On Diurnal Variation of Barometric Pressure. 27 



and «1 and a/ will each attain one maximum and minimum during 

 the course of a year. Moreover, the maximum of «j will cor- 

 respond to the minimum of a^. 



b) If l-^{p^+l)^^{p^ + l), hxxi I + -^-^ if +l)>-^{f+l), a, 



a a a a 



will have one maximum and a/ two maxima. 



c) If l-_^(^2+i)<:i(p2+l), and 1 + A(_pHl)<-^ (i^'+l) , a, 



a a a a 



as well as a/ will have two maxima. 



The position of zero will vary wàth the value of a, b,p. 



Again consider the case when a varies only in the direction 

 of meridian. Putting in § 7, (18) 



a=c + d cos- — y, (25) 



L 



we have a, oc c + d |l-(^ Y } cos -^ ?/ . (26) 



When we consider d an a periodic function of seasons, it will be 

 evident that the annual course will be inverted at the two stations 

 apart L/2 in the direction of y. 



In order that we may apply the above to actual examples, we 

 must of course have a detailed knowledge about the geographical 

 and seasonal distribution of the daily variation of temperature. 

 Since we are not yet in possession of the sufficient data, we will 

 merely mention here some facts with regard to the actual examples 

 to which our theory may find application, and suggest a method of 

 investigation convenient for the purpose. 



We wdll choose the data for British Isles, because the seasonal 

 variation of a^ is very irregular, apparently owdng to the rather 

 complicated distribution of land and water in this region. The 

 seasonal variation of a^ was taken from Angot's paper. Our first 

 procedure was to obtain the mean seasonal variation (Fig. 10) for 

 the ten stations, and then to obtain for each station the deviation 

 curve (Figs. 11-18). On comparing these deviation curves among 

 themselves, several interesting facts may be noticed: 



