NO. 17.] 



FOG. 



537 



In summer and autumn, the range is nearly as great as that of the 

 probability of precipitation. 



PL IX. (1 mm. = 1 per cent). 1 



THE ANNUAL PERIOD OF THE PROBABILITY OF FOG. 



The maximum lies in July, and is as great as the maximum of the 

 probability of precipitation (0'192 in August). 



NUMBER OF DAYS WITH FOG. 



The winter months have no fog. The spring months very little. The 

 summer months have fog more than every alternate day, particularly July. 

 September has a good many, October few, and November extremely few days 

 with fog. PL IX. 3 (1 mm. = 1 day). 



1 On PI. IX has been written erroneously 1 mm. = 10 per cent. 

 8 On PL IX 1 cm. has been written instead of 1 mm. 

 3 Mark errors for June and July in the curve. 



