Science Siftings

New Zealand Tablet, 15 February 1917, Page 56

Science Siftings

‘Volt.’

The Depth of Niagara. ' ~ _ The depth of the whirlpool rapids in the Niagara River just below the falls has been estimated as anywhere between 250 and 1000 feet, but as no boat can live in the rapids it has been. impossible to verify this estimate. } Engineers now propose to take .a • series . of soundings from: a 'passenger: aero car line constructed 200 feet above the water. 'A* weight of 5001 b will: be used, or heavier if necessary. A similar uncertainty.; prevails as to the depth of water immediately-under the falls, the strength of the current I interfering with the sounding lines. ; - r Door Wedge Rings Bell.Placing a wedge under a door is one of the most efficient means of closing it, for pushing upon the door from the outside only increases the" effect of the wedge. A convenient device of this kind is made of metal and it not only serves to wedge the door, ' but also contains a mechanical bell mounted on the same base and behind the wedge in such a way that pressure on the face of the wedge causes the bell to ring. The base carries a set of short points underneath, so that it can be put in place* and grips upon the carpet or flooring so as not to slide out of position. Such a device can be carried in the pocket, and it is recommended for travelling. Tunnels Under Rivers. There are now many . great rivers with tunnels under them. The first attempt to make a tunnel under a river of any size was the Thames' tunnel in London, which was built by the famous'engineer Brunei. He had so much trouble with the water that oozed through that he came near giving up the job as impossible when he happened to see a piece of rotten wood into which a worm had bored under water. As the worm ate its way into the wood it left a deposit like lime all around the hole, and this got quite hard and waterproof, so that the worm could always get out the way it came, and the hole remained true and firm. Brunei did the same thing. He made large steel tubes and pushed them into the earth, and then he. forced cement in between the tube and the wet ground about it, so that it set as hard as rock. All tunnels under water are built on the. same plan now. Sunlight'and Health. There is a striking analogy between the beneficial effects of sunlight and air upon plants, and upon human beings. One of the principal requisites for our physical welfare is haemoglobin', the coloring matter of the blood. Sun bathing and outdoor life are the best means of making it. Everyone " knows what happens to flowers that grow in the shade. Physiologists tell us that haemoglobin of the blood is to the human -body what chlorophyl is to the plant, and its growth is facilitated in the body by sunlight just as the growth of the green chlorophyl in the plant is facilitated. Miners who work underground become pale. Flowers that grow in dark places have.little color l and the leaves are pale. Human beings and animals are affected in much the same way for want of sunlight, excepting those that by nature are adapted to this life. The sunlight does more than tan the < surface of the skin. The coloring matter is formed and developed deeper in. ; The sun’s rays strike downyatid the effect penetrates perhaps for an inch or two into .the soft tissues, so that the influence of the sun is felt on the interior of the body as well as on the exterior.