CLIMATOLOGICAL AVERAGES VON BEZOLD 



427 



53° to 1 7 north latitude the numbers given by Batchelder are 

 almost invariably smaller than those by Spitaler but are larger 

 in the equatorial zone and in the southern hemisphere. 



Especially do we recognize the value of the method of presenta- 

 tion here developed when we apply it not only to annual averages 

 but to specific small periods of time. 



Thus, for instance, the curves given by Wiener 6 and which have 

 been copied in educational works 7 showing the distribution of 

 insolation on March 20, 



1. 25' 



I.O 08 Q6 Q4 02 O 02 0.4 0.6 OB 



034 



Q62 



0.3I 



QOC 



April 12, May 5, and June 

 2 1 , present a very different 

 picture after being redrawn 

 as shown in fig. 62. 



In this figure the scale of 

 ordinates is chosen, as done 

 by Hann, so that the sum 

 total of the solar radiation 

 received on the 20th March 

 by a point on the equator 

 [at the upper surface of the 

 atmosphere] or the so-called 

 "Thermal day " is taken as 

 the unit. 



If now we examine this 

 figure in which we have also 

 added below for compari- 

 son, the temperatures for 

 January and July as given 

 by Spitaler we see that the 

 remarkably large sum total 

 of insolation that comes to the polar regions during the summer 

 solstice takes up far less space in this diagram than in the older 

 method of presentation, in other words, that portion of the cir- 

 cumpolar region that receives such a relatively large insolation is 

 only a very small fraction of the surface of the earth. 



It is easily understood what a great advantage this method has 

 in that the total insolation coming to any zone on a given day, is 



FIG. 62. DISTRIBUTION OF INSOLATION. 



6 Zeit. d. Oesterr. Gesell. f. Met., XIV, plate 1, fig. 3, 1879. 



7 See, for example, Hann. Handbuch der KHmatologie; 2d edition; 

 Vol. I, p. 97. 



