BIGELOW: EXPLORATIONS IN THE GULF OF MAINE. 91 



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's Bank, off the Penob- 

 scot, is intermediate between the two extremes (the figures are: — 

 Stations 33 and 35, 32.5%o; Station 25, 32.6%o; Station 11, 32.3%o; 

 Station 19, 32.4%o; Station 2, 32.2%o). 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 oft'-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 eastern 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 

 oft' 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, i. e., 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 



