Titles in the Mediterranean and Adjacent Seas 



365 



The comparison of this chart with later ones based on far more extensive 

 observations shows how good WhewelTs picture of the North Sea tides was 

 already at such an early period. 



i, , .1 150 



Fig. 152. 



-tidal lines of the North Sea according to Whewell. (The numbers indicate 

 approximately the corrected establishments in lunar hours.) 



This accurate conception was, however, forgotten later on, when Airy, 

 in his book Tides and Waves (1845) denied the existence of amphidromies 

 and rotary tides and expressed the opinion that the distribution of the tides 

 in the North Sea is mainly determined by progressive waves, whose pro- 

 pagation was influenced above all by the depth (see p. 148). The chart given 

 by Airy, compared to that of Whewell, must be considered as a step back, 



