WILLATS'S SCIENTIFIC MANUALS, No. 1. 
 PART II. 
 
 PLAIN DIRECTIONS 
 
 FOR OBTAINING 
 
 PHOTOGRAPHIC PICTURES 
 
 UPON 
 
 WAXED AND ALBUMENiSED PAPER 
 
 AND 
 BY 
 
 COLLODION AND ALBUMEN, 
 
 Including aThird Edition of 1:E GRAY^S TREATISE on 
 PHOTOGRAPHY; a description of the STEREOSCOPE 
 and the manner of taking pictures suited for it ; also, the 
 process for Copying MICROS(X)PIC OBJECTS, ^c- 
 
 EDITED 
 
 By CHARLES HEISCH, F.C.S., 
 
 Lecturer on Chemistry at the Middlesex HospitaL 
 
 Xnhn : 
 
 Richard Willats^ 
 
 aATE T. & E. WILIATS,) 
 
 AND 
 
 PHILOSOPHICAL INSTRUMENT MAKER, 
 No. 28, Ironmonger Lane, 
 
 (Removed from 98, Cheapside.) 
 
 Price Two Shillings, or by Post 2s, &d. 
 
PHOTOGRAPHIC MANUALS, No. 1. 
 
 PART ZX. 
 
 PLAIN DIRECTIONS 
 
 rOB OBTAINING 
 
 PHOTOGRAPHIC PICTURES 
 
 UPON 
 
 WAXED AND ALBUMENISED PAPER 
 
 AND 
 BY 
 
 COLLODION AND ALBUMEN, 
 
 Including a Tliird Edition o/LE GRAY'S TREATISE on 
 PHOTOGRAPHY; a description of the STEREOSCOPE 
 and the manner of taking pictures suited for it; also, the 
 process for Copying MICROSCOPIC OBJECTS, ^c. 
 
 EDITED 
 
 By CHARLES HEISCH, F.C.S., 
 
 Lecturer on Chemistry at the Middlesex Hospital, 
 
 Richard Willats, 
 
 (LATE T. & E, "WILLATS,) 
 
 AND 
 
 PHILOSOPHICAL INSTRUMENT MAKEB, 
 No. 28, Ironmonger Lane, 
 
 (Removed from 98, Cheapside.) 
 
Alfeed Boot, Printer, Dockhead, Bermondsey. 
 
INTEODUCTION. 
 
 The Calotype Process of Mr. Talbot, has been so often and minutely 
 described, that it is not my intention to allude to it in the present work, 
 further than to remark that on it are based almost all the subsequent 
 processes which have been published. Though experiments have been 
 made with all substances sensitive to the action of light, nothing has yet 
 been found to supersede the iodide of silver originally recommended. 
 
 All amateurs of Photography must be aware that success in the 
 practice of the Calotype much depends on the manipulatory skill of the 
 operator, and on the observance of various little precautions which it is 
 almost impossible to describe. Few of those who attempt to follow the 
 printed directions, without having seen the various operations performed 
 by a practised hand, arrive at satisfactory results, until after repeated 
 failures; and this not so much from any deficiency in the explanations, 
 as from the difficulty of describing all the little niceities of manipula- 
 tion, which should be seen to be understood. 
 
 I have endeavoured in the following pages to detail only those pro- 
 cesses which from their intrinsic simplicity are more capable of being 
 perfectly described. The abandonment by Mr. Talbot of his patent 
 right, has given a great impulse to Photography in this country, and it is 
 
 B 2 
 
V. 
 
 to be hoped that the assertion so often made, that the progress of the 
 art here has not been so great as on the continent, will soon cease 
 to be repeated ; indeed the late exhibition at the Society of Arts shewed, 
 that though labouring under disadvantages of atmosphere with which their 
 foreign brethren had not to contend, the English photographers were not 
 so far behind as had been imagined. I cannot but congratulate photo- 
 graphers also on the establishment of a society for the furtherance of the 
 art, headed by artists of such high standing as the Earl Somer's, Sir 
 C. Eastlake, and Sir W. Newton. This must at once silence those who 
 wish to degrade photography to a mere mechanical art, instead of 
 admitting the great benefit which, if properly used, it can confer upon 
 high art. To the numerous friends to whom I am indebted for many 
 valuable hints, I offer my very best thanks for their assistance, and 
 IDarticularly to Mr. Henneman, of whose kindness, and readiness to 
 impart information, it is impossible to speak too highly. In conclusion, 
 I venture to express a hope, that as one of the objects of the Photogra- 
 phic Society is the free communication of all discoveries in the art, 
 the days of patents and secrets in photography may be said to have 
 passed away. 
 
PHOTOGRAPHY ON PAPER. 
 
 M. LE GEAY'S PROCESS. 
 
 M. Le Gray having been the first to propose the use of paper waxed 
 previously to being subjected to any other preparation, and which can be 
 dried, and preserved for some time without deterioration after being ren- 
 dered sensitive, I shall first describe the method of preparing it precisely 
 as detailed by him in his late work Photographie, Traite Nouveau 
 Theorique et Pratique des Procedes et Manipulations,*' published in 
 September 1852, and shall afterwards describe the modifications which 
 the process has undergone in the hands of other operators. After stating 
 that the choice of paper to be waxed before iodizing is less important than 
 of that which is to be used unwaxed, and that he prefers the thin paper 
 of Messrs. Canson Freres to all others, rejecting only those sheets in the 
 thickness of which there are any considerable inequalities, or which are 
 stained with iron,* M. Le Gray proceeds to describe as follows, the 
 
 PRELIMINARY PREPARATION OF THE NEGATIVE PAPER. 
 
 The object of this preparation is to fill all the pores of the paper 
 with white wax, which causes it to be more equally acted on by the sub- 
 sequent preparations. Paper thus prepared assumes the appearance and 
 firmness of parchment, and has the advantage of not requiring to be 
 waxed after the picture is developed, before taking the positive proof. 
 
 * Even these stains may be to a great extent removed by the use of free iodine 
 as hereafter recommended. 
 
6 
 
 Take a large daguerreotype plate, place it on a levelling stand quite 
 horizontal, heat it by passing a spirit lamp backwards and forwards 
 under it, or (which is better) place it on a hot water bath ; when warm, 
 rub a piece of white wax on its surface. 
 
 When you have a good coating of melted wax on the plate, lay a 
 sheet of paper upon it, and bring it into perfect contact with the wax, by 
 passing a card gently over the back. When the paper has imbibed the 
 wax equally all over, place it between several folds of fine white blotting 
 paper, and pass over it an iron heated until a little saliva dropped upon 
 it boils, but does not roll off. If the iron be hotter it spoils the wax and 
 stains the paper. 
 
 A sheet of paper thus prepared should be perfectly transparent, and 
 have no shining places on its surface, as the blotting paper should absorb 
 all the wax which has not completely penetrated the texture of the 
 paper.* 
 
 FIRST OPERATION. 
 
 IODIZING THE PAPER. 
 
 t A. Take rice 200 grammes, isinglass in leaves 20 grammes, dis- 
 tilled water 3 litres. Let them simmer in an earthen vessel till the 
 rice is quite soft, but the grains still unbroken. The liquid will then 
 contain the glutinous matter of the rice, without being rendered thick 
 by the starch. Filter the liquid through fine linen. This liquid gives 
 great body to the paper, and much intensity to the blacks of the picture. 
 
 B. In one litre of this rice water, dissolve of 
 
 Sugar of Milk 45 grammes 0 centigrammes. 
 
 Iodide of Potassium . . 15 „ 0 
 
 Cyanide of Potassium 0 80 
 
 Fluoride of Potassium 0 „ 50 „ 
 
 * I have found it better to plunge the sheets of paper completely into melted wax 
 in a shallow dish, and when well soaked to hang them, previously to ironing them, before 
 the fire, or in a hot air chamber, as long as any wax drops from them. By this means 
 a good deal of wax is saved, and much less left for the blotting paper to absorb. 
 
 Should you use a tin dish, which is not so good as a porcelain one, be careful to 
 have it thickly and perfectly tinned, for if there be the least flaw in the tin, the wax 
 becomes very speedily contaminated with iron, and completely spoils all your paper. 
 
 t These Letters refer to Notes, pages 27 and 28. 
 
7 
 
 When the salts are dissolved, filter through fine linen, and preserve 
 in a well stoppered bottle. This solution will keep a long time, and may 
 be used to the last drop. In cold weather it should be slightly warmed 
 before putting in the paper. To prepare the paper, pour some of the 
 solution into a flat dish, and plunge the waxed paper sheet by sheet 
 completely into it, taking care to remove all air bubbles. The depth of 
 solution in the dish should be at least four or five centimetres,* as by 
 having abundance of liquid the paper is more perfectly iodized. Put 
 15 or 20 sheets at once in the solution, and leave them from half an hour 
 to an hour, according to the thickness of the paper, thick paper taking 
 a longer time than thin. When uniformly soaked, turn over the pile, 
 and beginning with the sheet first immersed, hang them up by one 
 corner to dry, placing a small piece of blotting paper on the opposite 
 corner to facilitate the fall of the drops. Never put English and French 
 paper in the same solution, as the English paper contains free acid, 
 which liberates iodine and colours the French paper deep violet.t 
 
 When the sheets are dry, cut them to the size of your camera 
 frames, and preserve them in a portfolio. This paper is called for 
 brevity's sake, iodized paper. Paper thus prepared should be of a light 
 violet colour, which makes the after preparation easier. This colour is 
 easily obtained when the iodizing solution is old, because it becomes acid 
 by keeping, which liberates a part of the iodine. 
 
 The same effect is produced with a new solution, by adding to every 
 litre 25 centigrammes of iodine, t 
 
 The paper may be prepared thus far by day light, but should not be 
 exposed too long, as though not very sensitive, a long exposure to a 
 bright light decomposes the iodide of potassium, and forms an iodide of 
 starch on the paper.§ 
 
 The liquid which remains after the paper is withdrawn, is to be 
 preserved in a well stoppered bottle; it only requires to be filtered 
 immediately before it is again used. 
 
 * About 1^ inch. 
 
 1 1 have not found this of any consequence ; indeed, I do not see how this 
 statement is to be reconciled with the subsequent paragraph, in which the use of free 
 iodine is recommended, and certainly such good results cannot be obtained without it. 
 
 X 2 grains to 1 pint of solution. 
 
 § I have not found this to be the case. 
 
8 
 
 SECOND OPERATION. 
 
 c 
 
 GIVING SENSIBILITY TO THE PAPER. 
 
 Take of Nitrate of Silver 
 
 20 grammes 
 
 Glacial Acetic Acid 
 Pure Animal Charcoal 
 Distilled Water 
 
 . 24 do. 
 . 8 do. 
 . 300 do. 
 
 Dissolve the Nitrate of Silver in the water^ in a stoppered bottle } 
 then add the Acetic Acid and the Animal Charcoal. 
 
 Shake the bottle, and allow it to stand for half an hour, when the 
 Charcoal will have subsided, and the liquid will be fit for use. 
 
 This solution must be made by candle light,* and preserved in a 
 bottle covered with a black case. The above quantity of solutioiv is 
 sufficient to give sensibility to 20 sheets of paper, 35 centim. long, by 
 25 centim. broad ;t each sheet of this size containing enough iodide of 
 potassium to decompose 1 gramme of nitrate of silver. 
 
 The liquid, after having been used, should be again poured on the 
 animal charcoal, which decolorizes it, and renders it perfectly limpid. 
 
 The little needle-shaped crystals which form on the bottom of the 
 bottle, serve to supply silver to a partially exhausted solution. 
 
 When you wish to prepare the paper, filter as much of the solution 
 as you want for use ; then take two perfectly clean dishes, in the first 
 pour the filtered solution to the depth of 1 or 2 centimst, and fill the 
 second with distilled water. 
 
 Take a sheet of iodized paper, and lay it with one side on the surface 
 of the solution of aceto-nitrate of silver, taking care to remove all air 
 bubbles; then with a hog's bristle brush, press the sheet completely 
 under the solution, and remove all air bubbles from its upper surface 
 with the brush. The hairs of this brush must not be fastened tvith 
 metal. 
 
 Leave the paper in the solution for four or five minutes, or if it be of 
 
 * It is far more convenient to cover a window with two folds of common yellow 
 calico, whicli stops all the chemical, whilst it admits nearly all the luminous rays. 
 
 t 13^in by lOin. 
 
 % From ^in. to finch. 
 
9 
 
 the violet color before mentioned (which is better), until it becomes 
 white. 
 
 Withdraw the sheet from the solution, and plunge it completely into 
 the distilled water, removing the air bubbles with another brush which 
 must be kept exclusively for the purpose.* 
 
 Prepare in this manner ten sheets of paper, and place them one on 
 the other in the distilled water. 
 
 Pour off the water into a bottle, holding the sheets on the bottom of 
 the dish with the brush. Cover them with fresh distilled water, which 
 pour into the same bottle. If you wish to preserve the paper a long time 
 before using, you must wash it a third time. 
 
 This paper must not be dried by suspending it in the air, as it then 
 becomes black all over on being immersed in the solution of gallic acid. 
 It must be dried with perfectly new and clean blotting paper, and pre- 
 served for use between sheets of the same paper, placing first a sheet of 
 prepared paper, and then a sheet of blotting paper, so as to keep the 
 sheets of the prepared paper separate, t 
 
 The paper thus prepared preserves its sensibility for a fortnight, or 
 even a month if it be well kept from the light; it is therefore very valu- 
 able to travellers, who need only carry with them a portfolio with two 
 divisions, one for the prepared paper, the other for the pictures which 
 they take. The image need not be developed for two or three days. 
 
 Having prepared ten sheets of paper, return the solution to the 
 bottle containing the animal charcoal, shake it up, allow it to settle, and 
 again filter it before preparing the remaining ten sheets of paper, for 
 which the solution will serve. When the solution is thus exhausted, pre- 
 cipitate the little remaining silver by pouring into it a solution of chloride 
 of sodium (common salt.) Wash the precipitated chloride of silver with 
 distilled water, and use it to add to the hyposulphite of soda for fixing 
 the positive proof as hereafter directed. 
 
 Whatman's paper unwaxed may be prepared in the same manner as 
 the foregoing, and answers very well, but will not keep so long as the 
 
 * I have found a glass rod bent Into the form of a triangle as recommended by 
 Dr. Percy much better than any brush. 
 
 t I do not find this necessary. I simply hang the paper up to dry in a dark 
 room, and when dry put it into a portfolio. 
 
 B 3 
 
10 
 
 waxed paper. When unwaxed paper is used, it is better to add to each 
 litre of the iodizing solution the whites of two eggs beaten into a froth. 
 
 THIRD OPERATION. 
 
 EXPOSURE IN THE CAMERA. 
 
 Take especial care that the principal object in the picture is perfectly 
 in focus on the ground glass. This can frequently only be accomplished 
 by a sacrifice of the secondary parts of the picture. In a landscape it is 
 in general better to focus on the part intermediate between the fore and 
 back ground. 
 
 This part of the operation requires much judgment, and it is only 
 the artist, or person of good taste who can decide properly which part of 
 a view to sacrifice, and which part to bring out strongly. The time of 
 day at which to take a view, so as to have the light in such a position as 
 to produce the best efiect, is also a matter entirely dependent on the judg- 
 ment of the operator, and for which no directions can be given. 
 
 The time during which the paper should be exposed in the Camera, 
 can only be determined by experience, but on a proper regulation of this 
 time depends in a great measure the beauty of the picture.* 
 
 For a portrait, with a double combination lens capable of filling the 
 whole plate, (SJin. by ^in.) from thirty seconds to one minute in the 
 shade, and from ten to thirty seconds in the sun, are generally sufficient. 
 
 For landscapes, with a single lens, and a diaphragm of fifteen or 
 twenty millimetres diameter, the time of exposure should vary according 
 to the color of the objects, from thirty seconds to twenty minutes. Thus, 
 with an equal amount of light, a stone building would require an exposure 
 of thirty seconds, while a picture of forest trees could not be produced 
 in less than twenty minutes. 
 
 Heat, which much accelerates this part of the process when operating 
 by the humid method, has little or no effect when dry paper is employed. 
 
 * In another part of his work M. Le Gray says that you should impress on your 
 mind the fact that however short the exposure in the Camera may have been, you can 
 always get a good picture by leaving the proof a longer time in the gallic acid ; and by 
 way of example states that he took two pictures of the same object at the same time, 
 exposing one for twenty seconds, and the other for fifteen minutes, and that both turned 
 out equally good ; but the first required twenty-four hours in the gallic acid, and the 
 last only one. I have certainly never been able to obtain such results. 
 
11 
 
 After exposure in the camera, the image is scarcely visible, and is only 
 developed by the subsequent operation which may be deferred for as 
 much as a fortnight without risk of failure. 
 
 POURTH OPERATION. 
 
 DEVELOPMENT OF THE IMAGE 
 
 Solution of gallic acid is the agent employed to develop the image. 
 
 The solution should never be made till it is wanted, as an old solution 
 damages the white parts of the picture. It is therefore convenient to 
 weigh out a number of small parcels of gallic acid, each containing 
 0*50 centi-grammes.* When the solution is wanted, dissolve the contents 
 of one of these parcels in J of a litre of the water in which the wax 
 paper has been washed, and which contains precisely the quantity of 
 aceto-nitrate of silver necessary to give a good proof. When the gallic 
 acid is dissolved, plunge the proof into the solution, taking care that it 
 is completely covered and that there are no air bubbles. For this 
 purpose it is necessary to use an abundance of solution, as the wax paper 
 is not easily covered by a small quantity. 
 
 The solution here recommended contains quite sufficient acid com- 
 pletely to develop the image, and has this advantage over the saturated 
 solution formerly used, that it never deposits crystals in the body of the 
 paper, which the other is apt to do owing to the water evaporating while 
 the proof is in the solution. 
 
 Watch the development of the image closely, and as soon as it is 
 very vigorous, remove the proof from the solution and wash it in several 
 waters, rubbing it gently with the finger to remove any deposit that may 
 have taken place upon it. 
 
 The grey tint which the paper assumes in the gallic acid is of no 
 consequence, as it entirely disappears when the proof is examined by 
 transmitted light. 
 
 From the tint assumed by the proof in the gallic acid, you can 
 judge if the paper have been exposed for the right length of time in the 
 camera. 
 
 * This must mean 50 centigrammes, or 8grs. to 9 oz, of the wash water. 
 
1^ 
 
 If when examined by transmitted light, it appear of a greyish black 
 all over, or if the high lights (which ought to be of a dense black in the 
 negative) are no darker than the half tints, it is a sign that the proof 
 has been too long exposed. 
 
 If on the contrary, the high lights only become visible, and the 
 image soon ceases to become any more forcible, the proof has been 
 exposed for too short a time. 
 
 The time occupied in developing the image may be much shortened 
 by warming the solution of gallic acid. To do this, it is best to place 
 the dish containing the proof on a water bath heated to between 30^ 
 and 40° cent.* by means of a lamp. 
 
 If any oxide of silver deposit on the proof, it may be removed by 
 pouring on it some pure acetic acid, and rubbing it gently with a brush. 
 
 FIFTH OPERATION. 
 
 FIXING THE NEGATIVE. 
 
 Dissolve 100 grammes of hyposulphite of soda in 800 grammes of 
 water, t Pour this solution into a dish to the depth of 0*5 centimetre, $ 
 and plunge the proof completely into it, taking care to remove all air 
 bubbles. 
 
 Never put more than one proof at a time into this bath. 
 
 The hyposulphite dissolves all the salts of silver which are unacted 
 upon by the light, but has no effect on the gallate of silver which forms 
 the blacks of the picture. It requires from ten minutes to three quarters 
 of an hour to effect this solution. It is known to be complete when all 
 trace of yellow has disappeared from the paper, and when the white parts 
 of the proof examined by transmitted light are perfectly clear and trans- 
 parent. The paper should not be left in the bath longer than is absolutely 
 necessary, as a too prolonged action of the hyposulphite enfeebles the 
 blacks of the picture. 
 
 As soon as all the yellow iodide of silver is dissolved, remove the 
 
 * Between 86o and 104' Fahrenheit, 
 t Hyposulphite of soda loz., water 8oz. 
 t About 0-2 In, 
 
J 
 
 13 
 
 proof from the bath, wash it in several waters, and allow it to float in a 
 large basin of water for at least half an hour, to wash out all the hypo- 
 sulphite of soda, and then dry it between sheets of blotting paper. 
 
 The solution of hyposulphite of soda may after filtration be used 
 for fixing many other proofs. To restore the transparency which the 
 proof has lost by the action of the various solutions, it is only necessary 
 to warm it sufficiently to melt the wax which it contains. This may be 
 done, either by holding it to the fire, or by placing it between one or two 
 folds of paper and passing over it a warm iron. It is then ready for use, 
 and positives may be obtained from it as hereafter directed. 
 
 The modifications which the foregoing process has undergone consist 
 principally in various alterations in the iodizing solution. 
 
 The preparation of the rice water being a troublesome operation, 
 every one was anxious to avoid it if possible. 
 
 Le Vicomte Vigier was the first to point out that whey properly cla- 
 rified answered all the purpose of rice water, sugar of milk, &c. : he gives 
 the following directions. To a quart of whey add the whites of two eggs 
 beaten into a froth ; when well mixed, heat nearly to the boiling point. 
 The heat coagulates the albumen and clears the whey. Strain the liquid 
 first though a sieve and then through paper. 
 
 In a quart of whey thus prepared, dissolve of 
 
 The paper is soaked in this solution, and afterwards treated in every 
 respect according to M. Le Gray's directions. 
 
 The addition of bromide of potassium to the iodizing solution is a 
 great improvement, as it not only increases the sensibility of the paper, 
 but renders the whites of the picture much more pure and transparent. 
 
 The next modification of the wax paper process which I shall mention 
 is that of Mr. J. How. His directions are in all respects so good, that I 
 
 * Iodide of Potassium 
 
 400 grains. 
 
 Bromide of Potassium 
 Cyanide of Potassium 
 Fluoride of Potassium 
 
 60 „ 
 30 „ 
 23, „ 
 
 * These are as neaily as I can learn the original proportions which Le Vicomte 
 Vigier employed, but as he never published them, I cannot speak quite positiyely. 
 These proportions answer very well. 
 
14 
 
 shall quote them almost entire, as they were published in Notes and 
 Queries.— Page 93. No. 169. 
 
 "The easiest way of waxing the paper is to take an iron (those 
 termed box irons are cleanest and best for the purpose) moderately hot 
 in one hand, and pass it over the paper from side to side, following closely 
 after it with a piece of white wax, held in the other hand, until the whole 
 surface has been covered. By thus heating the paper, it readily imbibes 
 the wax, and becomes rapidly saturated with it. The first sheet being 
 finished, I place two more sheets upon it, and repeat the operation upon 
 the top one, (the intermediate sheet serving to absorb any excess of wax 
 that may remain) and so on until the number required is waxed. The 
 sheets which now form a compact mass are separated by passing the 
 iron over them ; then placed between folds of bibulous paper, and sub- 
 mitted to a further application of heat by the means just described, to 
 remove all superfluous wax and render them perfectly transparent." 
 
 To prepare the iodizing solution, " Take some milk quite fresh, and 
 add to it drop by drop glacial acetic acid, in about the proportion of 1 
 to 1.5 fluid drachms to the quart, keeping the mixture well stirred with a 
 glass rod all the time, which will separate the caseine ; then boil in a 
 porcelain vessel to throw down any caseine not previously coagulated, 
 and also to drive off as much as possible of the superfluous acid. After 
 boiling five or ten minutes, the liquor should be allowed to cool, and then 
 be strained through a hair seive or a piece of muslin : when quite cold 
 the chemicals are to be added. — They are the following : 
 
 Iodide of Potassium 385 grains 
 
 Bromide of Potassium 60 „ 
 
 Cyanide of Potassium 30 ,, 
 
 Fluoride of Potassium 20 „ 
 
 Chloride of Sodium in Crystals 10 ,, 
 
 Resublimed Iodine I J „ 
 
 The above are dissolved in 35 fluid ozs. of the strained liquid, and 
 after filtration through white blotting paper, the resulting fluid should be 
 of a bright lemon colour. The iodizing solution is now ready for use, 
 and may be preserved in well stopped bottles for any length of time.*' The 
 remainder of Mr. How's process is precisely similar to M. Le Gray's, 
 and need not therefore be repeated. 
 
IS 
 
 The method of waxing the paper here described is very superior to 
 the original method of M. Le Gray, as it is applicable to any sized sheet 
 of paper, consumes much less wax, and leaves so small a quantity for the 
 blotting paper to absorb, that very little comparatively is employed. 
 
 I have long been of opinion that in making the iodizing solution, 
 too little attention has been given to the combining proportions of the 
 various salts, and that better results could be obtained if more definite 
 proportions were employed. I therefore instituted a series of comparative 
 experiments between papers made according to the foregoing directions, 
 and some which I prepared in which the salts employed were in atomic 
 proportion, the result of which fully confirmed my expectation. I 
 first satisfied myself that the three essential salts in the solution were 
 an iodide, a bromide, and a chloride, and that the others might be 
 omitted without affecting either the sensibility of the paper, or the 
 beauty of the tints obtained. The proportions which I find answer the 
 best are 4 atoms of iodide, 2 of bromide, and 1 of chloride. I make 
 use of whey prepared according to Mr. How's directions as a solvent. 
 If the milk be good this answers very well, but if poor, the addition 
 of some sugar of milk to the whey is an improvement. I usually employ 
 the following solution : — 
 
 Whey 1 quart Impl. 
 
 Sugar of Milk 100 grains. 
 
 Iodide of Potassium . . 400 grains. 
 
 Bromide of Potassium . 142 grains. 
 
 Chloride of Ammonium 33 grains, or Chloride of Sodium 36 grs. 
 
 Unless I suspect metallic spots in the paper, I use neither cyanide 
 of potassium nor free iodine. The small quantity of acetic acid left in 
 the whey liberates sufficient iodine to give a light violet colour to the 
 paper, which serves as a guide for the time of exposure to the sensitive 
 solution. I prefer iodizing in vacuo as recommended by Mr. J. Stewart, 
 and described at page 20. It gives a more equal coating to the paper 
 and seems also to prevent spotting ; the soaking is also effected in a 
 much shorter time. 
 
 To render the paper sensitive, I employ the same solution as 
 Le Gray, page 8, but applied to one side of the paper only ; this is best 
 done by carefully floating the sheet on the sensitive bath, taking care to 
 
16 
 
 have no air bubbles under it. It is then washed by floating in the same 
 manner on distilled water, and changing the water once or twice. 
 To develop, I use — 
 
 This is spread on a glass plate placed perfectly level, and the proof laid 
 face downwards upon it. I prefer the saturated solution of gallic acid, 
 and the addition of the somewhat large proportion of silver solution, as 
 it causes the development to be much more rapid, and is not so liable 
 to give a precipitate on the paper as those solutions in which the proof 
 must remain for a comparatively long time. 
 
 The following process was published by Mr. Crookes, in Notes and 
 Queries, No. 6. p. 443. After some preliminary observations he says : — 
 My method is a modification of Le Gray's process, in which the 
 pores of the paper are saturated with wax previous to the formation of 
 the sensitive surface. This is undoubtedly the best, both as regards the 
 brilliancy of the finished picture, and the ease and convenience of mani- 
 pulation ; but there are several circumstances which tend to impair the 
 beauty of the results, foremost of which may be mentioned the spots, one 
 or two being generally met with even on the best paper. By the follow- 
 ing slight modification I have succeded in removing the impurities which 
 cause the spots, and also diminishing the time of exposure in the camera." 
 
 After describing the waxing of the paper, Mr. Crookes thus pro- 
 ceeds : — 
 
 The next operation consists in iodizing the paper ; the bath is 
 composed of 
 
 Iodide of Potassium . . . . 1 oz. 
 
 Water 1 pint imp. 
 
 with the addition of as much free iodine as will give it a sherry colour. 
 This removes the iron and brass, of which the spots generally consist : it 
 will require renewing now and then. The sheets are to be completely 
 immersed in this bath, for at least two hours, taking care to avoid air 
 bubbles, and then hung up to dry : they will be of a deep purple colour, 
 
 Saturated Solution of Gallic Acid 
 Of the Sensitive Solution ...... 
 
 Distilled Water 
 
 J ounce. 
 J drachm. 
 J drachm. 
 
17 
 
 owing partly to the union of the iodine with the starch in the paper, and 
 will keep good for any length of time. 
 
 " The solution for rendering these iodized sheets sensitive, consists of 
 
 The marked side of the paper is to be laid carefully on this solution, 
 and kept there for about half a minute longer than is necessary to com- 
 pletely decolorize it, (from seven to ten minutes) and then floated in dis- 
 tilled water for a few minutes. It must then be dried between blotting 
 paper, and kept in perfect darkness in a portfolio until required } with 
 one washing it will not keep good longer than six days, but if washed 
 sufficiently, it will keep good for weeks.*' 
 
 " For developing the picture, I employ four parts of a nearly satu- 
 rated solution of gallic acid, and one part of the solution previously 
 employed for exciting the paper ; these are to be well mixed, and the 
 marked side of the paper floated on it. The picture will soon begin to 
 appear, and should be completely out in less than an hour, and before the 
 gallo-nitrate is decomposed ; it must then be washed, soaked in tolerably 
 strong hyposulphite of soda until all the yellow iodide is removed, 
 washed again several times and then dried, and either ironed over, or 
 held before the fire to melt the wax. The greatest care must be taken to 
 have the dish to contain the gallo-nitrate perfectly clean ; it ought to be 
 rubbed with strong nitric acid every now and then, to remove the stains 
 from a previous operation ; unless this precaution be taken to avoid the 
 presence of dirt, the picture will be covered with stains, similar to mar- 
 bling in bookbinding. The gallic acid and nitrate of silver must also be 
 filtered before mixing.'* 
 
 I should be inclined to think from some expressions in this commu- 
 nication, that Mr. Crookes had never fairly tried Le Gray's* process; 
 had he done so, he would not have spoken of spots occurring on paper 
 prepared by that method. The cyanide of potassium, and free iodine, 
 recommended by Le Gray, remove metallic spots at least as effectually 
 as the free iodine in Mr. Crookes' process. I cannot agree with Mr. 
 Crookes in considering that his paper is more sensitive than Le Gray's ; 
 indeed, I have found quite the reverse to be the case. The very deep 
 
 Nitrate of Silver. . 
 Glacial Acetic Acid 
 Water 
 
 15 grains 
 15 grains 
 1 oz. 
 
18 
 
 colour given to the paper, is a disadvantage in this process, as it necessi- 
 tates a much longer exposure to the sensitive solution, than when only of 
 the light violet colour originally recommended. The saving of all the 
 trouble of making rice water or whey, seems at first sight a great point 
 gained, but a comparison of the results will, I think, shew that it is after 
 all, trouble well bestowed ; the depth of the black, and perfection of the 
 middle tints, more particularly in views comprehending objects at very 
 different distances, being so much greater when the original solution is 
 employed. I have never been able, by this process, to obtain first 
 rate results, excepting where little variety of light and shade are to be 
 represented. 
 
 NEGATIVES ON UNWAXED PAPER. 
 
 These papers are mostly used wet, and have not therefore the advan- 
 tage of keeping for any time. Le Gray gives the following directions in 
 the work already referred to : 
 
 The paper is iodized in precisely the same manner as the waxed 
 paper, the iodizing solution being made in the same way, only with the 
 addition of the whites of two eggs to each litre of solution. 
 
 To render the paper sensitive, pour some freshly filtered solution of 
 acetonitrate of silver of the strength before recommended into a shallow 
 porcelain dish, or on to a piece of plate glass placed quite horizontal ; 
 take a sheet of iodized paper by two corners and drop it with one side 
 only on the acetonitrate, raise and lower it several times so as to remove 
 all air bubbles from the under surface. To avoid soiling the fingers, use 
 either an ivory spatula to place under the corner of the paper, between 
 which and the finger the sheet is to be supported, or else take hold of 
 the corners with two pair of forceps made of horn or bone. Be careful 
 to prevent any of the solution of aceto-nitrate from getting on the back 
 of the paper, as it causes inequalities in the sensibility, and consequently 
 stains on the picture. Let the paper remain on the solution until the 
 sensitive coating is completely formed, which will take from one to five 
 minutes, according to the temperature and the quality of the paper — 
 English paper taking more time than French. Place the paper thus 
 prepared quite wet upon a slate on which you have previously laid a 
 sheet of blotting paper soaked in water. Slate is preferable to all other 
 
19 
 
 materials for this purpose, as it preserves the moisture longer ; the paper 
 placed under the sensitive sheet should be very clean and free from all 
 stains of iron. Always keep the slate inclined towards that edge which 
 is to be lowest in the camera. If this precaution be neglected, the 
 liquid which collects at the lower edge will run back over the surface 
 of the paper and produce stains. Paper thus stretched upon a slate will 
 remain for three or four hours without becoming detatched. If the 
 paper is to be kept longer before it is exposed in the camera, soak the under 
 sheet in a weak solution of gum arable, which retains the moisture longer 
 and is more sticky. If it be preferred, the moist paper may be placed 
 between two flat glasses in the camera.* Great care must be taken to 
 have these glasses perfectly clean and free from scratches. For cleaning 
 both these glasses and the dishes, there is nothing so good as Papier 
 Joseph ; it is very superior to linen, as it absorbs both the moisture and 
 impurities much more perfectly. It should not be spared, as it is better 
 to use a sheet too much than to be uncertain of the cleanness of your 
 apparatus. 
 
 When the under sheet of paper adheres well to the slate it should 
 not be changed for every proof, but simply be wetted with some fresh 
 water before applying a new sheet of sensitive paper. The remainder 
 of the process is precisely similar to that with wax paper. 
 
 The following letter to Sir J. Herschel, which appeared in the 
 " Athenseum," IS^o. 1311, p. 1363, will be read with interest by all ama- 
 teurs of Photography, as giving the results of an experiment new to the 
 
 " Pau Pyrenees. 
 
 " My dear Herschel, — Thanks to the valuable indications of Prof. 
 Regnault, of the Institute^ I have been enabled to produce, what appear 
 to me, most satisfactory results in Photographic Landscapes on Paper, 
 In this remote corner (so deficient in resources for experiment) I 
 feel that I am but very partially acquainted with the results obtained and 
 the progress making in the great centres, Paris and London ; but I think 
 
 * When two glasses are made use of, the paper must be pressed between blotting 
 paper before being placed between them. If it be put in quite wet, the moisture is 
 spread unequally over the surface and causes irregularities in the sensibility of the 
 paper. 
 
20 
 
 that, in detailing the simple process and manipulation I now adopt, indi- 
 cations of some value, and suggestive of further improvement to fellow- 
 labourers in the art may be found ; and if you are of the same opinion, 
 you will perhaps facilitate the communication of these details to our 
 photographers at home. 
 
 ^^The following observations are confined to negative paper pro- 
 cesses, divisible into two— the wet and the dry. The solutions I employ 
 for both these processes are identical, and are as follows :— 
 
 " Solution of Iodide of Potassium, of the strength of 5 parts of 
 iodide to 100 pure water. 
 
 *^ Solution of Aceto-Nitrate of Silver, in the following proportions : 
 15 parts of nitrate of silver ; 20 of glacial acetic acid ; 150 of distilled 
 water. 
 
 Solution of Gallic Acid, for developing, a saturated solution. 
 
 " Solution of Hyposulphite of Soda ; of the strength of 1 part hypo, 
 of soda to from 6 to 8 parts of water. 
 
 " The solutions employed are thus reduced to their simplest possible 
 expression, for it will be observed that in iodizing I employ reither rice- 
 water, sugar of milk, fluoride, cyanide, nor free iodine, &c. ; but a 
 simple solution of iodide of potassium (the strength of this solution is a 
 question of considerable importance, not yet, I think, sufficiently inves- 
 tigated). 
 
 " For both the wet and the dry processes I iodize my paper as fol- 
 lows :— In a tray containing the above solution I plunge, one by one, as 
 many sheets of paper (twenty, thirty, fifty, &c.) as are likely to be re- 
 quired for some time. This is done in two or three minutes. I then 
 roll up loosely the whole bundle of sheets, while in the bath ; and picking 
 up the roll by the ends, drop it into a cylindrical glass vessel with a foot 
 to it, and pour the solution therein, enough to cover the roll completely 
 (in case it should float up above the surface of the solution, a little piece 
 of glass may be pushed down to rest across the roll of paper and prevent 
 its rising). The vessel with the roll of paper is placed under the receiver 
 of an air-pump and the air exhausted ; this is accomplished in a very 
 few minutes, and the paper may then be left five or six minutes in the 
 vacuum. Should the glass be too high, (the paper being in large sheets) 
 to be inserted under a pneumatic pump receiver, a stifi* lid lined with 
 India-rubber, with a valve in the centre communicating by a tube with a 
 
21 
 
 common direct- action air-pump may be employed with equal success. 
 After the paper is thus soaked in vacuo it is removed, and the roll drop- 
 ped back into the tray with the solution, and then sheet by sheet picked 
 off and hung up to dry, when, as with all other iodized paper, it will 
 keep for an indefinite time. 
 
 " I cannot say that I fully understand the rationale of the action 
 of the air-pump,* but several valuable advantages are obtained by its use : 
 — 1st. The paper is thoroughly iodized, and with an equality through- 
 out that no amount of soaking procures, for no two sheets of paper are 
 alike, or even one, perfect throughout in texture ; and air bulbs are im- 
 possible. 2nd. — The operation is accomplished in a quarter of an hour, 
 which generally employs one, two, or more hours. 3rd. — To this do I 
 chiefly attribute the fact that my paper is never solarized even in the 
 brightest sun; and that it will bear whatever amoant of exposure is 
 necessary for the deepest and most impenetrable shadows in the view, 
 without injury to the bright lights. 
 
 " Wef Process. — To begin with the wet process. Having prepared 
 the above solution of aceto-nitrate of silver, float a sheet of the iodized 
 paper upon the surface of this sensitive bath, leaving it there for about 
 ten minutes. During this interval, having placed the glass or slate of 
 your slider quite level, dip a sheet of thick clean white printing (unsized) 
 paper in water, and lay it on the glass or slate as a wet lining to receive 
 the sensitive sheet. An expert manipulator may then, removing the 
 sensitive sheet from the bath, extend it (sensitive side uppermost) on 
 this wet paper lining, without allowing any air globules to intervene. — 
 But it is diflicult, and a very simple and most effectual mode of avoiding 
 air globules, particularly in handling very large sheets, is as follows^ — 
 Pour a thin layer of water (just sufficient not to flow over the sides) upon 
 the lining paper, after you have extended it on your glass or slate, and 
 then lay down your sensitive paper gently and by degrees, and floating 
 as it were on this layer of water ; and when extended, taking the glass 
 and papers between the finger and thumb, by an upper corner, to prevent 
 their slipping, tilt it gently to allow the interposed water to flow off by 
 the bottom, which will leave the two sheets of paper adhering perfectly 
 and closely, without the slightest chance of air-bubbles it may then 
 
 * The use of the air pump in soaking iodized paper, was first proposed by Mr. R. 
 Murray some years ago, but the experiments were never carried out. 
 
22 
 
 be left for a minute or two, standing upright in the same position, to 
 allow every drop of water to escape ; so that when laid flat again or 
 placed in the slider none may return back and stain the paper. Of 
 course, the sensitive side of the sheet is thus left exposed to the unin- 
 terrupted action of the lens, no protecting plate of glass being interposed 
 — and even in this dry and warm climate I find the humidity and the 
 attendant sensitiveness fully preserved for a couple of hours. 
 
 To develop views thus taken the ordinary saturated solution of 
 gallic acid is employed, never requiring the addition of nitrate of silver; 
 thus preserving the perfect purity and varied modulation of the tints. 
 The fixing is accomplished as usual with hyposulphite of soda, and the 
 negative finally waxed. 
 
 " Dry Process, — In preparing sheets for use when dry for travelling, 
 &c., I have discarded the use of previously waxed paper, — thus getting 
 rid of a troublesome operation, — and proceed as follows. — Taking a sheet 
 of my iodized paper, in place of floating it (as for the wet process) on 
 the sensitive bath, I plunge it fairly into the bath, where it is left to soak 
 for five or six minutes — then removing it, wash it for about twenty 
 minutes, in a bath, or even two, of distilled water to remove the excess 
 of nitrate of silver, and then hang it up to dry (in lieu of drying it with 
 blotting paper). — Paper thus prepared possesses a greater degree of 
 sensitiveness than waxed paper, and preserves its sensitiveness, not so 
 long as waxed paper, but sufficiently long for all practical purposes, say 
 thirty hours, and even more. The English manufactured paper is far 
 superior for this purpose to the French. To develop these views, a few 
 drops of the solution of nitrate of silver are required in the gallic acid 
 bath. They are then finally fixed and waxed as usual. 
 
 " These processes appear to me to be reduced to nearly as great a 
 degree of simplicity as possible. I am never troubled with stains or 
 spots, and there is a regularity and certainty in the results that are very 
 satisfactory. You will have observed, too, how perfectly the aerial 
 perspective and gradation of tints are preserved — as also how well the 
 deepest shadows are penetrated and developed — speaking, in fact, as they 
 do to the eye itself in nature. In exposing for landscape, I throw aside 
 all consideration of the bright lights, and limit the time with reference 
 entirely to the dark and feebly-lighted parts of the view; with a 
 3J-inch lens, the time of exposure has thus varied from ten minutes 
 
23 
 
 to an hour and a half, and the action appears to me never to have 
 ceased. 
 
 " The influence of the air-pump in this appears to me very sensible, 
 and deserving of further examination and extension. I purpose not 
 only iodizing, but rendering the paper sensitive with the action of the 
 air-pump, by perhaps suspending the sheet after immersion in the 
 nitrate bath under the receiver of the air-pump for a few minutes, before 
 exposure in the camera, or by some other manoeuvre having the same 
 object in view. 
 
 * " I should add, that I have chiefly employed Canson*s French paper 
 in iodizing with the aid of the pump. Few of the English manufactured 
 papers are sufiiciently tenacious in their sizing to resist the action of 
 the pump, but they may easily be made so ; and were, in short, the 
 English paper, so far superior in quality 'to the French, only better sized, 
 that it is with glue less easily soluble, even though more impure, there 
 is scarcely any limit to the beauty of the views that might be produced. 
 
 " There are more minor details that might be given ; but 1 fear re- 
 peating many a ' twice-told tale,' acquainted so little as I am with what 
 is doing ; — the preceding, however, may have some interest, and whatever 
 is of value is entirely due to our friend M. Regnault, ever so generously 
 ready as well as able to aid and encourage one's efforts. 
 
 " Ever yours, John Stewart." 
 
 The pictures lately exhibited by Mr. Stewart, at the Society of Arts, 
 fully bear out all that he says of them ; the effects of distance, and the 
 varieties of light and shade, being more beautifully preserved than in any 
 photographs I have yet seen. How much of this perfection is due to 
 the intrinsic merit of the process, how much to Mr. Stewart's skill as 
 an operator, and how much to the light he enjoyed in the Pyrenees, are 
 questions which it will require some time and many experiments to 
 answer. 
 
 On one point, no one in England will be inclined to agree with 
 him, viz : — That thirty hours is quite long enough for paper to keep. 
 Even if fine weather could be reckoned on, all must allow, that the less 
 
 * Mr. Stewart's remarks respecting the Paper appear rather at variance, and it 
 is diflacult to say which he uses, French or English, 
 
24 
 
 you have to carry, if going any distance, the better, and consequently 
 that a portfolio of sensitive paper which will keep for six weeks, is 
 better than one of simply iodized paper, together with a box full of bot- 
 tles and dishes. But in this country, where though you prepare paper 
 on a very fine night, you may have a week of wet or foggy weather suc- 
 ceeding it, paper which will only keep thirty hours, is no better, indeed 
 not so good, as that which will keep but three or four, such as the wet 
 paper before mentioned. 
 
 NEGATIVE ALBUMENIZED PAPER. 
 
 With the exception of the wax paper process, I know none which 
 yields so good results as that on albumenized paper, the albumen prevent- 
 ing the texture of the paper from interfering with the perfection of the 
 detail, as it undoubtedly does, when neither wax or albumen are employed. 
 
 Le Gray's directions for this process are the best I have yet met 
 with. They are as follows : — 
 
 In the whites of ten eggs, dissolve — 
 
 D Iodide of Potassium 4 grammes cent. 
 
 Bromide of Ammonium . . 0 ,, 50 „ 
 
 Chloride of Sodium 0 „ 50 ,, 
 
 Beat the mixture in a porcelain basin with a wooden fork till it becomes 
 a thick white froth. Let it stand for a night, and decant the clear liquid 
 which has subsided. Pour this liquid into a flat dish placed perfectly 
 horizontal, taking care to remove all froth. Take a sheet of paper by 
 two corners, and place it with one side only on the solution, beginning 
 with the edge opposite to that 
 by which you hold it, and letting 
 it fall at a right angle on the sur- 
 face of the liquid so as to push 
 out all air bubbles. The man- 
 ner of doing this will be best i 
 understood by an inspection of — 7 ^ 
 the diagram No. 1. 
 
 The same manner of pro- 
 ceeding is to be adopted when- 
 ever paper is directed to be floated on a solution. 
 
25 
 
 It is better to place a light before you, so that you may see all air 
 bubbles through the paper. 
 
 Let the sheet remain on the solution for two or three minutes, then 
 take it by one corner and remove it gently, but without stopping, and 
 hang it up by the corner to dry. 
 
 Having prepared and dried as many sheets as you require, place 
 them one on the other between two sheets of very smooth white paper, 
 and pass over them a very hot iron, removing one sheet every time you 
 pass the iron over them. This will render the albumen insoluble. The 
 iron should be as hot as is possible without scorching the paper. 
 
 This paper is to be floated on the aceto-nitrate of silver precisely 
 in the same manner as it was originally placed on the albumen. The 
 solution of aceto-nitrate in this process should be made without the 
 addition of animal charcoal, as that in which this body is employed seems 
 to dissolve the albumen. The pictures are developed and fixed precisely 
 in the same manner as those on waxed paper. 
 
 I think it is better to float the paper on the developing solution, than 
 to plunge it in as here directed. 
 
 The following paper employed at the Royal Observatory, Greenwich, 
 for the registration of meteorological observations, also gives very good 
 results in the camera, but from the large quantity of bromide of potassium 
 employed, it is more particularly adapted for use by artificial light. It 
 may be used for taking positives by the light of a camphine lamp. 
 
 To a filtered solution of 4 grains of isinglass in 1 oz. of boiling 
 distilled water, add 12 grs. of bromide and 8 grs. of iodide of potassium. 
 The solution, either hot or cold, is applied to one side of the paper in 
 such quantity as to wet it thoroughly but not to run off ; the paper is 
 then quickly dried at the fire, and may be preserved in a dry place. It 
 is excited by solution of nitrate of silver, 50 grs. to the ounce of distilled 
 water, and the image developed by a saturated solution of gallic acid to 
 which a few drops of acetic acid have been added. It is subsequently 
 washed and fixed in the usual way. 
 
 Proofs on unwaxed paper require to be waxed before good positives 
 can be obtained from them. This operation is exactly the same as that 
 of waxing paper already described, the mode detailed by Mr. How being 
 by far the best. 
 
 C 
 
It will be observed that in almost all these processes the strength of 
 the sensitive solution is the same, however much that of the iodizing 
 solution may vary. The reason of this is that the precise strength of 
 this solution is quite immaterial, provided it contain enough silver to 
 decompose all the salts contained in the paper, all excess being removed 
 by washing. When the solution becomes so weak as no longer to effect 
 this decomposition, it must be renewed, as any undecomposed iodide, or 
 bromide of potassium, materially interferes with the action of the light 
 on the silver salts. 
 
 In the Appendix to his last work, Le Gray gives the two following 
 processes by which he says very beautiful results are obtained by a 
 practised hand ; but he cautions beginners against attempting them, as 
 unless the operator be accustomed to the necessary manipulations, 
 failure is pretty sure to follow. 
 
 NEGATIVE GELATINE PAPER. 
 
 E Dissolve 25 grammes of isinglass in a litre of distilled water, 
 heating it on a water bath. 
 F 
 
 Take of The above Solution, still hot 365 grammes. 
 
 Iodide of Potassium 13 ,, 
 
 Bromide of Potassium 4 
 
 Chloride of Sodium 2 „ 
 
 When the salts are dissolved filter through fine linen. Pour the solution 
 while hot into a dish, and plunge your paper sheet by sheet into it, 
 taking care to remove all air bubbles. Let the paper remain for a 
 quarter of an hour in the bath, and hang it up to dry. 
 
 The remainder of the process is precisely the same as that described 
 at page 8 for giving sensibility, &c., to wax paper. 
 
 The iodizing solution may be kept and employed to the last drop ; 
 it only requires to be warmed and filtered immediately before it is again 
 used. This process gives exceedingly delicate and harmonious proofs j 
 it should be employed principally for subjects in which there are very 
 strong contrasts of light and shade, as by it, the gradations of tone are 
 better preserved than by those processes which give very intense blacks. 
 
27 
 
 ALCOHOLIC SOLUTIONS FOR NEGATIVES. 
 
 No. 1 Alcohol of 36° 1000 grammes. 
 
 Collodion 10 
 
 Iodide of Potassium 10 
 
 Cyanide ditto 1 
 
 Or, 
 
 No. 2 Alcohol of 36° 1000 grammes. 
 
 Camphor 15 „ 
 
 Solution of Lac in Spirit 5 „ 
 
 Iodide of Potassium 8 
 
 Cyanide ditto 2 
 
 Fluoride ditto 2 ,, 
 
 The advantage of these solutions is, that the whole of the paper we wish 
 to prepare can be put at once into the bath, as the alcohol penetrates 
 the mass with the greatest facility. The salts and resins should be pow- 
 dered and put into the alcohol in a stoppered bottle where they should 
 be left for two or three days, the bottle being frequently shaken. If at 
 the end of this time anything remains undissolved, the solution should be 
 filtered thi'ough blotting paper. Place the paper and solution in a pan, 
 which can be closed by a glass plate to prevent evaporation, and shake 
 it to make the alcohol penetrate the paper. After a quarter of an hour, 
 remove the paper and allow it to drain for a minute or two into the 
 pan ; then pierce through the corner of the whole mass with a silver 
 needle, and draw a string through it which you can suspend across the 
 room. Separate the sheets on the string and allow them to dry. In 
 this manner a great many sheets may be prepared in a very short time. 
 This paper will keep for a very long time. The remainder of the process 
 is the same as for waxed paper. M. Le Gray does not state the strength 
 of either the collodion or the solution of lac in spirit. 
 
28 
 
 NOTES TO THE NEGATIVE PROCESSES. 
 
 A Rice 3500 grs., (7oz.,2drachms., 20grs.), isinglass 350 grs., water 3 qts. I find 
 the following the best way of proceeding. Put the rice and isinglass into the cold 
 water, then place the whole on the fire until it boils. When it has boiled gently for 
 about half-a-minute, remove it from the fire and strain at once through a sieve. When 
 the liquor is cold it must be again strained, either through a very fine cloth, or through 
 paper. The isinglass, although useful in making the solution take to the paper, 
 may be omitted without afi'ecting the results of the process, and unless you are going 
 to use up all the solution in a very short time it is better to do so, as the isinglass soon 
 becomes putrid, while the solution prepared without it will keep for many months quit© 
 «weet. 
 
 B Sugar of Milk 393*78 grains. 
 
 The fluoride of potassium may I think, be omitted. I have never found it make 
 the slightest difl'erence in the result. The cyanide is useful, as it removes the spots in 
 the paper caused by the presence of metallic oxides, principally oxide of copper. 
 
 Iodide of Potassium. . , 
 Cyanide of Potassium 
 Fluoride of Potassium 
 Rice Water 
 
 131-26 „ 
 7.00 „ 
 4-37 „ 
 
 C 
 
 Nitrate of Silver. . . . 
 
 Glacial Acetic Acid 
 
 308*64 grains. 
 370-36 „ 
 123-45 „ 
 
 Animal Charcoal 
 Distilled Water . 
 
 About 10'5oz. 
 
 D 
 
 Whites of ten Eggs 
 Iodide of Potassium . 
 Bromide of Potassium, 
 Chloride of Potassium. 
 
 62 
 8 
 8 
 
 grains. 
 
 Isinglass 
 Water . . 
 
 465 graina 
 I quart. 
 
 r 
 
 Warm Solution of Isinglass 
 
 Iodide of Potassium 
 
 Bromide of Potassium . . . 
 Chloride of Sodium 
 
 13 f. oz. 
 200 graing. 
 
 31 „ 
 
PHOTOGRAPHY ON GLASS. 
 
 NEGATIVES BY COLLODION, &c. 
 
 Much discussion has recently taken place, as to who first proposed 
 the use of Collodion as a substance upon which photographs might be 
 obtained. The question who first suggested its use ? is more easily 
 asked than answered. I myself heard its use proposed by a friend, in 
 1847, almost immediately after Professor Schoenbein had announced 
 that rather bad gun cotton would dissolve in ether ; and before collodion 
 had come into use for surgical purposes. It is however easier to say 
 who first published any account of the method of using it. This was 
 undoubtedly Le Gray, in the Appendix to his work, " Traite Pratique 
 de Photographic sur Papier and sur Verre," published in June 1850 ; a 
 translation of which, by Mr. Cousens, was published a few weeks after- 
 wards, by Messrs. T. & R. Willats. The Appendix seems to have been 
 most curiously overlooked by most : in it he says, " I am now making 
 use of the following process on Glass: — Fluoride of Potassium or 
 Sodium is dissolved in alcohol of 40°, mixed with sulphuric ether, and 
 then saturated with collodion. I act on this with aceto-nitrate of silver, 
 and I obtain a picture in 20 seconds, in the shade; I develop the 
 image by a solution of protosulphate of iron, and fix with hyposul- 
 phite of soda. By the use of ammonia and bromide of potassium, I get 
 gi'eat variety of sensibility. The application of the solution to the glass, 
 is extremely easy. I hope, by this means, to obtain portraits in 2 or 3 
 seconds." Although these are but vague directions, they are quite 
 enough to establish Le Gray's right to be considered the first who pub- 
 
30 
 
 lished the collodion process, as they contain all the essential points, viz : 
 the addition to collodion of an alcoholic solution of some salt, capable of 
 giving with nitrate of silver, a precipitate sensitive to light ; the redac- 
 tion of the solution to a proper consistence by ether ; and the spreading of 
 the liquid thus obtained, on glass plates. The substitution, by Mr. 
 Archer, of iodide of potassium, (a substance in constant use in photo- 
 graphy) for the fluoride or bromide of Le Gray, can only be regarded as 
 an improvement on a process already before the public. Mr. Archer, 
 in his late letter, claiming to be the originator of the Collodion Process, 
 says that if Le Gray tried experiments on collodion in 1849, he did not 
 give the public the advantage of following him, and that in his work of 
 1850, the subject is dismissed in three or four lines. Though Mr. 
 Archer's communication to "The Chemist,'' extends to a much greater 
 length, does he really give the public more information about his process, 
 than Le Gray does concerning his ? The public may judge of this, by 
 perusing the following extract from "The Chemist'' of Februaiy 18th, 
 1851: 
 
 The imperfections in paper photography, arising from the uneven 
 texture of the material, however much care may be taken in the manu- 
 facture of it, and which from its nature, being a fibrous substance, cannot, 
 I believe, be overcome, has induced me to lay it aside and endeavour to 
 find some other substance more applicable, and meeting the necessary 
 conditions required of it, such as fineness of surface, transparency, and 
 ease of manipulation. 
 
 " A layer of albumen on glass answers many of these conditions, 
 producing a fine transparent film, but it is difiicult to obtain an even 
 coating on the glass plate ; it requires careful drying, and is so extremely 
 delicate when damp, that it will not bear the slightest handling ; besides 
 these objections, the necessity of having a large stock of glass when a 
 number of pictures are to be taken, is much against its general use. My 
 endeavour, therefore, has been to overcome these difficulties ; and I find, 
 from numerous trials, that collodion, when well prepared, is admirably 
 adapted for photographic purposes as a substitute for paper. It presents 
 a perfectly transparent and even surface when poured on glass, and being 
 in , some measure tough and elastic, will, when damp, bear handling in 
 saveral stages of the process. 
 
 " I will now give a short outline of my mode of using it. The first 
 
31 
 
 Step in the process is to prepare the solution of collodion. There are 
 several ways of doing this, but I will briefly allude to two. 
 
 Pour a quantity (say 1 oz.) of collodion into a bottle containing dry 
 iodide of silver to settle. The collodion will, in this way, take up a cer- 
 tain quantity of the silver salt, and become opaque ; it should then be 
 transferred to another bottle containing iodide of potassium, to be again 
 well shaken up until the iodide of silver is entirely dissolved, and the 
 solution becomes perfectly transparent. 
 
 " Or this : — To a solution of iodide of potassium in spirits of wine, 
 add a small quantity of iodide of silver sufficient to saturate the iodide 
 of potassium; let, however, the latter salt be in excess.* Add a small 
 quantity of this solution to the collodion, between five and ten grs. by 
 measure to 1 oz. of collodion will be sufficient, and if any of the iodide 
 of silver should precipitate, a small quantity of iodide of potassium must 
 be added to dissolve it. In this way, or by the former mode, the collodion 
 may be prepared. 
 
 " The next step is to spread this solution evenly on a plate of glass. 
 This can be done by pouring a sufficient quantity on the glass to run in a 
 body freely. When it has entirely covered the glass plate, let the supei*- 
 abundance be drained off at one corner into the bottle again ; this 
 operation cannot be done too quickly, for the ether rapidly evaporating 
 would prevent the collodion running evenly over the surface of the plate, 
 and from its becoming too thick. 
 
 " The plate is now plunged into a bath of nitrate of silver, allowed to 
 remain there for a few seconds, and then washed in water. (This washing 
 is intended to remove all the ether from the surface of the collodion, 
 which, if allowed to remain, would cause an unevenness in the sensitive- 
 ness of the surface, producing streaks or spots.) Immediately after 
 washing, it may be exposed to the action of light for the time necessary 
 to obtain a picture. This picture can be developed either by gallic or 
 pyro- gallic acid. If the latter acid be used, a few precautions are 
 necessary, to which I will allude presently. The former acid may be 
 used as a bath, in the ordinary way. After the picture is developed, the 
 film of Collodion should be loosened from the edges of the glass plate 
 with a flat glass rod. By doing this, it will easily separate from the plate 
 and can be allowed to float freely in the water bath, previous to being 
 * If the iodide of potassium be saturated, how can it be in excess ? 
 
32 
 
 placed in the bath of hyposulphite of soda, and then again thoroughly 
 washed. 
 
 " The drawing can now be mounted on a plate of glass, and when dry 
 can be varnished, to protect it from injury. 
 
 " If thought more convenient (and, in fact, this mode is the best when 
 pyro-gallic acid is used), the film of collodion, after being exposed to light 
 and the image developed, can be removed from the glass plate (leaving 
 the fixing and final washing to be done at leisure) by rolling it up on 
 a glass rod, thus: — Take a sheet of ordinary white wrapping or thick 
 blotting paper (if glazed it will be better), about the same breadth, and 
 about one third longer than the drawing to be removed, soak it in water, 
 and place it with the glazed side in contact with the surface of collodion. 
 Turn the end of the collodion picture over the edge of the paper lying 
 upon it, then place the glass rod just within the edge, and commence 
 rolling it upon the rod; with a little dexterity, this can be accomplished 
 without injuring the drawing. The cylinder thus formed, is easily re- 
 moved from the glass rod, and can be preserved for any length of time 
 in this state by being kept damp and away from the light, to be finally 
 fixed at some more convenient time. Thus one plate of glass will be 
 sufficient to make any number of drawings upon, the above operations 
 being repeated for each picture. 
 
 " The plate of glass should be rather larger than the drawings intended 
 to be made upon it, to allow for rough edges, &c. The back of the glass 
 may be ground to get the focus upon, and one side should be formed 
 into a kind of handle to prevent the hand of the operator being near the 
 solution when the glass is in use. 
 
 t6 Thirty grains of nitrate of silver to one ounce of water will be suffi- 
 cient for the nitrate of silver bath. 
 
 " Three grains of pyrogallic acid to one ounce of water, to which must 
 be added about one drachm of acetic acid. 
 
 " Between five and ten grains of nitrate of silver to one ounce of 
 water. 
 
 The two latter solutions are to be mixed in equal proportions when 
 a picture is to be developed. A wide -mouthed glass measure will be 
 necessary to hold this mixture. 
 
 I have found it convenient to have a trough made of gutta percha, 
 the two sides and bottom of which are about one-eighth inch high and 
 
33 
 
 just large enough to hold the glass plate. With this trough the mixed 
 solution can be poured rapidly over the plate, without fear of any being 
 thrown over the edges." 
 
 It will be observed that in this letter not a word is said of the method 
 of making collodion, or the strength of the solution to be employed ; 
 the quantity of iodide of potassium and silver is also left an open ques- 
 tion, so that beyond the use of the iodides of silver and potassium in 
 collodion, the public was left much where it was before, excepting that 
 its attention had been fairly drawn to the subject. Subsequent experience 
 has shewn that it is better to omit the iodide of silver, and add only the 
 alkaline iodide to the collodion, as that containing silver soon spoils, and 
 is never so tough as that prepared without it. Some operators indeed 
 still prefer collodion containing silver, I shall therefore in the following 
 section give one or two formulae for its preparation, 
 
 PREPARATION OF COLLODION. 
 
 The greater number of photographers prepare their collodion by 
 various slight modifications of a process first published by M. Mialhe, in 
 which cotton is acted on by a mixture of finely powdered nitre and com- 
 mon oil of vitriol 
 
 Mr. Mayall gives the following formula : — 
 
 Clean dry Cotton 80 grains. 
 
 Finely powdered and dry Nitrate of Potash . . 3 ojmces. 
 
 Mix the nitre intimately with the cotton in a basin, and pour upon it 
 3 f. ounces of strong sulphuric acid. Then, with two stout glass rods, 
 knead the cotton in the acid for about four minutes, or until the mass 
 begins to fume; then quickly plunge the whole into an excess of water, 
 and wash out all trace of acid and dry. This quantity of cotton is to 
 be dissolved in 1 pint of sulphuric ether for negatives, or 1 quart 
 for positives. To every pint of collodion add about 14 grains iodide of 
 silver, and 1 2 grains iodide of potassium. 
 
 Le Gray's directions for making the gun cotton differ but little from 
 these, but his method of iodizing being essentially different, I shall give 
 his process entire; — 
 
 " Dry Nitrate of Potash in fine powder 80 grammes. 
 Strong Sulphuric Acid (not fuming). . 120 „ 
 
 C 3 
 
34 
 
 Mix them well in a porcelain basin with a glass rod for about two 
 minutes, then add 4 grammes of cotton. Keep the cotton stirred in the 
 acid mixture for about ten minutes, then throw it into a large quantity of 
 water, and wash till not acid, first in common, and then in distilled 
 water. Press out the water with the hand, and afterwards between folds 
 of blotting paper j then spread it on paper, and let it dry by exposure to 
 the air, taking care to keep it free from dust. When quite dry put into 
 a stoppered bottle the following ingredients : — 
 
 Sulphuric Ether of 62'> 
 
 Alchohol of 36° 
 
 Gun Cotton 
 
 Liquid Ammonia 
 
 When the cotton is dissolved, add one gramme of iodide of ammonium. 
 When the solution is complete, filter it through fine linen into a dry 
 bottle. 
 
 Iodide of potassium may be substituted for iodide of ammonium, but 
 we must then add 10 centigrs. of pure iodine, and 2 drops of liquid 
 ammonia. 
 
 Dr Diamond, in No. 151, of Notes and Queries," recommends 
 the following process as yielding, in his opinion, a collodion very superior 
 to every other. 
 
 To prepare the gun cotton, Place 100 grains of clean cotton in a 
 large basin, and pour on it 1 J oz. of nitric acid previously mixed with 
 loz. of strong sulphuric acid. Knead it with glass rods during five 
 minutes, at the end of which time the cotton is to be plunged into cold 
 water and washed as long as any trace of acid remains. The most 
 convenient mode of drying it is to wring it in the folds of a towel, and 
 then pin it up in small fragments to allow the air to have free access 
 to it." 
 
 In these directions Dr. Diamond omits to mention the specific 
 gravity of the nitric acid to be employed, although upon it depends the 
 whole success of the operation. 
 
 This process is the one originally published by Mr. T. Taylor, in 
 the " Times," before Professor Schoenbein had made known his mode of 
 preparing gun cotton. Mr. Taylor, however, particularly mentioned 
 
 100 grammes. 
 25 „ 
 
 5 drops. 
 
35 
 
 that acid of sp. gr. 1500 must be employed, his purpose being to obtain 
 a cotton as powerfully explosive as possible. This cotton is, however, 
 insoluble in ether, and therefore quite unfit for making collodion. 
 I presume Dr. Diamond must mean to recommend acid of sp. gr. 1450, 
 as that is about the strength usually sold. This yields a soluble cotton, 
 but I have never yet succeeded by the use of nitric acid of any sp. gr. 
 in making really good collodion. 
 
 If Dr. Diamond pay but little attention to the sp. gr. of his acid, 
 it is not surprising that he finds it impossible to say precisely the proper 
 quantity of iodizing solution to be employed, as doubtless his collodion 
 is never twice exactly alike. If the collodion be of the same quality, 
 the quantity of iodide must always be the same. 
 
 Dr. D. proceeds. " To prepare the Collodion : — About 50 grains 
 of this cotton put into a pound of ether will dissolve and form collodion 
 of the required consistency. The ether used should be the common 
 rectified ether not washed ; and should the operator find he has obtained 
 an ether which will not dissolve the cotton, a portion of spirits of wine 
 may be added in a proportion not exceeding one-tenth of the ether. 
 This may be either allowed to subside or be strained off" immediately 
 through an old silk handkerchief, and is then in a fit state to iodize." 
 
 " To iodize the collodion dissolve 30 grs. of nitrate of silver and 30 grs. 
 of iodide of potassium, each in 4 oz. of water^ and mix the solutions ; 
 wash the precipitated iodide of silver frequently in distilled water, and 
 w^hen almost dry, place it in a bottle with I5 oz, of alcohol. Drop into 
 this mixture iodide of potassium till the iodide of silver is completely 
 dissolved, when it is fit for use. It is difficult to determine how much 
 of this solution should be added to the collodion, probably 10 or 12 
 drops to the ounce, but it should be added until the collodion, when 
 poured on a piece of glass and immersed in the bath of nitrate of silver, 
 assumes a semi-opaque, opal-like appearance. Should the collodion 
 then appear very turbid, a little spirit of wine may be added.*' 
 
 Various additions have been from time to time proposed to the 
 Ingredients here recommended, some for the purpose of rendering the 
 collodion more tough, and others for increasing its sensibility, thus Mr. 
 Fry recommends the addition to the iodized collodion of a piece of gutta 
 percha, the small quantity of which that dissolves, is said to render the 
 collodion much stronger. In a late No. of Notes and Queries," amber 
 
36 
 
 is recommended for the same purpose. Amongst the accelerating sub- 
 stances may be mentioned bromide of potassium, fluoride of potassium, 
 arsenious acid, and iodide or bromide of iron. None of those who re- 
 commend these substances, state the quantity in which they are to be 
 added ; I have myself found no advantage from their use for ordi- 
 nary purposes, but I am informed that for working by artificial light, 
 as in copying microscopic objects with a camphine lamp, the bromide of 
 iron is really useful. 
 
 The following process, (a slight modification of one with which I 
 was kindly favoured by Mr. R. Murray,) gives by far the best collodion 
 I have ever seen, being much more tough than those previously described, 
 and requiring about half the time of exposure in the camera : — 
 
 Mix in a wide-mouthed stoppered bottle, 
 
 Add to this mixture 30 grs. of Swedish filtering paper, (good tissue 
 paper made irom linen may be employed, but it is not so good,) put in 
 the stopper, and allow the paper to soak at least three hours : it may be 
 left for 12 or even 24 hours without danger. Pour off as much of the 
 acid as possible, plunge the paper into a large quantity of water, and 
 wash it till every trace of acid is removed, first in common and then in 
 distilled water ; then dry it by a gentle heat. 
 
 Dissolve 5 grs. of iodide of potassium in 2 drachms of spirit of 
 wine of 59 over proof, add to it 6 drachms of ether sp. gr. 0.738, and 
 lastly 6 grs. of prepared paper ; let the mixture stand, shaking it 
 occasionally for 12 hours, and then filter through fine linen, or better 
 still, through swansdown. Be careful to add the ether gradually to the 
 alcoholic solution of iodide of potassium, as if the latter be poured at 
 once into the ether, the salt will precipitate. Instead of the above, the 
 following solution is preferred by some : — 
 
 Iodide of potassium 5 grains, iodide of ammonium 3 grains, dissolve 
 in 4 oz. of spirits of wine, add IJ oz. of ether, and 12 grains of paper. 
 
 The ether here recommended is Howard's extra light ether, and is, 
 though so light, unwashed, it is the best that can be employed. Should 
 
 Nitrous Acid, sp. gr. 1460. 
 Sulphuric Acid, „ 1827 
 Nitric Acid, „ 1500 
 
 20 mins. 
 
 if. oz 
 i f. oz 
 
37 
 
 any one not be able to obtain it, common unwashed ether may be substi- 
 tuted, but less spirits of wine must be used. With ether of sp. gr. 0.740, 
 the iodide must be dissolved in 1| f. drachms of spirit, and 6^ f. drachms 
 of ether must be added. 
 
 The collodion may be made with still greater certainty by employing 
 absolute alcohol and dissolving the iodide in water, using one drop of 
 water for each grain of iodide ; this solution is mixed with the alcohol 
 and the ether poured into it. 
 
 The great advantage which paper possesses over cotton, is the facility 
 with which every trace of acid can be removed from it A much larger 
 quantity of it can also be employed, whereby great depth is given to the 
 blacks of the picture, and the middle tints are much more perfectly pre- 
 served. The film being so much thicker, is, of course, much Jess easily 
 injured. The iodide of silver formed on immersing the plate in the 
 nitrate of silver, is also much more perfectly adherent to the collodion, so 
 that you are never troubled with particles floating on the surface of the 
 solution, as is constantly the case when collodion prepared from cotton is 
 employed. 
 
 A skilful operator can work with the collodion thicker than is here 
 recommended, as much as 7 or 8 grs. of paper to the oz. being used by 
 some, it is however difficult to get an even film on the glass with such 
 thick collodion, and though greater depth of tone and increased solidity 
 are obtained, I think the proportions above directed are the best for 
 ordinary purposes. 
 
 MANNER OF COATING THE GLASS WITH COLLODION. 
 
 The edges of the glass plates being first ground, they must be ren- 
 dered perfectly clean and free from grease. For this purpose they may 
 be washed in solution of soda, or in liquid ammonia, and afterwards in 
 plenty of clean water, and dried with a cloth which must itself be cleansed 
 from grease by washing in a weak solution of soda, and afterwards in 
 clean water. 
 
 Le Gray recommends the use of spirits of wine holding a little fine 
 tripoli powder in suspension, which is to be applied with a bunch of 
 papier Joseph, and the plate then rubbed clean with some fresh pieces of 
 
38 
 
 paper. I have found nothing answer so well as infusion of galls, a liquid 
 constantly used by microscopists for removing grease from their slides. 
 However they may have originally been cleaned, the plates should imme- 
 diately before they are used be polished on a buff of velvet, or chamois 
 leather, similar to those used for polishing daguerreotype plates. 
 
 The plate being perfectly clean, take it by one corner in the right 
 hand, and with the left pour a good quantity of collodion on to its centre. 
 Spread this entirely over the glass by inclining it gently in every direc- 
 tion. Pour off the excess of collodion at the corner opposite to that by 
 which you hold it, bring the plate into an upright position, and draw 
 one edge of it along the mouth of the bottle; then immediately place it 
 perfectly horizontal, and give it a slight tremulous movement, which 
 completely removes all the streaky appearance from its surface. As 
 soon as the collodion begins to set, it is ready to be placed in the bath of 
 nitrate of silver. If the plate be too large to be held by one corner, some 
 other part of it must be supported. Nothing is better for this purpose 
 than the support directed by Le Gray, viz., a bottle with the top of 
 the cork rounded. On this you rest the centre of the plate, and holding 
 it by one corner you can readily ^ive it all the necessary motions. 
 
 GIVING SENSIBILITY TO THE PLATE. 
 
 The solution for this purpose is composed of : — 
 
 Nitrate of silver 300 grains 
 
 Distilled water 10 oz. 
 
 This solution is contained in a trough of glass or gutta perclia, rather 
 larger than the plate to be immersed, and about J or | of an inch wide, 
 placed in a sloping position. Into this the plate is to be plunged with 
 one uniform movement, as any stop produces lines across tlie collodion 
 surface. This immersion is best effected by placing the plate on a glass 
 dipper, made by cementing a slip of plate glass, about a J in. wide, on 
 the end of another slip of 8 or finches long, and I J or 2 inches wide. 
 The plate is laid with its uncoated surface on the long slip, and its 
 
39 
 
 lower edge resting on the cross slip; the position of the plate and 
 trough will be understood at once by an inspection of figure 2. The 
 plate will almost directly become coated 
 with a yellow iodide of silver. It must be 
 examined occasionally, and as soon as the 
 liquid remains in a uniform film over its 
 surface, it must be removed to the camera, 
 and exposed as rapidly as possible. It has 
 lately been recommended to add some alco- 
 hol to the solution of nitrate of silver, and it 
 seems certainly to give a more uniform coat- 
 ing to the plate. It is usual with the alcohol 
 to use rather a stronger solution ; the follow- 
 Fig. 2. ing are the proportions generally employed : 
 
 Nitrate of silver 400 grains. 
 
 Alcohol 4 f . drachms. 
 
 Distilled Water 10 f. oz. 
 
 It is said by some, that a new sensitive bath does not give a uniform 
 coating to the plate ; this they attribute to the nitrate of silver dis- 
 solving a small quantity of the iodide of silver at first formed, to prevent 
 which, they recommend that a little iodide of potassium should be added 
 to the nitrate of silver solution ; this precipitates a small portion of iodide 
 of silver, which is redissolved by the nitrate, and prevents its afterwards 
 attacking the coating on the plate ; should any iodide of silver remain 
 undissolved, it must be separated by filtration. I have never found this 
 part of the process necessary. 
 
 The plate being properly coated, it is removed from the bath, the 
 liquid allowed to drain off at one corner, and then placed in the camera 
 frame, which should be placed in an upright position, the edge of the 
 plate from which the solution has been drained being at the lower part 
 of the frame, as if placed in any other position, drops of solution which 
 have collected at that part will run over the surface of the plate and cause 
 stains. Two or three folds of blotting paper should be placed over the 
 back of the plate, before closing the door of the frame. Camera frames 
 for this process are best when lined entirely with glass ; at all events, the 
 part on which the plate rests should be made of that material. Should the 
 
40 
 
 operator be unable to obtain a glass frame, the best thing he can do is to 
 place small pieces of blotting paper over those parts of the frame on 
 which the plate is to rest, as wood is very apt to cause stains on its surface, 
 besides becoming very much spoiled by being kept constantly wet with 
 the moisture from the plate. 
 
 It is quite impossible to state precisely the length of time during 
 which the plate must be exposed in the camera, as it will vary with the 
 state of the light, and the construction of the lens. I may mention 
 however, that with a good double combination of 2 inches apperture, and 
 8 inches focal length, the day being moderately bright, a good portrait 
 may be obtained out of doors in the shade, in from 3 to 5 seconds. The 
 plate should always be exposed as soon as possible after it is rendered 
 sensitive, as its sensibility declines rapidly as it drys. Some have 
 recommended having a glass bath for the nitrate of silver fitted to the 
 back of the camera, and exposing the plate whilst in the solution, but 
 the action of the light is materially decreased by having to pass through 
 the side of the bath, and perhaps still more by the film of solution of 
 nitrate of silver, which stops many of the chemical rays. 
 
 The most common agent for this purpose is a solution of pyrogallic 
 acid, mixed with acetic acid. The precise strength of the solution de- 
 pends on the length of time which has been required to produce the 
 picture ; in general, a stronger solution being required as the intensity of 
 the light diminishes, and consequently the time of exposure increases. 
 The following is the solution generally employed : — 
 
 Pour about 2 drachms of this solution over the surface of the glass which 
 is kept gently agitated to prevent stains forming on the surface. After 
 about two seconds pour off the solution, and if the blacks have not a 
 decided and intense appearance, add to the solution three or four drops of 
 a solution of nitrate of silver of the strength of 30 grains to the oz., and 
 
 DEVELOPMENT OF THE PICTURE. 
 
 Pyrogallic Acid . . 
 Distilled Water . . , 
 Glacial Acetic A cid 
 
 3 grains. 
 
 2 f.oz. 
 
 1 f. drachm. 
 
41 
 
 again pour it on the plate. As soon as all the details of the picture are 
 well defined and the blacks very intense, which will generally be the 
 case in from ten to twenty seconds, pour off the solution and wash the 
 plate well by pouring water gently on to it, when it will be ready for 
 fixing. 
 
 I have found solution of pyrogallic acid of half the above strength 
 answer perfectly on a bright day, and indeed give better pictures than the 
 stronger solution. • 
 
 Various methods have been devised of applying the developing 
 solution, some operators preferring one, and some another. One of the 
 most convenient is to place the plate face upwards on a small glass tripod* 
 standing in the middle of a dish, and pour the developing solution rapidly 
 over it, any which may run over the edges being caught in the dish. 
 The plate can also be washed without removing it from the stand by 
 pouring water on to its centre and allowing it to flow over into the dish. 
 Mr. T. Ross recommends a trough of plate glass rather larger than the 
 plate, about 3-16ths of an inch deep, and having only three sides, the 
 open end being slightly raised by cementing a slip of glass under it. In 
 the inside of this trough are cemented two slips of thin microscopic glass, 
 on which the plate may rest so as not to come in contact with the bottom. 
 A small quantity of developing solution being poured into the trough, the 
 plate is laid face downwards on the slips of thin glass. Capillary attrac- 
 tion draws the liquid up between the plate and the bottom of the trough, 
 and thus a very small quantity of solution may be made to cover a com- 
 paratively large plate. By placing a sheet of white paper under the 
 trough the development can be watched without removing the plate. 
 When the development is complete the plate must be washed as before 
 directed. A saturated solution of gallic acid may be substituted for the 
 pyrogallic acid, but I do not think the results are so good. If this acid 
 is used it is better to plunge the plate completely into a bath of the solu- 
 tion in the same way as it is put into the bath of nitrate of silver. 
 Solutions of the protosalts of iron (principally the sulphate and nitrate) 
 are by some preferred to either gallic or pyrogallic acids. M. Le Gray 
 gives the following formula for the preparation of developing solution : — 
 
 * Should the operator not have a glass tripod, a small wine or liQueui glass answexi 
 the purpose very well, the plate being laid on the mouth of the glass* 
 
42 
 
 "* Distilled Water 600 grammes. 
 
 Proto Sulphate of Iron 50 
 
 Sulphuric Acid 10 drops. 
 
 Acetic Acid 10 grammes. 
 
 The plate is completely immersed in this bath, which will serve to 
 develop a great many pictures ; the development should be complete in 
 three or four seconds. Should the proof not be sufficiently vigorous when 
 withdrawn from this bath, it may be much improved by placing it in a 
 bath of gallic acid containing a small quantity of aceto-nitrate of silver.*' 
 The proto-nitrate of iron being chiefly used for the development of posi - 
 tive images, I shall give the formula for its preparation under that head. 
 
 M. Le Gray asserts that the tone of the picture thus obtained, is 
 more harmonious than that of those developed by pyrogallic acid, and 
 that the middle tints are better preserved ; I have not found this to be 
 the case, if good collodion be employed, moreover the blacks are never so 
 intense. 
 
 FIXING THE NEGATIVE. 
 
 This is done by pouring on to the surface of the plate a nearly satu- 
 rated solution of hyposulphite of soda, allowing it to remain until the 
 whole of the yellow iodide of silver is removed and the whites of the 
 picture appear perfectly transparent. If it be preferred, the plate may 
 be immersed in a bath of the fixing solution, but the film of collodion is 
 apt to become detached from the glass if it be too often completely im- 
 mersed in various solutions. Hyposulphite, which has been frequently 
 used, is preferred by some, as it is less likely to weaken the black parts of 
 the picture; it takes however a longer time to dissolve the iodide of 
 silver, and if the negative be really good and forcible, new hyposulphite 
 does it no injury. As soon as the solution of the iodide of silver is com- 
 plete, pour ofi" the hyposulphite and wash the plate well in water. After 
 a good quantity of water (say at least half a pint) has been poured over 
 
 * Distmed Water • 1 pint. 
 
 Protosulphate Iron 875 grs. 
 
 Sulphuric Acid 12 drops. 
 
 Acetic Acid 164 grs. 
 
43 
 
 the plate, it should be allowed to remain for an hour or two under as 
 much water as can be made to stand on its surface, the water being 
 changed frequently (say every ten minutes) during this time. This long 
 washing is particularly necessary with the paper collodion, as from its 
 greater body it retains the hyposulphite much more firmly than collodion 
 prepared from cotton. If the hyposulphite be not entirely removed, 
 after two or three days it crystalizes all over the plate, and completely 
 spoils the picture. After being well washed, the plate is placed in an 
 upright position with its lower edge resting on some blotting paper, and 
 allowed to dry spontaneously. 
 
 M. Le Gray recommends a solution of 2 grammes of persulphate of 
 iron in a litre of water instead of hyposulphite of soda for fixing the nega- 
 tive ; he admits, however, that it leaves the light parts of an opaque 
 yellow tint, which somewhat interferes with the subsequent printing pro- 
 cess ; nevertheless, he says that it increases the force of a feeble proof, 
 and enables you to print from it when you could not do so had it been 
 fixed by hyposulphite of soda. The solution should remain on the plate 
 about forty seconds, as too long an exposure completely removes the 
 image. I have not myself tried this mode of fixing, so can give no 
 opinion of its efficacy. 
 
 When the proof is perfectly dry, it must be varnished to prevent its 
 being injured in the printing process. Various varnishes may be used 
 for this purpose. The one I have found answer the best, is that made 
 by dissolving gum damma in turpentine : it should be of such a thick- 
 ness as to run readily over the plate. It is applied to the glass precisely 
 in the same manner as the collodion, the plate being previously heated 
 as hot as the hand can bear. Common mastic varnish reduced to about 
 half its ordinary thickness with turpentine may also be employed, but it 
 remains much longer sticky. White hard varnish thinned either with 
 turpentine or absolute alcohol, also answers very well. Some operators 
 employ pale laquer, which is a remarkably good and hard varnish, and 
 possesses the advantage of enabling you to print from the negative imme- 
 diately. It requires, however, considerable skill to use this varnish pro- 
 perly ; the plate must be made very hot and kept so after the varnish 
 has been applied until it is quite dry, otherwise it becomes opaque. I 
 have also sometimes found that it dissolves the picture completely ofi' 
 the glass. I have not yet been able to ascertain to what this is owing. 
 
44 
 
 Dr. Diamond gives the following receipt for a varnish which he strongly 
 recommends : — 
 
 Powder 2 drachms of amber, and macerate for 3 days in 2 oz. of 
 chloroform ; shake it often and filter it for use through thin blotting 
 paper. The chloroform dissolves a hard resin from the amber, and 
 leaves its bituminous components untouched. Another varnish may be 
 made by macerating amber in naptha or benzole ; it does not dry so 
 rapidly as the preceding, and has some colour ; but when large surfaces 
 are to be covered, it is from its comparative cheapness a desirable coating, 
 as it perfectly protects the picture." Dr. Diamond recommends the 
 broken mouth pieces of pipes for this purpose as they are generally made 
 of the finest and most transparent kind of amber. 
 
 If a negative appear very feeble after being fixed, it may often be 
 much improved by the action of a solution of corrosive sublimate. Dr. 
 Diamond recommends dissolving half an ounce of corrosive sublimate in 
 one ounce hydrochloric acid, and afterwards adding one ounce of water. 
 I have always employed a nearly saturated solution of corrosive subli- 
 mate in water as it has not so great a tendency to render the collodion 
 rotten. A small quantity of the solution being poured on to the plate 
 the blacks gradually become white, and a very agreeable positive is often 
 produced ; as soon as this is the case, wash the plate in water, and again 
 apply the solution of hyposulphite of soda ; almost immediately the color 
 is again changed to black, and generally far more intense than that of the 
 original picture ; it has now only to be well washed, dried and varnished, 
 as already described. 
 
 Instead of varnishing the collodion while on the glass, it may be 
 transferred to paper, and where easy package is an object, this is the 
 best method of proceeding. It is however a difficult and delicate 
 operation, and can only be performed with very good collodion. The 
 following directions from Le Gray's work are, I think, the best I have 
 Bften for this process. 
 
 " After the proof is fixed, place it in a bath of water acidulated with 
 acetic acid, and leave it until one corner of the collodion becomes 
 detached from the glass. Then allow a fine stream of water from a 
 small cock to flow between the collodion and the glass, by letting it fall 
 on the corner of the glass which is uncovered; this must be done 
 patiently and with great caution. When the water flows freely between 
 
45 
 
 the collodion and the glass, place the plate horizontally on some folds of 
 of paper. 
 
 Cut two pieces of very thin and transparent paper rather larger 
 than the plate. Soak them in pure water, and remove the excess of 
 moisture by pressing them between folds of blotting paper. Cover one 
 side of each piece with a solution of dextrine made just so thin as not to 
 draw into threads when taken up on a brush. Place one of these pieces 
 on the collodion in such a manner as to exclude air bubbles, lay upon it 
 a plate of glass somewhat larger than that on which the picture was 
 taken, and press strongly upon it to bring the paper and collodion into 
 perfect contact. Turn over both the glasses, and remove that on which 
 the picture was originally taken, by pushing it off horizontally. The 
 collodion remains adhering to the paper, but still presents some inequal- 
 ities of surface, and sometimes even retains some bubbles of air; to get 
 rid of these imperfections, lay the second piece of paper over the collo- 
 dion, in such a manner as to inclose the latter between the two sheets of 
 paper. Lay over the whole some folds of blotting paper, and rub 
 strongly on the top with the hand, to expel the excess of dextrine. Fi- 
 nally, rub over the whole with a plate of agate or marble, which serves as 
 a kind of burnisher, and insures perfect contact. Remove the picture 
 from the glass and hang it up to dry ; when dry it must be waxed in the 
 same manner as a proof on paper. 
 
 These proofs possess one advantage over those on glass besides their 
 greater indestructability, mz: — that we can touch up any little white 
 spots or flaws in the collodion, which is not easily done on glass." 
 
 NEGATIVES BY ALBUMEN. 
 
 The albumen for this purpose may be prepared precisely as directed 
 for the preparation of albumenized negative paper, or if preferred, very 
 good results may be obtained by the use of iodide of potassium or 
 ammonium in the proportion of 1 gr. of iodide to every 100 of albumen, 
 the whole being beaten into a thick white froth, allowed to stand for 
 twelve hours, and the clear liquid decanted. 
 
 The glass being perfectly cleaned as directed for the collodion 
 negatives, place it on a levelling stand and pour an abundance of 
 
46 
 
 albumen upon it. Incline it in every direction to make the liquid 
 flow all over it, and pour off the excess at one corner. Replace the 
 glass on the levelling stand, and allow it to dry in a peifectly horizontal 
 position, preserving it from dust by a cardboard cover, or any other con- 
 venient means. The plates may be preserved in this state for any time. 
 To render the plate sensitive, hold it to the fire to remove the last trace 
 of moisture, and then immerse it in a bath composed of 
 
 Nitrate of Silver 305 grains. 
 
 Distilled Water 10 oz. 
 
 Acetic Acid IJ oz. 
 
 The plate is immersed in the same manner as the collodion proof ; 
 after two or three minutes, remove the plate from the bath, wash it well 
 in distilled water, and allow it to dry in perfect darkness ; it will preserve 
 its sensibility for two or three days. 
 
 The image is developed and fixed in precisely the same manner as 
 those obtained on paper ; the time of exposure in the camera is however 
 much longer, from half an hour to an hour being required to obtain a 
 good proof.* 
 
 The Rev. W. Kingsly recommends the addition to the albumen of a 
 small quantity of bromide of iron, having the bromine slightly in excess ; 
 he sayS;> by this means he obtains pictures with almost as great rapidity 
 as on collodion ; he does not however state the quantity he employs. 
 
 The following letter, published by Mr. Reeves in '^The Expositor/' 
 describes a process by which an even coating on the albumen is more 
 easily obtained; it yields in the hands of its author very beautiful results. 
 
 " Take an ounce measure of the white of egg, add to it seven 
 grains of iodide of potassium, and two grains of bromide of potas- 
 sium ; shake it up in a bottle until the whole forms one mass of froth, 
 which will not run on the bottle being inverted. In two or three hours 
 suflBcient liquid will have separated to coat the plates. Procure a glass 
 tube about an inch in diameter and six or eight long, and tie over one end 
 
 * M. Le Gray states that both the time of exposure, and that required for developing 
 the image, may be much decreased, by using instead of the gallic acid a saturated 
 solution of proto-sulphate of iron, to which one tenth of its bulk of glacial acetic acid 
 has been added. 
 
47 
 
 a piece of fine linen. The above albumen is then poured into this tube 
 and forced out by blowing, on the glass plate, which must first be cleaned 
 not with strong nitric acid, but by a few drops of spirit and a little chalk, 
 on a piece of clean leather. The albumen is now forced through the tube 
 on the plate, which is held horizontally on the finger. The diffusion of the 
 liquid might be facilitated by spreading it with the edge of another piece 
 of glass. An excess ought to be placed on the glass and made flow all 
 over, by inclining the plate from side to side. The excess is then made 
 to flow off at one corner into a glass, to be returned to the tube when 
 required. The plate should not be drained much, as a thin coat is not 
 so sensitive as a thicker. The coated plate is better put aside on a hori- 
 zontal board and covered over while another is prepared in a similar 
 manner. A square tin vessel is to be procured, of dimensions not less 
 than two inches greater than the glass to be coated. A piece of thin 
 plate glass is to be supported on the inside in a horizontal position, and 
 about an inch less each way than the tin vessel. This vessel ought to 
 have a cover in the form of a pyramid, that the steam might trickle 
 down the sides and not drop on the prepared plate. An iron tripod-stand 
 sufficiently high to admit a chauffer underneath, with an adjusting-screw 
 in each foot, is the best support, as it allows the apparatus to be levelled 
 with the greatest nicety. When the apparatus boils,* put the glass first 
 prepared on the middle of that which was levelled in the boiler, and 
 place the cover on. In about two minutes the albumen is coagulated 
 firmly, and will bear rubbing when wetted. If the plate is not kept in 
 long enough it will be soft when wetted, and subject to all the difficul- 
 ties the other processes were. If it is kept in too long it will be liable 
 to crack, the commencement of which might be noticed around the 
 edges, and should be the signal to remove it. The coating is best dried 
 by leaving it in the boiler, while the cover is placed crossways over the 
 plate to prevent dust from falling on it ; the steam then escapes, and the 
 albumen quickly dries and becomes transparent. It will be observed 
 that in this process the coagulation takes place in an atmosphere of steam, 
 which is essential, otherwise the thin film would dry before arriving at 
 the necessary temperature, and coagulation would be impossible, coagu- 
 lated albumen being a hydrate — a fact not mentioned before in connexion 
 
 * We presume Mr. K. means water to be put into the tin vessel and then made to boil. 
 
48 
 
 with this process, and which rendered the other published processes so 
 difficult, the coagulation in their case being generally performed by the 
 acetic acid of an after operation, and not by the heat. This coagulation 
 is soft, and very difficult to obtain without lines called ripple marJis. 
 Prepared glass plates are best preserved in a daguerreotype-plate box. 
 To make them sensitive, dip them into a solution of aceto-nitrate of 
 silver, consisting of about thirty grains of nitrate to an ounce of water, 
 and one-sixth its bulk of strong acetic acid ; to which add one-eighth of 
 alcohol. The plate is then removed and well washed in water, and placed 
 in the camera wet or dry ; in the latter case it is less sensitive. If a very 
 sensitive plate is required, it must not be washed at all, but placed in 
 the camera immediately, as it does not do well to allow it to dry in 
 that state. When the exposition in camera has taken place, the picture 
 is developed by placing the plate first in the nitrate of silver before 
 mentioned, and then in a saturated filtered solution of gallic acid, 
 sufficient to cover the plate. When well developed, which might be 
 known by holding the plate up before a candle, it is desirable to wash 
 it with cotton and water to remove any surface deposit. Strong hypo- 
 sulphite must not be used for fixing, as it is liable to detach the coating 
 from the plate, but bromide of potassium of twenty-five grains to six 
 ounces of water. The glass must be washed previous to going into the 
 bromide of potassium, and also after. 
 
 The process which I have detailed I have carried largely into 
 practice, it is simple and certain in its results. I and Mr. Nichols first 
 used the steam-bath four or five years since, but could not succeed to 
 our satisfaction until I again turned my attention to it last spring. 
 
 Thomas Reeves." 
 
 N.B. — Plenty of water must be kept in the boiler, and sustained 
 briskly boiling. 
 
49 
 
 PREPARATION OF POSITIVE PAPER. 
 
 It is difficult to give more than general directions for the prepara- 
 tion of positive paper, as the precise proportions of the various ingredients 
 to be employed must depend on the tone of color the operator wishes 
 to produce, and must also be modified according to the paper that is 
 employed. It may in general be said that the French papers of Canson 
 Freres are best suited for the production of black, and the English 
 papers of Turner or Whatman for that of brown or reddish tints. 
 
 All positive processes mainly consist in impregnating the paper 
 first with a chloride or bromide of an alkalie, or alkaline earth, and 
 subsequently washing it with nitrate of silver, by which means the 
 surface of the paper becomes covered with a chloride or bromide of 
 that metal. 
 
 Various methods are employed to spread the solution on the paper , 
 some soaking the paper completely in the solution of chloride, others 
 floating the sheet npon it so as to touch one side only, while some apply 
 it with a brush. I have found the best results produced by applying 
 the solution to one side only, and I believe nothing is better for this 
 purpose than a clean sponge 3 it lays on the solution more perfectly than 
 a brush, and is less trouble than floating the paper on to a bath of the 
 solution. The solution of nitrate of silver may also be applied in many 
 ways. By spreading some of the solution on a level glass plate and 
 floating the sheet upon it. By pouring a small quantity of the solution 
 on to the paper and spreading it with a glass rod. By means of a brush 
 &c. Mr. Buckle recommends a bunch of clean cotton held in a glass 
 tube by means of a silver wire, the cotton being changed as soon as it 
 gets dirty. I generally use a piece of sponge tied on to a glass rod ; 
 by washing this occasionally in distilled water it may be used for a long 
 time and answers the purpose perfectly. 
 
 I shall now proceed to describe some of the solutions more com- 
 monly employed, premising that they may be altered almost infinitely 
 according to the taste of the operator, provided he take care always to 
 employ the nitrate of silver in sufficient quantity to decompose all the 
 chlorides present in the paper, as a small quantity of an alkaline chloride 
 left undecomposed much impairs its sensibility. 
 
 D 
 
No. 1. Hydrochlorate of Ammonia, or Chloride of Sodium 5 grs. 
 
 Water 1 f. oz. 
 
 Wash the paper on one side only with this solution, and when it is dry * 
 apply— 
 
 Nitrate of silver 60 grs. 
 
 Distilled Water 1 oz. 
 
 Some prefer washing the paper twice with a solution of nitrate of 
 silver, 30 grs. to 1 oz. of water, allowing the paper to dry, or drying it at 
 the fire, between the two washings. Ammoniacal solution of nitrate of 
 silver may also be employed, and it is easier with this solution to obtain 
 a perfectly even surface. The solution is made by dropping strong 
 liquid ammonia into the solution of nitrate of silver above described, 
 until the precipitate, which is at first produced, is nearly all dissolved ; 
 the undissolved portion is allowed to subside, and the clear liquid 
 employed. 
 
 No. 2. Hydrochlorate of ammonia 2 
 
 Water 1 f. oz. 
 
 Followed by — 
 
 Nitrate of Silver 20 grs. 
 
 Distilled Water 1 f. oz. 
 
 This gives very delicate and pleasing tones, but they are more apt to 
 fade than when a stronger solution is employed. 
 
 No. 3. Le Gray recommends — 
 
 Hydrochlorate of Ammonia .... 5 grs. 
 
 Distilled Water 100 grs. 
 
 Followed by — 
 
 Nitrate of Silver 15 grs. 
 
 Distilled Water 100 grs. 
 
 This preparation, or No. 1, is the best to employ when the proof 
 is to be fixed with chloride of gold as hereafter described. 
 
51 
 
 No. 4. Bromide of Potassium 10 grs. 
 
 Water » 1 f. oz. 
 
 ' Followed by — 
 
 Nitrate of Silver 30 grs. 
 
 Distilled Water 1 f. oz. 
 
 The amount of nitrate of silver employed with this proportion of 
 bromide may vary from 25 to 60 grs. in the oz., and a variety of very 
 pleasing tints be thus produced. 
 
 No. 5. Chloride of Barium 5 grs. 
 
 Water 1 f. oz. 
 
 Followed by-— 
 
 Nitrate of Silver 30 grs. 
 
 Distilled Water 1 f. oz. 
 
 The ammoniacal solution of nitrate of silver may be substituted 
 for the solution here named. Small quantities of chloride of barium, 
 or bromide of potassium, may be mixed with any of the solutions of 
 hydrochlorate of ammonia above mentioned, and in this way almost an 
 endless variety of tints may be obtain ed. The paper, after being washed 
 with the chloride solution, may be kept for any time, but the nitrate 
 of silver should not be applied more than two or three days before the 
 paper is used ; indeed, it is better to use it as soon as possible after it 
 has been made sensitive. It is almost needless to remark, that after the 
 nitrate of silver is applied, the paper must not be exposed to light, and 
 should be kept as much as possible from the air. Very pleasing effects 
 may be produced by adding to the chloride solution, sugar of milk, grape 
 sugar, or mannite, in the proportion of 4 or 5 grs. to the oz., darker 
 tints, more approaching to black, are thus obtained. Isinglass in the 
 proportion of 4 grs. to the oz. is also a very good addition to the chloride 
 solution, especially if paper which has not a very good surface be 
 employed. 
 
 D 2 
 
52 
 
 POSITIVE ALBUMENIZED PAPER. 
 
 By the use of albumen, almost any paper may be made to yield 
 good pictures. The details are in all cases more perfectly preserved than 
 they can be on plain paper, however fine its grain. 
 
 To the whites of eggs add hydrochlorate of ammonia in any of the 
 proportions recommended previously for making the chloride solution, 
 4 or 5 grains to the ounce answers very well. Beat the whole into a 
 thick froth with a wooden or silver fork, allow it to stand for about twelve 
 hours, and decant the clear liquor which subsides. Apply this liquid to 
 one side of the paper, allow it to dry, and iron it, in precisely the same 
 manner as directed for the preparation of negative albumenized paper. If 
 the highly varnished appearance of this paper be thought objectionable, 
 the albumen may be diluted with its own bulk of water. 
 
 To render this paper sensitive, it is placed with its albumenized side 
 downwards on a bath of nitrate of silver, the strength of which may vary 
 according to the tint we wish to obtain. With the proportion of hydro- 
 chlorate of ammonia recommended above, 60 grs. to the oz. gives very 
 good results. 
 
 Mr. Henneman recommends the following proportions as yielding a 
 very sensitive paper more particularly adapted for printing rapidly in 
 dull weather. 
 
 White of Egg 1 f. oz. 
 
 Distilled Water 1 f. oz. 
 
 Chloride of Sodium i oz. 
 
 Followed by — 
 
 Nitrate of Silver 120 grs. 
 
 Distilled Water 1 oz. 
 
 PRINTING THE POSITIVE. 
 
 Place the negative face upwards on the glass of the pressure frame j 
 over it a sheet of positive paper somewhat larger than the negative, with 
 its prepared side downwards ; then put the back board of the pressure 
 frame in its place, and bring the negative into as close contact as 
 possible with the positive paper, by tightening the screws at the back, 
 
53 
 
 taking care to make the pressure as even as possible, otherwise the glass 
 is apt to be broken. Then expose the frame to the light of the sun, in such 
 a way that the rays fall perpendicularly upon the negative ; bright sun- 
 shine is always preferable, as the proof requires less exposure, and the 
 results are always more brilliant than those produced by a longer expo- 
 sure to diffused daylight. If the back of the frame be jointed in the middle 
 to enable you to see the progress of the printing, it is as well to place a 
 sheet of card board between the positive paper and the back, as the 
 working of the joint will sometimes tear the paper. Should the back not 
 be jointed, the negative should be fastened to the positive paper at two 
 corners by some gummed paper, in order that the back of the frame may 
 be removed, and the picture from time to time examined without shifting 
 one upon the other. 
 
 The time of printing will vary with the paper employed, and the 
 tint required; it is always however necessary to allow the proof to 
 become darker than it is intended to be ultimately, as it fades a good 
 deal during the process of fixing. In general it may be said that the 
 parts intended to be white, should bo allowed to assume a light grey tint. 
 
 FIXING THE POSITIVE. 
 
 This is perhaps the most important operation in the whole process, 
 not only because the stability of the proof is dependent on the care with 
 which it is performed, but because infinite variety of tint may be pro- 
 duced by slight variations in the manner of conducting it. 
 
 Hyposulphite of soda is employed to fix the positive as well as the 
 negative proof. It is found by experience that an old solution gives more 
 agreeable tints than a new one ; the fixing however is less perfect, and a 
 I^roof fixed with old solution should always be placed for a short time in 
 a fresh solution before it is washed, to be sure that all the salts of silver 
 are removed. As old solution of hyposulphite is not always to be had, 
 the same effect may be produced in the following manner : — 
 
 Dissolve 80 grs. of nitrate of silver in distilled water, and add to the 
 solution, either a solution of salt or hydrochloric acid, until the whole of 
 the silver is precipitated. Allow the precipitate to subside, and wash it 
 repeatedly with water until all trace of salt or acid is removed ; then ex- 
 pose it to the light till it is quite black. Afterwards dissolve it in the 
 
54 
 
 following solution: — Hyposulphite of soda loz., distilled water 6 oz. 
 Should a precipitate appear in this bath after frequent use, a little fresh 
 solution of hyposulphite should be added to it, the whole allowed to 
 subside, and the clear solution poured off. Wash the proof well in 
 water to remove all undecomposed nitrate of silver, and then plunge it 
 completely into the above solution, and allow it to remain at least axi 
 hour. The tint of the picture depends much on the time it is left! 
 in this solution, but less than an hour will not fix it perfectly. Remove 
 it from this bath, wash it in water, and place it in a bath of new 
 hyposulphite, containing one part of the salt to eight of water, let it 
 soak for about ten minutes, wash it well in many waters and then allow 
 it to float in a large basin of water for at least twelve hours, changing 
 the water every hour, to remove all trace of hyposulphite. Should 
 this not be done, the proof is sure to fade ; even with the greatest care 
 it is harldy possible to fix a proof so perfectly as to stand the action of a 
 damp atmosphere, although it may be quite unalterable by light. 
 
 Some operators recommend placing the proof after it is fixed and 
 washed, in a warm solution of carbonate of soda, and subsequently again 
 washing ; this is said to remove the hyposulphite more perfectly, it 
 however much damages the tone of the picture. 
 
 M. Le Gray attributes the fading of the positives to the hyposulphite 
 being partly decomposed during the process of fixing, and depositing 
 sulphur in the pores of the paper. To remove this, he employs alcohol 
 mixed with one-third of its bulk of bisulphide of carbon; the proof 
 after being soaked in this solution, is to be washed, first in alcohol, and 
 then plentifully in water; in this manner he says he obtains perfect 
 fixation. He also recommends the addition of a little ammonia to the 
 hyposulphite, not only as giving greater stability to the proof, but 
 improving its color. 
 
 The following process for producing proofs of a very pure black 
 and white colour, and in which all the details are very beautifully 
 preserved, is also extracted from Le Gray's last work. It possesses, 
 according to its author, not only the advantage of giving very beautiful 
 tints, but that the proofs are quite unalterable. To the truth of the 
 former part of this statement I can bear witness ; I have not yet kept 
 any proofs long enough to feel sure about the latter. 
 
 The positive paper is prepared in the ordinary way. The proof is 
 
55 
 
 exposed to the light for a longer time than when it is to be fixed by the 
 ordinary means. To obtain a proof of a blueish black colour in the 
 dark parts, the whites should be allowed to become of a light violet 
 color. To obtain a full black in the dark parts, the exposure should be 
 long enough to make the whites of a very decided violet colour. And 
 for a greenish black, the whites should be printed of a sepia tint. 
 
 After the exposure is complete, wash the proof well in water, to 
 remove all undecomposed nitrate of silver. If weak solutions of nitrate 
 of silver and hydrochlorate of ammonia have been employed, this 
 washing may be omitted. Washed or not, place the proof in the following 
 bath 
 
 Keep the proof agitated all the while it remains immersed.- The 
 image almost immediately begins to clear, the olive tints pass to black, 
 and the lights lose color but do not disappear. When the dark parts 
 are perfectly clear, and all the details of the negative well defined, 
 remove the proof fi'om the bath and wash it in five or six waters to 
 remove all trace of acid. This washing must be conducted with the 
 greatest care, as if any acid be left in the proof, it causes a precipitate 
 of sulphur when it is placed in the hyposulphite of soda. To avoid this 
 it is better to mix a little ammonia with the first wash water employed ; 
 washing in two waters after this will be sufficient. After it is washed, 
 place the proof in a bath of hyposulphite of soda, containing 1 part of 
 the salt to 6 of water. The proof must not be left in the bath less than 
 half an hour, and may remain there for three or four hours without 
 any of the details being destroyed ; the precise tint being determined 
 by the length of time the proof remains in the hyposulphite. The 
 fixing is finished in the usual way by repeated washing in water. By 
 using a bath of hyposulphite, containing chloride of silver in solution, 
 still richer tones are produced j but the proof should always be placed 
 for a few minutes in a bath of fresh hyposulphite, before being finally 
 washed. 
 
 The addition of hydrochloric acid to the chloride of gold, precipi- 
 
 Distilled Water . , 
 Chloride of Gold 
 Hydrochloric Acid 
 
 1000 grs. 
 1 gr. 
 26 grs. 
 
56 
 
 tates any silver which may remain in the proof, in the form of chloride, 
 which cleans the whites of the picture ; the chloride of silver being more 
 easily dissolved by the hyposulphite, than any other salt. 
 
 A very beautiful neutral tint may be given to positives fixed in the 
 ordinary manner, by immersing them for a few minutes in the following 
 solution : — 
 
 Proofs of a bad colour may generally be rendered very beautiful by 
 the use of this solution, they of course require to be well washed when 
 removed from the bath. 
 
 In 1843, Sir J. Herschel described a process to which he gave the name 
 of Chrysotype, which might be employed to produce either positives or 
 negatives. As the paper requires a somewhat long exposure in the 
 camera, it is more frequently employed for the former, and gives very 
 beautiful results. The following details were published in the Philoso- 
 phical Magazine for March, 1843 : — 
 
 " Paper is to be washed with a moderately concentrated solution of 
 ammonio- citrate of iron, and dried. The strength of the solution should 
 be such as to dry into a good yellow colour, not at all brown. 
 
 In this state it is ready to receive the photographic image, which 
 may be impressed upon it either from nature in the camera obscura, or 
 from an engraving on a frame in sunshine. The image so impressed, 
 however, is very faint and sometimes hardly perceptible. The moment 
 it is removed from the frame or camera, it must be washed over with a 
 neutral solution of gold of such strength as to have about the color of 
 sherry wine. Instantly the picture appears, not indeed at once of its 
 full intensity, but darkening with great rapidity up to a certain point, 
 depending on the strength of the solutions used, &c. As soon as the 
 picture is satisfactorily brought out by the auriferous liquid, it is to be 
 rinsed in water which is to be three times renewed, letting it remain in 
 
 Hyposulphite of Soda 
 
 Water 
 
 Nitrate of Silver 
 
 Chloride of Gold.... 
 
 1 pint. 
 40 grs. 
 6 grs. 
 
 2 oz. 
 
57 
 
 the third water five or ten minutes. It is then to be blotted off and 
 dried, after which it is to be washed on both sides with a somewhat weak 
 solution of hydriodate of potash. If there be any free chloride of gold 
 present in the pores of the paper, it will be discoloured, the lights passing 
 to a ruddy brown, but they speedily whiten again spontaneously, or at 
 all events on throwing it (after lying a minute or two) into fresh water, in 
 which being again rinsed and dried, it is now perfectly fixed. 
 
 " If paper prepared as above directed be washed with nitrate of silver 
 instead of solution of gold, a very sharp and beautiful picture is developed, 
 of great intensity. Its disclosure is not instantaneous ; a few moments 
 elapse without apparent effect; the dark shades are then first touched in, 
 and by degrees the details appear, but much more slowly than in the case 
 of gold : in two or three minutes however the maximum of distinctness 
 will not fail to be attained. The picture may be fixed by the hyposul- 
 phite of soda, which alone, I believe, can be fully depended on for fixing 
 argentine photographs.'* 
 
 M. Le Gray, who has lately been experimenting with this paper, 
 says that a little nitrate of silver added to the solution of ammonio- citrate 
 of iron, increases the sensibility of the paper to such an extent, that it 
 can be well used in the camera. He employs the following solution : — 
 
 Saturated Solution of Ammonio-citrate iron. . . 100 grammes. 
 
 Distilled Water 100 „ 
 
 iVitrate of Silver 2 „ 
 
 He says that the pictures may be developed not only with solutions 
 of gold and silver, but also with gallic acid. 
 
 Very beautitul positives may be obtained on any of the unwaxed 
 negative papers, and in dull weather better pictures can be obtained by 
 this means, than on the ordinary positive paper. The time required for 
 printing a proof on these papers is about one minute, or one minute and 
 a half, by diffused daylight, and one or two seconds in sunshine. 
 
 D a 
 
POSITIVES ON GLASS 
 
 BY COLLODION, &c. 
 
 The collodion for the production of positives, should be somewhat 
 thinner than that employed for negatives ; 3 grs. of paper or cotton to the 
 oz. of mixed alcohol and ether, and 4 grains of iodide of potassium, will 
 generally be found sufficient. The production of a positive instead of a 
 negative picture depends mainly on two circumstances, vi:t : the time of 
 exposure in the camera, and the nature of the developing solution. 
 Much less time is required to produce a positive than a negative, about 
 one half the amount of exposure being sufficient. 
 
 To develop a positive, Mr. Horne recommended the addition of a 
 little nitric acid to the pyro-gallic solution, but gave no proportion. I 
 find that 1 drop of nitric acid to 2 drachms of the solution of pyro-gallic 
 acid mentioned in a previous section, gives remarkably beautiful tints. 
 A much longer time is required for the development ; I have never 
 known a good picture produced in less than five minutes, and it is often 
 as much as twenty minutes before the development is complete. The 
 fixing of the picture is performed in precisely the same way as that of a 
 negative. When finished, the picture should be mounted with a black 
 back ground ; nothing is so good for this as a piece of thick cotton velvet. 
 Some operators varnish the picture with Brunswick black instead of 
 placing a black substance behind it ; but this is very apt to shew through 
 the white parts of the picture, and much impairs the effect. 
 
 Mr. Hennah gives the following formula for developing solution for 
 positives. 
 
59 
 
 Protosulphate Iron 
 
 Nitric Acid 
 
 Distilled Water ... 
 
 15 grs. 
 1 or 2 drops. 
 1 oz. 
 
 Or, 
 
 Protosulphate Iron 
 Acetic Acid 
 
 20 grs. 
 
 1 drachm. 
 
 2 drops. 
 1 oz. 
 
 -Nitric Acid 
 
 Distilled Water 
 
 He says that with this solution, soon after the picture begins to 
 appear, and before the whole is visible, the developing solution must be 
 poured off; it must be well washed with water, and fixed with the same 
 solution of hyposulphite of soda as that used for negatives. 
 
 Dr. Diamond recommends a solution of proto -nitrate of iron pre- 
 pared as follows : — 
 
 300 grains of nitrate of baryta are dissolved in 3 oz. of boiling dis- 
 tilled water. When the solution is complete, add 320 grs. of crystallized 
 proto -sulphate of iron. When the white precipitate of sulphate of baryta 
 has subsided, the clear solution of proto-nitrate of iron is poured off into 
 a stoppered bottle for use. When this solution is to be used, it is mixed 
 with a solution of 
 
 in the proportion of 6 drops of the pyrogallic solution to 1 drachm of 
 the proto-nitrate of iron. The solution of proto-nitrate of iron should 
 be fresh made, as it will not keep for any length of time. 
 
 The production of positive pictures on collodion being so much more 
 rapid than that of negatives, renders the process peculiarly adapted for 
 taking moving objects. Mr. R. Hunt having lately stated that he did not 
 think any process sufficiently rapid to obtain a representation of the waves 
 of the sea, I may mention that I have seen pictures by Mr. W. Jackson of 
 Lancaster, in which they were very perfectly represented. The process 
 which he employs was published in a former edition of this work, and 
 signed W. G. It consists in adding to each oz. of the ordinary iodized 
 collodion, 1 gr. of arsenious acid; exciting with solution of nitrate of 
 silver 100 grs. to the oz. of distilled water, to which some iodide of 
 
 Pyrogallic Acid 
 
 Water 
 
 Acetic Acid . . . 
 
 3 grs. 
 1 oz. 
 
 1 drachm. 
 
60 
 
 potassium has been added to prevent its action on the plate ; and de- 
 veloping with solution of proto-sulphate or proto-nitrate of iron 40 grs.to 
 1 oz. of distilled water. Warming the sensitive bath to about 100° F. 
 still further increases the sensibility of the plate. 
 
 M. Martin has lately published a process for producing very powerful 
 positives. The collodion is prepared and applied to the plate in the usual 
 way ; it is rendered sensitive by immersion in the following solution : — 
 
 Nitrate of Silver 365 grs. 
 
 Nitric Acid 218 grs. 
 
 Distilled Water 10 oz. 
 
 The image is developed in a bath of proto-sulphate of iron. When 
 sufficiently developed it is well washed in water, and immersed in a bath 
 consisting of 
 
 Cyanide of Potassium 386 grs. 
 
 Nitrate of Silver 62 grs. 
 
 Distilled Water 35 oz. 
 
 This bath almost immediately converts the negative into a positive. 
 No farther fixing is required. 
 
 Very beautiful positives, especially for viewing as transparencies, or 
 for use as slides to a magic lantern, may be produced on albumenized glass 
 plates. Any of the preparations recommended for negatives on albumen 
 may be employed, but the following preparation gives the best positives : 
 
 White of Egg 1 f. oz. 
 
 Distilled Water J f. oz. 
 
 Saturated solution of Iodide of Potassium 10 drops, 
 
 the whole beaten into a froth, left to subside, and the clear liquor poured 
 on the glass in the manner before described. The plates are excited with 
 solution of nitrate of silver 25 grains to 1 oz, of distilled water, to every 8 
 parts of which, one part of glacial acetic acid has been added. The image 
 is developed with saturated solution of gallic acid, and a few drops of solu- 
 tion of nitrate of silver. The picture is obtained by placing a negative 
 on the prepared surface, and exposing to the light in the same manner as 
 positives are printed on paper. Ten minutes will generally be found 
 about the right time of exposure. 
 
61 
 
 PROCESS FOR COPYING 
 
 MICROSCOPIC OBJECTS. 
 
 The application of photography to the representation of microscopic 
 objects has lately attracted a good deal of attention. I transcribe from 
 the last number of The Microscopic Journal the directions given by Mr. 
 J, Delves, of Tonbridge, whose beautiful specimens have excited such 
 general admiration. 
 
 The only arrangement necessary for the purpose is the addition to 
 the microscope of a dark chamber, similar to that of the camera obscura, 
 having at one end an aperture for the insertion of the eye-piece end of 
 the compound body, and at the other a groove for carrying the ground- 
 glass plate. 
 
 " This dark chamber should not exceed 24 inches in length (the size 
 which I have found best to adopt) : if extended beyond this, the pencil 
 of light transmitted by the object-glass is diffused over too large a 
 surface, and a faint and unsatisfactory picture is the result. The eye- 
 piece must be removed from the compound body, and the object (being 
 well illuminated by reflection from the concave mirror) must be adjusted 
 and focused upon the ground- glass plate.* In the production of positive 
 pictures a slight difficulty here arises, dependent upon the "over- 
 correction" of the object glass. The effect of this " over-correction" 
 is to project the blue rays of light beyond the other rays of the spectrum, 
 and as the chemical properties of light reside in the violet and blue rays, 
 it becomes necessary that the plane of the sensitive plate should coincide 
 with the foci of these rays, and it must therefore be placed beyond the 
 surface at which the best definition is seen ; this amounts to some 
 distance with the lower combinations, and decreases with the increase 
 of magnifying power. 
 
 " For the production of negative pictures, the ordinary illumination 
 is not sufficient, and recourse must be had to the sunbeam, which should 
 be reflected upon the object by the plane mirror when powers are used 
 not exceeding the quarter of an inch combination. It is not necessary 
 here (when producing negatives by the sun beam) to allow for the 
 over-correction" of the object-glass, but merely to focus the object 
 carefully upon the ground-glass plate. 
 
 " In the production of negative pictures, a moment's exposure 
 to the sunbeam is sufficient when using the lowest powers, and with the 
 highest I have varied the time from five to ten seconds." 
 
 * The microscope must be placed in a perfectly horizontal position, in order to 
 adapt it to the dark chamber. 
 
62 
 
 An ordinary camera may be used for this purpose, the lens being 
 removed and the eye-piece end of the microscope being introduced into the 
 brass tube which carries it, the space between being filled up with a black 
 silk handkerchief, or any convenient material which will exclude the 
 light, and at the same time allow the tube of the microscope sufficient 
 freedom for focusing. A tube of paper lined with black velvet or some 
 other non-reflecting substance should be placed in the inside of the body 
 of the microscope to prevent reflection from its sides. When using 
 artificial light (a camphine lamp is best for the purpose), the mirror 
 must be removed and a good condensing lens of about 2^ inch diameter 
 with its plane side next the lamp must be substituted, the precise position 
 of this lens must of course depend on its focal length. The time of 
 exposure necessary will vary with every object glass, and every object, 
 and can only be determined by experiment. 
 
 STEREOSCOPIC PICTURES. 
 
 The extremely beautiful effects produced by properly prepared 
 photographs when viewed in the stereoscope, induce me to think that 
 some directions for their production may not be unacceptable. 
 
 It is to Professor Wheatstone that we owe the invention of the 
 stereoscope, and to his admirable papers on Binocular vision 1 must 
 refer those who require a full account of the instrument and the interest- 
 ing phenomena with which it is connected. I shall only here say enough 
 of the instrument to enable the reader to understand the process for 
 producing the pictures, and in doing this I shall avail myself as much 
 as possible of Professor Wheatstone's own words. In the commencement 
 of his paper, read before the Royal Society, June 12th, 1838, he says — 
 
 When an object is viewed at so great a distance that the optic 
 axes of both eyes are sensibly parallel when directed towards it, the 
 perspective projections of it, seen by each eye separately, are similar, 
 and the appearance to the two eyes is precisely the same as when the 
 
63 
 
 object is seen by one eye only. There is in such case no difference 
 between the visual appearance of an object in relief, and its perspective 
 projection on a plane surface ; and hence pictorial representations of 
 distant objects, when those circumstances which would prevent or disturb 
 the illusion are carefully excluded, may be rendered such perfect resem- 
 blances of the objects they are intended to represent as to be mistaken 
 for them ; the Diorama is an instance of this. But this similarity no 
 longer exists when the object is placed so near the eyes that to view it 
 the optic axes must converge ; under these conditions a different pers- 
 pective projection of it is seen by each eye, and these perspectives are 
 more dissimilar as the convergence of the optic axes becomes greater. 
 This fact may be easily verified by placing any figure of three dimensions, 
 an outline cube, for instance, at a moderate distance before the eyes, and 
 while the head is kept perfectly steady, viewing it with each eye succes- 
 sively while the other is closed. Fig. 6 represents the two perepective 
 projections of a cube ; h is that seen by the right eye, and a that presented 
 to the left eye ; the figure being supposed to be placed about seven inches 
 immediately before the spectator. 
 
 " The appearances, which are by this simple experiment rendered so 
 obvious, may be easily inferred from the established laws of perspective; 
 for the same object in relief is, when viewed by a different eye, seen 
 from two points of sight at a distance from each other equal to the line 
 joining the two eyes. Yet they seem to have escaped the attention of 
 every philosopher and artist who has treated of the subjects of vision 
 and perspective. I can ascribe this inattention to a phoenomenon leading 
 to the important and curious consequences, which will form the subject 
 of the present communication, only to this circumstance; that the 
 results being contrary to a principle which was very generally maintained 
 by optical writers, viz. that objects can be seen single only when their 
 images fall on corresponding points of the two retinae, an hypothesis 
 which will be hereafter discussed ; if the consideration ever arose in their 
 minds, it was hastily discarded under the conviction, that if the pictures 
 presented to the two eyes are under certain circumstances dissimilar, 
 their differences must be so small that they need not be taken into account. 
 
 " It will now be obvious why it is impossible for the artist to give a 
 faithful representation of any near solid object, that is, to produce a 
 painting which shall not be distinguished in the mind from the object 
 itself When the painting and the object are seen with both eyes, in the 
 case of the painting two similar pictures are projected on the retinse, 
 in the case of the solid object the pictures are dissimilar ; there is there- 
 fore an essential difference between the impressions on the organs of 
 sensation in the two cases, and consequently between the perceptions 
 formed in the mind ; the painting therefore cannot be confounded with 
 the solid object. 
 
 After looking over the works of many authors who might be expected 
 to have made some remarks relating to this subject, I have been able to 
 find but one, which is in the Trait ato della Pittura of Leonardo da 
 Vinci.* This great artist and ingenious philosopher observes, 'that a 
 
 * See also a Treatise of Painting, p. 178. London, 1721 ; and Dr. Smith's Complete 
 System of Optics, vol. ii. p. 244, where the passage is quoted. 
 
64 
 
 painting, though conducted with the greatest art, and finished to the 
 last perfection, both with regard to its contours, its lights, its shadows, 
 and its colours, can never show a relievo equal to that of the natural 
 objects, unless these be viewed at a distance and with a single eye.' 
 ' For,' says he, ' if an object C [fig 3] be viewed by a single eye at 
 
 Fig. 3. 
 
 A, all objects in the space behind it, included as it were in a shadow 
 ECF cast by a candle at A, - are invisible to the eye at A ; but when the 
 other eye at B is opened, part of these objects become visible to it ; those 
 only being hid from both eyes that are included, as it were, in the double 
 shadow CD, cast by two lights at A and B, and terminated in D, the 
 angular space EDG beyond D being always visible to both eyes. And 
 the hidden space CD is so much the shorter, as the object C is smaller 
 and nearer to the eyes. Thus the object C seen with both eyes becomes, 
 as it were, transparent, according to the usual definition of a transparent 
 thing; namely, that which hides nothing beyond it. But this cannot 
 happen when an object, whose breadth is bigger than that of the pupil, 
 is viewed by a single eye. The truth of this observation is therefore 
 evident, because a painted figure intercepts all the space behind its 
 apparent place, so as to preclude the eyes from the sight of every part 
 of the imaginary ground behind it.' 
 
 "Had Leonardo da Yinci taken, instead of a sphere, a less simple 
 figure for the purpose of his illustration, a cube, for instance, he would 
 not only have observed that the object obscured from each eye a 
 different part of the more distant field of view, but the fact would also 
 perhaps have forced itself upon his attention, that the object itself 
 presented a different appearance to each eye. He failed to do this, and 
 no subsequent writer within my knowledge has supplied the omission ; 
 that two obviously dissimilar pictures are projected on the two retinae 
 when a single object is viewed, while the optic axes converge, must 
 therefore be regarded as a new fact in the theory of vision." 
 
 In a subsequent part of the same paper. Professor Wheatstone scates 
 " that if two perspective projections of the same solid, as it appears to 
 each eye, be simultaneously presented to the eyes, instead of a repre- 
 sentation on a plane surface, as each drawing appears to be when 
 separately viewed by that eye which is directed towards it ; the observer 
 will perceive a figure of three dimensions the exact counterpart of the 
 
\ 
 
 65 
 
 object from which the drawings were made." He then proceeds to 
 describe an instrument by which pictures may be thus presented to 
 the eyes, to which he gave the name of stereoscope, to indicate its pro- 
 perty of representing soHd objects. The form of the instrument may 
 be modified in various ways, but none is so good as that originally des- 
 cribed, as it admits of the use of larger pictures, and of much greater 
 adjustment to suit the sight of various persons, and the peculiarities 
 of the pictures employed. I extract the description from the paper 
 already referred to. 
 
 Fig. 4. 
 
66 
 
 " The stereoscope is represented by figs. 4 and 5 ; the former being 
 a front view, and the latter a plan of the instrument. AA' are two plane 
 mirrors, about four inches square, inserted in frames, and so adjusted 
 that their backs form an angle of 90° with each other ; these mirrors 
 are fixed by their common edge against an upright B, or which was less 
 easy to represent in the drawing, against the middle line of a vertical 
 board, cut away in such manner as to allow the eyes to be placed before 
 two mirrors. C C' are two sliding boards, to which are attached the 
 upright boards D D', which may thus be removed to different distances 
 from the mirrors. In most of the experiments hereafter to be detailed, 
 it is necessary that each upright board shall be at the same distance from 
 the mirror which is opposite to it. To facilitate this double adjustment, 
 I employ a right and a left-handed wooden screw, r I ; the two ends of 
 this compound screw pass through the nuts e e\ which are fixed to the 
 lower parts of the upright boards D D', so that by turning the screw 
 pin p one way the two boards will approach, and by turning it the other 
 they will recede from each other, one always preserving the same distance 
 as the other from the middle line/. E E' are pannels, to which the 
 pictures are fixed in such manner that their corresponding horizontal 
 lines shall be on the same level ; these pannels are capable of sliding 
 backwards and forwards in grooves on the upright boards D D'. The 
 apparatus having been described, it now remains to explain the manner 
 of using it. The observer must place his eyes as near as possible to the 
 mirrors, the right eye before the right-hand mirror, and the left eye 
 before the left-hand mirror, and he must move the sliding pannels E E' 
 to or from him until the two reflected images coincide at the intersection 
 of the optic axes, and form an image of the same apparent magnitude 
 as each of the component pictures. The pictures will indeed coincide 
 when the sliding pannels are in a variety of different positions, and 
 consequently when viewed under different inclinations of the optic axes ; 
 but there is only one position in which the binocular image will be 
 immediately seen single, of its proper magnitude, and without fatigue 
 to the eyes, because in this position only the ordinary relations between 
 the magnitude of the pictures on the retinae, the inclination of the optic 
 axes, and the adaptation of the eye to distinct vision at different distances 
 are preserved. In all the experiments detailed in the present memoir, 
 I shall suppose these relations to remain undisturbed, and the optic axes 
 to converge about six or eight inches before the eyes. 
 
 " If the pictures are all drawn to be seen with the same inclination of 
 the optic axes, the apparatus may be simplified by omitting the screw r I 
 and fixing the upright boards D at the proper distances. The sliding 
 pannels may also be dispensed with, and the drawings themselves be 
 made to slide in the grooves. 
 
 A few pairs of outline figures, calculated to give rise to the per- 
 ception of objects of three dimensions when placed in the stereoscope in 
 the manner described, are represented in figs. 6 to 8. As the drawings 
 are reversed by reflection in the mirrors, I will suppose these figures to 
 be the reflected images, to which the eyes are directed in the apparatus ; 
 those marked b being seen by the right eye, and those marked a by the 
 left eye. The drawings, it has been already explained, are two different 
 projections of the same object seen from two points of sight, the distance 
 
67 
 
 between which is equal to the interval between the eyes of the observer ; 
 this interval is generally about 2J inches. 
 
 Fig. 6. A cube. 
 
 Fig. 6. 
 
 Fig. 7. 
 
 Fig. 7. A cone, having its axis perpendicular to the referent plane 
 and its vertex towards the observer. 
 
 Fig. 8. 
 
 Fig 8. The frustum of a square pyramid; its axis perpendicular 
 to the referent plane, and its base furthest from the eye. 
 
 For the purposes of illustration I have employed only outline figures, 
 for had either shading or colouring been introduced, it might be supposed 
 that the effect was wholly or in part due to these circumstances, whereas 
 by leaving them out of consideration no room is left to doubt that the 
 entire effect of relief is owing to the simultaneous perception of the two 
 monocular projections, one on each retina. But if it be required to 
 obtain the most faithful resemblances of real objects, shadowing and 
 colouring may properly be employed to heighten the effects. Careful 
 attention would enable an artist to draw and paint the two compotent 
 pictures, so as to present to the mind of the observer, in the resultant 
 perception, perfect identity with the object represented. Flowers, crystals, 
 busts, vases, instruments of various kinds, &c., might thus be represented 
 so as not to be distinguished by sight from the real objects themselves. 
 
 The preceding experiments render it evident that there is an essen- 
 tial difference in the appearance of objects when seen with two eyes, and 
 when only one eye is employed, and that the most vivid belief of the 
 
68 
 
 solidity of an object of three dimensions arises from two different 
 perspective projections of it being simultaneously presented to the mind. 
 How happens it then, it may be asked, that persons who see with only 
 one eye form correct notions of solid objects, and never mistake them 
 for pictures ? and how happens it also, that a person having the perfect 
 use of both eyes, perceives no difference in objects around him when he 
 shuts one of them ? To explain these apparent difficulties, it must be 
 kept in mind, that although the simultaneous vision of two dissimilar 
 pictures suggests the relief of objects in the most vivid manner, yet there 
 are other signs which suggest the same ideas to the mind, which, though 
 more ambiguous than the former, become less liable to lead the judgment 
 astray in proportion to the extent of our previous experience. The 
 vividness of relief arising from the projection of two dissimilar pictures, 
 one on each retina, becomes less and less as the object is seen at a greater 
 distance before the eyes, and entirely ceases when it is so distant that the 
 optic axes are parallel while regarding it. We see with both eyes all 
 objects beyond this distance precisely as we see near objects with a single 
 eye ; for the pictures on the two retinje are then exactly similar, and ^e 
 mind appreciates no difference whether two identical pictures fall on 
 corresponding parts of the two retinse, or whether one eye is impressed 
 with only one of these pictures. A person deprived of the sight of one 
 eye sees therefore all external objects near and remote, as a person with 
 both eyes sees remote objects only, but that vivid effect arising from the 
 binocular vision of near objects is not perceived by the former ; to supply 
 this deficiency he has recourse unconsciously to other means of acquiring 
 more accurate information. The motion of the head is the principal 
 means he employs. That the required knowledge may be thus obtained 
 will be evident from the following considerations. The mind associates 
 with the idea of a solid object every different projection of it which 
 experience has hitherto afforded ; a single projection may be ambiguous, 
 from its being also one of the projections of a picture, or of a different 
 solid object 5 but when different projections of the same object are 
 successively presented, they cannot all belong to another object, and the 
 form to which they belong is completely characterized. While the object 
 remains fixed, at every movement of the head it is viewed from a different 
 point of sight, and the picture on the retina consequently continually 
 changes. 
 
 Every one must be aware how greatly the perspective effect of a 
 picture is enhanced by looking at it with only one eye, especially when 
 a tube is employed to exclude the vision of adjacent objects, whose 
 presence might disturb the illusion. Seen under such circumstances 
 from the proper point of sight, the picture projects the same lines, shades 
 and colours on the retina, as the more distant scene which it represents 
 would do were it substituted for it. The appearance which would make 
 us certain that it is a picture is excluded from the sight, and the imagina- 
 tion has room to be active. Several of the older writers erroneously 
 attributed this apparent superiority of monocular vision to the concen- 
 tration of the visual power in a single eye.* 
 
 * " We see more exquisitely with one eye shut than with both, because the vital 
 spirits thus unite themselves the more, and become the stronger : for we may find by 
 looking in a glass whilst we shut one eye, that the pupil of the other dilates." — Lord 
 Bacon's Works, Sylva, Sylvarum, art. Vision. 
 
69 
 
 " There ai'e some facts intimately connnected with the subject of the 
 present article which have already been frequently observed. I allude 
 to the experiments, first made by Du Tour, in which two different 
 colours are presented to corresponding parts of the two retinae. If a 
 blue disc be presented to the right eye and a yellow disc to the corres- 
 ponding part of the left eye, instead of a green disc which would appear 
 if these two colours had mingled before their arrival at a single eye, the 
 mind will perceive the two colours distinctly, one or the other alternately 
 predominating either partially or wholly over the disc. In the same 
 manner the mind perceives no trace of violet when red is presented to 
 one eye and blue to the other, nor any vestage of orange when red and 
 yellow are separately presented in a similar manner. These experiments 
 may be conveniently repeated by placing the coloured discs in the 
 stereoscope, but they have been most usually made by looking at a white 
 object through differently coloured glasses, one applied to each eye." 
 
 Fig 9. 
 
 Fig. 9 represents another form of the stereoscope in which the 
 observer looks directly at the drawings instead of at their reflected images ; 
 the two being made to coalesce by the introduction of two prisms or 
 semi-lenses into the eye-pieces of the instrument. This form possesses th« 
 advantages of cheapness and portability, but can only be used with small 
 drawings, and does not admit of the same amount of adjustment as the 
 reflecting stereoscope. 
 
 It is obvious that to make two pictures of any but the most simple 
 objects with sufficient accuracy to be viewed in the stereoscope, would 
 be extremely difficult, if not impossible ; but as cameras can be placed 
 in any position we please with regard to the object to be represented, 
 photography supplies the means of producing stereoscopic drawings in 
 the greatest perfection. 
 
 It is better if possible, to employ two cameras, and take the two 
 
70 
 
 pictures simultaneously; as, even if the object to be copied remains per- 
 fectly fixed, the light may slightly change, and thus the position of some 
 of the shadows be altered. 
 
 For near objects, such as portraits &c., the following is the best 
 method of proceeding : — Describe a circle on the ground, and draw from 
 its centre two radii, which shall form an angle of about 6° with one 
 another. The object to be copied is placed on the centre of the 
 circle, and the cameras at precisely equal distances from it and in 
 the direction of the radii. Great care must be taken that the images 
 in the two cameras are of precisely the same size, and that the same 
 point of the object occurs precisely in the centre of each picture. To 
 ascertain if this be the case, divide the ground glass of the cameras by 
 pencil lines into a number of squares of about a quarter inch in size, and 
 draw diagonal lines across the glass so as to mark its centre ; by now 
 observing how many of the squares are occupied by the object to be 
 copied, and precisely the spot which coincides with the centre point 
 on the ground glass, and shifting the cameras slightly until the two 
 images perfectly agree in these respects, two pictures adapted for the 
 stereoscope may be obtained. , 
 
 e 
 
 lira.' s dfh 
 
 Fig 10 
 
 To avoid the trouble of drawing the lines on which to place the cameras 
 every time they are wanted, the stand may be marked with a number of 
 lines shewing the positions of the cameras for objects at different distan- 
 ces ; the figure 10 will serve to explain this : — Let A B C D be the board 
 on which the cameras stand, which we will suppose to be exactly 1ft. 
 wide, and of any required length ; the line a b divides it in the middle ; 
 the lines c d and c* d! represent the positions of the camera for an ob- 
 
71 
 
 ject at 4 ft. distance from the point b ; the points c and c' being respect- 
 ively 3.4 in. from the point a, and the points d and df 2.5 in. from the point 
 fe. The other lines represent the positions of the cameras for objects at 
 a greater distance, the distance between the lices increasing 1.25 in. 
 for every 2 ft. that the point b is removed from the object to be copied. 
 For distant objects, such as buildings &c., the operation is still easier, the 
 cameras not requiring to be placed at an angle, but simply removed to 
 a distance from one another varying with that of the object to be copied. 
 Professor Wheatstone has determined that the cameras should be placed 
 parallel to one another, and that the distance between them should 
 increase two feet for every fifty feet that we recede from the nearest 
 object in the landscape. To understand these arrangements, it must 
 be borne in mind that the pictures are not intended to represent the 
 objects as actually seen, but as they would be seen if reduced to the 
 same size as the pictures, and placed at the same distance from the eyes. 
 I cannot too strongly recommend amateurs of photography to turn their 
 attention to this part of the subject. Many a perishable object of great 
 beauty or interest, of which no accurate idea could be conveyed by the 
 finest drawing, may be thus preserved and examined as perfectly as 
 if the object itself were always at hand. 
 
 In conclusion, I would impress upon all who wish successfully to 
 practice the art of Photography, the necessity of always employing pure 
 chemicals and not allowing themselves to be led away by the apparent 
 cheapness of inferior articles, as a single impurity is often enough to spoil 
 what would otherwise be a good result. Another circumstance to which 
 too much attention cannot be paid is, the necessity of extreme cleanliness ; 
 never take it for granted that any thing is clean unless you have yourself 
 cleaned it, and remember that what is clean to other people must often 
 be considered dirty by the photographer. 
 
72 
 
 EQUIVALENT WEIGHTS 
 
 OF THE SUBSTANCES MOST COMMONLY EMPLOYED IN PHOTOGRAPHY 
 
 ELEMENTARY. 
 
 Barium . . . , 
 
 68 
 
 Iron 
 
 28 
 
 Bromine .... 
 
 78 
 
 Oxygen .... 
 
 8 
 
 Chlorine .... 
 
 36 
 
 Potassium . . . 
 
 39 
 
 Gold ..... 
 
 98 
 
 Silver 
 
 108 
 
 Hydrogen .... 
 
 1 
 
 Sodium .... 
 
 23 
 
 Iodine 
 
 126 
 
 
 
 COMPOUND. 
 
 
 Acid Acetic . . . 
 
 60 
 
 Potassium Bromide 
 
 117 
 
 „ Hydrochloric . 
 
 37 
 
 „ Cyanide . 
 
 65 
 
 „ Nitric . . . 
 
 54 
 
 „ Fluoride. 
 
 57 
 
 „ Sulphuric . . 
 
 40 
 
 „ Iodide . 
 
 165 
 
 Ammonia .... 
 
 17 
 
 Silver Bromide . . 
 
 186 
 
 Ammonium Chloride 
 
 53 
 
 „ Chloride . . 
 
 134 
 
 „ Iodide . 
 
 143 
 
 „ Cyanide . . 
 
 144 
 
 Barium Chloride . 
 
 104 
 
 „ Iodide . . . 
 
 234 
 
 Baryta Nitrate 
 
 130 
 
 „ Nitrate . . 
 
 170 
 
 Gold Chloride . . 
 
 304 
 
 Sodium Chloride 
 
 59 
 
 Iron Nitrate . . . 
 
 90 
 
 Soda Carbonate . . 
 
 53 
 
 „ Sulphate ( cryst.) 
 
 139 
 
 „ Hyposulphite . 
 
 79 
 
73 
 
 COMPARATIVE TABLE OF ENGLISH AND:^ 
 FRENCH WEIGHTS AND MEASURES. 
 
 GRAINS. 
 
 1 Pound Avoirdupoise . . . 7000 
 
 1 Ounce ditto . . . . 437.5 
 
 1 Pound Troy .... 5760 
 1 Ounce ditto .... 480 
 
 Gramme . . . . . 15.432 
 
 Decigramme . . . . 1.5432 
 
 Centigramme . . . . 0.15432 
 
 Milligramme . . . . 0.015432 
 
 INCHES. 
 
 36 
 
 39.37079 
 3.93708 
 0.39370 
 0.03937 
 
 Imperial Gallon 
 Ditto Pint 
 Ditto Ounce 
 Cubic Inch 
 Litre . 
 Decilitre 
 
 Yard 
 
 Metre 
 
 Decimetre 
 
 Centimetre 
 
 Millimetre 
 
 CUBIC INCHES. 
 
 211.214. 
 34.65925 
 1.7329625 
 1. 
 
 61.02525 
 6.10252 
 
 GRAINS OF 
 DISTILLED WATER 
 
 70000 
 8750 
 437.5 
 252.458 
 15432. 
 154a8 
 E 
 
74 
 
 TABLE OF CONTENTS. 
 
 Page. 
 
 Introduction iv. 
 
 M. Le Gray's Negative Wax Paper Process 5 
 
 Waxing the Paper 5 
 
 Iodizing the ditto 6 
 
 Giving Sensibility to ditto 8 
 
 Exposure in the Camera 10 
 
 Development of the Image 11 
 
 5, Fixing the Negative 12 
 
 The Editor's Negative Wax Paper Process 15 
 
 Mr. Howe's ditto ditto 13 
 
 Mr. Crook's ditto ditto 16 
 
 Negative Process on Unwaxed Paper 18 
 
 Mr. J. Stewart's Process 19 
 
 Negative Albumenized Paper 24 
 
 Process as used at the Greenwich Observatory 25 
 
 Negative Gelatine Paper 26 
 
 Alcoholic Solutions for Negatives 27 
 
 Notes to Negative Processes 28 
 
 Negatives by Collodion on Glass 29 
 
 Preparation of Collodion 33 
 
 „ Manner of Coating the plate with ditto 37 
 
 Giving Sensibility to the Plate 38 
 
 „ Development of the Picture 40 
 
 Fixing the Picture 42 
 
 Negatives by Albumen on Glass 45 
 
 Preparation of Positive Paper 49 
 
 Positive Albumenized ditto 52 
 
 Printing the Positive Picture 52 
 
 Fixing the ditto ditto 53 
 
 Positives by Chrysotype Process ^ . 56 
 
 Positives on Glass by Collodion 58 - 
 
 Albumen 60 
 
 Process for Copying Microscopic Objects 61 
 
 Stereoscopic Pictures and the manner of obtaining them 62 
 
 Table of Equivalent Weights 72 
 
 Comparative Table of Weights and Measures 73 
 
 Catalogue of Apparatus and Chemicals 75 
 
75 
 
 CATALOGUE 
 
 OF 
 
 PHOTOGRAPHIC APPARATUS, 
 
 ©iimical prrpatattonsf $c jMatemljS, 
 
 MANUFACTURED AND SOLD BY 
 
 RICH'>* WILLATS, 
 
 (LATE T. & R. WILLATS,) 
 OPTICIAN AND PHILOSOPHICAL INSTRUMENT 
 MAKER, 
 
 28, IRONMONGER LANE, 
 
 (removed from 9 8, cheapside,) 
 XiON-DOM*. 
 
 Pig. 1. 
 
 £ s, d. 
 
 Improved Shifting Back Camera, with Achromatic lens, 3 in. 
 in diameter, mounted in brass sliding tube, with dia- 
 phragms to take pictures 10 by Sin. . fig. 1. 10 10 0 
 
 Ditto ditto with rackwork adjustment and double slide, Fig. 2, 
 
 to hold two prepared papers J*!! 10 & 12 0 0 
 
76 
 
 £ s. d. 
 
 Ditto ditto with Achromatic lens, sliding adjustment to take 
 
 pictures 6 by 7 in. . . . £5 & 6 0 0 
 
 Ditto ditto with Achromatic lens to take pictures 5 by 4 in. 2 10 0 
 
 Fig. 2. 
 
 Improved Shifting Back Camera, with best double combination 
 Achromatic lenses and diaphragms, to take Pictures 
 8i by 6J in. . . £14 14s. & 18 18 0 
 
 Ditto ditto to take 6i by 4f in, . 10 10 & 12 12 0 
 
 Ditto ditto to take pictures 4 by 3 in. . . . 5 15 0 
 
 Photographic Camera, with brass sliding front and miniscus 
 
 lens for obtaining pictures on paper, 4 by 4 in. .110 
 Ditto ditto with brass sliding front and Achromatic lens 15 6 
 
 Fig. 3. 
 
 Photographic Camera, with rack work adjustment and Achro- 
 matic lens fig. 3 . , from £1 15s., to 2 2 0 
 
77 
 
 Fig 4. £ *• ^» 
 
 Folding Cameras with single Achromatic lens fig 4 from 5 5 0 
 
 Folding Camera of the best make, with Achromatic lens in 
 rackwork front, with double paper holder and 1 holder 
 for glass plates, to take pictures 10 by 8 in., perfect to 
 the edges . • • • . 16 16 0 
 
 Ditto ditto made to order, to suit lenses of various focal lengths. 
 
 R. Willats* Portable Camera with flexible cloth body, angular, 
 vertical, and horizontal adjustments, with Achromatic lens 
 and rackwork front to take pictures, 10^ by 8 in. fig. 5. 11 11 0 
 
 Ditto ditto with angular adjustment and sliding tube . 9 9 0 
 
 This form of Camera, shown at the Exhibition of 1851, is so constructed as to 
 admit of being packed into a very small space and extremely convenient for Travellers 
 being easily carried and not liable to derangement. 
 
 E 2 
 
78 
 
 Fig. 6. £ ^• 
 
 * Willats' Improved Camera with double Achromatic combina- 
 tion lenses, to take pictures 4 by 3, adapted for por- 
 traits, with screw adjustment « . fig- 6. 6 0 0 
 
 Fig. 7. 
 
 * Willats' Improved Camera, with single achromatic lens and 
 
 revolving diaphragm to take pictures 4 by 3, 3J by 2f , 
 
 and 2i by 2 in. . • . fig. 7 3 10 0 
 
 Cundell's Camera with double combination of miniscus lenses, 
 
 to take a picture, 7J by 6J in., as described in the 
 
 Philosophical Magazine" . . .550 
 
 A pair of Cameras with double combination Achromatic lenses, 
 
 arranged for taking Stereoscopic Portraits, 2 J by 2, 3^ by 
 
 2|, and 4 by 3 in. 
 Microscopic Copying Cameras made to suit Table Microscope. 
 
 * These forms of Camera are weU adapted for taking portraits by the collodion process. 
 
 12 0 0 
 
79 
 
 £ s, cL 
 
 Complete set of Apparatus and Chemicals to take Collodion 
 
 Pictures on glass, in a case . . from 3 3 0 
 
 Complete set of Photographic Apparatus, including Chemi- 
 cals, &c., for Paper Process, in case, to take pictures 4 by 
 4 in. . . . . from 3 3 0 
 
 Ditto ditto in stout packing case with lock and key to take pic- 
 tures 5 by 4 in. . . . . .550 
 
 Ditto ditto ditto, with extra dark slide for collodion process. 
 
 Chemicals and Apparatus . . .660 
 
 Ditto ditto, with double dark paper slide. Chemicals &c., in 
 
 case, with lock and key, to take 6 by 7 in. . . 10 10 0 
 
 Ditto ditto ditto with dark slide for collodion process. Chemi- 
 cals and Apparatus complete, to take 6|by7^in. .13 0 0 
 
 Larger sets fitted up to order. 
 
 Fig. 10. 
 
 Copying frames and glass for obtaining positive photographs 
 
 with padded backboard and pressure bai^, fig, 8, 5/6 & 0 1 6 
 
80 
 
 £ s, d. 
 
 Copying Frame, with sliding lid for ditto . fig. 9. 0 10 6 
 
 Johnstone's Improved ditto, with hinged back, so that the 
 progress of the process can be conveniently viewed with- 
 out disturbing the papers . fig. 10, from 0 16 0 
 Very strong pressure frames with screws at back . from 0 16 0 
 
 Tin vessels for heating photographic drawings . fig. 11. 
 
 0 
 
 5 
 
 0 
 
 Photographic Etnas . . . fig. 12, each 
 
 0 
 
 5 
 
 6 
 
 Flat Porcelain Pans for washing ^nd setting pictures Is. 6s. & 
 
 0 
 
 2 
 
 6 
 
 Large ditto, 12 by 10 inches .... 
 
 0 
 
 4 
 
 6 
 
 Extra ditto ditto 
 
 0 
 
 7 
 
 6 
 
 Polished Glass Dishes for ditto ditto . . from 
 
 0 
 
 14 
 
 0 
 
 Gutta Percha Dishes in sets of 4 
 
 1 
 
 5 
 
 0 
 
 Gutta Percha Dipping Baths for collodion process, fig. 2, p. 39, 
 
 
 
 
 Larger Sizes to Order. 3s.j 4s. 6d. & 
 
 0 
 
 6 
 
 6 
 
 Glass Dipper for above .... 
 
 0 
 
 1 
 
 0 
 
 Flat Glass Baths .... from 
 
 0 
 
 5 
 
 0 
 
 Air Pumps and Exhausting Syringes various 
 Stewart's Apparatus for preparing paper . 
 
81 
 
 Fig. 13. 
 
 Fig. 14. 
 
 Tripod Stands, or levelling stands 
 Best ditto ditto . 
 
 fig. 14 
 fig. 13 
 
 £ s. 
 0 5 
 0 10 
 
 Fig. 15 
 
 fig. 15, a 
 
 1 16 
 
 2 2 
 0 16 
 
 Camera Stands, French Polished Mahogany- 
 Ditto ditto, jointed legs ditto 
 
 Common ditto ditto, with ring top . . from 
 
 Portable ditto ditto . fig. 16. 21s., &; 
 
 Ditto ditto, fig. 17, very firm . . from 
 
 R. Willats* Improved Ball and Socket Tripod Camera Stand, 
 very portable, and by a new and simple arrangement of 
 the screw & wedge, the ball can be firmly clamped, capa- 
 ble of holding a heavy camera without liability of shifting 2 10 0 
 
82 
 
 Fig. 16. 
 
 Head Rests, best portable 
 
 Willats' Improved Johnstone's Head Rest 
 
 Fig. 17. 
 
 £ s.d. 
 .076 
 
 . 1 10 0 
 
 Fig. 18. 
 
 Boxes of various sizes for holding glass plates, price according 
 to finish. 
 
 Fig. 19. 
 
83 
 
 £ s. d. 
 
 Portable Still, with worm and tub for the distillation of water 
 
 on common fire . . fig. 19, 1 gallon 110 
 
 Ditto ditto, best make . . . .15 0 
 
 Ditto ditto, best make . . .2 gallons 2 0 0 
 
 Improved Camel's Hair Brushes prepared expressly for Photo- 
 graphic purposes ?. . . round 0 10 
 Ditto ditto . . . . flat 0 1 6 
 Ditto vditto larger sizes . . 2s. 6d. & 0 3 6 
 Glass tube with silver wire for Buckle's cotton wool brush .026 
 Velvet Buffs for polishing glass plates . each 1/10 & 0 3 6 
 Turner's superior Paper, made expressly for Photographic 
 
 purposes .... per quire 0 
 
 Ditto ditto . . . . quarto 0 
 
 Whatman's (selected) . . per quire folio 0 
 
 Ditto ditto .... quarto 0 
 
 Cansons Freres' negative paper, best make per quire 0 
 
 Ditto ditto positive . . . .0 
 
 Papier Joseph 
 
 Waxed Paper to order 
 
 Stout White Wove Blotting Paper 
 
 Pink ditto ditto . 
 
 Patent Glass Plates, 3J by 2| . ' . per doz. 
 
 4 by 3 
 H by 3i 
 
 5 by 4 
 Larger sizes cut to order. 
 
 Best selected Glass Plates of the above sizes will be rather 
 higher in price. 
 
 Plate Glass Slabs of various sizes . Is., 2s., 3s. & 
 
 Glass Spirit Lamps . . .2s. 6d., 3s. 6d. & 
 
 Shallow Glass Troughs of various sizes . ' . 
 Glass Tubes for Reeves' Albumen Process . .006 
 
 Steaming Apparatus for ditto ditto, made to order 
 Porcelain Evaporating Dishes . . . 9d. & 0 1 0 
 
 Finest Cotton Wool for Brushes . . per oz. 0 0 3 
 
 Silver Leaf . . . . per book 0 16 
 
 Mastic Varnish . . . per bottle 0 1 0 
 
 1 6 
 
 1 6 
 
 1 6 
 
 2 0 
 
 2 6 
 
 3 6 
 
 5 0 
 5 0 
 
84 
 
 £ s. d. 
 
 Thermometers, Warranted • , from 0 2 6 
 
 Retort and Receiver Stands, glass retorts, receivers and flasks, &c. 
 
 Glass Funnels and Stirring Rods 
 
 Glass Triangle for pressing down paper in solutions 
 
 Graduated Glass Measures . . . Is. 4d. & 0 1 6 
 
 Mortars and Pestles • . . . . 
 
 Pipettes . . . . . 6d. & 0 0 8 
 
 Scales and Weights, common . . . .036 
 
 Ditto ditto, glass pans, best, . . . . 'O 18 0 
 
 Tin Plate for waxing proof . . . 6d. & 0 1 0 
 
 Glass stoppered Bottles for holding chemical preparations 
 
 of various sizes . . from each 0 0 6 
 
 Yellow glass stoppered bottles of various sizes. 
 
 Fig. 20. 
 
 Wheatstone's Reflecting Stereoscope, fig. 4, page 65 . ♦ 
 
 Ditto Refracting ditto, with diagrams, fig. 9, page 69 15s. & 1 1 0 
 Japanned tin ditto, with diagrams . . fig. 20 0 5 0 
 
 Photographic Views in variety . from each 0 4 6 
 
 Ditto ditto, for Stereoscope . ,,030 
 
 Collodion Views for ditto . . ,,.0106 
 
 Daguerreotype Views for ditto . . „ 0 6 6 
 
 Passe Partout, or Skeleton Frames, for mounting Photo- 
 graphs, in variety . . each, from 0 0 6 
 Morocco Leather Cases, lined with Velvet, gilt Mats and best 
 Glass for Portraits ; according to size. 
 
85 
 
 Pure Chemicals, 
 
 FOR PHOTOGRAPHIC PROCESSES ON PAPER OR GLASS. 
 
 
 
 
 I? 
 
 X> 
 
 
 
 
 
 * per oz. 
 
 0 
 
 1 
 
 0 
 
 
 
 
 \j 
 
 A 
 yJ 
 
 
 — — . r^5l11lP TJIITP 
 
 vJclillO. L/l.HC • • 
 
 
 J? 
 
 0 
 
 5 
 
 0 
 
 
 
 
 0 
 
 0 
 
 2 
 
 ~— NitriCj pure • 
 
 
 ?> 
 
 n 
 
 u 
 
 Q 
 
 3 
 
 ——— 1^ i Li atJ. Ui IClLlL/ • 
 
 
 J J 
 
 0 
 
 0 
 
 4 
 
 Pyro-Gcillic * « 
 
 
 . per dram 
 
 Q 
 
 
 Q 
 
 SucciniCj pure . . 
 
 
 • |>er oz. 
 
 
 5 
 
 0 
 
 — SulpliiiriCj pure • 
 
 
 • jj 
 
 n 
 u 
 
 0 
 
 2 
 
 -A. Hi mo 11 19, Solution . . 
 
 
 per oz., 2d. Sc 
 
 n 
 U 
 
 A 
 
 u 
 
 o 
 
 
 
 
 0 
 
 0 
 
 Q 
 
 
 
 l>ei oz. 
 
 0 
 
 0 
 
 3 
 
 V/()110U1UH • . » 
 
 
 
 n 
 
 
 0 
 
 ^ A^illofo^ VhT»ovkOT»i:i/~l i^/^lii^^iT^n 
 VV llidts picpdlcU. V^UIIOUIOII . 
 
 
 >? 
 
 A 
 U 
 
 1 
 
 1 
 
 0 
 
 Aiciiei b UlttO UlllO 
 
 
 
 A 
 U 
 
 A 
 
 »j 
 
 A TSIPTl IPflf Pfl flitfn 
 
 
 
 0 
 
 
 0 
 
 Rectified. Sulphuric Ether 
 
 
 
 A 
 
 o 
 
 1 
 1 
 
 A 
 
 ACcLdLe 'J I J-itrdLl • 
 
 
 • pel u^. 
 
 A 
 
 yj 
 
 A 
 
 V 
 
 o 
 
 
 
 )? 
 
 A 
 
 A 
 
 \f 
 
 u 
 
 
 
 7? 
 
 0 
 
 Q 
 
 6 
 
 
 
 ?7 
 
 0 
 
 0 
 
 u 
 
 Od.iL UJ VjlUiU Ul ijxli U yjL • 
 
 
 • P"^ UU Li • 
 
 Q 
 
 
 (\ 
 
 \J 
 
 TT»r»n ArmTiriTiin r^ifr'nfp 
 
 
 pel oz. 
 
 Q 
 
 
 () 
 
 _ Snlt^Vififp v»iivp 
 
 ———^ CLllJJUCllCj . • 
 
 
 
 0 
 
 Q 
 
 2 
 
 Proto Nitrate Solution 
 
 
 
 
 
 
 Iodine, pure resublimed 
 
 
 
 0 
 
 3 
 
 0 
 
 Syrup of the Iodide Iron 
 
 
 
 0 
 
 1 
 
 6 
 
 Lime Chloride, pure . 
 
 
 
 0 
 
 0 
 
 6 
 
 Potassium Bromide, pure 
 
 
 
 0 
 
 5 
 
 0 
 
 Ferro Cyanuret, Pure . 
 
 
 » 
 
 0 
 
 0 
 
 6 
 
 Ferro Sesquicyanuret 
 
 • 
 
 • J? 
 
 0 
 
 2 
 
 6 
 
 Fluoride . 
 
 
 
 
 
 
 This, if required for export, can be had with Iodizing preparation separate. 
 
86 
 
 
 
 £ 
 
 s. 
 
 d. 
 
 Potassium Cyanide . 
 
 
 0 
 
 I 
 
 0 
 
 ^ Pure 
 
 
 0 
 
 3 
 
 6 
 
 Iodide, Pure 
 
 
 0 
 
 3 
 
 0 
 
 — Nitrate, pure 
 
 „ 
 
 0 
 
 0 
 
 3 
 
 Silver Nitrate Pare, crystalised 
 
 
 0 
 
 5 
 
 6 
 
 Potassio Cyan. Silver Solution 
 
 yy 
 
 0 
 
 1 
 
 6 
 
 Oxide 
 
 yy 
 
 0 
 
 8 
 
 a 
 
 Silver Ammonio Nitrate Solution 
 
 yy 
 
 0 
 
 1 
 
 0 
 
 Soda Hyposulphite . 
 
 per lb. 
 
 0 
 
 3 
 
 0 
 
 ■ ~ • . . 
 
 per oz. 
 
 0 
 
 0 
 
 3 
 
 Sodium Chloride, pure 
 
 • 
 
 0 
 
 0 
 
 6 
 
 Perfectly pure Animal Charcoal 
 
 per oz. 
 
 0 
 
 0 
 
 8 
 
 Virgin Wax 
 
 yy 
 
 0 
 
 0 
 
 4 
 
 Finest Tripoli 
 
 
 0 
 
 0 
 
 6 
 
 Distilled Water 
 
 . per gall. 
 
 0 
 
 1 
 
 0 
 
 Pure Gelatine 
 
 
 0 
 
 0 
 
 6 
 
 Sugar of Milk 
 
 
 0 
 
 0 
 
 6 
 
 Pale Laquer 
 
 . per bott. 
 
 0 
 
 1 
 
 0 
 
 Willats' Preparation for making Iodized Paper 
 
 by one appli- 
 
 
 
 
 cation or wash . 
 
 . per bott. 
 
 0 
 
 2 
 
 6 
 
 The above Prices for Chemicals are subject to constant variation. 
 
 Photographic Apparatus of all kinds made to Order. 
 
 For further particulars of Daguerreotype and Photogrophic Ap^ 
 paratuSy see Willats* Illustrated Catalogue^ Part 1, Photography, 
 price Fourpence, or by Post, Sixpence. 
 
 Foreign Orders accompanied by a Remittance, or Order for Payment in 
 London promptly attended to. 
 
 THE GREATEST CARE TAKEN IN PACKING. 
 
 Alfred Boot, Printer, Dockhead, Southwark. 
 
Rich'' Willats, 
 
 dDftiriiiii, 
 
 No. 28, IRONMONGER LANE, OHEAFSIDE, 
 
 (Remo7)ed from 9S, Cheapside.) 
 
 spectaoz.es 
 
 To suit all ages and sig-hts, glazed with the finest BRAZILIAN 
 PEBBLES, or BEST OPTICAL FLINT GLASS. 
 
 The gi^eatest care is taken by Rich^- Willats that the Pebbles, 
 or Glasses, are correctl}' worked and polished, as well as suited to the 
 sight of the Purchasers. 
 
 A pair of useful Blue Steel Spectacles, with best Optical Flint 
 Lenses, to suit any sight, either for Ladies or Gentlemen, for 
 
 FIVE SHIX.I.INGS. 
 
 Lighter and more highly finished BLUE STEEL SPECTACLES, 
 at 66-., 7s., €d. and IZs, €d. 
 
 The very best Elastic Blue Steel Spectacles that can be made, 
 mounted with finest Brazil Pebbles (to order if preferred), %Ss, 
 
 An extensive Assortment of solid Gold and Silyer Spectacles, 
 Hand Folders, and Eye Glasses. Improved Hand Folders 
 to clip on the Nose, of various forms and materials. 
 
 A LARGE STOCK OF VERY SUPERIOR 
 
 ACHROMATIC OPKRA GIiASSES, 
 
 RACE GLASSES, AND SMALL OPERA GLASSES, 
 
 FOR THE POCKET. 
 
 A THREE-DRAW ACHROMATIC TELESCOPE 
 
 For 12s., or with Sun Shade, 16s. 
 
 MILITARY, NAVAL, AND IMPROVED ACHROMATIC 
 ASTRONOMICAL TELESCOPES. 
 
 Oxy-Hydrogen Microscopes. Polariscopes. Camera Lucedas. 
 Polarising Apparatus. 
 
WILLATS' PORTABLE ACHROMATIC 
 MICROSCOPES, 
 
 In a Mahogany Case, with Apparatus complete, £5 5^ Magnifying 
 Power 8,000 times. Larger and more complete Achromatic Micros- 
 copes, from £8 85. upwards. 
 
 DISSOLVING VIEWS. 
 
 Apparatus for exhibiting the Dissolving Views as shewn at the Royal 
 Polytechnic Institution, with the Hydro-Oxygen Light; or on a smaller 
 scale, suitable for Private Use, Schools, &c., illuminated by Patent 
 Argand Lamps, and constructed on the most improved Principles, by 
 R. WiLLATS, who has on hand a large Collection of PHANTASMA- 
 GORIA and MAGIC LANTERNS, together with Slides for illustra- 
 ting Lectures on Natural History, Botany, Geology, and Astronomy. 
 
 COMIC SLIDES IN GREAT VARIETY 
 
 DRAWING INSTRUMENTS 
 
 In Pocket Cases from 5s. to 40s. In Mahogany French Polished Cases, 
 21s. to £10 10s. 
 
 MEDICAL GALVANISM AND ELECTRICITY. 
 
 R. WiLLATS respectfully solicits the attention of the Medical Profes- 
 sion to his ELECTRO-MAGNETIC MACHINES, combining Com- 
 pactness, Portability, and Power, as constructed by him for St. Thomas's, 
 Guy's, and the pi. .cipal Metropolitan and Provincial Hospitals, for the 
 application of Medical Electricity. Complete in Case, with Battery and 
 Directions, £3 3*. 
 
 FRICTIONAL ELECTRIC MACHINES 
 
 of every Form and Dimension. 
 Smee's, Daniell's, Groves', and Cruikshank's Batteries. 
 
 ELECTRO-METALLURGICAL APPARATUS. 
 
 Single Cell Apparatus ; Precipitating Troughs and Batteries ; Appa- 
 ratus for Electro- Plating ; Binding Screws; Porous Jars; Plaster Casts ; 
 Wax Moulds ; and every Material required in the varied Processes, 
 
 METEOROLOGICAL INSTRUMENTS. 
 
 Upright or Pediment Barometers; Best Dial Faced Barometers; 
 Marine Barometers ; Standard Barometers ; Standard and Plain Thermo- 
 meters; Day and Night Registering Thermometers; Sixe's Thermo- 
 meter ; Chemical, Botanical, Medical, Brewing and Bath Thermometers. 
 
 Every Description of Apparatus for practically pursuing the various Branches of 
 Natural Philosophy, of very superior Workmanship 
 
 MANUFACTURED AND SOLD 
 
 BY KICHAKD WILLATS, 
 28, IRONMONGER LANE, CHEAPSIDE, LONDON- 
 
JUST PUBLISHED, 
 WILLATS'S SCIENTIFIC MANUALS. 
 
 SCIENTIFIC MANUAL, No. 1. 
 
 PLAIN DIRECTIONS FOR OBTAINING PHOTOGRAPHIC 
 PICTURES on PAPER, CALOTYPE, Energiatype, and other 
 
 Processes, including the Chrysotype, Cyanotype, Catalasisotype, 
 Chromotype, Gaudinotype, etc., with the latest improvements. 
 
 FOURTH EDITION, WITH ADDENDA, PART I. 
 
 Price One Shilling, or hy Post One Shilling and Fourpence. 
 
 PART II. 
 
 PLAIN DIRECTIONS FOR OBTAINING PHOTOGRAPHIC 
 PICTURES upon WAXED and ALBUMENIZED PAPER and 
 
 GLASS by COLLODION and ALBUMEN, &c., including a third 
 
 EDITION of LE GRAY'S TREATISE ON PHOTOGRAPHY, a 
 description of the STEREOSCOPE and the manner of taking 
 Pictures suited for it. Also the process for Copying MICRO" 
 
 SCOPIC OBJECTS. 
 
 Price, Two Shillings, or by Post Tivo Shillings and Sixpence. 
 
 SCIENTIFIC MANUAL, No. II. 
 
 PRACTICAL HINTS ON THE DAGUERREOTYPE, being simple 
 Directions for obtaining Portraits, Views, Copies of Engravings, and 
 Drawings, Sketches of Machinery, etc., by the Dagerreotype pro- 
 cess ; including the latest Improvements in Fixing, Colouring, and 
 Engraving the Pictures ; with a Description of the Apparatus. 
 Illustrated with Engravings. 
 
 THIRD EDITION 
 
 WITH A SUPPLEMENT CONTAINING AMERICAN PROCESS. 
 
 Price One Shilling, or by Post One Shilling and Fourpence. 
 
 SCIENTIFIC MANUAL, No. III. 
 
 MICROSCOPIC MANIPULATION, containing the Theory and Plain 
 Instructions for the use of the Microscope ; including the best 
 Methods for the Mounting of Objects, and a Review of the impor- 
 tant Discoveries effected by this Instrument. Illustrated by 
 Wood-cuts. Price One Shilling and Sixpence, or by Post Two 
 Shillings 
 
SCIENTIFIC MANUAL, No. IV. 
 
 A POPULAR GUIDE TO THE ELECTROTYPE, containing 
 Concise and Simple Instructions in the various processes of Electro 
 Metallurgy, with the Art of Moulding in Plaster, Wax, Fusible, 
 Metal, etc. Parts 1 and 2. Price One Shilling, or hy Post One 
 SMUing and Fourpence each. 
 
 Other Numbers of this Series of highly popular Manuals will shortly 
 be published. 
 
 A PRACTICAL TREATISE ON MEDICAL ELECTRICITY, 
 containing a Historical Sketch of Frictional and Voltaic Electricity, 
 as applied to Medicine; with Plain Instructions for the use of 
 Electric, Galvanic, and Electro-Magnetic Instruments; and em- 
 bracing an account of the most recent Researches of Matteuci. 
 Illustrated by Wood-cuts. Price Two Shillings, 
 
 A THERMOMETRICAL TABLE, on the Scales of Farenheit, . 
 Reamur, and (Centigrade ; comprising the most remarkable Pheno- 
 mena connected with Temperature in relation to Climatology, Phy- 
 sical Geography, Chemistry, and Physiology. By Alfred S. Taylor. 
 Price, in Sheet, with Explanatory Pamphlet, Is. 6d.; or Mounted 
 on Rollers, 4s. 6d. 
 
 A GUIDE TO THE MAGIC LANTHORN AND DISSOLVING 
 VIEW APPARARATUS, including Directions for the Application 
 of the Oxy-Hydrogen Light to Optical Purposes. Price Sixpence, 
 or by Post JEightjyence. 
 
 IN THE PRESS. — A NEW EDITION. 
 
 WILLATS'S 
 
 ILLUSTRATED CATALOGUE 
 
 OF 
 
 PHOTOGRAPHIC, 
 
 AND 
 
 Just Published, Price Fourpence, per Post Sixpence, 
 
 PART I., 
 
 PHOTOGRAPHY.