G. C., claiming for Le Gray the merit of the first use of collodion upon glass, states that a pamphlet upon the subject was published in 1850, and which was translated into English at the same time. Will he oblige me by stating who published this pamphlet, or where it may be obtained? I have heard this statement before, and have used every endeavour to obtain a sight of the publication, but without success. Were the facts as stated by your correspondent, it would deprive Mr. Archer undoubtedly of the merit which he claims; but from all I have been able to learn, Le Gray mentioned collodion as a mere agent for obtaining a smooth surface to paper, or other substance, having no idea of making it the sole sensitive substance to be employed. I have been informed that in Vienna, early in 1850, collodion was tried upon glass by being first immersed in a bath of iodide of potassium; and it was afterwards placed in a second bath of nitrate of silver. These experiments had very limited success, and were never published, and certainly were unknown to Mr. Archer.
H. W. D.
Mr. Weld Taylor's Process.—In your 167th Number (Vol. vii., p. 48.) is a communication from Weld Taylor on photographic manipulation, which, in its present form, is perfectly unintelligible. At p. 48. he says: "Twenty grains of nitrate of silver in half an ounce of water is to have half an ounce of solution of iodide of potassium of fifty grains to the ounce added." Now this is unnecessarily mystifying. Why not say: "Take equal quantities of a forty-grain solution of nitrate of silver, and of a fifty-grain solution of iodide of potassium;" though, in fact, an equal strength would do as well, and be quite as, if not more, economical.
In the next place, he directs that cyanide of potassium should be added drop by drop, &c. It
is to be presumed that he means a solution of this salt, which is a solid substance as usually sold.
What follows is so exceedingly droll, that I can do nothing more than guess at the meaning. How one solution is to be floated on another, and then, after a bath of nitrate of silver, is to be ready for the camera, surpasses my comprehension.
Also, further on, he alludes to iodizing with the ammonio-nitrate (I presume of silver). What does he mean?
Geo. Shadbolt.
Dr. Diamond's Services to Photography.—Sir, We, the undersigned amateurs of Photography in the city of Norwich, shall be obliged if you will (privately, or otherwise, at your own discretion) convey to Dr. Diamond our grateful thanks for the frankness and liberality with which he has published the valuable results of his experiments in the pages of "N. & Q." We have profited largely by Dr. Diamond's instructions, and beg to express our conviction that he is entitled to the gratitude of every lover of the Art.
We are, Sir,