176 ATMOSPHERIC ABSORPTION. [SECT. xviu. 



being distinctly reflected. I had not been long contem- 

 plating this phenomenon, before a sudden storm came on 

 and dropped a curtain of clouds over the scene." 



An occurrence which happened on the 18th of November, 

 1804, was probably produced by reflection. Dr. Buchan, 

 while watching the rising sun from the cliff about a mile to 

 the east of Brighton, at the instant the solar disc emerged 

 from the surface of the ocean, saw the cliff on which he was 

 standing, a windmill, his own figure and that of a friend, 

 depicted immediately opposite to him on the sea. This 

 appearance lasted about ten minutes, till the sun had risen 

 nearly his own diameter above the surface of the waves. 

 The whole then seemed to be elevated into the air, and 

 successively vanished. The rays of the sun fell upon the 

 cliff at an incidence of 73 from the perpendicular, and the 

 sea was covered with a dense fo^g many yards in height, 

 which gradually receded before the rising sun. When 

 extraordinary refraction takes place laterally, the strata of 

 variable density are perpendicular to the horizon, and, if 

 combined with vertical refraction, the objects are magnified 

 as when seen through a telescope. From this cause, on 

 the 26th of July, 1798, the cliffs of France, fifty miles off, 

 were seen as distinctly from Hastings as if they had been 

 'close at hand; and even Dieppe was said to have been 

 visible in the afternoon. 



The stratum of air in the horizon is so much thicker 

 and more dense than the stratum in the vertical, that the 

 sun's light is diminished 1300 times in passing through it, 

 which enables us to look at him when setting without being 

 dazzled. The loss of light, and consequently of heat, by 

 the absorbing power of the atmosphere, increases with the 

 obliquity of incidence. Of ten thousand rays falling on its 

 surface, 8123 arrive at a given point of the earth if they 

 fall perpendicularly ; 7024 arrive, if the angle of direction 

 be fifty degrees; 2831, if it be seven degrees : and only 

 five rays will arrive through a horizontal stratum. Since so 



