THE SPECIFIC GRAVITY OF THE SEA, ETC. 211 



peraturc decreased as llodgers approaelied the sliorc, yet the 

 specific gravity decreased also, because the saltness decreased by 

 reason of the increasing proportion of river water as he neared 

 the shore. And thus we have in our own waters an illustration 

 and an example of how water that is cool and light — because not 

 so salt — may be made to cover and protect as with a mantle, a 

 sheet of warmer, but Salter and heavier water below. 



427. A71 under current of warm hut salt and heavy water. — The 

 mean specific gravity of the Arctic Ocean water as observed by 

 Eodgers, and reduced to the freezing-point (27''.2) of sea water, 

 was 1.02C3. The specific gi-avity of the Gulf Stream water, as 

 observed by him, and reduced to the same temperature (27°.2), 

 was 1.0303. If these be taken as fair specimens of the water of 

 the torrid and frigid zones, it would appear that the waters of 

 intertropical seas have 15 per cent, more salt in them than the 

 surface water of the Arctic Ocean has. It is to be regretted that 

 the hydrometer has not been more frequently used in the Arctic 

 Ocean, for a careful series of observations upon the specific 

 gravity of the water there at the surface and at various depths 

 would indicate to us not only the extent to which the water 

 there is diluted by the rivers and the rains, but it would yield 

 other highly interesting results. Now this salt and heavy 

 water, whose specific gravity at 27*^.2 would have been 1.0303, is 

 the very water which Eodgers observed in the Gulf Stream on its 

 way to the arctic regions. This is the water which, after passing 

 the Grand Banks and meeting the diluted water as an ice-bearing 

 current from the north, dips down, but continues its course as an 

 under current. It is protected from farther loss of heat, after the 

 manner of our own littoral waters, b}^ the colder but lighter and 

 upper current from the north, until it enters the Arctic Ocean, 

 there to rise up like a boiling spring in the centre of an open 

 sea. 



428. De Havens water shy. — Eelying upon a process of reasoning 

 like this, and the deductions flowing therefrom. Lieutenant De 

 Haven, when he went in command of the American expedition in 

 search of Sir John Franklin and his companions, was told in his 

 letter of instructions, to look, when he should get well up into 

 "\\ ellington Channel, for an open sea to the northward and west- 

 ward. He looked, and saw in that direction a " water sky." 

 Captain Penny afterwards went there, found open water, and 

 sailed upon it. The open sea in the Arctic Ocean is probably not 



