Indications of a Lunar Atmosphere. 51 



planets enfeebling their light.* But, as we perceive nothing of 

 this sort upon a luminary which is a thousand times nearer us» 

 the cause which produces it may be considered as absolutely 

 wanting in the moon. 



5. Conceniijig some observations which appear to indicate the 

 existence of a Lunar Atmosphere. — We have already seen that 

 it may be regarded as demonstrated, that the moon has no at- 

 mosphere which, in any respect, is comparable to that of the 

 earth. It does not, however, necessarily follow, that it is com- 

 pletely devoid of one ; and some appearances have been wit 

 nessed which may be referable to a cause of this kind. Such, 

 for example, are the changes in brightness, as well as in colour 

 and form, which have been observed in some stars a short time 

 before their occultation behind the moon. Some astronomers, 

 it is true, have never recognised such appearances. But others, 

 we must admit, equally worthy of confidence, have verified 

 them. Messrs Beer and Madler mention, among others, that 

 two observations have been communicated to them by M. Bo- 

 guslawski of Breslau, in which two small stars assumed, for 

 a minute or two before their occultation, a form which was 

 elongated in a direction perpendicular to the margin of the 

 moon, and again, just before they were hid, appeared as lumi- 

 nous points. Our authors themselves, on the 25th of April 

 1836, observed u of the lion, an instant before its occultation 

 behind the moon, become somewhat redder, and slightly di- 

 minish in lustre. They thought also that they perceived, on 

 many occasions, when an annular mountain began to be illu- 

 minated, and when it was still darkness all around it, that 

 slight changes of colour were manifest, consisting in a bluish 

 light, which rapidly transformed itself first into a pale yellow, 

 and then into a more decided yellow. 



If an atmosphere exists round the moon, corresponding to what 



• The most considerable of the two spots which we observed upon the disk 

 of Jupiter, from November 1834 to April 1835, continued visible no longer, 

 after passing the central point, than during one hour und twenty-four mi- 

 nutes and one hour and twenty-seven minutes, on two opportunities which 

 were peculiarly favourable ; in all other instances it disappeared sooner. It 

 has not been seen, therefore, farther than at 54° of the point of conjunction ; so 

 that all that is required to render it invisible is an obscuring thickness double 

 of that which exists on the middle of the disk (Note by the Authors.} 



d2 



