THE CALMS. 67 



Among these we particularly notice high chains of mountains, 

 the unequal capacity of sea and land in absorbing and re- 

 taining heat, which gives rise to sea and land breezes ; the 

 increasing or diminishing power of the sun in different seasons 

 by which the equilibrium of the air is modified in many coun- 

 tries, the difference of radiation from a sandy desert or a forest, 

 electrical discharges from clouds, &c. &c. 



Although subject to many of these local disturbances, the 

 winds generally blow with an astonishing regularity in the 

 tropical zone ; while in our variable climate the polar and 

 equatorial stream are engaged in a perpetual strife, now bring- 

 ing us warmth and moisture from the south and west, now cold 

 and dryness from the north and east. 



Thus, in the Atlantic and Pacific Ocean we find the trade- 

 winds perpetually blowing from the east, the north-east trade- 

 wind between 9° and 27° N. lat., and the south-east trade-wind 

 between 3° N. lat and 25° S. lat. It was by their assistance that 

 Columbus was enabled to discover America, and that the wretched 

 barks of Magellan traversed the wide deserts of the Pacific from 

 end to end. 



Between these two regions of the trade-winds lies the dreaded 

 zone or girdle of the eqtiatorial calms (doldrums), where long 

 calms alternate with dreadful storms, and the sultry air weighs 

 heavily upon the spirits. 



" Down dropt the breeze, the sails dropt down, 

 'Twas sad as sad could be ; 

 And we did speak, only to break 

 The silence of the sea. 



" Day after day, day after day, 



We stuck, nor breath, nor motion, 

 As idle as a painted ship 

 Upon a painted ocean." 



On their polar limits, the trade-wind zones are again girdled 

 with calm belts, the horse latitudes, whose mean breadth is 

 from ten to twelve degrees. The boundaries of these alternating 

 regions of winds and calms are not invariably the same, on the 

 contrary, they are perpetually moving to the north or south, 

 according to the position of the sun. 



From 40° N. lat. to the pole, westerly winds begin to ba 



