136 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



fluctuations in the height of high water at Liverpool* : the 

 former range between about 0-5° C. above and 1-33° C. below 

 the mean line. This is extraordinary when one assumes that 

 the differences are due, apparently, to the different areas of 

 banks covered by the tides at neaps and springs. One thing, 

 however, must be noticed : for approximately the first half 

 of the period the mean temperature for Morecambe Bay Light- 

 ship is below that at Bahama Bank. The foreshore in More- 

 cambe Bay must therefore be exercising a cooling effect since 

 the influence of the sand-banks must be greater at the former 

 position than at the latter. We should expect, then, that 

 each high-water maximum would be opposed by a temperature 

 minimum, whereas the reverse condition is shown by the graph. 

 There is bound, however, to be a lag in the change of tempera- 

 ture, because it will take some time for the effect produced 

 inshore to be felt at the lightship. The second part of the 

 smoothed curves show that the foreshore is now warming the 

 water offshore, and the temperature fluctuations produced by 

 the tides and disclosed by the three-daily averages now corre- 

 spond directly to the curve of high-water levels — so there is 

 apparently no lag. That is, there is a complete reversal of the 

 relative position of the fluctuations at the two lightships, and 

 yet the periodicity of rhythm of the three-daily temperature 

 fluctuations is apparently undisturbed. In spite of this 

 apparent anomaly we must, however, correlate the changes in 

 tidal level with the temperature fluctuations, though we must 

 not expect a very high degree of correlation since the rate at 

 which heat is transferred to and from the foreshore must 

 depend on other conditions, such as the winds. 



If the temperatures for January to March, 1908, be treated 

 in the same way a similar rhythmic fluctuation is shown. 

 But this is not so regular as in the case of 1907. The maxima 



* The difference between the times of high water at Liverpool and 

 Morecambe Bay is only about ten minutes. 





