T40 



Report S.A.A. Advancement of Science. 



1 896- 1 904 at East London, and compared them with the simultaneous 

 temperatures at Durban and Kimberley. The following are mean 

 annual results for penthemera, of which the night of a cold wind is 

 the central night, together with the normal means. 



Table 6. — Mean Annual Minimum Temperature of Cold Spells at 

 East London, compared with the simultaneous Tempera- 

 tures at Durban and Kimberley. 



An examination of these numbers shews that the cold weather 

 is general throughout the. country, but that the true epoch of mini- 

 mum is earliest on the central table-land, and latest at Durban. In 

 fact, the lowest point of the curve of departure from the mean 

 temperature of the five days comes between the second and third day 

 at Kimberley, slightly later than the third day at East London, and 

 between the third and fourth days at Durban. This is a remark- 

 able result, considering that the barometric conditions upon which these 

 low temperatures depend travel from SW. to NE., and are therefore 

 felt earlier at East London than at Kimberley by many hours. If 

 the dependence of the temperatures upon the pressures were absolute 

 we should expect the temperature wave, like the pressure wave, to be 

 felt first at East London, and almost simultaneously, later on, at 

 Durban and Kimberley. It seems to follow, then, that the cold 

 winds in question, like the hot winds, must originate on the table- 

 land, and move downwards to the coast. An analysis of the baro- 

 metric pressures, which it is unnecessary to give here, supports this 

 view, anti-cyclonic conditions being the rule. For the purpose of 

 investigating the wind movement I have only had access to the 

 anemometer records of East London for the three years 1898-1900; 

 but of the 31 instances of low minimum temperature at East London 

 in those three years 29 occurred with winds blowing off the land, and 

 the other two with wind blowing parallel to the coast, one in 

 December strong from the SW., and the other in October strong from 

 a north-easterly direction. I am inclined to think that in both these 

 exceptional instances there must have been a strong admixture of 

 land wind entering from above. The average velocity of the wind 

 at the time of minimum on the third day in the 31 instances between 

 midnight and 8 a.m. was 19 miles per hour, i.e., about a mile an 

 hour faster than the normal. It is evident from these facts that the 

 cold winds of East London are true hora winds, similar in every 

 respect to those of Dalmatia. 



