a 
a eee ee Cle 
BIGELOW: EXPLORATIONS IN THE GULF OF MAINE. 9] 
raises the surface salinity by mixing, virtually equalizing the physical 
properties of the water from surface to bottom, the mean salinities 
for the upper thirty fathoms show that the water off the Grand Manan 
Channel is absolutely, as well as apparently, salter than it is at Station 
11, or off Massachusetts Bay; and that Jeffrey’ Bank, off the Penob- 
scot, is intermediate between the two extremes (the figures are:— 
Stations 33 and 35, 32.5% ; Station 25, 32.6%; Station 11, 32.3% ; 
Station 19, 32.4% ; Station 2, 32.2%). These facts must be ampli- 
fied by records from other times of year; but so far as they go they 
point to the conclusion that the coast water flows southwesterly along- 
shore, with a branch turning southward off the mouth of the Penob- 
scot; and that it swings eastward as a whole off Cape Ann. ‘The fact 
that the St. Johns water is less evident, though much greater in amount, 
than the water from the Penobscot, Kennebec, and Merrimac, can be 
explained only on the assumption that it is more constantly mixed 
with salt off-shore water than are the latter; an assumption supported 
by our observation that oceanic salinities are most closely approxi- 
mated both on the surface and in deeper layers in the easterm part 
of the Gulf. All this, of course, indicates an in-shore movement of 
water in this region in August, which mixes with the St. Johns water 
off the mouth of the Bay of Fundy, with consequent changes of 
salinity; while the occurrence of Salpae over the Eastern Basin is as 
good evidence, as is the high salinity, that at the time of our visit 
this oceanic water was an offshoot from the northern edge of the Gulf 
Stream, not of northern origin. Off the mouth of the Penobscot 
the salinity curves show that the flow is the reverse, 7. ¢., to the south; 
but off Casco Bay we once more find a tongue of comparatively salt 
water approaching the coast, and separating the Penobscot from the 
Cape Ann fresh wedge. Thus, although the actual movements of 
tidal currents do not reveal the existence of any general circulation 
in the Gulf (p.84), salinity conditions show very clearly that there is an 
influx of ocean water on the east side of the Gulf; and a longshore 
movement of the fresh coast water, sending out a southerly tongue 
off the Penobscot, and swinging eastward off Cape Cod. In other 
words, the surface of the Gulf as a whole, at the time of our cruise, was 
probably occupied by two separate eddies, which are reconstructed 
here from the salinities (Plate 4). The fact that the salinity is lower 
over the western than over the eastern side of the eastern basin, is due 
to the eddy, part of the fresh wedge off the Penobscot being drawn into 
its circulation on the west side. And the comparatively low salinity of 
the western basin, and the gradual rise of salinity from west to east 
