A STUDY OF CORRELATIONS AMONG TERRESTRIAL TEMPERATURES. 355 



This equation will be coml)ined with those to be derived from the later material. When 

 taken alone it gives the result 



V=.023; T„=±0°.15C. 



§ 12. General Dismission -of ilonthly Defarhires from 1S72 to 1900. 



In pursuance of our general plan we take up the mean simultaneous departures 

 of the temperature in these regions for which I have found observations to be readily 

 available. The results are given in Table X following. In explaining them the object 

 is to facilitate the work of using the departures, rather than to set forth in detail how 

 they were formed. The construction of the table is as follows. The period under dis- 

 cussion, 1872-1900, is divided into periods during each of which the number of sta- 

 tions remain unchanged. This is convenient because our general formulae, as 

 developed in Chapter I, involve a separate summation for each of these periods. 



For the first period the entire United States is taken as a single region, because it 

 is possible that, in the course of a month, a departure of temperature would have time 

 to extend itself across the Rocky mountains from San Diego to Texas. The mean 

 departui'es found in the table are formed from the ten-day means given in the next 

 chapter. From and after 1874 the West Indian stations are combined with the United 

 States, so as to form one general mean for all of North America. The region South 

 America is practically identical with the Argentine Eepublic. The data for this region 

 are also given in the ten-day tables. 



It will be .seen that the Indian stations and Batavia are treated as if completely 

 independent. Whether this is the case cannot be determined in advance of the gen- 

 eral discussion. I'he Australian departures are determined fi-om an extended study 

 and combination of the results given in the publications of the Adelaide Observatory 

 by Sir Charles Todd. For the most part they are formed from the mean of these six 

 stations in which the departures were found to be least subject to fitful fluctuations 



The departures at the several stations are numbered i\, v.,, etc., in accordance with 

 the system followed in Chapter I. These index numbers are therefoi'e the values of 

 i in the equation of § 4-7. 



Partly as a check, and partly to facilitate the ulterior discussion, the algebraic 

 sum of the 12 departures for each year are found below the line for December. 



The column S" which terminates the column for each year is the sum of the 

 squares of all the departures for the year at each individual station. From them the 

 steadiness of the temperature may be inferred. 



The mean t, the general world departure so far as it can be inferred from the 

 stations, and its square form the last two columns. These enter into the formulae of 

 Chaj^ter I, and are summed at the bottom of the columns. 



