The Optical Magic Lantern Journal (December 1893)

190 ~ The Optical Magic Lantern Journal and Photographic Enlarger. carry them unless incased in some covering of more elasticity than the cylinder itself, We think from the evidence adduced that users of cylinders need have no apprehension of danger. In this case only the sudden shock acting upon an exceptionally brittle cylinder caused the explosion. —:0:— A Story of a Safety Jet. OxcE upon a time, many years ago, at a meeting of a society called the London and Provincial Photographic Association, a manufacturing optician, whose name was and is Mr. Charles Darker, was ‘‘ working” the optical lantern, when an incautious member asked his opinion as to the best safety jet for the mixed gases. Mr. Darker replied that if anyone present wished to buy a safety jet he should be happy to make one for him and to send in the bill ; but his advice was to go without one and to take | the risk. | on the occasion, and the opportunity was seized “Why,” said Mr. Darker, as nearly as we » can remember his words, ‘my father in vented the most perfect safety jet ever made | on this earth, and was proud of it; it wasin his thoughts by day and in his dreams by night; one fine morning it was finished, and one of my father’s best customers came in saying that he wanted to buy a safety jet. He was told that he had arrived at exactly the right moment, for the most perfect safety jet ever made was about | to be tested, and he could come into the workshop to see the experiments. A bullock’s bladder was then sent for, and everyone knows that when a bullock’s bladder is wanted no | butcher ever has one. After a great delay and trouble, however, one was obtained, all covered with fat and blood. It was then filled with mixed oxygen and hydrogen gases, and put behind the wonderful safety jet. My father in high glee stood on one side of the jet, and the customer on the other. The mixed gas was turned on, a light applied to the jet, and then —O, Lord! The customer wiped the blood to ask him for particulars as to how they produced gelatino-primuline lantern slides. Dr. Reynolds had drawn attention to the value of such slides in the two points that they are free from grain, and can be obtained of different | brilliant colours at the will of the operator. The following is a formula for producing lantern transparencies :— A solution is made consisting of :— Gelatine ... 300 grains. Primuline 80. ,, Chrome alum... soe O° as Water 1 pint. This is freed from air bubbles by any of the ordinary means adopted for that purpose in making gelatino-bromide emulsions, then clean glass plates are coated with it at a temperature of 60° Centigrade. The plate is then put ina place free from dust to dry, and until the next stage is reached it is insensitive to light. The sensitising bath can be made up in various ways. It amounts to this: it is an acid bath just sharp enough to the taste, and can ' be made with any acid, such as tartaric, citric, oxalic, or any mineral acid, and then nitrite of soda is added in sufticient quantity. So longas nitrous acid is present, which can readily be ascertained by the smell, it is sufficient. What the inventors recommend is an acid bath, containing from one to two per cent. of any of the acids mentioned, to which nitrite of soda five per cent. solution is added from a stock bottle : In small quantities as required. As regards lantern slides, the quantity of ' primuline is varied according to the density and fat off his face, and went away without | buying father’s safety jet.” —:0:— Gelatino-Primuline Lantern Slides. Dr. J. Reynoips, a Brixton physician, has recently been experimenting with the primuline | process, and a few days ago brought the results before the Brixton and Clapham Camera Club, of which he is president, Mr. C. F. Cross, of the firm of Green, Cross and Bevan, . the patentees of the primuline process, was present required, and the printing has to be done from transparent positives, not negatives. A half per cent. solution of primuline will do for some subjects, especially when the film of gelatine is thick; when the film is thin, a two per cent. solution of primuline gives a nice result; the operators must display a little judgment in the matter. The nitrous acid in the sensitising bath “« diazotises ’ the primuline; the plate has then ' to be washed in a stream of water for five minutes, and allowed to dry. If the film looks cloudy, the cloudiness can be removed with a soft brush or a tuft of cotton wool; the sensitised plates will keep for some days, but it is better to use them as soon as possible. Some of the plates are quite transparent, others are slightly opalescent. The speed of the plates bears some resemblance to that of albumenised paper. The exposure may be perhaps five minutes in sunshine, and much longer in diffused daylight ;