Science Siftings

New Zealand Tablet, Volume LII, Issue 30, 12 August 1925, Page 62

Science Siftings

(By Voli)

Secrets of the Earth’s Core. With our knowledge of the sun, moon, planets, and stars, we are still totally ignorant, except by inferences which amount to little more than guesses, of the state or composition of the earth’s interior. The deepest coal-mine ever sunk is, to the mass of the/globe, much less than the skin of an apple in relation to the apple itself. Nevertheless, it is hard to escape the conclusion that the earth’s core must be much hotter than anything ever heated artificially by man, although very high temperatures have been produced under pressure. Even if we take it that, according to the experience of mine-sinking, the heat increases one degree for every hundred feet bored the temperature of the earth’s centre would reach 211,200 degrees Fahrenheit. We can form some idea of what this means when we remember that the boiling-point of water at sea-level is no more than 212 degrees Fahrenheit, so that the earth’s centre would be almost exactly a thousand times hotter than the water with which you make your tea. Making a Modern Bell. The method of making a modern bell, such as the 10-ton giant which is to be installed in the new tower of Bristol University, has varied very little, except for the, improvements due to machinery and to new methods of tuning, since the time the monks made their own (writes H.R., in the Daily Express). First the bell is designed on paper, then a core of brickwork is made the required size, and covered with loam and sand. This is formed into the shape corresponding to the inside of the proposed bell by means of an instrument which is worked round and round like the arm of a compass until the right curves are moulded. For the outside shape a cast-iron case is used and lined with baked sand and loam, made bell-shape in a similar manner. Cn this baked lining are chiselled the inscriptions which will afterwards appear on the bell. The case is then placed over the core, leaving a space between the two which is the exact thickness of the new bell, and the whole is securely bolted to a cast-iron plate at the bottom. It is then baked for two or three days in order to get rid of all moisture, since the slightest trace of dampness would cause sparks of the hot metal to fly about during the filling process. Meanwhile the furnacemen have been getting ready, and for several days have been anxiously watching a low furnace containing several tons of bell-metal —an alloy of copper and tin. When the metal has reached the right temperature the furnace is tapped and the molten liquid is poured into a giant ladle and - brought alongside each of the six moulds, which have been placed in readiness down the middle of the “shop.” Then, taking care that the flow is continual, for the presence of one • bubble of air would mean a faulty bell, the fiery metal is poured

into the space left between the case and - the core of each mould. >■ .... After some days, according to the size of ‘ the bell, the metal cools. The case is the 1 !-. • • - (■ lifted , off, revealing the outside of the benjf which is turned over and the blackened core chiselled out. It is now a dull ""color, and the final process is to polish it by means of' t . *7 * >* - • sand-blasting, and to tune it with a special machine, which shaves off portions of the inside until the right note is obtained. It is then ready for mounting, either on a $ steel frame for a peal of bells, or on the steel girder of a carillon, ‘ * ; *-V