The Optical Magic Lantern Journal (August 1890)

Selections. THE diameter of a lantern condenser should be not less than the diagonal of the clear space within the slide mask. ! A 34in. condenser is large enough for a slide of standard size with circular opening, but for an oblong opening, a condenser of four inches in diameter is necessary.— Andrew Pringle. ma z My advice to amateurs respecting plates is, not to hop from one make to another, but to select a make of plates with a thick evenly coated. film, rich in silver, and of medium quickness, and when such a make-has been found—to use an Americanism—“ freeze to it." —7. Steventon. anes Ir, when developing a lantern plate with hydroquinone, a : little yellowness result, it can be easily removed by a treatment with a solution of cyanide of potassium of the following strength :—Cyanide, two drams ; water, one pint.—W. A. Kibbler. AN album affords amusement for one or two only, a public | exhibition to the many ; but a good deal of the interest derived from the latter is lost from the fatigue of walking round the toom with the back of your head at an acute angle to your spine, and the frequently exceedingly bad lighting of the exhibits. All this is got rid of by using the optical lantern.— D. Wardrop. |. THE things that have helped to make the lantern so much more popular during the last few years are, to my mind— Ist, the simplification of photographic work by the intro-duction of dry plates ; 2nd, the improvements in apparatus, by means of which perfect manipulation and registration can be secured ; 3rd, the compressed gas system being all that can be desired since Beard's small automatic regulators have been invented.— @. R. Baker. ae s In my experience of a number of years in the manufacture of oxygen for the limelight and other scientific pur poses, I have become convinced that the majority ofexplosions are the result of a sudden plugging of the neck of the retort and outlet pipe with the binoxide and decomposed chlorate. There are many cameras now to be had which take small negatives suitable for lantern work ; these are so compact and self-contained that they require no stand, focussing cloth, or other adjunct.—Z. CQ. Hepworth. ss s ALL hand cameras should be practically tested before being issued to the public.— Charles Winter, THE quality of the glass for lantern pictures is a matter of considerable importance, as a slight scratch or air bell would, when magnified on the screen, be very objectionable. —Albert W, Scott. Pd Tue eye knows not how to see until it is taught ; it will look upon objects without seeing them—senseless and vague. It must be taught what and how to appreciate.—C. L. Imac. ee s WHen lantern slides are varnished with collodion, a great brilliancy is given to the picturee—Geu. A. Neleon, Se THERE is a peculiarity about certain plates manufactured for the purpose of making lantern slides. The image, which before fixing appears very thin, acquires great density after fixing. Unless one is prepared for it, this is very liable to mislead.— G. TV. Athins, ia ‘*fixed focus’ Notes and Queries. M. J.—You evidently had more ether in the saturator than it was capable of takingup. The saturator should be drained so as to allow any excess to escape. Ch, Hutchinson.—Instead of cutting the wicks so much as you mention, try rubbing the charred surface with a piece of : paper ; this should enable you to obtain a flame that is not “ forked.” D. 7.—The intensity of the light would in both cases be equal, AL, Evans.—We may have something to say upon the subject in our September issue. Ifand Camera.—Judging by the print you enclosed, the picture is slightly out of focus. If you call the maker's attention to it they will rectify it. The camera mentioned being * one, you cannot alter it in the manner you explain. ’ (. G,--A is nearly twice the price of B ; E would perhaps : answer your purpose best. ’ Cynro,—Replied by letter. Perhaps the new form of oxy-calcium jet mentioned in this number would suit your requirements at the altitude you speak of. J. M. Hick.—We have communicated with the makers, and are informed that the fault was remedied some months ayo. Perhaps the lot you obtained were made previous to the rectification. We have found them greatly improved of late. Inquirer (Ryde) writes: ‘“ Will you or any of your readers kindly inform me if it is a safe thing to use an oxygen cylinder to supply gas to an ether saturator, using a regulator tothe cylinder?’ Reply.—Yes. G. A.—In using Hydrokinone for the development of the Mawson fantern plate, yellow stain may be caused by : (1) Using too strong a formula; (2) if the plate be removed from the fixing solution and exposed to the atmosphere before being quite fixed ; (3) by using the same developing solution repeatedly for a number of plates; (4) if Hydrokinone be kept in solution with sulphite of soda for a long time it will stain badly. R.—We have not heard that the camera has yet been placed upon the market. _ Louis Whitney.—Communicate with Taylor, Taylor, and Hobson, of Leicester ; they have a machine for engraving letters which would doubtless answer your purpose. We do not know the price. Ilenry Hunter writes : Enclosed please find a half plate negative. Kindly mark out the best piece from which {can make a suitable picture for a lantern slide by contact, and I will call for same about the beginning of August, when I intend coming to London. Ansn:e7.—Three very good subjects can be obtained for contact slides. We shall be pleased to see you when you come to town. it, J.asks : What is a photo-crayon enlargement ? Isit an enlargement worked up in crayon? Your reply in ‘‘ Notes and Queries " will beesteemed. eyly.—Photo-crayons are enlargements made from a negative upon a collodionized plate, the deepest parts of the shadows of which must be very thin. This picture is backed by paper, which has previously been hatched so as to give a slight shading. The effects thus produced are very beautiful and stand well. John S. Benham.—We have not heard that the gentleman has returned from America, but as we understand he has several engagements in this country for the autumn and winter, we may expect him shortly. Samuel Hedges writes: A foreign formula contains the following—rc.c. Will you kindly help me by saying in your next what it means in English? Heply.—t c.c. means ; one cubic centimetre, and is equal to 17 minims, or drops.