556 



Transactions. — Physics. 



in a north and south line, and at a distance of about two hun- 

 dred miles apart. The progressive eastward movement of the 

 whole system is indicated by the compression of the lines on 

 its eastern or advancing side. Each circle represents T 2 oin. 

 of pressure, or from 30 to 304. The small arrows show wind- 

 rotation and the large feathered arrow the forward movement. 



Anticyclone (Southern Hemisphere). 



Mff/. 



It will be seen that at a pressure increases from 30 in. to 

 about 30-3 in., the wind changing from the southward toward 

 east, and that when the maximum pressure has passed to the 

 right of — i.e., to the eastward of — a, but also lies to the 

 southward of it, pressure decreases to 30 in., with the wind 

 changing to north-east; at b pressure increases to 304 in., 

 the wind continuing in the south, because the position of b is 

 such that it lies directly m the route of the anticyclone maxi- 

 mum pressure, and when this has passed to the eastward of 

 b the wind comes from north and pressure decreases to 30 in., 

 but at c pressure increases only about ^jin. or t0 30 - 2in., 

 with south-west wind changing toward west ; and as the 

 maximum pressure passes to the eastward of c, but lies also 

 to the northward of it, pressure decreases to 30 in., with wind 

 changing to the north-west. It will be seen by this figure 

 that, although the wind-rotation of the whole system is from 

 right to left, the changes in the direction of the wind as 

 experienced at a and c are in quite opposite directions. 



Nearlv all anticyclones have more than one maximum 

 area. This is shown by the occurrence of partial decreases of 

 pressure, accompanied by changes of wind to the northward, 

 and similar to that which has been shown to occur when a 

 high pressure passes away and is followed by partial increases, 

 accompanied by southerly wind, corresponding to those shown 

 as taking place on the first approach of high pressure. Dia- 

 gram No. 2 shows an anticyclonic pressure curve of the 

 Southern Hemisphere containing three maximum points : at 

 d pressure is at 30 in., with southerly winds, and increases to 

 e; then decreases with northerly winds to/, followed by a 

 second increase and southerlj winds to g : then decreases 

 with northerly winds to k, and increases with southerly winds 

 to nt. finally decreasing with northerly winds to 30 m. 



