24 
MR. LEWIS F. RICHARDSON ON 
VIII. 1917, August, 2d. 17h. L.A.T., South England. Overcast. 
IX. 1917, July, 17d. 19h. 50m. L.A.T., East Champagne, France. Nine observations of a cloud at 
intervals of 1 minute by an Abney level. Angular elevation about 9 degrees. 
X. 1917, August, 8d. 20h. L.A.T., Argonne, France. Large fire of petrol and wood. Smoke observed 
from distance of 10 km. with a sextant. If smoke were not hot, height of its upper edge above 
ground would have given K = 4 - 6 x 10 s cm. 2 sec. -1 , an over estimate. Irregularities in upper 
edge gave K = 10 4 , probably an under estimate. Mean K of order of 10 5 . Overcast. 
XI 1918, April, 12d. 14h. 5m. L.A.T., France. Two anti-aircraft shell puffs at a mean elevation of 
21 degrees above the horizon and 4 degrees apart in a vertical plane, were brought into 
coincidence in the field of view of a sextant. In 120 seconds their separation of 4 degrees did 
not vary visibly, certainly not by 4 minutes of arc. Their apparent motion was horizontal at 
T'gVtr radian per sec. Height assumed 3200 metres—a likely value. 
XII. 1914, November, 16d. 3h. to 9h. G.M.T. Taken from the re-production of the Dines anemogram 
on p. 81 of the ‘Observer’s Handbook,’ Meteorological Office, London, 1917 edition. 
XIII. 1917, July, 26d. 21h. L.A.T., the English Channel. 
XIV. 1917, July, 26d. 16h. L.A.T., the English Channel, off Havre. 
XV. 1917, July, 26d. 15h. L.A.T., the English Channel, off Havre. Observations of cloud at intervals 
of 1 minute with pocket sextant. Angular elevation about 4 degrees. 
The photograph (2) also shows that the smoke spreads more rapidly upwards than 
downwards, indicating that the stress hh and the turbulivity £ both increase with 
height. 
Fig. 3 shows another case of low eddy-conductivity occurring at sunset. The 
smoke here is from burning hydrogen phosphides ; it is warm and rises slightly. To 
the eye the smoke appeared as a narrow wavy ribbon moving with a mean velocity of 
1'2 metres per second. The broader smooth band shown in the photograph is due to 
the exposure of 75 seconds, made long in order to get an average effect. The source 
of smoke is a bottle 3"4 metres above ground and just within the picture. The 
bamboos are 5 metres apart. The air density was 0'00126 c.g.s. The eddy- 
diffusivity works out to about 130 c.g.s. units, the eddy-conductivity to 0'16 c.g.s., 
the turbulivity to 200 c.g.s. The sky was cloudless. Obstructions to windward rose 
above the horizon to an angle of only 5 V radian. The photograph was taken in 
latitude 51° 37' N., longitude 4m. 24s. west, at 1919, Sept., 29d. 17h. 58m. G.M.T. 
Above is a table of observations. It is noticeable that when two of the 
direct stresses xx, yy, hh have been measured at the same time and place, they 
have been found to be not very unequal. G. I. Taylor has published some 
observations which show the same thing. It is as though there were a kind of 
equipartition of energy between the three components of the eddying motion. A 
very marked increase in both direct stress and diffusivity takes place either with 
velocity or with height. A rapid increase of viscosity with height in the first 
200 metres has also been deduced by W. Schmidt from wind observations made by 
Hellmann over a piece of flat land. (‘ Sitz. Akad. Wiss.,’ Wien, 1917, Heft 6, 
p. 17). 
