Science Siftings

New Zealand Tablet, 9 October 1913, Page 57

Science Siftings

By ‘Volt.’

A Large Block of Stone. Probably the largest block, of stone ever moved in Australia was moved by explosive force at the Harcourt granite quarries recently. This stone is in on© piece, and measures approximately 60ft long, 54ft wide, and 30ft deep. It contains between 90,000 and 100,000 cubic feet, and weighs nearly 8000 tons. , The preparations for this blast included the blasting out of a gullet 60ft long and 30ft deep along one side of the block. Parallel to the gullet, and at a distance of 54ft, a natural joint runs through the block. The object was to make a break from this joint to the gullet. A hole 4in in diameter and 20ft deep was drilled in the solid stone, and charged with half a hundredweight of powder. When exploded, the block was broken across 54ft of solid stone 30ft deep, and shifted bodily a distance of 4in from the break. . Saving the Dust of Metals. In copper smelting there is an immense waste due to the dust of metals which is thrown out by the smelter smoke'. .One great smelting works in the Western States of America, having complaints of the damage done to the crops of the surrounding farmers due to the deposit of arsenic, copper, etc., spent £200,000, in building long flues to endeavor to get some of the metallic dust deposited from the smoke into such flues, and during the first year saved £IOO,OOO worth of copper in the shape of dust. A few years later analyses were made of this same smelter smoke, and in face of such large saving something like 40001 b of copper, 47751 b lead, 60001 b zinc, 43001 b antimony were still being discharged into the atmosphere in the shape of dust, representing about £BO,OOO worth of metal annually. Now it has been discovered by Sir Oliver Lodge that by means of an electrical apparatus which diffuses electrical currents amongst the fumes, a great part, as much as 90 per cent., of the metal dust can lie recovered by precipitation; and if this process turns out to be satisfactory many millions of pounds per annum will be saved in the shape of such dust. In wool sorting there is a dust which, to the ordinary man would appear absolutely useless. Yet from Bradford alone the Kent hopfields received 1200 ' tons of this dust, which is a valuable fertiliser. The Thermometer. Thermometers are of interest to the great majority only in extremely cold or extremely hot weather. Physicians say that what is called ‘the thermometer habit is apt to be a bad habit in hot weather, when a visible rise in temperature seems to accentuate the heat itself and to increase the suffering. Thermometers are of comparatively recent invention. According to Sir Samuel Wilkes, Fahrenheit constructed his thermometer from one made many years before by Sir Isaac Newton. He invented an instrument for measuring the degree of heat in fluids by taking a'tube and filling it with linseed oil. On • this he marked the freezing point at zero by putting the tube in ice, and in the same way he marked the point when placed in boiling water. The very awkward scale which we now use is evidently that of Newton; for, the decimal system not being then in use, he took the number 12 to denote the heat of the body. This lie found and .made it the'starting point of his scale, both upward and downward. It was some time after this that; - for,the sake of convenience, the. degrees were divided into two, and thus the body heat • was 24 above zero and; boiling point 53. When, . many years afterward, Fahrenheit ■’ made his instrument and used mercury instead 'of linseed, oil, which . wars far more convenient, he again divided these degrees into four, so if the number be multiplied accordingly we have 212 for the boiling point and 96 for the body heat. Fahrenheit, finding he could get a lower temperature than freezing, made this point zero, which brought the number 8 of Newton’s to, 32 of .Fahrenheit... . In this way * the thermometer was constructed. ■ , .X ■■