PHYSICAL OCEANOGEAPHY OF THE GULF OF MAINE 781 



next day (10220) , and at the same relative position off Marthas Vineyard on the 26th 

 of that August (10261), yielded salinity sections similar in type (fig. 144), though 

 with actual values considerably lower in the upper 150 meters. The bottom water 

 at all these stations has been close to 35 per mille at depths greater than 300 meters. 

 None of our stations have been located far enough out from the edge of the con- 

 tinent to show the true tropical-oceanic distribution of salinity — namely, saltest at 

 or very close to the surface and decreasing with increasing depth down to 600 to 1 ,000 

 meters. Curves of this sort result, for example, from the observations taken by the 

 United States Coast Survey steamer BacTie on her profile from Bermuda to the 

 Bahamas in January, 1914 (Bigelow, 1917a, figs. 8 and 9), and by the Dana near 

 Bermuda in May, 1922 (Nielsen, 1925, fig. 5); but when the so-called "inner edge 

 of the Gulf stream " approaches the edge of Georges Bank, as in July, 1914, doubtless 

 one need run off only a few miles into the oceanic basin to find the salinity so distrib- 

 uted there. 



GENERAL DISTRIBUTION OF SALINITY BELOW THE SURFACE 



The spacial relationships of the differences in salinity just outlined and the 

 general state of the gulf in summer are made more graphic by the usual projections — 

 horizontal and profile. 



The salting of the eastern side of the gulf, which takes place from June to 

 August (p. 765), contrasted with the freshening of the western side of the basin as 

 land water is dispersed seaward (p. 763), produces a decided alteration in the 

 distribution of salinity from late spring through the summer at moderate depths as 

 well as at the surface (p. 763). In 1915 these changes resulted in an increase in the 

 salinity of the 40-meter level from about 32.5 per mille to about 32.8 to 33.5 per 

 mille in the northeastern part of the basin during the interval between the last week 

 of June (fig. 133) and the end of August, contrasting with a decrease in its 

 western side from about 32.9 per mille to about 32.6 per mille, though very little 

 seasonal alteration took place meantime in the coastal zone near Mount Desert, on 

 the one hand (about 32.3 per mille), or near Cape Sable on the other (about 31.9 

 per mille) . 



The most interesting feature of the 40-meter chart for July and August, 1914 

 (fig. 145), which may be taken as typical of the season (there being no reason to 

 suppose that this was either an abnormally fresh or an abnormally salt year), is 

 the regular gradation from low values in the western side of the gulf to a tongue 

 of high salinity (33 + per mille) in the eastern side of the basin, again giving place 

 to a narrow zone of much fresher water along western Nova Scotia, with stUl lower 

 values (31.8 per mille) near Cape Sable and eastward along the outer coast of Nova 

 Scotia (Bigelow, 1917, fig. 33). 



A much wider extent of 33 per mille water in that August than is shown 

 on the May and June charts for 1915 (figs. 125 and 133) no doubt reflects some 

 seasonal drift inward from the Eastern Channel after the slackening of the Nova 

 Scotian current, with the isohaline for 32.9 per mille revealing a tendency for the 

 saltest band to circle westward along the coastal slope of Maine, bringing salinities 

 as high as 32.9 to 33 per mille as far as the ofiing of Penobscot Bay. A tongue of 



