188 bulletin: museum of comparative zoology. 



collected by Mr. Welsh on August 22, near the sixty fathom curve off 

 Block Island (Station 10112) proved to be very much salter (surface 

 salinity 34%o) than the water in this region during the first of July; 

 Salter, in fact, than any water on the shelf at that time, showing that 

 an indraught of ocean water took place in August. 



During the spring of 1913, Captain McFarland, of the schooner Vic- 

 tor, collected water samples at nine localities between Nantucket and 

 Delaware Bay, seven at the surface, four from 15-25 fathoms, which 

 show that early in June the surface salinity was 32.9%o thirty miles 

 south of Marthas Vineyard, 32.6%o over the southwest slope of Nan- 

 tucket shoals twenty miles west of Nantucket light-ship; and that it 

 was practically unchanged at the latter locality on June 21 (p. 351). 

 Thus the water was salter in June than in July; but while the 

 difference was considerable off Marthas Vineyard (32.9%o as against 

 32.2%o) it was very slight over Nantucket Shoals (June 6, 32.65%o; 

 June 21, 32.68%o, July 9, 32.5%o). 



Off Cape May, a few miles south of the location of our Station 10072, 

 Capt. McFarland encountered water of 34.18%o on the surface, and 

 near the bottom at twenty-five fathoms, on May 3 and May 9, which 

 is much Salter than it was there in July (about 32.4%o on the surface). 

 But as the curves show (Plate 2), 34% water would have been reached 

 only fifteen miles further off shore at that season. Apparently, then, 

 the coast water, from Cape Cod to Chesapeake Bay, is freshest in 

 July; and hence, since the outrush of river water is at its maximum in 

 May, seaward expansion must be a slow process. After July, ocean 

 water once more has the upper hand. 



Salinity sections. The water is usually freshest on the surface, salt- 

 est on the bottom, over the continental shelf south and west of Cape 

 Cod, as, indeed, is the general rule in coastal waters in summer. But 

 at three Stations, 10073, 10074, and 10077, all south of Delaware Bay 

 between the 20 and 30 fathom curves, the intermediate layers, were 

 saltest (Fig. 31, 34). The remaining, more normal, sections fall into 

 several distinct classes. There is, to begin with, one Station (10059) 

 with only a very slight rise in salinity from the surface downward 

 (surface 33.06%o; 30 fathoms, 33.1%o), a type familiar in the northeast 

 part of the Gulf of Maine in regions of strong tidal currents ; its loca- 

 tion on George's Bank, where the currents are proverbially violent, 

 and where temperature like salinity was practically uniform at all 

 depths, shows that it is a similar example of vertical circulation. 

 Judging from the tidal currents, it is probable that more or less 

 similar conditions obtain locally on Nantucket Shoals; but on their 



