78 Rainfall, Natural Drainar/c, S^-c. 



one person considers every day rainy on which any rain falls, 

 another requires that his rain-gauge shall register something, 

 however small, and a third, that there shall be a definite and 

 stated quantity. It is evidently quite impossible to compare 

 statements where there is so little agreement as to the terms 

 made use of. But in this again there is now a spirit of im- 

 provement, and after the lapse of a few years the agriculturist 

 will know better than he can do at present, both whether the 

 climate of England is really changing, and if so whether the change 

 is for good or evil. 



The mean rainfall for the whole of the British islands is so 

 different from the means for England, Scotland, and Ireland 

 taken separately, and the mean of all England is also so different 

 from the means of certain districts taken separately, that a 

 collection of observations made over a large district cannot safely 

 be tabulated together without great precaution being taken to 

 avoid error. It is, indeed, specially necessary to define natural 

 districts, with a knowledge of the proximate conditions, and with an 

 express view to this branch of meteorology. The districts assumed 

 at present are twenty-three in number : eleven in England, eight 

 in Scotland, and four in Ireland. So far even as England and 

 Scotland are concerned, these are certainly very imperfect, and 

 Ireland must undergo re-arrangement as soon as the state of the 

 observations will permit. These divisions, however, rather refer 

 to geographical position than to similar physical conditions. 

 The total number of stations at which observations are now 

 made is very large. 



It has often happened that a year of drought in many large 

 tracts of the United Kingdom has been a year of excessive rain- 

 fall in others, but for this there have generally been assignable 

 reasons. More usually the causes producing exceptional years 

 m^ust be looked for from a distance, and affect large districts of 

 Europe as well as the British islands. One general law of 

 rainfall, however, seems to obtain in every part of the land of the 

 north temperate zone, in which records have been carefully kept 

 for a considerable time ; and although England gives somewhat 

 extreme examples of the operation of this law, and may even seem 

 sometimes exceptional, the general tendency of the observations 

 proves the existence of a considerable amount of harmony and 

 inter-dependence. 



If, then, it be the case, as seems very probable, that a diminution 

 of rainfall is taking place in England, it is evident that the 

 cause for such a result may be local, and the result of human in- 

 fluence and the cultivation of the land. On the other hand the 

 cause may be cosmical ; it may affect all Europe, and be con- 

 nected with other changes of various kinds, such as the elevation 



