SCIENCE NOTES.

Otago Witness, Issue 3278, 10 January 1917, Page 57

SCIENCE NOTES.

—New Use- of X-Rays. A report comes from Switzerland that successful experiments have been carried out "in photographing the iron reinforcements of concrete with Routgen rays." O; recent years, ferroconcrete has become marvellously popular for the framework of big buildings; but, unfortunately, the nun is embedded in the cement so completely that it is impossible to keep it under observation, and, for all that, engineers know to the contrary, rust may corrode it to a degree which will upset all calculations as to its reliability as a mainstay. Sir Hugtt Bell, when he was president of the Iron and Steel Institute, pointed out that thousands of buildings were being erected of iron and cement, in Europe and America, "under conditions of profound ignorance as to what w;:s going to happen to the iron iii the future." Perhaps our ignorance will be dissipated by X-ray photographs, which will enable the condition of the hidden metal to be ascertained at any moment, and thus prevent what might otherwise be appalling disasters by building collapses. —Analysis of Dust.— In the October i.-»ae of Science . R. Roes gives a duaiit <i account of a v. t analysis carried ou. bv him. The »>utjpie selected was that ivhich had aceumuidt i on the bookshelves ii the ijiii ot a large library, anil ,-. as collected liitrefrom by means of a vacuum el ..;.:. The microscopical examination showed that human hair was* pre.-en! in the dust, as also was other shorter hair, and wool and cotton fibres, the latter no doubr. produced by the wear of hats and clothing. i< ly wings wero detected, and sand grams were also present, the fine sand having oecn carried in on clothes and boots. It was also found possible, with the microscope, to determine that fragments of wood, paper, string, and celluloid were present, the product of the slow and scarcely perceptible wear of tables, b00k.% and bookcovers. Pieces of finger-iiu.il were detected, and alto metallic iron and leather. The iron dust was separated out by means of a magnet, and was presumably from the wear of nails in the shoes of visitors. When the dust was chemically analysed it was found that there was about 16 per cent, of carbon present, mainly contained in tho wool, cotton, and leather, together with the paper dust and the smoke from nearby chimneys and locomotives. Th« amount of nitrogen was comparatively high, over 1 per cent., chiefly present in the"hair, nail's, and other organic substances. On heating tlte dust it was found that 40 per cent, was able io be driven off, leaving 60 per cent, of ash. This high content of ash waß traceable to the amount of iron, aluminium, lime, soda, and sand present, some, no doubt, carried in on clothes, etc.. while she remainder would be due, to the wear of floor, shelves, and walls. Some common salt was present, and was considered to have been derived from the drying of perspiration, which had gathered on books, etc. Of greater interest, however, is the account of the various germs that were recorded in this examination. "Tho bacillus coli communis was found. It may have come from several sources, the most probable one being the hands, while handling books. The bacillus might also be present, because of the roughing, sneezing, and, possibly, the expectoration of people using the library. The total number of bacteria in the dust of such a confined spice as a library would naturally be high, as the dust would cat eh the bacteria and have a tendency to hold them. One of the chief points of interest connected with this analysis is the presence of the bacillus eoli communis. Where this organism survives, more harmful bactci ia might also remain, such as those producing cholera, typhoid fever, diphtheria, ami especially tuberculosis, which hitter disease is csns-vl by a bacillus especially able to resist the sterilising influence of drying."