TIDES. 61 



time slow, and therefore, in as far as tides are con- 

 cerned, the solstices must be seasons of tranquillity, 

 except where there are powerful local causes, and these 

 of course will be the more violent in their action, in 

 proportion as that of the general ones is diminished. 



As the equinoxes are approached, the parallels of the 

 two tides will approach each other with a velocity pro- 

 portionate to the change of declination ; and that will 

 both augment the tides, and produce a motion in the 

 ocean, and especially in the atmosphere, toward the 

 hemisphere which the luminaries are approaching ; and 

 the latter will be augmented by causes that are to be 

 noticed afterwards. 



But there is a further source of variation in the po- 

 sition of the moon's orbit, and also in the changing dis- 

 tance of the moon both from the earth and the sun ; 

 and there are slight variations produced by the earth's 

 not being a perfect globe, but flattened at the poles. 

 Observation has not, indeed, been hitherto able to con- 

 nect these minor variations with any seasonal results ; 

 and indeed the variations themselves would not be very 

 easily rendered intelligible in the language of ordinary 

 conversation. We shall, therefore, only remark, that 

 the moon, revolving round the earth, differs nothing in 

 principle from a single atom floating in the atmosphere 

 or on the ocean ; and therefore as its relative distances 

 from the sun and the earth vary, the moon will be 

 affected by what we may call tides in it ; and must 

 produce a higher tide in the ocean and the atmosphere 

 when it is nearer to the earth, than when it is farther 

 distant. 



The source of variation that is the most easily un- 

 G 



