24 POrCLAR LKCTCRES AND 'ADDRESSES. 



the moon is crossing the meridian, and (supposing 

 for simplicity, the moon to be in the plane of the 

 earth's equator) there would be high water when 

 she is rising and setting. When the moon and 

 sun arc exactly in conjunction and opposition, the 

 longest and shortest axes of their tidal spheroids 

 would agree ; and the highest and lowest tides on 

 the average of the whole earth would be the high 

 water and lo\v water immediately before and after, 

 or after and before, the time of new and full moon. 

 This, be it remembered, is on the supposition of 

 no tidal resistance, but does not involve any 

 assumption whatever of regularity, whether as to 

 the boundary of the sea or as to uniformity of its 

 depth, 



IO. Now, it is well known thai, in this part 

 of the world, the "spring tides" are observed 

 to be late by from a day and a half to three 

 days after new moon and full moon. On the 

 \\r>t ( 'oa>l of Ireland the interval is about 

 thirty-six hours ; it amounts to about sixty hours 

 London l>ridi;r, and has intermediate values 

 at intermediate points of the British Channel. 



