184 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
Isle of Man, showed a difference between surtace and 
bottom of 225°C. Here the tidal stream is slight, or 
barely perceptible. 
Summarising the results of these hydrographic 
soundings, we find the following conditions :— 
1. Coldest at the bottom : 
60 cases (mean differences in Table IV); 
2. Warmest at the bottom: 
3 cases: mean difterence, 0°125° C. 
- 
~ 
. Intermediate cold stratum: 
7 cases: mean difference, 0'175° C.; 
4. Intermediate warm stratum: 
Ge 
Nee! 
) 
3 cases: mean difference, 0°125° C. ; 
. Water absolutely homothermic: 
(oon 
3 cases. 
All these figures show that the Irish Sea is a practi- 
cally homothermic water mass. The slght vertical 
differences of temperature can be traced to causes such as 
those indicated by Dr. Bassett in the preceding paper in 
this Report. 
Some Conclusions. 
So far as hydrographic investigation is concerned, 
the Irish Sea presents problems of a similar nature to 
those encountered elsewhere in the British area. It is, 
for instance, certain that here, just as in the case of the 
North Sea and English Channel, the annual influx of 
relatively high-salinity water, due to the variation in 
strength of the Gulf Stream Drift, can be detected. But, 
there are also special conditions and problems. ‘The 
Irish Sea is a comparatively small sea area, and the extent 
of coast-line, and, therefore, the amount.of land drainage, 
is relatively greater than in the case of the North Sea. 
It is shallow and characterised by high and strong tides; 
and, as a result of these conditions, there is a greater 
