Science Siftings

New Zealand Tablet, 23 October 1913, Page 57

Science Siftings

By 'Volt.'

; v '" : - : '."'*-' SurgicaljOperations on Trees. '_ - ;';:. There is hardly a wood of any^size 1 which does not have several- of its trees mere shells of bark, the heart■ of the trunk having been eaten away by the spread of 'dry rot.,. Outwardly they appear to be perfectly sound, bub sooner or later a higher-wind than 'usual : will 'bring them crashing down, perhaps endangering human life, and .almost: certainly seriously damaging the sound trees by which they are surrounded. Now, however, a method -has been discovered of preventing the spread: of the dry rot -fungi,: and by it an affected tree may be i tendered once more sound and-healthy.: The procedure is almost exactly similar to that followed by dentists in the case of a decaying tooth. First the decayed wood is carefully removed, and the resulting cavity entirely cleared of all• foreign substances. The holes which have to be gouged out are bacteriologically cleansed by corro'sive sublimate, . and the walls of the cavity waterproofed to protect the wood. If necessary, the cavity is braced with steel ribs or truss rods./The hole is now ready for filling in, and it is plastered up with cement, care being taken that the filling is kept under the edge 'of the bark at every point, so as to allow the bark to heal over the cement. When this last stage has been accomplished the tree is as sound and healthy as ever, 'and shows'no sign of the treatment to which it has been subjected. ; .. v •--■-."- People ...to the Square Mile, ... .■■ -,-;' ; / The statistical abstract for 1900 to 1910-11 contains the latest available figures respecting the populations of Europe'. Apart from, the small areas of the Hanse Towns, whose figure is 3825, the densest population recorded is that of Saxony, which has 830 persons to the square mile. Similar figures for other countries -Belgium,'6s2; the Netherlands, 465; United Kingdom, 372; -Japan, 335; Italy, 313; Germany, 311; Austria, 246; Switzerland, 235; France, 191; Russia in Europe, 55; Norway, 19; Egypt proper, 939. Oversea .possessions of United Kingdom, 33 ; of Germany, 14; of the Netherlands, 48; of Japan, 118; of the United States, 31. The highest national birth rates in Europe, apparently, are; recorded in. the Balkan .peninsula and Russia—namely, per 1000: Russia, 46.8; Roumania, 43; Bulgaria, 40.3; Servia, 39; Hungary, 34.8. France has the least birth rate—namely, 10.7. Roumania's death rate was 25.7, while the healthiest three "countries are those of Scandinavian: Norway, 13.2; Denmark, 13.4; Sweden, 13.8. The largest towns outside the British Empire are, inhabitants: New York, 4,767,000; Paris, % 2,888,000; Tokyo, 2,186,000; Chicago, 2,185,000; Berlin, 2,071,000; Vienna, 2,031,000; St. Petersburg, 1,907,708 Philadelphia, 1,549,000. i;; . Striking Facts About the Soil. , - '?/'--' ;: ~ How far does the heat of the full summer's'/ sun penetrate into the ground? Probably "hot one person in ten will give, an answer that is even approximately correct. Their replies generally vary from one inch to ; many hundreds of feet. Actually the distance about--3 feet. Beyond this depth the temperature of the 4 soil . does not vary appreciably from hour to hour, let the midday be ever iso hot and the midnight ever so cold. At this depth the mean temperature.in the.summer is about 58 deg. Fair., and in the winter about 36 deg. Fahr. And the annual difference? That is to say, the depth at which there is' some difference between : the summer temperature and that of the winter? Well, at a depth of 60ft it is impossible to measure any change due to the changing seasons overhead. \f Go/down only 40ft and it is minute—barely me'asureable. But at 25ft .to 30ft it is quite: a .definite amount. The surface/heat takes a long while to penetrate downwards. In fact, curiously enougli, the change in temperature of the ground takes just over six months to ; reach ; the end » of its 25ft journey. - Thus we are faced with the phenomenon of midsummer upon ; the .surf - occurring 'at the same time as midwinter 25ft to 30ft down, and . vice-versa. I. ~„'„, --„.', ■ .'. ,; - , c -* -r , *-..- -*~