THE FRESH-WATER LOCHS OF SCOTLAND. 
419 
the surface current, directly produced by the wind, carrying the warm 
surface water along with it, and the return current, to take the place 
of the water blown along the loch, is spread throughout tjie whole depth 
•i-l 4 7'^ ^S'’ 4-^° 5/^ 52'' SS” 5*#'’ 55* 
FIG. 69. TYPICAL MONTHLY CURVES OF TEMPERATURE IN LOCH NESS. 
of the loch. But when the discontinuity layer has formed, the loch is 
divided into two current systems. Above the discontinuity layer there 
is the surface current produced by the wind, and the return current also 
takes place above the discontinuity layer, without directly affecting the 
