328 ARRAN. METEOROLOGY. 



In sailing up the Sound of Sleat, a dead calm was observed 

 to reach from Airdnamurchan point to Loch Hourn. Im- 

 mediately succeeding that, was found so smart a breeze 

 from the westward, that the vessels passing through it 

 were obliged to lower their topsails and reef their main- 

 sails. Further to the northward, the calm again recurred ; 

 the line of separation being so decided, that the vessel 

 in which I happened to sail ran through the breeze at the 

 rate of eight knots an hour, entering the calm with such 

 velocity as to bring all her sails suddenly aback. This 

 line of wind was about two miles in breadth, and lasted 

 for upwards of three hours ; being accompanied by a 

 parallel line of clouds, a circumstance generally attendant 

 on partial winds, while the atmosphere on both sides was 

 clear and blue. 



It does not always happen that these winds proceed in 

 a straight direction : on the contrary, they are frequently 

 curved ; the curvature taking place laterally, or parallel to 

 the horizon, or even assuming directions more compli- 

 cated. Such curvatures are sometimes indicated by the 

 appearance of the water, at others by the trim of the sails 

 in the vessels which are under -the influence of the winds. 

 On one occasion in Loch Hourn, three parallel lines of calm 

 were observed to alternate with the same number of zones 

 of rough water, extending across the whole loch, and 

 at right angles to the course of the breeze. To be satisfied 

 respecting the actual direction of the wind in these points, 

 I caused the boat to cross the whole, using the oars in the 

 parts becalmed. Thus it was found that we went before 

 the wind through all the breezy parts ; the middle of each 

 zone, of which the smallest was not more than 100 yards 

 in breadth, being attended with as much wind as the boat 

 could well carry, and the margins diminishing' gradually 

 till they subsided into a perfect calm. This appearance 

 lasted for an hour or more, beyond which I had no oppor- 

 tunity of watching it in a satisfactory manner. It can 

 only be accounted for by supposing the stream of air 



