494 Intermitting Springs* [Book VI L 



gular rifing and failing of tides in the ocean. The 

 phenomenon has fince been very fatisfa&orily ex- 

 plained, and upon a very fim pie and obvious princi- 

 ple. It has been already (hewn, that when a fiphon is 

 inferted in a verTel containing water, if the air is drawn 

 out of the fiphon, or by any means the water is made 

 to flow over the bent of the tube, which lies above 

 the brim of the vefiel, the water will continue to flow 

 over the brim through the fiphon till the whole is ex- 

 haufted. 



To account, therefore, for the intermitting fpring, 

 we have only to fuppofe, that a cavity or receptacle is 

 formed in the bowels of the hill or mountain, where 

 the fpring is fituated, which gradually fills with water 

 like other refervoirs j by the interpofition of fome ftra- 

 tum of (lone or rockj the tube or cavity which conveys 

 the water from this receptacle to the fpring or mouth 

 where it ifTues, is bent in the form of a fiphon, the 

 bent of which is confiderably higher than the bottom 

 of the refervoir. Whenever, therefore, the refervoir 

 or receptacle is filled as high as the bent of the tube, 

 the water will rife in it to its level, and begin to flow 

 into the fpring, which will continue till the receptacle 

 is exhaufted. While this procefs is going on the wa- 

 ter in the fpring will rife ; and as foon as the recepta- 

 cle is exhaufted, the water, being drawn off by a 

 ftream or rivulet, will appear to fall in the well of the 

 fpring, and will continue to fall till the receptacle is 

 again fupplied to the height of the fiphon or tube, 

 when the'procefs of filling will be again renewed. 



To render the matter perfectly plain, let ABC 

 (Plate X. fig. ,4.) reprefent the cavity or receptacle, 

 from the bottom of which C proceeds the tube or 

 fiphon D E. When the water rifes in the receptacle 

 to the level of E in the tube, it will begin to flow into 



the 



