PHYSICAL OCEANOGRAPHY OP THE GULF OF MAINE 
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Arctic water, according to locality), but often, if not always, heavier than the tropic 
water on the outer side as well (Witte, 1910 ; E. H. Smith, 1924, p. 140, 1925, figs. 10, 
12, and 19), causing the dynamic tendency for surface water to move in from both 
sides toward this heavy zone (or “cabelling”), which seems first to have been empha- 
sized by Witte (1910). Huntsman, too (1924, p. 278), definitely accepts “cabelling” as 
a governing event in the formation of the slope water; and although more recent 
hydrodynamic studies (see especially E. H. Smith, 1926) have made it clear that actual 
sinking is usually prevented there by the effect of the earth’s rotation, a potential 
Flo. 169. — Density profile crossing the continental shelf in the offing of Shelburne, Nova Scotia, 
March 17 to 20, 1920. Corrected for compression 
sinking zone of this sort does nevertheless tend to draw in surface water from both 
sides toward the zone where the surfaces of equal density depart most from the 
horizontal, and so to set up a horizontal circulation. 
A potential sinking zone of this same sort was revealed by one profile run off La 
Have Bank by the Canadian Fisheries Expedition in July, 1915, when the upper 100 
meters proved more dense just outside the edge of the continent (Bjerkan, 1919, 
Acadia stations 41 to 43) than in on the edge of the shelf, on the one hand ( Acadia 
