398 Prof. h'\schofl:' on the J^emperature of Springs. 



'But' whether this phenomenon is so extensive as to cause, by 

 the melting of such masses of ice, not only a local but a general 

 cooling of the sea in low latitudes, is difficult to determine. 

 'Tis true navigators have met with masses of ice of several nau- 

 tical miles in circumference; indeed, one has been seen eight 

 miles in width, and the whole length of which could not be com- 

 ?passed by the eye, and another of such dimensions that a ship 

 required three days to get clear of it, whilst at the same time it 

 rose to a height of 100, 200, and 250 feet above the sea, and 

 ■must, therefore, have extended to the depth of 450, 900, and 

 1100 feet below the surface. But, although considerable, what 

 are these masses of ice compared with the enormous quantities 

 of water of the ocean in the temperate and torrid zones ? Yet, 

 since several natural philosophers have sought the cause of the 

 cold damp summer of 1816, and a part of 1817, which was so 

 prejudicial and destructive to a great part of Europe, in the 

 melting of those enormous masses of ice,* and since, in Great 

 Britain, the thermometer was observed to fall whenever the 

 wind blew from the west, it may well be supposed that those 

 masses of ice do actually exert some influence on the depression 

 of temperature in the sea in low latitudes. 



As, notwithstanding these causes of a depression of the tem- 

 perature of the tropical seas, their temperature is still higher 

 than the mean temperature of the air, with which they are in 

 contact ; and, as farther, the water of the sea loses some of its 

 heat by evaporation — other causes must cause an elevation of 

 their temperature, which overbalance all these. The water of 

 the sea does indeed receive more heat from the rays of the sun 

 than the air ; but it also, on the other hand, loses heat in the 

 night by radiation. It is true we are not able to measure the 

 relative powers of the warming and cooling influences which 

 operate on the surface of the sea ; but it is hardly to be suppos- 

 ed that the former could be the most powerful, unless the sea 

 received heat from the earth at its bottom. 



To be continued in next Number. 

 • Chladni, in Gilbert's Annal. vol. Ixii. p. 132. 



