OCEAN METEOROLOGY. 



185 



The above sail and speed, corresi^onding to various forces of the 

 wind, are but approximations to what really takes place according to 

 particular circumstances, such as model of ship, course steered with 

 reference to the wind, condition of the sea, etc. 



The customary designations of the clouds are employed, and the 

 portion of clear sky is denoted by figures — 10 representing a wholly 

 clear sky, an entirely cloudy one, and intermediate numbers a sky 

 partly clear and partly cloudy. 



In the column descriptive of the weather, the following sym- 

 bols are used, and by means of them, all the possible variations of 



