Science Sittings

New Zealand Tablet, Volume XXXV, Issue 48, 28 November 1907, Page 35

Science Sittings

By «Volt f

' - ' - The Green of the Sea The green color of ocean water depends upon the number of 'medusae and other minute animal forms which inhabit it. The deep goreen northern seasi literally swarm with these minature crea'fcures. In some places, as_ many as 128 of them have been found in a single cubic inch of water. From soundings made in the districts where these creatures are found in such immense Jiiumbers, it is probable that the waters will average a mile in depth. Whethe* these forms occupy the whole d'eptlli is uncertain.. Provided, however, the depth to which >tftvey extend is jb'ut 250. fathoms, an immense num*ber of one species may occur within a space of one) square mile. The Crawfish's- Tail The tail of- a crawfish serves that animal as an oar. By a peculiar jerk of. the .tail, the -animal can retire from a dangerous object with almost incredible swiftness The tail is much more effective in moving :the animal backward than forward, a singular instance of adap,tatkm to its situation, for by means of its tail it can . withdraw into its hole with such swiftness, as in an instant- to place it out of danger." Lasting Qualities of Wood Some /interesting} experiments (have .been made to ascertain which wood lasts the longest. It was "found that birch and aspen decayed in three yeaxs, maple and tfed beech in five years, and elm and ash in seven years. Oak, Scottish fir, and Weymouth pine decayed- to^the depth of half an inch in seven years. In- situtations so free from moisture that they may be practically called dry, the durability o£ timber) is unlimited. The roof of '.Westminster Hall is more than four hundred and fifty - years old. A Spider's Web Rightly considered, a" spider's web is a most curious as well as a most beautiful thing. The majority of children suppose that the spider's web is pulled :out of his •mouth and that the little insect has a large reel of the stuff in his stomach, and that he could almost instantly? add feet, yards,- or rods to the roll. The facts are that (the spiders have* a regular spinning machine, a set of tiny tubes, at the far end of the body, and that the "threads are nothing more nor less than a white sticky fluid, whioh hardens as soon as it comes in contact with the air Formation, of Rayibows A. fine rain and a strong sun are necessary for the formation of white rainbows. The phenomenon is due to - 'the optical principle known as interference. If the drops of water ble every sirmall, the 'interference of title rays causes a complete overlapping of the color and the bow appears white. The various prismatic colors, instead of being* thrown out separately, as in the ordinary prism, are -thrown one on top of the other, and the light is cast by ithe sun on a sheet of rain. The result is still more noticeable where a fog; takes the place of the rain. An Electric Tree A German authority has reoently announced the discbtiery of a tree in the forests of Central India which haa most curious characteristics. The leaves of the trees are, of a highly sensitive nature, and so full of electricity that whoever touches one of them receives an electric shock. It has a very singular effect upon a magnetic needle, and will influence it at a distance of even, seventy feet. The electrical strength of the tree. varies according to the time of day, it being strongest at midday and weakest at midnight. In wet weather its powers disappear altogsether. Birds. ner^er approach the tree, nor have insects ever^been seen upon it. A Remarkable Cave Two gold prospectors recently discovered in the Santa*- Susanna Mountains, abjout fifty miles .from Los Angeles, California, the largest and most* remarkable cave in Western America. While looking for indications of gold,, they found an opening,, whidh they entened. The opening led to a great! cavern, consisting of many passages, some of them wide, but most of them narrow and lofty. The passagps lead into great halls, .some containing an acre,' studdfed with stalagmites and stalac■tites, in some oases so thickly tihafit is difficult to 'get through. The walls of one of these halls are covered with rude drawings of the chase, some almost obliterated, but 'others still clear.