ATMOSPHEROLOGY. — FROST-RIME. 435 



the cold is reduced to 14°. It is most abundant in 

 the lowest temperatures, with a high sea and strong 

 winds ; but diminishes as the swell and wind subside, 

 or whenever the sea begins to freeze. When the 

 air is clear and apparently dry, it commences at a 

 higher temperature than when it is dark and damp. 

 Indeed, this meteor is most common when the air is 

 free from clouds. Hence, though it sometimes oc- 

 casions such an obscurity in the lower atmosphere, 

 that objects near the surface of the water cannot be 

 seen at the distance of 1 00 yards ; yet, at the mast- 

 head, where the observer is lifted above the mist, 

 ships can be distinguished at the distance of five or 

 six miles, and high land at the distance of ten or 

 fifteen leagues ; and when the frost-rime does not 

 rise above forty or fifty feet, objects on the water, 

 such as ice, may be discovered three or four miles off, 

 though they may be invisible from the deck when 

 within a furlong. 



The cause of this phenomenon may, perhaps, be 

 similar to that producing rain, as it can be very well 

 explained on Dr Hutton's theory, already described. 

 The wind that brushes over the surface of the water, 

 and is, by the pressure of the atmosphere, brought 

 into immediate contact, being much colder than the 

 sea, must receive heat from it, and have its tempe- 

 rature somewhat elevated. This increase of tempe- 

 rature, enables it to abstract some moisture from 

 the sea, and being thus rendered specifically lighter, 



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