POLAR ICE-CAPS AND SEA LEVELS. 359 



33 feet of sea. A column of sea- water 33 feet 

 long (or 10 metres, or 5^ fathoms) and square inch 

 area, weighs 15 Ibs. The atmosphere, mass for 

 mass, is just equivalent to 5j fathoms of sea, but 

 33 feet depth is a mere fraction of our sea-water. 

 And again, a quantity of water is of much greater 

 capacity for heat than the same quantity of air, the 

 thermal capacity of air being very much less than 

 that of water. Briefly then we may say that in 

 the transport of heat over the whole solid globe 

 the air goes for nothing. The sea is the great 

 carrier. The air, of course, has an enormous 

 indirect effect in the shape of gales, moderate 

 winds, or trade winds, and in moving the water. 

 It moves the surface of the water just as it moves 

 the ships over the water. So that wind, indirectly 

 helps the sea as a heat carrier. The wind is the 

 distributer, the sea is the carrier the great 

 carrier in the transport of heat 



