VILE 
On the Light of the Moon and of the Planet Jupiter. 
Bx GEORGE P. BOND. 
( Communicated September 11, 1860.) 
On the 22d of March, 1851, several daguerrotype pictures of Jupiter were 
obtained on plates exposed at the focus of the great refractor of the Observatory of 
Harvard College. The belts were faintly indicated; but the most interesting fact in 
connection with the experiment, apart from its having been, as is believed, the first 
instance of a photographic impression obtained from a planet, was the shortness of the 
time of exposure, which was nearly the same as for the Moon, whereas, considering 
the relative distance of the two bodies from the Sun, it was to have been expected that 
the light of the Moon would have had twenty-seven times more intensity than that of 
Jupiter, supposing equal capacities for reflection. The experiments were repeated on 
the 8th and 9th of October, 1857, by Mr. Whipple, using the collodion process, with a 
like result. 
The energetic action of the light of Jupiter was noticed by De La Rue, in Decem- 
ber, 1857. The following is an account of his experiments. 
* Recent experience in photographing the Moon and Jupiter having given me the 
impression that the light of that planet, in proportion to its luminosity, possessed con- 
siderably more actinic power than that of the Moon, I determined on testing the 
correctness of this view, experimentally, on the first favorable opportunity. On 
‘December 7th, the Moon and Jupiter being, during a part of the night, at nearly the 
same altitude, although in different parts of the heavens, I turned the telescope alter- 
nately on one and the other body, and thus obtained several photographs (six of each), 
under almost identical conditions. Generally nine to ten seconds were sufficient for 
the Moon pictures, and twelve seconds for those of Jupiter; hence, although the light 
of.the Moon is at least twice as bright as that of Jupiter, its actinic power would 
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