70 Professor CErsted on JFater-Spouts. 



meet, can produce such an effect ; but I do not venture to de- 

 cide if the accounts we possess are sufficient to prove the ac- 

 tual occurrence of such a consequence. 



In considering the water-spout, we have endeavoured to 

 arrive at its proximate causes from the effects which have 

 been observed and recorded ; and we have ascertained that 

 a whirlwind which begins in the higher regions of the air, 

 and becomes expanded as it descends, constitutes the essen- 

 tial element of the phenomenon. It will, however, be fur- 

 ther asked, What is the cause of this vortex ? We perceive 

 plainly that a whirlwind can be produced by two currents of 

 air following parallel courses, but flowing in opposite di- 

 rections. There is notliing to prevent us from assuming the 

 existence of such currents in the higher regions of the atmo- 

 sphere. They must often occur there while the air beneath 

 is perfectly tranquil ; at least, during an aerial voyage, a 

 whirling cloud was met with ; but M^e must also admit that 

 we are in possession of no evidence of such air-currents ac- 

 tually existing at the period when a whirlwind is formed. 

 But still, that this is the case seems very probable, when we 

 reflect that they must be of frequent occm'rence, and that they 

 are capable of producing the effect we have said might be as- 

 cribed to them. 



Experience teaches us, that such opposite streams in the 

 higher regions of the air often contend with each other, while 

 profound repose pervades the lower strata. We know also 

 that the opposite currents produced by the inequality of tem- 

 perature over the land and sea, often extend upwards to a 

 great height, and are there in a state of great commotion, 

 while all is tranquil beneath. 



It is evident that opposite and crossing currents of wind are 

 capable of producing also whirlwinds whose axes should run 

 parallel with the earth. These must hkewise produce great 

 mixtures of the upper and lower strata of air, and give rise to 

 rain and hail. This seems to correspond very well with om- 

 storms ; but I am not yet able to say how far we can carry 

 this opinion.* 



* From " Sehumadier'$ Jahrbuehfilr 1838." 



