USES OF SALT SEAS. 23 
with the waves of the Polar Sea, form a bed of mean density light 
enough to maintain itself and flow off towards the Atlantic Ocean. 
These surface movements determine in the lower regions certain 
contrary movements, whence originate the powerful counter currents 
which ascend the Straits from Baffin’s Bay and reappear in the 
mysterious ‘ Polynia’ of Kane, diffusing there its treasure of heat 
brought from intertropical seas.” Dr. Kane, in his interesting 
narrative, reports an open sea north of the parallel of 82°, which he 
and his party crossed a barrier of ice eighty miles broad to reach, 
and before he reached it the thermometer marked 60°. Beyond this 
ice-bound region he found himself on the shores of an iceless sea, 
extending in an unbroken sheet of water as far as the eye could 
reach towards the Pole. Its waves were dashing on the beach with 
the swell of a great ocean; the tides ebbed and flowed. Now the 
question arises, Where did those tides have their origin? The tidal 
wave of the Atlantic could not have passed under the icy barrier 
which De Haven found so firm; therefore they must have been 
cradled in the cold sea round the Pole ; in which case it follows that 
most, if not all, the unexplored regions about the Pole must be 
covered with deep water, the only source of strong and regular tides. 
Seals were sporting, and water-fowi feeding, in this open sea, as Dr. 
Kane tells us ; and the temperature of the water which rolled in and 
dashed at his feet with measured beat was 36°, while the bottom of 
the icy barrier of eighty miles was probably hundreds of feet below 
the surface level. 
“« The existence of these tides,” says Maury, “ with the immense 
flow and drift which annually take place from the Polar Seas and the 
Atlantic, suggests many conjectures as to the condition of these 
unexplored regions. Whalers have always been puzzled as to the 
breeding-place of the great whale. It is a cold-water animal, and, 
following up the train of thought, the question arises, Is not the 
nursery for the great whale in this Polar Sea, which is so set about 
and hemmed in by a hedge of ice, that man may not attempt to 
trespass there ?” 
One or two points worthy of notice may be recorded here. 
Shallow water, and water near the coast, or covering raised sand- 
banks, is colder than water in the open sea. Alexander von 
Humboldt explains this phenomenon by supposing that deep waters 
of higher temperature re-ascend from the lowest depths and mingle 
with the upper beds. Fogs are frequently formed over sand-banks, 
because the cold water which covers them produces a local precipita- 
tion of atmospheric vapour. The contour of these fogs are perfectly 
