PHYSICAL OCEANOGRAPHY OF THE GULF OF MAINE 
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outlined by the isotherm for 12° on the chart (fig. 46), also includes the whole east- 
ern side of the gulf, off western Nova Scotia, out to the 100-meter contour, in an 
undulating outline more easily represented graphically than verbally. 
The transition from warm to cool is often very noticeable as one runs from the 
offing of Cape Elizabeth, across the mouth of Casco Bay, to the neighborhood of 
Fig. 47.— Surface temperature, July to August, 1912 (above), and July to August, 1923 (below) 
Boothbay Harbor. On August 13, 1925, for example, the Halcyon had surface read- 
ings of 16° at the mouth of the bay but only 12.8° close to Seguin Island. Next 
the shore surface temperatures ranging from 13° to 15.3° have been recorded between 
Casco Bay and Penobscot Bay in August; usually cooler than 14°, but with much 
