The Winds. 



255 



discovered by Sir James C. Boss, about the longitude of Green- 

 wich, upon the confines of the Antarctic Sea. Another region 

 of great permanent depression, near the Sea of Ochotzk, is 

 known to exist at a diametrically opposite point upon the earth. 

 If these observations should be confirmed, there can be little 

 doubt that a cyclonic tendency of the wind round these regions 

 must exist as a permanent feature of atmospheric circulation. 

 May not these two regions of depression be the true Atmos- 

 pheric Poles of the world ; and may not the vortices which 

 they appear to indicate furnish an answer to the question, 

 " What becomes of the anti-trade currents of the air returned 

 to polar regions from the equator V 3 



The velocity and direction of wind may be registered either 

 in words or in a scale of figures, velocities, or pressures, as in 

 the following table : — 



Table VIII. — Wind-scales, or scales of the force of wind. 









Telocity. 



Pressure. 



General term. 



Land scale. 



Sea scale. 



Miles per 

 hour. 



lbs. on 

 one sq. ft. 



Calm .... 



















Light . 









1 



3 



10 



1 



2 



Moderate . 









2 



5 



32 



5 



Fresh . , 









3 



7 



45 



10 



Strong . 









4 



8 



65 



21 



Heavy . 









5 



10 



72 



26 



Violent . 









6 



12 



80 



32 



Instruments for recording the force and direction of wind 

 are called anemometers {ave/JLOs, wind; /xerpov, a measure). In 

 Robinson's anemometer the distance run over by the wind 

 is shown by four hollow cups attached to multiplying wheels, 

 whence the number of revolutions can be read off upon a dial. 

 A simple calculation then gives the velocity of the wind. The 

 pressure of the wind on a plate of one square foot is propor- 

 tional to the square of the velocity. It is recorded by means 

 of springs, in Osier's anemometer, upon a moving sheet of 

 paper, whilst a large vane records on the same sheet the direc- 

 tion of the wind. This instrument, by an ingenious contri- 

 vance, records automatically upon the same sheet of paper the 

 depth of rainfall for any time. It has been erected at Ply- 

 mouth, Greenwich, and Birmingham, as well as at Halifax and 

 the Bermudas on the Atlantic, to register the force and direc- 

 tion of the wind. 



