Volltext Seite (XML)
due to a material substance enveloping the sun, but is a phenomenon of diffraction. Dr. Hastings gives his reason for this theory at some length, and points out that in taking photographs of the corona it is seen to be larger as the time of exposure is longer, showing that the corona extends indefinitely, while it decreases in brilliancy in exact accordance with the mathematical laws of diffrac tion. According to the Athenamm, M. Antony Guyard has devised a photometer of considerable delicacy, dependent on the decomposition of iodide of nitrogen placed in aqueous ammonia, which is proportional to the intensity of light. The volume of nitrogen evolved in a given time is a measure of the amount of luminous radiation. We see that the Academy of Sciences in Paris have accorded a hearty reception to M. Janssen, the French astronomer, and his friends, on their return from Caroline Island, ft would not be amiss if some little official recog nition were made to Mr. Woods and Mr. Laurence, seeing that they, too, have made a long and perilous journey on behalf of the scientific authorities of this country. Herr Stein’s suggestion to employ a Geissler tube of red glass for the illumination of the dark room is scarcely likely to find adoption, at any rate in the ordinary studio of the photographer. A Ruhmkorf coil necessary to the working of such an apparatus could scarcely be purchased for less than three or four pounds ; and there would, more over be the trouble and expense of a small electric battery. Far better would be a tiny Swan lamp of red glass worked by a bichromate battery, a suggestion also made by Herr Stein, but which we brought before our readers eighteen months ago. Senor Carlos Relvas, of Gollega, Portugal, whose name is well known as that of an ardent amateur, recommends the careful preservation of old oxalate developer. To obtain negatives of great density, he uses first an old oxalate developer, then a fresh one, and finally the old one again. When his late Majesty King George IV. was about to sail north in a new craft, upon which he had spent much time and money, a wag is said to have remarked that “ on the fitting up of his yacht the king showed a great deal of taste—and deuced bad it was.” We were reminded of this dictum the other day on looking at a grand collection of “club ” portraits, brought to us by a traveller, who would not rest until we had closely examined the whole number of gorgeously coloured and gilded pictures. He was at some trouble, too, to assure us they were not mere show specimens, but simply the ordinary work of the firm he represented. Dr. Stolze warns photographers not to place too much reliance upon a coloured spirit flame in the dark room, like the flame, for instance, produced by alcohol, in which bromide of strontium has been dissolved. Salt dissolved in alcohol will impart to the spirit lamp a flame innocuous under most circumstances, but then if the light does no harm, it is so faint as to do no good either. Photographing the vocal chords is now an accomplished fact, and it is not likely that enquiring physiologists will stop here. The Journal of the Microscopical Society gives some interesting engravings of an apparatus devised by Herr Leiter and Dr. J. Mikuliez, for allowing the walls of the stomach to be illuminated and examined by the aid of lenses. The electric light is, of course, the source of illu mination, and this is placed at the end of a bent tube, and inserted into the stomach, the observer placing his eye at an objective at the other end of the tube, through which the image is conveyed by means of a right-angled prism, which acts as a reflector to transmit the rays from the side of the instrument up the tube. In the same paper, Dr. J. Oliver describes a successful experiment of examining the interior of the liver by means of a small Swan incandescent lamp, and by an arrangement which is said to give a better light, and develop less heat than Leiter’s system. What ever can be seen by the eye can also be photographed (grant ing, of course, that the illumination is of actinic quality) ; the photographing of the interior of the stomach would seem to be but a matter of ingenuity in regard to the apparatus. We recently spoke with a photographer over the palmy days of photography, that halycon time of 1851-54. His experience was limited to the West Country, but in Plymouth, even so late as the last year, the charge made for a Daguerreotype portrait, quarter-plate, was £2 12s. 6d., while a half-plate picture brought in four guineas. From twenty-five to thirty guineas a week was then the average takings single-handed. And even when paper photographs came first into vogue, a single print from a quarter-plate negative was charged two guineas. But it wasn’t all honey, even in the good old times. “ I remember well my first start with the collodion process,” said our friend. “ I took a first floor drawing-room with four windows, which, with the aid of a sheet mirror, made a capital studio, while my dark closet was a handy cupboard in the bedroom adjoining. 1 remained there a fortnight, and although with some experience of the collo. dion process, I never produced a satisfactory negative the whole time. The plates one and all were covered with spangles, and the film had irregular vine-like markings. The latter, of course, were due, as I learnt subsequently, to insufficient bathing of the plate—streaks in the direction of the dip, they were afterwards called—and the former arose fromiron particles in the water. I paid afortnight’s rent and left, but this was not all my loss ; the landlady requested my attendance in the bedroom, and invited me to explain the presence of certain inky splashes over the furniture which defied all scrubbing with soap and water. My next studio was improvised in less showy quarters, 1 remember.”