a17— 
indication of the wind force on the horizontal boundary of the at- 
mosphere , not of the wind force on a vertical wall. It is a boundary 
phenomenon, and there can be no meaning in sveaking of its variation 
with elevation above the surface. Wind force is easily observed, al- 
though there is the disadvantage that gradations finer than Beaufort 
units or half Beaufort units cannot be distinguished reliably. On 
the other hand wind speed varies with elevation above the surface, 
and for a given wind force the sneed at any level varies with the 
stability of the air. Furthermore wind speed cannot *e measured ac- 
curately on shipbonrd. Of course the air speed past an anenometer 
can be measured with sufficient accuracy, but even a good anemometer 
exposure on a stationary ship cannot be relied uvon to give the wind 
Speed at the same elevation free fron the ship's influence. For a 
ship under way the difficulties are multiplied, so that no matter how 
carefully corrections are applied the wind syveed derived from anes 
mometer readings is not as reliable as the wind force estimated by an 
able observer. Hence, both theoretically and practically, it is 
justified to employ wind force. 
To summarize the conduetion of heat from the sea surface, this 
is ecqual to the vertical transport of heat by turbulence at any low 
fjevel in the air, This turbulent transport at a chosen level is given 
as the intensity of mixing at that level times the temperature gradient 
at that level. The intensity of mixing depends on the wind forces 
The temperature gradient is provortional to the difference between the 
water temperature and the air temnerature at deck level. Hence the 
rate of conduction may be expressed as the product of the water-air 
temperature difference and of a factor depending on. wind force. This 
factor is tabulated in the next section. The rate of evaporation is 
found from a similar product as presented in the following section. 
The basie research on turbulence in the atmosphere is still in 
