SCIENCE NOTES.

Otago Witness, Issue 2408, 26 April 1900, Page 58

SCIENCE NOTES.

—Dr Hall-Edwards, who it will be remembered was one of the first to put the Rontgen rays to., practical use in surgery, and who has now for some years been surgical radiographer to the General Hospital, Birmingham, has been appointed X-ray expert and surgical photographer to the hospital of the Imperial Yeomanry in South Africa. He has devised a portable Rontgen ray apparatus for use on the but his present appointment, is for service in the base hospital at Capetown, where he will not only use the X-rays as an aid to surgery, but will keep systematic records, by means of ordinary photography, of the cases treated. These will serve not only for immediate use, but will be of permanent utility in the literature of military surgery. Dr Hall-Edwards was sent for by the War Office o short time ago, and some negotiations had taken place with regard to a possible appointment in connection witl the army hospitals, when he received the offer from Mr A. D. ITripp, who attended the Prince of Wales after the accident to his Royal Highness's knee, and who is the leading civilian member of the Imperial Yeomanry surgical staff. The appointment Avas confirmed in London, and Dr Hall-Edwards returned to Birmingham to prepare for his departure for the Cape with the rest of the staff, and sailed by the Majestic on February 10. Two set^-s of X-ray apparatus have already been given for use with the Imperial Yeomanry. | — Professor R. W. Wood, of the University ! of Wisconsin, U.S.A., described at the So-'j ciety of Arts the new process which he has devised for producing pictures in colour by 1 photographic means. His process bears a certain resemblance to those, of Ives and Joly, but is quite distinct from either. It is practically an adaptation of the diffraction grating. By using gratings the lines of which arS at different distances apart, different colour effects are obtained, and if a 'plate be ruled with different-sized gratings on different parts of its surface, each grating, when viewed from the same standpoint and with proper optical means, will show a different colour. By a development of this principle and by printing from suitable photographic negatives, such as are used in the now well-known three-colour process, through gratings of different dimensions, Professor Wood is able to produce a nicture which, colourless in

itself, shows colour when viewed by transmitted light through a lens fixed in a suitable position. The process devised by Professor Lippman enables the natural colours of objects to be reproduced by purely photographic means, and without the use of coloured pigments.

— One of the latest ideas in submarine boats is that of an engineer named Rogers. It is a telescopic boat, go that when the after part is drawn in or pushed out by means of hydraulic mechanism provided for the purpose, he' 1 displacement in altered, and so phe ri&es or sinks as required. She is fitted for the discharge of Whitehead torpedoes, and has another peculiarity, in that her conning tower is, so to speak, a complete boat in itself. Should any untoward accident befall the vessel, all the captain and his crew, who are together in the conning tower, have to do is to leave the sinking ship. They disengage tho tower from the foundering hull and float away, perchance 'to safety. — A new process of photography in lelief upon glass, porcelain, etc., has been lately discovered by M. Sekutowicz. He transforms by a direct process a photographic aim into a photoplastic relief, which may be used in the moulding of glass and in analogous processes. The experimenter happened upen the discovery in the following manner. Having hart occasion to reinforce a negative film in a solution of mercury bichloride, he found that the film then presealei a .vuvface having greater relief than usual. In searching for the cause of this action he discovered that the solution had been very much toostrong, owing to a mistake in weighing. Upon repeating the experiment ihe phenomenon again appeared, and by varying the suar.^th of the solutions he obtained a teries of reliefs in proportion to the degree of cor.cGiicration of the bath. After demonstrating this face he at once proceeded to utilise tl.e c'heovery, and first obtained a' pla&ter impre:?icri in the following manner. The film in relief, while wst, is placed upon a block of fine piasterhaving a ptane surface, this having beea previously moistened. The formation of airbubbles between the film and the p!a?ter should be carefully avoided. Ai the cad of a few minutes the excess of wacer is ab?c..rbec! by the piaster, and the film remains ar.ed fiat upon its support, the side in leliel being uppermost. A layer of piaster i-, 'A.en ficnved over this in the v usual wat, i*tid a ipproduction is thus made, which is xrea;eJ by the galyanoplastic procesp. In thii yi,y s mould is formed, which may be applied tc various industrial uses, such as irnnreszion in relief upon glass or porcelain, and also in tho different processes of photo-printing, and the discovery of M. Sekutowicw will no doubt prove of considerable value in these and analogous processes. — English Mechanic.

— What is described as a new method of making oil-gas has been shown to a number of civil engineers and others interested in automobile and tramway traction. It is understood that a company is bringing out the invention, which is of French origin, in England. It is thus described : ''The gas "fountain consists of a plain tin oblong canister, with two tubes projecting from the top. The box, packed with a highly porous, specially prepared wood, is charged with a hydrocarbon liquid, such as petroleum. This is entirely absorbed by the wood. By means of a siphon arrangement of the tube', air passing through the oil. held' by the fibrous absorbent in a finely-divided state, is automatically turned into gap, the uses of which for motor, lighting, heating, and all other purposes to which gas can be applied were demonstrated. — Silhouette photographs by flashlight are made as follows : — Acrosb an open doorway, o." at the opening between two connecting rooms, stretch a white sheet without joint, creases, or folds. In one room (behind the sheet, and at a distance of six or eight, feet from it) arrange everything for a flash expo&ure. A single flash-sheet or small cartridge, or ten grains of powder, will suffice. In the other room pose the subject or subjects as near to the sheet as possible, and give them occupation. Thus two ladies may be sitting, busied with their embroidery, or a girl may be posed, standing, with her violin in characteristic attitude ; or a baby may be seated at table in a high chair. In this same room focus the camera on the subject, lower the gas a little, uncover the plate and lens, and quickly go into the other room (behind the sheet) and make the flash. The result, on development, will be an attractive silhouette, which, printed on Velox or any other paper, will form a very desirable greeting card for a friend of the subject. The theme 'of the silhouette picture may be varied infinitely according to personal taste. Two men playing chess, a child with toys, or a woman trimming a hat are subjects which suggest themselves. This class of portraiture, too, I may add, londs itself admirably to' the humorous side of photography, and some very funny groups may be delineated by means of the silhouette photograph — thus, the shadows on ' the blind of lovers under the mistletoe, "Mrs Caudle's Curtain Lectures," "Mr •Boozey's reception on his arrivel home at 1 a.m. " open out quite a new field for the amateur photographer. — "Iris," in Leeds Mercury.

— Among the scientific inventions of Lord Dundonaki, who led the first relief troops into Ladysmith, is a utensil for burning slow-combustion fuel, which proved of much utility during the late campaign on the Indian frontier. Thi? was known as the "Instra,"' the interior being instratified with an incombustible arrangement of five stratas of substances. In this it is possible to burn powdered charcoal fuel in a safe, portable, and cleanly manner, and consequently it was much in favour in the huge mountain passes, where in previous expeditions po many had perished from the cold. It was Lord Dundonald's ancestor, the famous Admiral Cochrane, who introduced the &yntem of air pressure in tunnelling operations, which was used with so much success in the construction of the great highway beneath the Thames at Blackwall.

— Farmers have obtained the benefits of the telephone syptem in the United States. The North Electric Company, of Cleveland, Ohio, has recently commenced a "farmers' community exchange," by use of which the city exchange is enabled to furnish a service to the farmers in its neighbourhood at a price within the reach of the farmers of the country. At various points are located one of the switchboards. T?rom this point radiate eight or fct'n lines, to each of which are connected several subscribers. Community exchanges are connected by trunk lines to the city exchanges. Patrons are enabled to converse with any of the other subscribers to their own exchange, or, by trunking into the city exchange and from there to any of the other community exchanges, are enabled to reach any of the patrons of the city or other community exchanges. — The story of khaki is one of the industrial romances of the century. . . . Tho, vhg cf^ an olive dye in connection with ihe duffing' of our troops in India dates back for irony years. The tint was devised, in the first instance, by native dyers, who used for the

purpose pigments which they were unable to fix, and also unable to prepare, in a uniform state. A traveller for a Manchester firm was one day taking a railway journey in Northern India, and found himself in the company of an Anglo-Indian military officer. The conversation drifted to cotton drill, and the regimental officer made the remark that the first Manchester man who succeeded in producing an absolutely fast khaki dye would make his fortune. The remark made a deep impression upon the traveller, who upon returning home set to work to study the reason why the olive and brown dyes hitherto used always washed out after a few applications of soc'a. He put himself into communication wi'h a skilful dyer, and the two experts set ihemeelves the ta^k of discovering a method of fixing these dyes upon cotton yarns or fabrics. Many experiments were made, and at length an effective dye was obtained, but, unhappily, it yielded at once to the soap and soda test. Instead of giving up in e'espair, the two inventors pursued their researches, and one day the dyer produced a piece of fabric which upon being tested was found to retain its colour even under the severe application of a caustic alkali. He was requested to try again, and again he failed. Then the two colleagues put their heads together, and went over the conditions once more very carefully, and at length observed that, whether accidentally or not, tfce cloth in which the dye was fast had Leen dipped in a diVh made of a certain metal, whereas all the unsuccessful experiments had been made with a dish of another metal. The invention was assured from that -day, and fortune was'-the result. — Daily News.