KNOWLEDGE & SCIENTIFIC NEWS. 



[Jan., 1905. 



Svin 



Our 

 SLiid "Weather." 



By William J. S. Lockver, M.A., Ph.D. 



" The moon and the weather 

 May change together ; 

 But change of the moon 

 Does not change the weather. 

 If we'd no moon at all, 

 And that may seem strange, 

 We still should have weather 

 That's subject to change." — Notes and Queries. 

 There are many of us who would like to know whether 

 our ne.\t summer will be sunny and warm or our next 

 winter dry and cold, so that we might prepare for the 

 delights that could be enjoyed by such weather conditions. 

 That day is not however with us yet, and its delay in 

 coming is owing to many reasons, the chief among which 

 being that civilized nations were not so widely scattered 

 over the earth as they are now, and that consequently 

 meteorological records extending over a long period of 

 time do not exist in sufficient number to allow of a 

 complete discussion being made. 



If we only had behind us one hundred years of good 

 meteorological observations made in the way that they 

 are to-day, and also an unbroken record of observations 

 of sun-spots and prominences, then we should be in a far 

 better position to tackle such meteorological problems as 

 are now lying before us unsolved. 



Unfortunately one cannot go much further back than 

 about fifty years when discussing the great majority of 

 meteorological observations, for in many cases they are 

 either very sparse and broken, or it is not known with what 

 degree of accuracy they were made. In the case of solar 

 phenomena the investigator is still more restricted ; for, 

 although the observations of sun-spots have been made in 

 a more or less crude manner for a great number of years, 

 it was not till about the year 1830 that a systematic 

 method of observation was adopted ; further, the solar 

 prominences, important indicators of the sun's activity, 

 were only first recorded systematically in the year 187/. 

 The reader will therefore understand that before all these 

 difTerent phenomena can be correlated to enable long- 

 period forecasts to be successfully made, a greater period 

 of time than the one at present available is absolutely 

 necessary. 



This is, however, no reason why attempts should not 

 now be made to find out whether these solar and terres- 

 trial changes are related to each other, and if possible to 

 point out how, from our present material, such a relation- 

 ship, if detected, can assist us in making at any rate 

 rough forecasts of approaching seasons. 



It is generally acknowledged that we are children of 

 the sun, and life on this earth is only possible in conse- 

 quence of his presence. Our sun is, so to speak, the 

 fuel on which we are all dependent, and it is, therefore, 

 quite natural to look to him as the instigator of our 

 " weather." Now, our orange-shaped globe is surrounded 

 by the atmosphere. The sun from without pours his 

 rays down on the earth's surface and heats it, whether it 

 I)e water or land ; this heated land or water warms the 

 atmosphere in contact with it. and this warmed air, 

 which is now lighter than it was before, rises from the 

 surface and is replaced by the cooler and heavier air 

 flowing in at the bottom. In this way a current of air, 

 a wind, is set up. The land or water most heated in this 

 manner is that which lies in those regions over which the 

 sun during a year passes overhead, and the reader will 



at once gather that this part of the world is that which 

 includes the equatorial regions. It is due to the heat- 

 ing of this region, coupled with the great cooling about 

 the terrestrial poles in consequence of the presence of ice 

 and snow, that the whole mechanism of the circulation 

 of the atmosphere is set in motion and maintained, and 

 " weather " is the ultimate result of this circulation. 

 Fortunately for us — but unfortunately for meteorologists 

 — the surface of the earth is not completely covered over 

 with water, but is studded here and there with great 

 stretches of land, so that an unequal heating of the atmo- 

 sphere round the equator takes place, and the directions 

 of the atmospheric currents the further the equator is 

 left behind, combined with the rotation of the earth, 

 become more complicated than they otherwise would be.' 

 To study the action of the sun on the earth to its 

 fullest extent it is therefore best to begin in the region 

 about the earth's equator where the solar action is 

 greatest ; and when this is completed, to trace this action, 

 which would probably be communicated by the air 

 currents, to the regions in higher latitudes. 



Fiif. i.-The Sun. u< 

 .showJnff the spots 

 muximum. 



about the time of sun.spot 



It is well known not only in these hut in all other 

 latitudes that the " weather " is not the same every year. 

 Sometimes there is a great abundance of rain, sometimes 

 very little; one winter is very mild while another is very 

 cold. In fact each continent has its own little meteoro- 

 logical worries such as floods, droughts, fatnines, &c. 

 Thus India has just recovered from tlie most severe 

 famine ever known, while Australia is labouring from a 

 similar visitation. There seems little doubt that all these 

 conditions are produced by changes in intensity or direc- 

 tion, or both, of the main currents in our atmospiiere, 

 and since these conditions depend for the main part on 

 the distribution of atmospheric pressure, it is this element 

 which should receive the closest attention. 



It has been stated above that the most likely cause of 

 these variations finds its origin in the sun, for, granting 

 a change in his heating powers, the strength of the 

 atmospheric currents, and consequently the atmospheric 

 pressure, would be accordingly altered. 



The question therefore arises, Does the heating power 

 of the sun vary ? This is difficult to answer directly, al- 

 though from certain observations of his surface, to which 



