islands, on May 6, 1883. The spectroscopic results and the corona photographs taken with the 4–inch lens of Captain Abney, previously used in 1882, were most successful. Janssen on this occasion used two objectives, one 6–inch and one 8–inch diameter, and using long exposures, photographed the corona extending two diameters from the sun, this being much further than it could be traced with a telescope.

Photography was again used on September 8, 1885, at the total eclipse in New Zealand.

At the eclipse of August, 1886, visible at Granada, Captain Darwin used a chronograph as devised by Dr. Huggins, consisting of a mirror inclined in a tube in such a manner as to enable photographs to be taken in the primary focus without the intervention of a flat. Good results were obtained. Dr. Schuster and Mr. Maunder used 4–inch lenses of 60–inch focus, and obtained good results. Their spectrum photographs were also successful. Professor Pickering, of Harvard, used a heliostat and a photo-heliograph of 38 feet focus, supported horizontally, but no results were obtained with this apparatus, although he was partially successful with his other instruments.

Very few photographs were obtained of the eclipse of August 19, 1887, in Russia, owing to the unfavorable weather. The English observers intended to use similar instruments to those employed in 1886, but the weather did not permit.

The eclipse of January 1, 1889, was very successfully photographed by the American observers, the largest aperture used being thirteen inches. On some of the plates used during this eclipse the standard intensity scale recommended by Captain Abney several years ago was fixed, and for the first time definite conclusions as to the brightness of the corona were obtained.

The expedition sent out by the Royal Astronomical Society for the eclipse of December 22, 1889, were each fitted with a 4–inch photographic lens, belonging to Captain Abney, mounted on the usual equatorial plan, and intended to continue the series so well begun by Dr. Schuster in 1882, and also with a 20–inch mirror of 45 inches focus, specially constructed and mounted for eclipse work, and designed to photograph the outer portions of the corona too faint for ordinary instruments. The plates for use with the 4–inch lenses were specially prepared by Captain Abney, and on each of them he had placed a scale of standard intensity squares for measuring the brightness of the corona. Small squares on each of the plates were exposed to a standard light for various times; these squares were then covered with a strip of black paper, and the plates taken out to the Eclipse Station and exposed on the corona. When the plates were developed the image of the corona and the squares were, of course, developed to the same extent, the squares thus serving as standards for absolutely measuring the photographic intensity of the light of the corona. The density of the deposit in any part of the picture of the corona can be compared with the density of the most similar of the squares on the same plate by Captain Abney’s photometer, and as this photometer depends upon the method of limiting apertures, it gives absolute readings.

The African expedition was entirely unsuccessful, owing to clouds, but the expedition to Salut Isles, under charge of the late Father Perry, obtained successful photographs, which are at present under examination. From them Captain Abney will be able to measure the absolute photographic intensity of the light of the corona.

An American expedition was sent to Cayenne with instruments used on January 1, 1889, and obtained successful photographs, while an American expedition to Southwest Africa was unsuccessful, for the reason already given. This expedition, under the direction of Professor David P. Todd, was located at Cape Ledo, about half a mile from the English Eclipse Station.

Several new departures in eclipse photography were introduced. Chief amongst these was the remarkable apparatus by means of which no less than twenty-three objectives and two mirrors were accurately pointed at the sun and caused to follow it by one large clock. A large duplex polar axis (the old English form as used for the 12.5 inch reflector at Greenwich) was mounted on solidly constructed stone piers and very carefully adjusted. This axis is constructed of 6–in. wrought-iron tubing, the total weight being about 2000 lbs. In it the cameras were fixed by set screws, the optic axis of the instruments being adjusted parallel to each other, and at an angle equal to the south polar distance of the sun at the time of totality. The carefully regulated and very powerful clockwork attached to the instrument caused the polar axis to rotate, and thus the whole battery of instruments followed the sun. Each lens was fitted with a pneumatic shutter regulated to give the required exposure in each case. The cameras themselves were enclosed in a dark-room, the lenses only being exposed to the sun, so that dark slides were not required, the plates being held on open rotating frames, these frames being rotated at the proper time by pneumatic arrangements. When the cameras were once pointed, and the clock driving properly, all the operations of exposure and changing of plates were performed without personal superintendence by means of the pneumatic apparatus, and a chronograph attached to the valve system of this apparatus recorded the exact time at which each exposure was begun and ended.

It is to be regretted that this ingenious and elaborate apparatus did not have a satisfactory trial, owing to the dense clouds; but Professor Todd assures us that he was thoroughly satisfied with the success of the pneumatic movements during the three minutes ten seconds he brought it into operation at the time of totality.

It is not improbable that (in spite of the great strength and weight of the axis and the solidity of the supporting piers) with this plan of fixing a large number of cameras and spectroscope on one polar axis, the constant opening and shutting of shutters, and the changing of the plates, may produce so much shake that none of the long exposure photographs will be satisfactory. This, of course, can only be ascertained by the use of the instrument on the corona, and several years must elapse before the trial can be made.

Another unusual instrument was a photo-heliograph of five inches aperture and forty feet focus, mounted on a combination of the equatorial stand and tripod.

The long tube was made of iron, coiled spirally and strongly riveted, the necessary rigidity being attained by strong wires extending from end to end, and tightly stretched by a disc in the middle of the tube. Close to one end of the tube the polar axis was attached by a universal joint; the other end of the tube being supported by two rods, one on the east and one on the west side, these rods being also attached by universal joints. By means of these rods the proper inclination was given to the tube. The east rod was the declination rod, and was capable of sliding along the polar axis. The west rod was for giving motion in right ascension, being terminated at the free end in the form of a piston of a sand clock fixed in an inclined position. The rate at which the sand escaped from the cylinder could be accurately regulated, so that the rate of descent of the piston was completely under control, and was, of course, such as would cause the instrument to follow the sun.

This instrument was erected at Cape Ledo, close to a hill of such inclination that the sun could be followed during the whole of the eclipse, while the long tube could be manipulated with greater advantage than would have been possible if the instrument had been erected on level ground. The hot air rising from the heated hill probably affected the definition in the photographs, but under the circumstances that could scarcely be avoided.

This form of mounting certainly solved the question of the possibility of using long-focus lenses mounted as direct photo-heliographs, but the apparatus is certainly unwieldly, and was only got into the fit state that it was on the eclipse day by the very great care and patience of Professor Bigelow. As it was intended principally to photograph the partial phases of the eclipse with this instrument, instantaneous exposures were arranged for, but Professor Bigelow succeeded so well in the adjustment of the instrument and the regulation of the sand clock, that he would have tried to obtain photographs of the lower corona with it had the weather permitted.

The photographic apparatus on this instrument has a very ingeniously constructed revolving plate holder, carrying round plates of twenty-two inches diameter. The exposing apparatus and the apparatus for rotating the plate between the exposures were moved by pneumatic arrangements, exposures being made at intervals of six seconds, the exact time of each being recorded on a chronograph. As no dark slides were used, it was necessary to enclose the whole of the photographic apparatus in a dark-room. One hundred and ten exposures were made with this telescope during the partial phases of the eclipse, all the photographs taken having to be obtained through clouds.

In several expeditions previous to this, where more than one kind of observation has been required, two or more objectives have been mounted on the same stand and driven by the same clock; but this plan is always open to the objection that any accidental disturbance in the manipulation of one of the pieces of apparatus will most probably spoil the results for both. With the American plan of many objectives on one heavy axis, and a pneumatic apparatus to manage all the actual operations of exposures and changing of plates, this objection of possible accidental disturbance is to some extent overcome; but the shake of the many operations taking place on the one axis introduces another risk. Beside this, the apparatus is very heavy, and exceedingly difficult to transport and erect, even in a civilized country.

Such is a very summarized account of the instruments hitherto employed, and it seems to me that the time has now come when much can be gained by the employment of fixed instruments and a moving large plane mirror. This idea of using a heliostat is, of course, not new, for it has been used several times on a small scale, and for special purposes. There is nothing beyond the difficulty of making a plane mirror sufficiently large for the work to prevent the adoption of this method in the future; and this difficulty now has ceased, as it is only a matter of time and labor to make plane mirrors of sufficient size. With a large plane mirror, twenty inches or upwards in size, mounted on a heliostat mounting, and so arranged as to reflect sunlight into a series of instruments rigidly supported in a horizontal position, the difficulties of eclipse observers will be very considerably lessened. The one driving clock will keep the pencil of light constantly in the same direction, and this can be used partly for photographing the corona, partly for spectroscopic work, partly for polariscopic observations, and so on for any other purposes, the whole of the instruments being fixed in the best possible positions for the observers. Practically, with a large flat mounted in the manner indicated, we can fix any portion of the sky we require to observe, and to do it we can point as many instruments as we can crowd into the pencil, each instrument being quite independent of the others. The length of focus of an objective would not introduce any difficulties on this plan, for the length of the tube is of little importance when it can be fixed in an horizontal position. The observers at the Eclipse Station only have one astronomical adjustment to make, _i.e._, that of the position of the heliostat, and only one driving clock to regulate. This clock, since it has only to move the weight of the plane mirror and its mounting, can be more accurately made and regulated than is possible with a clock when it has to carry the weight of the tube and heavy axis of an ordinary telescope. The positions of the observers are more easy and natural during the precious seconds of totality; or, if personal superintendence is to be abolished in favor of the American pneumatic apparatus, this suggested arrangement of the instrument is better fitted for the pneumatic attachments than the old plan is. The whole of the photographic apparatus can be fixed up in a dark hut or under a dark tent with far less trouble and risk of stray light than is possible with the old manner of mounting.

The cost of a good heliostat mounting is about the same as that of a good telescope, and with one heliostat we can do the work of at least half a dozen of the usual instruments.

A. A. COMMON, F.R.S., and A. TAYLOR, A.R.S.M.

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THE Supreme Court at St. Paul, Minnesota, handed down a decision on July 1st in the case of Ida Moore, of Minneapolis, against Photographer Rugg. Rugg sold a copy of Mrs. Moore’s picture, which was put on exhibition in improper places, much to the discredit of the lady, and she brought suit for damages. The Supreme Court holds that it is a case in which there is ground for the recovery of damages; that the photographer has no right to dispose of pictures which are the sole property of the sitter. The decision is an important one. Similar cases have arisen once or twice previously in other parts of the country.

GENERAL NOTES.

A NOVEL CARBON PROCESS.--Mr. O. Volkner publishes the following dust carbon printing process, which appears to be easy to carry out, requires no reversed negatives, and yields permanent prints. We also think it can be used in making phototypic printing blocks. Make a solution of gelatine in water 1–60, and draw sheets of good strong paper through it, and hang it up to dry. Wet it again and squeeze it down on a piece of glass. Now brush over it a solution of ten parts gelatine, ten parts gum arabic, twenty parts white sugar, eighty parts distilled water. While still quite moist put it in a dusting box (such as used for photogravure) which contains a mixture of 100 parts of white dry sugar and five parts of French lamp black. After a lapse of eight to ten minutes, withdraw it and you will find it covered with innumerable particles of dust. Paper thus prepared will keep, and has to be sensitized in a bath of fifty parts bichromate of potassium, fifty parts bichromate of ammonia, six thousand parts water and aqua ammonia, until it assumes a light yellow color, and at last, to avoid the too quick dissolution of the gum arabic, immerse in twenty parts chromic acid in 1,500 alcohol. Print by Vogel’s photometer 16° to 18°. To develop, use warm water first, and afterwards cold, leaving the print for several hours in water, to which may be added a little aqua ammonia, in case the printing was carried too far. The prints show a singular and very pleasing grain and need no transferring.--_Dr. Eder’s Jahrbuch._

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EVERY photographer is, no doubt, to his own sorrow, familiar with a yellow stain in the negative, caused by taking the plate from the fixing bath before it is thoroughly fixed. Mr. Belitski, the well-known photo-chemist, made some experiments recently to remove this stain, and succeeded very well. A slight stain can often be removed by placing the negative in the following solution: 50 parts alum, 1000 parts water, 10 parts bichromate of potassium, 20 parts muriatic acid. After several minutes the negative turns yellow all through. It is washed now very thoroughly, exposed to sunlight for several minutes, and developed or blackened with the ordinary iron developer. When the stain is very intense this remedy will not prove to be of any avail, and only by leaving it for twenty-four hours in the Lainer acid fixing bath (so often described in all journals recently) he succeeded in removing the stain and saving a valuable negative.--_Deutsche Photographen Zeitung._

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THE article on “Fixing Plates” which appeared in our June number, page 163 should read in the heading “Fixing Prints.” Our readers have doubtless discovered this for themselves before now.

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TRANSCRIBER’S NOTES

1. Silently corrected typographical errors and variations in spelling. 2. Retained anachronistic, non-standard, and uncertain spellings as printed. 3. Enclosed italics font in _underscores_.