Curiosities of Science. 69 



mical Society's Medal in 1857. " For thirty years," said the President 

 at the presentation, "never has the sun exhibited his disc above the 

 horizon of Dessau without being confronted by Schwabe's imperturbable 

 telescope ; and that appears to have happened on an average about 

 300 days a-year. So, supposing that he had observed but once a-day, 

 he has made 9000 observations, in the course of which he discovered 

 about 4700 groups. This is, I believe, an instance of devoted persist- 

 'ence unsurpassed in the annals of astronomy. The energy of one 

 man has revealed a phenomenon that had eluded the suspicion of astro- 

 nomers for 200 years." 



HAS THE MOON AN ATMOSPHERE ? 



The Moon possesses neither Sea nor Atmosphere of appreci- 

 able extent. Still, as a negative, in such case, is relative only 

 to the capabilities of the instruments employed, the search for 

 the indications of a lunar atmosphere has been renewed with 

 fresh augmentation of telescopic power. Of such indications, 

 the most delicate, perhaps, are those afforded by the occulta- 

 tion of a planet by the moon. The occultation of Jupiter, 

 which took place on January 2, 1857, was observed with this 

 reference, and is said to have exhibited no hesitation, or change 

 of form or brightness, such as would be produced by the refrac- 

 tion or absorption of an atmosphere. As respects the sea, if 

 water existed on the moon's surface, the sun's light reflected 

 from it should be completely polarised at a certain elongation 

 of the moon from the sun ; and no traces of such light have 

 been observed. 



MM. Baer and Maedler conclude that the moon is not en- 

 tirely without an atmosphere, but, owing to the smallness of 

 her mass, she is incapacitated from holding an extensive cover- 

 ing of gas; and they add, "it is possible that this weak en- 

 velope may sometimes, through local causes, in some measure 

 dim or condense itself." But if any atmosphere exists on our 

 satellite, it must be, as Laplace says, more attenuated than 

 what is termed a vacuum in an air-pump. 



Mr. Hopkins thinks that if there be any lunar atmosphere, 

 it must be very rare in comparison with the terrestrial atmo- 

 sphere, and inappreciable to the kind of observation by which 

 it has been tested ; yet the absence of any refraction of the 

 light of the stars during occultation is a very refined test. Mr. 

 Nasmyth observes that " the sudden disappearance of the stars 

 behind the moon, without any change or diminution of her 

 brilliancy, is one of the most beautiful phenomena that can be 

 witnessed." 



Sir John Herschel observes : The fact of the moon turning 

 always the same face towards the earth is, in all probability, 

 the result of an elongation of its figure in the direction of a 

 line joining the centres of both the bodies, acting conjointly 



