A STUDY OF ('()H1;KI>AT1()NS AMONG TERRESTRIAL TEMPERATURES. 



343 



illustrate the method as fully as possible, two combinations of the data have been 

 made. In the first the four Indian stations are treated as independent, in the second 

 their mean is used as a single region. The second and third columns show the general 

 mean departures of temperature, uncorrected for the sun spot fluctuations, as formed 

 from the departures in Table II. In the first of these the four Indian stations are 

 treated as if they were independent ; in the second their combined mean is used, as 

 found from the last column of Table V. 



AG is the sun-spot fluctuation. Subtracting it from the two columns of means 

 Ave have a world-departure of temperature, found in the columns t' and t, according 

 to the use of the Indian stations. Following each of these is its weight, which is the 

 sum of the weights of the individual departures. 



Fixing our attention on these world-departures we note that their general mean 

 value is about ± 0°.13, and that in only 7 of the 34 years does it rise to 0°.2. If we 

 could regard these departures as actual means for the entire globe, they would indi- 

 cate corresponding fluctuations in the sun's radiation. But, before we can draw any 

 conclusion to this effect, Ave must determine whether the departures exceed in their 

 general mean the values to be expected from the accidental deviations in the separate 

 regions. 



As the statistical method has been set forth, the sum of the squares of the general 

 deviations r are derived from any unbroken series of observations at a number n of 

 stations extending through a number r of years. In substance, the method consists in 

 subtracting from the sum of the squares of the products Wt the portions of the 

 squares which Avould be due to the accidental deviations, or twV. The remainder 

 STF't^ — X«'V, Avhich Ave have called A, is proportional to the sum of the squares of 

 the deviations for the whole globe, as shoAvn Ijy the equations (16) and (17). We 

 might subtract for each unbroken series, not the squares of the actual regional devia- 

 tions V, but the product of the mean values of v'- by r. The final result Avould 

 obviously be the same in either case. 



We now sum the columns- IF'V" and u<''v''' to find the value of A, dividing the time 

 into convenient terms of four or five years as follows : 



