52 Experimental Philosophy. [Lecture 5. 



Sometimes the syphon is concealed in the handle 

 of the cup (see fig. 23.) in such a manner, that 

 when a person raises it to his lips to drink out of 

 it, the fluid which it contains shall be carried 

 over the bend of the syphon, and it will then be 

 drawn off by the longer leg, so that the person shall 

 not only be disappointed of his draught, but will 

 have his clothes well splashed, to the great 

 amusement of the by-standers. 



In some parts of the world there are what are 

 called intermittent springs, or wells which seem 

 to ebb and flow like the tides. This we shall 

 perceive is usually caused by a natural syphon. 

 In fig. 24, A is a well of this nature, B is a ca- 

 vity or reservoir of water under ground, with 

 which it communicates, by means of the pipe or 

 syphon C. It is obvious, that unless the water 

 in the reservoir rises above the height of the 

 bend of the syphon C, the well cannot be filled ; 

 but if by considerable rains, or any other cause, 

 the reservoir should become full, then the syphon 

 will begin to act, and the water will run into the 

 well as long as there remains any in the reservoir. 

 It will then cease to receive any more, and the 

 drain from the well will empty it in its turn. At 

 Gravesend there is a pond of this kind, which 

 ebbs while the tide is coming into the adjacent 

 river, fills after the tide has risen to its height, 

 and all the time that it is ebbing in the river. At 

 Larntown, in Worcestershire, there is also a brook 

 which, in summer, has a stream sufficient to turn 



