298 Astronomical and Nautical Collections. 
sea; but merely to understand, that these parts are left a little 
behind, while the central parts fall more within the tangent, to- 
wards the moon, and the nearer parts still more than the central 
parts: nor is this a faet of which our belief must rest on any ob- 
served phenomena of the tides, since it is completely demonstrable 
from the general laws of gravitation and of central forces: so that 
if no such tides were under any circumstances observable, their 
non-existence would afford an unanswerable argument against the 
universality and accuracy of these laws, as they are inferred from 
other phenomena. 
‘* The second objection is already answered in the statement of 
the mode of operation of the disturbing force. The action of this 
force is only supposed to be sufficient to retain a particle of water 
in equilibrium on a surface of which the inclination to the horizon 
is scarcely perceptible, or to cause the whole gravitation of a 
column four thousand miles in height, immediately under the lu- 
minary, to be equal only to the gravitation of a column shorter by a 
few inches or feet, in another part of the spheroid. The objectors 
have confounded this very slight modification of the force of gravi- 
tation, with its complete annihilation by a greater force: and with re- 
spect to the force of cohesion, it is so little concerned in counteracting 
any elevation of this kind, that to attempt to calculate the magnitude 
of any resistance derived from it would be perfectly ridiculous. 
“‘ The third objection is only so far more valid, as it is opposed 
to the imperfect and superficial notions,” which some authors have 
entertained, “ of the supposed operation of the forces concerned :” 
as if the sea could instantly accommodate itself to the temporary 
form which would afford an equilibrium. In fact, however, it is 
just as likely to happen, in the open ocean, that the transit of the 
luminary may coincide with the time of low water as with that of 
high water; and in more limited seas and lakes, there is no hour 
in the twenty-four at which high water may not naturally be ex- 
pected to take place, according to the different breadth and depth 
of the waters concerned; while, under other circumstances, it may 
happen to be high water only once a day, or once a fortnight, or 
there may be no tide at all, without any deviation from the strictest 
