DE FLUXU ET REFLUXU MARKS. 237 



mentioning several intermediate places, he says that 

 along the coast of Normandy as far as Calais and Nieu- 



i/ 



port there is high water at nine, and after a not very 

 distinct statement as to the time of high water in the 

 middle of the channel, goes on to state that from Calais 

 to Gravelines the water is high off shore (in derota) at 

 an hour and a half after midnight, that is at the same 



o 



time as at Rota, and at Zealand at the same time as on 

 the coast of Portugal. These statements are scarcely 

 sufficiently accurate to make it worth while to compare 

 them with modern observations ; but it is necessary to 

 remark that Sagrus, though he mentions it as a re 

 markable circumstance that the time of hio-h water 



O 



should be the same at Gravelines and at Rota, does 

 not mean to assert that there is any discontinuity in 

 the progress of the tide along the shores of France and 

 the Netherlands. The tide gets progressivelv later and 

 later until we come to a place where there is high water 

 about one in the afternoon, and therefore also high 

 water about half-past one after the succeeding mid 

 night. In order to compare Gravelines and Rota, he 

 takes (but without mentioning that he does so) two 

 different tide-waves, the statement with reference to 

 Gravelines appearing to relate to a later wave than the 

 other. Bacon however does not appear to have under 

 stood this ; and consequently, after saying that the hour 

 of high water becomes later and later from the Straits 

 of Gibraltar to the coast of Normandy, proceeds thus : 

 &quot; Hucusque ordinatim ; ad Gravelingam vero, verso 

 prorsus ordine, idque inagno saltu, quasi ad eandem 

 horam cum ostio freti Herculei.&quot; This notion of a 

 reversal of the order of the tides as we proceed along 

 the French and Dutch coast is not justified either by 



