552 Dr. W. N. Shaw. Relation between Autumnal [Feb. 2 r 



"On a Relation between Autumnal Rainfall and the Yield of 

 Wheat of the Following Year. Preliminary Note." By 

 W. N. SHAW, Sc.D., F.R.S., Secretary of the Meteorological 

 Council. Keceived February 2, Read February 2, 1905. 



By autumn, in this note, is to be understood the period from the 

 36th to the 48th week, both inclusive, of the year, as represented in the 

 Weekly Weather Report of the Meteorological Office; it covers the 

 months of September, October, and November, approximately. The 

 rainfall to be referred to is the average amount in inches, for the 

 " Principal Wheat Producing Districts," for the period mentioned, in 

 successive years. The amounts are taken from the summaries of the 

 Weekly Weather Report. 



The yield of wheat is that given for successive years in the annual 

 summaries of the Board of Agriculture and Fisheries as the average 

 yield in bushels per acre for England, since 1884, or more strictly 

 since 1885, as that is the first year for which the figures for England 

 are given separately. In 1884 the figure for Great Britain, which 

 generally differs but little from that for England, is used. 



These are the only figures in the official publications which are 

 immediately available for the purposes of comparison. The totals of 

 rainfall for the 1 3 weeks have been compiled from the weekly amounts,, 

 otherwise the figures are taken as they stand in published returns. 

 The areas referred to are not exactly coterminous, but they are more 

 nearly so than if the rainfall values had been taken for the whole of 

 England, or the wheat yield for Great Britain. 



When the autumn rainfall and the yields of wheat for successive 

 years from 1884 to 1904, as thus defined, are plotted, the rainfall curve 

 being inverted, i.e., rainfall being measured downward on the paper 

 while yield is measured upward, there is a very striking similarity 

 between the curves, so much so as to suggest that if the scales were 

 suitably chosen the two curves would superpose and show general 

 consonance, with exceptions, more or less striking, in a few of the years. 

 In other words, the yield of wheat in any year seems to depend mainly 

 on the absence of rainfall in the previous autumn, and but little on any 

 other factor. 



The obvious algebraical expression for such a condition as the curves 

 represent is a linear equation, and the equation which represents the 

 relation between yield of wheat for England and the previous autumn 

 rainfall is : 



Yield = 39*5 bushels per acre -5/4 (previous autumn rainfall in 

 inches). 



If we call the yield obtained from the rainfall by this equation the 



