Professor OErsted on IFater- Spouts. 63 



appears in the clouds. It is not probable that the latter im- 

 mediately pass into a state of repose. According to what has 

 been already mentioned regarding the observations of Holm, 

 it is evident, that the clouds, after all appearances of a water- 

 spout have ceased, nevertheless retained a rotating movement. 

 It was at the same time remarked, that not only those clouds 

 which formed the upper portion of the water-spout, but also 

 the rest at some distance, possessed a cu'cular movement. 



On the actual nature of a Water-Spout. — If now, after all 

 this, we ask, what a water-spout really is ; the answer would 

 be : it is a whirlwind (Luftwirbel). By itself, a water-spout 

 is not more visible than air itself, but those portions which 

 are mixed either with vapour, di'ops of water, or solid matter, 

 become visible. 



The source of this vortex is not to be sought in the lower 

 regions. There is no peculiarity of the earth's crust with which 

 the phenomenon of water-spouts seems to be connected ; for, 

 they occm' in countries of the most diversified constitution, 

 as, for example, in volcanic, as well as in non-volcanic dis- 

 tricts. In the sea also, there seems to be no condition of the 

 water or of the bottom, on which their occm'rence is depen- 

 dent. Just as little can these vortices be produced by the 

 winds prevailing at the earth's surface, for they take place 

 most frequently in the midst of a serene atmosphere. They 

 must, therefore, have their origin in the upper regions. 



Owing to the circular motion of water-spouts, all the parts 

 exhibit a centrifugal action towards the circumference. This 

 force is, as is well known, a necessary consequence of the na- 

 ture of rototary motion But any one even who is not ac- 

 quainted with the laws of circular motion, can form a per- 

 fect idea of this matter, by taking a ti'ansparent vessel, as for 

 example a flask, filled with a mixture of sand and water, and 

 by some means or other tui'ning it round on a perpendicular 

 axis. The heavier portions will then be observed on the out- 

 side, and the lighter in the middle. Those portions which 

 are carried to the greatest distance from the middle, ai'e at 

 the same time carried upwards ; this takes place because the 

 agency which drives them outwards finds a limit at the cir- 

 cumference, which forces the particles that are in motion to 



