NO. 17.] 



CLOUD. 



517 



We see from these Tables that in every month the amount of cloud is 

 greater with the stronger winds, and less with the weaker winds. The 

 difference is greatest in the colder months, about 3'4 from January to April, 

 and least in September, which month has the greatest amount of cloud. 



The weaker winter winds and the fresher summer winds give no appre- 

 ciable diurnal period of the cloudiness. The general rule is that the 

 amount of cloud is greater during the day than during the night, and that the 

 diurnal range is greater with the stronger winds than with the weaker. 

 PI. VIII. (1 cm. = 1 degree of the cloud-scale). 



