50$ KOVUM ORGAKUMf, ^HOOK II. 



between eacli advance and retreat, witli some little dlfTercnee, 

 agreeing uitli the motion of the moon. We have here the fol- 

 lowing cross-ways. 



This motion must be occasioned cither by the advancing and 

 the retiring of tlie sea, like water shaken in a basin, which leaves 

 one side while it washes the other ; or by the rising of the sea 

 from the bottom, and its again subsiding, like boiling water. 

 But a doubt arises, to which of these causes we should assign 

 the flow and ebb. If the first assertion be admitted, it follows, 

 that when there is a flood on one side, there must at the same 

 time be an ebb on another, and the question therefore is reduced 

 to this. Now Acosta, and some others, after a diligent inquiry, 

 luive observed tliat the flood tide takes place on the coast of 

 Florida, and the opposite coasts of Spain and Africa, at the 

 same time, as docs also the ebb ; and tliat there is not, on the 

 contrary, a flood tide at Florida when there is an ebb on the 

 coasts of Spain and Africa. Yet if one consider the subject 

 attentively, this does not prove the necessity of a rising motion, 

 nor refute the notion of a progressive motion. For the motion 

 may be progressive, and yet inundate the opposite shores of a 

 channel at the same time ; as if the waters be forced and driven 

 together from some other quarter, for instance, which takes place 

 in rivers, for they flow ancf ebb towards each bank at the same 

 time, yet their motion is clearly progressive, being that of the 

 waters from the sea entering their mouths. So it may happen, 

 that the waters coming in a vast body from tlie eastern Indian 

 Ocean are driven together, and forced into the channel of the 

 Atlantic, and therefore inundate both coasts at once. We must 

 inquire, therefore, if lliore be any other cliannel by which the 

 waters can at the same time sink and ebb: and the Southern 

 Ocean at once suggests itself, which is not less than the Atlantic, 

 but rather broader and more extensive than is requisite for this 

 effect. 



We at length arrive, then, at an instance of the cross, which 

 is this. If it be positively discovered, tliat when tlie flood sets 

 in towards the opposite coasts of Florida and Spain in the 

 Atlantic, tliere is at the same time a flood tide on the coasts of 

 Peru and the back part of China, in the Southern Ocean, then 

 assuredly, from this decisive instance, we must reject the asser- 

 tion, that the flood and ebb of the sea, about which we inquire, 

 takes place by progressive motion ; for no other sea or place is 

 left wiere there can be an ebb. But this may most easily bo 

 learnt, by inquiring of the inhabitants of Panama and Lima 

 (where the two oceans are separated by a narrow isthmus), 

 whether the flood and ebb takes place on the opposite sides of 

 the isthmus at the same time, or the reverse. This decision or 

 rejection appears certain, if it be granted that the earth is fixed; 



