SOME MEASUREMENTS OF ATMOSPHERIC TURBULENCE. 
25 
The six observations of steamers’ smoke are put forward only as upper limits to the 
turbulence appropriate to the bare sea, for the steamer itself probably makes 
a considerable eddy. 
It would be desirable to classify the observed eddy-conductivity as a function of 
four independent variables; namely, the height, the vertical gradient of entropy, the 
vertical gradient of velocity and the character of the surface. Vertical gradient of 
velocity is suggested as an independent because it measures the only rate-of-mean 
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strain which attains a noticeable value in the free atmosphere, and because Osborne 
Reynolds* has shown that the energy of the eddy motion comes from the work 
done by the ecldy-stresses upon the corresponding rates of mean strain. The observa¬ 
tions here presented are much too scanty for such a classification, but to render the 
relation to height visible, the effect of velocity has been removed, in one sense, by 
dividing each value of the eddy-conductivity by the velocity at that level. The 
* Lamb, ‘ Hydrodynamics,’ IV. edition, § 369, equation (21). 
VOL. CCXXI.-A. E 
