Clark : Notes on the York Rainfall. 431 



especially from the long^ records of Rothesay, London, and 

 Exeter. 



Going back again to the Upping-ham records, from 1736 tO' 

 1798, we get a similar curve, even though the comparison is with 

 less certain sun spot records. Also, Prof. Schuster has shown 

 (Proceedings 'Royal Society,' A, No. 515, p. 143), that 'from 

 1750 to 1825 the eleven year period does not appreciably affect 

 the periodogram.' A tendency to ' lag,' indicated even at York, 

 is however more pronounced. This especially tends to assume 

 the form of a ' hump ' when single cycles are considered, about 

 the eighth or ninth year of the cycle. We may note a similar 

 hump in solar intensity curves, especially if these are ' weighted ' 

 for the solar areas most efficient at the time of the autumnal 

 equinox. 



Examination has been made, further, with reference to 

 Bruckner's suggested thirty-five year cycle. The period covers 

 two such, namely 1831 to 1865, and 1866 to 1900. For these 

 two the respective annual and monthly values were three- 

 bloxamed and combined year by year. Except March and 

 August, all thirteen curves obtained showed a larger range in 

 the earlier part. Ten of the maxima fall in the earlier part, and 

 six minima. There is a contrast again between August and the 

 two following months. On eliminating the eleven year cycle, 

 this contrast becomes yet more strongly marked. Treating the 

 sun spot values in the same way, the residue gave a curve of 

 solar activitv closelv associated with the corresponding curve 



for S_+ « - k. 



Taking in both cases the records from 1831 to 1900, and 

 combining the two cycles into one, the solar curve has a 



maximum at VI. and minimum at XXVI. — 9 — — A shows a 



maximum at V. and minimum at XXVI. In both the years 

 II. -XIX. form a period of activity ; XX. -I. of quiescence. 

 Relatively wet Augusts preponderated during the quiescent 

 times, Septembers and Octobers during the active period. 



The curves for the whole year, and those of nearly every 

 month, are more or less similarly divided. For the whole year 

 the mean rainfall in the thirty-six years of ' active ' solar 

 conditions is 26.09 inches, againt 23.25 in the thirty-four 

 ' quiescent ' years. 



The three months about the autumnal equinox have been 

 specially considered with regard to the York rainfall, but the 



1906 December i. 



