DIRECTION AND VELOCITY OF THE WIND. 



213 



the bi-horary intervals o h.-2 h., 2 h.-4h._, 4 h.-6 h._, &cc., or 

 for the hours i h. 3 h. 5 h., &c. It is evident, therefore, that 

 the velocities in Table III. do not strictly correspond to 

 the hours and directions opposite to which they are placed ; 

 and although the errors which would arise from this cause 

 might not materially affect the ultimate results, I have 

 thought it desirable to reduce the velocities to the times 

 for which the directions are given. This I have done by 

 simply taking for each hour the mean of the velocities for 

 the two preceding and two following hours. The corrected 

 results are given in Table IV. 







Table IV. 









Mean 



Mean 





Mean 



Mean 





direction. 



bi-horary 





direction. 



bi -horary 



h. 



6 1 



velocity. 



h. 



i 



velocity. 



.. 



... 227 41 .. 



.... 1518 



12 .. 



... 221 43 . 



.... 11-79 



2 .. 



... 229 46 . 



.... 15-47 



14 .. 



.... 222 29 . 



.... 11-71 



4 •• 



.... 227 52 . 



.... 14-59 



16 .. 



.... 221 57 . 



.... 11-56 



6 .. 



226 . 



.... 12-95 



18 .. 



.... 224 10 . 



.... ii-6o 



8 .. 



.... 221 33 . 



.... 12-05 



20 .. 



.... 224 5 . 



.... 12-48 



10 .. 



. ... 220 27 . 



.... 11-88 



22 .. 



.... '.27 43 . 



.... 14-05 



On looking over the numbers in this Table it will be seen 

 that from about 9 h. to 19 h., or from 9 p.m. to 7 a.m., the 

 velocity of the wind is nearly constant; it afterwards 

 rapidly increases, attains a maximum a little before two 

 o'clock, and then returns rapidly to the night^s rate. The 

 variations in the direction of the wind also follow those of 

 the velocity pretty closely. The total movement of the 

 air between 9 p.m. and 7 a.m. is 58-52 miles in a mean 

 direction from S. 42° 8' W. ; and between 7 a.m. and 9 

 p.m. the total movement is 96-67 miles from S. 46° 36' W. 

 It appears, therefore, that at about 7 a.m. a force which 

 has been almost, if not quite, inoperative during the pre- 

 vious ten hours begins to act on the wind from a westerly 

 direction, and, gradually but rapidly increasing in inten- 

 sity, produces its maximum effect between i and 2 p.m. ; 

 it then gradually diminishes, and finally ceases to act about 



