HYDUOGRAPHICAL SURVEY. 181 



where few of the little medusae exist, the sea is 

 uncommonly transparent. Captain Wood, when 

 attempting the discovery of a north-east passage, in 

 the year 1676, sounded neaT Nova Zembla in 80 

 fathoms water, where the bottom was not only to 

 be seen, but even the shells lying on the ground 

 were clearly visible. 



Never having been in a very high latitude du 

 ring any part of the year when the sun sets, I have 

 never observed whether the Greenland Sea possesses 

 the property of shining in the dark. There is, 

 however, great reason to believe, that as the lumi- 

 nousness of the sea is often derived from small ani- 

 mals of the medusa kind, that the green-coloured 

 water found in the Greenland Sea would be strong- 

 ly phosphorescent. 



The sea in the Arctic regions is of somewhat 

 less specific gravity, than it is in temperate or torrid 

 regions; and consequently less salt. The correct 

 analysis of sea-water being a difficult problem, the 

 usual measure of the saltness of the sea, is by its 

 specific gravity ; this, though but an approximation 

 to the truth, when the quantity of any particular 

 salt only is considered, gives the saline contents in 

 the gross with tolerable accuracy. A quantity of 

 sea-water taken from the surface in latitude 77° 40', 

 longitude 2° 30' E., of the specific gravity of 

 1.0^67, afforded in 1000 grains the following in- 

 gredients : 



