SCIENCE NOTES.

Hokitika Guardian, 15 April 1925, Page 4

SCIENCE NOTES.

NEW PHOTOGRAPHIC PROCESS. Topsy-I iirvey methods of developing photographic films and plates. i>\ which the process is carried out in daylight instead of a darkened room, and the film is placed in the fixing bath first and then in the developer, has been shown possible as the result oi experiments made at the Wagner Free Institue of Science by Dr Henry Hellman over a number of years. I lie plate or film is first placed in a dilute solution of sodium thiosulfate, commonly called “liyno.” This is done in a dark-room. Although il seems entirely transparent when brought out into daylight. it is placed in a special developer and the image appears. The inventor of the process claims that tins is a great advantage since _tlu*,c is pleiity'of light to observe the at lion. In photography, tho silver luomide is fixed with some substance such as gelatine that can he spread out in a thin Inver oil a glass or celluloid suppoii. This forms tin* plate or film, and, "hen exposed in the camera to the image formed on it by the camera lens, the parts struck by the light, are atlected, while the others arc not. No change is apparent if the film is then examined, , but this invisible or latent image may be brought out by development, which changes"' I lie latent image into one of very minute particles ot metallic silver, This process leaves the parts that, "etc not reached by the light as unchanged silver bromide, so it is necessary to remove it by fixing. Sodium fbiosuliate dissolves the silver bromide, but. not tho metallic silver, and the result is the familiar “negative.” with dark areas corresponding to the lights ol the ori-

ginal scene. This being the case it would seem Unit if | lie silver bromide were first dissolved away by fixing, the lalenl image, supposed to be due to a cluing" in the molecule, wmdd go with it. bill Dr Leli'iuau lias demonstrated Unit it persists in the gelatine itself. The ordinary developer lannot be Used, but by means of a special one containing mercuric chloride or bromide, metallic ltn'reury is deposited where the silvoi would have been if i be plate had been treated in the usual manner, and the negative may be printed in Lise ovdinarv wav. ' FINGER PRINTS INHERITED. Finger prints, the most certain <d it lv it I ilbsd ion marks, arc hereditary, (tie's di tim live pall'TO i Id.e (bat ot one's parents, and "ill lie passed on to future generations "ilh relatively little change. These results are announced by Mile Kristine Hointevie, of the Rival Frederick University, after exhaustive statistical study of the finger-print records of I lie Oslo (Norway) Court of dustieo, which were put, at her dosposal. Carrying her researches into tlie wider relationships ol the human family, Mile Ruimevie lias discovered that there is a resemblance between the finger-print types ill related races - the nearer the relationship, the closer the resemblance. Finally, the similarity between the linger prints;

of apes follows the same rule of kinship. SPONGE IRON. The production of sponge iron, a finely separated form of the metal, and very useful in chemical and metallurgical industry, has been made possible on a large scale by researches comluctep at Seattle by the Bureau of Mines of the U.S. Department of the Interior. The process depends on the fact that most iron ores are oxides of iron, and that if the oxygen can be extracted at temperatures so low that the iron does no fuse or run it is left standing as a very fine poms metallic sponge, presenting very large areas of free surface, on which the reactions of chemical manufacturing processes can take place. The process also premises to render possible the profitable production of iron from low-grado ores and furnace wastes. During the past year a furnace using the new process was operated commercially at Silver City, b lah, producing about three tons of sponge iron daily.