96 
Proceedings of the Royal Society of Edinburgh. [Sess. 
to-north current which must get rid of air, and a north-to-south current 
which must have air in order to maintain itself, and all that is required in 
order to maintain both currents is a transverse flow of *0175 C ? S ^ L IV at 
sm \ 
any level where the current velocity is V from the south-to-north current 
to the north-to-south current. We cannot accept this transverse motion as 
a part of steady motion, because the motion would not be strictly speaking 
along the isobars as prescribed by Law 1. But if we could persistently 
take the momentum necessary for the perturbation of the steady motion in 
compliance with Law 1 out of the general west-to-east circulation, we 
High 
10 
9 
South- 
> 
North - 
8 
to- 
•0175 
to- 
7 
North 
sm a 
South 
6 
current 
1 
current 
5 
4 
V 
•0175^^zr 
Sill A 
3 
‘ ‘ Too warm ” 
> 
‘ ‘ Too warm ” 
2 
I 
1 
1 
1 
<$- - - 1° long. > long. - -> 
Fig. 3. — South-to-North current V 1 supplying its own bottom outflow 
Uj and maintaining a parallel North-to-South current V 2 and its 
bottom outflow U 2 by transference of air across the ‘ ‘ high ” ridge. 
could have both the southerly and northerly currents maintained. It is 
not unreasonable to suppose that, as a westerly circulation has to be 
diverted northward to produce the northward circulation, the westerly 
momentum at the various levels may produce the effect described. In 
this case we should have the permanence of the anticyclonic distribution 
maintained by the persistent infraction of the law of relation of pressure 
to wind. At the same time a flow-off at the bottom outwards in both 
cases has to be supplied, and in consequence there is a downward flow 
under permanent conditions of pressure over both sides of the ridge of 
“ high ” which would give the necessary warming of the air of a high- 
pressure region. Hence the case represented in fig. 3 seems to furnish a 
possible example of a high-pressure region maintained in a quasi-steady 
condition by a transfer of air across the isobars in consequence of the 
