PRECIPITATION 27 



results the fact that the rainfall of any particular part of Great 

 Britain is interesting in relation to the geographical position of 

 that area, and should be considered in that connection. 



It is unlikely that a teacher, however enthusiastic, will succeed 

 in getting a class to carry out rainfall observations over any con- 

 siderable period of time, so that the annual rainfall cannot be 

 studied on the basis of actual observation. On the other hand, the 

 observations can probably be kept up for a fortnight or even a 

 month at a time, and this will give an opportunity for explaining 

 the meaning of the term mean. The local result can also be com- 

 pared with the recorded averages for other stations, and thus an 

 idea of the great variations in the British area given, and correlated 

 with position, elevation, etc. Even if the actual observations 

 can only be kept up for a very short period, they should not be 

 neglected, for it is very important to associate directly a measured 

 amount of rain in the gauge with the observation of rain as it falls, 

 and, once this association has been firmly established, lessons based 

 upon official figures can be given without unreality. 



Another point of great importance as regards actual observa- 

 tion is the number of days with rain. For the meteorologist 

 a day with rain is one in which T ^- inch falls. An attempt 

 to record the days with rain should be made over a considerable 

 period, for from the climatic point of view this is of great import- 

 ance. The British climate as a whole is characterised by the great 

 number of days with rain, and therefore the relative infrequency 

 of torrential rain. Over the whole area the average is nearly 200 

 days with rain out of the 365 composing the year, but again the 

 different parts of the country differ considerably. The average 

 is about 180 for England and Wales, about 206 for the whole of 

 Scotland, and 216 for Ireland. The actual figures are only of 

 importance as enabling us to emphasise the great number of days 

 with rain in all parts of our area. As in the case of the total rain- 

 fall, the figures given above are made up by averaging a number 

 of different figures. The lowest number of days with rain on an 

 average in England seems to be 153 (at Weymouth), and the 

 highest 243, in Ireland (at Londonderry). The fact that the days 

 with rain are distributed throughout the year should be emphasised. 

 There is no season of the year when rain is not likely to occur. 



