THE CLYDE SEA-AREA. 



393 



tide is thus homothermic Channel water passed in sheets less than 25 fathoms 

 thick across the flat counter of the Great Plateau. 



FIG. 2. 



At the annual minimum in March the Arran Basin throughout its whole 

 depth is at the same temperature as the Channel and the Plateau ; but as 

 the process of warming goes on the superficial layers are most rapidly 



FIG. 3. 



heated by the direct influence of the sun, and by the indirect influence 

 of warm land -water which floats upon the surface of the salter mass. The 

 result is that the surface water heats up more rapidly and to a higher degree 

 than the deeper layers, which change their temperature probably because 



