NOVUM ORGANUM 415 



is firm and indissoluble, whilst that of the other is unsteady 

 and separable ; by which means the question is decided, and the 

 first is received as the cause, whilst the other is dismissed and 

 rejected. Such instances, therefore, afford great light, and arc 

 of great weight, so that the course of interpretation sometimes 

 terminates, and is completed in them. Sometimes, however, 

 they are found amongst the instances already observed, but they 

 are generally new, being expressly and purposely sought for and 

 applied, and brought to light only by attentive and active dili- 

 gence. 



For example : let the required nature be the flow and ebb of 

 the sea, which is repeated twice a day, at intervals of six hours 

 between each advance and retreat, with some little difference, 

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

 lowing cross-ways. 



This motion must be occasioned either by the advancing and 

 the retiring of the 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, 

 have observed that the flood tide takes place on the coast of 

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

 same time, as does also the ebb ; and that 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 and ebb towards each bank at the 

 same time, yet their motion is clearing 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 the 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 there be any other channel by which 

 the waters can at the same time sink and ebb : and the South- 

 ern Ocean at once suggests itself, which is not less than the At- 

 lantic, 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, that when the flood sets 



