Science Siftings

New Zealand Tablet, 26 June 1913, Page 47

Science Siftings

By * Volt.’

A Big Undertaking. \ The Sydney Public Works Committee have come to a . decision on the subject of the means of communication, over the harbor between Sydney and North Sydhey, which has been under discussion for so long. After the consideration of a hug© mass of evidence that v had been tendered on the various schemes submitted, it was decided that, in the opinion of the committee, it is expedient to connect Sydney and North Sydney by means of a bridge, and they recommend the adoption of the scheme, carrying four ,lines of railways, one 35ft roadway, one 17ft 6in roadway, and one 15ft roadway, at an estimated cost of £2,750,000. 1•; V • a-.-.’ A New Variety of Glass. While the new variety of glass known as quartz or acid glass is valuable from the fact that it resists heat and does not crack when suddenly heated and cooled, so that various apparatus can be made of it, such glass has a tendency to crystallize when heated for a long time near the melting point. This makes the glass mechanically weaker, and it changes more with heat. A new glass made by M. Thomas does not become deyitrified in this way, and he obtains it by using silica to which is added a small amount of certain metallic oxides, these being acid oxides, especially zirconium or titanium oxides. As small an amount as 0.1 per cent is enough to increase the mechanical resistance by 20 to 50 per cent., and the general properties are .much superior. How Birds Sleep. The sleep of most wild creatures, whether birds or animals, is light; there is too much danger round to make sound sleep safe. The author of A Gamekeeper s Note-Book, who made some very interesting observations on sleeping birds, found out that the perch-roosting birds always keep head to the wind. If a rook alights in the home tree in a light wind, he swings his head into the wind before alighting. * So when .wood-pigeons come home before the wind, they pass over their roosting-trees and then beat up into the wind. At rest, the bird doubles its knees, as it were, which causes the toes to contract, the weight of the body resting chiefly on the breast and outspread wings— on the eggs if in a nest. The legs and feet have sinews which work an automatic locking action of the claws, so that, roosting with knees doubled up the feet grip the branch unfailingly. . ’ Preservation of Stone. The newer portion of the stonework of Dunfermline Abbey, in Scotland, restored in 1818, has recently been found crumbling and deteriorating, so that measures for its preservation have become necessary. A solution of silicate of soda or liquid glass applied in two coats to the surface of the stone after scraping off the outside surface, followed by one coating of calcium chloride, has been followed by excellent results, and it is said preserves the stone for forty years without renewal. As the cost of the solution is very little, the application might serve to. protect the older stone churches of America from decay. It might also be noted that while this stone used in 1818 needs care and protection, the original stone used in the erection of the older portion of the nave of the Abbey, built A.D. 1040, still remains in a fair state of preservation, the explanation being that this enduring stone was brought by the Normans or Romans from distant parts.