147 
1916-17.] The Formation of Anticyclonic Stratus. 
(2) On the northern and eastern sides of anticyclones there is nearly 
always a layer of stratus, or of haze with cloud patches ; the height of this 
layer varies between 3000 and 6000 feet above the surface, but the level is 
usually the same over a very large area. 
(3) Stratus is common in winter on the southern sides of anticyclones. 
2. Descent of Air in Anticyclones. 
In shoulders of high pressure, and on the western sides of anticyclones, 
the level of a reversed temperature gradient is sometimes observed to 
descend somewhat. 
3. Some Causes of the Formation of Stratus in Anticyclones. 
(1) Stratus may be formed by the action of adiabatic compression on 
cloudy air, with the assistance of convection. 
(2) Stratus may be produced as the result of the increase of the 
westerly component of the wind velocity above the layer in which it is 
formed. This method of formation may be subdivided as follows : — 
(a) In westerly conditions with an increasing temperature, the increase 
is more pronounced where the wind velocity is high ; layers 
whose temperature gradient is low may thus be changed to 
layers of reversed gradient, while convection maintains an 
adiabatic gradient in other layers. 
(b) In cold easterly conditions the wind usually decreases above a 
certain level, and so may cause a reversed temperature gradient 
immediately above that level. 
(c) In northerly conditions cold surface air may flow under warmer 
air from a more westerty point. 
In general the increased westerly component is the result of horizontal 
temperature distribution, but in case ( c ) it may be partly due to the air 
required to reinforce a northerly current being supplied from the west. 
(3) Stratus near the surface may be caused by contact with a cold land 
or sea. 
Nov. 30, 1916. 
Note on Turbulent Motion. 
Since the above paper was written, some researches by Major G. I. 
Taylor on the subject of the conduction of heat by means of eddies have 
come to my notice.* Most of the clouds I have called “ stratus ” are 
* “Eddy Motion in the Atmosphere,” Phil. Trans., A series, vol. 215 (1915), pp. 1-26. 
See also Report on the Work carried out by the S.S. “Scotia,” 1913, London, 1914 (H.M. 
Stationery Office). 
