328 OUTLINES OF NATURAL PHILOSOPHY. 



At Brest, the tides of the syzygies rise to 19.317 

 feet ; and those of the quadratures to 9.151, not 

 quite the half of the former quantity. 



In the Pacific Ocean, the rise, in the first case, is 

 5 feet j in the second, 2 or 2.5. 



The greater the rise of high- water above the level of 

 a fixed point, the greater the depression of the 

 corresponding low- water relatively to the same 

 point. To estimate the height of the tide, it seems 

 best to take the excess of the mean of the two con- 

 secutive high-water marks, above the intermediate 

 low- water. This is the method of LA PLACE. 



330. The height of the tide is affected by the 

 vicinity of the Moon to the Earth, and increa- 

 ses, cceteris paribus, when the parallax and ap- 

 parent diameter of the Moon increase, but in a 

 higher ratio. 



The greatest variation of the Moon's semidiameter 

 above or below the mean is about ^th of the 

 whole r and the corresponding variation of the tide 

 at the syzygies is ^ tn f i ts mean quantity. Sys- 

 teme du Monde, p. 77. 



331. The rise of the tide is affected by the 

 declination of the luminaries ; it is greatest, 

 cceteris paribus, at the equinoxes, and least at 

 the solstices. 



When 



