202 PHYSICAL GEOGRAPHY O:^ THE SEA, AND ITS METEOROLOGY. 



unerring, and we can imagine no mitigation of the climate in that 

 direction, unless it arise from the proximity, or the presence there 

 of a large body of open Avater. It is another furnace (§ 151) in 

 the beautiful economy of Nature for tempering climates there. 



426. The hydrograj^hic basin of the Arctic Ocean is large, and 

 Ster^by being di- ^^ delivcrs iuto that sea annually a very copious 

 and thtr'Iiii?%^v7^ drainage. Such an immense volume of fresh water 



mantle for the discharo'ed iuto SO Small a sea as the Arctic Ocean 



Salter and warmer -^^ ^^.^^ ^^ ^^ tOWards diluting its brinO. Fig. 2, 



sea water below. 



Plate X. (§433), shows the extent to which the brine of our 

 littoral seas is diluted by the drainage from the Atlantic slopes 

 of the United States. It will be observed by that figm^e that 

 suddenly after crossing the parallel of 34° N. the water begins to 

 grow cooler and lighter. The observations for the two curves 

 are a part of the celebrated series made by Captain Kodgers in the 

 U. S. ship " Vincennes " all the way from Behring's Straits by the 

 way of Cape Horn to New York. He cleared the inner edge of 

 the Gulf Stream in 34°, where the waters began to grow cooler 

 and hghter, and so continued to do as he approached the shore. 

 The remarkable and sudden approach of the thermal and specific 

 gTavity curves after crossing 34^ N. can be explained by no other 

 hypothesis than this, viz. : the surface water of the sea v/as so 

 diluted with the fresh water from the Chesapeake, the Delaware, 

 and New York Bays, that, notwithstanding the temperature de- 

 creased as Eodgers approached the shore, yet the specific gravity 

 decreased also, because the saltness decreased by reason of the in- 

 creasing proportion of river v>^ater as he neared the shore. And 

 thus we have in our own vv^aters 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 beiov;. 



427. The mean specific gravity of the Arctic Ocean water as 

 ^f"v'"^%f"7^i"'^ ^^^®^'^®^ ^y Bodgers, and reduced to the freezing- 

 and heavy water, poiut (27°. 2) of soa watcr, was 1.0263. The speci- 

 fic gravity of the (rulf Stream water, as observed by him, and 

 reduced to the same temperatm-e (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 regi'etted that the hydi'ometer has not been more 

 frequently used in the Arctic Ocean, for a careful series of observa- 



