We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.
Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.
white, because highly diluted solutions are incapable of colouring gelatin, while copper sulphocyanide mordant, by which the image is formed, attracts and accumulates the colour and produces very intense images, so long as the treatment is sufficiently prolonged.
This method of obtaining monochromes by means of well diluted dyeing solutions provides images of insuperable regularity and perfection, as any one may prove by experimenting on a piece of positive film or on an ordinary slide.
Films must not be perforated beforehand, so that the colour may not pass to the other side; after producing one series of monochromes, the green for instance, on one surface, the series of red monochromes is produced on the other side. No disturbance likely to protract the operation need arise since the work is practically automatic, and a little expeiience is sufficient to show how long it ought to last.
The treatment could be done very rapidly if relatively concentrated dyeing solutions were used, but this would produce a general colouring of the whole surface and a supplementary treatment with acid permanganate or neutral permanganate would be required to rid the photograph of the general colouring.
But this method, as I have had occasion to prove, always compromises the chiaroscuro to some extent, especially as there is a difference in the resistance of the two colours to the oxidizing action of the permanganate.
Tri-chromatic films.
The eminent chemist and photochemist, Prof. Seyewetz called attention in No. 4 of the Review to the Audibert trichromatic process, which also makes use of a double-faced positive film, producing thereon in the first instance two images (in this case one with rhodamine S. and the other with methylene blue) and superposing a yellow image thereon.
Leaving aside the optical and mechanical considerations which have been dealt with by Prof. Seyewetz, I would point out that tri-chromatic synthesis by means of the final addition of a
687 —