CANADIAN FISHERIES EXPEDITION, 1911,-15 



243 



The vertical movements of the water described in this chapter, which are due 

 to the earth's rotation, are naturally opposed, in a very important degree, by the 

 Archimedean forces. With water of very high stability, these forces may entirely 

 prevent the screwing movement of the water, all that takes place being then a current 



Fig. 27. — Experiment with vertical air blast against surface of water in layers. 



(Tank rotating.) 



in the isosteric surfaces, which are deformed in the manner shown in fig. 22. In a 

 coastal current, where the water is in layers of great stability, the surface water will 

 therefore flow parallel with the coast. If, however, the stability of the strata be so 

 slight that the deflecting tendency of the earth's rotation exceeds the maximal value 

 of the Archimedean forces, then the screwing movement will thoroughly stir the 

 water in which it takes place, rendering the layer highly homogeneous, so that the 

 dividing surface between it and the next will be sharply defined. After this, there 

 will be nothing to hinder the screwing movement of the water in this homogeneous 

 layer, and the movement in question will thus attain its full development. This 

 explains the high component of movement towards the coast in the surface portion 

 of the comparatively homogeneous water south of Newfoundland, whereas in the 

 Gaspe current, a layer formation of great stability, no such landward movement takes 

 place {vide fig. 28). Even down on the banks to the south of Newfoundland, the 

 water often flows northward, the bottom water, owing to the screwing movement, natur- 

 ally having a component southwards. Thus the dangerous character of the Canadian 

 Atlantic coast as regards navigation is due to the homogeneous nature of the water. 

 If at any season the sea-water there should be overlaid by lighter surface water in 

 stable layer formation, there would then be no danger of ships being driven on shore 

 by the current, as long as such surface water was present. 



