OBSERVATIONS AT SEVERAL PLACES ON THE BRITISH COASTS. 
229 
mean water by knowing the excess of springs above neaps : the excess being 10, the 
mean water would be 7 below the neap high water. But it appears that in general 
the mean water is lower than this: and the excess of springs being 10, the mean 
water is from 14 to 19 below neap high water at various points on the coast of Great 
Britain and France. 
In consequence of the law of the high waters, given alike by the theory and by the 
observations, the spring high waters are above the mean high water for a longer 
period than the neaps are below it. For it is evident that if DE and DF be each 
equal to DC, the heights are greater than the mean DC through the arc EAF, which 
is greater than a semicircle. And it is evident that the excess of AE above a qua- 
iEC 5 
drant will be an arc of which the sine is 12° nearly. Hence the two 
portions of the semicircle will be, in time, 3^ 24“ and 2^* 38“ ; and the tides will be 
above the mean during 6 ^ 48“ of lunar transit, and below the mean during 5^‘ 12“ ; 
and this is found to be very nearly the case at all the places examined ; thus con- 
firming the identity of the rule of different places one with another, and with the 
construction given above. 
