170 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



the salinities occurs, as had already been concluded from 

 the results summarised in the last table but one. 



The change due to the tide will certainly, in most 

 cases, be much smaller than that found above. On the 

 line Holyhead — Calf of Man it will probably be 

 undetectable, and on the line Piel Gas Buoy — Calf of 

 Man will probably be greater the nearer the point 

 considered is to the English coast. 



Nothing has as yet been said of the temperatures of 

 the water samples. These, of course, are higher in the 

 summer than in the winter. The surface water is in 

 many cases somewhat warmer than the underlying, but in 

 other cases it is the same. From 9*2 metres downwards 

 the temperature is fairly constant. In the case of one or 

 two of the deeper stations there is sometimes a notable 

 diminution in the temperature with depth, and in the 

 case of some of the shallower stations the temperatures 

 are rather irregular. In the shallower water this is 

 probably connected with tidal currents. 



A few words may finally be said about the position of 

 certain isohaline lines in this area. That for salinity 34 

 probably starts at Burrow Head, Wigtownshire, runs across 

 to a point a little west of the Point of Ayre, starts again 

 at the Calf of Man and runs across to Holyhead. It then 

 crosses Carnarvon Bay, making a slight curve inwards, 

 and then goes in almost a straight line across Cardigan 

 Bay, ending near Cardigan. This may be regarded as a 

 sort of mean position about which it will vary with the 

 season, so that, for instance, the portion between the Calf 

 of Man and Holyhead will sometimes (about May) make 

 a considerable bend to the east. The salinity of all the 

 water to the east of this line will be below 34. The 33 

 isohaline is clearly much more affected by seasonal 



