Lindsay — Annual Rainfall and Temperature of TJ. S. 77 



he finds, apparently, indicates a period for both of about 

 thirty-five years. The interval, however, between max- 

 ima and minima varies from four to thirty years. The 

 maxima for temperature and rainfall sometimes fall to- 

 gether and sometimes a maximum of temperature coin- 

 cides with a minimum of rainfall. 



It may be considered then that the most that may be 

 said is that there are not yet enough data, or perhaps, 

 better, not enough work has been done on the vast 

 amount of data already accumulated, to show with any 

 certainty, or even probability, that any celestial phe- 

 nomena govern the variation of temperature and precipi- 

 tation from year to year. The remarkable thing is that 

 the yearly variation is so small, considering the great 

 storms and great variations of temperature extending 

 over short periods. This very uniformity is perhaps 

 more wonderful than the discovery of some celestial cause 

 for the variation. 



The mtegi'ated values for the entire country evidently 

 furnish a much more reliable basis for a study of climatic 

 conditions upon the earth than could ever be obtained 

 by observations at isolated stations. 



EXPLANATION OF PLATES. 



Plate VIIT. — "With the time interval 1891-1904 are plotted: (P) The 

 precipitation, in cubic miles per year, on the entire United States. 

 (T) The annual temperature of the United States. (S.S.) Wolff's 

 sunspot numbers. 



Issued, June 19, 1912. 



