Direction of the Wind at Wallingford, Conn. 211 



numbers for the five years was taken. These numbers are given in 

 Table I. 



[See Table I, pages 212-225.] 



In order to deduce from these numbers the mean direction of the 

 wind, the sums of the hours during Avhich each wind prevailed were 

 I'egarded as distances traveled, and the numbers were resolved into 

 two rectangular components by means of a traverse table, in ihe same 

 manner as we resolve a traverse in navigation. The sum ol all the 

 southerly motions was then subtracted from the sum of all the north- 

 erly ; also the sum of all the easterly motions from the sum of all the 

 westerly ; and the resulting direction Avas obtained by the principles 

 of trigonometry. A similar computation was made for each of the 

 twenty-four hours for each month. The results are given in Table II. 

 [See Table II, page 226.] 



In order to exhibit the results of this Table jaalpably to the eye, the 

 numbers are repi-esented by curved lines on Plate viii. Beginning 

 with January, the wind's dii-ection at 1 a.m. was set off with a pro- 

 tractor, and a line drawn ^ inch in length ; from the extremity of this 

 line the wind's direction at 2 a. m. was set off, and another line drawn 

 of the same length as before ; and in the same manner were set off the 

 directions for each of the 24 hours. Thus we obtain a broken line 

 which may be regarded as representing the average progress of a par- 

 ticle of air for each hour of the day through the month of January, 

 supposing the wind's velocity to be the same at all hours. In like 

 manner the curve" for each of the 12 months were constructed. The 

 points of the compass are indicated upon the margin of the chart. 



These curves show a decided diurnal change in the direction of the 

 Avind for each month of the year; while for the six warmer months 

 the diurnal change is unexpectedly large. The following comparison 

 with similar observations made at Hudson, Ohio, Philadelphia, Penn., 

 and Toronto, Canada, will show the remarkable character of these 

 results. From a discussion of seven years' observations at Hudson, 

 Ohio,* Prof E. Loomis obtained for the mean direction of the wind 

 at 9 A. M. and 3 p. m. for each of the twelve months, the results given 

 in the first half of Table III. In the last half of the same Table are 

 given the corresponding results for Wallingford. 



* Am. Jour. Science, vol. xlix, 1845, p. 276. 



