SOUTH AFRICAN METEOROLOGY. 275 



3. The Southerly (S) Type. — High over south or south- 

 east or both. Prevaihng' winds should be easterly, but the pre- 

 sence of the warm sea current often induces westerly winds. 



4. The Central (C) Type. — Higli over the whole of the 

 sub-continent, but often lower over the centre, causing the 

 appearance of two highs and a slight V. Prevailing winds 

 should be westerly on coast but various (ver the interior. 



5. TJie All-Low (L) Type. — Low over the whole of South 

 Africa, no decided high anywhere. Prevailing winds must be 

 decided by the positions of the areas where pressure is least ; 

 if on the west coast, they should be easterly ; if on the south 

 coast, they should be south-west to easterly; and if in the east, 

 they should be southerly to westerly. 



6. The Pericyclonic (F) Type. — 'High over west and along 

 southern coast to north-east or east ; sometimes the west element 

 is missing or the south or south-east one. Prevailing winds 

 should be southerly through easterly to northerly. 



The definition of a high and a low is as follows : A Low 

 is an area of low pressure bounded by the 29.90 inches isobar; 

 an average High has readings of the barometer more than 29.90 

 inches, and less than 30.10 inches, and a true High is an area 

 of high pressure bounded ])y the 30.10 inches isobar. 



In the following diagrams giving rainfalls following various 

 pressure types, the districts are defined thus: W, west Cape; 

 SW, south-west Gape ; C, central Cape ; S, south Cape ; SE, 

 south-east Cape ; N, Natal ; FS, Free State ; WT, west Trans- 

 vaal ; CT, central Transvaal ; ET, east Transvaal. 



Diagrams indicating where Rain fell during the 24 



HOURS GOVERNED BY A PRESSURE TyPE. 



