BIGELOW: EXPLORATIONS OF THE COAST WATERS. 



213 



seasons covered by our work, was only about .6%o on the surface 

 (Fig. 49, 50), though here the change was practically as great at all 

 depths as on the surface. 



Another local difference, which deserves special note, for' its bear- 

 ing on the cause of the annual spring and summer freshening, is 

 that salinity reaches its minimum much earlier in the year in the 

 eastern than in the western part of the Gulf. For example, while 

 salinity is at its maximum, and the upper layers at their minimum, 

 at about the same season (Fig. 44) in the trough north of Cape Ann 



Fig. 53. — Surface temperature of the northern half of the Gulf of Maine, May, 1915. 



as east of the latter, the deeper layers are at their minimum there in 

 May instead of in midsummer. And further east, i. e., off Matinicus 

 (Fig. 48), next the coast east of Mount Desert, the eastern side of the 

 Eastern Basin (Fig. 49, 50), German Bank (Fig. 52) and Lurcher 

 Shoal (Stations 10272, 10315, p. 340), the entire column of water was 

 freshest in May after which a rise in salinity took place at all depths. 

 The general hydrographic changes which characterize the Gulf as a 

 whole as exemplified by the observations in 1915, are illustrated by the 

 charts and profiles (Fig. 53-71). 



