312 Rain Fallhuj at Rothamsted 



for the last 14 years the average for the year has been 29-98 inches, 

 and but for three abnormally dry years (1905-6, 1908-9, 1913-14) 

 would have been well over 30 inches. Rothamsted lies in the rather 

 narrow wet strip that runs in a north-easterly direction across the 

 eastern counties, and separates the dry region, including the Thames 

 Valley, South Middlesex, East Berkshire and East Oxfordshire on the 

 south, from another dry tract comprising Bedfordshire, Cambridgeshire, 

 Huntingdon, East Northamptonshire, etc., on the north. 



The distribution calls for little comment. The four wettest months 

 are July, August, October and November, and the four driest are 

 February^, March, April and June: allowing for the varying number of 

 days, April is the driest month of all; this is usual over one-half the 

 area of the British Isles^. Further details are given in Table 1, p. 331. 



The amoanl and distribution of nitroycn cotnpoiimla in the rain. 



The amounts of ammoniacal and nitric nitrogen present in the rain 

 are given in Table 2 (p. 332): in lbs. per acre they are 



Sept. Oct. Nov. Dec. Jan. Feb. 



Nitrogen as Ammonia 



(NHj) 0-217 02.35 0-219 0-223 0-182 0-159 



Nitrogen as Nitrate... 0-103 0-161 0-111 0-115 0-087 0-088 



The yearly fluctuations in ammoniacal nitrogen are shown in Fig. 1 : 

 they are seen to follow the rainfall very closely with only four exceptions : 

 the year 1893-4 when the ammonia fell although the rainfall rose, and 

 1895-6, 1901-2 and 1908-9, when the ammonia rose although there 

 was less rain. Fig. 2 shows the fluctuations month by month; these 

 also follow the rainfall. Tables 3 and 4 (pp. 333-4) give fuller details. 



' February is one of the driest months in the whole year so far as actual rainfall is 

 concerned, but there is a popular tradition which is still carried on by popular writers, and 

 which no amount of statistical data is able to break, that it is a wet month. Probably the 

 reason for the tradition is the old proverb "February fill dylse." 



2 H. R. Mill and C. Salter, J, Roy. Met. Soc, 1915, 41, 14. 



