92 Experimental Philosophy. [Lecture 7. 



least, botli seem to proceed from the same cause. 

 Wherever the air is suddenly rarefied in a par- 

 ticular spot, from electricity or any other cause,* 

 a kind of vacuum is created, and the circum- 

 ambient air rushing at once from every quarter, 

 a conflict of winds takes place, and the circular 

 motion, already noticed, ensues. It is to be ob- 

 served that, in water-spouts at sea, the water 

 ascends, and does not descend (according to the 

 vulgar notion) from the cloud, which is formed 

 at the extremity of the spout. The water in 

 this case rises, where the vacuum is created by 

 the whirlwind, by the pressure of the atmo- 

 sphere, as in a common pump. Only the vacuum 

 not being quite perfect, it rises in small drops, 

 and forms the cloud at the upper extremity of 

 the phenomenon. An artificial water-spout may 

 be made in a very easy way. In a stiff paper or 

 card make a hole just wide enough to insert a 

 goose quill, then cut the quill off square at both 

 ends ; place the card at the top of a wine glass or 

 tumbler filled with water to within about a quarter 

 of an inch of the lower orifice of the quill. Then 

 apply the mouth to the upper part of the quill, 

 and draw out the air. The water in the glass 

 will then be seen raised in the form of an in- 

 verted cone like a water-spout, and not in a con- 

 tinued stream, but broken into drops, and mingled 

 with particles of air. 



It is by the agency of the air that water is 

 raised in vapour from the earth to form clouds. 



