1868 JOURNAL OF THE
PHOTOGRAPHIC SOCIETY (London)
Vol. XIII
TRANSCRIPTION CONVENTIONS:
--Italics have been retained from publications, which uses them for both titles as well as emphasis. To more easily locate image titles, I have continued this italicization when titles have been rendered in all capitols or put in quotes, however italics have NOT been used when the general subject of an image is mentioned.
--Photographer’s (or potential photographer’s) names have been bolded – see also below under “Names”
--Brackets [ ] are used to indicate supplied comments by the transcriber; parenthesis
( ) are used in the original sources. If the original source has used brackets, they have been transcribed as parenthesis to avoid confusion.
--Spelling and typos: Nineteenth-century spellings occasionally differs from currently accepted norms. In addition, British spellings also differ from American usage. Common examples are: “colour” vs. “color”; “centre” vs. “center” and the use of “s” for “z” as in “recognise” vs. “recognize. While great care has been exercised in transcribing the 19th-century journals exactly as printed, “spell check” automatically corrects many of these differences. An attempt has been made to recorrect these automatic changes, but no doubt some have slipped through. As for typographical errors, these have been checked although no doubt some have managed to slip through the editorial process. For matters of consequence, I will be happy to recheck the original sources if need be for specific references.
-- Technical articles: For the most part, articles discussing technical aspects of photography, products, etc. were not transcribed unless they are part of a larger article covering photographs. When technical descriptions are too lengthy to include, that has been noted. Exceptions have been made as the transcriber saw fit.
--Meetings of Societies: Names of officers, members attending or referenced, dates and locations of meetings have been given. The first and/or earliest meetings recorded have been transcribed in full. Beyond those early years, only if the reports are very short or discuss photographs, have the articles been copied in full; if administrative or technical in nature. Although not always possible due to time constraints on borrowed materials, when possible, I have included at least the dates of society meetings and any photographer’s names listed.
-- Related, contemporary journals: e.g., The Art-Journal, cover both photographer as well as painting, drawing, sculpture, etc.. As they frequently refer to the production of both the photographer and the painter as “pictures” it is not always possible to tell when photography is indicated. If there is doubt, these articles have been included and the names bolded, but the individuals may, in fact, not be photographers.
NAMES:
--All photographer’s names have been bolded for easy location. EXCEPTIONS: While it is likely that people working with photographic equipment and techniques are also photographers some discretion has been used and not all such names have been bolded. Names of honorary members of a photographic society are assumed to be photographers and thus bolded, when in fact, that may not be the case. Names mentioned in connection with meetings of non-photographic societies have not been bolded unless there is a known or suspected photographic association. A computer word search, however, will still enable the researcher to locate any references to specific names.
--Names: Given abbreviations for titles such as “M” for “Monsieur”, etc., it is not always possible to tell if an individual’s first name or title is being abbreviated. Thus, especially with non-English photographers, too much credence should not be put into an initial that could also serve as an abbreviated title.
--It is not always possible in lists of photographers to know when two separate photographers are partners or not, e.g., in a list, “Smith and Jones” sometimes alludes to two separate photographers and sometimes to one photographic company. Both names will be highlighted and indexed but a partnership may be wrongly assumed. Any information to the contrary would be appreciated.
NUMBERS:
--Numbers referenced in the various journals can refer to either the photographer’s image number, or an entry number in an exhibition catalog. When the number is obviously is obviously that of the photographer, it is included in the index under the photographer’s name, whereas exhibition numbers are not.
1868: JPS, Mar. 16, vol. XIII, #191, p. 20:
Miscellanea: The Forthcoming Solar Eclipse.—
At the anniversary meeting of the astronomical Society, on the 14th inst., the Rev. C. Pritchard, President, made the following statement:-- “The present year will be signalized by a total eclipse of almost the greatest possible duration. As probably centuries may elapse before we shall have again an opportunity so unexceptionably favourable for observing the peculiar phenomena which are only to be seen during a total eclipse of the sun, it will be a source of gratification to the Fellows of the Society that two well-equipped expeditions have already proceeded to India for the purpose of making observations during the eclipse of August next. One of these expeditions, originated by our Society, is under the superintendence of Major Tennant, of the Great Trigonometrical Survey, who will be assisted by Captain Brandreth and three non-commissioned officers of the Royal Engineers. It is proposed to take photographs of the eclipse, for which a reflecting telescope of the Newtonian form of construction, furnished with a silvered glass mirror, has been provided. The pictures will be taken at the focus of the mirror, without any enlargement, by an eyepiece, as was the case with those taken by Mr. Warren De La Rue in Spain. Major Tennant is also provided with suitable apparatus for observing the spectra of red prominences and of the corona, and for analyzing the light of thse objects by polarization.
1868: JPS, Apr. 18, vol. XIII, #192, p. 37-40:
Photography as an Aid to Archæology. By J. Henderson. (Liverpool Amateur Photographic Association.)
Archæology has been defined as “the science of teaching history by its monuments; that is, by every monument of man which the ravages of time have spared.” “By the study of the past we advance the interest of the present, and know how to make use of it for the benefit of the future.”
This being the case, the reproduction by means of photography of objects of antiquity is one among the numerous applications of our art which is now receiving, as it deserves, no small share of attention.
A great deal may be urged in favour of the readiness with which copies of various objects may be made by hand, of their cheapness, durability, and the ease with which they may be multiplied; but against these may be set the absolute truthfulness which is inseparable from a photograph when taken under proper conditions; the facility with which they also may be produced; the great advantage of a stereoscopic combination of views; lastly, with regard to permanence, the carbon and allied processes, and greater care in the production of silver prints, point at least in this direction, while the simplicity of our own collodio-bromide process commends itself for yielding excellent glass transparencies, which, when encased in Canada balsam, would seem to defy the ordinary wear and tear of time.
My attention was first drawn to the subject of my paper by reading a letter in the ‘Times’ in January last, wherein Mr. C. P. Stevens stated he had been enabled to form certain conclusions from photographs of flint implements from gravel-pits at Malton, in reference to which a vexed question was raised. In a letter to me, from the Blackmoor [“Blackmore”] Museum, Salisbury, that gentleman says:--“I had a flint hatchet photographed yesterday; but for such objects photography is not very useful, as the yellows come out too dark.
“For matters of detail, photography is admirably adapted, or for mere form. Our museum is set apart for pre-historic archæology, and for weapons, and so on, in use by modern savages, as illustrating the collection, and photographs of rare forms of club, spears, ornaments, tools, weapons &c. are useful and valuable to us. We also collect photographs of the aborigines of various countries; and for this nothing is equal to photography, because artistic licence is impossible.
“For dolmens and other megalithic structures, photography is a magnificent agent; likewise for sculptured stones of the early periods. Of course I do not now allude to any application of the art as available for other than purposes of archæology.
“Our county archæological societies employ photography largely in their work, and the Hampshire Society also. Some photographs of the Roman city of Silchester were taken during a recent visit of that Society to the spot.”
Many important historical monuments are in inaccessible position, which the artist has to visit hurriedly, filling up subsequently the details of his imperfect sketches. This photography does effectually on the spot. Many objects of antiquarian interest are fragmentary, and form a mere portion; the probable outline of the whole has to be deduced; others (such as cinerary urns, bones, and implements, and also Roman frescoes), when exposed after ages of interment, rapidly crumble in our atmosphere, and are lost for ever. A sketch is often attempted by a rude draughtsman, where a photograph would render invaluable aid.
The character, date, and evident use of objects, as in the foregoing instances, are frequently determined by the situation and other circumstances under which they are found; and here our art is of great use.
I have, on a former occasion, referred to “architectural photography,” and now, in relation to the archæological part of the subject, I may add that, although the architect will learn more by making a careful sketch of an old building, yet you will very seldom find two sketches of the same subject which agree perfectly, while the time and skill necessary to copy the endless intricacies of detail (say) in a Gothic building, would be better spent in taking a few photographs of the same. Photographs show the difference in the courses of masonry, which often determine relative dates. They also show the juncture of work of different periods and alter insertions; and in connexion with this subject I may urge the desirability of photographing churches, &c., before and after restoration.
As illustrating and adding force to what I have said, I may remind you of what has been done by our own Government, by public and other bodies, and by individuals who have employed photography for the purposes I have named.
By command of Her Majesty, photo-zincography has been employed to reproduce in facsimile a selection of the national MSS. Of England, from the Conquest to the reign of Queen Anne. Thus far, 230 have been published, to which the Domesday Book must be added. About 80 MSS. Of Scotland are already in the hands of the public, and more of that country, and also of Ireland, are to follow. By the same process some municipal and other archives have likewise been copied.
The Ordinance Survey of Stonehenge and of Turnsachau (I. of Lewis) is accompanied with illustrative photographs.
In a communication received after the rest of my paper was written, Mr. C. J. Stevens, in speaking of the value of the Ordnance photographs of Stonehenge, refers to his remarks upon them in the ‘Athenæum,’ also to Mr. Parke’s photographic illustrations of the “Antiquities of Wells,” and after enumerating photographs of Celtic and other relics (including those of the Swiss lake-dwellings), he proceeds to say: “The stone axe from Malton, and the beds from whence it was derived, are chiefly known to archæologists by the published photographs of them;” and concludes thus: “An artist is not necessarily an archæologist, and he may slur over or misrepresent some trifling (to him) detail. I have a photograph of a church, with the village, cross, &c., upon the latter, even the chalk scribblings of boys are shown. No artist would have taken this; but in a strange country and with all to learn about the antiquities and the people, such minuteness is invaluable.”* (*I am indebted to Mr. Stevens for the permission to use his remarks, which were not intended for publication.)
The India Office has published an important work with photographic illustrations—‘The Textile Manufactures and Costumes of the People of India’: and the Indian Government has recently directed the whole of the ancient buildings of India to be photographed.
The Ordinance Survey of Jerusalem has been the means of many valuable photographs being taken there; and the Hon. Secretary of the Palestine Exploration Fund also says: “We have already materials for almost an entirely complete and accurate map of the country, and photographs of more than 300 spots and objects, large numbers of which have never before been taken.”
There are catalogues of photographs of about 10,000 objects of antiquarian interest in South Kensington Museum, not to mention the numerous photographs taken of loan and other collections, and also at the British Museum.
While making a passing allusion to the use made of photography by our English and other Antiquarian Societies, I may mention that the Archæological Society of Rome have proposed to photograph any antiquarian discoveries they make, and send copies to the Society of Antiquaries in London for publication. One account says: “Mr. J.H. Parker is proceeding with a collection of photographs of the ancient monuments of Rome and the Campagna, with a view to facilitate the researches of archæological students, and demonstrate the successive styles of Roman construction during the periods of the kings, the republic, and the empire.” At that date about 500 photographs had been so taken.
The mysterious remains of Egypt have attracted the attention of photographers from the first. Frith was early in the field, and was followed by Bedford; who also illustrated Palestine, Greece, &c., The Vicomte de Rongé, in his mission to Egypt in 1863-4, produced six volumes of hand-copies of inscriptions and 220 photographs.
Professor Piazzi Smyth lately took 166 photographs at the Pyramids (many for the lantern) and 50 stereo views. Most of them were taken “solely with a view to procuring aids to scientific enquiry.” They were produced on glass slips, 3 inches by 1 inch, exposed while in the bath, and they include eleven views in the interior of the Great Pyramid by magnesium light. He prefers stereo views taken with two cameras, and very justly urges the taking of distant objects with the cameras placed widely apart. This, I think, we might often do with advantage, using one stereo camera, first taking one half and then moving the camera and refocusing for the second half.
In this connexion I ought to mention the labours of Thompson among the ruins of Cambodia, Fergusson and Hope in Indian architecture, and Svaboda at the Cave of Elephanta, likewise in Mesopotamia and on the sites of the Seven Churches of Asia. Helsby has illustrated some of the antiquities of South America; and a new work on Central America by Squier is, I believe, to be illustrated by 3000 photographs; and any one acquainted with the elaborated monuments of that country will admit that by no other means could fair representations be given.
It would be tedious to enumerate the volumes bearing on antiquities which photography has illustrated, either directly by silver or other prints, or as furnishing a groundwork to the wood-cutter. In ‘Sinai Photographed, or Contemporary Records of Israel in the Wilderness,’ Lord Lyndhurst suggested the application of photography “as the only way so to certify their copies of the inscriptions as to silence cavil.” Noel Humphrey’s interesting work on the ‘History of the Art of Writing’ is cleverly illustrated by photography.
`Our art-science has been employed, to some extent, in illustration of old coins and medals, also in copying old mosaic pavements on a reduced scale. Some time since Mr. Rejlander turned his attention to the ancient brasses for which our country is so famous; and, by superimposing rubbings on sensitized paper, obtained copies of the same size as the originals. I am of opinion that negatives of the rubbings, reduced to a known scale, would yield equally useful and more convenient prints.
Of the numerous works of antiquarian interest I will only mention ‘The Ruins of Pompeii;’ but I may mention that, as its counterpart in this country, ‘Uriconium,’ a photograph previously taken, was useful in enabling 120 columns of a hypocaust to be restored after they had been wantonly overthrown.
Some of the details at Iona, and upwards of a hundred photographs at Melrose, have been taken, the latter embracing everything of constructive or ornamental interest; and it is somewhat in this spirit that I would urge the copying, by photographic means, wherever practicable, of such works of antiquity as remain to our own day, as well for the purpose of study as for transmission, if possible (either in the form of negatives or prints), to posterity, to whom the originals may be partially or entirely lost.
The portico of the Temple of Dendera, on the Nile, was added by Tiberius; but against this recent acquisition may be set the fact that Egyptian monuments known to exist in the fourteenth century are now no more. Of some treasures of antiquity now lost, only rude representations have come down to us; for example, on the arch of Titus at Rome we have some of the sacred trophies from the Jewish Temple, and in this country drawings of the famed shrine of St. Thomas of Canterbury only exist on portions of an undestroyed window, and in a partly burnt manuscript.
The idea I have suggested may appear speculative, if not visionary; but who shall say whether our art-science may not be the means of much more being known hereafter of men and things as they existed in the nineteenth century than could have been had photography been unknown?
Let me conclude in the words from the ‘Essays of Elia:’-- “Antiquity! thou wondrous charm, what art thou? that being nothing, art everything! When thou wert, thou wert not antiquity; then thou wert nothing, but hadst a remoter antiquity, as thou calledst it, to look back to with blind veneration, thou thyself being to thyself flat, jejune, modern! What mystery lurks in this retroversion? or what half Januses are we that cannot look forward with the same idolatry with which we for ever revert? The mighty future is as nothing, being everything? The past is everything, being nothing!”
1868: JPS, Apr. 18, vol. XIII, #192, p. 40:
Miscellanea:
Art Exhibition in Lancashire.—An intended exhibition of works of fine art, to be held at Darwen, in Lancashire, is announced to be opened in May. As photographs will form an important feature of this exhibition, those of our readers who have pictures worthy of public display will do well to contribute to what appears likely to be an important and interesting local exhibition. Communications should be addressed, without delay, to W. S. Ashton, Esq., Hon. Sec., Darwen, Lancashire. The object is to provide funds for establishing an Educational Institution in Darwen.—Photographic News
1868: JPS, June 16, vol. XIII, #194, p. 64-72:
How Mr. Warren De La Rue photographed the Moon.
The sharp and delicate photographs of the lunar disk obtained in such perfection by Mr. Warren De La Rue, F.R.S., are produced by apparatus and manipulations which by long years of care and experience have necessarily been brought to a high state of perfection. The processes producing such excellent results it is now a work of pleasure to publish in detail.
Mr. De La Rue’s observatory is built in the grounds of the private residence of the owner, at Cranford, a little village about two miles from the Southall station of the Great Western Railway. In the days of old the house and grounds were the property of the Hon. Grantley F. Berkeley; but this remarkable man of letters has disappeared from the vicinity of Cranford, to give place to the man of science. Unlike most observatories, that at Cranford has no dome, the revolving roof being of drum shape. This is built of wood, the top being covered with copper, and turns upon a circular wall of solid brickwork. The internal diameter of the room is 18 ft. 6 in., the moveable part rotating upon what is known to astronomers as a “live ring.” There are two rails, one of which is fixed upon the brickwork, and one to the underside of the drum; and between the rails is a series of rollers linked together that they may be kept in place. While the drum rotates the ring rotates also, but of course at half the velocity. The vertical opening, giving telescopic access to objects far removed from the zenith, is 3 ft. 6 in. in width, and closed by two shutters B, B, which run upon rails, and are easily moved by the hand. The top part of the opening in the roof of the drum is closed by a cover C, running upon horizontal rails A, A, which project beyond the circumference of the durum; it works very easily. This opening in the roof extends from the periphery to beyond the zenith, and like the vertical slit it is 3 ft. 6 in. wide, it being well known that great width of opening is best for good definition, because warm air, escaping near the sides of the slit, otherwise tends to encroach upon the field of view, and cause indistinctness by unequal refraction. To keep the telescopes and other apparatus in good working order the observatory is warmed with hot water, heated by means of a gas-stove in the lower room D, which, however, is not used when any observations are to be made. The large reflecting telescope in the centre of this room stands upon the top of a square pillar of solid masonry passing through the floor and through the centre of the room below. The lower room D is devoted to the photographic manipulations.
The mirror of the reflecting telescope M, by which the celestial photographs are taken, is of 13 in. diameter, and 10 ft. focal length. It is mounted equatorially with a modification of which is known as the German plan, which modification permits the telescope to pass all round the pole, without being interrupted by the metal dial-shaped pillar E, which gives it support. The instrument has no tube properly so called, but in place thereof a skeleton arrangement F, F, made of iron gas-piping F’ strengthened diagonally with wire braces F’’ drawn tight by nuts. It is a Newtonian telescope,--an elliptical reflector of speculum-metal, G, whose minor axis is two inches across, being used to change the direction of the rays and throw them into the eyepiece H. When photographing, this second reflector and the arm which carries it are removed, and the image is thrown direct from the large speculum on to the sensitized plate placed in the holder I. In the earlier experiments the diagonal reflector was not removeable, and the pictures were taken after two reflections; after the change was made Mr. De La Rue did not gain in rapidity of exposure quite so much as was expected, showing that the chemical rays are not so much absorbed by the metal of the second reflector as Steinheil’s experiments on the loss of the optical rays would have led one to expect. The clock-driving apparatus K of the telescope has some peculiarities of construction, because an exposure of some seconds is necessary to get a picture; so the instrument must follow the movement of the moon accurately and steadily, and permit of its rate being easily altered. A driving-clock, if adjusted to follow a star, must be altered more or less to follow the moon; and it is practically found most convenient to effect this by altering the length of the pendulum; this is done by screwing up or down the bob k1 . The clock, as will be seen by reference to the drawings, is furnished with a conical pendulum, which is driven through the intervention of a Siemens governor k2; and the rapidity of the pendulum itself is regulated by the friction of a little brush k3, upon a horizontal circular brass plate k4, an arrangement which is found practically to give the most constant velocity. Thus, when it is required to make the clock go slower, the pendulum bob is screwed down a little. The clock has a detached hour circle, L, and is driven so as to always mark sidereal time, as in the Astronomer Royal’s arrangement, so that when a star is to be found it is only necessary to set the instrument to the right ascension and declination of the star, which will then be found in the field of the telescope. The instrument has two speculum metal reflectors, both of which were made and polished by Mr. Warren De La Rue; it also has two reflectors of silvered glass, one by Steinheil, of Munich, and one by Mr. With. When not in use these mirrors are carefully boxed up and protected from damp by means of lime. The hour and declination circles on which the divisions are marked are made of gun-metal, into which are inserted rings made of an alloy of palladium and silver, a compound which not only resists oxidation as well as platinum, but is a much more tractable substance to work.
A stage N is made for the observer; and he can raise or lower himself by simply turning a small wheel n1 in front; stairs n2 at the back of the stage make the stage accessible from the floor of the room. The stage runs upon castors, and in its motion round the observatory is guided by a carriage n3, which runs upon a central circular rail n4, passing round the telescope and its supporting machinery. Some little boxes fixed to the upper framework of the stage hold the eye-pieces, which are thus always within easy reach of the observer.
I(n consequence of their vast distance, the fixed stars cannot be magnified by a telescope so as to give a measurable disk; hence their image in the instrument, when projected upon a photographic plate, is a mere speck, almost too small to be seen except with the aid of a lens. If the telescope be allowed to remain stationary, so that a star in its motion through the heavens shall cause the small image of itself to travel across the photographic film, it is natural to except that the track of the star upon the plate should be marked by a straight or curvilinear line as fine as a hair. But when the experiment is tried, the line is found to be broken up and distorted, because the every-varying density of the atmosphere causes currents and unequal refraction, consequently a flickering motion of the image of the star. For this reason photographs of the heavenly bodies are never so sharp as the optical image in moments of finest definition, and should be taken with great rapidity, because the image will not keep still upon the plate, owing to the changes in atmospheric refraction. Highly sensitive and pure collodion is therefore necessary in astronomical photography to get anything like a perfect picture. In taking heads upon a large scale in photographic portraiture the operator is usually troubled with an opposite defect, for the lines and wrinkles come out unpleasantly sharp; and one method of overcoming the difficulty (devised by Mr. John Traill Taylor, one of the editors of the British Journal of Photography) is to stretch a piece of catgut between the floor and the camera, this string being played upon a fiddle-box during the exposure of the plate, whereby a vibratory motion is given to the camera, sufficient to soften the sharp lines, and the music produced causes a soothing expression to creep over the face of the sitter. The difficulties of the astronomical photographer are not so easily overcome; his only resource is to reduce the time of exposure, and work on those favourable nights when atmospheric disturbance is at its minimum. Such nights are very few in the course of a year, though there are many evenings when approximately good pictures can be obtained. The slightest mist is fatal to good astronomical photography; but light fleecy clouds, when the air is bright and clear, are no great impediments to success.
When the moor or a planet is to be photographed with the apparatus already described, the operations begin by selecting a glass plate for the picture. Mr. De La Rue uses the flatted crown plate,* (*Formerly he used the extra-white patent plate; but this glass is so hygroscopic that many pictures have been lost by its absorbing moisture and destroying the collodion film; hence the use of this kind of glass has been discontinued.) the best glass obtainable for photography; and after receiving a parcel, he rejects all those which contain specks or air bubbles; so that one-third of the supply is usually at once case aside. The glass is cut into circular disks 2 ¾ in. in diameter, because the shape of the holder, I, is round, in order not to stop off more of the central part of the aperture than is necessary. Shortly before use the edge of the glass is roughed with a piece of sandstone, such as is used by gardeners to sharpen their scythes. After washing away the grit carefully, the surface of the plate has to be made chemically clean, as good a method as any being to rub it well with prepared whiting and a strong solution of cyanide of potassium mixed up to the consistence of cream, then rinsing it with clean water and drying and polishing it with a clean cloth. The cloths used must be free from all traces of dirt, grease, or soap; so they are usually prepared by washing in a warm solution of common soda, after which they are rinsed many times over in successive changes in clean water, to get rid of the alkali, and are then dried.
The cleaned plate is next coated with collodion; and the choice of a suitable collodion is a matter of some importance. Mr. De La Rue uses good commercial samples of plain collodion, iodized with iodide of cadmium only, and no bromide. Collodion containing cadmium salts is noted for its stability; for potassium and other alkaline salts strike a yellow colour, due to decomposition, very soon after mixing with plain collodion, especially when the latter has already been long kept. The sample of plain collodion chosen should be more limpid than usual; for iodide of cadmium tends to make it gelatinous; it should also give an even film upon the glass, free from structural markings. The sample of pyroxyline from which it is made should be one which does not give a tough strong film, but a film readily permeated by liquids. An iodide-of-cadmium collodion, when made from a pryoxyline which gives the highest sensitiveness, is very liable to spots and markings; and pure chemicals, absence of dust, and cleanly manipulations are necessary to get uniformly good results. Mr. De La Rue is very careful to have no traces of sediment in the collodion itself; for he says:--“Collodion should not be sensitized until after it has stood for at least a week after it has been purchased; and it must then be carefully poured into the mixing-vessel without disturbing the sediment which is always present. It must be agitated occasionally for some hours after mixing with the sensitizer before it is set aside to rest and deposit the new sediment which forms. After standing for a month or two it should be carefully decanted for use, to the extent of three-fourths, into a perfectly clean glass bottle.” The plate, having been coated with collodion, is dipped into a bath containing thirty grains of pure fused nitrate of silver to each ounce of distilled water. This bath is perfectly neutral if the nitrate of silver has been carefully fused at the lowest temperature requisite for its fusion.
The best way of effecting the fusion is to put about sixty grains of crystallized nitrate of silver into a small porcelain dish, heated by an air-flame gas jet, and as soon as the mass has melted pout it into about a quart evaporating-basin previously heated a little over 212 deg. Fahr. (100 deg. Cent.). By a rapid whirl of the basin the fused mass forms a thin ribbon easily broken with a glass rod. When broken it is transferred into a counterpoised stoppered bottle, and weighed at once for use. In preparing the baths the nitrate of silver, 600 grains, is dissolved in two ounces of distilled water, and to this a solution of five grains of iodide of potassium in about a drachm of water is added. The precipitate at first formed is soon redissolved. Eighteen fluid-ounces of distilled water are added, little by little, and the whole agitated. A precipitate of iodide of silver separates, and it is allowed to deposit in the dark for twenty-four hours. The clear liquid is then passed through a filter previously washed with a little nitrate-of-silver solution. A bath thus prepared is at once in working order. When it becomes less sensitive, as it will do after a time by the accumulation of alcohol and ether and their derivatives, it cannot be restored by doctoring; so that when failures occur it is best to discard the old bath, and to have recourse to a new one. Mr. De La Rue usually prepares about a gallon at one time, so as always to have a store at hand; for it may be kept for any length of time.
The plate having been sensitized is at once exposed. When pictures of the moon are to be taken the time of exposure varies considerably. When it is full moon and the atmosphere is clear, the pictures may sometimes be taken instantaneously, and in this phase an exposure of from one to two seconds is usually the utmost that is necessary. The moon as a crescent would require ten to twenty seconds’ exposure under similar circumstances, in order to obtain a picture of the parts visible near the dark limb; and in order to get these dimly-illuminated portions in most perfection the brighter limb of the moon must be somewhat over-exposed. An almost imperceptible mist in the atmosphere will sometimes double the time of exposure. During this operation a clock beating seconds distinctly should be in the room, that the operator may be able to measure the time of exposure with accuracy. The planet Jupiter, when in opposition, is photographed in about five seconds, Saturn in from twenty to thirty seconds. The plateholder 1, for exposing the plate to the luminous image, is made entirely of metal; and the circular plate, when placed in it, rests at portions of its edge upon three silver supports. This is a much better plan than letting the wet plate rest upon wood, because in the latter case impurities from the wood often find their way across the solution on the plate, and in the development stains and faults result. The plate-holder is well dried with a cloth before the next picture is placed in it. Above all things, in taking astronomical photographs, it is necessary that the sensitized plate should be placed exactly in the focus of the telescope. The focusing is first done approximately upon ground glass, but finally upon a silvered collodion film placed in the plateholder itself. The latter film is made by sensitizing a plate in the usual way, briefly exposing it to diffused light, then throwing down a light deposit of silver with the developer, washing, fixing, and drying. A few scratches are then made upon the film, which is placed in the holder, the image of the moon is allowed to fall upon it, and the focusing is done from behind, the operator making the picture come to focus on the film while he makes the adjustments with the aid of a lens sliding in a tube, and in the first instance focused on the scratches.
After the plate has been exposed in the camera it has to be developed. Iron developers are of little use when the collodion, as in this case, contains no bromide salt, and Mr. De La Rue rejects them altogether, because he finds that pictures produced with them always show granulation, whilst negatives developed with pyrogallic acid will bear examination under the microscope. To get rapidity it is necessary to employ a weak retarding acid, and to use as little of it as possible. Mr. De La Rue makes his developer of pyrogallic acid three grains, glacial acid one fluid-drachm, distilled water three fluid-ounces. In very cold weather the above quantity of acetic acid is reduced. After the picture has been developed it is never intensified as in ordinary photographic operations, because some loss of detail in the image is always the result of such treatment, and thin negatives are best to produce enlargements. Lastly, the picture is fixed with hyposulphite of soda, and very thoroughly washed afterwards; for although a very faint trace of this salt left in the film might be harmless for some years, it would eventually cause the destruction of the pictures. After the washing, the finished picture is put aside to dry.
The picture of the moon thus obtained is only about 1 in. or 1 2/10 in. in diameter, according to the distance of the satellite from the earth. The greater the focal length of the telescope the larger would be the direct pictures of the moon obtained; so that with Lord Rosse’s telescope it would be possible, by means of good clockwork and high-class photographic ability, to get magnificent pictures of the moon between 6 in. and 7 in. in diameter. The great Melbourne telescope is provided with photographic apparatus, and will give pictures of between 3 in. and 4 in. diameter. Mr. Le Suen, who will have the direction of this instrument in Melbourne, has worked at Cranford, so as to familiarize himself with astronomical photography. Such pictures, if obtained, would be of scientific value. Mr. Warren De La Rue finds that parts of the moon which are equally bright to the eye do not reflect the chemical rays equally; for there is considerable difference in the intensity of these parts in the photograph. Jupiter and Saturn, as taken at Cranford, are small specks upon the photographic plate, and require a magnifying-glass to show details. Saturn’s rings, and the belts of Jupiter, are then distinguishable in the pictures.
When an astronomical pictures has been obtained and finished, it becomes necessary to render it permanent and safe from liability to injury. This is done by cementing a second sheet of glass in optical contact with the picture by means of Canada balsam, so that the film is protected like a fly in amber. A brass plate, about 18 in. long by 9 in. wide, is supported upon four legs, each about 8 in. in length. Lengthways, underneath the middle of the plate, is a gas-pipe with a row of holes along the top, giving a line of little jets heating the plate above. Levelling-screws on the legs, and a circular spirit-level laid for the purpose upon the plate, enable the latter to be adjusted in a truly horizontal position. The plate of glass is then laid picture-side uppermost upon the brass plate, by which it is heated. A smaller circle, 2 in. in diameter, of plain clean patent plate glass, having also been warmed upon the brass plate, is then laid over the centre of the picture, but not so as to touch it; for a slip of thin paper has its end laid under the edge of one side of the upper glass. A few drops of Canada balsam are then allowed to drop upon the lower glass at the point where it is touched by the upper one. The balsam is rendered more fluid by the heat, and slowly travels on its way between the plates of glass, being drawn on by the force of capillary attraction. Slowly does it travel between the plates; and when it has gone a little more than half its journey across, the slip of paper is removed, and the balsam at last fills up the infinitesimal space between the upper and lower plate. This operation requires patience, as it takes about a quarter of an hour before it is complete; and when any feeding with balsam is necessary, it should be added to that side where the upper glass touches the lower one. At the close more Canada balsam is applied round the edge of the upper plate, and the cemented picture is left for a little time upon the brass plate that much of the volatile essential oil contained in the balsam may be driven off by heat.
In one of the British-Association Reports written by Mr. Warren De La Rue there is much information about the history and results of celestial photography. Therein we learn that “the late Professor Bond, of Cambridge, in conjunction with Messrs. Whipple and Black, of Boston, in the United States, first obtained a picture of the moon by the daguerreotype process. This photograph was taken in the focus of the great refractor of the Howard Observatory of 15 in. aperture, by Merz, of Munich; but experiments were then discontinued till 1857, when new and better clock machinery was attached to the telescope. Mr. Warren De La Rue began taking positive lunar photographs by the positive process in 1852; but in 1857, after good driving-apparatus had been attached to the telescope, he first began taking negative pictures. Professor Phillips, aided by Mr. Bates, obtained some lunar photographs in 1853; and after 1854 more or less has been done in astronomical photography by Messrs. Hartnup, J.A. Forrest, M’Innes, Crookes, Fry, Huggins, W. Allen Miller, and Padre Secchi. These experimentalists nearly all used refracting telescopes, in which the chemical and visual foci are not coincident, so that it is more difficult with such an instrument to bring the photographic rays to a sharp focus upon the collodion film. In The telescope employed by Professor Phillips, of 6 ¼ in. aperture, and 11 ft. focal length, the actinic focus was found to be 0·75 in. beyond the visual focus; and in the Liverpool equatorial of 12 ½ ft. focal length the actinic focus was 0·8 in. beyond the visual focus. In the reflecting telescope all the rays of the spectrum are brought to a focus at the same point; and to this fact Mr. W. De La Rue ascribed much of his success in celestial photography. As to the degree of that success, he has “obtained pictures of the moon that bear examination with the 3-in. object-glass of a compound microscope, magnifying about sixteen and three-quarter times, and which show, with excellent definition, details occupying a space less than one second in each dimension. One second is equal to about 1/1720th of an inch on the collodion plate in the focus of the telescope; and in the finest photographs details occupying less than 1/2000th of an inch are discernible with the object-glass; hence much valuable work ahs already been accomplished. A second on the lunar surfaced at the moon’s mean distance being about one mile (1·149 mile), it will be evident that selenological disturbances extending over two or three miles could not escape detection, if such occur, provided photographs continue to be taken for a sufficiently long period.”
The photographs of the moon are not always of the same size, as the satellite is not always at the same distance from the earth, and the nearer it is the larger will be its photographic image. Therefore the pictures taken with the same reflector vary in diameter from 1 in. to 1 in. and nearly two-tenths (1·0053 in. to 1·1718 in., being at the moon’s mean distance 1·0137 in.) The moon does not always present exactly the same face to the earth; hence some pictures may be chosen from Mr. Warren De La Rue’s collection which appear to stand out like a solid globe when two of them are placed in the stereoscope. Two such pictures enlarged upon glass, so as to give positive images by transmitted light, were exhibited as stereoscopic transparencies at the meeting of the British Association at Leeds; and the effect was very fine, such illuminated images being the most beautiful that photography can produce. As pointed out by the Astronomer Royal, the fact that stereoscopic pictures can be taken of our satellite is experimental demonstration that the moon is a globular and not a flat body.
The photographing of the planets is difficult work, because the image thrown upon the collodion film is very small, only a spot in fact. The fixed stars, which are simply points of light upon the film, may also be taken; and Mr. De La Rue has obtained some photographs of the double star Castor, also of other stars; but he confines his attention principally to the moon, taking from time to time photographs of the planet on those rare nights when the atmosphere is quiescent. In photographing a planet he usually takes several pictures of it upon the same plate. After one picture is taken, the connexion between the telescope and driving-clock is broken without the clock being stopped; and when a certain time has elapsed the clock is again connected, and the image is allowed to fall once more upon the plate. But, as the planet has changed its relative position during the stoppage, its image falls in the second instance upon a different part of the plate. In like manner several pictures may be taken upon the same piece of glass. On the 8th of November, 1856, Mr. De La Rue took a picture of Jupiter at nearly the time of its occultation by the moon . The planet had then a pale greenish tinge of about one-third the general brilliancy of the moon; but the actinic power of Jupiter’s light was subsequently found to be equal to fully four-sixths or five-sixths of that of the moon. Saturn required twelve times as long as Jupiter to produce a photograph of equal intensity; yet on May 8th, 1859, a picture of Saturn, together with that of the moon, was taken in fifteen seconds, just as the planet emerged from behind the moon’s disk. When two pictures of the moon and a planet are both taken upon the same plate within a short interval at the time of occultation, a stereoscopic picture is obtained in which the planet or star appears further off than the moon. Stereoscopic pictures may be taken of Jupiter by allowing a sufficient interval to elapse between the two exposures of the plate. In the space of twenty-six minutes the planet will have rotated through the 15 deg. 48 min. necessary to produce the greatest stereoscopic effect. Mars takes sixty-nine minutes to rotate through the same angle. The markings on the other planets are too faint to hold out a promise of similar results. Although this is the case with respect to Saturn, the apparent opening and closing of his ring as he revolved round his orbit afford the means of obtaining a stereoscopic picture. In these photographs of the planets the distinguishing characteristics, such as the rings of Saturn and the belts of Jupiter, are discernible, but the image contains fewer details than when viewed by the eye in the telescope.
As already stated, the moon and planets are photographed upon a plate which receives the image direct from the speculum; but pictures of the sun have been taken upon the scale of 4 ft. to the sun’s diameter, in doing which the image was, for the sake of convenience, thrown out through the side of the skeleton tube by means of the diagonal reflector, after which it passed through a secondary magnifier placed in the position of an eye-piece, and fell upon a sensitized plate 18 in. square, placed at a distance of 4 ft. from the magnifier. Plates of this size will not permit, of course, a 4-ft. picture to be taken at once; so the whole disk has to be taken by four successive operations. In this way the spots on the sun are taken on a large scale; likewise the faculæ and mottling of the surface of the sun are clearly depicted. In taking sun-pictures the light is so overpowering that a very short exposure must be given; consequently the exposure is instantaneously produced b y means of a sliding shutter, with an adjustable slit in it, having generally a slit 1/20 of an inch wide. As the shutter falls in a very small fraction of a second, portions of the sun’s image find their way successively through the slit.
Very naturally it may be asked why a large direct picture of the moon may not be obtained with Mr. Warren De La Rue’s reflector, by magnifying the small image with a lens as in the case of the sun. The reason is that the light of the moon is so feeble compared with that of the sun that the time of exposure would have to be lengthened far too much to give any chance of obtaining a good picture. AS the image of the moon is only about 1 in. in diameter, and as the plate upon which it is taken is 2 ¾ in. in diameter, two negatives of the moon may be taken upon the same plate. This is sometimes done, and the clockwork of the telescope is detached between the times that the impressions are taken, so that the moon, by its own motion in the heavens, shifts its image from one side of the plate to the other. In this way the diurnal path of our satellite may be found, and used to supply data for the reduction of the lunar pictures; because a line joining any two similar craters in the pictures, marks the path approximately, the slight lunar motion in declination having to be taken into consideration.
The very perfect little photographs of the moon having been taken as thus described, enlarged copies have been made of them upon circles varying from 18 in. to 38 in. in diameter, the latter being about the scale of Beer and Mädler’s large map. The photographic picture is necessarily the more accurate of the two, from the truthfulness of photography, and from the fact that draughtsmen cannot draw the moon in a short time, so that some portions of their pictures must be taken when the moon has turned itself a little out of its former position with regard to the earth. The copying-camera O, placed in the house P, used to obtain the enlarged pictures is of the usual construction. It is pointed to the north pole (a shutter p1 opening in the roof of the camera-house for that object) for the sake of the steady light emanating from that part of the heavens, which light is allowed first to pass through a tube that the rays may be parallel when they fall upon and illuminate the small transparent photograph of the moon lying at the bottom of the tube. Inside the camera, a little below the illuminated negative, is the copying-lens, which throws an enlarged image of the little photograph upon a large sensitized plate at the bottom of the camera. The lens and small negative may be very accurately adjusted with respect to each other, a small microscope being brought into play in the operation. Generally, positives on the scale of 9 in. to the moon’s diameter, are taken in this way, and the pictures so obtained used for the secondary enlargements. In this copying-process, as might be expected, there is some loss, details being visible in the little negative which are not fully rendered in the enlarged copy. Mr. Dallmeyer, the optician, has recently made a lens, which he says he thinks will render every detail without loss, and when it is received it will be rigidly tested. Attached to the observatory is the transit-room R, used for obtaining time. In another part of the grounds is a 6-in. refractor by Merz, also mounted equatorially, and placed in a very ornamental dome designed by Mr. Owen Jones. A workshop, 43 ft. in diameter (formerly a riding-school), contains the polishing machine, a lathe, and other tools, driven by a steam-engine, and completes the requisites for work carried on at the Cranford Observatory. Mr. Reynolds, who accompanied Mr. De La Rue on the Himalaya Eclipse Expedition in 1860, is the technical and photographic assistant attached to the establishment. Just as we arrived at Cranford, Major Tennant’s staff of sappers had taken their departure after receiving instructions in astronomical photography, preparatory to the observations to be made in India by Major Tennant on the occasion of the total solar eclipse on August 18th of the present year.—The Engineer.