SCIENTIFIC AND USEFUL

New Zealand Graphic, Volume XII, Issue VI, 10 February 1894, Page 128

SCIENTIFIC AND USEFUL

THE ASTRONOMICAL DAY. The present method of commencing the astronomies! day is obviously inconvenient and contusing. Hence Canadian astronomers have invited all nations to c insider the question, ‘ is it desirable, all interests considered, that on and after January 1, 1901, the astronomical day should everywhere begin at mean midnight ?' DUST PHOTOGRAPHS. Two curious examples of ‘ dust or molecular photographs ’ hive been noticed in London. The plate glass of an hotel window has near it on the inside a glass screen bearing the words ‘ Coffee Room ’ in unfrosted letters. On removing the screen the words were found to be plainly visible on the window, and could not be removed by washing.]ln the other case a window bad been protected formerly by a gauze screen having the same words—• Coffee R >om ’ —in gilt letters, and on misty days these words have appeared on the glass since the final removal of the screen. ... OBJECTIONS TO THE ELECTRIC RAILWAY. Many of the objections urged against the introduction of the electric railway are strangely reminiscent of the extravagant objections raised against steam railways, as we are reminded by Mr Mayhew, in his recent work on railway development. Opponents of the steam railway assured the country gentry that birds would be killed by the smoke as they passed over the locomotive. The public were informed that the weight of the engine would prevent its moving. Foxes and pheasants were to become extinct in the neighbourhood of a railway, and the race of horses would soon die out altogether. Farmers were possessed with the idea that oats and hay would no more be marketable produce. Horses would start and throw their riders, and even cows would cease to yield their milk in the neighbourhood of one of those infernal machines. But as all these prophetic utterances have failed to fulfil themselves, the enemies of the electric railway will have to support themselves with some very strong forecasts indeed before the public mind will be seriously alarmed by them. A NEW HYGROMETER. A new registering hygrometer introduced by M. Debrun is composed ot a sheet of tanned gelatine, which, by the aid of a silk cord, acts on a lever bent at two very unequal branches. The extremity of the large branch traces on a sheet of smoked glass. A metallic registering thermometer traces on the same sheet, the simultaneous tracing of these two apparatus on the same sheet permitting the verification of the following facts:—When the weather is overcast or rainy the movements of the hygrometer are independent of those of the thermometer. When the weather is cloudy the movements of the hygrometer and thermometer are concordant or not as there is wind or none. In fine weather the course of the hygrometer and thermometer is always in opposite directions, so that with a thermometer and a hygrometer tracing on the same sheet it is possible to ascertain the state of the sky, etc , from the registration. ‘ TIIE LIFE OF THE EARTH.* An interesting speculative article on ‘ The Cessation of Life ’ recently appeared iu the Remie ScienUfique. The author, in the opinion of the Pall Mall Gazette, begins at the wrong end of his subject and works downwards, confronting the bewildered reader first with visions of the countless millions of centuries which must elapse before the universe, that * dust of the world,’ can finally come to an end and be used up. The life of the sun, which is the point at which our interest commences, has been estimated by careful thinkers. It will be twenty five to thirty millions of years before the sun’s autumnal period can set in, and be followed by the winter of death. The life of the earth is assigned within still finer limits. Science can even prognosticate the probable causes of its decay. Taking socalled natural causes first, all human and the higher organic life will die off long before the extinction of the sun’s fires. When the spots that now flick the equatorial zme of the sun have developed into patches sufficiently large to cause serious interference of light and heat, higher life will become impossible. There is, however, a cause at work within the earth itself which might anticipate this crisis. Gradually, but surely, the erosion of coast line by the sea, the flattening of mountains by torrent and glacier, are reducing dry land to the level of the ocean. When the levelling is complete ; earth will become but one vast swamp, unsuitable for human life. Four or five million years is the period given to the earth by geologists wherein to reach this stage. It is hardly worth while quibbling about a million or two of years now ; but the actual date as given above is likely to be deferred still longer by the gradual evaporation of the sea when its sources fail ; at which time, also, the dryness of the air, no longer refracting and storing up the solar heat, will leave the surface of our little glove, like Mr Kipling’s ‘ Tomlinson,’ at the mercy of the interstellar cold. Tbis effect, however, is neither so certain nor so easily calculable as the former one. It is supposed to be borne out in part by the example of Mars and the moon, the first of which appears to have no oceans left, but only inland seas ; while the other has absorbed its oceans, atmosphere, and all it ever bad. A doubt has been recently cast npon Mars in this connection. Professor Schaeberle, of Lick Observatory, is inclined to think that the * canals ’ of Mars are in reality dry land, the rest being ocean. In this case nothing but the mountain tops would be above water. The colour of San Francisco Bay from the top of Mount Hamilton is said to have originated first this revolutionary theory. But besides the natural causes of decay, M. d’Estienne, the above mentioned author, revels in what we must call by contrast the * unnatural.' He paints in glowing imagery what would happen, and in fact what at any time might happen, if the earth, in its journey with the solar system towards the constellation Hercules were to'encounter * des boll les des uranolithes !’