atmospherology; — refraction. 389 



first direct and undivided ; but, in a short time, it 

 separated in several places, and each distinct portion 

 was inclined at a small angle towards the ti-ue ho- 

 rizon. The effect of refraction was six minutes of 

 altitude, A particular haziness was evident to the 

 east and north of the broken horizon. 



On the 28th of April 1811, I had an opportuni- 

 ty of ascertaining the exact effect of a singular re- 

 fraction, by the alteration produced in tlic distance af 

 the visible horizon. A ship, the Henrietta of Whit- 

 by, bearing easterly from us, lay beset at such a dis- 

 tance, that her hull was not visible ; and when view- 

 ed from an elevation of ninety feet, with a good te- 

 lescope, half her lower m.asts were intercej)ted by the 

 ice on the horizon. Now, at the elevation from 

 which this ship was seen, the horizon, under common 

 circumstances, would be nine miles distant ; and 

 from the knowledge of the dimensions of her masts, 

 I estimated the portion of the hidl and masts inter- 

 cepted by the horizon, at about 22 feet ; consequent- 

 ly, her distance beyond the horizon must have been 

 at least 4J miles, and her distance from us not less 

 than 13i 



The day had been almost cloudless, the sun 

 powerful. At 11 p. m.*, I was informed by the 



" Latitude 77° 4'; longitude 8° 50* 52" E. ; barometer 30.17 ; 

 thermometer at noon 26", at 1 1 P. M. 1 6° ; the wind had been 

 easterly, but now blew a brisk breeze from the north. 



