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January 2, 1891.] THE PHOTOGRAPHIC NEWS. 3 published in Amde Guillemin’s “Forces of Nature,” translated from the French by Mrs. Norman Lockyer: Colours. Luminous Intensities. Lines Extreme Red ... ... Imperceptible ... A Red ... 32 B Red ... ... 94 C Orange ■ ... 640 D Yellow 1,000 ... ... Green... 480 ... E Blue ... 170 F Indigo... ... 31 G Extreme Violet ... 6 H This table shows the relative luminosity of the spectrum where cut by the eight principal lines of Fraunhofer. The maximum brightness is between D and E, nearer D, and distant from it about one-tenth of the total interval DE. Thus the eye, according to Guillemin, is more than ten times more sensitive to yellow than to red light, and this physiological peculiarity of the eye, which of course is not repre sented in spectrum photographs, has to be considered when selecting the best light for developing room operations with plates which are not orthochromatic. This matter is a serious one for professional photo graphers, because of the injury to eyesight brought about by constant work in the red light of the develop ing room. Mr. William Ackland, an experienced oculist, stated at a meeting of the Photographic Society, held November 30th, 1883, that he had noticed that a larger proportion of photographers than other people had found it necessary to have the glasses of their spectacles changed for others of higher power; he attributed the circumstance to the general use of red light in the developing room. Mr. Valentine Blan chard attributed a weakening of his eyesight to the red light, and Mr. J. J. Briginshaw once stated that, by substituting yellow for red light, his eyes had found great relief, and that, by the former light, he could work a longer time in the developing room, with less inconvenience, than when he operated therein for a shorter time by red light. SUPPLEMENT TO THE PHOTOGRAPHIC NEWS. To-day is issued, as a supplement to the Photographic News, a photogravure print from Mr. Lyonel Clark’s photograph of Dedham Bridge, which won a medal at the last exhibition of the Photographic Society. Mr. Clark is an energetic member of the Camera Club, and the son of Mr. Latimer Clark, the well-known electrician, who has been connected with submarine and other telegraphy from the earliest times. LANTERX Plates.— Messrs. B. J. Edwards and Co. have sent us somespecimengelatino-chloridelantern plates, accompanied by a ready-prepared iron developing solution. We found them to give nice, warm brown tones, and to work in a clean manner, without veil. The magnesium light was used for printing by contact. Messrs. Edwards and Co. also enclosed some gelatino- bromide lantern plates ; they were found to work well in the copying camera, also in contact printing. The quinol developer which the firm recommends gave clear, black images; the pyrogallol developer it recommends we found to give rather warmer tones. THE PHOTOGRAPHIC REPRODUCTION OF LITERARY MATTER. Many tastily executed volumes owe their principal adornments either directly or indirectly to photo graphy, which art is as useful a handmaid to book-writing as it is to many other branches of art. And a few books depend altogether upon pho tographic processes for their existence. As a case in point, we may mention the excellent reproduction of John Burnet’s art essays, which was issued by an American publisher a short time ago. In this case it was, of course, imperative that the illustrations should be exact copies of the originals, or they would have been valueless; and it was, no doubt, cheaper to reproduce the printed matter in the same way than to set up the type anew. The ease with which type can be reproduced by photography was also instanced a year or two back, on the completion of the last edition of the Encyclopedia Britannica. Hardly had the last volume been issued before an American publisher, with that utter disregard for copy right which is a characteristic of the class, announced the whole work for sale at a greatly reduced price. The volumes had been copied page by page by means of the camera, and reproduced in block form by the zinc etching process. But where photography is seen at its best in book work is in the reproduction of old black letter type, or in manuscript volumes. One of these latter now lies before us, and a very remarkable volume it is. The original is in various handwritings, for the book was contributed to by different persons who lived in the sixteenth, seventeenth, and eighteenth centuries. The work—which is entitled, “Arcana Fairfaxiana, or ye Apothecarie, his booke,” in fac simile—is a literary curiosity of great interest, particularly to those who, like photographers, have anything to do with matters chemical. The history of this reprint is curious. During alterations of some business premises in Pilgrim Street, Newcastle-on-Tyne, which had been in the occupation of a firm of chemists for more than a hundred years, a number of books was turned out from a lumber room, and among them was one that attracted the attention of Mr. George Weddell. With infinite care, this gentleman examined the volume and found it to consist of a number of domestic and medical recipes written in different handwritings. By the exercise of unusual sagacity, he succeeded in tracing the work to the Fairfax family, hence the title which he has conferred upon it. Several of the leaves were so discoloured that it was almost impossible to reproduce them by photography, so they were traced and trans ferred to stone ; but, where possible, photography has been employed, so that we have before us the identical handwriting of those who, some of them, “ went down into silence ” three hundred years ago. The book is not only most interesting as containing specimens of the different styles of writing which prevailed at various periods, but is a delightful peep into the domestic