36 



RESULTS OF METEOROLOGICAL OBSERVATIONS 



The resulting direction of the wind from 27 years of observation is 68° (W. of 



S.) or nearly W. S. W., with an average value of — = 0.234, since we were 



n 



obliged to assume all winds as of equal velocity. 



Apparent Secular Change in the Direction of the Wind. 

 The most notable feature in the above table is a tolerably regular fluctuation in 

 mean annual direction of the wind similar to that found from the observations at 

 Brunswick, Me. From about 1834, or perhaps an earlier period, the values of 4" 

 decrease until about 1847 ; after this date they begin to increase again. To bring 

 out this variation, somewhat freed from accidental irregularities, alternate means 

 were taken and the two results for each year were combined to a mean value, which 

 are given together with their differences from the mean direction (68°) in the 

 foUowing table : — 



Year. 



4, 



4, — mean. 



Year. 



4-, 



4, — mean. 



Year. 



4, 



•\-y — mean. 



1829 







... 



1838 



87° 



+19 



1847 



33° 



—35° 



30 



86° 



+ 18° 



39 



70 



+ 2 



48 



34 



—34 



31 



79 



+11 



40 



68 



+ 



49 



43 



—25 



32 

 33 



79 

 88 



+ 11 



+20 



41 



42 



76 

 68 



.+ 8 

 



50 



46 

 48 



—22 

 —20 



52 



34 



88 



+20 



43 



58 



—10 



53 



67 



— 1 



35 

 36 



81 

 82 



+13 

 +14 



44 

 45 



57 

 56 



—11 



—12 



54 



75 



+ 7 



58 



37 



89 



+21 



46 



45 



-" 



59 



. . _ 



" ' ~ 



The range of the variability in the mean direction of the wind as observed at 

 Marietta is 56°, which is but little inferior to the annual variability of the wind. 



The above variation of the mean direction of the wind, from year to year, 

 deserves special attention, and should be further investigated from other observa- 

 tions, since the resulting epochs at Brunswick and Marietta are quite discordant. 

 It must also produce a small efi"ect upon the mean annual temperatures, and thus 

 connects itself with the supposed secular change of the temperature. The column 

 headed " ij/i — mean" will serve for ready comparison of results at other stations. 



The numerical values of — , also appear to be subject to a variation; during the 



above period these values are decreasing. 



Relation of the Direction of the Wind to Tempierature. 

 To find the deviation of the temperature of each wind from the normal tempera- 

 ture, a table of mean temperatures for every day of the year was computed by 

 means of the formula ( T) given above ; to these means was applied, with its sign 

 reversed, the correction to the mean of 3 observations to the mean of 24 observa- 

 tions in a day, in order to make the tabular numbers directly comparable with the 

 observed daily means (uncorrected). As the deviation from the normal tempera- 

 ture is different in the summer and winter seasons, the year was divided into two 

 equal parts (with regard to temperature), taking the epochs of the mean annual 

 temperature or April 15th and October 15th as the limiting epochs. The observa- 

 tions also indicate that unless a certain wind has been bloiving for some time it 



