Science Siftings

New Zealand Tablet, 12 May 1910, Page 755

Science Siftings

BY ‘ VOLT’

The Highest Telephone, When it is completed, the highest telephone in the world will be possessed by Italy. They are constructing a line to the top of Mount Rosa, which is about three and one-eighth English miles in height. Queen Margharita has contributed so much toward the completion of the enterprise that the observatory and lodging oh the mountain have been given her name. There are, however, some who maintain that the telephone line will be a failure, in consequence of the difficulty of fixing the poles securely. Burglar-proof Glass. Consul William Bardel, of Rheims, reports that a new French plate-glass has been brought out which is practically burglar-proof. While an ordinary plate-glass, such as ’s usually put into jewellers’ shop-windows, can be smashed by a single stroke of a metal-faced mallet, it is not possible to break this new plate-glass in this manner. In an experiment made, a large piece of cast-iron was thrown violently against the window, but the only effect on the glass was a small hole measuring one or two inches. Several shots of a revolver loaded with jacketed bullets were then fired at the show-window, but the window suffered no damage except that the bullets entered to a depth of a fraction of an inch. The plate-glass which will stand such usage is ordinarily made of a thickness of |in to lin. If desired, even a heavier glass can be made without diminishing the transparency. Peculiarities of Volcanoes. The volcanoes of the Mediterranean, and of the Eastern and Western Coasts of Africa, are all situated on a line, a,nd all the volcanoes of the world have this remarkable linear arrangement. It is as though they were situated on lines of weakness in the earth’s crust, where great fissures had allowed of the escape of the pent-up forces from within. Another remarkable feature in connection with volcanoes is their proximity to the great ocean basins. All the Continental volcanoes lie along the coast line, and the islandic ones are of course situated in the midst of water. This relation of volcanoes to the sea is very suggestive when we remember that the explosive violence of a volcanic eruption is due to the escape of highly-heated steam; in fact, in a sense a volcanic eruption is like a steam-boiler bursting. The popular conception that a volcano is a burning hill is erroneous, for fire does not occur during an eruptive discharge, neither is there any smoke. What has been mistaken for flame is the glow of the molten lava, and the jlust mingled with steam at a distance looks like smoke. A volcano need not be a hill at all; it is essentially a fissure through which super-heated steam, fragments of rock, and lava are discharged with explosive violence. Lightning and Thunder. By counting the number of seconds in the interval between lightning and thunder it is possible to figure approximately how far from the observer is the scene of the storm, Sound travels 1100 ft a second, so multiply the number of seconds by 1100, which will give the distance in feet from the point where the lightning flashed. For example, if 10 seconds have elapsed the distance away will be 11,000 ft, or a little over two miles. It might be added that, as light and lightning travel so much faster than sound, if one survives after hearing the crashing peal he can be sure he is safe. Remembrance of this will dissipate terror. Thunder can be heard a relatively short distance only. Strong cannonading can be heard as far off as 70 or 75 miles, while thunder is usually not farther away than 12 or 15 miles. In only exceptional instances does the interval between thunder and lightning amount to 100 seconds, so that the extreme distance at which thunder can be heard may be put down as about 21 miles. A Peculiar Impossibility. It is impossible to throw a few drops of water on a red-hot stove. The water can never touch the stove at all. What is seen is a few drops rolling rapidly over the surface, gradually getting smaller and smaller until they disappear. If the drops are on a perfect level place one can see under them to the other side of the room, thus proving that they are not in contact with the stove itself. What actually happens is that the bottom of the drop changes at once to steam or vapor on coming close to the hot surface, and this vapor is supplied by the drop as it gradually goes away. So the drop rests on a cushion of vapor until it is entirely dissipated. This state of water is known as the spheroidal state, and is of interest simply on account of its peculiarity and seemingly paradoxical behaviour. The reason why the drop is not immediately evaporated or changed to steam is also very interesting. The water;vapor that intervenes between its under surface and red-hot stove is a very bad conductor of heat, and consequently the full intensity of the heat cannot get to the water itself, only the amount transmitted through the vapor being available for this purpose.