METHOD 



OF 



COMPUTING ASTRONOMICAL REFRACTIONS 



FOR 



OBJECTS NEAR THE HORIZON. 

 By the Rev. JOHN BRINKLEY, D. D. F. R. S. M. R. I. A. 



AND PROFESSOR OP ASTRONOMY IN THE UNIVERSITY OF DUBLIN. 



Read, January 17, 1820. 



Although observations of zenith distances, when the object is 

 near the horizon, are frequently aiFected by irregularities of refraction, 

 that seem not capable of being reduced to any law^, yet there is rea- 

 son to suppose that the effect of these irregularities will disappear in 

 a mean of a great number of observations ; and thus a mean refraction 

 for any altitude may be obtained, depending only on the mean zenith 

 distance,, and the corresponding heights of the barometer and ther- 

 mometer. The investigation of the law of these regular refractions, 

 as they may be called, has much engaged the attention of astro- 

 nomers. 



