SOME WORLD'S WEATHER PROBLEMS 209 



It may be mentioned here, however, that the remarks which 

 follow refer altogether to the prospects of defining the character 

 of weather during a season or a year, and not to such short 

 intervals of time as a day, a week, or a month. It is of far 

 greater consequence to know whether a summer will be fine 

 or wet, or a winter mild or cold, than to be informed that the 

 day after to-morrow will be wet. 



Every one is acquainted with the fact that not only in these 

 but in other lands the weather is not the same every year. 

 Sometimes there is a great abundance of rain, while at other 

 times we have very little. Some winters are impressed on our 

 memory by the abundance of snow, while for several years in 

 succession snow is conspicuous by its absence. Each country 

 is more or less visited at times with floods, droughts, famines, 

 or such-like misfortunes, and the names of India and Australia 

 are at once brought up in the mind. 



Now, without going into too great detail, it may be said 

 that all these conditions are produced by changes in the 

 intensity or direction, or both, of the main currents in our 

 atmosphere, and, as I have stated above, we are only acquainted, 

 like flat-fish, with the currents at the bottom of this atmosphere. 

 We know, however, that these currents are dependent for the 

 main part on the distribution of the atmosphere over the earth's 

 surface, and we are further familiar with the fact that this 

 distribution is not homogeneous, for by means of our baro- 

 meters we are able to weigh, in inches of mercury, vertical 

 columns of the air, and these weights are far from being equal. 



Observations of barometric pressure seem therefore to be at 

 the base of all w r eather changes, and the statements here made 

 will be for the main part restricted to this meteorological 

 element. The reader must, however, be reminded that it is 

 really temperature which dominates the atmospheric circula- 

 tion, but the changes of this important element are rendered 

 so complicated by local causes, that for simplicity all reference 

 to it will be omitted here. 



To describe now some of the steps which have led up 

 to this new aspect of meteorology, reference must first be 

 made to the work of H. F. Blanford, who, in 1879, was the 

 Meteorological Reporter to the Government of India. Blan- 

 ford, from a discussion of the variations of barometric pressure 

 over many years, found that there existed a kind of see-saw of 



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