48 



Causes of Water Spouts. 



Instead of attributing the formation of water spouts to this cause, 

 it would be more natural to suppose that electricity, when manifest- 

 ed in their appearance, is developed by the motion of the air which 

 occasions them. 



But how shall we form an idea of this movement ? How, from a 

 cause of that nature, give a reason for two effects which appear oppo- 

 sed to each other, that of descending and ascending spouts. May 

 we not, without confining ourselves to conjectures without proof, sub- 

 ject the phenomena to a certain extent, to experiment, and judge 

 from analogy, of the nature of the movement which takes place in 

 great whirlwinds, by that which we may observe in circular move- 

 ments in other fluids, of small dimensions. 



On the supposition that the motion of air alone in whirlwinds is 

 sufficient to produce water spouts, the same motion in liquids ought 

 to produce analogous effects, and if a whirling motion be excited in 

 a light liquid placed on a heavier one, the latter ought to ascend in 

 a spout into the former, as is the case in the natural phenomenon : 

 this reasoning led me to the following experiments. 



Fis. 1. 



Fig. 2. 



Fig. 3. 



First Experiment. — Into a cylindrical vessel ten inches high and 

 four in diameter I poured water to the depth of two inches and then 

 filled up the vessel with very transparent poppy oil. At the surface 

 of the oil I adjusted a little mill two inches high and an inch and a 

 half wide, the axis being vertical and the branches, four in number, 



