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granted, that this motion concerning which we are in. quiring be one of these two, — either a motion of rising and falling of the waters, or a motion of progression. Now by motion of rising and falling I mean such motion as is found in boiling water, which rises up
in the boiler and then sinks again; whereas by progressive motion I mean such as is found in water carried in a basin, which runs from one side up against the other. But that this motion is not of the first kind appears principally from this, that in the different parts of the world tides vary in point of time; so that in some places there is a flow and increase, when elsewhere there is an ebb and decrease. Now, if waters did not move from place to place but boiled up from the bottom, they ought to rise and fall everywhere at once. For we see that those two other motions, the half-monthly and the half-yearly, act and operate over the whole world at the same time. For the flow of the tide is increased everywhere at the equinox, not in some places at the equinox and in others at the tropics ; and so it is with the half-monthly motion. For the tide is highest at the new moon everywhere, and at the quarter nowhere. In these two motions therefore the waters really seem plainly to rise and fall, and to have, as it were, their apogees and perigees like the celestial bodies. Now, in the ebb and flow of the sea, of which I am speaking, it is quite the contrary ; which is the surest sign of motion in progression. Besides, if the flow of the tide be set down as a rising, we must observe somewhat more carefully how this rising is caused. For the swelling must be caused either by an increase in the quantity of water, or by an extension or rarefaction of the water in the same quantity, or by a simple lifting up in the same quantity and the same body. But this third cause is to be absolutely rejected. For if the water be lifted up as it is, there must of necessity be a vacuum between the ground and the bottom of the water, since there is no body to take its place. And if there is a fresh body of water, it must emanate and spring from the earth. But if it be only an extension, that will be caused either by a solution into a rarer body, or by a desire of approaching some other body, which, as it were, summons out and attracts the water and raises it up. And certainly this, whether it be ebullition or rarefaction, or agreement of the waters with some one of the higher bodies, does not appear incredible, if it be in a moderate quantity, and a tolerable length of time likewise be allowed for the swelling or increase of the water to collect and rise. Therefore the excess of water observable between the ordinary tide and the half-monthly which is fuller, or even the half-yearly which is fullest of all, - seeing that it is not greater than the difference between the flow and ebb, and has likewise a long enough interval to make this increase gradually, — is nothing contrary to reason. But that so great a mass of water should burst forth, as to account for the difference between the ebb and flow; and that this should be done so quickly, namely, twice a day; as if the earth, according to that foolish conceit of Apollonius, were taking respiration, and breathing out water every six hours and then taking it in again ; is a very great difficulty. And let no one be influenced by the trifling experiment, that some wells in some places are said to have a correspondence with the ebb and flow of the sea ; whence one might suspect that the waters inclosed in the cavities of the W
earth boil up in a like manner ; in which case the swelling could not be well referred to the progressive motion of the waters. For the answer is easy, that the coming in of the tide may close up and fill many hollows and loose places of the earth, turn the subterraneous waters, and beat back the inclosed air ; which in a continued succession may raise up the waters of such wells by simple protrusion. Therefore this does not happen in all wells, nor indeed in many ; which should be the case if it were the nature of the universal mass of waters to rise and fall by turns, and to correspond with the tide of the sea. But on the contrary, it is so extraordinary as almost to be regarded as a miracle ; because (no doubt) such openings and passages extending from wells to the sea are very seldom found without some stoppage or impediment. And it is not out of the way to mention what some say,
that in deep mines near the sea the air becomes so thick on the flow of the tide as to threaten suffocation ; from which it would appear not that the waters boil up (there being none seen), but that the air is driven back. But indeed there is another experiment which is not to be despised, but is of great weight, and by all means deserves an answer ; namely, that it has been found by careful observation (not accidentally noticed, but purposely inquired and discovered) that the tide ebbs on the opposite coasts of Europe and Florida at the same time, and that it does not leave the coast of Europe when it moves to that of Florida, like water stirred in a basin (which I spoke of before), but that it plainly rises and falls on both coasts at the same time. But the solution of this objection will clearly appear in the observations I shall make presently on the course
and progression of the ocean. Now the sum of the matter is this, that the waters which set out from the Indian Ocean, being obstructed by the opposition of the old and new worlds, are driven through the Atlantic from south to north ; so no wonder that they approach equally at the same time to both shores, as waters use to do which are driven by the sea into the mouths and channels of rivers, wherein it is most evident that the motion of the sea is progressive with respect to the river, and yet overflows the opposite shores both at the same time. This however I candidly admit, as my manner is, and I would have men attend and remember it; if on experience it be found that it is high water on the coasts of Peru and China at the same time as on the above-mentioned coasts of Europe and Florida, my opinion that the ebb and flow of the sea is a progressive motion must be given up. For if it be high water at the same time on the opposite shores both of the Southern ocean and the Atlantic, there are no other shores left in the world where there can be at the same time a corresponding ebb. But on the result of an appeal to experience (to which I have submitted the cause) in this matter, I feel tolerably
For I am plainly of opinion that, if we knew how the case stands all over the world, we should find that the arrangement is fair enough, and that there is at any given hour an ebb in some parts of the globe equal to the flow in others. Wherefore, from what has been said, let this motion of ebb and flow be set down as a progressive motion.
Next comes the inquiry, from what cause, and by what correspondence of things this motion of the ebb
and flow arises and exhibits itself ? For all the greater motions (if they be likewise regular and constant) are not solitary or (to use an astronomical term) ferine, but have in the nature of things some with which they correspond. And therefore these motions—both the halfmonthly motion of increase and the monthly motion of restoration -- appear to correspond with the motion of the moon; the half-yearly? or equinoctial motion, with that of the sun; and likewise the risings and fallings of the waters with the apogees and perigees of the heavenly bodies. Yet it will not immediately follow (and we would have men observe this) that things which correspond in the course and periods of time, or even in the manner of carriage, are in their nature subordinate, and the cause one of the other. For I do not go so far as to assert that the motions of the moon or sun are set down as the causes of the inferior motions which are analogous to them, or that the sun and moon (as is commonly said) have dominion over those motions of the sea (though such thoughts easily find entrance into men's minds by reason of their veneration for the heavenly bodies); indeed in that very halfmonthly motion (if rightly observed) it would be a very strange and novel kind of obedience, for the tides at the new and full moon to be affected in the same way, while the moon is affected in opposite ways; and many other things might be adduced which would destroy these fancies about dominations, and lead us rather to conclude that these correspondences arise out of the universal passions of matter, and the primary combinations of things, not as if one were gove erned by the other, but that both emanate from the 1 Semimenstruus in the original ought apparently to be semestris. — J. S.