518 



The cloud percentages refer to the entire day, hut the percentages of sunshine refer only to that portion 

 of the day during which the sun was above the horizon. Throughout November, December, and January 

 the sun did not set, and for these months the two values are comparable because they refer to similar 

 intervals of time. They do not differ very much in either of these months, but it will be noticed that the 

 sunshine percentage always exceeds that of clear sky, the explanation of the difference being found in the 

 fact that a record of sunshine was occasionally made when the sky was more than half covered with cloud. 



The differences between the values for the other months given in the table are explained partly by the 

 fact that they do not represent similar periods of time, and partly by the low altitude of the sun and the 

 consequent weakening of its power to burn the card on which the record was obtained. 



