312 Astronomical and Nautical Collections. 
canal to the equator, and disappearing for a sea situated at the pole: the 
econd part is a diurnal tide proportional to the sine of the latitude or of the 
inclination, being greatest when the luminary is furthest from the equinox, and 
vanishing when its declination vanishes.” 
He next proceeds “ to inquire more particularly into the cause of the 
hitherto unintelligible fact, that the maximum of the spring tides in the most 
exposed situations, is at least half'a day, if not a whole day, later than the 
maximum of the moving forces. 
“ Now it is easy to perceive that, since the resistance observing the Junar 
period is more considerable than that which affects the solar tide, the lunar 
tide will be more retarded or accelerated than the solar; retarded when the 
oscillation is direct, or when G? — B is [negative,] and accelerated when it is 
inverted, or when that quantity is [positive] ; and that, in order to obtain the 
perfect coincidence of the respective high waters, the moon must be further 
from the meridian of the place than the sun; so that the greatest direct tides 
ought to happen a little before the syzygies, and the greatest inverted tides a 
little after ; and from this consideration, as well as from some others, it seems 
probable that the primitive tides, which affect most of our harbours, are rather 
inverted than direct.” 
As aconvenient epoch for dating the beginning of a series of tides, it is ob- 
served that the mean conjunction, at the beginning of 1824, happens exactly at 
mean noon of Jan. 1, in the time of the island of Guernsey or of Dorchester, 
and at 18™ 49s Parisian mean time. 
It is further observed respecting the effects of resistance, that this cause ‘¢ tends 
greatly to diminish the variation in the magnitude of the tides, dependent on 
theirnear approach to the period of spontaneous oscillation, and the more as the 
resistance is the more considerable ; and supposing, with Laplace, that in the 
port of Brest, or elsewhere, the comparative magnitude of the tides is altered from 
the proportion of 5 to 2, which is that of the forces, to the proportion of 3 to 13 
the multipliers of the solar and lunar tides being to each other as 5 to 6,... 
we find that B must be either .g380 or .6398, and the former value making the 
lunar tide only inverse, we must suppose the latter nearer the truth; and the 
magnitude of the tides will become 1.663 and 1.998, and . . 4 cannot be greater 
than .632. It seems probable, however, that the primitive tides must be in a 
somewhat greater ratio than this of 2 to 1,and 5 to 3, when compared with the 
oscillations of the spheroid of equilibrium; and if wesuppose B=.g, and A still 
= = we should have [6.364] and [8.78] for their magnitude ;” so that the 
actual elevations would be about 6 and 19 feet respectively. 
“« Now... the tangents of the angular measures of the displacement, 26 7 
give us 69° 50’ and 72° 40’ for the angles themselves, when B = .6328 3 and 
’ 
