Volltext Seite (XML)
24 THE PHOTOGRAPHIC NEWS. [January 9, 1891. occasion requires. If, then, you take this normal deve loper, halve the pyro, and double the water, you will have what you may regard as a very fair normal developer for interiors; not a developer which will develop every interior you take equally well, but one which will require to be constantly varied to suit the subject, and which may, nevertheless, be looked upon as your normal deve loper. It is some years since I used plates for any kind of work, but to those who do use them I would say, never take an interior without backing the plate. There are many methods of backing, and it will be enough if I men tion that, for my part, I prefer black varnish. This, when dry, is always hard and clean, and, before development, can be removed with the greatest ease with cotton-wool and turpentine. It is only necessary to clear away the central portion on the plate, leaving that round the edges to wait until after fixing. One word more as to the time of year for interior work. Some time ago I did a good deal of work late in October, and, although the weather was exceptionally bright, I found, on development, that most of the films were under exposed, more especially those taken early in the morning and late in the afternoon. The explanation is, I think, that the light, though bright enough to the eye, is never theless weak, the reflected light inside the the buildings is feeble, and, as a consequence, the shadows are always black, and the contrast between them and the high-lights much greater than in summer, when a flood of light is reflected from every part of the interior. Anyway, the practical result of my failures was that I decided that, when the sun set at six o’clock, it was time to stop taking interiors.—Camera Club Journal, A BURST PRESSURE GAUGE. The other day an action was tried which is of great inte rest to all lanternists, for it arose out of the bursting of a pressure gauge whilst in situ on an oxygen gas cylinder. The accident unfortunately resulted in the operator los ing the sight of one eye, and the sight of the other has since been endangered through what doctors term “ sym pathetic action.” The bursting was not due to any explosive mixture of gases, but simply and solely to the pressure exerted upon the inner tube of the gauge by the compressed gas. The gauge had been tested three or four times previously to being sent out, and the defendants, Brin’s Oxygen Company, pleaded that this was the case. They further pleaded that they were not the makers of the gauge, but that it was an article generally sold as a pres sure gauge, and also that the contract between them and the plaintiff was for the supply of a guage in general, and not for a gauge for a specific purpose. In the end the plaintiff gained the action, and, by previous arrangement, received from the defendants £325 damages. There is always, unfortunately, a suspicion, when any vessel constructed to bear a great pressure is said to have been tested to an extent far beyond that which it will normally be called upon to bear, that the test itself may possibly have weakened its walls, and caused a strain which may at some future time bring about disaster. This may have been the case in the present instance, or the accident may, perhaps, be accounted for by some flaw in the metal tube which forms the main part of a pres sure gauge. But it is difficult to trace the exact cause of the disaster, and we can only surmise that it may have been due to one of the circumstances suggested. We can, however, offer a hint to the makers or owners of these gauges, whereby danger from a ruptured tube would be obviated. It is assumed that we are writing of the common pres sure gauge made with a strong brass casing, and contain ing a Berdun tube. Should this tube burst, the brass case immediately becomes filled with gas, and the glass front, being the weakest part of the structure, is forced out, and its fragments deal destruction around, as in the unfor tunate case already cited. We have before heard of a glass being smashed in this way, but luckily with no evil results to the manipulator, and whatever be the actual cause, it is evidently an accident that may happen to any one using a gauge of this description. We suggest, as a preventive of injury from such an occurrence, that each gauge should be provided with a safety valve. This might take the form of an opening in the metal case, or the said case might be made of brass perforated in an ornamental style. The gas would then, in case of accident, find a ready means of escape on every side, and the glass front would remain intact. Until such a plan be adopted it would be as well if all users of such gauges were to pursue the course which we have always followed, of turning the face of the gauge away from us when turning on the gas valve. The turning of the valve should, moreover, be quite gradual, so as not to put any sudden strain upon the gauge. The same pressure gauge may be used for both hydrogen and oxygen bottles; but as it is now the custom—a custom, by the way, which is much to be commended—to furnish the former with a left-hand thread to its screw nozzle, a left-hand threaded adapter will be necessary before the gauge can be attached to that bottle. The section of the Berdun tube is so small that there is really no danger from explosion if the two gases should get mixed within it; but, practically, the time occupied in moving the gauge from one cylinder to the other will give ample opportunity for it to get clear from any residue. The junction points between gauge and cylinders should never be oiled. A case of ignition of gas is on record which was traced to the heat caused by working a metal flange against an oily leather washer. South London Photographic Society.—At the meeting on January 2nd, at Hanover Hall, Peckham, Mr. Howson gave a demonstration of lantern plates. The next meeting will be on January 16th, when Mr. Warnerke will give a demonstration on “ Mechanical Printing as Applied to Photography.” Society of Arts.—The following are the papers to be read at the meetings of the Society of Arts after the Christmas recess :—J. F. Green, “ Steam Lifeboats ” ; A. G. Green, C. F. Cross, and E. J. Bevan, “ Photography in Aniline Colours”; Carmichael Thomas, “Illustrated Journalism”; T. Emmerson Dowson, “Decimal Coinage, Weights, and Measures ” ; Sir Roper Lethbridge, M. P., “ The Proposed Irish Channel Tunnel” ; Wm. Topley, F.R.S., “The Sources of Petroleum” ; Colonel Sir Charles Wilson, K.C.B.,K.C.M.G., F.R.S., “Methods and Processes of the Ordnance Survey ”; E. J. Ravenstein, “Lands available for Colonisation” ; Prof. J. J. Hummell, “Fast and Fugitive Dyes”; William Robinson, “The Use of Petroleum in Prime Motors”; H. Newman Lawrence and Arthur Harries, M.D., “Electricity in relation to the Human Body ” ; J. Harrison Carter, “Milling Machinery”; F. H. Cheeswright, “Breakwaters.” The next series of Cantor Lectures will be by Mr. A. J. Hipkins, F.S.A., on “ The Construction and Capabilities of Musical Instruments.” The course of three lectures will com mence January 26th.