300 Astronomical Society. 



to stars of a certain magnitude or colour ; nor are they dependent 

 upon any particular age of the moon. Most of them have furnished 

 but solitary instances of peculiarity y viz. Spica Virginis, y Librce, 

 132 Tauri, a 1 Cancri, X Aquarii, 249 Aquarii, 187 Sagittarii, y Tauri, 

 p Leonis, p Geminorum, 8 Cancri, and 8 Piscium. One, Regulus, af- 

 fords three, whilst to Aldebaran we are indebted for no less than 

 twenty instances of anomaly. 



On reference to the list, the anomaly alluded to, it will be seen, 

 stands not upon the testimony of a single individual, but is supported 

 frequently by the evidence of a second, and sometimes even of a third 

 person j occasionally they are co-observers at the same station ; at 

 other times they are at different parts of the same city ; whilst in some 

 instances, they are separated by a very considerable distance. On 

 the other hand, the conflicting testimonies, where we should least ex- 

 pect to find them, are perplexing 5 a circumstance which together 

 with the vague manner in which the observations are frequently re- 

 corded, and the habit, which in many instances unfortunately pre- 

 vailed, namely, of observing the immersion and emersion of the same 

 star, on the same occasion, with different telescopes, and the almost 

 constant omission to register, if the moon's dark limb, was or was not 

 visible, enable us, Mr. South says, to do little more than to state, 

 with some appearance of probability, what are not the causes of the 

 phenomena. 



The hypotheses advanced as explanatory of the phenomena in ques- 

 tion, are then stated : viz. A lively imagination on the part of the ob- 

 server :— A spurious disc given to the moon's image by the instrument 

 of observation : — A lunar atmosphere : — Irradiation : — And lastly, 

 different refrangibilities to which the rays from the moon and star 

 are liable, arising from their differences of colour. 



As unfavourable to the first hypothesis, which would refer the 

 phenomenon to a lively imagination on the part of the observer, 

 Mr. South advances the fact, that ' more than sixty instances of ano- 

 maly stand attested by such men as Messier, Troughton, Bouvard, 

 Arago and Mathieu ; and that it is rather too much to suppose, that 

 all of them are liable to the imputation, which such an hypothesis 

 would require. 



The second hypothesis, which supposes a spurious disk to be given 

 to the moon's image, might, he observes, be entitled to some consi- 

 deration, had refracting telescopes whose object-glasses were not 

 achromatic, been solely employed for the observations ; but seeing 

 that refractors, long and short, achromatic and non-achromatic j re- 

 flectors, newtonian and gregorian, most of which were probably far 

 above the rank of good instruments, and some of which certainly 

 might be brought forward as the most perfect specimens of optical 

 ingenuity, — have all exhibited the anomaly ; there is considerable dif- 

 ficulty in receiving the hypothesis j unless indeed we could grant that 

 a constant cause should not produce a constant effect. 



The next hypothesis offers a lunar atmosphere as the occasion of 

 the apparent projection of a star on the moon's disk. Were this the 

 case, its effects would be similar upon all stars of similar colour ; and 



should 



