516 



Throughout the eight summer months' observations at Discovery Bay there occurred fifty-two instances 

 in which the temperature recorded by the solar radiation thermometer amounted to or exceeded 120 F., and 

 in the two months of December and January, 1902-3, there were but four instances in which the reading 

 was below 100 F. 



At Madras the difference between the maximum temperature in the sun and the maximum air tempera- 

 ture recorded in the screen varied from 41 F. to 46 F., and the difference between the solar and terrestrial 

 radiation thermometers ranged from 75 F. to 82 F., but at Discovery Bay the difference between the 

 maximum temperature of the air and the maximum temperature by the solar thermometer ranged from 

 85 F. to 119 F. These figures certainly show that the solar radiation in the Antarctic during the summer 

 months is of unusual intensity, and indicate a condition of atmosphere peculiarly favourable for the 

 transmission of the sun's heat rays. 



AMOUNT OF CLOUD. 



The mean proportion of clouded sky bears a close relation to the subject of both solar and terrestrial 

 radiation, and must be taken into consideration when any attempt is made to estimate the total amount of 

 either. 



The mean cloud proportion for each month has been obtained from the daily observations, but from 

 internal evidence it would seem that separate estimates were made of each kind of cloud, instead of the 

 proportion of the sky expanse which was actually covered, and it is possible that this method of observing 

 would give results slightly too high ; in some instances, at any rate, it gives a total amount of clouded sky 

 greater than 10, which is the number used to indicate a completely overcast sky. 



The observations have been dealt with in two ways, and the results are shown in Tables IV. and V. 



TABLE IV. Mean Proportion of Clouded Sky at each Observing Hour of the Day, and for the Day. 

 (0 = cloudless sky; 10 = sky completely overcast.) 



