448 Mr. Carringtoii on the Evidence of the 



As the parallel ou which this spot was situated passed nearly 

 through the centre of the disc, and its latitude was small, the 

 differences of hcliographical longitude of the spot and the centre 

 of the sun^s disc were on each day nearly equal to p, and were 

 amenahle to sensibly the same corrections for solar refraction. 

 The hcliographical longitudes will accordingly receive the same 

 corrections, and the times t the equivalents in time with opposite 

 signs. Taking ^ = Aug. 22-365 as the concluded mean, the next 

 Table exhibits first the uncorrected discordances of t; and next, 

 these discordances corrected on three suppositions indicated. 



The first hypothesis leaves the resulting sum of discordances 

 much as it wiis before correction, but the second and third sen- 

 sibly increase it, in other words, do harm instead of good. The 

 sums on the three hypotheses, however, indicate that a smaller 

 value of m would probably give a better result. Treating the 

 discordances by equations of condition and the method of least 

 squares, we find ?h = 1-002003 as the most probable value, tlie 

 sum of the discordances being in that case reduced to +176. 

 The observations accordingly afford very slender evidence in 

 Javour of an atmosphere for which h — -^, ??i= 1-0020, but will 

 not bear one for which m much exceeds 1*005. 



We will now take a different case, in which no assumption of 

 elements of the plane of rotation need be made. If two spots 

 are passhig over the disc together, and solar refraction be in- 

 sensible, the distance between their centres in arc of a great 

 circle should be constant from day to day, or affected only by 

 the independent motion of the spots. On the other hand, if 

 the observed angles are affected by refraction, the mutual di- 

 stance will a])pcar to vary. The independent motions of spots 

 being notoriously less in latitude than in longitude, whether 

 arising from change of form or translation, it appears at first 



