28 THE BOOK OF NATURE STUDY 



The number of rainy days in Great Britain is a point which 

 requires emphasis. It is a point which becomes commonplace 

 from so early a stage in the life of the individual that it is difficult 

 to make its significance realised. Our rainfall is moderate ; it 

 occurs throughout the year ; the number of days with rain is large 

 here are three facts of prime importance. Two important conse- 

 quences are : first, that long spells of drought are rare, and form no 

 part of the normal sequence of our weather ; second, that very 

 heavy falls of rain are also rare. 



As regards the second point, falls which exceed 2 inches in 

 twenty-four hours are regarded by the Rainfall Organisation as 

 sufficiently exceptional to need special emphasis. Much greater 

 falls than this do occur, the heaviest individual falls occurring as a 

 rule in districts where the rainfall is relatively great. The chance 

 that falls exceeding 2 inches in twenty-four hours will occur 

 varies so much with the locality that a general statement can 

 hardly be made. We may mention, merely for purposes of refer- 

 ence, that in the period between 1882 and 1905 the mean of the 

 daily rainfall records received by the British Rainfall Organisation 

 was 2314, and of these 285, or about 12 per cent., recorded falls 

 exceeding 2 inches in twenty-four hours. Further details will be 

 found in the yearly volume of the Organisation (British Rainfall). 



4. FLOODS. The first point then is to emphasise the relatively 

 gentle, diffused nature of our rainfall, using the ordinary observa- 

 tions for this purpose. But not infrequently, especially perhaps 

 in autumn, we have exceptional rainfall ; this, as indicated above, 

 being much more frequent in some places than others. Again, 

 if droughts do not regularly occur, almost every summer will afford 

 examples of a temporary limited dryness, which may be used to 

 illustrate the general phenomena of drought. Let the teacher then 

 first, by the help of actual measurements and records of rainy days, 

 emphasise the ordinary character of our rainfall, and then let him 

 seize exceptional conditions as a basis for lessons which may drive 

 home the ordinary conditions by emphasising the extraordinary. 



We may begin with a heavy rainfall. For example, in October 

 1906, very heavy rainfall was experienced in parts of Scotland, 

 especially on Speyside. At Ardclach (Glenferness) , in the county of 



