The action of these great planetary bodies on each other,--it surely cannot be denied,--leaves them separate identities, precisely as before; and it is a species of agency, so essential to the magnificent harmony of the system, that we cannot conceive it to have been interrupted, for a single moment, since the universe itself was formed. An action, therefore, has been constantly taking place on all the bodies in the universe,--and consequently a difference of some sort produced,--which yet leaves their identities unaffected. But, though the identity of the substance of the separate orbs is not affected by their mutual attractions, the _state_, or temporary physical character, of these orbs,--considered individually as one great whole,--_must_ be affected,--or it would be absurd to speak of their mutual agency at all; for action implies the sequence of a change of some sort, and there can be no action, therefore, where the substances continue precisely the same, and their state also precisely the same, as before the action. Accordingly, we find, on our own globe, that great changes of state, such as form the most striking of its regular visible phenomena, are produced by this distant operation. The waters of our ocean, for example, rise and fall,--and, therefore, must have altered states, or physical tendencies, in consequence of which they rise and fall, as there is no corresponding addition or subtraction of matter,--at regular intervals,--which it is in our power to predict with infallible accuracy,--not because we can divine any loss of identity in the fluid mass,--any internal change in its elementary composition, or the nature and varieties of the winds, which are to sweep along its surface,--but because we know well, at what hours, and in what relative situation, a certain great body, at the distance of some hundreds of thousands of miles, is to be passing along the heavens.