4 Mr. Ivory's Tables of mean, fyc. QNo. 157* 



Log. diff. 308. -r- 94 or Tab. diff. for 1." =, + 03.28 

 T. (T.— 50°) Table iv,=, -.08 X, + 8.1=,— 00,65 

 b. (30 in. p.) „ — .14 x, + .37=, —00,05 



Mean refraction by the tables, . . 7' : 32."79 



Ditto ditto by P. Bessel's Tables, ap- \ *, „, , lm 

 pendix, Gr. Tr. 1836, .. .. f' ' 



Refraction by Ivory's Tables, .. .. -f 1".08 



When the altitude of the body is observed it is advisable to convert 



it into Zenith distance by subtraction from 90°, the proportional parts 



of the Logs, being then additive. 



Example III. The altitude of the sun's lower limb was observed 



45°: 15': 42"5, the Barometer standing at 23.33, and the Thermometer 



at 47-2 Fahrt. required the refraction. 



(90° — 45°: 15/ 42". 5) = 44°: 44': 17".5. = Z. 



Log. P. 23.33 Table 1. 9.89079 



Log. T. 47°.2 Table 11 0.00266 



Log. Z. 44°: 30' Table in 1.75855 



Prop, part for 14'.292 do. 357 



Nearest Tabular number, .. ,. 0': 44."80 1.65557 



Log. diff. 43 -f- 96 or Tab. diff, for 1"= -f 0.45 



Mean refraction, 0' : 45."25 



The following errata in the Original Table (Phil. Trans, for 1838) 

 have been corrected. 



Mean Refraction forZ.D. 89°:50' printed 32': 15'M0 should be 32':25".1 



Log.diff.Z.D.89°:00'and89°:10' .. .. 2316 .. .. 2306 



86°:40'and86°:50' .. .. 1627 •• - 1527 



85°: 40' and 85°: 50' .. .. 1312 .. .. 1308 



83°:00'and83°:10' .... 833 .. .. 933 



H.E.I.C. Magnetic Observatory, Simla, December, 1842. 



