404 



HYDROGRAPHY. 



calms, various moanings, and loud roarings are heard from the front 

 of the storm, which has passed, and from its rear, which is to come. 



The last part of the storm, though not of so long duration as the 

 first, is generally considered more violent, and vessels are reported as 

 receiving more damage after the change of wind, which rushes in 

 from an opposite quarter to restore the equilibrium. 



The sudden change of wind from the opposite quarter which follows 

 the calm, is preceded by sharp flashes of lightning ; the tempera- 

 ture falls, the barometer rises, and fair weather ensues, with a pure 

 and wholesome atmosphere. The utmost devastation is apparent on 

 every side, and both animate and inanimate objects show the effect of 

 the action of the electric fluid. During the whole period, the storm 

 is accompanied by excessive and copious falls of rain ; that which falls 

 in the latter portion is very much reduced in temperature, and fre- 

 quently hail is precipitated. 



The effect of electricity is seen in the burnt appearance of vegeta- 

 tion, — and in some cases, the crews of vessels have found the effects 

 of it upon their persons, although they had not been aware of having 

 seen any. 



The first part of the storm, which precedes the calm, is of much 

 longer duration than the latter part. The rise of the barometer is 

 more rapid than its fall. The change of temperature is equally great. 

 Where these meteors have taken place, their approach, direction, and 

 end, exhibit the above characteristics. 



To explain these phenomena, it is requisite to have recourse to all 

 the facts that have been established, and the localities where these 

 hurricanes originate ; comparing them with each other, to show the 

 directions in which they move, and in what particulars they corre- 

 spond. From them we derive what we believe to be the true expla- 

 nation of the phenomena ; and where these causes do not exist or 

 prevail, there are no hurricanes, or even storms, to disturb the atmo- 

 sphere; we may then be justified in ascribing to them the hurricanes. 

 The great and predominating causes which we assign for these meteors, 

 are therefore the accumulation of heat and electricity. They are en- 

 gendered on the sea, where the temperature has attained its maximum. 

 From evaporation, the atmosphere has become surcharged with vapor, 

 and an accumulation of electricity has taken place. At these periods 

 of the year, the winds have in a measure ceased over these areas, or 

 become fickle and uncertain. There is no way in which these accu- 



