Surface maxima north of Cape Cod 
(Nantucket data missing) were greater by 
2°F and 4°F at Portland Lightship and 
Georges Shoals respectively than in 1956; 
at Boston Lightship it was lower by 0.7°F. 
From Ambrose through Savannah Lightships 
(Diamond Shoals excepted) surface maxima 
were both earlier and lower than in 1956. 
Thus, north of Cape Cod summer surface 
temperatures followed a smooth curve, 
roughly parallel to the mean, whereas 
south of the Cape temperatures leveled off 
abruptly after the first 10 days of July. 
Bottom temperature. 
At the bottom along the continental 
shelf both minimum and maximum temperatures 
occur during isothermal conditions of late 
winter and early fall. Thus, the 1957 
bottom minima, like the surface minima, 
were above those for 1956. This was true 
of all stations with the exception of 
Nantucket, where an intrusion of cold water 
at depth occurred in what had been a 
completely mixed column two weeks earlier. 
Maximum temperatures at the bottom 
occurred at the same time or earlier than 
in 1956. As should be expected they occur 
at the time of the autum overturn which 
mixes bottom water with the warmer water 
of the upper layers. Thus, bottom maximum 
temperatures are dependent upon the time 
of occurrence of autumn storms. Early 
autumn storms which abruptly destroy the 
thermocline produce high bottom maxima as 
in 1957; if the overturn is delayed until 
cooling is advanced at the surface, bottom 
maxima will be relatively lower as in 1956. 
This explains how the bottom maxima could 
be generally higher in 1957 than in 1956 
(as they were from Boston to Winter Quarter, 
inclusive), even though the surface maxima 
were generally lower. It also points out 
the dangers inherent in trying to postulate 
bottom conditions from a knowledge of sur- 
face temperature regimes. 
