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Proceedings of the Royal Society of Edinburgh. [Sess. 
The first term of the right-hand side is usually negative, but in a region 
of reversed gradient becomes positive. The second term is nearly always 
positive as far as the west to east component is concerned, and on the 
north side of anticyclones would be large and positive above the level of 
the stratus clouds, as the air at that level is much warmer towards the 
centre of the anticyclone. It may therefore be expected that on the north 
side of anticyclones the wind velocity will increase more rapidly at levels 
where the temperature gradient is low than where it is high. 
When warmer air is spreading from the west, as often happens in the 
northern half of anticyclones, the temperature will rise most where the 
wind velocity is greatest. Thus reversed gradients already existing are 
intensified, and regions where the temperature gradient was originally 
relatively low may become regions of reversed gradient. This process is 
perhaps assisted by the action of convection * within those layers where 
the temperature gradient was originally relatively high ; since the wind 
velocity increases with height and warm air is arriving, the temperature 
gradient will tend to fall in these layers also ; but convection may maintain 
an adiabatic gradient, and thus retard the increase of temperature at the 
top of the layer, and so help to produce a reversed gradient above it. Con- 
vection within the adiabatic layers would also reduce the increase of wind 
velocity with height in those layers, and thus the increase within the 
regions of reversed gradient would become more marked than ever. 
Whether this explanation is true or not, the fact remains that temperature 
curves of the type shown on the right-hand side of the figure above are 
* Mechanical mixing due to turbulent motion. See Note at end. 
