and Departures in the United States. 



no 



ative region ; the positive maximum departure, not neces- 

 sarily the hio-hest station, is taken as 7 degrees, so that we 

 have 7x7 = 4-49 to represent the strength of the positive tem- 

 perature departures during the month, May, 1896, in the 

 United States ; the nmximum negative departui'e for the west- 

 ern districts is about 6 degrees, so that 3x(— 6)=— 18 rep- 

 resents the negative departure number for the same month ; 

 the sum of these without signs, 49 + 18 = 67, is the total aver- 

 age amplitude, that is the amount by which the temperature 

 system departed from the normal in a series of high and low 



•Fig. 1. 



Fig. 1. Temperature Departures, May, 1896. 

 481 similar charts have been drawn, giving the temperature variations in 

 the United States from January, 1873, to December, 1909. 



waves; the sum of these numhers with signs, -f 49 — 18 = -f 31, 

 gives the average temperature excess for the United States, 

 showing that this region averaged warmer than the normal for 

 the month. Similarly, the numbers in Table I represent the 

 relative changes in temperature for the United States month 

 by month for 37 years, 1873 to 1909, inclusive. It can be 

 seen by an inspection of Table I, that : 



(1) it is not possible aUvays to treat the United States as a 

 temperature unit in the midst of the world-departure (New- 

 comb), because there are many months when, as May 6, 1896, 

 this region is not all warmer, or all colder, than the normal. 

 There is a tendency for the temperature to oscillate about a 

 sort of nodal line on the eastern edge of the Rocky Mountain 

 Plateau ; it sometimes hkppens that the interior of the United 



