SCIENTIFIC MISCELLANY.

Otago Witness, Issue 3687, 11 November 1924, Page 66

SCIENTIFIC MISCELLANY.

(For the Witness.) GERMICIDE-DOMED TIMBERS. The superior durability of some woods is found to be due to contained substances that are poisonous to wood-rotting bacteria and fungi, the poisons being mors concentrated in heartwood than in sapwood. PURE ALUM FROM CLAY. In its process of obtaining pure alum and aluminium salts from impure clay, the U.S.. Bureau of Mines first removes the iron and most of the potash by treatment with acid. The iron-free residue readily yields aluminium sulphate, and with some further experiments to bring the process to its highest working efficiency, a considerable cheapening of the products is expected. SOME CANADIAN PESTS. The chief, insect ravages in Canadian forests, resulting in a timber loss of hundreds of millions of dollars in 15 years, are reported by Dr J. M. Swaine to have been: the spruce budworm in Quebec and New Brunswick; the western pine barkbeetles in yellow pine, white pine, and lodge-pole in British Columbia; the spruce bark-beetle in white and red spruce of Quebec, Manitoba, and Saskatchewan; and the larch sawfly in Eastern Canada. TREELESS SPOTS IN FORESTS. The cause of the grassy openings in the pine forests of the south-eastern United States has been a subject of investigation by the Forest Service. The tests made show that the fine soil washed in from surrounding elevations remains saturated with water until late spring, rotting seeds and drowning seedlings, and that if any plants get started the hard baking of the soil in summer kills them by keeping water from their roots. The strong winds, sweeping across these unshielded spaces, may also tend to keep down the trees. LEAD GOES TO THE BONES. When lead is swallowed, even in solution, little of it is absorbed into the general circulation, according to Dr A. S. Minot, Massachusetts physician. Much of that absorbed is excreted by the liver in the bile, but a small proportion reaches the general circulation, and is distributed to the various tissues. The bones show a special affinity for lead, retaining it. When the lead accumulates sufficiently to cause symptoms of poisoning, it is distributed throughout the body, but when it is no longer absorbed, it tends to collect in the skeleton, where it remains as a temporarily harmless deposit. TIN-LIKE ZINC PLATING. The Classen zinc-plating process, of German origin, is designed especially for giving iron a glossy and adherent protective coating of great density. Sheet, tube, wire, screws, nails, and- so on can be quickly covered, and the coating is stated to be perfectly smooth under a powerful microscope, while other zinc p'lating appears irregular and full of holes. On account of the porosity, other forms of plating have necessarily been thick. The smooth new plating resembles tin or silver, and is so much thinner than the old that equally as good protection is claimed from the use of only one-tenth to oncThalf as much zinc. ISLAND CLASSES. The classification of oceanic island® opposed to the British Association by Prof. W. M. Davis offers these primary divisions: (1) Islands in colder seas that have suffered glacial erosion, such as the Faroes; (2) those in cool seas that have undergone persistent abrasion, of which an example is Tristan da Cunha; (3) those in coral seas protected by reefs from abrasion, and modified only by erosion, like Borabora; and (4) those in the margin of coral seas alternately reef-protected in warmer periods, and exposed to abrasion when cooler, a class that includes Bonin Islands. These groups may be subdivided into stationary, rising, and sinking islands. TUBERCULOSIS VACCINATION. Tuberculosis seems to have, received another set-back in the discovery of a protective vaccine. Young children living in the same house with a tuberculous person are especially liable to infection, and Dr N. Raw„ in the British Medical Journal, urges that all such children over one year of age should he vaccinated. He has treated 412 children, ranging from 14 to 14 years of age, who have had one parent .suffering from pulmonary tuberculosis. The vaccine was prepared from dead cultures of attenuated bovine bacilli, and two injections were given, with an interval of two weeks between them. The treatment was given in all cases at the request of a parent. There have been no harmful effects, and so far no vaccinated child has developed tuberculosis. GIVING PROTECTION TO PROTECTIVE SEA WALLS. As a means of protecting exposed shores from the destructive wearing away by shingle and boulders, concrete walls have been tried and found wanting. Such sea-walls are ground down rapidly, but the new plan of giving them a facing of wood seems to promise greatly increased durability. In experiments on the southern coast of England, wood blocks were set in cement, with the end grain exposed. On recent examination, the trial lot ul wood blocks inserted in the wall

showed very little wear, but the surrounding unprotected concrete had been eroded 1£ to 2 inches more than the wood. The blocks had been put in place in 1921. The preliminary test having been so satisfactory, a considerable length of sea-wall has been faced with wood, mostly in cubes of six inches to a side, but with occasional projecting blocks having a depth of nine inches. The blocks were set in neat cement grout. THE EARTH AND METEORITES. The view that the earth consists of an iron core surrounded by a shell of silicate rock is found by Adams and Washington, of the Carnegie Institute of Washington, to have been gaining steadily in favour since its suggestion by Dana in 1873. The theory is based on the calculated average density of the earth, the rates of transmission of earthquake waves, and analogy with meteorites. The average density is greater than that of any known silicate rocks, making it evident that the centre must consist of some material much more dense than the outer shell, and the nickel-iron of meteorites would supply such material. Variations in the velocity of earthquake waves seem to indicate that the transition from a solid core to the surface silicates is gradual, an intermediate zone being made up of a varying intermixture of iron and rock. Threw main groups of meteorites are recognised, the iron-niekel siderites, the mixture of iron and silicates known as siderolites, and the stony aerolites, composed almost wholly of silicates, and, assuming that meteorites represent a broken-up body resembling the earth, the three varieties correspond to the iron-nickel centre, the mixed silicate-iron zone, and the outer crust of silicate rock. Instead of being comparable to a huge meteorite, the earth is like the body broken up to form the meteorites, and its disruption would yield meteorites of all known kinds.