PHYSICAL OCEANOGRAPHY OF THE GULF OF MAINE 
557 
In 1915 a west-east gradation in surface temperature was recorded along 
the coast of Maine from May 10 to 14, from 7.8° near the Isles of Shoals and off 
Casco Bay to 5° off Penobscot Bay and 4.2° to 4.8° near Mount Desert Island. No 
doubt the precise readings vary with the state of the weather, however, as well as 
with the date and exact locality and from year to year. I must also caution the 
reader that at this season the surface temperature is changing so rapidly in the west- 
ern side of the gulf that a difference of a few days, one way or another, will make a 
considerable difference in the readings obtained; less so in the eastern side. 
Although the precise surface temperatures at any given date vary from one May 
to the next, depending largely on the forwardness of the season on the land, probably 
Fig. 27. — Surface temperature, first half of May, 1915 
the comparative rates of vernal warming do not vary widely from year to year in 
different parts of the gulf. 
It appears from combining the records for the three years 1913, 1915, and 1920, 
that this change is most rapid in the inner part of Massachusetts Bay, where the 
surface warmed from 3.05° on April 6 (station 20089) to 8.89° on May 16 (station 
20123) in 1920. Similarly, temperatures taken by the FisJi Hawk in 1925 show the 
surface of the southern side of the bay, generally, warming from 5.3° to 6.8° on 
April 21 to 23, to 7° to 11° on May 20 to 22. 
At the mouth of the bay, where the surface does not chill to so low a figure at 
the end of the winter, a less rapid rate of vernal warming causes about the same 
