OUR SEE-SAW ATMOSPHERE.

New Zealand Herald, Volume XLIV, Issue 13390, 19 January 1907, Page 1 (Supplement)

OUR SEE-SAW ATMOSPHERE.

I THE .MYSTERY OF WEATHER j '. ■ CHANGES. I ( j < A i am-isatisij article on the subject o)' •■Sum.. World's: Weather Problems" ap- I pears in the second number of Science Progress, tlie new and in every way admirable < quarterly journal of scientific thought of tin: twentieth century. The writer is William ; J. S. Lockyer, and he starts by quoting a j ■ very good general definition of the aerial ! 'envelope surrounding our earth. Here it i , is : ' '■ I "The earth we inhabit is surrounded by i j nil atmosphere of air, the height of which '. | is known to be at least forty-five miles, i jit presses upon the earth with a weight 1 equal, at the. level of the, sea. to about j i fifteen pounds to every square inch of stir-i ; face. As we ascend high mountains this; j weight becomes less: as we go down into!' deep mines it becomes sensibly greater. We I [ breathe this atmospheric air, and without ■ i ' it we could not live many moments. It floats round the eaith, being in perpetual j motion : and. according to the swiftness ! with which it moves, it, produces gentle ' breezes:, high winds, or terrible tornadoes."' It is astonishing how little is known, even j i to-day, about this immense ocean of air, and i of the movements which take place in it. We live at the bottom of the air ocean '■ jus; as flat fish live at the bottom of the j sea, and this fact may be one of the chief i reasons of our ignorance of its nature and ! motions. But wo are learning more of it j daily. The time has now fortunately at- j rived when soundings in the air can be made j nearly as easily a.s those in the ocean of j water. By means of balloons and kites wo can explore the' atmosphere, for about nine '' miles above the earth's surface, and what j we have learnt is' most useful and interesting. | Nowadays, instead of each nation or smaller group of people observing the weather of their own neighbourhoods and saying; nothing about it to others, there is an ad- j mirable spirit, of co-operation abroad, and the whole world's weather is being systematically observed. ; The ehutigeableness of the weather is a I truism which needs no emphasis here, but the causes of this condition arc worth study, ing constantly. "All these conditions arc produced by changes in the intensity or direction, or both, of the main currents in our atmos- ' phere. We know that these currents are dependent for the main part on the distribution of the atmosphere , , over the earth's surface, and we arc ! further familiar with the tact that this dis- : fribution is not homogeneous, for by means \ of our barometers we are able to weigh . . vertical columns of air, and these i weights are far from being equal. i "Observations of barometric pressure seem, therefore, to lie at the base of all I weather changes." i A scientist has discovered that there are i motions of a see-saw character in the at- J mosphere. One of these see-saws acts over j the area between Siberia and Australia. "In other words, when, in some years the pressure in Siberia was extra high, that in Australia was correspondingly low. "The present writer, with Sir Norman Lockyer, curried the investigation still further onward, and examined the pressure changes at ninety-five stations scattered all over the globe. The result of this inquiry led to too discover}* that there really existed only one large, see-saw, and this between nearly antipodal parts of the earth! In fact, it seemed that the Indian region was about, the centre of one area, while the Argentine and Chili formed the centre of the antipodal region." | What, asks the writer, does this - see-saw j ' inform us'.' In answering, it must bo re- . membered that there is a fixed quantity of ; ' atmosphere round our globe, and that if I some large quantity is drawn away to any I one quarter of the globe there will be a : shortage elsewhere. i " This barometric see-saw tells us that ' such a transference of air is really in operation, and the direction of this exchange is from east to west and from west to east ! alternately, and not between the equatorial ; and polar regions." j : And now is this barometric see-saw going j ito help meteorology? "Very materially," >. . says the writer. j "Wo have here, possibly, ail important. j clue to the close connection between the j ! meteorological behaviour of regions which : I tire, widely separated. For instance, it is j only quite recently that Sir John Elliot j ' pointed out that the drought in the Indian j region during the years 1895 to 1902 was a ; more or less general meteorological feature ,of the whole area, including Abyssinia, J '■ East and South Africa, Persia. Baluchistan, ; Afghanistan, and probably Tibet, and the : greater part or the whole of Australia. . . All these localities fall in the Eastern hemisphere portion of the see-saw, so that thev should Ik- affected .similarly." One 10-aiid-fro motion occupies nearly, but not quite, lour years on the average. "There is. 1 think now," the writer con'eludes, "little doubt that this pressure os- | (.'illation dominates, and is therefore'respon- ' sible tot, the very different types of wenit her that are experienced at any one place ! in the course of three or four years." i Tito writer seeks, in the article, for the i cause of this see-saw of our atmosphere. and lie finds i: in the sun. which, we are : incident ally told, becomes hotter and colder j ' alternately every eleven years. The fact of J the connection between solar activity and j the state of our atmosphere is by now well J : established in the minds of scientists. j