GENEEAL OBSEEVATIONS ON THE WINDS. 107 



and not on the coast. Professor Laughton accounts for the Sea Breeze 

 by the excess of barometric pressure seaward owing to evaporation, and 

 for the Land Breeze by the descent of the column of air forced up by the 

 Sea Breeze. It is to be remarked that both Land and Sea Breezes are 

 only well developed on coasts backed by hills. 



(19.) The wind decidedly veers round the compass according to the sun's 

 motion, i.e., in the Northern Hemisphere from North through N.E., East, 

 S.E., to South, and so on, often making a complete circuit in that direc- 

 tion, or more than one in succession (perhaps occupying many days in so 

 doing), but it rarely hacks, and very rarely, or never, makes a complete 

 circuit in the contrary direction, except in very high latitudes. Professor 

 Dov6 argued this to be the direct consequence of the rotation of the earth ; 

 and, although the observation was recorded by Lord Bacon, in 1600, it is 

 now known as Doves Law of Gyration* 



(20.) Professor Coffin, from his elaborate discussions, considered the 

 following to be a general description of the "Wind system of the Northern 

 Hemisphere : — 



1st. That from high Northern latitudes the winds proceed in a Southerly 

 direction, but veer towards the West as they approach a limit ranging 

 from about lat. 56° on the Western continent, to about lat. 68° on the 

 Eastern, where they become irregular and disappear. The area of this 

 zone is about 11,800,000 square miles. 



2nd. That farther South there is a belt of Westerly winds, less than 

 2,000 miles in breadth, entirely encircling the earth ; the Westerly direc- 

 tion being clearly defined in the middle of the belt, but gradually disappear- 

 ing as the limits are approached on either side. The area of this zone is 

 estimated to be about 25,870,000 square miles. 



3rd. That South of the zone last named the mean direction of the wind 

 is Easterly. This area is estimated to contain 60,760,000 square miles.f 



Professor Dove contended that there are but two systems, the 1st and 

 3rd of the foregoing, j 



* When speaking of the wind veering with the sun, of coiirse the shifting of the 

 cyclonic winds in the Northern Hemisphere is not inckided. 



t " Windsof the Northern Hemisphere," by Professor Coffin, A.M., Pennsylvania, U.S., 

 in " Smithsonian Contributions to Knowledge," vol. vi. 



X See Report of the British Association, 1845. See, also, Professor Mitchell, in the 

 American Journal of Science and Arts, vol. xix., page 254. A great amount of information 

 will be found on the general subject in the works of Kiimtz and Romme, who have also 

 laboriously studied and generalized the phenomena of the Winds, and to whose labours 

 much that is here said ie owing. 



