[The original article in Annals of Science in 1971 had footnotes at bottom of each page, but for this on-line presentation of the full text those footnotes are all moved together at the end of the article. Reference, in square brackets, within the text to the footnote numbers are hypertext-linked in both directions]
THIS paper reports Sir John Herschels use of gallic acid in his photographic experiments prior to W. H. F. Talbots discovery, in September 1840, of the use of that agent as a latent image developer. The later involvement of Herschel in Talbots legal action against a professional photographer named James Henderson in 1854 is described, and some recently-found correspondence between Talbot and Herschel, in the years 1853 and 1854, is fully reported.
Gallic acid and the Calotype process
During 1841, a photographic patent was sealed by W. H. F. Talbot (1800-1877). This was the patent for his Calotype process, a process of considerable importance in the evolution of photography. Unfortunately, the period of fourteen years, 1841 to 1854, over which the patent extended, was not a happy one for the growth of photography in England. To many persons during those years it seemed as if Talbot believed that he held a patent for photography in its entirety; indeed there is much to justify them in that view. We have seen in Part II of J. B. Reade and the Early History of Photography, (Ann. Sci. 1971, 27, 47-83) how this unhappy situation regarding the patents came to a head in the years 1852-1854. At this time the Rev. J. B. Reade was brought forward in an attempt to show that Talbots patent was invalid; the claim was made that Reade had used gallic acid in photographic experiments in 1839, two years before Talbot sealed his Calotype patent. This work of Reades, it was alleged, was the real source of the discovery of the Calotype process; Talbot having been led to the use of gallic acid after hearing about Reades experiments in April 1839. This agitation over the patents during the early 1850s would have had comparatively little significance today, except for the fact that it has greatly influenced historians views of the discovery of development and of the latent image.
As we have already seen, Talbot did indeed learn in April 1839 that J. B. Reade had used gallic acid; but there is no particular reason to suppose that this had any direct influence upon Talbot's ideas about the development of a latent image. J. B. Reades involvement in events leading to Talbots discovery of the Calotype process became established in the history of photography to the exclusion of any other influence. Reade's appearance at the Talbot v. Laroche trial, in December 1854 - an event well recorded in photographic literature - was responsible for this. There was, however, another person who could well have been called to give evidence about his own early use of gallic acid; this was Sir John Herschel. But in fact Herschel did not appear in this case; consequently he has not become established in the history of photography, as has Reade, as having influenced Talbots use of gallic acid.
Sir John Herschel and gallic acid
Herschels name had, however, been brought forward in this respect before the Laroche trial; this was during the patent agitation of 1852 and, in particular, in May 1854, when Talbot was seeking to obtain an injunction to stop a London professional photographer, James Henderson, from using the Collodion technique for portraiture. The journal Notes and Queries took some interest in photography at this period, and in their issue for July 8, 1854, they published three items related to the photographic patent case of Talbot v. Henderson. These items were, firstly, a letter to Talbot from J. B. Reade concerning a statement, by Talbot, that Reade had not used gallic acid as a developer in 1839; and secondly, as representing Talbots side of the case, Notes and Queries printed two affidavits that had been sworn by Sir David Brewster and by Sir John Herschel. Herschels affidavit was in reply to a statement, made by Robert Hunt and Charles Heisch, that he had published a remark about the use of gallic acid prior to Talbots work on the Calotype process. Herschel stated, in effect, that he had indeed made such a remark in a paper that he had read to the Royal Society in February 1840; but, he said, this was a minor remark which would not have had any influence upon Talbots discovery of the development of the latent image. The printing of this affidavit in Notes and Queries is the major published reference to the possibility of there being a link between a remark made by Herschel in 1840 and the subsequent discovery, by Talbot, of the Calotype process.
This fact, that Herschel published a minor remark early in 1840 about gallic acid, has been ignored by historians, although there is no reason why this should not have had at least as much influence upon Talbot as a minor remark about an experiment of J. B. Reades. Of course, the story of Reade and gallic acid became historically important due to the events of the 1850s. At that time many persons in the photographic world would have been aware that experiments had been made with gallic acid by J. B. Reade; in contrast, published references to Herschel and gallic acid seem to be limited to little more than the publication in Notes and Queries just mentioned, to two articles in the Art Journal during 1852 and 1854, and Jabez Hoggs Practical Manual of Photography of 1853. 
Attention was drawn to Reade because of his appearance at Talbot v. Laroche - a legal action which became legendary to professional photographers, and which entirely overshadowed the Henderson injunction hearing: this is obviously the main reason why Herschels use of gallic acid prior to 1840 has been overshadowed by J. B. Reades use of that substance. The Reade/Talbot legend has been persuasive because of the rather nice story about their conversations with Andrew Ross.
Herschel, in his affidavit published in Notes and Queries, specifically states that he did not influence Talbots work; but do we have to take his word for this? At the very least, it is surely likely that his remark would have had as much influence on Talbot as an account, by Ross, of Reades experiment.
There appear, in fact, to be just two recorded occasions on which Herschel specifically mentions the use of gallic acid, as a sensitizing agent, prior to Talbots experiments of September 1840. Firstly, Herschel wrote to Talbot on the 28 February 1839: 
I had been trying various modes of rendering nitrated paper more sensitive - till I read your most curious account of your process, which opens up quite a new view of the subject, and is altogether one of the most singular things I ever saw. You must have hunted down the caprices of these combinations with great perseverance and patience. When I read it I gave up further trials,  your processes being very simple and complete - I had most hopes of the Gallate of Silver, which is affected by light very differently from its other salts....
Secondly, Herschels paper On the Chemical Action of the Rays of the Solar Spectrum... and on some Photographic Processes which was read at the Royal Society in February 1840, and published that summer in the Philosophical Transactions  states:
My first attention was directed to the discovery of a liquid, or emulsion, which by a single application, whether by dipping, or brushing over, should communicate the desired quality [of increasing the sensitiveness of photographic paper]. The presence of organic matter having been considered by some late chemists an essential condition for the blackening of the nitrate of silver, I was induced to try in the first instance a variety of mixtures of such organic soluble compounds as would not precipitate that salt. Failing of any marked success in this line, (with the somewhat problematic exception of the gallic acid and its compounds,) the next idea which occurred was that of introducing organized salts of silver into the pores of paper, by first washing it over with an organic, soluble, precipitable salt, with alkaline base, and then with nitrate of silver. Here also no distinct result was obtained.
We must primarily study the events of 1839 and 1840 if we wish to clarify our understanding of the discovery. of the latent image and development. However, the discussion concerning Herschels two remarks given above, and regarding the relationship between his and Talbots work of 1839 and 1840, will be left until some later events have been reported; this is some correspondence between Sir John Herschel and Fox Talbot that has recently come to light, and that is of considerable relevance to this subject, even though it is of the later - 1854 - period. The correspondence reveals how it came about that Herschel made his affidavit during 1854 about his early use of gallic acid, and it is also of special interest because of the light that is cast upon the relationship between him and Talbot.
Talbot applied to Herschel in 1853 for some assistance over his difficulties with some London professional photographers, who were using the wet-collodion technique for portraiture; Talbot, and his patent licensees, considered this to be an infringement of the Calotype patent. Herschel therefore became involved in the case of Talbot v. Henderson; the preceding article (Ann. Sci., March 1971, pp. 47-83) has already given the background to the Calotype patent cases, and we now deal more specifically with the Henderson injunction of 1854.
Talbot v. Henderson 
On 27 April 1854 a Mr. Arthur Church visited a photographic studio at 204 Regent Street, London. After asking the woman who approached if paper portraits could be taken, he was shown upstairs to the glass studio. There his portrait was taken by the photographer, James Henderson. Well satisfied with his visit, he returned to the studio two days later, paid one guinea, and after casually asking some questions about the technique - the wet collodion process - that had been used, he left with his paper portrait. Mr. Church, who was Assistant to Dr. Hofmann, the Professor of Chemistry at the Royal College of Chemistry, had, in fact, been sent to Hendersons studio by a firm of solicitors in Lincolns Inn; consequently it was not many days afterwards that this firm, Price and Bolton, who were the Solicitors of W. H. F. Talbot, also sent one of their clerks along to Hendersons studio. This clerk, Fred Chapman, did not, of course, want his photograph taken; instead, on 6 May 1854, he required Henderson to receive a Bill of Complaint -for Henderson was alleged to have infringed Talbots Calotype patent, by using the wetcollodion process in taking portraits for sale.
We have already seen, in J. B. Reade and the early history of photography;
part II the background to the events that led up to legal action being taken against three London professional photographers - Colls, Henderson, and Laroche - at this period; and we have also seen briefly, on pp. 58-62, of J. B. Reade, Part II, how, barely one month after Arthur Church had his portrait taken, that an injunction was granted, on 26 May 1854 in the Court of Chancery, to restrain Henderson from selling paper portraits. The formal Injunction was served on Henderson (again Mr. Chapman went along) on 1 June 1854.
Henderson was enjoined to be
restrained under the penalty of five thousand pounds... from in any manner using exercising or putting in practice the invention of the plaintiff... or resembling the same or any part thereof, in the preparation of portraits... or selling any photographic portraits on paper according to, or by means of, the said plaintiffs Invention or any part thereof, until further Order of the Court.
Vice Chancellor Wood, who had heard the case on the 26 May, had expressed some doubt about the inclusion of the phrase imitating or resembling the Invention, or any part thereof ; this attitude of the Vice Chancellor must have greatly encouraged Henderson in his decision to contest the case. Henderson had already during May contacted a number of photographers who had sworn affidavits in his defence. But, of course, Talbot had also been preparing his side of the case. When the injunction was granted on 26 May, he had affidavits sworn by three persons to support him; these were by Nicolas Henneman, Sir David Brewster, and Sir John Herschel. The following correspondence,  between Fox Talbot and Sir John Herschel, can now tell us how Herschel became involved in this.
Letter No. 1, Talbot to Herschel, dated 13 November 1853.
[To] Sir J. Herschel.
Greta Bank, Keswick,
Believe me to remain,
It would appear that Herschel did not make any reply to this letter; but six months later, when Talbot found it necessary to bring an action, in Chancery, against James Henderson, Herschel received another two letters:
Letter No. 2, Talbot to Herschel, dated 15 May 1854.
[To] Sir J. Herschel.
But a knot of photographers in Regent St. and elsewhere have conspired together to upset my patent-the case comes on for argument in the Court of Chancery in a few days, when affidavits will probably be made by the opposite side that I am not the inventor of the art, or that at any rate my invention was imperfect & of no utility &c &c &c.
I am advised that 2 or 3 affidavits made by persons of high scientific eminence would outweigh in the mind of the Vice Chancellor a host of affidavits made by obscure persons who speak with little or no authority on the subject.
I have therefore asked Sir David Brewster and Profr. Wheatstone  to make affidavits in my favour which they have kindly consented to do, & if you have no objection to do the same I shall consider my case as established. I may mention that it would only be necessary for you to call at the office of my solicitor in Lincolns Inn at any hour of the day between 10 and 6 on Friday or Saturday next and sign the affidavit, which 1 hope would not be giving you too much trouble.
But since of course you would like to know first, the contents of the Document, I would send you a draught of it previously. It would state that you believe me to be the inventor of the Calotype or Talbotype process, & that you are acquainted with the principles of the Collodion process, which for reasons assigned you consider to involve the same scientific & photographic principles as mine, and to conduct to the same result finally, viz. to a positive photograph on paper.
Excuse this trouble, &
Letter No. 3, Talbot to Herschel, dated 18 May 1854.
[To] Sir J. Herschel.
Letter No. 3a, Talbots Draft of affidavit proposed for Sir John Herschel.
[Draft] Afft. of Sir J. Herschel Bart., Master of Her Majestys Mint, &c.
1. I have for many years paid much attention to optical Science, and I have written
/4. Vide another sheet./
6. I am acquainted with the principles of what has been termed the Collodion process in Photography and 1 consider it to be a useful & convenient mode of operating. By ye employment of the said Collodion process a greater rapidity of photographic action is frequently obtained, together with a greater precision & clearness in the negative image or picture.
7. The said Collodion process consists chiefly in a mode of obtaining the negative pictures upon a film or skin of iodised Collodion spread upon glass, instead of obtaining them upon a sheet of iodised Paper according to the plaintiffs invention described in the said specification.
[Items 4 and 5 are written on separate sheet:]
Items 1, 2, 3 and 4 are marked with a line down the margin. The word omitted, which heads the separate sheet, is in Talbots hand. Although a similar draft was sent to Brewster (see footnote 15) it is possible that the separate items 4 and 5 were not.
Letter No. 4, Rough Draft, Herschel to Talbot, dated 19 May 1854.
May 19, 1854. To F. Talbot.
My dear Sir,
I remain, &c.
P. S. Many thanks for the Pantheon on Steel. I read the inscription very well. by the bye, what a bald affair the Dome (above the columns) is and the flanking walls! What a noble photograph of Paris from a window in one of the houses just about to be pulled down beyond C[? ommun] Street would make!! It is certainly by a long chalk the finest building on Earth so seen.
[To] H. F. Talbot.
Letter No. 5, Talbot to Herschel, dated 20 May 1854.
[To] Sir J. Herschel.
Many thanks for your letter. 1 am very sorry to cause you so much trouble, more especially as your time is so fully and usefully occupied.
An affidavit in the Court of Chancery is a thing finished and done with, it leads to no further trouble - as there is no jury and no viva voce evidence, there is of course no cross examination. The affidavit speaks for itself and either produces an effect on the mind of the Vice Chancellor or none, as the case may be.
An affidavit is an expression of personal belief only. To put a parallel case: 1 could testify, if the occasion for it should arise, that 1 believe you to have been the discoverer of hyposulphuric [sic] acid, and of the solvent power of that acid, of the salts of silver - My testimony would not be to the fact, but to my belief of the fact. The fact itself might be quite otherwise, and yet the truth of my affidavit would be unshaken.
Of course we have proof, supported by the necessary affidavits, that the defendant in the present cause infringes my patent by selling portraits which are prima facie the same as those produced by my patent process.
His defence is that he uses a different process, viz. the Collodion process.
The reply is that the Collodion process borrows from the Calotype process the essential part of the latter, viz. the development of a latent image by gallic acid. What we wished you if possible to testify was that (in your opinion) such development of a latent image
But since you feel scrupuloux [sic] about making these assertions we will endeavour to dispense with the necessity of troubling you and I will not apply again unless my solicitor assures me that he feels himself in need of support from high scientific authority. We have Sir D. Brewsters affidavit to the above effect, though in other words. 
Letter No. 6, Herschel to Talbot, Draft dated 21 May 1854.
May 21 / 54.
My dear Sir,
It is only as respects theCollodion process that I demurred and really if your defendant sets up a plea that he does not employ your process but another [
A. makes photographs for sale
Letter No. 7, Talbot to Herschel, dated 23 May 1854.
[To] Sir J. Herschel.
Athm. Club. Tuesday
The principal affidavit is by Mr. Robert Hunt, and as you will see, he introduces your name. I have therefore thought it right to send you a copy of it, and at the same time to ask you for a short affidavit in reply to that part only of Mr. Hs affidavit which names yourself (not noticing any other part of it). I have followed partly the wording of the note I received from you this morning - the rest I have drawn up in words that I thought you would be likely to adopt, but if not, pray alter them to others. I find that I need not trouble you to call at Lincolns Inn, for as soon as the words of the affidavit are settled, and you appoint a time, I can call on you with a solicitor either in Harley St of an evening, or at the Mint, at an earlier period of the day.
I have just now taken down the Transns of the Royal Society for 1840, and carefully reperused your paper and can find no other mention of Gallic acid than that at page 8, which therefore I conclude to be the passage referred to by Mr. Hunt. I think the Vice Chancellor will hear the cause on Friday, therefore tomorrow or Thursday are the days on which I could call on you with a solicitor empowered to take an affidavit. (This is a new arrangement, very convenient for persons engaged in legal proceedings)
Yours very truly,
No. 7a, Copy of Chancery Affidavit sworn by Robert Hunt and Charles Heisch; sworn 22 May 1854 in the cause Talbot v. Henderson.
We, Robert Hunt and Charles Heisch say ...
Item 4. ... the mode of taking Portraits contemplated by the said Plaintiff [Talbot] as described in his [Calotype] specification is limited to the use of sensitive calotype paper for obtaining a negative image, and to the use of gallo-nitrate of silver for obtaining there from a positive image upon ordinary photographic paper.
Item 5. Gallic acid and infusion and tincture of galls had been used for the purpose mentioned in the Plaintiffs specification long before the date of his Patent both by Sir John Herschel and the Reverend J. B. Reade. the first public use of the infusion of nut galls, which is an essential element in the Plaintiffs patented process is due, as we are informed and believe, to the said J. B. Reade, who communicated the fact of his having used such infusion as an accelerator to Mr. Edward W. Brayley, Junior, by letter on or about the 9th March 1839, and the said Edward W. Brayley, as we are further informed and believe, published the information so received by him from the Rev. J. B. Reade at a Lecture delivered by him at the London Institution in or about the same year and exhibited at such lecture specimens of photographs obtained by J. B. Reade by that process. Sir John Herschel also published the fact of his having used gallic acid in a paper communicated by him to the Royal Society on 20th February 1840, and which paper is printed and published in the Philosophical Transactions.
Item 6. The Collodion process was invented subsequently to the date of the Plaintiffs Patent. The invention was not patented.
Item 7. Although the result obtained by the use of Collodion is finally in a measure the same as that yielded by Calotype paper, in as much as both processes eventually produce a picture, yet the collodion process is essentially different from that described in the Plaintiffs specification.
Item 10. That the images produced on Collodion are different, and the final results therefrom are better, have a greater sharpness of outline, vigour of tone, and delicacy of tints and half tints, than can possibly be obtained by Calotype, and the first of these processes is much more rapid in its action than the second.
Item 11. the collodion process differs as much from the Calotype as the latter differs from the daguerreotype process.
Item 12. That gallic acid and gallo-nitrate of silver are not employed in the Collodion process.
Item 13. That the Collodion image is developed by the use of either the proto sulphate of iron for which the Plaintiff himself has acknowledged in a communication made by him to the Athenaeum on 6th December 1851  that Science is indebted to Mr Robert Hunt, or by pyrogallic acid... .
Item 14. Dormant images obtained by light were developed long previously to the date of the Plaintiffs Patent by M. Niepce in 1827 and M. Daguerre in 1839.
Herschels reply to Talbots last letter, with its enclosures, is not now available. He did, however, swear an affidavit before a Commissioner of Oaths (and presumably Talbot also visited him?) at his town house at 32 Harley Street, on the Thursday, 25 May. The hearing did take place, as Talbot thought, on Friday 26 May 1854.
No. 8, Copy of Chancery Affidavit sworn by Sir John F. W. Herschel; sworn 25 May 1864 in the cause Talbot v. Henderson, 
Item 1. I have read a copy of an Affidavit sworn in this cause by Robert Hunt and Charles Heisch... in which my name is mentioned in the following terms, viz., Sir John Herschel also published the fact of his having used Gallic Acid in a paper communicated by him to the Royal Society on February 20th 1840 and… published in the Philosophical Transactions.
Item 2. I say that the inference attempted to be drawn to the prejudice of the Plaintiff from my Memoir... is erroneous in as much as in the experiments there referred to I did not use Gallic Acid for the purpose of developing a dormant picture,  not being then aware that any such dormant picture then existed, but only with a view to increase the sensitiveness of the paper.
Item 3. I say that my memoir above referred to extended to nearly Sixty pages, and that Gallic Acid is only once named in it, to the best of my recollection, videlicet, at page eight, in the following words. My first attention was directed to the discovery of a liquid, or emulsion, which by a single application, whether by dipping or brushing over, should communicate the desired quality. The presence of Organic matter having been considered by some late Chemists an essential condition for the blackening of the Nitrate of Silver, I was induced to try in the first instance a variety of mixtures of such organic soluble compounds as would not precipitate that Salt. Failing of any marked success in this line (with the somewhat problematic exception of the Gallic Acid and its compounds) the next idea which occurred was ....
Item 4. I say that in writing the passage of my memoir above quoted, I did not contemplate the Photographic process since called the Calotype process, nor was I then acquainted with that process.
The day after Herschel signed the affidavit it was presented, in support of Talbots case, before the Vice Chancellor. Immediately afterwards, Talbots solicitor, J. H. Bolton, sent Herschel his copy of the affidavit, and also briefly reported the result of the hearing. Talbot wrote the same day to tell him more of what happened:
Letter No. 8a, Mr. Bolton to Sir John Herschel, dated 26 May 1854.
Mr. Bolton presents his complements to Sir John Herschel & begs to enclose copy of his affidavit as desired. Mr. B. begs to acquaint Sir John, that the Motion for an Injunction was heard today by V. C. Wood and an order for such Injunction was made as prayed .
[To] Sir John Herschel Bart.
Letter No. 9, Talbot to Herschel, dated 26 May 1854.
[To] Sir J. Herschel.
I remain, Dr Sir,
On the same day Talbot also wrote (in his diary? ):
Court of Chancery. We are completely successful against a defendant of the name of Henderson who has been infringing my patent by taking portraits in Regent Street. The case was argued for three hours before Vice Chancellor Wood. The affidavits of Brewster and Herschel demolished the defendants case.
But in spite of Talbots glowing report of the Vice Chancellors hearing this is not borne out by the report of the case in The Times . The Vice Chancellor had, in fact, some doubts about granting the injunction: he said, it was quite clear that there was a serious point to be tried at law between the parties. The Times reported him as saying that He should grant the injunction - but he felt some doubt as to that part of the order which asked to restrain the defendant from imitating and resembling the plaintiffs invention, or any part thereof. Talbots counsel pointed out, however, that those words had been copied from the order made by the previous Vice Chancellor in an earlier similar case. Vice-Chancellor Wood therefore thought that, because of this earlier ruling, the Order must stand: but a question had been raised... as to whether the Collodion process was an infringement of the patent... There was sufficient before the Court, to show that an action must be tried. The counsels were directed to undertake this action immediately.
The two other affidavits that had been presented at the hearing in support of Talbot, by Nicolas Henneman, and by Sir David Brewster,,  made statements about the Collodion process; but, as we have seen, Herschel studiously refrained from giving any opinion about this.
The case was not pursued forthwith, as directed; for it was decided to hold it over until after the result of Talbots more urgent action against Martin Laroche was known. In that action the jury did find that Laroches use of the Collodion process could not be deemed an infringement of the Calotype process. It seems that later in the year Talbot inquired if Sir David Brewster would also be prepared to give evidence at the Laroche hearing; Brewster replied that he could not go to London unless his evidence was essential, and, as Talbot did not think this was so, he took no part in that trial.
Obviously Herschels attitude regarding the Collodion process made it unlikely that he would be an effective witness at the Laroche hearing. Before that action was heard in December 1854, Talbot wrote to W. T. Brande to ask if he would consent to give evidence, and mentioned that Herschel has an objection to appearing in court and therefore it is not our intention to ask him. It is even more unlikely that Herschel would have appeared at the Laroche trial, when we remember that his health was very poor in the latter part of 1854.
This correspondence of Talbot and Herschel during 1854 is of some interest because of the fresh glimpse that we are able to get of their personal relationship. With this in mind, it is worth looking back fifteen years, to the time (1839) when they were writing often to each other about the then new art of photography. It is a common experience for the reader of this earlier correspondence to be struck by the difference between these two men. 1839 was a tense time for Talbot. He had been giving some attention to photographic experiments since 1834, and the announcement of Daguerres invention obviously shattered his own hopes of astounding the world; one can certainly feel some sympathy for him in this. But his Photogenic Drawing technique was not, in fact, such a startling achievement, although Talbot was obviously anxious that it should be so acknowledged. Indeed biographers of Talbot have sometimes expressed surprise that he did not receive greater recognition in 1839; the answer is that his contempories were, quite simply, more able to estimate the true extent of his achievement at that time. However, we should not perhaps forget the genuine regard that Herschel had for Talbots Photogenic Drawing sensitization. It must have been disappointing for Talbot to observe the ease with which Herschel tackled the problems involved in the first steps in photography during the first few weeks of 1839. Herschel communicated information about his early experiments with a frankness that is noticeably lacking on Talbots side;  Herschels letters are characterized by an easy openness, while Talbots sometimes possess an undercurrent of agitation and anxiety. It is interesting to note that the 1854 correspondence also shows, to some extent, the same features.
Talbots comment, in his letter of the 20 May 1854 about Herschels discovery of hypo, lacks a little tact; one wonders if he would ever have considered, that the remark could, in some circumstances, have been misunderstood? It is illustrative of an interesting facet of his nature, that he was able to offer a compliment in such a guileless manner.
Certainly this new correspondence enables the affidavits of Brewster and Herschel to be seen in a fresh light; for the statements that they contain resulted from the considerable prompting of Talbot.
Herschels attitude in 1854 towards his early use of gallic acid was most reasonable. There is no reason to suppose that he, any more than J. B. Reade, had any concept of latent image development before Talbot published this. Herschels work in general during 1839 and 1840 was of influence on Talbot. Leaving aside speculation regarding any influence that Herschel might have upon Talbots realization of development, we can certainly ask a more limited question: did Herschels use of gallic acid in 1839 prompt Talbot to experiment with that chemical? Consideration of this question must wait until a later paper.
Finally, we must not forget that there was another man involved in the events of 1854:
In 1848 Henderson started to practise as a Daguerreotypist in Fleet Street, London, moving in 1851 to 184 Strand. Around 1852 he had thought that the public demand for the Daguerreotype had dropped, and he therefore took lessons in the wet-collodion technique. Stimulated by the falling-in of his house in the Strand in September 1853, he decided to move to 204 Regent Street and to include portraits on paper as part of his trade. He paid out £120 for a years lease at Regent Street, fitted out the studio for £100, and spent about another £100 on advertising: but, he said, had not held myself out as a taker of Photographic Portraits on paper for more than three weeks before I received the Notice of Motion for an Injunction,
and the whole sum I have received for them has not exceeded the sum of £14 ,  Talbots solicitors took the first steps in the action within two weeks of the granting of the injunction, and for several weeks pressed Henderson to prepare his defence speedily. At this time a proposal was made to set up a Defence Fund for him. However, as Talbots proceedings against Laroche were certain to be heard first, the solicitors finally agreed, at the beginning of November 1854, to let all proceedings regarding Henderson stand over until after the action against Laroche had been tried. When Martin Laroche won his case in December 1854 the solicitors of Talbot and of Henderson agreed that the litigation should not be pursued. But Hendersons solicitor pressed for compensation for his client, and did not agree with Talbots representatives that Henderson should bear any of the legal costs (about £150) that he had so far incurred. Luckily, at the time when the injunction was granted the Vice Chancellor had agreed to the suggestion of Hendersons counsel that a condition might be imposed upon the plaintiff of making compensation to the defendant, if he [Talbot] failed in the action. Accordingly, on 6 June 1855, a Motion was filed in Chancery after a hearing before the Vice Chancellor to enable Henderson to be awarded damages and compensation. A second stage of the case Talbot v. Henderson thus began.
At this time, Henderson was no longer living in London. A few months after the granting of the injunction in 1854 he began to feel the strain of his situation: he did not renew the lease of his Regent Street studio when it was due in October 1854, and, on the advice of his doctor, removed to Hampstead for change of air. During the summer of the following year he went to live at Brighton, and later may have moved to Launceston, Cornwall.
Both sides prepared their case during the summer of 1855; facts and opinions were gathered about the extent of damage, if any, which had been caused to Hendersons business by the granting of the injunction. Talbots side asked to examine his business receipts. Many accounts were not still available, but it was shown that his gross receipts for the taking of portraits averaged £31 per month; this was both for the 10 months before the granting of the injunction, and for the remaining five months at Regent Street after that time. It was also necessary to estimate what damage to his business there would have been in 1855; although anyone else could use the collodion technique after the Laroche verdict in December 1854, Henderson could not legally do so, for the injunction against him was still in force.
In November 1855, both contestants again arranged for affidavits to be sworn for them by their supporters, and in February 1856 those witnesses were cross examined about their opinions. On Talbots side, Antoine Claudet  and Nicolas Henneman alleged that Henderson would not have received any increase of income by selling paper portraits rather than Daguerreotypes. Furthermore, they insisted that his income in 1855 would have been very drastically reduced because of the large number of photographers who were using the Collodion process since the Laroche verdict. Henneman gave a very gloomy picture of his own business to support this argument. There were, he complained, about twenty photographers then practising the Collodion process in Regent Street. Before December 1854 he would not have liked to have sold his business in Regent Street for under £4,000 or £5,000; but the great increase in competitors using the Collodion technique, due to Laroche winning his case against Talbot in that month, meant that the value of his business had been greatly reduced. He said, I would not like to sell up under £2,000 or £3,000 now. This was six months after Talbot v. Laroche. No doubt this argument was considered a useful one to put forward; but it is ironic that the facts consequent upon Talbot losing his case against Martin Laroche should be used as a weapon against Henderson.
On the other hand, Henderson claimed that he was stopped by the injunction in 1854 from establishing a good and lucrative business in taking portraits by the collodion technique. He said: If the damage I have sustained by the consequences of the Injunction... is to be estimated in money, I consider that the plaintiff ought to pay me at least £500. His supporters variously suggested that he should be entitled to £300 or £400 for loss of profits.
On 18 March 1856 a decision on the case was reached by Vice Chancellor Wood:
It is Ordered  that the Plaintiff, William Henry Fox Talbot, do... pay the Defendant the sum of £150, being the amount of damage... And it is Ordered that the Plaintiffs Bill do stand dismissed out of the court with costs to be taxed... ; the costs of all the defendants Witnesses are to be taxed and allowed as ordinary witnesses and not as Scientific Witnesses. And it is Ordered that the Plaintiff William Henry Fox Talbot do pay to the said James Henderson the Costs when taxed.
Hendersons legal costs were later found to be £180. 16s. 4d.  Talbot was to pay this as well as his own expenses.
So, almost two years after the granting of the injunction to stop Henderson from using the Collodion process for taking portraits for sale, and with Henderson to receive £150 damages, the case of Talbot v. Henderson came to a close.
[ A letter written on 5 April 1856  by Henderson to Talbot provides a brief glimpse of the consequences of the case for Henderson. ]
 Notes and Queries, July 8th 1854, 10, 35-6. (A short extract of this was made in Liverpool Phot. J., August 12th 1854, 1, 110.)
Art J., June 1852, p. 193; August 1854, pp. 236-8. A large part of the 1852 Art Journal article is found in exactly the same words in the preface of A Practical Manual of Photography, by Jabez Hogg, 4th edn., 1853; this suggests, of course, that Hogg was the author of the Art Journal article (although no other evidence has been found for Hoggs connection with that journal).
Jabez Hogg (1817-1899) (D.N.B., 1901, 1st Suppl., vol. ii, p. 432), was an ophthalmologist and microscopist who was also on the staff of the Illustrated London News, and other of Ingrams illustrated magazines. He certainly held strong views against photographic patents. The earlier edition (the 2nd, 1845) of his photographic manual differs from the 1853 one, both in having a slightly different title, Photography made easy: A Practical Manual of Photography ... by a Practical Chemist and Photographist, and a different preface; this preface of 1845 calledThe Injustice and Validity of the Patent Considered, With suggestions for rendering such a patent a virtual Dead letter, specially concerns the Beard v. Egerton case and the Daguerreotype patent. Unfortunately, I have been unable to trace any copy of the 3rd edition; this presumably was published before the 1852 Art Journal article.
Robert Hunt had been a fairly regular contributor to the Art Journal since 1848. He, of all the persons associated with the journal, must certainly have been the most knowledgable about photographic history and techniques; it would be rather surprising if he was not associated in some way with the Art Journal editorial articles on the photographic patents; but, in fact, there is no evidence for this. He did, very briefly, mention Herschel and gallic acid in the 1854 (2nd edition) of his Researches on Light, p. 84: The discovery of the extraordinary property of the gallic acid, in increasing the sensibility of the iodide of silver, is amongst the numerous claims which Mr. Talbot has made to dis. coveries in the photographic art. It must however be remembered that Sir J. Herschel used gallic acid, but not successfully, and that previously the infusion of galls had been employed by the Rev. Mr. Read [sic] with success. A very brief comment about this subject and Herschel was made also by Hunt in the Art J., February 1856, pp. 49-50.
 Letter reproduced in facsimile inThe origin of the word “Photography”: An Historical Letter, I. M. and A. Barclay, Phot. J., September 1937, 77, 528-531.
 Herschel had given Talbot considerable details of his experiments during the previous four weeks, and Talbot did respond (one might think a little belatedly), on the 19 February 1839 (letter HS 17.284, Herschel papers, Royal Society), by telling Herschel about his method offixing with common salt or potassium iodide. Talbots second paper on Photogenic Drawing, in which he gave information on the chemicals used, had also been read to the Royal Society on 21 February, and published in the Literary Gazette and the Athenaeum on 23 February.
Herschel does not, in fact, seem to have done any experiments for a month, at this time; his Chemical Notebook (in Photographic Collection, Chemistry Dept., Science Museum, London, and Microfilm B13 Science Museum Library) records on 20 February 1839,Got Fox Talbots letter of Feb 19 and tried his processes by Hydriod Potash and Common Salt...; then no further experiments are recorded until 24 March 1839.
 Phil. Trans., 1840, 130 (part 1), 1-59 (the quotation is from Item 27). Abstracts of this paper were also published in Phil. Mag., March 1840, 16, 239 and April 1840, 16, 331, and in the Athenaeum, 28 March 1840, pp. 254-5; but the remarks about gallic acid are not mentioned therein. The paper was read over three meetings of the Society. The MS of the paper (Royal Society PT 23.1) is marked as having been read up to item 19 on 20 February; item 27 was therefore read on 27 February 1840.
 A published report of the hearing of this case on 26 May 1854 is found in The Times, May 27th 1854, p. 11, and was reprinted in Newtons London J. Arts. Sci., 1854, 44 (conjoined series), 457-460.
The account of Talbot v. Henderson given in this article results from a search of Court of Chancery records at the Public Record Office, London. Four classes of Chancery documents have been found, at the P.R.O., which deal with the first (1854) stage of this case:
(a) Chancery Cause Book C32/329/Cause 1854, T39.
(b) Chancery Decrees and Orders C33/1023 (Motions 829, 907, 1080, 1094), and C33/1024/1167.
(c) Chancery Proceedings, C15/157/Pleading 1854, T39. This important group of Pleading documents contains the 19 page Bill of Complaint, Interrogation of 13 June 1854, and Defendants Answer of 1 August 1854; furthermore there are also filed here several Depositions of Witnesses made during the later stages of the case, in 1855 and 1856.
[(d) Chancery Affidavits — continue over to foot of next page 244]
(d) 16 Chancery Affidavits sworn during 1854, all filed in the two boxes of C31/1048; No. 664 sworn by J. H. Bolton, No. 665 N. Henneman, 666 Talbot, 667 Church, 679 Chapman, 706 Hunt and Heisch, 707 A. Normandy, 708 W. H. Thorn. thwaite, 714 Brewster, 719 Henderson, 722 Talbot, 733 Herschel, 800 Chapman 817 Price, 820 Chapman and Maynard, and No. 1111 sworn by Chapman.
 Uncatalogued letters and papers concerning W. H. F. Talbots photographic patent legal action of 1854, Talbot v. Henderson, between Sir John F. W. Herschel and [W.] H. F. Talbot; Royal Society Archives, London. [Since the publication of this article these letters have been catalogued in Herschel Correspondence, Box 26, letters 48–52]
I am most grateful to the Royal Society for not only allowing me to study the MS. collections in their library, but also for their permission to publish these letters; special thanks are due to L. P. Townsend, the Societys Archivist, for his indispensable help in bringing these papers to light.
The papers consist of 12 items: Letters, Talbot to Herschel dated 13 November 1853, 15 May 1854, 18 May 1854, with separate draft affidavit (by Talbot) entitled Afft. of Sir J. Herschel Bart. ...&c., 20 May 1854, 23 May 1854 with enclosure of Copy of Chancery Affidavit sworn by Robert Hunt and Charles Heisch, and 26 May 1854; Rough drafts of Letters, Herschel to Talbot, dated 19 May 1854, and 21 May 1854; Letter, Mr. Bolton to Herschel, dated 26 May 1854 with enclosure of Copy of Chancery Affidavit sworn by Sir John Herschel. The letters are quoted in full in this article; the Copy Affidavits are, however, edited slightly.
 Letter at Science Museum dated 7 November. [Since the publication of this article in 1971, Herschels letter of 7 Nov 1853 has been transferred to the National Museum of Photography, and the full text has been placed online.] Dr. D. B. Thomas kindly tells me that Herschel asks in the letter if Bowring could publish his portrait that had been taken by an amateur using the collodion technique! Herschel and Talbot corresponded extensively between 1826 and 1844, but, it would seem, comparatively rarely after that time. (There are 70 letters from Talbot to Herschel in the Royal Society Collection up to 1844, but, except for this correspondence concerning the Henderson injunction, only 4 letters after 1844) However, Herschel does seem to have written to Talbot earlier in 1853. For E. Ostroff, in Etching, Engraving and Photography; History of Photomechanical Reproduction, J. Phot. Sci., 1969, 17, 65-80, quotes a letter from Herschel to Talbot dated 14 May 1853. It appears from this letter (stated to be in the Talbot MS. Collection, Lacock Abbey) that Talbot had early in the year sent Herschel some examples of his photomechanical engravings. [The text of that short letter of "14" May 1853 has more recently been placed online by the Talbot Correspondence Project Document No. 06797.]
 Sir John Bowring, LL.D. (1792-1872), D.N.B., 1886, vol. vi, p. 76; Bowring was at this time involved in proposals for decimalisation in England, playing a prominent part in establishing the one-tenth of a pound, the florin, in English currency. The hand engraving of Herschels photograph [reproduced here ] appeared the following year, in Bowrings book The Decimal System in Numbers, Coins and Accounts, London, 1854, plate opposite p. 72.
 Mention of a jury suggests that Talbot was contemplating a Queens Bench action; this, and the date of the letter, indicates that he had the Laroche action in mind.
 J. R. Hind (1823-1895), D.N.B., 1901, 1st Suppl., vol. ii, p. 424; Astronomer, of Bishops Observatory, Regents Park, well known for his Asteroid observations.
 Talbot told Robert Hunt two years before that he had spent £7,000 in his patents, etc., on the art (Letter dated 5 March 1852, Robert Hunt to Peter Fry, published by J. Dudley Johnston in J. Roy. Soc. Arts, 1939, 79, 832-3). Of course the various ways included, after all, several commercial ventures.
 Affidavits were sworn on the opposite side by Robert Hunt; Charles Heisch, lecturer in Chemistry at the Middlesex Hospital, and the editor that year of Willats Photographic Manual, Plain Directions for obtaining Photographic Pictures ... (Manual No. 1, part II), London, 1854; W. H. Thornthwaite, author of A Guide to Photography, and partner of Horne and Thornthwaite, the Opticians, Instrument and Photographic suppliers of Newgate Street, London. His firm had a close association with F. S. Archer in 1851 (see Archers remarks in Notes and Queries, 25 December 1852, 6, 612), and were, at first, the exclusive suppliers of his iodized collodion. The firm became a centre for the introduction of the collodion process, and there can be little doubt that they were also a centre of agitation against Talbots patents. Henderson had applied to them, in or about the year 1852 for instruction in the collodion process, and accordingly Fallen Horne had taught him this. (Chancery Affidavit, sworn by Horne, 26 November 1855, P.R.O., C31/1127/1344); Alphonse Normandy, a consultant Chemist, experienced in patent and legal proceedings (D.N.B., 1895, vol. xli, p. 114); and, of course, James Henderson also filed an Affidavit. For Affidavit references see footnote [5 (d)]
 Charles Wheatstone (he was not yet knighted) became a vice-president of the Royal Photographic Society on its formation in January 1853. He had taken a general interest in the photographic discoveries in the early part of 1839, and he had corresponded with Talbot at that time. No affidavit by him was filed in the case. [A letter from Wheatstone to Talbot dated 22 May 1854 (Lacock Abbey MSS LA 54.25) shows that Wheatstone avoided giving his support]
 Pyrogallic acid was usually used as the developer in the Collodion process, not gallic acid. F. S. Archer introduced the use of pyrogallic acid in 1850 (F. S. Archer, The Chemist, 1850, 1 (n.s.), 360-1 and 450-1); in fact he used it on the albumen on glass technique, before he brought in the Collodion process.
 Talbot must also have sent a draft of a proposed affidavit to Brewster just as he had done to Herschel; in fact the first half of it must have been the same, for six out of the nine items of Brewsters sworn statement are identical with items proposed for Herschel. Items 1, 2, 3, 5 and 6 together, and 7, of Brewsters affidavit are almost identical with items 1, 2, 3, 6, and 7, respectively, of the draft.
 The Bill of Complaint had been served on Henderson on 6 May; as he had not been warned in any way before that, he did not have very much time to prepare any defence.
 Probably no one was more familiar with Herschels photographic work than was Hunt. He had written to Herschel in December 1839 to tell him about his own photographic experiments; after this first approach by Hunt, they had corresponded extensively during the following decade, and also Herschel had been able to give Hunt a little help in personal matters during that period. They seem, however, to have had little contact in the early 1850s; indeed it is surprising to note that when Hunt sought election to the Royal Society in 1852 his certificate of nomination did not contain Herschels signature (although he did receive support from Talbot!). For the relationship between Herschel and Hunt see their letters preserved in the Royal Society collection of Herschel papers, letters HS 10.80 to 10.136.
 Although the copy of Hunts affidavit was found in the bundle of this correspondence, a second draft affidavit as proposed for Herschel does not still exist. This is especially unfortunate as Herschels reply to this letter is also lacking. Talbots remark about havingfollowed partly the wording of the note I received from you… is a little amusing, for those words were, of course, quoted from his own letter of the 20 May; the three points mentioned are to be found in item 5 of the affidavit that Herschel finally swore on 25 May 1854.
 The copy sent to Herschel which is in the bundle of correspondence at the Royal Society was made by Talbots solicitor; the original affidavit is, in fact, filed at the Public Records Office, Chancery affidavit C31/1048/706. It is not necessary to quote it in its entirety; the Title, the Jurat, and the legalistic and generalized parts of the Statement are omitted. As the affidavit lacks punctuation this has been added, and all the dates are given as figures.
 This, in the Athenaeum, 6 December 1851, pp. 1286-7, was a report by Talbot of the method which he called the Amphitype. It was the subject of his fourth photographic patent (No. 13,664), which was enrolled on 12 December 1851. This patent incorporated the use of albumen on glass (which had first been put by Talbot into his 1849 patent (No. 12,906) even though the Albumen technique had been described by Niepce de Saint Victor in Comptes Rendus Acad. Sci. Paris, in 1848) with development with sulphate of iron. Hunt had used ferrous sulphate as a developer in his Energiatype (or Ferrotype) process in 1844. (Published in the Athenaeum, June 1844, pp. 500-1, and Adv. Sci. Brit. Assoc. Report for 1844, part II, p. 36, and comments by Talbot, p. 105.) The incorporation of the use of ferrous sulphate in Talbots patent resulted in a little controversy in the Athenaeum (3 January 1852, pp. 22-3, and 10 January, pp. 55-6). Talbots patenting activities must have been a source of irritation to Hunt, although from the evidence. available (see for example his letter to Peter Fry about Talbot in 1852, which has been quoted on p. 53 of J. B. Reade and the Early History of Photography, Part II) he seems to have been friendly in his attitude to Talbot. Hunt, in contrast to Talbot, always freely published his photographic work; he might also have claimed that the patenting by Talbot of iodised paper could easily have owed its origin to his own published work (Phil Trans., 1840, 130, 325-34); and he could easily have pointed out that he had spoken in 1840 of the chemical disengagement of the light-created picture - the invisible photographic image, but he was obviously ready to acknowledge that his ideas about this would have been derived from the work of others (see mention of Niepce and Daguerre in Item 14).
 It is difficult to accept that Niepce and Daguerre discovered the idea of the latent image and its development. The empirical use of mercury-forming an amalgam with the silver - in the Daguerreotype process cannot, without ambiguity, be called development; but it would surely have had some significance in preparing the way for such a breakthrough in ideas.
 This copy of Herschels affidavit was made by Talbots solicitor. The original affidavit is filed at the Public Record Office, Chancery Affidavit C31/1048/733. As with Hunts affidavit, the Title and Jurat of the affidavit have been omitted. It was also published six weeks later in Notes and Queries, 8 July 1854, 10, 35-6.
 This use of the words dormant picture rather than latent image, is interesting; for Herschel did speak in his 1840 memoir of the picture, though invisible, is only dormant. However, he was not speaking of the latent image and development, but of the picture that had been made invisible, and dormant, by having been treated with corrosive sublimate (mercuric chloride); this could be instantly revived in all its force by merely brushing it over with a solution of a neutral hyposulphite (Phil. Trans., 1840, 130, p.6 (item 19.).
 William Henry Fox Talbot, F.R.S.: Material towards a Biography, collected by J. Dudley Johnston, edited by R. C. Smith, Phot. J., December 1968, 108, 361-371. The passage quoted is stated to have been written on 26 May, although there is some confusion in the article about the year in which it was written; it was obviously not written in 1851 as stated, but in 1854.
 He was, in fact, referring to Talbot v. Colls, 22 January 1852: see J. B. Reade and The Early History of Photography: part II, pp. 52-53.
 Chancery Affidavit sworn 6 May 1854, P.R.O., C31/1048/665.
 Chancery Affidavit sworn 24 May 1854, P.R.O., C31/1048/714. Brewsters affidavit was also published (with Herschels) in Notes and Queries, 8 July 1854, 10, 34-5. He was staying in London at the time, and swore the affidavit in the chambers of Talbots solicitor. Item 8 (I consider the said collodion process to be only a variation or modification of the plaintiffs said invention, called by him the Calotype, for [four following reasons]...) is the most important part of his statement concerning the Collodion process.
 Talbots evidence at Talbot v. Laroche, Phot. J., 21 December 1854, 2, 88.
 MS letter in George Eastman House Collection, quoted by Beaumont Newhall, Latent Image, New York, 1967, pp. 129-130.
 See his diary for that period (MS. Copy of Herschels Diary, 1848-1860, MS. 585, Royal Society, London), and Literary Gazette, 5 May 1855, p. 284.
 Some attention has been drawn to the relationship between Talbot and Herschel during 1839 in H. Gernsheims Talbots and Herschels Photographic Experiments in 1839, Image [GEH], September 1959, pp. 133-37, and in R. S. SchultzesRediscovery and Description of Original Material on the Photographic Researches of Sir John F. W. Herschel, 1839-1844, J. Phot. Sci., 1965, 13, 57-68 (pp. 62-4 relevant). Both of these articles had restricted terms of reference; and as the writers had incomplete access to other Herschel/ Talbot correspondence further scrutiny of the subject is required. Attention will be given to this in a later paper.
 Chancery Affidavit, sworn 4 June 1855, P.R.O., C31/1126/749.
 Chancery Affidavit, sworn 25 May 1854, P.R.O., C31/1048/719.
 Notes and Queries, 24 June 1854, 9, 598-9. In fact a Fund was set up for Martin Laroche. Donations to the Fund, organised by W. H. Thornthwaite, had, by April 1855, reached only £105, although Laroches legal expenses were between £400 and £500 (Art. J., April 1855, p. 127).
 Court of Chancery documents at the Public Record Office, London, which deal with the second (1855-1856) stage of Talbot v. Henderson are:
(a) Chancery Decrees and Orders, C33/1031/Motion 943, C33/1031/Order 1154, C33/1038/840.
(b) Two Chancery Affidavits sworn on 4 June 1855 by James Henderson and his lawyer, John Mead, filed in box C31/1126; affidavits No. 749 Henderson, 752 Mead.
(c) Nine Chancery Affidavits, sworn during November 1855, all filed in box C31/1127; consists of five affidavits on Hendersons side, No. 1236 Henderson, 1344 F. Horne, 1345 A. Normandy, 1346 J. P. Bourquin, 1347 T. Mackern; and four affidavits on Talbots side, 1348-9 T. Donnithorpe (solicitors clerk), 1350 A. Claudet, 1351 N. Henneman.
(d) Two Affidavits sworn on 6 and 10 December 1855 by James Henderson, C31/1215/294 and 295.
(e) Chancery Proceedings, C15/157/Pleading 1854, T39. As well as containing items concerning the 1854 stage of the case, this Pleadings group of documents includes Depositions of Witnesses made during 1855 and 1856:
Deposition filed 6 July 1855, sworn on 30 June 1855 by J. H. Bolton; Deposition filed on 4 August 1855, sworn on 30 July 1855 by James Henderson; Deposition of N. Henneman sworn 30 June 1855; five Depositions filed 7 February 1856, which were sworn on 5 February 1856 by A. Normandy, F. Horne, J. P. Bourquin, A. Claudet, and J. Henderson.
It is hoped that it will prove possible in the future to publish transcripts of many of these Talbot v. Henderson Documents; they are a source of most interesting information about the Calotype patent and professional portraiture in London during the early 1850s.
 Claudets studio was also in Regent Street, at No. 107, on the opposite side to Henneman and Henderson. For biographies of Claudet (1797-1867) see D.N.B., 1887, vol. xi, p. 2; Claudet a Memoir by Joseph Ellis; Phot. J., August 1868, 13, 101-8; A. T. Gill, Phot. J., December 1967, 107, 405-9.
 Chancery Decrees and Orders, P.R.O., C33/1038/840. This, and other extracts in this article quoted from Crown copyright records of the Court of Chancery in the Public Record Office, appears by permission of the Controller of H. M. Stationary Office.
 Expenses paid to Scientific Witnesses were not normally allowed as legal costs. In the 1854 stage of the case Henderson had incurred expenses of about £30 for Scientific Witnesses: A. Normandy (see footnote 12) fits this description.
 See page 244. Mr. Church was, in fact, the nineteen-year old student and assistant who became Professor of Chemistry at the Royal Agricultural College and later at the Royal Academy: Sir Arthur Herbert Church, F.R.S. (1834-1915), obituary in J. Chem. Soc., 1916, 109, part 1, 374. (I am indebted to J. Bentley, who has recently published a study of the Royal College of Chemistry in Ambix, 1970, 17, 153, for his help in identifying Church). Church was at the Royal College of Chemistry in Oxford Street from 1851 to June 1855. The affidavit regarding his visits to Hendersons studio was sworn before John Thomas Church who was, of course, formally described as a London Commissioner to administer Oaths in Chancery, but who was, in fact, his own father, a solicitor of Bedford Row.
With Church in the College laboratory was another famous pupil and assistant of Professor Hofmann, Sir W. H. Perkin, with whom Church published work two years later. But of particular interest are two other assistants or demonstrators John Spiller and Sir William Crookes who were at the College at this period. Spiller and Crookes published their papers concerning a Method for preserving the Sensitiveness of Collodion Plates etc., at the time of Talbot v. Henderson, in May and July 1854 (Phil. Mag., 1854, 7, 349; Phot. J., 1854, 1, 205, and 2, 6). Both Crookes and Spiller became editors of photographic journals. Crookes was assistant at the College from 1850 to 1854, and also collaborated later with Church. He could easily have been well aware of the events concerning the Calotype patent, for he was associated with Charles Wheatstone and his family home and business was at 143 Regent Street. The Life of Sir William Crookes, by E. E. F. DAlbe (London, 1923) contains a letter of 1858 from Talbot to Crookes regarding patents.
 Chancery Certificate of Costs dated 27 June 1856, P.R.O., C38/2345/Trinity 1856, Talbot v. Henderson, filed 1 July 1856.
 [Item added to online version at www.midley.co.uk, not in original article in Annals of Science 1971 Letter (Lacock Abbey Collection: LA56.018) from Henderson to Talbot dated 5 April 1856 ]
© Copyright 1971: R. D. Wood and publishers Taylor & Francis Group