WINDS. 



ns3 



will continue to be until they are better understood. I have desig- 

 nated a calm as the result of an equilibrium of temperature, whether 

 it be high or low. In the first case, it is more or less a rarefied and 

 moist atmosphere : in the second, dense and dry. 



All observations show that there are several areas of ocean where 

 calms exist almost constantly. There are others which are periodical, 

 and result from geographical position ; while some have a daily recur- 

 rence, though well defined in limits. The areas of calms comprised 

 within the Equatorial limit, and those on the outer borders of the 

 Trade Winds, have also their periods of vibrations, caused by the in- 

 fluence of the sun's heat. The periodical calms are those consequent 

 upon the change of the Monsoons, and the diurnal ones are the result of 

 the land and sea breezes. Those resulting from geographical position, 

 are the large areas of ocean where the heat has induced an almost 

 constant high and equable temperature, to which the flow of the cur- 

 rents of air is sluggish, resulting from the velocity of the ascending 

 current, and where large areas are reduced to a very low and equable 

 temperature by the ice which exists in the Polar regions. All calms 

 continue as long as the surrounding atmosphere remains undisturbed. 

 Many instances of these will be brought to mind by the daily experi- 

 ence of every individual. 



We thus perceive that calms are frequent both in high as well as 

 low latitudes, and play an important and essential part in the circula- 

 tion of the aerial currents. Were it not for calms, in order to secure 

 the changes of atmosphere to insure a circulation, the heat and cold 

 would be much greater, the changes more constant, whirlwinds and 

 disastrous conflicts more frequent, and the shocks to our senses un- 

 bearable, or the atmosphere would be brought to a stand-still under 

 one temperature, and we deprived of the blessings which a free circu- 

 lation gives in the constant recurring cool and refreshing breezes, so 

 essential to the health, welfare, and happiness of man. In the first 

 case, neither man nor nature would know repose ; in the second, there 

 would be nothing to prevent that stagnation which would engender 

 all kinds of disease, and both animal and vegetable life would suffer, — 

 and that order of things which "tempers the wind to the shorn lamb," 

 so beautiful, so simple, and so wisely ordained in the progressive move- 

 ments of the winds in their retrograde action, would be destroyed, by 

 which the temperature is made to increase and decrease gradually, its 

 accumulation prevented, and not suffered to become stagnant, by the 

 one great law under which it acts, — the denser and colder atmosphere 



