BIGELOW: EXPLORATIONS IN THE GULF OF MAINE. 89 
range of temperature from surface to bottom at successive stations 
along the coast from the Penobscot to Grand Manan, the surface 
growing warmer, and the bottom colder at least at corresponding 
depths, is evidently due to the fact that the diminishing force of the 
tidal currents is less and less effective in causing vertical circulation, 
so that the waters retain more and more nearly their normal tempera- 
ture gradient. Exactly the opposite takes place in passing off shore 
from the mouth of Grand Manan Channel, the temperature and salin- 
ity range growing progressively greater. 
The mouth of Casco Bay, 2. e., the region where the general trend 
of the coast changes from northerly to northeasterly, is the dividing 
line between temperature sections of two types; for whereas the 
coast waters east of this point were about as much warmer than the 
off-shore stations on the bottom as they were colder on the surface, the 
coast water south and west of Portland was no warmer on the bottom 
than it was off Cape Ann or near Platt’s Bank, though it was constantly 
several degrees colder on the surface. On the contrary, Station 11, 
close to the coast, was colder at all depths down to about sixty fathoms 
than the water east of Jeffrey’s Ledge, and the curve at Station 14, 
off Cape Porpoise, was almost precisely like it, the same temperatures 
being found from five to ten fathoms nearer the surface at Station 11 
than at Stations 23 and 24. Below fifty fathoms the temperatures 
were about equal. If temperature were the only clue to oceanic circu- 
lation, we would naturally assume that such a profile indicated an 
upwelling of cold bottom water. But the salinities of this region, 
forbid this explanation, because, as the salinity sections show, the 
in-shore stations were fresher at all depths, whereas, if the surface were 
cooled by water rising from below, the salinity would necessarily be 
raised by the same process, and we would expect to find the surface 
salter than, or at least as salt as it was at the stations further off shore. 
But although the temperature readings at Station 11 were lower at all 
depths down to fifty fathoms, than they were east of Jeffrey’s Ledge, 
the curve for the former was almost precisely the same as it was at 
Station 2, in the mouth of Massachusetts Bay a few days earlier, 
except that the upper ten fathoms were cooler at Station 11; while the 
salinity curves (fig. 11) show that the latter was slightly salter than 
Station 2 at the surface, slightly fresher below thirty fathoms. It is 
evident that while vertical movements of such a column of water as 
was met at Station 24 could not reproduce the temperature and 
salinity conditions found at Station 11, a vertical mixing of the upper 
fifteen or twenty fathoms of the waters at Station 2 would cause 
