1()8 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



probably due to the way in which the mixing of the 

 fresher and Salter water is brought about by the tides, 

 which cause the Salter water at stations 5 and 6 to be 

 gradually diluted by the less salt water from further 

 north. This will obviously result in the minim um 

 salinity at stations 5 and 6 roughly corresponding with 

 maximum salinity at the more northerly stations. The 

 different behaviour at station 7 is no doubt due to the fact 

 that at that point the tide running north is much stronger 

 than that running south, so that there is a continuous 

 slight stream from the south. 



These last considerations make it clear that in 

 considering the seasonal variation of salinity, the effect 

 of the tides must be borne in mind. 



As already mentioned, the portion of the Irish Sea 

 with which the present investigations deal is noted for its 

 strong tides, so it seemed likely that the salinity at any 

 given spot would depend to a slight extent on the state of 

 the tide : as this changed, so the water originally present 

 would be replaced by other water which might well differ 

 in salinity. It was important to see whether any 

 differences so caused were appreciable and likely to mask 

 any seasonal change in the salinity. Samples were 

 accordingly collected from one of the stations every two 

 hours throughout a tidal cycle. The station chosen was 

 that at 54° 2' N. ; 3° 47' W., as being one at which any 

 such effect would probably be well marked owing to the 

 proximity of the large body of water of low salinity in 

 Morecambe Bay. 



The results obtained are given in the following table : 



