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158 THE PHOTOGRAPHIC NEWS. [April 3, 1868. having an important bearing upon the excellence of their productions. The best work will scarcely be produced when the system is in the exhausted and depressed condi tion which is the inevitable result of the continuous breath ing of an atmosphere charged with the vapours of ether and some other substances used in the daily practice of photo graphy. ACTINIC LIGHT TRANSMITTED BY DIFFERENT KINDS OF GLASS. Wb have been favoured by Mr. Gaffield, of Boston, United States, whose valuable experiments on the action of sunlight on glass we recently brought before our readers, with an in teresting photographic print illustrating the degree of light transmitted by certain samples of glass he has examined. In this instance the experiment was intended to determine the degree of chemical action exerted by light after passing through certain samples of new glass. Fourteen examples of glass, each four inches by two, were placed side by side, duly labelled so that each should in printing register its own description on a sheet of sensitive paper, and sub mitted for three minutes to direct sunshine; and the print before us presents the result of the experiment, which is curious and interesting. One half of the sheet was covered with glasses of the colours of the solar spectrum in their due order—-red, orange, yellow, green, blue, indigo, violet. The nature of the colour ing matter used in the respective samples is not stated, and we know that this is an important element in the power of the glass to transmit or obstruct actinism; but we assume that the glasses were selected each as pure and bright examples of its colour. The red, orange, and green have, during the exposure in question, entirely checked the trans mission of actinic light, and no action whatever has taken place on the paper; whilst, curiously enough, the yellow shows a delicate tint of grey, indicating decided action of light. Blue, of course, has transmitted the most actinic light of any of the coloured samples ; indigo, however, being scarcely inferior in its power of transmitting light. Violet obstructs a very large proportion of the light, the blue having transmitted at least three times as much. The other por tion of the sheet is covered with samples labelled as follows : black, porcelain glass, Belgian sheet glass, Belgian sheet ground, American crystal sheet, English crown, French white plate. The black glass, as might have been antici pated, obstructs the passage of actinic light entirely. The porcelain glass, which is the American term for opal pot metal, transmits light in a degree slightly superior to the violet glass. The chemical action appears not to have been retarded in any appreciable degree by the grinding of the Bel gian sheet, as whilst that glass unground transmits the light decidedly most perfectly (the paper being appreciably blacker under it than elsewhere), the same sample ground does not appear to transmit light in any degree less than the American, English, and French clear samples. This is very curious, and requires explanation, as ground glass is generally found to obstruct a very large proportion of light—in some photo graphic experiments as much as 60 per cent, of illuminating power being cut off when the light has passed through ground glass. English crown, American crystal sheet, and French white plate, appear to transmit actinic light in about the same degree, and decidedly more perfectly than blue glass. The Belgian sheet is, however, decidedly the most perfect sample of those tried in the illustration before us. This accords with former experience which has come under our notice regarding this glass, which is also one of those least liable to change. Mr. Gaffield informs us that he is still at work upon his experiments with the changes effected in glass by the action of sunlight. The photographic illustration of the varied degrees of change produced by exposure during various periods, from a day to a year, are sufficiently marked for de finite observation ; although even in a year, in many cases, the alteration is very slight. In the final chart of results, showing the progressive changes in a period ranging from one year to ten, a most valuable record will be secured, for which the photographic community will be deeply indebted to Mr. Gaffield, whose valuable labours will doubtless direct attention to this subject—hitherto so little considered—in a degree commensurate with its importance. ECHOES OF THE MONTH. BY AN OLD PIOTOGRAPIIER. Health of Photographers—Disordered Nitrate Baths, and Modes of Restoring them—Photography without a Nitrate Bath—Rewards to Inventors, and Secret Processes — Presentation Prints—The Edinburgh Committee on M. Salomon’s Prints—Societies. The effect of the practice of photography upon the health ot its devotees, to the discussion of which you have recently opened your columns, is a question which touches the inte rests of the majority of your readers, amateur or professional, very intimately. Your correspondent “ Hypo(chondriac),” who thought the complaints of photographers who suffered from ill-health should be answered with good-natured railery, is doubtless one of the fortunate persons who enjoy good health. “ He jests at scars who never felt a wound.” But it has been my fortune to know a good many professional photographers who have persevered manfully in the dis charge of onerous duties in spite of a sore amount of suffering and debility, charged, if not due, to the pursuit of photography ; and I have further known zealous amateurs who have been absolutely forbidden by their medical men to apply themselves longer to their favourite pursuit. The question, it cannot be doubted, then, becomes a very important one : Is the practice of photography injurious to health ? We know well that many trades have their espe cial diseases: the painter suffers from the action of lead salts ; the grinder from the dust of the metal he polishes; the looking-glass maker from mercury; the lucifer-match maker from phosphorus ; the electro-plater from cyanide; and a host of others incur, from the varied special causes involved in their daily occupations, sufferings which em bitter life and bring on early decay. Is photography legitimately chargeable with any of these things ? This ques tion will, I hope, receive a conclusive answer in the course of the discussion. For my own part, I think not; and whilst I know that many photographers suffer ill-health from causes arising out of the practice of their art, I do not think that photography is an unhealthy occupation per se. That it is made so by ignorance, thoughtlessness, or recklessness in many cases, however, there cannot be a doubt. I have the happiness of knowing a very large number of the ablest men in every branch of our profession, and I can scarcely remember one who does not suffer seriously at times from debility; but I am inclined to believe that it is traceable, in almost every instance, not to the prudent practice of photography, but from over-taxing themselves: working anxiously as well as energetically. With the successful, the struggle to excel; with the unsuccessful, the struggle to exist; with all, the heat of the glass room, and the worries attendant on the duties there : the varied effluvia of the dark room, and the anxieties occasionally arising from pinholes, matt silver stains, fog, splitting films, dissolving films, hard varnish, bad paper, &c., operating on the nervous and irrit able temperament, which is common amongst photographers —all these things are necessarily common causes of ill- health incident to, but not necessarily arising out of, the practice of photography. The discussion of the question must have the good effect of making photographers a little more careful in the handling of dangerous poisons, and a little more considerate, probably, of the ventilation of the dark room. The majority of dark rooms have anything but an agreeable atmosphere. Joey Ladle, in Dickens’ last Christmas story, states that taking in the vapours of wine