PHYSICAL OCEANOGEAPHY OF THE GULF OF MAINE 825 



the water changed from a temperature of 1.1° to 13.3° C. (34° to 56° F.) within 

 the length of the ship, and where the line of demarkation between the two waters 

 was made plainly visible on the surface by ripplings, the transition zone from the 

 one to the other is usually compressed within a few miles abreast the Gulf of Maine. 



The general characteristics of the coast water in boreal latitudes have been 

 well described by Schott (1912) and are matters of common knowledge. I need 

 merely state here that mean annual surface temperatures lower than 15° and mean 

 salinities lower than about 33.5 per mille may be so classed, as distinguished from 

 the much warmer and more saline (35.5 per mille) tropic water, which is commonly 

 (though rather loosely) termed "Gulf Stream" as it skirts the North American 

 plateau. 



In discussing the sources of the sector of the coast water included within the 

 Gulf of Maine, it will be convenient to consider the upper and lower strata separately, 

 for it is now proven they they draw chiefly from different sources. 



SUPERFICIAL STRATUM 



NOVA SCOTIAN CURRENT 



Until detailed study of the physical characters of the coast water off northeastern 

 North America was undertaken by the United States Bureau of Fisheries, the Museum 

 of Comparative Zoology, and the Biological Board of Canada, a northerly source was 

 usually ascribed to the coastal water all along the seaboard of Nova Scotia, New 

 England, and much farther to the south. This, in fact, has been described, time out 

 of mind, as the "Arctic current." As I have remarked in an earlier report (Bigelow, 

 1915, p. 251), "almost all the ocean atlases show something of this sort; and it has 

 been accepted in one form or another in almost all the textbooks on physical 

 geography and oceanography (for example, Maury, 1855; Keclus, 1873; Attlmayr, 

 1883; Thoulet, 1904; Kriimmel, 1911; Schott, 1912; the German Marine Observ- 

 atory (Deutche Seewarte, 1882), the current charts of the United States Navy 

 (Soley, 1911), and the British Admirality (1897) current chart.)" 



The low temperature of the surface water near shore, contrasted with the " Gulf 

 Stream" offshore and with the oceans as a whole at the latitude in question, natu- 

 rally suggests a northern origin until analyzed in relation to other factors (p. 686). 

 Ostensible evidence to the same effect is afforded by the continuity of the cold zone 

 all along the northeastern coasts of North America, with its mean temperature grad- 

 ually decreasing from the south toward the Newfoundland-Baffins Bay region in 

 the north. The southwesterly drift that has been reported repeatedly along the 

 coasts of the northeastern United States and Nova Scotia argues in the same direc- 

 tion; so, also, the extension of a generally boreal fauna southward and westward as 

 far as Cape Cod, with planktonic communities of this category spreading still farther 

 in this direction in winter. 



The observations on the temperature, salinity, and circulation of the gulf, detailed 

 in other chapters, do, in fact, prove beyond reasonable doubt that water from 

 the northeast (low in temperature) does flow past Cape Sable into the Gulf of Maine 

 for a time in spring, sometimes into the summer. Before considering what part this 

 actually plays in the Gulf of Maine complex a few words may well be devoted to its 

 probable source. 



