422 Transactions of the South African Philosophical Society. 



have not Kew certificates ; nevertheless they compare very well one 

 with the other. 



The thermometers are placed under bare sand in an area of about 

 7 feet square surrounded by a grass lawn. In the beginning of 1901 

 they were moved from one spot to another more convenient which 

 they now occupy. 



TABLE 1. 



Monthly Aveeages of Temperature. 



Month. 



Black 

 Bulb 



in vacioo. 



Max. in 

 Shade. 



10 years. 10 yean 



Jan 152-0 



Feb 152-4 



Mar 143-9 



April 135-7 



May 125-4 



June 118-7 



July 119-6 



Aug 127-3 



Sept i 136-3 



Oct j 141-9 



Nov. , I 149-5 



Dec I 153-1 



Year 



88-6 

 83-2 

 77-8 

 70-9 

 64-9 

 66-3 

 71-2 

 77-9 

 81-7 

 86-4 

 89-5 



138-0 



78-9 



Min. in 

 Shade. 



10 years 



61-5 

 61-2 

 57-2 

 50-4 

 41-9 

 35-7 

 35-6 

 38-7 

 45-5 

 50-8 

 54-9 

 60-5 



49-5 



Min. 



over 

 Grass. 



10 years. 



o 

 57- 

 57- 

 53- 

 46- 

 37- 

 31- 

 30-6 

 34-0 

 41-0 

 46-3 

 50-3 

 56-4 



45-1 



Surface Soil. 



Max 

 years. 



121-3 



113-4 



105-0 



96-4 



86-5 



75-6 



81-2 



93-5 



102-1 



111-7 



120-5 



124-9 



102-7 



Min. 



6 years. 



63- 



63- 



58- 



51- 



41- 



34-2 



33-0 



35-5 



43-2 



50-9 



56-1 



61-6 



49-3 



M + m. 



2 

 6 years. 



76-0 



Table 1 gives the monthly averages of the maximum and minimum 

 temperature of the earth at a depth of 1 inch, the maximum tempera- 

 ture in the sun, the maximum and minimum in the shade, and the 

 minimum radiation temperature as registered by a spirit thermometer 

 standing 3 inches above short grass. With regard to this last it is 

 to be borne in mind that the grass is thick, and is green only for 

 eight or nine months of the year ; when frosts are prevalent the 

 grass is quite brown and dry. I have called attention before to 

 the fact that the maximum temperatures in sun and shade at 

 Kimberley depend upon the meridian altitude of the sun, and that 

 the monthly averages of both are, in consequence, greatest in 

 December and least in June. From Table 1 we see that a similar 

 (though accentuated) feature characterises the maximum temperature 

 of the surface soil. But, like the minimum temperatures of the air 

 and of radiation, the temperature of the surface of the ground is highest 

 at night towards the end of January, and lowest in July. The bare 

 ground is always warmer than the air during the day, but at night 

 it is warmer in summer and colder in winter. The range of tempera- 



