SEA-FISILERIES LAPORATORY. 163 
known, this deep channel is in reality a submerged river 
valley and does not owe its origin in any way {to marie 
currents, which, therefore, need not be expected to pay 
much attention to it. The water filling this channel, even 
in the deepest parts of the Mull of Galloway, is wonder- 
fully constant in composition, merely showing the small 
increase in salinity with depth which was to be expected. 
A few words must now be said about the temperatures 
of the various soundings. Needless to say, these are 
higher in the summer than im the winter. In the majority 
of cases the temperature is practically constant from top 
to bottom, only the surface water being, asa rule, slightly 
warmer than the rest. Occasionally in some of the deeper 
stations there is a shght fall in temperature with depth, 
but our usual ten stations are not deep enough for this 
always to be observed. ‘This fall of temperature was, 
however, well marked in the case of all the deep stations 
investigated during the June trip, though the difference 
between top and bottom temperatures only amounted to 
0:7° at the deepest station (240 metres) and 2°5° at another 
station 100 metres in depth. The difference between top 
and bottom temperatures at the two shallow Stations I 
and IT is often considerable, but this 1s chiefly due to tidal 
effects. The surface water is also often abnormally warm 
at other stations near the coast, for example, those in 
Cardigan Bay. 
The question of the relation between the temperature 
at any spot and the distance from the land is discussed 
by Mr. Johnstone in a separate paper. 
Ii the preceding tables are studied carefully it will be 
noticed that in a few cases instead of a gradual fall in tem- 
perature on goie from top to bottom there is either a small 
intermediate rise or fall. This happens once at Station I (in 
October) and once at Station TI (nm February), when the water 
