OUTLINES OF NATURAL PHILOSOPHY. 



SECT. VIII. 



Of THE TIDES. 



327. THE alternate rise and fall of the surface 

 of the sea twice in the course of a lunar day, or 

 of 24 h 50 m 48 sec of mean solar time, is the phe- 

 nomenon known by the name of the Tides. 



The time from one high- water to the next, is, at a 

 mean, 12h 25m 24sec. The instant of low-water is 

 nearly, but not exactly, in the middle of this inter- 

 val ; the tide, in general, taking nine or ten mi- 

 nutes more in ebbing than in flowing. 



At the time of new and full Moon, the tide is the 

 highest, and the interval between the consecutive 

 tides is the least, viz. 12h 19m 28sec. At the qua- 

 dratures, or when the Sun and Moon are 90 dis- 

 tant, the tides are the least, and the interval be- 

 tween them is the greatest, viz. 12& 30m 7sec. 



f 

 328. The time of high- water is mostly regu- 



lated by the Moon, and in general, in the open 

 sea, is from two to three hours after that planet 



has 





