262 



GENERAL AIR CIRCULATION. 



In our next diagram, figure 82, an attempt has been made to show the probable pressure 

 at 3,000 metres. This height has been chosen instead of the 4,000 metres used by Memardus 



Fig. 82. Probable Antarctic pressure, 3,000 metres. 



for reasons which will be given in the next section. It is possible to outline the pressure 

 distribution at this height from the principles used in preparing figure 80. Isobars * are shown 

 and the method followed in drawing them will be their justification. 



We know from the pressure and temperature conditions over the Ross Sea and the 

 Barrier that the gradient between these two areas is reversed above about 1,700 metres, so 

 that at 3,000 metres the pressure over the Ross Sea is distinctly higher than over the 



* It may be as well to point out here that the actual pressure to which the isobars refer is not known 

 and therefore they have simply been numbered 1, 2, 3, etc. The number of isobars drawn has been determined 

 solely with the idea of giving a clear picture and they may be increased or decreased at pleasure, over either 

 the low or high pressure systems, if it is considered that the gradients in each are not in keeping _^with the wind 

 velooitioa. 



