This is the dry plate section from Edward L Wilson's 1887 text 'Wilsons Quarter Century in Photography', subtitled 'a collection of hints on practical photography which form a complete textbook of the art'. What makes it particularly useful are the extensive notes from around 300 workers of the time - these are included as supplementary html pages linked from the heading of each section. While in the original book the notes and main text ran through the book with tenuous connection, in this web version they are for the first time clearly linked! 120 years too late...
The number of each section is the original numbering from the book, the dry-plate section starting at 147.

WORK STILL IN PROGRESS, 5/6/06

 147

 148

While, as a rule, it will be found most certain, and certainly the most economical, for the photographer to purchase his sensitive emulsion plates ready made, he may not always wish to do so. Therefore, complete formulae for making emulsions of various kinds will follow, with all the notes of practical worth which have been given as bearing upon the subject.

There are so many methods that manufacturers of plates make a choice, fancying that they see advantages in one which are not possessed by others. This causes uncertainty always as to the sensitiveness, and makes it necessary for the user to make a change in his exposure and development, as well as after-treatment, every time the brand of plates is changed.

Of course, it would be too much to expect a uniform standard of plates. The best plan is to choose a brand from which you can produce the best results and adhere to it. Another good idea is, when you desire a quantity of plates, to test samples made from certain batches of emulsion, find which suits best, and then have your stock order made from that emulsion. Since a number is given by the dry plate manufacturer to each emulsion he mixes, the plan suggested is not a difficult one.

 149

The manufacture of emulsion must be conducted in the dark-room. The purest and best ingredients should be used, and cleanliness and exactitude cared for throughout. It will be understood that the temperature at which the gelatine is cooked, rules the degree of sensitiveness of the resulting emulsion -the higher the temperature the more sensitive the emulsion. Sensitiveness is also secured by the addition of ammonia to the bromide of silver.
Three methods will be given for the preparation of emulsion, therefore, including one, in the practice of which, the slow boiling of the gelatine is followed. The preparation of the glass is substantially the same as that given for the "wet" process, cleanliness being the great desideratum.
I have heard it said that one need not be so careful in this matter, but have seen many bad results from unclean plates.

 150

To prepare an emulsion with ammonio-nitrate of silver based on Dr. Eder's plan - proceed as follows:
A. Bromide of potassium, 370 grains; gelatine, 518 to 694 grains; pure water, 10 1/2 ounces.
B. Nitrate of silver, 458 grains; pure water, 10 1/2 ounces.

A. should first be dissolved. After soaking, say fifteen minutes, place the ingredients in a water-bath at a temperature of 95° to 120° F., till the gelatine has dissolved, and the solution is clear. Now ammonia is added drop by drop to B. until the precipitate first formed is redissolved and the solution is clear. These operations can be carried out in daylight. Now, to the dark-room and in as weak a ruby light as possible, gradually add the silver solution to the gelatine. Shake well after the addition has been made, at intervals, and set aside to cool. Then replace the bottle in the water-bath, which should be at a temperature not exceeding 95°; let it remain for from half to one hour, allowing the water in the bath at the same time to cool down gradually to, say, 75°, not lower. The temperature should not be allowed to sink so low as that, there may be danger of the gelatine setting; but the quantity of water should be sufficient to prevent the temperature falling lower than stated. In adding ammonia, which should be done before adding the silver to the gelatine, great care is needed, lest the temperature rise too high. The water-bath should be watched also, for too high a temderature will cause fog at development. The danger mark is 90 to 105° F.

 151

When the digestion is complete pour the emulsion into a porcelain dish and place it in cold water for the purpose of setting it quickly. When thoroughly set, it is pressed through coarse canvas, and then suspended in a bag and washed either in frequent changes of water, or, better still, in running water for from four to five hours. As the emulsion absorbs a good deal of water during the washing, the latter must be removed either by allowing it to drain for some time, or the excess may be expelled either by gentle pressure or by pouring alcohol over the emulsion. In the latter case only half the ordinary amount of alcohol should be added to the emulsion after filtering. The emulsion may now be melted and filtered, or any sediment may be allowed to subside to the bottom. If the emulsion is to be preserved, an antiseptic should be added, consisting of one grain of salicylic acid, dissolved in alcohol, to every ounce of emulsion. The same weight of oil of thyme - or, best of all, carbolic acid - may be substituted. The alcohol serves a good purpose by acceleratin the setting of the emulsion.

The proportions of potassium bromide to silver nitrate employed should not be less than 4 to 5. With less bromide, fog is apt to make its appearance. This is a nice point and requires extreme and careful attention. As Dr. Eder truly says:

 152

"The difficulty of determining the proper proportions depends on the fact that if too much bromide be employed, the sensitiveness is reduced; if too little, there is a danger of fog. If an emulsion containing a very small excess of soluble bromide be prepared without ammonia, and digested for severil days at a temperature of 110° or 120° F., the process of modification proceeds rapidly, and, owing to the low temperature employed, there is very little danger of decomposition. If, however, the operation is shortened by boiling or addition of ammonia, an excess of soluble bromide is very useful to counteract the natural tendency to fog. In case of long digestion, an excess of soluble bromide retards, but does not prevent the attainment of great sensitiveness."
The conversion of the insensitive into the sensitive modification takes place very rapidly if the directions given above be followed out. Even at a temperature of 77° F., the operation is generally complete in fifteen or twenty minutes. If a small portion of the emulsion, examined on a strip of glass, transmits blue light, the digestion may be stopped, and it will generally be found that prolonging the digestion over thirty minutes does not give material increase of sensitiveness, although, if the temperature be properly controlled, it may be continued for three hours without any decomposition.
If, when the emulsions are prepared, the solutions are too hot, or dissolved silver is insufficiently diluted, or the quantity of gelatine is not properly proportioned, a coarse-grained emulsion, without any corresponding increase of sensitiveness, will be the result. Such an emulsion would be useful in several of the heliographic processes.

 153

As there is no danger of the emulsion losing its setting powers under the low temperature employed, it is best to add all the gelatine at once. In emulsifying with ammonia, it is never advisable to add a second quantity of gelatine to the emulsion after digestion, owing to the renewed heating which is thus entailed. When the action of the ammonia is too prolonged, especially in summer time, frilling is very apt to ensue.
The washing of the emulsion should be conducted with the greatest care, as it is absolutely impossible to attain full sensitiveness in the presence of a considerable excess of soluble bromide; and if any trace of ammonia be left behind, it exercises a caustic action, and combines with any salicylic acid which may afterward be added, so as to reduce its antiseptic properties. Never forget that an unwashed emulsion, prepared without ammonia, will keep fresh for a long time without requiring the addition of an antiseptic.
In proportioning the amount of gelatine to the sensitive salts, it has been stated, that if a hard gelatine, possessed of great power of resistance, be employed, less is required than when a softer sample is made use of. A small proportion of gelatine is to be recommended, for the following reasons: The emulsion when broken up into small pieces, does not absorb so much water during washing. When the emulsion is rich in bromide of silver, there is no necessity for using thick films, which, besides being liable to frill, take a much longer time to dry than thin ones. If, on the other hand, the proportion of gelatine be too small, the bromide of silver is coarse in the grain, and sinks to bottom of the emulsion. In preparing a hard, quick-acting emulsion, employ a large proportion of potassium bromide, a given quantity of gelatine, and one and a half times its weight of silver nitrate. Dr. Van Monckhoven rightly remarks that a large proportion of gelatine gives a soft image; a small proportion a denser but harder picture.

 154

When preparing an emulsion by boiling, and subsequent digestion with ammonia, the following hints must be regarded.
This method gives more sensitive plates, but requires greater care, than the preceding. It depends on the fact that the sensitive modification of bromide of silver forms very rapidly at temperatures between 140° to 212° F., aid that the sensitiveness of such an emulsion, in itself very great, can be Still further increased by subsequent treatment with ammonia at a low temperature. The proportions of the ingredients are the same as those previously given: 370 grains of potassium bromide, which should not be alkaline, are dissolved in 10 1/2 ounces of water, in a strong glass bottle, and 518 to 694 grains of gelatine introduced. The whole, after soaking for some time, is dissolved in hot water, at a temperature of 95° to 120° F. The remaining operations must be conducted in the dark room. To the warm solution of bromized gelatine add 458 grains of nitrate of silver previously dissolved in 10 1/2 ounces of water. The latter may also be warmed over the water bath. There is no absolute necessity for this proceeding. Now wrap the bottle in a thick cloth, and shake well, taking care that the cork is not blown out by the steam. The remainder of the silver may be rinsed out with about two ounces of water. Finally, 1 to 2 grammes of potassium iodide, dissolved in a little water, are added to produce a clearer film. During the boiling which follows, the cork must not be pushed in too tightly, otherwise the pressure of steam might break the bottle. A roll of linen will prevent the bottle coming in contact with the heated surface of the bottom of the saucepan. The best way is to replace the cork during boiling by another in which a small groove has been cut for the escape of the steam. The bottle containing the emulsion is put into a saucepan, covered by a tightly fitting lid, and the spirit lamp or gas jet light below, care being taken that not even the reflected light from the flame falls upon the emulsion. The water bath, which should contain hot water, can soon be brought to boiling point, at which temperature the emulsion should remain for twenty or thirty minutes, after which it may be allowed to cool down. When large quantities of emulsion are being prepared, the boiling should be continued longer. The necessary time of boiling must be reckoned from the moment that the emulsion reaches a temperature of 50° C. If the emulsion is very acid, such as occurs when ammonium bromide is employed, the boiling may be continued for an hour without damage, and with a resulting increase of sensitiveness. But as gelatine boiled in the presence of an acid is apt to decompose, only a small portion of the gelatine should be used, and the bulk added afterward.

 155

The emulsion at this stage will be found extremely sensitive, and can be used as it is; but by further treatment with ammonia, it is possible to increase the sensitiveness considerably.

When the temperature has fallen to about 40° F., two drachms of strong ammonia (sp.gr. 0.910) are added, and the emulsion is digested for half an hour or an hour at a temperature of 95° to 100° F. Then the emulsion is ready for washing, which may be carried out in the same manner as already described.Dr. Eder claims that an emulsion prepared in this way is, perhaps, one-fifth more sensitive than one prepared according to the preceding. It gives well graded harmonious pictures, free from tendency to hardness. The picture appears readily under the developer. The details in the shadows should be fully developed before the high lights are too dense. Emulsions produced by this method are specially suitable for portraiture, although they do not give such absolutely clear glass in the shadows as can be obtained by the first method.
By this method extreme care should be exercised in the choice of materials.

The gelatine and bromide should not be alkaline, otherwise there is danger of fog during the boiling. If a difficulty is experienced in procuring neutral, or slightly acid, materials, the warm solution of potassium bromide and gelatine may be cautiously acidified with dilute acetic acid. The condition of the mixture must be only very slightly acid, otherwise the setting power of the gelatine will be impaired. Warming the bromide gelatine as recommended, before the introduction of the nitrate of silver, hastens the operations considerably. Half an hour is the most suitable period for the boiling, a quarter of an hour being hardly sufficient; while, if the operation is prolonged to threequarters of an hour, fog sometimes ensues. Some samples of gelatine will admit of longer boiling than others. Generally speaking, the emulsion may be boiled so long as it remains clear, and the longer it is boiled the more sensitive it will be.

 156

In digesting an emulsion with ammonia, special care must be taken as to the temperature indicated. Generally speaking, half an hours digestionwill be sufficient, but the operation can be continued for an hour, and even two hours, without danger, and there is more certainty that the desired sensitiveness will be attained. Besides this, the subsequent treatment with ammonia compensates for any defect in the boiling during the first part of the process. The same precautions recommended under the first method, in regard to the addition of ammonia, are applicable in this case. In both methods it is directed that all the, gelatine should be added at the outset. With some samples of gelatine easily acted upon, it may be found necessary only to add part of the gelatine at first, and the remainder after the digestion is completed. Gelatine being the most obstreperous ingredient in use, a modification of treatment may be required by every lot used.

 157

For the preparation of an emulsion by digestion at low temperature proceed as follows:

Although the methods given above are reliable, yet, owing to the extreme care required in the manipulations, and the danger of fog from the use of unsuitable materials, it is thought best to give another formula which may be absolutely relied upon even in unskilled hands.

After what has already been said on the subject, I may give the formula in a few words: 370 grains of bromide of potassium and 617 grains of gelatine are dissolved by heat in 10 1/2 ounces of water, and, as soon as the solutio is complete, the temperature of the mixture is raised to 120° F., and a solution of 463 grains of nitrate of silver in 10 1/2 ounces of water is introduced. The emulsion is placed in a water bath at a low temperature, viz., 90° F., and digested at this temperature. It is well to keep back half the gelatine till after digestion.

If an emulsion is required about as sensitive, or twice as sensitive, as wet collodion, it may be used after six to twelve hours' digestion. Such an emulsion is very well adapted for landscapes or interiors.

If a more sensitive preparation is required, the digestion may be continued for three days at a temperature of 90° F. The resulting emulsion will be very sensitive, and well adapted for portraiture, as it gives soft, harmonious negatives. It may be looked on as one of normal sensitiveness.

 158

Dr. Eder says: "No doubt the best method of washing emulsion is to first break it up into small pieces ; but as, in this state, it absorbs a large quantity of water, I give a method recommended by Heid. The emulsion is poured out after digestion into a tall, square glass bottle, which should not be more than a quarter full at the most. The bottle is then laid on its side, and the emulsion allowed to set. When it has set, the bottle is filled completely with water, tightly corked, and laid on its side so that the part covered with emulsion is uppermost. The water should be changed repeatedly during twentyfour hours, after which the emulsion is read for coating; about an ounce of alcohol should be added previously, and, if the emulsion is to be kept, an antiseptic may be added."

 159

Armed now with a stock of clean plates, slightly warmed, and a quantity of emulsion from which we may expect everything, we proceed to the dark room to unite them. The emulsion is poured upon the plate in the same manner as the collodion, from a warmed measure. A glass rod is used to insure an even coating, and the superfluous emulsion is persuaded from one corner into a bottle. The plate is then placed on a level shelf, and there left to set. From this it is removed to a drying cupboard, and still levelled, there retained at an even temperature until quite dry. This operation should not be hastened. Alcohol may be used in an emergency to facilitate drying.

 160

The exposure of emulsion plates, owing to their increased sensitiveness, should be made with careful study of all the attendant circumstances. The almost morbid desire for instantaneity, now existing to a far too great degree, causes many failures. There is no advantage in quick exposures for general subjects. In fact, there is oftentimes decided disadvantage. Take into consideration everything and use "lightning plates" only when their power is absolutely required. For ordinary work go slower, and take your compensation in better results. When you are a master in precision, then you may use the hair-trigger and expect to hit the glass ball almost every time. Until exposure becomes an inspiration with you, think carefully every time. Of course there are times when one must take the risk and throw rules aside. Accidental pictures are sometimes very fine. The remarks on exposure in another chapter should be regarded.

 161

The development of a gelatine plate is no less beautiful than the moulding of the clay into form by the sculptor. With the knowledge how to mix his potent chemicals, and with a mind that directs carefully, the photographer has power at hand which, with the exercise of the art and science in him, may produce wondrous results. The number of changes he may cause is infinite. A turning of the wrist, a thoughtless movement of the hand, a few drops in excess, or stinting the solution here and there may alter the form and nature of the image as much as the careless pressure and unskilled turning of the clay by the sculptor may ruin the loveliness of the statue.

Two methods of development with their modifications find about equal use amongst photographers. The first method is the alkaline, in which pyrogallic acid, bromide, and ammonia are the chief features; and the other is the ferrous oxalate combination. A few advocate the use of two solutions. Those who use commercial dry plates should develop them as instructed by their manufacturer. The modifications offered by practical worker would fill a volume. This fact seems to throw a deep veil of difficulty over photographic manipulation - to exasperate even sometimes, but there is no reason for being dismayed. Choose a line of practice and then adhere to it. I never yet saw the man fail in our art who was really desirous of success. For the notes below I have, from varied sources, selected what seem to cover all that has been made known on this vital topic. And yet I am aware that in less than a month there may be a hundred more offerings equally as useful. This is as it should be. In an art so beautiful as ours, the more generous rivalry there is, the more enthusiasm, and the more enthusiasm the more growth. And development is growth of the most fascinating description. It affords as much varied pleasure too as anything in art. That is, if I dare apply the word art to anything chemical or physical. If I dare not, then I shall claim that development is more beautiful than art. Every plate I develop is a new pleasure to me. I see something in it - and something comes out upon it which I never saw before. And besides all this, there is always a mystifying apprehension about it which adds to its ebarm and works wonders in bringing about one's best results. The student must not be alarmed at this variety, for even in nature it is rare to find either fruit or flower developed and brought to perfection twice alike. A few words on the rationale of development should come in right here for the help of the novice, before we proceed any further.

After the sensitive plate has been exposed in the camera, it holds what is termed a latent image. Exposed to the light in that condition the obscuration of the film would ensue and prevent all chance of the latent image ever becoming apparent, by whatever means applied. But if it is protected from the light, and developing solutions applied immediately a real image begins to form. A building-up process commences. The particles of reduced silver run, spring, leap, climb, pile up, fall into their places just as the sand of the simoom and the snow of the mountain do and form the elevations and depressions we see. A sectional view of a developed image is a miniature in drawing of what a sectional view of the earth snow covered, sand scattered would be.
I am sure you understand. No small number of the particles of silver go adrift and find no place in building up the image. Some of these are driven away by the wash-water, and the most persistent ones are "cleared" off by the fixing process. The entire operation is fascinating.

 162

One of the great obstacles in the way of successful emulsion work is frilling. It will be treated of presently. One method of preventing it is to immerse the plate in a saturated solution of alum for five minutes previous to fixing it. The negative should be well rinsed before and after this operation.

 163

Hyposulphite of soda is the very best material for fixing. The strength should be, say, four ounces of hyposulphite to a quart of water.

Fast thorough washing should follow the fixing, in order to eliminate every particle of hyposulphite from the film. To determine certainly when this is effected a test may be made of a portion of the wash water as directed for the printing department. If after-treatment is needed, when the plates are perfectly dried, they may be varnished, as directed for the wet.

 164

When the manufacture of bromo-gelatine emulsion plates was taken up in earnest, a great many stumbling blocks were found in the way. Some of the difficulties seemed insurmountable. Those who partially overcame them, although they owed the most of what they knew to the industry of others, withheld their own "finds" rather ungenerously.

This induced Mr. Paget to offer a prize for the best workable emulsion method given free to the public. The prize was won by Mr. W. Wilson, of London, and his process is given below entire.

 165

Still there were drawbacks, one of the greatest being the impossibility of securing a satisfactory degree of sensitiveness without weak, insipid results.

Mr. J. B. Obernetter, of Munich, claimed to have overcome this trial, and announced his readiness to sell his secrets to the public, provided a certain sum was subscribed for him. An effort to obtain subscribers here, resulted in the method being presented to the public by the late John A. Scholten, Esq., of St. Louis. Both of the methods named were published in the Philadelphia Photographer at the time of their being made public. The Obernetter method is also added here, as it first appeared. Scarcely anyone is ever content to work a process in its entirety. All have useful practical hints from which the intelligent worker can draw to suit his inclination.

A multiplicity of methods is given here in order that the manipulator may have a fair understanding of all the means at his disposal. If he is wise lie will choose from the assortment whatever gives him the best results, and then adhere to the same, only modifying as emergencies may arise. And I confess that emergencies never cease - they are always arising. But they do not always require a modification of the chemicals. The whole secret is oftener in the thoughtful manipulation than in the means.

 166

With all that has been provided, still the great desire of the manufacturers has been to produce, and the operators to have, a grade of plate in the highest degree sensitive, with which results equal to slower ones could be had. Up to the present this wish has not been satisfied.

An advantage gained in this direction has been ever opposed by some perverse drawback. Some manufacturers have become so exasperated as to assert that quick plates are "sour grapes" after all, and for some purposes "long exposures" are deemed best. Mons.Balagny, a persistent Parisian photographer, has taken issue with this opinion, and after much patient experiment, offers a means of development which he claims will produce from the most sensitive plates, the best results with the greatest ease. I add his method as sent from France, separated from the notes on developers, that it may be more fairly understood. The two papers were presented about three months apart.

 167

The annoyances which beset the dry-plate maker and worker are numerous. Gelatine is a far less manageable substance than collodion - as sensitive as a neuralgic person to every atmospheric change most exacting in the treatment it requires at the hands of the manipulator. The morbid desire for "lightning" plates often results in weak negatives, so that the demand for a safe and effective means of intensification has had a great deal of careful consideration. The best way is to use such plates as will give the proper density without after treatment, but since this cannot always be, we must turn to the intensifier.

 168

Again, from lack of knowledge as to the exposure, or from careless haste, the negative is too strongly developed, and as a result, is harsh and hard and too dense. In such cases the careful application of a reducing agent must be made. A difficulty always occurs to decide the degree of reduction allowable. Sometimes no amount of coaxing and cajoling will "save" a plate, and it must be discarded. Let it be remembered, once for all, if anything is expected from a defective emulsion plate, it must be earned by patience, care, and skill.

 169

"Fog," or veiling of the film is one of the most exasperating bugbears of "dry" work, and comes without any premonition. In the early days of bromo-gelatine, this disease almost drove the most optimistic advocates of the process from the contest. A careful investigation of the causes was followed by the subversion of the trouble in usual cases. But fog still comes to all, and must be met heroically.

 170

Another one of the common annoyances is "frilling". Its equivalent in animal nature is the kicking of the mule, and the effect upon the human system is about the same. You may use the utmost care in every particular until you come to the fixing of the plate even, when, for some cause you cannot imagine, the film will begin to corrugate and swell and rise in ridges from the glass, and you are surprised and baffled. There seems to be no universal preventive, for sometimes the cause cannot even be guessed at. There is some knowledge on the subject, however, and it has been gathered together for the notes.

 171

Yellow stains; silver stains; developer stains; stains which come before, during, and after the manipulations, have had a great deal of attention. Some of the causes are known and remedies are found. Some are as much a mystery as ever. Frequently yellow spots appear, large and small, after drying. It is believed that during fixation the hyposulphite creeps in through punctures in the film and cannot be removed by any amount of washing - it cannot be reached unless the film is removed and both sides washed. Enough water follows to diffuse this even small amount of hypo between film and glass and cause the yellowness so fatal to good negatives. There seems to be no hope for a negative thus afflicted. There are red spots, too, which make the heart sick.

 172

Spots on gelatine negatives are also caused by "tear drops", the result of unequal drying. If the manipulator will form the habit of watching whether such a nuisance is liable to occur or not, before the negative is dry after washing, it may be prevented entirely by a second slight treatment under the tap. Some brands of plates are apt to dry unequally, and with such the tear-drops are most liable to make their appearance. Bad washing and want of washing bring many a trouble which might as well have been avoided, and frequently cause a grievous deterioration of quality in the negative.

 173

And with all these the chapter on hitches is not ended. No one has confessed as yet that the bromo-gelatine process, wonderful as its capabilities and results are, is the "process of the future," or all that the earnest photographer believes to be possible for his craft to accomplish. There are great attainments before us. They are unveiling every day. We must be patient with what is and hope to do better with what comes.

The novice is oftentimes appalled at the number of drawbacks possible in the practice of photography. An impression seems to have been sent broadcast that our art is "easy" - that "anyone can make good photographs."

Therefore when failures and faults lift themselves up in the way, a good deal of surprise and disappointment follows. This should not be so, because it is not reasonable to expect photography to run any smoother than other pursuits and recreations do. And I do not feel sure that our art would hold the fascination which it does for such myriads. Now, if it was all "smooth sailing," we should then lose our feeling in it - our respect for it if it was "easy." One of the chief attractions attending it consists in the knowledge that one may fail awfully with it if one is not carefully and constantly on the alert. The navigator of the broad and turbulent Mississippi finds a peculiar charm in piloting his way along it, because he knows that, although snags and sawyers abound, he possesses the skill to dodge them, and that he is going to do it almost every time. A kindred pleasure awaits the patient and loving photographer. The long list of obstacles given in these pages is not intended to frighten, but only to forwarn that you may be forarmed.

 174

Once a satisfactory negative has been obtained, every precaution will be taken to protect it - from the heartless, unsympathetic handling of the printer. Varnish is the best preservative, and the method of application is very similar to what has been offered for the " wet" negative.

 175

By far the most learned treatise published on bromo-gelatine work is Modern Dry Plates or Emulsion Photography, by Dr. J. M. Eder, my distinguished colleague of Vienna, and translated by a lamented friend, H. Baden Pritchard. It is published by Messrs. E. & H. T. Anthony & Co., New York. I cannot close this section of my work more aptly than by adding from Dr. Eder's work his carefully collated practical notes.

And yet, with all these things before us, who shall say that the end of the list of photographic possibilities his come? One of the greatest conquests has been to cause gelatine to respond in such an orderly manner, as detailed by Dr. Eder, to our requirements. It was like the "Taming of the Shrew " to make that substitute for collodion answer. The work began with the manufacturers of gelatine, who by careful experiment conquered all difficulties and produced an article that met all the wishes of the emulsion maker, as rapidly as it became possible to do so. Success came through much tribulation and trial, but since it came what marvels have transpired. There are more successes to come provided the mantle of noble generosity, which led the experimenters of the past to give of their knowledge, falls upon their artistic and earnest successors.