Variation of Temperature in the British TWrx, 



75 



and spring minimum, and a glance at figs. 1 and 2 will show that it is the 

 frequency which converts the sudden warm effect in February, which 

 is shown by the individual winds, into a gradual rise from autumn to 

 winter and fall from winter to spring which are the features of the 

 complete second-order curve. It will also be observed that the 

 frequency effect has a maximum in July which brings back the maxi- 

 mum exhibited by the sum of the individual effects to its normal 



DIAGRAM: 6. 



DIVERGENCE FROM FIRST ORDER CURVE. 

 KEW 1876 TO 1884. 



Fig.t Tot&L effect. 



2. Effect of compounding the 

 curves for &Lu winds, without 

 reg&rd to the reL&tive frequency 

 or the v&rious winds or Groups 

 of winds, 



5. Difference between fig.i. &nd Fig.z. 



position. The October November effect seems to be complete in the 

 compounded curve, and, as was seen in Diagram 4, it has its origin 

 chiefly in the curves of the south-east and north-west winds. Thus it 

 appears that the second-order effect is to some extent independent of 

 the direction of air supply, but that it is in part due to the relative 

 frequency at different times of the year with which the air supply is 

 derived from " hot," " cold," or " temperate " sources. At the periods of 

 the maxima of the second-order curve the air supply of these islands 

 is derived mainly from the warm sources, i.e., south, south-west, and 

 west, and at the periods of its minima, either from the coldest sources, 

 which are the east, north-east, and north, or to a very predominant 

 extent from the slightly cold sources, which are the south-east and 

 north-west. 



It is especially noteworthy that the cooling effect in May is due to 



