"The three known papers were those impregnated with the nitrate, chloride, and the iodide of silver-the two former used by Wedgwood and Young, and the latter by Davy. It is true that Talbot says of the iodide of silver that it is quite insensitive to light, and so it is as he makes it; but when he reduces it to the condition described by Davy-viz., affected by the presence of a little free nitrate of silver-then he must acknowledge, with Davy, that 'it is far more sensitive to the action of light than either the nitrate or the muriate, and is evidently a distinct compound.' In this state, also, the infusion of galls or gallic acid is, as we all know, most decided and instantaneous, and so I found it to be in my early experiments. Of course I tried the effects of my accelerator on many salts of silver, but especially upon the iodide, in consequence of my knowledge of Davy's papers on iodine in the 'Philosophical Transactions.' These I had previously studied, in conjunction with my chemical friend, Mr. Hodgson, then of Apothecaries' Hall. I did not, however, use iodised paper, which is well described by Talbot in the Philosophical Magazine for March, 1838, as a substitute for other sensitive papers, but only as one among many experiments alluded to in my letter to Mr. Brayley.
"My pictures were exhibited at the Royal Society, and also at Lord Northampton's, at his lordship's request, in April, 1839, when Mr. Talbot also exhibited his. In my letter to Mr. Brayley, I did not describe iodised pictures, and, therefore, it was held that exhibition in the absence of description left the process legally unknown. Mr. Talbot consequently felt justified in taking out a patent for uniting my known accelerator with Davy's known sensitive silver compound, adopting my method (already communicated to him) with reference to Wedgwood's papers, and adding specific improvements in manipulation. Whatever varied opinion may consequently be formed as to the defence of the patent in court, there can be but one as to the skill of the patentee.
"It is obvious that, in the process so conducted by me with the solar microscope, I was virtually within my camera, standing between the object and the prepared paper. Hence the exciting and developing processes were conducted under one operation (subsequently patented by Talbot), and the fact of a latent image being brought out was not forced upon my attention. I did, however, perceive this phenomenon upon one occasion, after I had been suddenly called away, when taking an impression of the Trientalis Europæa-and surprised enough I was, and stood in astonishment to look at it. But with all this, I was only, as the judge said, "very hot." I did not realize the master fact that the latent image which had been developed was the basis of photographic manipulation. The merit of this discovery is Talbot's, and his only, and I honour him greatly for his skill and earlier discernment. I was, indeed, myself fully aware that the image darkened under the influence of my sensitiser, while I placed my hand before the lens of the instrument to stop out the light; and my solar mezzotint, as I then termed it, was, in fact, brought out and perfected under my own eye by the agency of gallic acid in the infusion, rather than by the influence of direct solar action. But the notion of developing a latent image in these microscopic photographs never crossed my mind, even after I had witnessed such development in the Trientalis Europæa. My original notion was that the infusion of galls, added to the wet chloride or nitrate paper while the picture was thrown upon it, produced only a new and highly sensitive compound; whereas, by its peculiar and continuous action after the first impact of light on the now sensitive paper, I was also, as Talbot has shown, employing its property of development as well as excitement. My ignorance of its properties was no bar to its action. However, I threw the ball, and Talbot caught it, and no man can be more willing than myself to acknowledge our obligations to this distinguished photographer. He compelled the world to listen to him, and he had something worth hearing to communicate; and it is a sufficient return to me that he publicly acknowledged his obligation to me, with reference to what Sir David Brewster calls 'an essential part of his patent' (vide North British Review, No. 14 article-'Photography').
"Talbot did not patent my valuable fixer. Here I had the advantage of having published my use of hyposulphite of soda, which Mr. Hodgson made for me in 1837, when London did not contain an ounce of it for sale. The early operators had no fixer; that was their fix; and, so far as any record exists, they got no further in this direction than 'imagining some experiments on the subject!' I tried ammonia, but it acted too energetically on the picture itself to be available for the purpose. It led me, however, to the ammonia nitrate process of printing positives, a description of which process (though patented by Talbot in 1843) I sent to a photographic brother in 1839, and a quotation from my letter of that date has already appeared in one of my communications to Notes and Queries. On examining Brande's Chemistry, under the hope of still finding the desired solvent which should have a greater affinity for the simple silver compound on the uncoloured part of the picture than for the portion blackened by light, I happened to see it stated, on Sir John Herschel's authority, that hyposulphite of soda dissolves chloride of silver. I need not now say that I used this fixer with success. The world, however, would not have been long without it, for, when Sir John himself became a photographer in the following year, he first of all used hyposulphite of ammonia, and then permanently fell back upon the properties of his other compound. Two of my solar microscope negatives, taken in 1837, and exhibited with several others by Mr. Brayley in 1839 as illustrations of my letter and of his lecture at the London Institution, are now in the possession of the London Photographic Society. They are, no doubt, the earliest examples of the agency of two chemical compounds which will be co-existent with photography itself, viz., gallate of silver and hyposulphite of soda, and my use of them, as above described, will sanction my claim to be the first to take paper pictures rapidly, and to fix them permanently.
"Such is a short account of my contribution to this interesting branch of science, and, in the pleasure of the discovery, I have a sufficient reward."
These lengthy extracts from the Rev. Mr. Reade's published letter render further comment all but superfluous, but I cannot resist taking advantage of the opportunity here afforded of pointing out to all lovers of photography and natural justice that the progress of the discovery has advanced to a far greater extent by Mr. Reade's reasoning and experiments than it was by Mr. Talbot's ingenuity. The latter, as Mr. Reade observes, only "caught the ball" and threw it into the Patent Office, with some improvements in the manipulations. Mr. Reade generously ascribes all honour and glory to Mr. Talbot for his shrewdness in seizing what he had overlooked, viz., the development of the latent image; but there is a quiet current of rebuke running all through Mr. Reade's letter about the justice of patenting a known sensitiser and a known accelerator, which he alone had combined and applied to the successful production of a negative on paper. Mr. Talbot's patent process was nothing more, yet he endeavoured to secure a monopoly of what was in substance the discovery and invention of another. Mr. Talbot was either very precipitate, or ill-advised, to rush to the Patent Office with his modification, and even at this distant date it is much to be regretted that he did so, for his rash act has, unhappily for photography, proved a pernicious precedent. Mr. Reade gave his discoveries to the world freely, and the "pleasure of the discovery" was "a sufficient reward." All honour to such discoverers. They, and they only, are the true lovers of science and art, who take up the torch where another laid it down, or lost it, and carry it forward another stage towards perfection, without sullying its brightness or dimming the flame with sordid motives.
The Rev. J. B. Reade lived to see the process he discovered and watched over in its embryo state, developed with wondrous rapidity into one of the most extensively applied arts of this marvellous age, and died, regretted and esteemed by all who knew him, December 12th, 1870. Photographers, your occupations are his monument, but let his name be a tablet on your hearts, and his unselfishness your emulation!
The year 1838 gave birth to another photographic discovery, little thought of and of small promise at the time, but out of which have flowed all the various modifications of solar and mechanical carbon printing. This was the discovery of Mr. Mungo Ponton, who first observed and announced the effects of the sun's rays upon bichromate of potash. But that gentleman was unwise in his generation, and did not patent his discovery, so a whole host of patent locusts fell upon the field of research in after years, and quickly seized the manna he had left, to spread on their own bread. Mr. Mungo Ponton spread a solution of bichromate of potash upon paper, submitted it under a suitable object to the sun's rays, and told all the world, without charge, that the light hardened the bichromate to the extent of its action, and that the unacted-upon portions could be dissolved away, leaving the object white upon a yellow or orange ground. Other experimenters played variations...
