PHOTOGRAPHIC CORRESPONDENCE.
History of Photographic Discovery.—Without entirely agreeing with the opinion expressed to us a few days since, by an eminent scholar and most original thinker, that photography was destined to change the face of the whole world; we have little doubt it is destined to produce some striking social effects. Its history is, therefore, an interesting one, and the following extract from a paper "On some early Experiments in Photography, being the substance of a Letter addressed to Robert Hunt, Esq., by the Rev. J. B. Reade, M.A., F.R.S.," from the Philosophical Magazine for May, 1854, seems, in that point of view, so important, that we have transferred it to "N. & Q."
"I may assume that you are already aware, from my letter to Mr. Brayley of March 9, 1839, and published in the British Review for August, 1847, that the principal agents I employed, before Mr. Talbot's processes were known, were infusion of galls as an accelerator, and hyposulphite of soda as a fixer.
"I have no doubt, though I have not a distinct recollection of the fact, that I was led to use the infusion of galls from my knowledge of the early experiments by Wedgwood. I was aware that he found leather more sensitive than paper; and it is highly probable that the tanning process, which might cause the silver
solution to be more readily acted upon when applied to the leather, suggested my application of the tanning solution to paper.
"In your own history of the photographic process," says Mr. Reade, addressing Mr. Hunt, "you say, 'the discovery of the extraordinary property of the gallic acid in increasing the sensibility of the iodide of silver was the most valuable of the numerous contributions which Mr. Talbot has made to the photographic art.' It is nevertheless true, as stated by Sir David Brewster, that 'the first public use of the infusion of nut-galls, which is an essential element in Mr. Talbot's patented process, is due to Mr. Reade;' and in my letter to Mr. Brayley I attribute the sensitiveness of my process to the formation of a gallate or tannate of silver. I need scarcely say, that among various experiments I tried gallic and tannic acid in their pure state, both separately and mixed; but the colour of the pictures thus obtained with the solar microscope was at that time less pleasing to my eye, than the rich warm tone which the same acids produced when in their natural connexion with solutions of vegetable matter in the gall-nut. This organic combination, however, was more effective with the solar microscope than with the camera, though the lenses of my camera were five inches in diameter. It is probable enough that the richer tone was due to the greater energy of direct solar rays. In using the solar microscope, I employed a combination of lenses which produced a convergence of the luminous and photogenic rays, together with a dispersion of the calorific rays, and the consequent absence of all sensible heat enabled me to use Ross's cemented powers, and to make drawings of objects inclosed in Canada balsam, and of living animalcules in single drops of water. The method I employed was communicated to the Royal Society in December, 1836, and a notice of it is contained in the 'Abstracts.'
"You inform me that some persons doubt whether I really obtain gallate of silver when using an infusion of gall-nuts, and that one of Mr. Talbot's friends raises the question. It is sufficient to reply, that though gallic acid is largely formed by a long exposure of an infusion of gall-nuts to the atmosphere, as first proposed by Scheele, yet this acid does exist in the gall-nut in its natural state, and in a sufficient quantity to form gallate of silver as a photogenic agent; for M. Deyeux observes, that 'when heat is very slowly applied to powdered gall-nuts, gallic acid sublimes from them, a part of which, when the process is conducted with great care, appears in the form of small white crystals.' M. Fiedler also obtained gallic acid by mixing together a solution of gall-nuts and pure alumina, which latter combines with the tannin and leaves the gallic acid free in the solution; and this solution is found, on experiment, to produce very admirable pictures. But what is more to the point, Mr. Brayley, in explaining my process in his lectures, showed experimentally how gallate of silver was formed, and confirmed my view of the sensitiveness of the preparation. It is therefore certain that the use of gallate of silver as a photogenic agent had been made public in two lectures by Mr. Brayley at least two years before Mr. Talbot's patent was sealed.
"I employed hyposulphite of soda as a fixer. Mr. Hodgson, an able practical chemist at Apothecaries' Hall, assisted me in the preparation of this salt, which at that time was probably not be found, as an article of sale, in any chemist's shop in London. Sir John Herschel had previously announced the peculiar action of this preparation of soda on salts of silver, but I believe that I was the first to use it in the processes of photography. I also used iodide of potassium, as appears from my letter, as a fixer, and I employed it as well to form iodide of lead on glazed cards as an accelerator. Iodide of lead has of itself, as I form it, considerable photographic properties, and receives very fair impressions of plants, lace, and drawings when placed upon it, but with the addition of nitrate of silver and the infusion of galls the operation is perfect and instantaneous. Pictures thus taken were exhibited at the Royal Society before Mr. Talbot proposed his iodized paper. The microscopic photographs exhibited at Lord Northampton's in 1839 remained in his lordship's possession. I subsequently made drawings of sections of teeth; and one of them, a longitudinal section of a tooth of the Lamna, was copied on zinc by Mr. Lens Aldous for Owen's 'Odontography.' I may say this much as to my own approximation to an art, which has deservedly and by universal consent obtained the name of Talbotype."
Photographic Cautions.—Diffused light being one of the most common causes of photographic failures, I beg to call the attention of your readers to the construction of their cameras. Working with a friend, and taking the same localities, using the same paper and chemicals, his pictures have proved comparative failures, a general browning pervading the whole, evidently the effect of light. Every inspection failed to discover it, until the mode was adopted of putting one of the paper-holders in its position as for taking a picture, then removing the lens, and, with the aid of the focussing-bag, looking through the hole where the lens is applied, when light became visible in many spaces, entirely accounting for these failures. As many such cameras are now becoming made upon the same sliding construction, every one should test his apparatus before he commences, for such a one is entirely useless. Lately also the glass corners for collodion plate-holders in the dark slides, have been by some makers replaced by a sort of silver looking wire, but possessing little of that metal. The most minute portion of the copper in this wire coming in contact with the excited collodion, produces a decomposition sufficient to spoil any picture. These may appear trivial things to "make a note of," but as they have caused much vexation to one who has had some photographic experience, they may still more perplex a novice; and as you have done so much towards making the science plain, I hope you will give them space in your forthcoming Number.
Lux in Camera.
A Query respecting Collodion.—I have been making some collodion by Mr. Tery's process, and have iodized it with a very sensitive medium. The collodion is very clear and properly diluted. The ether I used had a very powerful smell of sulphur, and was likewise very strong and volatile. I diluted it with an equal
volume of alcohol. The ether was then still very strong. The cotton dissolved freely. On mixing the iodizing medium, the colour of the collodion turns immediately to nearly a port-wine colour, but still remains very clear. I obtain a very good film of iodide of silver from the bath, but cannot produce a picture under five or seven minutes, whereas with the same lens, and the same iodizing medium, viz.
| Alcohol | 8 drms. |
| Iodide of potassium | 8 grs. |
| Iodide of ammonium | 4 grs. |
| Iodide of silver | ½ gr. |
I have obtained beautiful pictures in less than one second with collodion prepared by the same (Archer's) process. As I have made a quantity of it, and am unwilling it should be wasted, I have taken the liberty of asking your opinion on the subject. Do you think the collodion is too new, or the ether not good? On pouring the developing solution on the plate (protosulphate of iron), the plate has the appearance of having ink poured on it; but this appearance is removed on the application of the hyposulphite of soda, and the plate remains as clear as when it was taken from the nitrate of silver bath.
J. Cook.
The Céroléine Process.—Have any of your photographic correspondents made such experiments on the céroléine process as to enable them to communicate the results to "N. & Q."?
Is Mr. Crooke's process for preserving the sensitiveness of collodion applicable to all collodions? If not, what collodion is best suited for it?
Silex.
Mr. Fox Talbot's Patents.—-The injunction moved for by Mr. Fox Talbot, as reported in The Times of Saturday last, reminds us of a Query which we have been sometimes asked, and which may just now be brought forward with advantage, namely: If Mr. Talbot's patents extend to the collodion process, how comes it that the earliest practisers of the collodion art had to make their own researches? We know one skilful photographer whose experiments were so extensive before he made any tolerable pictures, that his spoiled glass and cuttings were more than a man could lift.