THE SALTS OF THE SEA. 245 



struction. Feh. 24:th. The iceberg still in sight, but drifting away 

 fast to the north-east. Feb. 25th. The iceberg that so lately threat- 

 ened our destruction had driven completely out of sight to the 

 north-east from us." 



483. Now, then, whence, unless from the difference of specific 

 Temperature of the gravity duo to soa Water of different degrees of salt- 

 under current j^ggg ^nd temperatiu-e, can aa'o derive a motive power 

 in the depths of the sea, with force sufficient to give such tre- 

 mendous masses of ice such a velocity ? What is the temperature 

 of this under current ? Kodgers's observations (§ 480) would 

 seem to indicate that at the depth of 150 feet it is not below 40°. 

 Assuming the water of the surface current which runs out with 

 the ice to be all at 28°, as De Haven found it (§ 479), we observe 

 that it is not unreasonable to suppose that the water of the under 

 cmTent, inasmuch as it comes from the south, and therefore from 

 warmer latitudes, is not so cold ; and if it be not so cold, its tem- 

 perature, before it comes out again, must be reduced to 28°, or 

 whatever be the average temperature of the outer but surface cm- 

 rent. Dr. Kane found the temperature of the open sea in the 

 Arctic Ocean (§ 429) as high as 36°. Can water in the depths 

 below flow from the mild climate of the temperate zones to the 

 severer chmates of the frigid zone without falling below 36° ? To 

 what, in the depths of the sea, can a warm cm-rent of large volume 

 impart its heat ? The temperatm-e of sea water from the tropics 

 in which ice is forming is invariably (§ 442) 28°. Does not the 

 <3ircumstance of De Haven's invariahly finding this to be the tem- 

 peratm-e beloAV the ice on which he drifted tend to confirm the 

 conjecture (§ 479) about the ice and the river water ? 



484. This under polar current water, then, as it rises to the top, 

 jt comes to the and is brought to the surface by the agitation of the 

 surface. g^^ ^ j^^ arctic rogious, gives out its surplus heat 

 to wami the atmosphere there till the temperatm-e of this warm 

 imder current water is lowered to the requisite degree for going 

 •out on the surface. Hence the water-sky of those regions. And 

 the heat that it loses in falling from its normal temperature, be 

 that what it may, till it reaches the temperature of 28°, is so much 

 caloric set free in the polar regions, to temper the air and miti- 

 gate the climate there. Now is not this one of those modifications 

 of chmate which may be fairly traced back to the effect of the 

 saltness of the sea in gi^Hng energy to its circulation ? Moreover, 

 if there be a deep sea in the polar basin, which serves as a recep- 



