Professor CErsted on Water-Spouts. 55 



30 feet ; but, in such cases, the lower part of the pillar has 

 been undoubtedly mistaken for the whole. This might easily 

 happen to a person who was not possessed of proper informa- 

 tion regarding the phenomenon ; for, when a water-spout be- 

 gins to be formed, especially over water, there is often seen 

 a pillar of water or of drops of water, rising from the surface^ 

 without a particular connection with a cloud being observa- 

 ble ; but this connection is to be found, if it is sought for, and 

 supposing we do not imagine that the cloud must necessarily 

 be perpendicularly above the water-spoiit. Should such a 

 water-spout in the act of formation be afterwards interrupted 

 in its development, its base might easily be mistaken for the 

 whole. It is apparent from all the circumstantial accounts 

 we possess of water-spouts, that their upper portion is a 

 cloud. 



The diameter of water-spouts is very various. The lower 

 portion has generally a diameter of some hundred sometimes 

 above a thousand feet, but often much less. The vor- 

 tex of drops or solid particles which the water-spout whirls 

 along with it, has, however, been sometimes included in the 

 mass forming the lower portion. But those cases are to be 

 regarded as exceptions, where the diameter of water-spouts 

 has been measured by the hollows they have formed in the 

 earth, which afford a much less considerable size. The dia- 

 meter of the middle portion is often estimated at only a few 

 feet, but this has chiefly been by inexperienced observers. It 

 will be made probable from what is to follow, that the middle 

 portion of the water-spout is surrounded by a whirlwind, 

 which does not allow of observation, OAving to its containing 

 no opaque particles. 



Colour and Transparency of Water- Spouts. — The colour most 

 frequently assigned to water-spouts is grey, dark blue, also 

 dark brown, and fire-red ; from which it would seem that the 

 colom-s are the same which the clouds assume in their diffe- 

 rent states of illumination. 



The middle portion of water-spouts is often transparent, 

 but this holds good only in those which occur over water. 

 One water-spout was noticed whose middle portion was 

 opaque while it traversed the land, but became transparent 



