SCIENCE SIFTINGS

New Zealand Tablet, 30 January 1919, Page 46

SCIENCE SIFTINGS

By "Volt."

Painting a Liner. One of the biggest jobs, indeed, in connection with a warship or the big liners now being used as transports is giving them a fresh coat of paint. To paint these big ships hundreds of thousands of gallons of paint are required every year, and the paint bill alone of a big shipping company runs well over four figures a year. About 20 to 30 men on each ship are often kept busy putting on the gallons of paint. Most of the large companies used to have their liners repainted at the end of every voyage, or, rather, at the end of every double voyage. The amount of surface that each liner had to have painted was very nearly two and a half acres, so painting a big ship is literally painting by the acre. A warship has to be- painted regularly, for otherwise her life would be considerably shortened, and she would fall to pieces from corrosion. Her outside plates would be simply eaten through and through. The greatest trouble is with the bottom of the vessel, which rapidly, gets encrusted with barnacles and seaweed. This growth on the bottom of a ship is really enormous. The pre-war cruiser Champion, for instance, was taken into dry dock and thoroughly cleaned after serving as a training ship for some years in the. River Mersey. Over 40 tons of mussels alone were removed from the bottom-, and it took a gang of men a week to clear away the growth of seaweed and barnacles. The Domestic Poker. The domestic poker, plain in the kitchen and polished in the parlor, is falling into disrepute as a coal-wasting instrument. In these days of fuel shortage it should be put away, buried, or used as an allotment tool (says an . exchange). There are scientific reasons for the abolition of the poker. Many, if not most, coals burn quite as well without its application. Other coals, particularly those of the anthracite type, if stirred with the poker will not burn at all. Combustion experts have proved that it is radiation only that counts in the warming of a room. It is the stoppage of radiation which accounts for the commonly observed phenomenon of a general movement of chairs towards a fir© still burning brightly and for the vigorous application of the poker. Poking the fire certainly causes the coals to blaze, but not to radiate; and the heat engendered by combustion passes up the chimney. The fire should be left alone, and the firebricks, which every patriotic householder should have put in his grate, will do the radiation and will warm the room. One pound of coal contains about 12,000 heat units, or sufficient to heat a fairly large room for one hour in the dead of winter. In the ordinary wasteful type of household grate about three pounds of coal are used, because 8000 of the heat units go up the chimney and only 4000 heat units pass into the room. Therefore, those who indulge in the habit of poking the fire—it is only a habit, and a bad one— do well to remember when tempted to take the poker in hand that with coal at £2 per ton, for every ton of coal burned in the domestic grate they are sending £1 6s 7d of hard-earned money up the chimney without gaining any return in the way of heat to the room.