203 



Curiously enough the maxima and minima for the three- 

 years are identical in both eases, being 69'^ and 49°, the range 

 therefore being the same, viz., 20°. The maxima and minima 

 did not occur on the same date at the two places. The mean 

 maximum of each of the three years of Simon's Bay however is 

 68° and of Table Bay 65°, a difference in favour of Simon's 

 Bay of 3 degrees ; the mean minimum of Simon's Bay being 

 52° and of Table Bay 50°"6, a difference in favour of Simon's 

 Bay of r4 degrees. The annual range also is different, being, in 

 the case of Simon's Bay 20°, 17°, 17°, and in the case of Table 

 Bay 15°, 19°, 17°. 



With the exception therefore of the absolute maximum and 

 minimum, which are identical, there is a marked difference in 

 favour of Simon's Bay in the three years, taken both collectively 

 and individually. 



When, however, we come to consider the case more particularly 

 in regard to the monthly differences we find this is not so. Thus 

 the mean monthlv differences in favour of Simon's Bay are : — 

 January 6°-4, February 7°-3, March 4°-6, April 4°-3, May 2°-2, 

 June l°-6, July l°'4, August 0°-2, September -0°-8, October 0°*3, 

 November 1° 8, December 4°"2. During the winter months, 

 therefore, the mean monthly temperature of Table Bay 

 approaches that of Simon's Bay ; indeed, in each year it is higher 

 in August or September, or both — (September of 1898, August 

 and September of 1899 and x'^.ugust of 1900) — and for the three 

 years together it is higher in the month of September. ( Vide 

 Plate YI.) We learn from the data also that in summer the 

 temperature of the water in Simon's Bay is on an average 4 

 degrees higher than in Table Bay, while in winter it is only 1^ 

 degrees, a fact no doubt connected with the prevalence of the 

 south-east winds during the former period. 



Before leaving this series of observations we may note an 

 interesting comparison between the mean monthly temperatures 

 observed at Robben Island and those published by the Meteoro- 

 logical Council, London, in 1882. These latter are contained in a 

 series of charts with isothermal lines for the ocean district south of 

 South Africa. The data were procured from logs of English and 

 Dutch ships for the years 1853 to 1878. Plate VII shows the com- 

 parison between these. 



It must be remembered however that the latter are tempera- 

 tures taken at sea in the region off Table Bay. They do not 

 therefore indicate any general change of temperature of the sea 

 between the two periods of time, but they bring out markedly the 

 fact already noted, of the existence of water of higher temperature, 

 at a distance from land, and show that this ssems to hold good 

 generally. 



