§ 7).). SrO.lAlS, IIUURICANES, AND TYPHOONS. 427 



But tliat is conjecture ; the presence of heat is a fact. In the 

 middle of the cyclone there is generally rain, or hail, or snow ; 

 and the amount of heat set free during the process of condensing 

 the vapor for this rain, or hail, or snow, is sufficient to raise from 

 the freezing to the boiling point more than five times the whole 

 amount of water that falls. This vast amount of heat is set free, 

 not at the surface of the sea, it is true, but in the cloud-region, 

 and where the upward tendency of the indraught is still farther 

 promoted. What sets the whirlwind a brewing is another ques- 

 tion ; but its elements being put in motion, there is a diminished 

 barometric pressure, first, on account of centrifugal tendency; next, 

 on account of the ascending column of air, which expands and 

 ascends — ascends and expands on account of such diminished 

 pressure — and next, though not least, on account of the heat 

 which is set free by the condensation of the vapor which forms 

 the clouds and makes the rain. This heat expands and pushes 

 aside the upper air still more. 



799. After much study, I find some difficulties about the cy- 

 objectionstothethe- clon© thcory that I can not overcome. They are 

 ^'"^'' of this sort : I can not conceive it possible to have 



a cyclone with a revolving and traveling disc 1000, 500, or even 

 100 miles in diameter, as the expounders of the theory have it. 

 Is it possible for a disc of such an attenuated fluid as common 

 air, having 1000 miles of diameter with its less than wafer-like 

 thickness in comparison, to go traveling over the earth's surface 

 and revolving about a centre with tornado violence ? With the 

 log-books of several vessels before me that are supposed to have 

 been in different parts of the same cyclone, I have a number 

 of times attempted to project its path, but I always failed to 

 bring out such a storm as the theory calls for. One or two ves- 

 sels may do it ; but is their testimony sufficient ? I think not. 

 Take as many as six or seven at sea, and their records never 

 prove the existence of such a storm as the theory calls for. I 

 make a distinction between the hauling of the wind in conse- 

 quence of diurnal rotation of the earth, and the rotation of the 

 wind in the cyclone in consequence of its centripetal force. For 

 the sake of illustrating my difficulties a little farther, let us sup- 

 pose a low barometer with a revolving storm to occur at A in the 

 southern hemisphere. Let the storm be traveling toward B. Let 



