18 



so that 



G. I. TAYLOE ON EDDY MOTION IN THE ATMOSPHERE. 



tan BH, = - - 4 



A 2 



Substituting for A 2 and A 4 their values in terms of a 



1 tan a / 



tan BH! = - - - = tan a- - 



1 + tan a 



(18) 



Since a is positive and less than ^ the smallest positive value of H t is given by 



(19) 



The height H 2 at which the wind velocity first becomes equal to the gradient 

 velocity is given by u 2 +v 2 = Q G 2 . This reduces to 



9 _ BH ., _ ( 1 + tan a) cos BH 2 ( 1 tan a) sin BH 2 / 2 v 



tan a 



Equation (20) can be solved so as to give tan a in terms of BH 2 , and when several 

 corresponding values of a and BH 2 have been obtained BH a can be obtained by 

 interpolation in terms of a. In Table III. are shown the values of BHi and BH 2 and 

 corresponding to values of a from to 45 degrees. 



TABLE III. 



It appears, therefore, that Hj/H., varies from 3 to 2'2. 



Mr. DOBSON gives 80 me tres = 2 .g 6 ag the observed value of H,/H 2 , and his values 

 300 metres 



of a all were about 20 degrees. It is probably a coincidence that the observed ratio, 2'66, 

 should be so very close to the calculated ratio 2'6, but the coincidence is at least 

 significant. 



