30 THE METEOROLOGY OF JAMAICA 



spaces." The general appearance of this cloud is somewhat 

 similar to a Venetian blind, the dark and light bars being all 

 parallel to the horizon, wherever you look. 



(10) Nimbus simply means rain-cloud ; and as w^e have 

 already had cumulo-nimbus, this form should certainly be 

 called strato-nimbus. 



(11) Stratus. ''A horizontal sheet of lifted fog. When 

 this sheet is broken up into irregular shreds by the wind, or 

 by the summits of mountains, it may be distinguished by the 

 name oi fracto-sti^atus." 



Fogs lie during the night in the valleys in Jamaica, 

 especially in St. Thomas-in-the-Vale and in the interior parts 

 of Hanover, Westmoreland, and St. James, where those three 

 parishes join ; the morning sun dispels them about two hours 

 after sunrise, and if the morning be still and calm, a cloud 

 will be observed high above the valleys w^hich the fog had 

 previously filled. The above definition should be considered 

 to inchide ani/ loio horizontal sheet of smoke-like cloud condensed 

 out of lifted invisible vapour. In consequence, 



(12) Fracto-stratus is the commonest cloud in Jamaica, 

 winter and summer alike. In summer it develops into 

 cumulus ; in winter it develops into cumulus, stratus, or 

 strato-cumulus. 



Clouds (1) to (4) inclusive belong to the upper division ; 

 (5) to (7) inclusive belong to the middle division ; and of 

 course (8) to (12) inclusive to the lower division. 



In the Eegister their order should be reversed, so that the 

 column containing the lower cloud should follow the column 

 containing the surface wdnd ; then the middle cloud, and 

 then the upper. For there is a well-known law respecting 

 the relative direction of a succession of currents ; * and it is 

 convenient to see at a glance whether cyclonic (or anti- 

 cyclonic) conditions prevail among the currents ; for though 

 these conditions seldom occur, yet the importance of keejDing 

 careful watch for cyclones is so great that an observer should 

 regulate his system accordingly. 



* lu the northern hemisphere, if you stand with your back to the wind, the 

 higher currents will come more and more from the left (or diverge more and 

 more to the right), the higher the currents are. This law applies to both 

 cyclones and anticyclones. 



