56 Pi'ofessor Oersted on Water- Spouts. 



when it proceeded over a river. The transparency of this 

 portion at sea has sometimes been observed to so great an 

 extent, as to allow of those clouds being seen through it which 

 were lighted up by the sun. When an opaque water-spout 

 begins to become feeble, the cloud-like portions, which had 

 descended into it, retire, and as the drops of water, the foam, 

 the dust, &c. which caused the opacity, are no longer driven 

 upwards to so great a height, the middle portion becomes 

 transparent. 



Duration and Movements of Water-Spouts. — Water-spouts 

 generally last longer the larger they are ; but they rarely 

 continue for half an houi-, and there is hardly one example 

 of an hour's duration. 



Water-spouts seldom, if ever, remain the whole time at one 

 place. There is great inconstancy in their rapidity and di- 

 rection. They sometimes have so great a rapidity as to move 

 seven or eight German miles (thirty-two to thirty-seven Eng- 

 lish miles) in an hour ; at other times they advance so slowly, 

 that pedestrians can easily follow them, and occasionally they 

 remain quite stationary for a time. Their course is sometimes 

 quite straight for a long distance, but not unfrequently it is 

 interrupted ; in some instances it is zig-zag. Their course, 

 however, has for the most part a principal direction or bear- 

 ing. It has been asserted that the direction of water-spouts 

 is most frequently from south-west to north-east, and certainly 

 the data hitherto collected go to confirm this opinion. 



Water-spouts do not remain uniformly at the surface of the 

 earth, but alternately rise and fall ; and hence we see, that, 

 during their progress, they have in some places, torn up trees 

 by the roots, in others, only torn away the upper portions, 

 and that at some points they have not touched them at all. 

 This alternate rising and sinking often becomes very evident 

 when a water-spout traverses a plain or the sea. 



The circular rapidity of water-spouts is also very variable, 

 for frequently the eye can hardly follow it, while at other 

 times their motion is not so violent. Almost all observers 

 expressly mention this circular movement, and I do not find 

 that its existence is contradicted by any who have themselves 

 seen the phenomenon. It is true that two American natural- 



