920 BULLETIN OF THE BUREAU OF FISHEEIES 



(fig. 53; isotlierms for 10° and 12°) suggests an eddying movement, drawing warmer 

 water inward over the bank on the western side; but in other summers the cool 

 drift extends much farther westward. Bottle drifts, for example, place 1922 in this 

 category (p. 883); and Libbey (1891 and 1895) records it in longitude 70° to 71° in 

 the summer and early autunm of 1889. 



In another chapter (p. 585) I have tried to make it clear that the areas of low 

 and high surface temperature, which characterize various parts of the Gulf of Maine 

 in summer, are due chiefly to tidal stii-ring — most active over the shoal banks and in 

 the northeastern part of the area generally, least so in the basin off Massachussetts 

 Bay. Tidal stirring also plays a part in holding the surface temperature somewhat 

 lower along the western margin of the gulf and around the shore of Massachussetts 

 Bay than a few miles out at sea ; but the gradation also points to some movement 

 of the surface water eastward, away from the shore, under the impulse of the 

 prevailing southwestern winds, an event with which bathers on our beaches have 

 long been familiar (p. 588), and which takes part in the development of the western 

 side of the Gulf of Maine eddy. The evidence (by bottle drifts) of a westerly set 

 from the Nova Scotian side and from the Bay of Fundy along the coast of Maine is 

 also borne out by the extension of surface water colder than 14° westward past 

 Penobscot Bay in August (figs. 46 and 47) over depths so great that tidal stirring, 

 in situ, is not active enough to be responsible, per se, for surface values as low as 

 those actually recorded there. 



The 40-meter charts for July and August (figs. 52, 53, and 54) also suggest a 

 similar westerly drift by the isotherms for 8° and 9°, though at this depth the water 

 moving in that direction from the Nova Scotian side is warmer than that which it 

 replaces off the coast of Maine — not colder, as it is at the surface. (For discussion 

 of this bathymetric difference, see p. 608). 



The mutual relationships of waters warmer and colder than 9° were especially 

 suggestive in August, 1913, as locating the vortex of the anticlockwise eddy about 

 60 miles south of Mount Desert and Penobscot Bay (fig. 52). The correspond- 

 ing chart for 1914 (fig. 53) is not so easy to interpret in this respect, the picture 

 being complicated in the western side by a pool of water cooler than 6°, which 

 probably owed its low temperature to vertical stirring or to local upwelling in the 

 mid depths. 



None of the summer charts for temperature reveals any dominant movement of 

 warm water into the gulf fi'om offshore at the surface, nor do the 40-meter charts for 

 the summers of 1914 or 1915, but some circulatory indraft of this sort is suggested 

 on the 40-meter chart for 1913 (fig. 52) by temperature, just as it is by salinity 

 (p. 782), by the warm (>10°) tongue in the eastern side of the basin, with lower 

 temperatures on either hand, to which the reader's attention has already been called 

 (p. 608). 



At first sight the distribution of temperatures at 40 meters prevailing in July, 

 1914 (fig. 53), might suggest a drift into the gulf from offshore across the eastern end 

 of Georges Bank, but a closer analysis makes it clear (p. 617) that in this case unity 

 of temperature had a local significance only, being- an adventitious result of the fact 

 that vertical mixing was most active on the northern part of the bank. 



