62 bulletin: museum of comparative zoology. 



than Stations 45 and 46, made almost simultaneously, shows that the 

 discrepancy below seven fathoms between it, and Stations 2 and 7, 

 can not be wholly the result of seasonal change, in the sense of solar 

 warming. Hence it seems safe to say that at Station 43 we encoun- 

 tered a water mass distinctly warmer than the waters west, north, or 

 northeast of it. But of course it is impossible to know whether this 

 warm water would have been encountered off Cape Cod earlier in the 

 season, or whether it had moved thither between the times of our 

 two visits to Massachusetts Bay. 



Salinity. 



As pointed out above, titration is, on the whole, the most satis- 

 factory method for determining salinity, (the term salinity meaning 

 the number of grams of solids per kilogram of water) ; and the follow- 

 ing account of the salinities of the Gulf of Maine is based entirely on 

 the values arrived at by this method. 



Every water sample was titrated twice, some of them three or four 

 times, and to test the possibility that some evaporation or other 

 alteration in the salinity of the samples might have taken place be- 

 tween collection and titration, the titrations for four samples, chosen 

 at random, were repeated after an interval of two months, with the 

 following results : — 



Station 



Trial A 



Trial B 



27, surface 



32.66 



32.66 



43 95 fathoms 



33.69 



33.70 



22 45 



32.74 



32.75 



2 60 



32.92 



32.91 



The pairs of salinities agree so closely that there was evidently no 

 appreciable change as a result of storage. 



Surface salinity. — The chart of surface conditions in July and Au- 

 gust, 1912 (Plate 2) shows that the salinity was lowest close to the 

 coast, there being a band five to twenty miles broad reaching from 

 Cape Ann northward nearly to Cape Elizabeth where the salinity 

 was below 31.4, while it was highest along the western edge of the 

 Gulf, over the Nova Scotia Coastal Bank (Station 31), where water 

 of 32.84 was encountered. The curves clearly show two distinct 

 masses of water of low salinity intruding into the comparatively salt 

 waters of the central part of the Gulf. One of these was off Cape Ann, 

 where the curves of 31.4, 31.8 and 32, swing far to the eastward. The 



