58 ANNUAL RECORD OE SCIENCE AND INDUSTRY. 



gard to the thermal stratification of an area which may be 

 set down at nearly 15,000,000 square miles, and which has an 

 average depth of at least 15,000 feet. He recapitulates his 

 views in the following propositions : 



First. That apart from the horizontal circulation produced 

 by the action of winds upon the surface of the ocean, there is 

 a vertical circulation maintained, in consequence of the dif- 

 ference between the polar and equatorial areas ; the whole 

 mass of water contained in any ocean-basin, in free communi- 

 cation with both, being divided into two strata, of which the 

 lower constantly, though slowly, flows over the ocean-bed 

 from the pole toward the equator, while the upper is as con- 

 stantly flowing from the equator toward either pole. 



Second. That the cause of this circulation is the action of 

 surface-cold upon the water of the polar area, which, by re- 

 ducing its bulk, increases its specific gravity down to its 

 freezing-point at about 27, so that a column of polar water 

 weighs heavier than a column of equatorial water of the same 

 height. This involves a bottom outflow of cold water from 

 the polar area, producing a general downward movement and 

 a surface indraught. The water thus drawn in will be cool- 

 ed, and will descend in its turn. On the other hand, in the 

 equatorial area, the drawing off of the warm surface water and 

 the constant arrival of polar bottom water will produce gen- 

 eral upward movement, which, by bringing the glacial water 

 under the influence of solar heat, will keep up a difference in 

 weight between the polar and equatorial columns on which 

 the maintenance of this circulation depends. 



This general fact has been repeatedly illustrated by Dr. 

 Carpenter by actual experiment, on a small scale. 



Third. The amelioration of the climate of Northwestern 

 Europe, proved beyond all doubt to be dependent on a north- 

 east movement of ocean water, does not depend on the ex- 

 tension of the real Gulf Stream or Florida current to the 

 North Atlantic, but is the result of the northward movement 

 of the whole upper stratum, in consequence of the surface in- 

 draught toward the polar sea. This is shown from the fact 

 of the great depth of its current, which, as far as the Faroe 

 Islands, amounts to 600 or 700 fathoms a body of water too 

 great to be affected by so small a rivulet, in comparison, as 

 is the Gulf Stream. 



