238 PREFACE TO THE 



Sagrus s statements or by the phenomena to which 

 they relate. 1 



Sagrus is probably the first writer who remarks that 

 the time of high water is not always the same as that 

 of slack water. &quot; Et illud adnotat Sagrus,&quot; says Pa- 

 tricius, &quot; non minus minim &quot; (he has been speaking 

 of the coincidence as to the time of hiffli water be- 



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tween the Dutch and Portuguese coasts) &quot; si a Selan- 

 dia quis ad caput Anglias Dobla [Dover?] naviget, 

 mare plenum erit a medinoctio tertia quidem hora, sed 

 eodem itinere, fluxus aqua3 obvius fiet per horas duas 

 cum dimidia donee flaccescat, quod nautae dicunt aquam 

 fieri stancam.&quot; Patricius rightly compares this with 

 the phenomenon observed at Venice, namely that when 

 the water has already sunk half a foot at the entrance 

 of the harbour it is still rising in the harbour itself. 



With respect to theories of the cause of the tides, it 

 may be observed that a connexion of some kind or 

 other between the tides and the moon has at all times 

 been popularly recognised. But the conception which 

 was formed as to the nature of this connexion lono-con- 



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tinued vague and indefinite ; and in Bacon s time those 

 who speculated on the subject were disposed to reject 

 it altogether. One theory, that of Telesius and Pa 

 tricius, compares the sea to the water in a caldron ; 

 that is to say it rises and tends to boil over when its 

 natural heat is called forth under the influence of the 

 sun, moon, and stars, and then after a while subsides. 

 But why should this alternate rise and fall have a 

 definite period of six hours? Patricius calmly an- 



1 I have given Sagrus s statements in extenso in a note on the passage in 

 the text. He seems to have forgotten that Nieuport is farther from Calais 

 than Gravelines. 





