976 BULLETIN OF THE BUREAU OF FISHEBIES 



slope the year round, veering through west to southwest across the basin toward 

 the offing of Massachusetts Bay; and though variations in saUnity and temperature 

 prove this drift intermittent, its stream track seems comparatively constant from 

 season to season during its periods of activity. 



The correspondence between the dominant circulation of the gulf, as established 

 by direct evidence, and the dynamic gradient is close enough to show that the 

 former is essentially dynamic, set in motion by the regional inequalities in density, 

 but given its eddylike character by the confining effect of the bottom contour of 

 Georges Bank to the south. 



Deflection of the horizontal tidal oscillations by the rotation of the earth simi- 

 larly tends to produce an anticlockwise movement around the basin of the gulf, and 

 with the effect of the wind consistent with this, the several motive forces are parallel 

 in effect. 



The westerly drift of slope water along the slope of the continent is also dynamic 

 in source, and available evidence suggests the same motive power for the "Gulf 

 Stream" drift abreast of the gulf. 



TABLES OF TEMPERATURE, SALINITY, AND DENSITY 



Temperature is in degrees Centigrade, salinity in parts per mille, and density is 

 at the temperature in situ but without correction for compression. The tables on 

 page 977, summarized from Ekman's (1910) tables 2,4, and 5, give a close enough 

 approximation to the latter for general purposes in depths as small as those of the 

 Gulf of Maine. For computations involving the specific volume, Smith's (1926, p. 

 19) simplification of Hesselberg and Sverdrup's (1915) tables are to be preferred. 



STANDARDS OF ACCURACY 



The old type reversing thermometers used in 1912 and 1913 were accurate only 

 to within about ±0.15° C, but with the instruments used subsequently for the 

 subsurface readings the probable error in temperature determination is less than 

 0.05° C As the surface readings have often been taken under difficulties and by 

 various persons, accuracy is not claimed for them beyond about ±0.3° C. 



All the determinations of salinity, except some for the winter of 1925 (noted 

 below under the respective stations), have been by titration. So far as personal 

 and instrumental errors are concerned, the results are reliable considerably within 

 the requirements of the International Committee for the Exploration of the Sea — 

 probably to ±0.03 per mille of salinity. However, as Giral (1926) has recently 

 emphasized, regional or seasonal variations in the relative proportions of the various 

 solutes in sea water, such as are known to occur, introduce another source of error, 

 which makes it unsafe to claim accuracy closer than about 0.05 per mille even for 

 waters as nearly uniform in their saline content as the Gulf of Maine probably is. 



The accuracy of the calculated densities depends, of course, on that of the deter- 

 minations of temperature and salinity on which they are based; and while errors in 

 these two may partially offset each other, they may, on the contrary, be cumulative. 

 Allowing as the probable range of error 0.05° and ±0.3 per mille, the probable error 



