Astronomical and Nautical Collections. } 305 
the other, the greater diminution of the spring than of the neap 
tides by the operation of a resistance proportional to the square of 
the velocity, which gives to the lunar tide a greater apparent pre- 
ponderance. Mr. Laplace is obliged to have recourse to some 
imaginary peculiarities in the local situation of the port of Brest, 
in order to explain the existence of lunar and solar tides in the 
proportion of three to one, while the other phenomena, depending 
on the moon’s attraction, make it improbable that the lunar force 
can be to the solar in a much greater ratio than that of five to two. 
But, in fact, the proportions of the tides in other ports, very dif- 
ferently situated, for instance at St. Helena, are nearly the same 
with those which have been observed at Brest; and it\is demon- 
strable, that such a diminution of the apparent. solar force must 
necessarily be the consequence of the operation of any resistance, 
proportional to the square of the velocity; besides being in part 
dependent, according to the most probable suppositions, upon the 
actual depth of the sea, as being more favourable to the exhibition 
of a lunar than a solar tide. 
“« There remains to be explained the interval which elapses be~ 
tween the time of new or full moon, and the occurrence of the 
highest tides, amounting at Brest to about a day and a half, and at 
London bridge probably to two days. The most simple supposi- 
tion respecting this interval, is that which Mr. Laplace has adopted ; 
as the retardation is greater at London bridge than at Brest, so it 
may be imagined that there are other places, still more exposed 
than Brest to the great oceans, at which it will altogether disap- 
pear. We cannot, however, discover any thing like a progressive 
succession of this kind in the tides which are observed at different 
parts of the continent ; nor would so great a time as a day and a 
half be required for the passage of a tide over more than half the 
circumference of the globe, upon any probable estimate of the depth 
of the sea.” The full development of the manner, in which the 
resistance may be supposed to cause this retardation, will be found 
in the Supplement of the Encyclopedia. 
“* We have assigned abundant reasons for the diversity which 
occurs in the time of high water at any given period of the moon’s 
