364 Astronomical and Nautical Collections. 



to explain the irregularities of terrestrial refraction, as well as 

 the uncommon increase of horizontal refraction in very cold 

 countries : and we may even derive from all these considera- 

 tions a correction of at least half a second, or perhaps of a 

 whole second, for the sun's altitude at the winter solstice, tend- 

 ing to remove the discordance, which has so often been found^ 

 in the results of some of the most accurate observations of the 

 obliquity of the ecliptic. 



ii. Extracts from two Papers on Refraction, hxj the Rev. John 

 Brinkley, D. D., published in the Transactions of the 

 Royal Irish Academy. 



I. Read May, 1814. 



12. As it is of considerable importance, particularly with a 

 view of comparing observations made in different places, that 

 the same refractions should be generally used, no objection, I 

 apprehend, can be made to the general adoption as far as 

 about 80° of the French refractions, which are now so well 

 known. 



13. Perhaps the following tables, " deduced from the above 

 formula," may be considered rather more convenient in many 

 instances than the French tables ; they will certainly furnish a 

 useful check. The advantage they afford is derived from the 

 facility with which the computation can be made by help of 

 tables of logarithms and of logarithmic tangents to four or five 

 places of figures, such as are in the " Tables requisite to be 

 used with the Nautical Ephemeris." By these the logarithmic 

 tangent of the zenith distance can be taken out at once, and 

 the inconvenience of proportioning for the minutes of zenith 

 distance avoided, which is greater than the new inconvenience 

 occasioned by the second table. Hence the tables here given 

 may be considered more convenient for observations of the 

 sun, moon, and planets. 



