RECOED AND DISCUSSION OF TEMPERATURES. 33 



Influence of Winds on Temperature. — To ascertain the temperature of the winds, 

 the following method was employed. By means of the preceding formula, express- 

 ing the temperature, a set of tables was formed — partly by direct computation, 

 partly by interpolation between these computed values — of the daily mean tem- 

 perature throughout the year, and the same was set down opposite the respective 

 hours of the day when the mean temperature is reached. Next, by means of the 

 known diurnal variation, interpolated from its mean monthly value, for each day, 

 these tables were completed by inserting the temperature for every hour of the day 

 to the nearest whole degree. They were then compared, hour for hour, with the 



abstract of observed temperature, and the difference < °^ ^^ ^^ \ placed in the 



( — for defect J 



column for the respective wind as observed at the same hour. For this latter pur- 

 pose, an hourly abstract of the wind was prepared. The abstract of differences 

 contains eight columns for each of the principal directions, and an additional one 

 for calms. By this process, the effect of the annual and diurnal variation is at 

 once eliminated, and the remaining differences can safely be left to their own com- 

 pensation. The results for the months from September to January (both inclu- 

 sive, have been combined for the two years. The following table exhibits the 

 results of this somewhat lengthy process. The first column contains the magnetic 

 directions of the wind, including a line for the calms; the second, the sum of the 

 differences as explained above ; the third, the number of times the wind blew from 

 each of the eight directions during the seventeen months of registered hourly tem- 

 peratures and winds; the sum total, or 2n, equals 11534, and the number by which 

 it falls short of 12264, indicates the number of hours observations were wanting; 

 the last figure in the column gives the number of hours during which the atmo- 

 sphere was calm. The fourth column shows the values of , or the quantity by 



n 



which each wind affected the temperature, the sign 4- corresponding to an effect of 

 raising the temperature above its mean. 



" Meteorology," Vol. XIV. 8th edition of the Encyclopsedia Britannica. The value 9 = corresponds 

 to January 1st and T \& expressed in degrees of Fahrenheit's scale. 



r=— 2°.20 +35°.39sin (« -f251° 43') +6°.T2 sm (2 9 +69° 4Y') +3°.20 stn (3 9 +11° 5')- 

 The formula leaves the following differences (0. — C.) between the observed and computed monthly 

 means : — 



In January — 0''.2 



February 4-3.4 



Marcli —4.9 



April -1-2.7 



May -1-0.3 



June — 2.5 



In July . 

 August 

 September 

 October 

 November 

 December . 



-f-l°.2 



-f-1.5 



—2.4 



4-1.4 



-fl.3 



—1.9 



And a probable error of any single determination of ± 1°.6. The warmest day is accordingly July 8th, 

 and the coldest March 1st. The mean temperature of the year is attained April 29th and October 12th. 

 The mean diurnal variation for the whole year, as derived from its montlily values, is represented by the 

 formula — 



t = -f-l°.85 sin (9 4-64° 55') 4-0°.08 sin (2 9 4-97°) 4-0°.03 sin (3 g 4-128°), 

 with a probable error for any single hour of ± 0°.03, the angle 9 counting from noon. 

 5 



