94 LEAVED FROM THE BOOK OF NATURE. 



the temperature is cooler, water becomes thinner again 

 and lighter, so that at the freezing point, as ice, it weighs 

 considerably less than when fluid. The consequence of 

 this peculiar relation of water to heat produces the re- 

 markable result, that in the great ocean an incessant move- 

 ment continues : up to the above mentioned degree of heat, 

 the warmer and lighter water rises continually, whilst the 

 cooler and heavier sinks in like manner; below that point 

 the colder water rises and the warmer part descends to 

 the bottom. Hence, the many currents in the vast mass 

 of the ocean ; sometimes icy cold, at other times warm, 

 and even hot, so that often the difference between the 

 temperature of the current and that of the quiet water 

 by its side, is truly astonishing. The great Humboldt 

 found at Truxillo the undisturbed waters as warm as 

 twenty-two degrees, whilst the stream on the Peruvian 

 coast had but little more than eight degrees, and the sailor 

 who paddles his boat with tolerable accuracy on the outer 

 line of the gulf-stream, may dip his left into cold and 

 his right into warm water. 



Greater wonders still are hidden under the calm, still 

 surface of the slumbering giant. Thoughtless and careless, 

 man passes in his light fragile boat, over the boundless 

 expanse of the ocean, and little does he know, as yet, 

 of the vast plains beneath him, the luxuriant forests, the 

 sweet, green meadows, that lie stretched out at the foot 

 of unmeasured mountains, which raise their lofty peaks 

 up to his ship's bottom, and of the fiery volcanoes that 

 earthquakes have thrown up below the waves. 



For the sea, also, has its hills and its dales ; its table- 



